INTEGRATION OF CONSTRUCTION WORKER FALL SAFETY IN … · integration of construction worker fall...
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1 INTEGRATION OF CONSTRUCTION WORKER FALL SAFETY IN DESIGN THROUGH THE USE OF BUILDING INFORMATION MODELING By JIA QI A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2011
Transcript of INTEGRATION OF CONSTRUCTION WORKER FALL SAFETY IN … · integration of construction worker fall...
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INTEGRATION OF CONSTRUCTION WORKER FALL SAFETY IN DESIGN THROUGH THE USE OF BUILDING INFORMATION MODELING
By
JIA QI
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
2011
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© 2011 Jia Qi
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To my parents, Yinghong Song and Fengzhou Qi
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ACKNOWLEDGMENTS
The first group of people I would like to acknowledge is my committee members. I am
grateful to my advisor, Jimmie Hinze, for his tireless support and selfless mentoring. He
provided me with a role model as a researcher. I would like to thank Dr. Raymond Issa for his
encouragement and generosity. Dr. Issa helped me throughout my endeavor and offered me the
possibility to discuss my research study with members of his vast network of industry and
academic contacts. I am extremely grateful to Dr. Olbina for all of her hard work and dedication
to her students and the teaching profession. I would also like to thank Dr. Chow. I greatly
appreciate all of his help and support in completing this study.
I am indebted to BIMserver, AEC3, and Solibri for their generosity in authorizing me to
use their software that has been invaluable to my research study.
I am also very appreciative of all those who helped me in the course of my research: Dr.
William East, Léon van Berno, Nichlas Nisbet, Ruben de Laat, Wei Wu, Yogesh Veeraraghavan,
Le Zhang, Zhe Wang, Rui Liu and many, many more.
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TABLE OF CONTENTS page
ACKNOWLEDGMENTS ...............................................................................................................4
LIST OF TABLES ...........................................................................................................................8
LIST OF FIGURES .........................................................................................................................9
LIST OF ABBREVIATIONS ........................................................................................................12
ABSTRACT ...................................................................................................................................14
CHAPTER
1 INTRODUCTION ..................................................................................................................16
Project History ........................................................................................................................17 Research Questions and Research Objectives ........................................................................18
2 LITERATURE REVIEW .......................................................................................................20
Design for Construction Worker Safety .................................................................................20 The Concept of Design for Construction Safety .............................................................20 Implementing the Design for Safety Concept .................................................................23 Barriers to Implementation ..............................................................................................24 The Legal Framework of Construction Health and Safety ..............................................27 Design for Safety Resources, Tools, and Processes ........................................................32
Building Information Modeling ..............................................................................................39 Adoption of Advanced Information Technologies in Construction Industry ..................39 Concepts of Building Information Modeling ..................................................................41
Definition of Building Information Modeling .........................................................41 Characteristics of Building Information Modeling ..................................................42 Legal issues ..............................................................................................................43
Building Information Modeling Software .......................................................................44 IFC interface .............................................................................................................44 Classification of BIM software ................................................................................45 Code checking software ...........................................................................................47
Delivery Method Influence on Safety Performance ........................................................48 Integrated Project Delivery method .........................................................................51 Integrated Project Delivery with Building Information Modeling ...........................54
Computer-Aided Critiquing System .......................................................................................54 Computer-Aided Critiquing System in Design and Construction ...................................54 Summary of Related Work ..............................................................................................55
3 METHODOLOGY .................................................................................................................63
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Finding the influence of BIM technology on Construction Safety.........................................64 Design for Construction Safety Process .................................................................................65 Defining the Rule Source ........................................................................................................66
Existing Design for Construction Worker Safety Suggestions .......................................67 New Design for Construction Worker Safety Suggestions .............................................68 Classification of Design Suggestions ..............................................................................69
Architecture and Functionality of the desired System ............................................................72 Platform Chosen .....................................................................................................................77
Data Saved in a Relational Database ...............................................................................80 Data in IFC/Ifcxml Schema .............................................................................................82 Data in Other XML Schema ............................................................................................85
Structuring the Rule Source ....................................................................................................87 Creation of Rule Sets ..............................................................................................................89
Rule Sets Based on Relational Database .........................................................................89 Rule Sets Based on BIMserver ........................................................................................91
Direct approach ........................................................................................................92 Indirect approach ......................................................................................................94
Rule Sets Based on Solibri Model Checker ....................................................................98 Rule Sets Based on Bimservices ...................................................................................101
4 RESULTS .............................................................................................................................108
BIM technology’s impact on construction safety .................................................................108 Safety Planning ..............................................................................................................108 3D/Virtual Reality .........................................................................................................109 Schedule/4D ..................................................................................................................110 Conducting Clash Detection ..........................................................................................112 Increasing Prefabrication ...............................................................................................113
Design for Construction Worker Safety Software Tool .......................................................115 Checking Results with a Relational Database ...............................................................118 Checking Results with BIMserver .................................................................................121 Checking Results with Solibri Model Checker .............................................................125
5 CONCLUSIONS AND RECOMMENDATIONS ...............................................................135
Conclusions...........................................................................................................................135 Drawbacks ............................................................................................................................141 Recommendations for Future Research ................................................................................143
APPENDIX
A FALL PROTECTION BEST PRACTICS............................................................................146
B SAMPLE CODES: NET AREA VALUE OF IFCSLAB ....................................................149
C SAMPLE CODES: IFCOPENINGELEMENT AREA VALUE RETRIVEAL ..................152
D SAMPLE CODES: QUERYING RELATIONAL DATABASE WITH SQL .....................155
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LIST OF REFERENCES .............................................................................................................156
BIOGRAPHICAL SKETCH .......................................................................................................165
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LIST OF TABLES
Table page 2-1 Comparison of the hierarchy of safety requirements between U.S. and U.K. ...................28
2-2 Computer-aided critiquing systems ...................................................................................62
3-1 Four different mark-up colors ..........................................................................................103
5-1 Comparison computable rule compiling process based on three software platforms ......137
5-2 Comparison of functionalities between three software platforms ...................................138
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LIST OF FIGURES
Figure page 1-1 Number and rate of fatal occupational injuries by industry sector in 2009 .......................16
2-1 Time/safety influence curve ...............................................................................................21
2-2 The hierarchy of control measures with practical examples ..............................................23
2-3 Distribution of designer activity in addressing safety. .......................................................24
2-4 Hierarchy of the designing for safety resources. ...............................................................33
2-5 Design for construction worker safety process ..................................................................35
2-6 IFC Interfaces.....................................................................................................................45
2-7 BIM roadmap .....................................................................................................................46
2-8 Participant relationships in the design-bid-build method ..................................................49
2-9 Team’s ability to affect project variables...........................................................................50
2-10 Traditional and redefined project phases ...........................................................................52
2-11 Participant relationships in a project under the IPD method .............................................53
2-12 Block diagram of a system for checking a building information model against SMARTcodesTM ...............................................................................................................60
2-13 Predominant checking systems ..........................................................................................61
3-1 Classification of design for construction worker safety best practices ..............................71
3-2 Architecture of Design for Construction Safety tool .........................................................74
3-3 Functionality of the D4S software tool ..............................................................................77
3-4 Querying BIM model/database with different programming languages and derived platforms/servers ................................................................................................................80
3-5 Building features in a relational database ..........................................................................81
3-6 Worksheet created by the IFA ...........................................................................................82
3-7 Linking the IfcWindow to IfcWall in HelloWall example ................................................84
3-8 Information lost during data transfer process ....................................................................86
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3-9 Interoperability through ISO standards ..............................................................................88
3-10 Table listing window types ................................................................................................90
3-11 Table listing levels .............................................................................................................90
3-12 Sequencing floor levels based on ‘Level’ value in ‘Floors’ spreadsheet ...........................90
3-13 All windows above the first floor in ‘Windows’ Spreadsheet ...........................................91
3-14 Filtering windows by SillHeight ........................................................................................91
3-15 The returned result of non-compliance ..............................................................................91
3-16 IFC hierarchy for opening area value retrieval ..................................................................93
3-17 Dimension parameters of an IfcOpeningElement ..............................................................94
3-18 IFC 2×3 object diagram – IfcOpeningElement ..................................................................96
3-19 Parameters of rectangle profile definition ..........................................................................97
3-20 The Rule Set Manager interface for browsing and editing rules .......................................99
3-21 The Libraries View ..........................................................................................................100
3-22 Workspace View ..............................................................................................................100
3-23 Parameter View ................................................................................................................101
3-24 Encoding D4S suggestions into safety Constraint Model................................................102
3-25 Sample rule of bimServices .............................................................................................104
3-26 Reviewing IFC opening element properties in IfcStoreyView ........................................105
3-27 Three windows in building model 4351.ifc .....................................................................106
3-28 Opening elements in building model 4351.ifc .................................................................107
4-1 Photograph of BIM computer lab at Center for Advanced Construction Information Modeling at the University of Florida .............................................................................110
4-2 Construction project life cycle safety with a D4S application tool .................................115
4-3 Safety effort of different stakeholders in a project lifecycle ............................................118
4-4 Model checking in a Microsoft Access ............................................................................119
4-5 Import computable rule in the Query window .................................................................119
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4-6 Model checking result in a Microsoft Access ..................................................................120
4-7 The architecture of current model server and potential extension ...................................121
4-8 Launch BIMserver and select project to be checked .......................................................122
4-9 User interface of Advance Query function of BIMServer ...............................................122
4-10 Checking area values of opening elements with BIMserver by using computable rule written in direct approach ................................................................................................123
4-11 The relationship between net area value and opening element area value ......................124
4-12 Checking area values of opening elements with BIMserver by using computable rule written in direct approach ................................................................................................124
4-13 Checking layout of Solibri Model Checker .....................................................................125
4-14 Using the model tree navigates the subject building model ............................................126
4-15 Selecting desired constraint model / rule set....................................................................127
4-16 Checking results ...............................................................................................................128
4-17 Description of non-compliance in the Info View ............................................................128
4-18 The PSet_Revit properties in Info View ..........................................................................129
4-19 Result Details view ..........................................................................................................130
4-20 Neglecting the non-compliance after selecting the ‘Accepted’ Option ...........................130
4-21 Create report.....................................................................................................................131
4-22 Instance properties in BIM authoring tool .......................................................................132
4-23 New result of the check after changing the dimension of certain objects .......................133
4-24 Result of checking for slab openings ...............................................................................134
4-25 Designing alternative given in Info View ........................................................................134
5-1 IfcOpeningElement with an IfcArbitraryClosedProfileDef .............................................143
5-2 IfcArbitraryClosedProfileDef defined by six points ........................................................143
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LIST OF ABBREVIATIONS
3-D Three Dimensions
4-D Three Dimensions + Time
4-D-Safety Four Dimensional + Safety
BIM Building Information Modeling
BIM ASW BIM authoring software
CACIM Center for Advanced Construction Information Modeling
CDM Construction Design and Management
CII Construction Industry Institute
CSI Construction Specifications Institute
COBie Construction Operations Building Information Exchange
ERDC Engineer Research and Development Center
HSE Health and Safety Executive
IAI International Alliance for Interoperability
ICC International Code Council
IFC Industry Foundation Class
IPD Integrated Project Delivery
KBS Knowledge Based System
MCS Model Checking Software
NBIMS National BIM standard
NIOSH National Institute for Occupational Safety and Health
OPS Onuma Planning System
OSHA Occupational Safety and Health Administration
PPE Personal Protective Equipment
SQL Structured Query Language
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STEP Standard for the Exchange of Product model data
XML Extensible Markup Language
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Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy
INTEGRATION OF CONSTRUCTION WORKER FALL SAFETY IN DESIGN THROUGH
THE USE OF BUILDING INFORMATION MODELING
By
Jia Qi
December 2011
Chair: Jimmie Hinze Cochair: R. Raymond Issa Major: Design, Construction and Planning
The construction industry has incurred the most fatalities of any U.S. industry in the
private sector in recent years. While many factors may contribute to this statistic, one likely
cause is due to designers who often lack design for construction safety knowledge, which results
in many safety hazards being built into project models. To improve the current situation, this
research was undertaken to identify the possible influence of Building Information Modeling
technology on construction safety. After identifying the extent of the positive impact of BIM
technology on safety, the research entailed the development of a design for construction worker
safety tool which efficiently makes designing for safety suggestions available to designers and
constructors. Particular emphasis was placed on fall accidents since falls are the most frequently
occurring cause of fatalities on construction sites.
The Design-Build delivery method is helpful for implementing this tool. The traditional
Design-Bid-Build approach limits the abilities of contractors to contribute their knowledge to the
project during the design phase, when they could add significant value to the project. With this
designing for safety tool, it is possible for project participants to work together to optimize the
building models/drawings, which provide valuable downstream benefits. Meanwhile, using the
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checking results from this tool, the constructors have the opportunity to take preliminary safety
measures to address construction site hazards from the beginning of the project.
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CHAPTER 1 INTRODUCTION
It is an alarming statistic that every work day nearly four workers are killed in the U.S.
construction industry. In 2009, the construction industry fatalities represented 18.8% of all work-
related fatalities in the U.S. (Bureau of Labor Statistics 2009). The construction industry has
incurred the most fatalities of any industry in the private sector in the past five years. Figure 1-1
shows the number and rate of fatal occupational injuries by industry sector in 2009. The number
of fatalities sustained in the construction industry (816) far exceeds those of other industries. The
fatality rate of the construction industry (9.7 fatalities per 100,000 workers) is exceeded by only
three industries, namely mining; agriculture, forestry, fishing, and hunting; and transportation
Figure 1-1. Number and rate of fatal occupational injuries by industry sector in 2009 (Source: Bureau of Labor Statistics)
and warehousing. Because of the high injury and fatality rates and the high costs associated with
these accidents, improving job site safety has become a major concern for many construction
professionals (Gambatese 2008). Researchers have proposed many methods to reduce job site
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hazards. One technique is to incorporate safety considerations into the project during the design
phase, or to involve designers in considering construction worker safety during the design
process (Korman 2001). This approach is known as design for construction safety. While this
approach is also known as prevention through design, especially among some federal agencies,
the term “design for construction safety” will be used herein.
Project History
This research utilizes recently developed information technology to develop an enhanced
software tool to facilitate the design for construction worker safety. Using a software tool to help
designers implement the design for construction safety knowledge is not a new concept. In the
1990s, the Construction Industry Institute (CII) recognized the lack of designer involvement in
construction worker safety due to their minimal education and experience in addressing safety on
construction sites. The CII funded a research project to develop a software tool to assist
designers in recognizing project-specific hazards and in implementing design suggestions for
consideration in the project design (Gambatese 1997). The design for safety suggestions were
accumulated through research efforts that included input from designers, traditional construction
contractors, and design-build firms. These suggestions were incorporated into the “Design For
Construction Safety ToolBox” (Gambatese et al. 1997).
As new information technology emerged, CII expressed a need for a software tool which
would replace the software tool created in 1996. To give design professionals the ability to more
quickly and easily access design for construction safety suggestions, the “Design for
Construction Safety Toolbox,” second edition, was developed in 2007 by Marini and Hinze,
through the support of the CII. The second edition of the toolbox is a web-based application that
can also be operated via a compact disc. The database of this application consisted of a simple,
external, text-based (XML) file designed to easily accommodate the addition of future design for
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construction safety suggestions (Marini 2007). Besides the changes made to the database, other
elements such as the application design, application navigation and software tour functions of the
second edition include substantial improvements to make the application more deliverable and
easy-to-use. This application is available from the CII.
As Building Information Modeling (BIM) technology is being increasingly adopted by
more design and construction companies, a large amount of work in the architecture, engineering
and construction (AEC) domain is now completed by using three-dimensional/object-oriented
computer software. In current usage, BIM does not automatically address construction worker
safety. Instead, construction safety can currently be addressed by the inclusion of written
statements which is a cumbersome and inefficient procedure. The proposed research is to
examine the possibility of developing a design for construction safety tool which could
automatically address construction safety in electronic construction documents.
Research Questions and Research Objectives
Designers who lack design for construction safety knowledge have limited access to this
type of information because the necessary channels of information flow do not exist. To solve
this problem, researchers can use Building Information Modeling (BIM) technology to deliver
design for construction safety knowledge to designers.
This research specifically addresses the following issues:
(1) With advances in information technology, is it possible for a construction worker safety tool to automatically check construction drawings and to provide design for safety suggestions during the design process?
(2) Determine the approach or procedure that would be most suitable for automatically integrating design for construction safety suggestions into the design process without hampering designer creativity.
(3) “Computer-aided critiquing” technology has been used to conduct automated building code compliance assessments. This endeavor shows the possibility of using computers automatically to check three-dimensional (3-D) models for certain rule sets. Building code
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compliance and design for construction safety knowledge are developed for different purposes. The differences between checking systems that use encoded building code information as rule sets and checking systems that use the encoded design for construction safety knowledge as rule sets will be examined.
(4) The supposed users of previous design for construction worker safety toolboxes are designers, most notably designers in design-build firms. Constructors could also check drawings themselves before construction work is begun to develop plans to protect their employees.
The objectives of this research are as follows:
To understand how Building Information Modeling (BIM) as a tool could be used to
enhance construction worker safety, especially falls from elevation.
To study the current practices of designers and make recommendations that will enhance
construction work site safety and to review the current procedures of design for construction
worker safety to improve it by using BIM Technology.
To develop a design for construction worker safety tool that would automatically check
construction drawings and make design for safety knowledge available to designers during the
design phase.
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CHAPTER 2 LITERATURE REVIEW
This chapter describes the background of this research and summarizes the results of other
related research work. There are three sections in this chapter. The first section introduces the
concept of design for construction worker safety and the current level of implementation in the
construction industry. Barriers to implementing this approach are examined and the legal
implications are discussed in detail by comparing the implementation of designing for safety in
the U.K. and U.S. The impact of the UK regulatory effort is discussed. Various safety tools are
examined to summarize past research work in this domain. The second section introduces the
concept of Building Information Modeling/Virtual Design and Construction. A BIM map is used
to describe the relationship between different applications. In particular, it focuses on code
checking software which has many similarities to a potential automatic design for construction
safety toolbox. Finally, the third section defines the computer-aided critiquing system and
introduces some prototypes which have been developed both in academia and in industry.
Design for Construction Worker Safety
The Concept of Design for Construction Safety
In 1985, the International Labor Office (ILO) suggested that design professionals should
consider construction safety during the design process. Design for construction worker safety
was not researched in the U.S. until Hinze (1992) conducted a survey to explore the relationship
between safety and design. That study showed that construction worker safety can be addressed
during the design stage. Despite this, few design firms were identified that regarded the safety of
construction workers as being within their scope of responsibility, primarily because of
designers’ fears of increased liability (Hinze and Wiegand 1992). In 1993, the Construction
Industry Institute sponsored a research study for Hinze and Gambatese to develop a detailed
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understanding of the concept of designing for construction worker safety and to develop a design
tool or toolbox (Gambatese et al. 1997).
According to Szymberski’s (1997) time/safety influence curve, the ideal time for
construction safety to be a prime consideration in the life of a project is in the conceptual and
preliminary design phases. Figure 2-1 shows that by including construction safety as a
consideration earlier in the project’s life cycle, project participants have a greater ability to
positively influence construction worker safety. A significant ability to improve construction site
safety is lost when it is considered later in the life cycle, such as during the construction phase.
Figure 2-1. Time/safety influence curve (Adapted from: Szymberski 1997)
Hazard management theory also validates the value of design for construction safety. After
identifying hazards to health and safety and assessing their potential to do harm, measures to
eliminate or minimize them should be determined in accordance with the hierarchy of control
(Manuele 1997; Andres 2002; Civil Construction Industry OHS Committee 2003).The hierarchy
of control measures are as follows:
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• Eliminate the hazard • Substitute the hazard with a lesser risk • Isolate the hazard • Use engineering controls • Use administrative controls • Use personal protective equipment
Measures from the top of the hierarchy produce better results than the lower ones and
should be considered wherever possible. According to this, control measures which make the
workplace safe are more effective than measures which protect construction workers from a
hazardous condition. Consider a practical example of using hierarchy of control measures to
protect workers working at elevation. First, construction workers should avoid working at
elevation whenever they can. This could be achieved by designing out the need to work at
elevation. Second, workers should use such measures a guardrails for fall protection when they
cannot avoid working at elevation. Third, where workers cannot eliminate the fall risk, they
should use personal protective equipment (PPEs) to minimize the distance and consequences of a
fall if a fall accident would occur (Health and Safety Executive 2005). Figure 2-2 shows the
hierarchy of control measures for fall protection.
Studies of construction accidents and injuries confirm that many events have their origins
upstream from the building process (Suraji 2001).A study by the European Foundation found
that approximately 60% of construction accidents could have been avoided or reduced with more
thought at the design stage (European Foundation 1991). Researchers in the U.K. contended that
changes in the permanent design elements would have reduced the likelihood of 47% of the 100
construction accidents studied (Gibb et al. 2004). Behm (2004) found that design was linked to
accidents in approximately 22% of 226 construction injury incidents and 42% of 224 fatality
incidents in Oregon, Washington, and California between 1990 and 2003. Later, Gambatese et al.
(2007) used the Delphi method to validate Behm’s research findings.
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Figure 2-2. The hierarchy of control measures with practical examples (Adapted from: U.K.
HSE 2003)
Implementing the Design for Safety Concept
Even though the concept of design for construction safety is viewed as a viable
intervention to improve safety, design firms do not commonly address construction worker
safety in their designs (Gambatese et al. 2005a). From the results of a 1992 survey, Hinze found
that less than one-third of the design firms addressed construction worker safety in their designs,
and less than one-half of the independent constructability reviews conducted addressed
construction worker safety (Hinze and Wiegand 1992). Hinze conducted studies that surveyed
377 project owners in the U.S. (Hinze 1994a; Hinze 1994b). The owners were asked whether
designers of their projects addressed construction safety in their designs. Only 16% of the
owners in those studies indicated that they considered their employee safety in their designs
(Figure 2-3). In a recent survey, 37% of the 19 respondents expressed that they were interested
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and willing to implement the concept, while 47% of the respondents gave a neutral response and
16% said they were not interested in it.
Figure 2-3. Distribution of designer activity in addressing safety (Adapted from: Hinze 2006).
Research studies were conducted and relevant training was carried out to change this
climate in the construction industry. With these efforts, researchers found that changes are
slowly occurring in the construction industry. First, an increasing number of owners are
demanding that all parties involved in their projects should be actively involved in safety
management. Owners such as Intel, Inc. and the Southern Company tend to select designers who
are safety conscious. Second, some large design-builders such as Jacobs and Fluor are also
practicing design for safety in their projects. In the future, with the companies realizing the
benefits they gain by adopting the design for safety concept, it is expected that more firms will
implement designing for safety concepts.
Barriers to Implementation
While the evidence is clear that construction worker safety can be addressed during the
design stage, the widespread implementation in practice throughout the U.S. is currently lacking
May address safety in
future 16%
Worker safety is addressed 10%
Worker safety not considered 45%
Occasionally address safety for
specific items 29%
Distribution of designer activity in addressing safety
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(Hinze and Wiegand, 1992). There are several barriers that hinder the implementation
(Gambatese 2005; Toole 2005):
• Designers’ fear of liability. • Designers’ lack of safety expertise. • Conflicts with the project delivery method. • Additional costs incurred by designers. • Time constraints. • Lack of a regulatory mandate.
In the U.S., there are liability fears on the part of designers for becoming involved in
construction site safety. In the Gambatese et al. (2005) study in Oregon and Florida, 26% of the
survey participants mentioned increased liability as a barrier. The construction documents define
the design for competitive bidding, cost estimation, and conveying “design intent”, but the
designers have no authority over or responsibility for the means and methods of construction.
For instance, the American Institute of Architects (AIA) B-141 contract form seeks to limit the
responsibility of the designer for actual construction issues, placing that responsibility instead on
the contractor (AIA 2007). Legal counsels often advise designers to contractually and
operationally limit their involvement in safety to minimize potential exposure to third-party
lawsuits (Behm 2005).
Designers usually take their lack of familiarity with necessary methods as an excuse to
evade the task of implementing health and safety in the design process (Hinze and Wiegand
1992). The partition between the design trade and the construction trade has caused cooperation
problems in the construction industry for many years. Even though constructors and researchers
have accumulated considerable design for construction safety knowledge, the dissemination of
this information in the design community is difficult. Designers contend that no tools are
available to help them implement the design for construction worker safety concept. As a result,
various design for construction safety tools have been developed to solve these problems in
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recent years. Researchers suggest that 10-hour and 30-hour OSHA courses for design
professionals should be promoted.
The process of procuring construction services is another barrier to implementing the
design for safety concept. In the traditional methods of procuring construction via design-bid-
build, contractors are typically not chosen until after the design is completed. Since contractors
cannot be guaranteed the project award, even though they may have contributed their expertise
during the design process, the needed communication about hazards between designers and
builders usually does not occur. Meanwhile, the model contracts of the AIA and the Engineers
Joint Construction Documents Committee (EJCDC) clearly state that designers have no site
safety responsibilities. For example, the 2007 construction series of standard contract documents
of EJCDC state that a contractor is responsible for “initiating, maintaining and supervising all
safety programs in connection with the work” and “inform the owner and its engineer of specific
safety requirements that must be followed at the site and the corresponding obligation of owner
and engineer to comply with such requirements” (NSPE 2007).
Design for construction safety will increase both direct and overhead costs for design
firms. Considering safety during the design process requires more time to gain the needed
training and to complete the design work. Unless owners are willing to pay higher design fees,
designers will not be inclined to implement the design for safety concept to decrease total project
life cycle costs (Toole 2005).
Time constraints are another concern of designers. Usually the tight project schedules
established by owners discourage a thorough analysis of the safety issues in favor of satisfying
other design requirements. Insufficient time is dedicated to the implementation of safety
procedures during the design phase. For instance, when the design-for-safety process was
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developed on one large capital project, the design team did not always welcome additional
review steps and more opportunities for comments to which they had to respond, because the
pace of the design was compromised (Weinstein et al. 2005; Hecker et al. 2005).
Last, current U.S. regulations do not place the requirement on designers to design for
construction safety. This further impedes the process of the design for construction worker
safety, as it will be discussed in more detail in the next section.
The above barriers to the implementation of design for construction safety are not
insurmountable. Researchers have proposed some key changes needed for the implementation of
the concept (Gambatese et al. 2005b; Toole 2005). In these key changes, design for construction
worker safety tools could help designers acquire the necessary safety knowledge, as discussed in
detail in the following section.
The Legal Framework of Construction Health and Safety
By analyzing the evolvement of legislation related to jobsite safety in the U.S., it is evident
that safety standards and legislation are “a result of a long history of change in the drive to
reduce the number of worker injuries and fatalities” (Gambatese 1996). However, legislation in
the U.S. has lagged behind some other countries, while designing for construction safety has
become increasingly more common in Europe and Australia. In 1992, Directive 92/57/EEC, also
referred to as the Construction Site Directive, was published, which was an initiative to improve
occupational health and safety in the European construction industry (Bluff 2003). Great Britain
responded by enacting the Construction (Design and Management) Regulations in 1994.
Regulations of the U.S. and the U.K. have different impacts on the implementation of the
design for construction safety concept. Table 2-1 provides a comparison of the hierarchy of the
safety requirements of the U.S. and the U.K.
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Table 2-1. Comparison of the hierarchy of safety requirements between U.S. and U.K. Hierarchy of Safety Requirements U.K. U.S.
High Statutory Law European Union law: The Temporary or Mobile Construction Sites Directive 92/57/EEC UK statutory law: The Health and Safety at Work etc. Act 1974
Occupational Safety and Health Act of 1970
Medium Regulations Manual Handling Operations Regulations 1996 Construction (Design and Management) Regulations (CDM) 2007 The Management of Health and Safety at Work Regulations (MHSWR) 1999
Title 29, Part 1926 of the Code of Federal Regulations (29 CFR 1926)
Low Codes of practice Managing Health and Safety in Construction. CDM Regulations 2007. Approved Code of Practice
ASCE’s Policy Statement 350 (ASCE 2001) ASCE Code of Ethics (ASCE 1996)
In the U.K., the health and safety-related publications can be ranked into different levels
based on their importance (Thope 2005). They are the Health and Safety at Work etc. Act
(HSWA), statutory regulations, and codes of practice. The health and safety performance of the
U.K. industry is guided and informed by the Health and Safety Commission (HSC) and the
Health and Safety Executive (HSE) which were established in the mid 1970s by the Health and
Safety at Work etc. Act 1974 (Howarth and Watson 2009). The Health and Safety Executive is
also responsible for enforcing primary and secondary legislation. The primary legislation
includes a number of Acts such as the Health and Safety at Work etc. Act 1974. The secondary
legislation is made up of statutory instruments which are also referred as regulations.
The Health and Safety at Work etc. Act. 1974 (HSWA) is the primary piece of legislation
covering occupational health and safety (HSE 2009). One of its effects is to “secure the health,
safety and welfare of persons at work (HSE 1974).” The health and safety law of the U.K.
29
construction industry is built on this act. This act provides the basis for the U.K. health and
safety law and is further supported by sets of regulations (Howarth and Watson 2009).
The secondary regulations include regulations such as the Construction (Design and
Management), Workplace (Health, Safety and Welfare) Regulations, etc. The Construction
(Design and Management) regulations took effect in 1995 (HSE 2007), and place health and
safety management duties on all parties involved in a construction project. When it comes to the
duties of designers, it explains:
Every designer shall in preparing or modifying a design which may be used in construction work in Great Britain avoid foreseeable risks to the health and safety of any person—carrying out construction work; maintaining the permanent fixtures and fittings of a structure. (HSE 2007, p9)
Approved codes of practice accompany the regulations. The creation of approved codes of
practice is provided for by Section 16 of the Health and Safety at Work etc. Act (2007 HSE).
They are not legally binding documents but serve to provide practical guidance for compliance
with health and safety regulations and can be used in criminal court proceedings as a means to
interpret whether the practical requirements of health and safety regulations have been met
(Howarth and Watson 2009).
In the U.S., industrial accidents rose significantly after World War II. To ensure that
employers provide employees with an environment free from recognized hazards, the
Occupational Safety and Health Act (OSHAct) was enacted by Congress in 1970. The Act
applies to employers in many industries such as construction and manufacturing. In section 5 of
the OSHAct, the general duty clause clearly mandates:
Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees. (U.S. Dept. of Labor, 2009)
30
The OSHAct created the Occupational Safety and Health Administration (OSHA), an
agency of the Department of Labor. OSHA was given the authority to promulgate and enforce
workplace health and safety standards. Title 29, Part 1926 of the Code of Federal Regulations
(29 CFR 1926) is specifically for the construction industry. These standards apply to
construction and maintenance work in all states.
The federal OSHA standards focus on the safety management responsibilities of employers
for their employees (Toole 2002). OSHA standards suggest that ignoring the hazards would not
be a violation of the OSHA standards for an engineering firm since the engineer is neither a
contractor nor a specialty contractor who requires a laborer to work in an unsafe environment.
Furthermore, the federal OSHA standards rarely mention the possibility of the safety of workers
being considered during the design of the project (Toole 2007). The likelihood of new or revised
OSHA standards that specify the inclusion of architects and engineers might be low (Behm
2005). There is a controversial view as the OSHA regulation can be interpreted as applying
whenever there is an employee/employer relationship (e.g. an engineer or architecture firm
directs an employee to inspect work on a construction site). Some researchers suggest that the
federal OSHA construction standards should be reexamined to require proactive hazard analysis
to be initiated during the design stage, so contractors could do better to minimize probable
construction hazards and provide a safe place to work for construction workers (Toole 2007).
At the code of practice level, the site safety documents issued by major construction trade
organizations contain significant differences in the site safety roles expected to be assumed by
different project participants (Toole 2002). In general, the general contractor and specialty
contractors are assigned the primary responsibility for construction worker safety. This is
31
embodied through the policy statements or contract terms of the ASCE, AIA, AGC and ABC.
For instance, AIA A201 (2007) explicitly rejects the idea that the architect has a safety role:
If the Contractor is then instructed to proceed with the required means, methods, techniques, sequences or procedures without acceptance of changes proposed by the Contractor, the Owner shall be solely responsible for any loss or damage arising solely from those Owner-required means, methods, techniques, sequences or procedures. (AIA, 2007)
The Architect will not have control over, charge of, or responsibility for, the construction means, methods, techniques, sequences or procedures, or for the safety precautions and programs in connection with the work, since these are solely the Constructor’s rights and responsibilities under the Contract Documents, except as provided in Section 3.3.1. (AIA, 2007)
Fortunately, the designer’s role in construction site safety is changing (Toole 2005). This
can be detected from the alteration of the ASCE construction site safety policy. ASCE, in 1989,
enacted its Construction Site Safety policy statement which stated that site safety was essentially
the general contractor’s responsibility. The policy statement adopted in 1995 excluded the role of
the engineer. Also, the revised 1998 statement omitted any reference to the engineer. The change
emerged in the proposed new policy statement A-350 which states that construction site safety
involves all the parties to some degree. All efforts to improve safety at construction sites are
supported by ASCE and the most effective improvements can be achieved by a cooperative
approach between all parties involved on a project (Muller 2002). The policy stated that
engineers have the responsibility to:
Recognize that safety and constructability are important considerations when preparing construction plans and specifications…
Both the frameworks of the U.S. and U.K are comprehensive and cohesive. Compared to
the US legal system, the framework of the U.K. construction and safety regulations clearly
define the duties of the designers related to construction worker safety.
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Design for Safety Resources, Tools, and Processes
Several approaches and tools have been developed to help designers identify design
decisions that can significantly improve construction safety without compromising architectural
form or function (Gambatese et al. 1997; Toole 2005; Gambatese et al. 2005a). Unfortunately,
there is no existing classification of these approaches. To clarify the past development of the
design for construction safety techniques, a hierarchy will be presented of the design for safety
tools, processes, and methods (Figure 2-4).
The first effort is to improve the communication and coordination between the different
stakeholders. Collaboration between designers and construction superintendents could be
particularly effective to reduce construction worker injuries and fatalities.
The second method is to form a systematic design process to eliminate or reduce design
errors and increase the opportunity of incorporating the design for construction safety knowledge
into construction documents. If designers are not sufficiently experienced to continuously
consider safety, outside design reviews should be conducted to improve the quality of the
drawings. There are several stages in the design process where the design can be checked in
some way.
The third kind of endeavor is to conduct a thorough risk assessment of each design
component. This is usually done by using various tools such as safety manuals, checklists, and
software to help designers access design for construction worker safety knowledge. Furthermore,
some tools can facilitate the checking process to save time and design fees.
Project participants should first try to strengthen the collaboration between themselves.
There should be ways through which information can be accurately and swiftly shared by
different stakeholders. Secondly, designers could improve the design process by delivering
33
Figure 2-4. Hierarchy of the designing for safety resources.
“safe” construction documents for the constructors. Finally, various tools should be developed to
meet specific needs. Some of these tools will be described.
Though the improvement of safety performance is possible based on the effort of an
individual discipline, communication and cooperation among the project participants about the
safety aspects of the project are important and necessary. It is believed that the major opportunity
for improving the design and construction of facilities lies at the interface between disciplines
(Fischer and Kunz 2004). It is especially when the traditional design-bid-build delivery method
is used that a barrier to safety-in-design is most apparent. Active communication and
collaboration could overcome the separation between design and construction and facilitate
successful project completion. One proposed method to implement the design for safety is to
increase the communication and coordination of work between designers and construction
personnel, particularly those with excellent safety records. Experienced superintendents could
make substantial contributions to the designing for safety effort, provided that designers would
34
recognize and harness their skills, site experience, and knowledge (Coble and Haupt 2000). In a
practical project in which the design-for-safety process was developed and implemented, the lead
designer insisted that he saw increased collaboration and dialogue with top construction
managers and trade contractors as the greatest benefit of the whole design process (Weinstein et
al. 2005; Hecker et al. 2005).
Many endeavors have been made to make the design process better. Taylor (2007) claims
that one approach is to study the design process and regard this process as a failure prone system.
Thorpe (2005) suggests the best way is to turn safe construction practices into a standard part of
the regular design process. Other research efforts have found the design and review process can
influence the extent to which a design is successfully modified to impact safety. They think well-
planned and implemented design-for-safety review processes could facilitate creating effective
and efficient designs (Weinstein et al. 2005).
After realizing the importance of the design process, another important issue is when the
required site safety expertise should be provided. Ideally site safety expertise must be provided
throughout the design process. However, implementing the design in this way may inhibit the
designer’s creative process or hamper the usual design process. It is more practical to have safety
constructability knowledge provided through several progress reviews (Toole et al. 2006).
Experience gained while developing past design for construction safety tools also demonstrated
this problem. The Health and Safety Executive (HSE) of the U.K. developed a software
prototype to provide designers with easy access to health and safety information by establishing
a means of structuring HSE's information as a Knowledge Based System. After the Knowledge
Based System (KBS) was completed, HSE sought feedback on the application from users. The
general negative feedback of HSE’s Knowledge Based System was the designers’ concerns
35
about the timing to conduct the checks. Designers felt that they could pick up any health and
safety risks during a risk analysis after the main drawings had been completed. They preferred
this approach, even though checking work early in the design phase could save time (HSE 2003).
In Figure 2-5, Gambatese presented a design for construction safety process. The key
component of this process is the incorporation of site safety knowledge into design decisions
before the drawings are finally issued for construction (Design for Safety Workgroup 2008).
Design for safety is a continuous improvement process in which specific design options are
assessed in terms of their positive or negative impact on safety at the end of each sub-phase.
Figure 2-5. Design for construction worker safety process (Adapted from: Gambatese 1996)
Hinze (2000) proposed a holistic approach to design that encompasses the designers’
consideration of the entire life cycle of the facility. This approach can be implemented by
including safety considerations in constructability reviews (Gambatese 2000a). A thorough risk
assessment of each component of the design should be conducted by designers (Hinze et al.
36
1999). Such a safety review process has been implemented. In the U.S., Intel, Inc. developed a
design for safety process which is called “life cycle safety” (LCS). The process involved many
different parties throughout the course of programming, design, and construction. Consideration
of design changes early in the project and input from the trade contractors are the key factors that
contribute to success (Weinstein et al. 2005).
In Australia, safety professionals created a tool called Construction Hazard Assessment
Implication Review (CHAIR) which brings together all the key stakeholders involved in the
design to help identify and eliminate inherent risks (WorkCover 2001). It provides a structured
review process that incorporates focused reviews at different points in the design phase. The
reviews provide a structured and systematic means to examine construction, maintenance, repair
and demolition safety issues associated with a design. The elements of design and the steps of
the proposed construction tasks can be considered through different phases.
In the Netherlands, Frijters and Swuste (2008) proposed a method which incorporates ten
steps for choosing between alternative building elements to integrate safety and health into the
design process. Two approaches are proposed based on the different timings for making
revisions. The first one is the “Rectilinear approach”. If the design for safety software finds that a
particular building element comprises a risk after the preliminary decision has been made, then
the preliminary decision is asked to be reviewed and the design to be re-drafted. The “interactive
method” intends to minimize the risks by taking appropriate measures during the design phase. It
is finalized by comparing all alternative options and selecting an appropriate one. The two
methods could be combined to generate a method which checks the documents both during and
after preliminary decisions have been made (Frijters and Swuste 2008).
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Last, a thorough risk assessment of each design component could be conducted by using
different design for safety tools which have been developed through past research studies. These
techniques and tools can be sorted into the following categories:
• CAD tools with built-in checking • Tool for drawing inspections • Tool for design “work through” • Checklist-based design reviews for typical weaknesses • Specification review
Checklists are one of the most widely used tools in the construction industry. IDC, a design
firm, developed a safety-in-design checklist, a database of design issues identified to address
potential problems for construction or facility operations. IDC developed the checklist as an
interactive and open-ended tool for designers (Weinstein et al. 2005). Meanwhile designers of
this project expressed their concern about time. The pace of the design and construction on the
project was fast, so the design team did not always welcome additional review steps and more
opportunities for comments to which they had to respond.
Construction specifications are another important tool for communicating between
designers and constructors. Boukamp and Akinci (2007) proposed a construction-specification
processing approach which allows for automatic reasoning about construction specifications to
determine their applicability to products in a project model and to extract requirements imposed
by them. Then a system that facilitates construction safety improvement is developed based on
this approach. The system could be used during the design phase to make designers aware of
safety implications resulting from specific designs. Also, the system could support safety
planning and evaluate the safety impacts of different construction methods (Wang and Boukamp
2007).
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Toole (2005) identified five tasks performed by designers in which they could potentially
contribute to increasing construction worker safety. Toole and Gambatese (2008) suggested that
design for construction safety is likely to evolve along four specific trajectories: increased
prefabrication, increased use of less hazardous materials and systems, increased application of
construction engineering, and increased spatial investigation and construction.
The Construction Industry Institute (CII) sponsored a research study to develop a design
tool titled “Design for Construction Safety ToolBox” that alerts designers of project-specific
construction safety hazards and provides suggestions on how a project can be designed to
eliminate or reduce those hazards (Gambatese et al. 1997). A database of over 400 design
practices was established through a review of construction industry publications and design
manuals. Interviews with engineers, architects, constructors, and construction managers were
also conducted to generate design for construction safety suggestions. The accumulated design
practices can be implemented during the design phase to reduce or eliminate safety hazards
during construction” (Gambatese et al. 1997).
The Design for Construction Worker Safety Toolbox, Edition 2, was developed in 2007
(Marini 2007) to meet the needs of CII. More than one hundred additional suggestions were
collected to enrich the knowledge base of the toolbox. Furthermore, the toolbox is based on new
authoring software which makes the tool accessible via the web. The database is much easier to
update because of the use of an XML file. Other functionalities such as navigation and print have
been designed for ease-of-use.
Researchers in Australia developed ToolSHeD (Tool for safety and health in design) to
help designers to integrate the management of occupational health and safety risks into the
design process. ToolSHeD provides access to information related to protection against falls from
39
heights during maintenance work on building roofs (Cooke 2008). It is a web-based system and
uses “argument trees” to effectively represent design safety risk knowledge.
Knowledge-based expert systems could also be used to facilitate the access of designers to
safety knowledge. In 2003, a prototype was developed in the U.K to structure HSE’s information
as a knowledge-based system for use by designers. More details about this system will be
introduced in the section of the computer-aided critiquing system.
To sum up, due to the current lack of legislation enforcing designers to fulfill design for
safety in the US construction industry, the decision to implement safety knowledge is ultimately
made by the design professional. This implementation can be facilitated considerably through the
efforts of facility owners and contractors. Through the past decades of research effort, the
improved design processes which allow for the consideration of worker safety during the design
phase of the project have been created. Design for safety knowledge and design tools that
facilitate designers being a part of addressing hazards that could contribute to construction site
injuries and fatalities have also been accumulated and developed. All of these approaches and
tools will significantly benefit the entire construction industry.
Building Information Modeling
This section introduces the role and potential impact of information technology on the
construction industry. It also defines the concept of Building Information Modeling (BIM).
Various BIM applications are explored. The connection between construction worker safety and
the delivery method is also examined and a new delivery method (Integrated Project Delivery
Method) is introduced.
Adoption of Advanced Information Technologies in Construction Industry
Information technology (IT) facilitates the architecture, engineering and construction
(AEC) industry to model, analyze, simulate, and predict a project’s performance. Methods and
40
approaches are proposed to integrate project information and leverage information across
disciplines and phases to enable better work processes and to make more reasonable project
decisions (Fischer and Kunz 2004; El-Mashaleh et al. 2006).
Information technology also makes it easier and more cost effective for AEC managers to
manage the safety of their employees. In the past decades, information technology including MS
Word made it easier and cost-effective to process the documents which helped promulgate
OSHA standards. Now, more powerful information technology makes possible the coordination
and integration of information across disciplines and throughout several phases. New tools and
approaches that support the concept of optimization of a project’s design from the perspective of
multiple disciplines are emerging (Fischer and Kunz 2004). More research studies on the
efficient means for providing designers with information needed to perform design for
construction safety are needed.
The construction industry is usually slow in adopting and utilizing new technologies
because of existing barriers (Mitropoulos and Tatum 2000). Barriers keeping contractors from
using the latest technology include fear, initial investment costs, the time to learn how to use the
technology, and the lack of support from the senior company leadership (AGC 2006; Toole
1998). There are also driving forces that prod the construction industry to adopt new information
technologies. The driving forces include competitive advantage, process problems, technological
opportunity and institutional requirements (Mitropoulos and Tatum, 2000). When the AEC
industry finds that certain information technology could provide tremendous opportunities, that
technology will be widely adopted. Building Information Modeling (BIM) is a good example, as
it has been swiftly adopted because project stakeholders perceive the significant benefit of
implementing BIM technology.
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Concepts of Building Information Modeling
Building Information Modeling (BIM) will be described and two important characteristics
of it will be introduced. The legal issue related to the use of Building Information Modeling will
also be explained.
Definition of Building Information Modeling
In recent years, Building Information Modeling (BIM) has gained considerable
professional and industrial attention. The earliest concept was published in an AIA Journal by
Professor Eastman in 1975 (Eastman et al. 2008). After more than three decades of development,
it is now regarded as one of the most promising developments in the AEC industry.
There are multiple definitions of Building Information Modeling. In the BIM handbook,
Eastman (2008) defines BIM as a modeling technology and an associated set of processes to
produce, communicate, and analyze building models.
The AGC defines BIM as “the development and use of a computer software model to
simulate the construction and operation of a facility. The resulting model, a Building Information
Model, is a data-rich, object-oriented, intelligent and parametric digital representation of the
facility, from which views and data appropriate to various users’ needs can be extracted and
analyzed to generate information that can be used to make decisions and improve the process of
delivering the facility. (AGC 2006)”
The National Building Information Standard Project Committee defines BIM as “a digital
representation of physical and functional characteristics of a facility. A BIM is a shared
knowledge resource for information about a facility forming a reliable basis for decisions during
its life-cycle from inception onward. (NBIMS 2006)” This third definition is deemed most
applicable to this research study.
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A related term is Virtual Design and Construction (VDC) which is proposed by the Center
for Integrated Facility Engineering (CIFE). VDC is the “use of integrated multi-disciplinary
performance models of design-construction projects to support explicit and public business
objectives. (Kunz and Fischer 2009)” It forms an integrated framework and set of methods to
manage the construction project, including those aspects of the project that must and can be
designed and managed. The building, the design-construction process and the organizations
follow the processes to design, build and operate the building (Kunz and Fischer 2009), while
Building Information Modeling (BIM) focuses on the building elements of the VDC model. BIM
can be viewed as a subpart of VDC or VDC can be viewed as the ultimate state or end-game or
BIM automation (Eastman et al. 2008). In practice, VDC and BIM are usually interchangeable,
but BIM will be used primarily in this research study.
In the past 50 years, CAD (Computer-Aided Drafting) has been widely used in the
architectural profession. As a new information technology, BIM as a design tool is different from
CAD in several ways (Eastman et al. 2008; Greenwold and Driver 2007). First, BIM offers
higher-level geometry operations than CAD does, so designers can represent entire objects rather
than drawing sets of lines and points. Designers can define much more complex structures of
object families and the relationships that exist between them. Second, the BIM design tool entails
a great deal of domain-specific knowledge. Third, BIM model users can define object families in
their own way without resorting to computer programming. Last, as a single unified description
of a building, BIM can facilitate coordination between project participants.
Characteristics of Building Information Modeling
Parametric modeling is a critical capability of BIM which makes the automatic update
features possible, and significantly enhances the model’s productivity. To some extent, BIM
could be viewed as an object-based parametric model with a set of object families. Standard
43
practices and codes can be programmed and embedded within it to define object behaviors
(Eastman et al. 2008). Users could use both predefined and customized object families. The
predefined object families include both vendor-provided families and web-based downloadable
families. A custom object family can be created when a needed object family does not exist.
Interoperability is another characteristic of BIM. As different application software is
needed to support all of the tasks associated with building design and production, interoperability
should be considered when passing data between different software. It identifies the need to pass
data between applications, and for multiple applications to jointly contribute to the work at hand
(Eastman et al. 2008). There are four main ways to exchange construction data between two
applications. One of them is the public level exchange format which uses an open-standard
building model such as Industry Foundation Class (IFC).
IFC as a data model was developed by the International Alliance for Interoperability (IAI)
to create a large set of consistent data representations of building information for exchange
between AEC software applications. One of the applications of IFC format is to check the
preliminary concept design against the specific project’s programmatic spatial requirements
(Eastman et al. 2008). Many organizations such as Singaporean CORENET and the International
Code Council (ICC) in the U.S. are working on this.
Legal issues
Legal issues such as who owns the construction databases, who pays for them, and who is
responsible for their accuracy are challenges faced by BIM users. Professional groups have
developed guidelines for contractual language to cover issues raised by the use of BIM
technology (Eastman et al. 2008). ConsensusDOCS 301 BIM Addendum is a standard document
to globally address the legal uncertainties associated with utilizing BIM. It provides a tool to
utilize BIM from start to finish, so contractors could closely integrate project delivery with
44
owners and design professionals (AGC 2008). The AIA E202-2008 establishes the procedures
and protocols the parties agree to follow with respect to the development and management of a
Building Information Model throughout the course of the project. Meanwhile, it is not a stand-
alone document, but it is intended to be attached as an exhibit to an existing agreement for design
services or construction of a project (AIA 2008).
As suggested by the AGC, while the use of BIM may well change the ways that projects
are conceived, designed, communicated, and built, it will not change the core responsibilities of
the members of the project team (AGC, 2006). “Contractors and construction managers will still
need to organize and lead the onsite construction effort; BIM technology vendors must ensure
that their solutions facilitate the building process and these relationships as they exist rather than
attempt to shift the responsibilities of the project team members into a contrived software work-
flow process” (AGC 2006; Khemlani 2006). A broader view of the legal issues can be found in
other reports (Larson and Golden 2008; AGC 2006).
Building Information Modeling Software
IFC interface
Various BIM architectural design tools (e.g. Autodesk’s “Revit” and Bentley’s
“Architecture”) grew out of the object-based parametric modeling capabilities developed for
mechanical systems design. Object-based parametric modeling represents “objects by parameters
and rules that determine the geometric and non-geometric properties and features” (Eastman et
al. 2008). Often a building model cannot be directly exchanged between different applications
because different BIM design tools rely on different definitions of their base objects.
Considering that no single computer application has the ability to conduct all kinds of
work, the building information needs to be passed between different applications. In the right
portion of Figure 2-6, there are different types of downstream applications which are developed
45
for specific usage. The interoperability must be realized on a project where different teams are
using different software. To solve this problem, the IFC data model has been adopted as the
international standard for data exchange and it will be used in this research to transfer data from
a BIM architectural design tool to a design for construction safety toolbox.
Figure 2-6. IFC Interfaces (Adopted from: Eastman 2008)
Classification of BIM software
BIM software can be classified into several categories: architecture, structural engineering,
MEP, construction, planning and visualization, codes and specifications, facility and asset
management, etc. Figure 2-7 shows a graph developed by the Quarry Group, which depicts the
classification of current BIM software. It shows that various software applications are divided
46
into different disciplinary categories. It also illustrates how data are transferred between different
software (Quarry Group 2009).
Figure 2-7. BIM roadmap (Adapted from: Quarry Group 2009)
Pre-design tools such as Onuma Planning System (OPS) are used to facilitate
“information-gathering” or “decision-making” processes in the early stages of a project (Smith
and Tardif 2009). Authoring tools, such as Autodesk Revit, Bentley Architecture, and Graphisoft
ArchiCAD are developed for building design. Design firms also use audit and analysis tools
which can only be used to analyze building information models created by authoring tools such
47
as Revit Architecture (Smith and Tardif 2009). Audit and analysis tools are used to do specific
work such as clash detection, sustainable design analysis, code compliance, and cost estimating.
BIM can be used by constructors to conduct construction cost estimating, constructability
analysis, and construction sequencing. Owners can utilize BIM to do facility management and
maintenance.
Code checking software
One software application that warrants a detailed analysis is one designed for code
checking. In civil engineering, most of the expert knowledge has taken the form of codes and
regulations. The purpose of a building code is to establish minimum requirements necessary to
protect public health, safety and welfare in the built environment (Wix and Liebich 2009). It is
different from the design for construction safety knowledge because the principle of design for
construction worker safety is to protect construction workers during the process of construction.
Another difference between them is that there are currently no administrative processes to
enforce designers and constructors in fulfilling design for construction safety responsibilities or
to ensure that projects are in compliance.
The traditional manual code checking method is time-consuming and error-prone. The
vision of automatically checking building plans against codes emerged as early as the 1970’s.
Before the 21st century, researchers had made some progress in this area. However, it was not
until recent years that the new generation of software technology and standards made automated
checking much easier (Wix and Liebich 2009).
In the U.S., automated code checking was championed by the International Code Council
(ICC). The ICC is a membership association dedicated to building safety and fire prevention by
developing the codes used to construct residential and commercial buildings. Many U.S. cities,
counties and states adopt codes developed by the ICC ( 2009). Since 2004, the ICC tried to use
48
object-based technology for representing their codes and created the SMARTcodes project. The
ICC is currently cooperating with corporations such as Solibri and AEC3 to develop the platform
for its automated code checking.
Solibri, Inc is the pioneer in providing “out of box” software that automates the checking
and analysis of the BIM model (Solibri 2009). Solibri Model CheckerTM (SMC) is an IFC
model checker. SMC imports models created in other software packages and checks them for
compliance with rules. These rules can be a comprehensive set of general purpose BIM checking
rule sets or user-defined specific rules. This tool has great potential for owners and code officials
to quickly verify if building models are in compliance (Solibri 2009; Quarry Group 2009).
COMcheck and REScheck were developed by the U.S. Department of Energy (DOE) to
improve the energy efficiency of the nation’s buildings by promoting building energy codes.
These software tools simplify energy code compliance by offering a flexible computer-based
alternative to manual calculations (DOE 2009). More information can be obtained from the
DOE’s website for the building energy codes program.
BIM has been defined and several types of software tools related to this research have been
introduced. Even though BIM technology offers considerable benefits to the construction
industry, adopting BIM technology alone will not eliminate all the construction worker injuries
and/or guarantee a successful project. Construction work is so dynamic that many other factors
will influence the outcome of the project. Without excellent management and safety-oriented
stakeholders, a zero injury objective cannot be achieved.
Delivery Method Influence on Safety Performance
Designers often do not have the expertise to make the design drawings sufficiently safe for
construction workers to finish the construction work without injury. The inadequate
interoperability partly causes this problem. Interoperability identifies the need to pass data
49
between applications, and for multiple applications to jointly contribute to the work at hand
(Eastman et al. 2008). Studies show that the lack of interoperability can cause tremendous
inefficiencies and waste in the construction industry. For example, a report of the National
Institute of Standards and Technology (NIST) determined that the AEC software had inadequate
interoperability that totaled costs of $15.8 billion per year (NIST 2004). One major reason for the
present situation is the current project delivery methods do not support cooperation and data
exchange between project participants.
The longstanding separation of the roles of architects and contractors makes it difficult for
team members to share knowledge and common project data. In the most prevalent delivery
method of Design-Bid-Build (Figure 2-8) for example, the designer develops a design based on
the owner’s requirements, then a constructor is selected to build it.
Figure 2-8. Participant relationships in the design-bid-build method
With this procedure, the project is designed with little expertise from the constructor who
actually constructs the project. As a result, many constructability and safety issues are not
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considered until the construction phase. Furthermore, public works projects often dictate that
“open bidding” must be used in government construction projects, so substantive early
involvement of the actual constructor is essentially prohibited (AIA 2007).
The early period of the design phase is important for the project. As Figure 2-9 shows, the
project team’s ability to affect project variables such as cost, schedule and constructability
decrease as the project progresses. Meanwhile, the cost of making changes dramatically
increases.
Figure 2-9. Team’s ability to affect project variables (Adapted from: Eastman 2008)
The type of project delivery method will impact the extent to which safety can be
addressed in the design. The forms of project delivery alter the roles played by the different
parties and the allocation of their responsibilities. A 1992 study found that design-build firms
addressed safety in their project designs more often than design-only firms (Hinze and Wiegand
1992). Gambatese (2005) criticized the traditional general contract (design-bid-build) approach
as keeping the parties isolated, with no payback apparent for the designers to address
construction worker safety. Alternative project delivery methods can be used to access the
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constructor’s knowledge to find safety hazards and to facilitate the implementation of design
modifications (Gambatese et al. 2005b). Toole (2007) also confirms that both the fee structure
and model contract terms of a design-build project could induce design engineers to consider
construction safety during the design phase. Ash (2000) contends that Great Britain’s
Construction Design and Management (CDM) regulations which place a duty on designers to
ensure design for safety yields some success when designers and constructors work together
more closely, such as in design-build and construction management companies.
Integrated Project Delivery method
To solve the current problem, the Integrated Project Delivery (IPD) method has been
introduced. The AIA (2007) defined IPD as a project delivery approach that integrates people,
systems, business structures and practices into a process that collaboratively harnesses the talents
and insights of all participants to optimize project results, increase value to the owner, reduce
waste, and maximize efficiency through all phases of design, fabrication, and construction.”
Integrated projects are uniquely distinguished by highly effective collaboration among all
participants to maximize value for the owner, commencing at early design. Figure 2-10 shows
that project flow in an integrated project differs significantly from a non-integrated project.
Design decisions are moved upstream as far as possible to make the process more effective and
less costly (AIA 2007).
Specifically, IPD allows constructors to contribute their expertise in construction
techniques early in the design process resulting in improved project quality and financial
performance during the construction phase. IPD leverages early contributions of knowledge and
expertise through the utilization of new technologies. The IPD allows the designer to benefit
from the early contribution of the constructors’ expertise during the design phase. Designers can
fully understand the ramifications of their decisions at the time the decisions are made. The close
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collaboration eliminates a great deal of waste in the design, and allows data sharing directly
between the design and construction team, thereby eliminating a large barrier to increased
productivity in construction.
Figure 2-10. Traditional and redefined project phases (Adapted from: CURT 2004; AIA 2007)
Since project participants share expertise and risks, Figure 2-8 could be modified as shown
in Figure 2-11 which demonstrates the situation under the IPD method. All the stakeholders of a
project will own one database which incorporates all the information about the project. Even
though architectural and structural engineers will have their own drawings, their models will be
derived from one database. Different stakeholders will have different authorities to access or
revise the database. After the project is finished, the owner will have ownership of the database.
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Figure 2-11. Participant relationships in a project under the IPD method (Adapted from:
MacLeamy 2009)
Contracts that define new business terms that facilitate collaboration are essential for
adopting the integrated delivery method. They could help designers find opportunities in
nontraditional areas throughout the life cycle of projects (CURT 2005). Unlike traditional
construction contracts, the discrete responsibilities of the designers and constructors are more
intertwined. For the benefit of the project participants, every participant’s work scope should be
clarified in the IPD agreement after negotiating the risk allocation on the project. Both the AIA
and AGC have launched agreements supporting IPD. The ConsensusDOCS 300 brings owner,
design professional and constructor together as a core team to act on behalf of the project
(Perlberg 2009). The AIA has introduced two types of agreement packages for the emerging
process. The “Transitional Agreements” are a first step to IPD, providing for an early
collaboration of project participants in an arrangement modeled after existing construction
manager agreements (AIA 2009). When the project participants are fully prepared, “Single
Purpose Entity” could be used. It allows a complete sharing of risk and reward. With this type of
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agreement, the participants work together to design and construct the project with mutually
agreed-upon cost goals. Both types of agreements encourage project participants to implement
BIM to realize the full potential benefits.
Integrated Project Delivery with Building Information Modeling
The IPD process unlocks the power of BIM (Yoders 2009; AIA 2007). The full potential
benefits of both IPD and BIM can be achieved only when they are used together. The IPD
project team reaches an understanding regarding how the building model will be developed,
accessed, and used, and how information can be exchanged between different participants.
Without such a clear understanding, the model may be used incorrectly or for an unintended
purpose (AIA 2007).
Some projects have successfully used IPD and BIM together to deliver projects to owners.
These initial practices show how BIM and IPD could be used together to deliver a project by
reaching criteria such as design aesthetics, materials selection, budget, schedule, and
sustainability (Yoders 2009). Some key elements were summarized to help succeeding project
stakeholders.
In summary, the change in delivery methods provides project participants with new
opportunities to succeed. Project participants must take on new roles and competencies to
achieve it. More benefits could be realized by using IPD and BIM together.
Computer-Aided Critiquing System
Computer-Aided Critiquing System in Design and Construction
Knowledge-based expert systems are a subfield of Artificial Intelligence (AI). The
fragmentation of the U.S. construction industry causes tremendous inefficiencies in all phases of
a construction project. In the past decades, several knowledge-based expert systems with
different functions have been developed in design and construction domains to reduce these
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adverse impacts of fragmentation (Fischer 1991). Many different problems which need specific
expertise now could be solved at the field level.
When the knowledge-based expert system technology is used in the design process to
support designers in different domains, it can be called a computer-aided critiquing system or an
automated critiquing system. According to Oh et al. (2008), the definition of a computer-aided
critiquing system used for design purposes is:
A design critiquing system is a tool that analyzes a work-in-progress and provides feedback to help a designer improve the solution. It may ask relevant questions, point out errors, suggest alternatives, offer argumentation and rationale, or (in simple and obvious cases) automatically correct errors.
A critiquing system not only alerts designers to their errors, but also helps designers
improve their drawings with “constructive” feedback (Oh et al. 2008). Notable critiquing
systems include Singapore’s CORENET system and Solibri Model Checker.
Summary of Related Work
Researchers have developed a few automated critiquing systems to support designers when
making design decisions. In this subsection, the mechanism of some of these systems will be
analyzed. Three criteria should be considered when selecting the model system. First, the system
should be developed to assist the architects/engineers in making informed decisions by providing
them with machine-generated feedback. Second, the critiquing system should have the
knowledge-based reasoning function which could automatically check inputted drawings based
on encoded rules. A knowledge-based reasoning structure consists of a set of rules with logic
equations that use the object attributes in the 3D model to assist the user in making informed
decisions (Korman and Tatum 2006). Last, the data for the buildings which will be input into the
checking system should be created in object-oriented three-dimensional (3D) models, in which
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the basic components of drawings are building elements such as walls, doors, and so on, rather
than geometric elements in the traditional CAD software.
Fischer (1991) developed the Construction Knowledge Expert (COKE) in the early 1990s,
which indentifies design-relevant constructability knowledge to help designers of concrete
structures check for constructability issues during the initial design. First, COKE builds a
symbolic geometrical and topological project model based on the information in the CAD
system. That object-based CAD system was specifically developed to create the project data for
constructability feedback because CAD systems at that time could not effectively link to an
expert system. The system uses high level application heuristics to determine whether a
construction method is applicable of not. Lastly, the system compares the project data in the
symbolic model with specific constraints about the layout and dimensions of structural elements.
If any conflict is identified, the system will alert the designer (Fischer 1991).
A more recent effort of CIFE was to promote the coordination of the MEP trades. Korman
and Tatum (2006) proposed a knowledge-based system that is able to provide valuable insight to
engineers and construction personnel, to assist them in resolving coordination problems for
multiple MEP systems. The system uses object-oriented 3D models and a knowledge-based
reasoning structure to assist the MEP coordination process by linking components of an object
with a particular set of knowledge. In an earlier research study, they developed a knowledge
framework and reasoning structure for the system. The model-based reasoning (MBR) method
and the heuristics method are used as the reasoning structure to perform diagnostic tasks. MBR
could abstract geometric and topological data from the geometric model and then determine the
spatial relationships between the components in the model. After classifying the types of
interferences, heuristic reasoning is used to determine and resolve coordination conflicts.
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CORENET (Construction and Real Estate NETwork) was an IT initiative conducted by the
Singapore government to re-engineer the business processes of the construction industry. One
task of this project was to develop an automated national building code compliance checking
system called e-Plan Check. Owners could submit building models in IFC format to the
Singapore regulatory agency for automated code checking by this system.
One of the important projects in CORENET is the Integrated Building Plan and Building
Services System (IBP/IBS). This part of the project was developed through a coordinated effort
with Jotne EPM Technology AS, Norway, by using EPM’s software applications. The
applications of EPM Technology are based on the EXPRESS Data ManagerTM (EDM) utilizing
ISO standards, particularly ISO 10303, which is a STEP or Standard for the Exchange of Product
model data. One application in this suite of products is EDMmodelCheckerTM which provides
validation of the dataset being used based on the EXPRESS data modeling language (Jotne EPM
Technology 2009). This module has been used to implement the e-plan Check system.
With the passage of the Construction (Design and Management) Regulations 1994, the
U.K. Health and Safety Executive (HSE) was concerned that safety should be as much a key
aspect in design as it is during construction and operation (AEC3 2009). The belief was held that
the poor health and safety record of the construction industry could be improved by encouraging
designers to give more consideration to health and safety issues during the design stage (HSE
2003). NNC Limited, a U.K company, cooperated with AEC3 and IAI UK to develop a
prototype system in which health and safety information is structured as a knowledge-based
system that can be delivered to designers. The whole project was split into five phases, with three
being directed to the development of the system. These three phases include: data gathering, data
structuring and data delivery. The data are primarily concerned with the hazards while working
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at height, and accidents due to falling objects. The major sources of safety and health
information included an invited health and safety consultant, documentations available from the
HSE and experiences of designers from both internal and external to NNC Limited. These data
are classified and structured into three areas: (1) textual health and safety data; (2) health and
safety rules; and (3) object properties. A software application should be selected as the platform
to deliver the information. After investigating the viability of the system that could carry out the
checking function, the HSE prototype used software that was developed by Singapore
CORENET as the design checking mechanism because the building regulations compliance
checking is analogous to the checking of designs against health and safety risks (HSE, 2003).
Last, an object-based CAD system exports design data in the IFC format to an EDM database
provided by EPM Technology. Design data are tested against health and safety requirements that
are graded according to levels of risk. The checking results are reported through graphic and
rule-browsing software (AEC 2009; HSE 2003).
As introduced in the Code Check Software section, in 2004 the International Code Council
(ICC) began to develop object-based technology to represent their codes and to test submitted
construction documents. The key elements are a model checking application and SMARTcodes.
The following paragraphs will explain the project by analyzing two major tasks: encoding
building code requirements into a rule base and developing model checking software.
The International Code Council (ICC) defines the SMARTcodes as “I-Codes in an IFC
(Industry Foundation Classes) compliant, interoperable format that can be used by Model
Checking Software (MCS) as a rule set of limits or constraints from the code and applied by the
BIM to show where conflicts occur (ICC 2009).” To encode the SMARTcodes, the obstacles are
the interpretation and presentation of the building code and the encoding of that presentation in a
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rule base (Conover 2009; Nisbet 2008). A protocol and software program were used to create
tagged representations of building codes that have a tagging schema that reflects the logic and
requirements of the codes from the text of the codes (Conover 2009).
An online version of the Solibri software application or the AEC3 Xabio web-based test-
bed could be adopted in the model checking application. Solibri Model CheckerTM (SMC) is a
product of Solibri, Inc. This application is designed to find potential problems, conflicts, or
design code violations in a building model through three steps. First, the user creates a building
model in an IFC-compliant application and saves it in the IFC format. Next, the user selects and
loads the specific rule sets that will be used for checking the model. Last, the application
automatically conducts the checking and produces the results. Users could export a report from
the applications for further analysis. The key point to successfully use this application is to
develop rule sets which can be used for projects of different types and in different locations. The
application provides a number of default rule sets and the user also can develop customized rule
sets (Khemlani 2009). In the SMARTcodes project, a customized version of Solibri Model
Checker is adopted as the model checking application.
Figure 2-12 depicts a block diagram of “a system for checking a building information
model against SMARTcodesTM in a trusted entity”. The BIM authoring software is software
that creates and maintains a building model.
Besides Solibri checker, AEC3 XABIO also can be used as the checking engine in ICC’s
project by sharing a dictionary of testable concepts which are defined both in plain language and
in buildingSMART terms with SMARTcodes (Nisbet et al. 2008). It uses EPM and Octaga
technology.
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Figure 2-12. Block diagram of a system for checking a building information model against
SMARTcodesTM (Adapted from: Conover 2009)
AEC3 XABIO can check a whole regulation or an individual clause and then generate a
full explanation. It is also web-based in cooperation with the Apache Software Foundation and
Octaga. On the website of ICC, videos demonstrate the trial system which uses Solibri or AEC3
XABIO checking engines. The e-Plan Check is also used as the checking engine to show the
interoperability of the SMARTcodes (AEC3 2009). Figure 2-13 shows the relationship between
three different checking engines. Checking systems based on these checking engines are also
demonstrated.
The SMARTcodesTM project started from energy codes which are relatively easy to
define and codes in other domains were gradually formalized into rule sets. Furthermore, this
system currently does not promise full automation since some codes that are nuanced and subject
to interpretation will have to be checked manually (Khemlani 2009).
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Figure 2-13. Predominant checking systems
House Designer is a graphical tool for product and house design developed by Selvaag
BlueThink. Several rule sets, such as geometry rules, functional rules and building systems can
be defined in the system. This software can generate a building from rules, not just passively
checking if building models satisfy certain rule sets. The user sketches the functional intent and
layout, and the House Designer applies the rules and automatically works out the various
elements and decisions that constitute a complete building design. The software immediately
warns the user when conflicts appear and rules are violated (Selvaag, 2009).
This section described some computer applications related to this research. Table 2-2
summarizes some computer applications associated with this study.
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Table 2-2. Computer-aided critiquing systems Name Purpose Knowledge Bases Developer Date COKE Provide constructability
feedback for the preliminary design of reinforced concrete building structure
Constructability knowledge
CIFE 1989
Prototype Mechanical, Engineering, and Plumbing Coordination Tool
To assist in MEP coordination during the design stage
Design criteria, construction, operations, and maintenance
CIFE 2003-2006
CORENET e-Plan Check
Check design for regulatory compliance through the internet gateway
Authorities Regulations
Singapore BCA
Since2000
Knowledge Based Expert system
Deliver health and safety information to designers
Information concerning hazards of working at heights
UK HSE & NNC Limited
2003
Solibri Model Checker
Provide commercial model checker
Rule sets Solibri, Inc 1999
AEC3 XABIO Check regulations or an individual clause
Rule sets AEC3 2006
BlueThink House Designer
Product and house design
Rule sets Selvaag 2007
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CHAPTER 3 METHODOLOGY
The initial objective of this research was to explore how BIM technology can be used to
support construction safety efforts. This was dominated by developing a design for construction
safety (D4S) software tool which can automatically check building models to identify potential
hazards on construction site. Only after identifying the safety hazards can the engineers and
constructors assess and mitigate identified hazards prior to or during the construction phase.
Specifically, this research study was focused on identifying the fall hazards, as falls are the most
frequently occurring types of accidents resulting in fatalities, which account for forty percent of
all construction worker fatalities. With 36 collected best practices related to falls, particular
emphasis was placed on openings located either in floor slabs or in walls in that falls are often
associated with workers on roofs and floors with openings. Hinze and William found that falls
from roofs/ floor edges and falls through roof/floor openings accounted for 40% of fall fatalities
(2011). The falls associated with scaffolds and ladders are not discussed at the current stage
because most of these are temporary structures and are difficult to associate with specific
building locations.
The research methodology for this research consists of six sections:
The first section discusses the possible influences of BIM technology on construction
safety. Then the opportunity of using a computer-aided critiquing system that provides design for
safety knowledge to designers is assessed. The second section analyzes a typical design process
to identify the appropriate timing at which to conduct design for construction safety checking to
effectively deliver the safety knowledge to designers under the environment of computer-aided
critiquing systems. The third section presents the work of collecting existing design for
construction safety suggestions from past research results and efforts to develop new suggestions
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to enrich the knowledge base. These collected suggestions are classified into five categories as
falls, struck by, caught in/between, electrical shock and others. For this research study the
software tool is exclusively focused on fall hazards. The fourth section explains the ideal
architecture and functionalities of the tool. It also explains other features of the tool, such as the
software interface and interactive method between the user and the model checking software.
The fifth section introduces the process of selecting a viable authoring environment as the
platform to develop model checking software. These software platforms can be classified into
different categories based on the programming languages used to compile the computable rules
and an assessment of how friendly the user interfaces are. The sixth section differentiates
between the semantic query and spatial query. The usage of a library to constrain the
terminologies is introduced. It is the technical foundation to compile the computable rules. The
seventh section describes the methods of encoding collected fall protection safety suggestions
into computable rules which can be used as rule sets in different model checking software. The
eighth section discusses the preparation of building models which are used to test the compiled
computable rules.
Finding the influence of BIM technology on Construction Safety
As described in the introduction, the first objective of this research is to delve into the
potential impact of BIM technology on enhancing construction worker safety. To get an idea of
how BIM technology as a tool could address construction worker safety, the research effort
concentrated on two resources. Knowledge was acquired through a literature search to find the
potential positive impacts of BIM technology on construction worker safety. During this process,
various textbooks and journal papers were reviewed. The Internet was also found to provide
valuable knowledge related to this research.
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After evaluating the current usage of BIM technology in the construction industry, it was
concluded that design for construction worker safety is an appropriate area where BIM could be
used to enhance construction safety. That is, while the theory of design for construction worker
safety has been gradually established through past research studies, the implementation of this
concept has not been widely carried out in project designs. There is a compelling need for tools
that can put the safety-in-design concept into practice. Thus, the second objective of this research
is to discover a means by which design for safety knowledge can be implemented in practice by
using BIM as a tool.
Based on previous research, it was recognized that the development of a model checking
system is a viable approach to deliver valuable design for construction worker safety suggestions
to design professionals. The various advantages of BIM technology made a computer-aided
critiquing system/model checking system be an advanced application to address construction
worker safety during the design process.
After identifying design for construction worker safety as the specific topic of this research
and a model checking system as the tool to address this issue, the primary effort was to analyze
the current design process to identify the appropriate time to conduct design for construction
safety checking work by using such a tool.
Design for Construction Safety Process
There are many small details that need to be taken into account during the design phase. As
a result, only the best designers consider design for construction worker safety as an integral part
of the main design process. Potential construction hazards can be easily designed into building
models during the design process, so design reviews should be conducted to detect
noncompliance and make designs safer. One of research questions is to determine when to
conduct a design for construction worker safety building model review.
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Ideally, a computer aided-critiquing system performs two major tasks to help designers
provide high quality building models in a mature design process. One is to minimize
noncompliance during the main design phase by informing and training designers about
alternative design options and the consequence-reducing practices. Another method is to conduct
noncompliance detection and correction after the main design work has been completed by
carrying out safety checks. By using these two methods, a design for construction safety tool
could be able to improve designs by providing appropriate knowledge or checking the final
building models. Past research studies have recognized, however, that a limited number of
progress reviews for safety may be more favorable. That is, because of the pressures on
designers to meet deadlines and budgets and to solve problems, design for construction safety is
usually ignored in the design process.
One merit of a computer-aided critiquing system is that it can facilitate the access by
designers to the design for construction safety (D4S) knowledge during the design process or
assist designers in making decisions which are more constructable for the project life cycle.
Because of the limitation of the current model checking software, the D4S software tool is
mainly focused on checking for noncompliance of the finished building model. This tool also
provides other functions such as model navigation, result presentation, and report generation.
The issues about when and how to conduct a safety review have been discussed in the
previous two sections. The following sections are focused on developing a model checking
system which can be used to automatically check building models for noncompliance.
Defining the Rule Source
To develop the model checking system, the design for safety suggestions that were
incorporated in the database must first be collected. This section describes the process of
accumulating existing and new design suggestions. The existing suggestions came primarily
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from two previous editions of a safety toolbox. New design suggestions included provisions from
the OSHA regulations, publications of the National Institute for Occupational Safety and Health
(NIOSH) and knowledge from the HSE of the U.K.
Existing Design for Construction Worker Safety Suggestions
Previous research had already developed and compiled numerous designing for safety
suggestions. The first edition toolbox developed by Hinze and Gambatese (1997) included 430
design for safety suggestions. Marini (2007), in the second edition of the toolbox, added more
than one hundred new suggestions into the database. These suggestions were collected from
safety design manuals and checklists, ideas generated by the researchers and CII research team
members, and interviews with industry personnel. Through these previous two research efforts,
nearly all the major potential problem areas had been examined and corresponding design for
safety suggestions had been developed. In the second edition of the toolbox, these existing
suggestions were classified into 20 categories. The following list shows these categories:
• Administrative: Layout • Administrative: Planning • Administrative: Design • Sitework: Layout • Sitework: Roads and Paving • Sitework: Earthwork • Foundations • Roofing • Structural: Steel • Structural: Concrete • Structural: Masonry • Structural: Timber and Wood • Finishes: General • Finishes: Stairs and Railings • Finishes: Ladders • Doors and Windows • Mechanical and HVAC • Electrical • Industrial Piping
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• Tanks and Vessel
This sorting method was reasonable and proved to be effective for the second edition of the
toolbox. Other classifying methods that are more suited to the object-oriented software were
considered and will be discussed in the following subsections; however, before the model
checking software was finally confirmed, the above sorting method was used to classify and
compile new suggestions.
New Design for Construction Worker Safety Suggestions
There were two major sources of the new suggestions. The first one was from the U.K.
HSE. Other new suggestions were gained from examining the OSHA regulations.
The passage of Construction Design and Management (CDM) has tremendously promoted
the implementation of design for construction worker safety in the U.K. The Health and Safety
Executive (HSE) as the official in charge of safety has accumulated considerable safety
knowledge which can be used in this research. The design for safety suggestions which were
collected during the project –“Knowledge Based System To Deliver Health And Safety
Information To Designers” especially focused on how to avoid risks while working at height.
The possible differences between the U.S. and U.K. construction industries should be
considered.
Meanwhile, additional suggestions were collected by further examining the OSHA
regulatory provisions. As the employer of construction workers, the constructor is given the
primary responsibility for worker safety. Also, the OSHA standards and policies for the
construction industry are directed at the constructor (Toole and Gambatese 2002). The voluntary
participation of designers in the OSHA training and education can potentially increase
construction site safety.
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Some OSHA provisions involve architects and engineers or include several instances
where the services of a professional engineer are required for analysis and design of temporary
construction structures. Meanwhile, designers should possess at least a limited degree of
expertise in construction safety to contribute to construction worker safety. In another words,
they should be familiar with the OSHA regulations. Unfortunately, most designers know little
about the OSHA regulations. In the survey conducted by Gambatese (2003), none of the 36
surveyed civil engineering departments offered a course strictly on construction safety. Another
survey conducted with design firms by Toole and Marquis (2004) found that less than one-fourth
of the U.S. participants believed that employees in their design firms were capable of identifying
site hazards to which construction workers are exposed. Some researchers have suggested that
10-hour and 30-hour OSHA courses for design professionals should be developed and promoted.
The OSHA regulations (Code 1994) were used to develop design suggestions in the
research conducted in 1996. Later, Gambatese et al. (2003) introduced more information about
“engineering mandates stipulated in OSHA regulations.” In this research, the OSHA regulations
were further analyzed and the literature (such as the Designer’s Guide to OSHA) was a helpful
resource to devise additional design for safety suggestions. The collected suggestions were
compiled and classified according to twenty categories previously listed. This helped ensure that
no duplications of existing suggestions were included in the database.
Classification of Design Suggestions
Through previous research, a large number of design for construction worker safety
suggestions had been collected. All suggestions were sorted into certain categories for future use.
The first edition of the safety toolbox used three ways or “paths” to sort suggestions:
project component, construction site hazards, and project systems. These three ways of accessing
design for safety suggestions were still valuable for this research study. In this phase, the
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feasibilities of these three methods were evaluated based on the function and architecture of the
new D4S software tool. Every way had its own merit when it came to manage knowledge. When
using project components, the application tool would present a list of components typically
found on construction sites. Considering object-oriented BIM applications also based on various
components of a building, this method could be a viable choice. Rather than examining a
particular component constituting a building, the designer could focus on specific jobsite
hazards. This can help designers access knowledge related to certain types of hazards. Major
types of causes of injuries and fatalities such as falls, cave-ins and electronic shock could be
controlled through this method. This was also the approach taken by HSE to develop their
knowledge-based system in the U.K. Classifying suggestions by project system was the third
way, which reflected the standard Construction Specifications Institute (CSI) format and
numbering system. The advantage of this method was that the International Code Council (ICC)
also adopted the CSI format to manage their building codes. Using a dictionary was a major
character of ICC’s SMARTcodes project. The advantage of the dictionary and classification-
based aspect of the work was that it enabled the codes to be searched to identify only those that
were relevant to a particular topic and to deliver these exclusive of all other, non-relevant codes.
The dictionary was managed by the CSI in cooperation with ICC. While using either of these
category methods could incorporate all the suggestion into the toolbox’s database, the first two
methods were jointly adopted to develop the D4S software tool.
Past research studies disclosed that fall accidents account for a large portion of
construction injuries and fatalities. For this research study, the rule sets of the D4S tool were
mainly focused on the potential fall hazards in the building models. That was done because most
D4S suggestions related to falls are directly associated with permanent building structures, which
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makes them easier to be complied into computable rules. The designing for construction safety
best practices were reviewed to identify those provisions that deal with fall protection. More than
thirty provisions on fall protection were identified. These provisions were further classified into
different groups based on their target building objects. The list of the design suggestions is
provided in the Appendix A. The classification of D4S best practices can be clarified by using a
tree shape diagram which is shown in the Figure 3-1. D4S suggestions were classified into five
categories, including falls, struck by, caught in/between, electrical shock and others. Falls can be
further sorted into five categories associated with different building components where accidents
happen.
Figure 3-1. Classification of design for construction worker safety best practices
The D4S safety suggestions were classified. The architecture and functionality of the
potential model checking system will be discussed next.
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Architecture and Functionality of the desired System
After D4S suggestions had been collected and classified, the next step was to develop the
proposed Design for Construction Safety (D4S) software tool--a construction safety checking
system. The purpose of this system was to automatically check imported building models which
are in IFC format or other document formats to alert users to opportunities for improving
construction safety. The system should provide design for construction safety knowledge
quickly, easily and economically. Software platforms were selected based on the requirements
discussed in this section to effectively deliver safety knowledge to users. According to the
technical requirements of these software platforms, suggestions were formalized and encoded to
rule sets, which also can be referred to as constraint model or computable rules.
The architecture of the software tool was first set up to define the scope of this tool.
Several issues were considered as important. Researchers had identified some factors which
should be considered when developing a computer-aided system (Oh et al. 2008). According to
experience from former research efforts, three features of the D4S tool were closely considered
when deciding when and how to intervene in the design process by the designers of this software
tool.
The first feature concerned the conditions under which the software tool would activate the
intervention function. Systems taking an active critiquing strategy would continuously monitor
designs as they evolve and offer feedback, while a passive critiquing strategy would only give
feedback when designers specifically ask for it. Because the timing of providing design for
construction safety knowledge had been decided in the second section, the system developed in
this study adopted the passive critiquing strategy to avoid distracting the designers as designs
evolve, although the active critiquing strategy may be a better solution for some approaches.
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The second feature concerned the type of feedback. The applications developed for code
checking work usually point out the specific errors in building models. The D4S software tool is
different in that it suggests the opportunities of integrating safety into the building models even
though the documents may be errorless. That is because currently the design for safety
knowledge consists of suggestions and there are no compulsory legal clauses to enforce their
fulfillment. So the software tool should be developed to not only offer negative evaluations but
also provide positive knowledge.
The third feature concerned the form in which the feedback will be reported to users. This
D4S software tool includes two types of feedback: text messages and graphical markers to
indicate the locations where improvements are possible. Text messages give detailed
explanations to designers to help them to better understand the design alternatives. By colorfully
marking the problematic components in the proposed three-dimensional drawings, the D4S
software tool explicitly shows designers the locations that need to be addressed.
After determining the course of action for the above three issues, the architecture of this
tool was defined. Figure 3-2 shows the desired architecture of the D4S software tool. The x-axis
represents the project process from the beginning of the design to the delivery of the documents
to the constructors. This process begins on the left with the design development period when the
designers draft the initial building models by using BIM authoring software. It then evolves into
the design review phase and the checking for code compliance period. Compliance checking of a
building model is conducted in these two phases. This culminates in the construction phase. The
design process is an iterative one. Users could submit building models and check against non-
compliance by using the D4S tool. After the report identifies the problematic building
components, the users can revise their drawings by returning to the architectural design tools.
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The core of the entire process is the model checking software which is supported by a dictionary
and a design for construction safety rule set. After the design for construction safety knowledge
has been incorporated into the construction documents, shop drawings can be used by the
constructors for further construction work.
Figure 3-2. Architecture of Design for Construction Safety tool
After the architecture of the D4S software tool had been determined, the next step was to
define the functionalities of the D4S software tool. The software tool was developed to have two
main functions. The first function consists of checking building models against the design for
construction safety rule sets. The second function of the D4S tool was to provide safety
information related to certain building components. This was based on both the characteristics of
the design for construction safety knowledge and the reasoning process of the software tool.
One of the differences between building codes and design for construction safety
knowledge is that a large number of design suggestions are in the textual format without any
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parametric information. Many of these suggestions were very difficult to be encoded into rule
sets that can be compared with the properties of building components and can be used to restrict
non-compliance. Consequently, it is better to keep their original form and show them to the user
in text format, while most of the building codes are connected to attributes that can be physically
measured. This point is very similar to delivering constructability knowledge to designers during
the preliminary design phase. In consideration of this point, this research needed to find an
appropriate way to deliver safety knowledge to designers.
Three possible ways were examined to find the appropriate methods for delivering design
for construction safety information to the D4S software tool users. The first type was “health and
safety rules” which could be checked by the model checking software for non-compliance. Most
suggestions related to objects which have clear design parameters that could be checked in this
way. Parameters could be set as rule requirements in the system. If the value of an object in the
drawing violates the parameter, then the system reports the non-compliance to the users. The
second type was safety knowledge in textual form. When a suggestion was too difficult to be
directly checked, the system should provide knowledge in textual form. Information in this form
can be general (e.g. locate rooftop mechanical/HVAC equipment away from roof openings), or
related to individual construction objects (e.g. locate roof opening away from the edge of the
structure).
The third method was to deliver information by using an object properties setting.
Designers could recode and deliver relevant health and safety information within their drawings.
For example, if a designer specifies the construction method for an object as “unusual”, the
designer could suggest to the constructors that this is an important point of concern during
construction. After assessing the entire mechanism of the D4S software tool, this method was not
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considered in this D4S application tool. One reason was that a large portion of the information of
this type is related to the construction method, which makes them inappropriate to be included in
the D4S knowledge database. Another reason was that designers need to do additional work to
input such properties, which makes this step more time consuming. All of these made this
functionality an unattractive one to designers. This application tool used the first two methods to
deliver design for construction safety knowledge to users.
Based on the software tool developed from Solibri Model Checker, the interface of this
D4S software tool consists of four sub-views:
• Model tree. It is a tree-view of all model objects. • Rule sets. Users can select rules that will be used to check the model. • Result view. Detailed explanation will be shown in this window. • 3-dimensional virtual reality model browser.
After the interface and the method to deliver information to users have been determined,
the basic functionalities of the D4S tool can be shown, as in Figure 3-6. The process of checking
a building model for non-compliances includes the following steps. First, the user imports the
building model into the rule checker. Then the 3D view can be shown on the right hand side of
this application tool. The navigation functions usually include Zoom, Spin and Walkthrough. On
the left hand side there are checkboxes which are used to select objects and rule sets. The user
could get detailed properties of any object by selecting an object tab. The user also can access all
design for construction safety suggestions by selecting them on rule sets. A detailed explanation
of every suggested design provision will be provided and some graphs will also be given to
illustrate complex issues. Next, the user can select the rules that will be used to check specific
objects against. After running the checking function, two sets of results will be produced. One is
a list of all non-compliance issues identified in the drawings, along with suggestions about how
to eliminate or mitigate these issues. The user could print the report in PDF or other forms.
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Another set of results will be shown on the right hand side in the form of a 3D view. Red circles
will show all the components which violate certain rule sets. After getting the report from the
model checker, the user can change drawings in the architectural designing tools or keep the
original design ideas if other requirements need to be met. Designers will be advised to keep a
record of their decisions for future use. Figure 3-3 demonstrates basic functionalities of a D4S
software tool.
Figure 3-3. Functionality of the D4S software tool
Platform Chosen
After the discussion of the architecture and functionality of the potential model checking
system, appropriate software platforms were selected. The computable rules/rule sets were then
developed based on these platforms or building model servers.
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Several software tools were examined to find the appropriate ones to be used as the
fundamental platforms of the D4S software tool. Only a few of them meet the requirements
discussed in the last section. The major difficulty was that the 3D model checking technology
was still a very advanced research area with a limited number of commercial software
applications specifically developed for this purpose. In addition, the few successful software
platforms were developed and owned by industry companies. These companies applied for
patents of their technologies and hardly any publications were released for reference.
Fortunately, some free BIM servers possessed the model query function, which uses
programming language to filter building models to retrieve useful information. Four BIM servers
were used in this research study as the software platform.
Programming languages have to be used to effectively query information from building
models stored in different kinds of database formats. For the purposes of this research study, the
software platforms were classified into three types based on how friendly they were in regard to
their user interfaces used to compile D4S suggestions into computable rules.
In the first type of software platform, the database can be queried by directly using a
programming language. The obvious advantage of this kind of platform is its flexibility. Each
suggestion/best practice can be compiled into computable rules by manually encoding
programming codes. Many engineers in the AEC domain do not have the expertise to work with
the programming languages because the language syntax usually is not immediately recognizable
to non-programmers. Therefore, a large amount of training is needed to prepare engineers to be
competent computable rule writers or users. The open source software tool BIMserver belongs to
this type. The computable rule compilers need to understand two programming languages --
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EXPRESS and Java schema to effectively query build models. This cross disciplinary
collaboration is often required to successfully complete such a project.
The second kind of software platform was developed to solve this problem by simplifying
communications for users with limited programming knowledge. These platforms adopt a user-
friendly code builder or code editor, which reduces the amount of unfamiliar syntax the
engineers have to address. The Solibri Model Checker and bimServices belong to this type.
BIMserver was also developing a generic sequence-finder to facilitate the code programming
process. An attempt was made to access the code builder of bimServices, but they could not
provide any information.
The third type of the platform adopted the natural language interface, which means that the
user could enter the constraints in plain conversational language directly into the system. The
constraint parsing process is much more difficult to fulfill. Currently, only a small portion of the
rules can be successfully transferred in this way. No software of this kind was used as the
platform for a D4S tool in this research study.
Figure 3-4 shows these three types of platforms and their subtypes. The classification of
these subtypes is based on the schema of the exported building model and the programming
language used to query these data. The building model actually can be treated as a database. It
stores all the information of a 3D building. A model checking software uses model query
language to retrieve certain information in which the user is interested. The information of a
building model can be exported into many different kinds of formats. Two kinds of database
were used in this study. The first one is a relational database such as Microsoft ACCESS and
Microsoft Excel. Structured Query Language (SQL) was used to query this kind of database. The
second one is in IFC/IFCXML schema.
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Figure 3-4. Querying BIM model/database with different programming languages and derived
platforms/servers
Data Saved in a Relational Database
The first software considered as a potential platform was MS Access, because it is very
popular software and is easy to use for most of engineers. The Autodesk Revit series provides
several exporting mechanisms, and the relational database is one of them. Other formats include
IFC, Relational Database, DWG, etc. Some of them were found not suitable for storing
geometric information, which means that they cannot be used for a querying task. For instance,
the DWG and gbXML are two document formats that do not function very well with the
semantic query.
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To export a building model from the Revit for model checking purpose, the first viable
option was exporting the information into a relational database, such as MS Access, by using
Microsoft Open Database Connectivity (ODBC). The relational database management system
(RDBMS) is a database management system based on relational models. The data are stored in
the form of tables and the relationships among the data are also stored in the form of tables. It is
the most basic and popular database system in the software industry. Many software
applications, either commercial or open source, are developed based on the relational database
model.
In this research study, a 3-D building model was prepared and exported into an MS Access
document to examine the validity of information stored in such a database. Figure 3-5 shows that
the exported file from Revit Architecture contains a set of tables. Many basic building
components (as well as their properties) of a typical building model are included in these tables.
Figure 3-5. Building features in a relational database
In a single table labeled Windows, the information for all windows and their ID, Level and
SillHeight were listed. The bottom elevation of a wall opening can be identified by checking the
height of its window sill. Before glass is put into a window opening, this opening presents a
serious hazard on a construction site, especially when window sill is less than 39 inches in
height. Window sills at this height will act as guardrails during construction. Then the Structured
Query Language (SQL) was adopted to query this database. SQL is the most extensively used
programming language to manipulate the MS Access database.
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The second method adopted to export attributes from a building model to a relational
database was using software tools such as IFC File Analyzer (IFA). The IFA used IFCsvr to
parse an IFC file and stored all the information in a MS Excel document.
The IFA generates a spreadsheet from an IFC file. A worksheet in the spreadsheet is
created for each type of IFC entity in the file. Every row in the worksheet contains the attributes
of an IFC entity. Figure 3-6 shows a summary worksheet created by the IFA software tool.
However, this method was not adopted in this study because of the severe information loss
during the format transfer process.
Figure 3-6. Worksheet created by the IFA
Data in IFC/Ifcxml Schema
The second option is to export a building model into IFC format. The IFC specification
was defined by Standard for the Exchange of Product model data (STEP) technologies and was
published as an open ISO-10303 standard. Compared to the other exporting schema, the IFC file
contains more spatial relationship information; however, it also has the most complex schema.
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Properties are often not directly attached to building components, but are related through long
indirect identification references (IDRef).
Consider checking the height of a window sill as an example. To find the sill_height of the
subject window, the relationship between this window and the attached wall must be clarified.
The IDRef of four related entities needs to be traced to link this IfcWindow to an IfcWall. Figure
3-7 shows the linkage between the IfcWindow to IfcWall with the HelloWall example, which
was developed by buildingSMART for tutoring purposes. The HelloWall example can be found
at the website of buildingSMART at http://buildingsmart-tech.org/implementation/get-
started/hello-world/example-1.
To clarify the connections between different IFC entities, a software tool IfcQuickBrowser
was used to display IFC files in a tree structure. The function of this software tool was that, when
selecting an item in the top window, all entities referring to this item (inverse references) were
displayed in the bottom window.
The path in Figure 3-7 can be simplified into “IfcWindow → IfcRelFillsElement →
IfcOpeningElement → IfcRelVoidsElement → IfcWallStandardCase”. The IfcOpeningElement
had an IfcRelVoidsElement relationship to the wall, indicating that the opening was subtracted
from the wall. The IfcWindow had an IfcRelFillsElement relationship to the opening, indicating
that the opening was to be filled with the window.
Even through IdRef, not all entities’ properties and special relationships can be directly
found in an IFC file. There were a large number of properties and relationships that were not
explicitly attached to entities. This information must be derived by analyzing other explicit IFC
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relationships.
Figure 3-7. Linking the IfcWindow to IfcWall in HelloWall example
For example, after linking the IfcWindow to IfcWall, it was found that the sill height does
not exist in some IFC files or is not supported by the dictionary of certain model checking
software. To get the value of this property, the term internal_sill_height needed to be calculated
by using the following equation:
get_sillheight(aWindow) - get_floorheight(get_floor(aWindow)).
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To compile any D4S best practice into a computable rule, the first step was analyzing how
objects were linked with different attributes and relationships. A solid understanding of the IFC
schema and its hierarchy was necessary to do this work and to successfully extract information
from building models. This task was often extremely difficult and time-consuming because of
the large size and complex schema of IFC.
The complexity of the EXPRESS language and IFC schema makes deriving component
properties directly from an IFC file a formidable task even for many programmers. Therefore
some software developers turned to the more popular XML schema and developed software
prototypes based on ifcXML. The ifcXML schema is a derivation from the Express schema
which is richer. It is the corresponding Extensible Markup Language (XML) schema of the IFC
schema. Several software platforms based on different types of XML parsers were examined to
validate their function for code checking. BimServices, one of the platforms used in this research
study belongs to this type. It was originally developed by AEC3 for the United States Army
Corps of Engineers ERDC. It was a suite of command line utilities using the TNO IfcEngine,
which was also adopted as the core of BIMserver.
Data in Other XML Schema
Because of the implicitness of many spatial relationships, the original ifcXML file is still
too complicated to query even for the most basic building components. For instance, it needs to
relate five elements through IDRefs to identify a single opening relationship between a door and
a wall, while four elements to attach simple properties such as a dimension or ‘is external’ to a
wall. This is very similar to the IFC schema because they are closely related to each other. To
solve this problem, the ifcXML file can be further simplified by transferring it to other XML
related formats. Like transferring information from IFC to ifcXML, some geometric and
topological information is lost during the transfer of ifcXML into another XML format. The loss
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of data when they are transferred between different schemas is ‘Information Lost’, which is
illustrated by Figure 3-8. Sometimes this information loss is acceptable, because the purpose and
the targeted query objects decide whether the transfer processes are suitable or not. If all the lost
information is redundant and not related to the subsequent compliance checking work, this
transfer is tolerable since all the useful information is kept. On the other hand, the data transfer is
unacceptable if any information of interest is lost during the transfer process.
Figure 3-8. Information lost during data transfer process
From the above figure, it is obvious that IFC schema provides the most information that is
necessary to derive construction features. It includes all objects and most of their properties,
relationships, and location information. Sometime ifcXML is used to substitute IFC in some
circumstances because of the complexity of STEP technology and EXPRESS language which
define the IFC schema. The mapping to the XML schema definition necessarily loses some
constraints including rules, inverse relationships and derived attributes, so certain special
relationships cannot be queried during the following period. Transferring ifcXML into other
XML schema usually causes further loss of information. The software platforms in this kind
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were closely examined and found that they were not suitable for developing the D4S software
tool because of the severe information loss.
Structuring the Rule Source
In the previous section, three kinds of software platforms that can be used as model
checking software were discussed. After selecting the appropriate software tools as the hosting
platforms, the design for construction safety suggestions were compiled into computable rules
based on the requirement of these platforms. To create computable rules, either spatial-based
query or semantic-based query can be used. While Borrmann and Rank proposed the spatial
query in 2010, most of the computable rules were based on the semantic query method. The
spatial query concerns the topological and geometrical properties of building models and
comprise of metric, directional and topological operators. These properties or relationships are
explicitly available in the building models, so the 3D model must be analyzed to acquire the
necessary data. The semantic query, however, uses information predefined in the building
models, which includes properties of BIM entities and/or relationships between them.
Semantic ambiguity was a common problem for the semantic query. The different terms
may relate to the same entities. On the other hand, several entities may share the same
terminology. The usage of dictionary, taxonomy, and ontology significantly improves the
situation. A ‘Dictionary’ defines vocabularies, terms and definitions. The Dictionary can make
sure that the property is always assigned the same meaning and unit of measurement. It is also
helpful to avoid uncontrolled expansion of the concepts. There were two options to establish a
dictionary. One was to constrain the terms used from a dictionary based on the buildingSMART
IFD (ISO 12006-3) efforts. Another option is to constrain the terms used from a dictionary based
on RDF/OWL ontology. The IFD library is an open library. The terms and concepts are defined,
semantically described and given a unique identification number (GUID).The IFD works with
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Industry Foundation Classes (IFC) and makes information exchange possible. The IFC
constrains the format for information exchange, and IFD defines a standardized understanding of
commonly used information. The relationship between IFD and IFC is shown in Figure 3-9
together with a third component, IDM, which is used to form a completely interoperable
information system. The IDM is a specification of which information to exchange and when to
exchange that information. It works with IFC and IFD to fulfill the information exchange.
Figure 3-9. Interoperability through ISO standards
Among the software platforms selected for developing the D4S software tool, the
dictionaries of BIMserver and BimServices were easily accessible to users or software
developers because the BIMserver is an open source software tool. BimServices also allowed for
the addition of new terminologies into its dictionary in support of this research. It was found that
the dictionary of BIMserver defines nearly 1,000 IFC terms. The specification of every term is
saved in a separate java format document. These specifications were originally defined by
buildingSMART International. The developer of BIMserver compiled them to fit the usage of a
BIM server. When executing the querying function, the server needs to first import all the terms
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by using the code ‘import org.bimserver.ifc.emf.Ifc2x3.*’. Even though this dictionary was
already very comprehensive, the users were still allowed to modify or even add new
specifications into the dictionary based on their needs.
Creation of Rule Sets
The IFC schema and IFD library provide the foundations for exchanging and sharing
information between different software applications. In this stage, the design for construction
safety suggestions were compiled into computable rules based on the four platforms selected in
the previous section.
Rule Sets Based on Relational Database
To manipulate and extract the data stored in a relational database such as MS Access 2007,
the Structured Query Language (SQL) was used. For example, consider the D4S suggestion
“Design window sills to be 42 inches minimum above the floor level”. The non-compliances can
be found through the following steps:
Step 1. Exported a building model into MS Access 2007 by using the Microsoft Open
Database Connectivity (ODBC) option which was provided by Revit architecture software. The
exported data include project parameters that have been assigned to different element categories
in the original building models. For each element category, Revit architecture exports a database
table for model types and another table for model instances with assigned values. For example,
Figure 3-10 shows a table listing all window types and there are 17 types of windows indicated
in the column ‘TypeMark’. The first column ‘Id’ lists the primary keys of all 17 types of
windows. Another table listing all window instances is shown in Figure 3-13. Note that ‘ODBC
exports’ presents metric units only. The Revit architecture adds relationships to the data tables
using primary keys and reference values. A primary key in each element table is the column
labeled ‘Id’. The number is the unique identifier for each instance or occurrence of a window.
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Figure 3-10. Table listing window types
Step 2. In the ‘Floors’ view, the ‘Floors’ were listed based on ‘Level’ values. In this case,
floor-20877 had the lowest elevation level value of 30, so it was recognized as being the lowest
or the first floor. This can be verified by the ‘levels’ table which is shown in Figure 3-11. There
are five levels of the subject building model. The first level has ‘Id’ value 30. After identifying
the first floor, the floor numbers were assigned to all other floors based on their level value as
shown in Figure 3-12.
Figure 3-11. Table listing levels
Figure 3-12. Sequencing floor levels based on ‘Level’ value in ‘Floors’ spreadsheet
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Step 3. In the ‘Windows’ view, all ‘Windows’ which were located above the first floor are
isolated. In this case, windows with level value over 30 were screened out.
Figure 3-13. All windows above the first floor in ‘Windows’ Spreadsheet
Step 4. In the ‘Windows’ view, comparing windows’ ‘SillHeight’ to the minimum
requirement, 42 inches or 1.0668 meter.
Figure 3-14. Filtering windows by SillHeight
Step 5. In the ‘Windows’ view, windows’ IDs of all non-compliant windows and their
floor numbers were returned as checking results. The retrieved windows’ IDs were sequenced by
floor level as shown in Figure 3-15.
Figure 3-15. The returned result of non-compliance
Rule Sets Based on BIMserver
An IFC model server is a database management system that centrally stores the building
information model and manages all access to it. Various parties involved in a construction
project can share information through it. The URL bimserver.org is linked to an open source IFC
model server project and plays a role as an information hub that allows users to merge, filter,
query, or even conduct clash detection.
From the collected falls prevention best practices, the following provision was selected to
locate the method of how to compile a computable rule based on BIMserver: ‘Locate the
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floor/roof opening which area value is larger than 4 square feet’. Openings in structures on
construction sites are a major causation for falls from elevation. During construction, elevator
shafts, skylights and stairs can all appear as openings in the floor slab. Windows and doors are
also closely related to openings in that they are normally inserted in to an IfcOpeningElement
using the IfcRelFillsElement relationship.
The opening element represents a void within any element that has a physical
manifestation. It stands for opening, recess or chase, and can be inserted into walls, slabs, beams,
columns, or other elements. The IFC specification provides two entities for opening elements.
IfcOpeningStandardCase is used for all openings that have a constant profile along a linear
extrusion. Another entity, IfcOpeningElement, is used for all other occurrences of openings and
in particular also for niches or recesses. The second entity, IfcOpeningElement, is used in this
research study.
In this research study, two methods were proposed to query an IFC file through the
‘Advanced Queries’ function of BIMserver. The purpose of this direct method was to retrieve the
area value using the semantic information already stored in the model. The indirect method
searches for the geometric parameters of the opening elements, and obtains the area value
through further calculations.
Direct approach
The quantities relating to an IfcOpeningElement are defined by the IfcElementQuantity
and are attached to the IfcRelDefinesByProperties. One quantity defined by the IFC specification
is the NominalArea, area of an opening as viewed by an elevation view for wall openings or as
viewed by a ground floor view for floor openings. First, the NominalArea is used to query the
area value of an IfcOpeningElement. The hierarchy graph shown in Figure 3-16 shows the
relationship between an IfcOpeningElement and its area value. Figure 3-16 shows that the
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IfcSlab and IfcOpeningElement are two separate entities. These two entities have to be first
linked to locate each IfcOpeningElement in the floor slab.
Then the relationship between IfcOpeningElement and its area value is found. This was
one of the most difficult steps because the IfcQuantityArea is separately stored from the
IfcOpeningElement. At this point, the specifications of all the IFC 2×3 terms defined by the
BIMserver dictionary become critical resources to understand and establish these relationships.
Figure 3-16. IFC hierarchy for opening area value retrieval
After validating the linkage between an IfcOpeningElement and its area value, the
following approach was proposed to query the area value of openings:
Step 1. Load the building stories.
Step 2. For every storey, get the IfcProduct and check the instance as IfcSlab.
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Step 3. Using RelVoidsElement, get the related IfcFeatureElementSubtraction for the IfcSlabs
Step 4. Use the information from step 3 and the IfcRelDefines to obtain the IfcPropertySetDefintion collection.
Step 5. Check for the IfcElementQuantity instance in the collection from Step 4.
Step 6. Using the IfcElementQuantity in step 5, get the IfcPhysicalQuantity.
Step 7. Typecast the IfcPhysicalQuantity to IfcQuanityArea to get the required Area Value for consideration.
This approach directly queries the area value of an IfcOpeningElement, which means that the
quantities are not obtained by calculating the geometric information of the opening element.
Indirect approach
Besides directly accessing the area value by using IfcQuantityArea, the area value of an
IfcOpeningElement can be calculated by using its dimension parameters. The second approach
was proposed to indirectly get the area value of an IfcOpeningElement. As shown in Figure 3-17,
the IfcRectangleProfileDef contains the YDim and XDim of a rectangular opening. The
IfcRectangleProfileDef.YDim is the opening width, and the IfcRectangleProfileDef.XDim is the
opening height. IfcAxis2Placement3D is used to locate and originate an object in three
dimensional space and to define a placement coordinate system.
Figure 3-17. Dimension parameters of an IfcOpeningElement
The IFC R2.0 Object Diagram developed by the Building Lifecycle Interoperable Software
Project (BLIS Project) was a helpful tool at the beginning stage of this process. It shows that the
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area value can be obtained by using the geometric dimension of an entity. With the progress of
the project, the IFC R2.0 Object Diagram – IfcOpeningElement was found to not represent the
correct relationships between an IfcOpeningElement and its IfcRectangleProfileDef because the
IFC schema had been updated from the old IFC R2.0 to the new IFC 2×3. A new diagram based
on IFC 2×3was then developed to replace the old one. Figure 3-18 shows a partial hierarchy and
attributes of an opening element. The full object diagram was more complicated, so only
relationships that were useful for querying purposes are demonstrated here. The geometric
relationships between an opening element and its dimension parameters can be derived from this
diagram. The definitions of all these terms were confirmed by documentations of International
Alliance for Interoperability (IAI), which can be obtained from the buildingSMART alliance
website http://www.buildingsmart-tech.org/ifc/IFC2x3.
In Figure 3-18, the IfcLocalPlacement defines the local coordinate system, which is
referenced by all geometric representations. The relative placement of an opening element to the
IfcWall and IfcSlab is recorded through it. The IfcProductDefinitionShape defines all shape
relevant information about an IfcProduct. It allows for multiple geometric shape representations
of the same product. The IfcShapeRepresentation represents the concept of a particular
geometric representation of a product or a product component within a specific geometric
representation context. It has an inherited attribute RepresentationType to define the geometric
model used for the shape representation. The swept area solid is a predefined type of
RepresentationType. It can be created through either an extrusion or a revolution. The
IfcExtrudedAreaSolid is defined by sweeping a bounded planar surface. It defines the extrusion
of a 2D area by using the direction and depth. A 2D area is given by a profile definition. The
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opening element extrusion segments may have any profile. Three profiles are supported by IFC
2×3. They are IfcRectangleProfileDef, IfcCircleProfileDef and IfcArbitraryClosedProfileDef.
Figure 3-18. IFC 2×3 object diagram – IfcOpeningElement
The IFC rectangle profile is the most common profile of an IfcOpeningElement. It defines
a rectangle as the profile definition used by the swept surface geometry or the swept area solid.
In IFC 2×3, rectangles are defined centric, which means the placement location has to be set with
IfcCartesianPoint (XDim/2, YDim/2) as shown in Figure 3-19.
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Figure 3-19. Parameters of rectangle profile definition
The indirect approach can be realized through the following steps:
Step 1. Load the building stories.
Step 2. For every storey, get the IfcProduct and check the instance as IfcSlab.
Step 3. If the instance is an IfcSlab, get its generalized parent object IfcElement.
Step 4. Using IfcElement, check to determine if the object has any opening elements using getHasOpenings() which will be a relationship IfcRelVoidsElement.
Step 5. Collect the IfcOpeningElement into a set from the relationship class IfcRelVoidsElement using getRelatedOpeningElement().
Step 6. The IfcOpeningElements searched for are rectangular opening elements along with their respective area values.
Step 7. Iterate the collection of IfcOpeningElements, to get the X Dimension and Y Dimension values to calculate the area as follows.
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Step 8. The objective is to find the path: IfcOpeningElement → IfcExtrudedAreaSolid → IfcRectangleProfileDef for the methods getXDim() & getYDim().
Step 9. Get the IfcRepresentation and iterate over them to find the IfcShapeRepresentation which will return the items of IfcExtrudedAreaSolid.
Step 10. IfcExtrudedAreaSolid has the profile definition among which IfcRectangleProfileDef is defined.
Step 11. Check for the instance of IfcRectangleProfileDef to invoke the getXDim() and getYDim().
Step 12. Calculate the area as a product of the return values of the above dimension methods.
Step 13. Filtering the IfcOpeningElement using the search area criteria.
Rule Sets Based on Solibri Model Checker
A large number of default building codes have already been included in the Ruleset
Folders and Ruleset Library as part of Solibri Model Checker (SMC). The users can adjust rule
parameters to make these pre-set rules fit their needs. These rule sets are compiled in java using
the SMC application programming interface (API), which is not publicly available. With the
Ruleset Manager, the user still can create and edit some new rules. For example, the computable
rule which checks the window sill height was compiled with “General Purpose Property Rule”
template. To compile this rule, the user interface was switched to the Ruleset Manager, which is
shown in the Figure 3-20. The Ruleset Manager has five “Views”. They are Rule Set Folders,
Libraries, Info, Workspace, and Parameters. The Ruleset Folders View on the left side of the
window shows all the available rule sets saved on the hard disk. These rules sets are kept in
several Ruleset Folders based on their disciplines. The user can upload any of these rule sets and
conduct corresponding rule checks. On the right side of the window, the Libraries View shows
all basic computable rule templates which can be edited based on the user’s need.
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Figure 3-20. The Rule Set Manager interface for browsing and editing rules
In the Libraries View, Figure 3-21, the “General Purpose Property Rule” was selected. The
description of this rule can be found in the Info View. This rule was designed to check any
combination of properties of a given component type. Then the users can add this template into
the Workspace View and configure the rule parameters in the Parameter View.
In the Parameter View, which is shown in the Figure 3-23, one discipline was selected to
make sure that only components in this specified discipline will be checked. In the Property
Value Rules table, the “Window” was selected as the component type to be checked. The
property to be checked was the “Bottom Elevation”. Usually there are several numerical
properties that can be checked, which depend on the selected component type. The operator
selected here was “At least”, and the value was set to 42 inches. By using the “Type” column,
certain construction types can be selected to limit the model checking. For instance, when
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checking the openings size in a building model, the user may only want to check the openings
located on the building roof, so the roof can be set in the type column to limit the checking
scope. After configuring Property Value Rules, the user can impress the output issues with the
Categorization Order table. For the Space Checking Options, “Check Only Spaces” was used.
Finally, the user can save the configured template as a new rule set in the Designing for
Construction Worker Safety folder.
Figure 3-21. The Libraries View
Figure 3-22. Workspace View
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Figure 3-23. Parameter View
Rule Sets Based on Bimservices
To use bimServices as the model checking software, the development of computable rules
is characterized by ‘soft coding’ which follows a pre-defined mark-up methodology (Nisbet,
2010b). The software programming for this can be done automatically or semi-automatically
based on predefined procedures. Figure 3-24 shows a general coding process based on
BimServices.
The paper based ‘Normative document’ can be encoded into IFC/ifcXML format
computable rule through a set of transformations. The first step is to transfer original D4S
suggestions into computer readable Baseline Electronic Suggestions which are in HXML format.
Then, the logical relationships between different ‘terms’ and ‘term properties’ are tagged by
marking them with different colors, which are corresponding to the SMARTcode
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Figure 3-24. Encoding D4S suggestions into safety Constraint Model
protocol. Then the marked-up text is edited into structured HTXML either manually or
automatically by using a code editor/builder. Finally, an XSLT format configuration is used to
convert marked-up XHTML into single D4S computable rule. The Transform1 function of
bimServices uses the ‘output’ setting within the XSLT file to anticipate the general output format
required. Rather than manually tagging and marking up a baseline electronic suggestion, using a
code editor is more time and cost effective. Furthermore, this enables a person skilled in the AEC
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domain to develop applicable rules without the support of programmers. The XSLT document is
still under development at this point in time.
As mentioned above, a color system was adopted to tag baseline electronic suggestions to
make the four logistic concepts apparent. Table 3-1 shows these four different mark-up colors
and their meanings.
Table 3-1. Four different mark-up colors Color Meaning Function Purple Selection What different situations does this apply to? Green Applicability What is the scope of the check? Blue Requirement What is required? Orange Exceptions What exceptions are there?
The checking of the window sill height was used as an example to show how a semantic
concept can be implemented into a computable rule and be applicable to model checking. The
logistic relationships were:
• Selection: Topic=window • Applicability: Topic=window Property=isexternal • Requirement: Topic=window Property=Internal_Sill_height • Comparator=greater than Value=42 Unit=inch
The ‘Internal_Sill_height’ was calculated by using the equation: get_sillheight(aWindow) -
get_floorheight(get_floor(aWindow)). It should also be noticed that there was one ‘Exception’ in
this provision. The windows located on the first floor were exempted from checking because the
differences between the altitude levels of window sills and exterior earth (ground) are normally
within a safe range. This discussion is an assumption because computable rules based on
bimServices have not been developed. The topographic information may not be accurately
portrayed in a BIM model so a manual check is advised.
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The Figure 3-25 shows the computable rule encoding process. At the top of the diagram is
the D4S suggestion in a normative document format. After coloring, marking-up and mapping,
the normative document can be transferred into a computer readable rule.
Figure 3-25. Sample rule of bimServices
Building Model Preparation
Besides compiling the computable rules, appropriate building models needed to be
prepared to test the effect of the tentative rules. With the rapid adoption of BIM technology in
the AEC industry, it was not difficult to find example test cases to explore the information
typically captured in IFC databases. For example, the IAI provided several links to various
examples at http://www.ifcwiki.org/index.php/Examples. The object properties and other
information of interest might be not included in a random building model. In this case, the model
checking software cannot conduct the check and return a value or term such as “UNKNOWN” to
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let the user know that certain information does not exist in the subject model. This causes an
‘uncheckable’ situation. Therefore, certain ‘rules’ need to be followed to prepare the test models.
The basic requirement of testing building model was that the model should look like a
normal building, and all targeted information must be included in it. For this research study, the
targeted information was the window sill height and the size of the floor openings. The existence
of the information can be verified by using an ‘IFC viewer’ such as IfcStoreyView, which was
developed by the Karlsruhe Institute for Technology. This software tool can be used to verify the
attribute values of most of the building components. Figure 3-26 shows the properties of an IFC
opening element reviewed by using IftStoreyView. It can be easily found from the figure that
this opening is located on the third floor and that the area value of this opening element is 78.5
square feet.
Figure 3-26. Reviewing IFC opening element properties in IfcStoreyView
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The purpose of this research was to identify and assess potential fall hazards. Two specific D4S
provisions were the focus of this research. The first provision is ‘Design window sills to be 42
inches minimum above the floor level’. While a 39-inch window sill height would satisfy the
OSHA requirement of fall protection, a more conservative value of 42 inches was selected as a
safer approach. The object of compliance checking is the height of the window sill. The second
provision is ‘Locate the floor/roof opening which has its smallest dimension greater than 6
inches. The objects of compliance checking are floor and roof openings. A sample model
4351.ifc was developed by using the Revit Architecture BIM authoring tool. Building model
4351 was a three story building. There were three windows and four floor openings in this
model. This can be verified by using an IFC viewer. Figure 3-27 is the front elevation of this
building model. From this graph, the three windows that are located on different stories in the
building can be easily located.
Figure 3-27. Three windows in building model 4351.ifc
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Figure 3-28 shows all the IfcOpeningElements in the model. The two large floor openings
were created by stairs. The two smaller ones were created by an elevator shaft which penetrates
the level 2 and level 3 floor slabs.
Figure 3-28. Opening elements in building model 4351.ifc
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CHAPTER 4 RESULTS
Two major results are discussed in this chapter. The first one is the positive impact that
BIM technology can potentially have on construction site safety. This consists of the changes
that will be realized by constructors that adopt BIM applications. New construction methods and
new applications could help constructors reduce injury and fatality rates by increasing the
opportunity for prefabrication, conducting clash detection, and providing virtual reality to let
construction workers become more familiar with the project.
The second result is a D4S software tool which could help designers implement the design
for construction safety concept in practice. This software tool was developed by using BIM
technology to set up a design for safety database and adopting a model checking software which
will automatically check developed building models against design for construction safety rule
sets. Particular emphasis is placed on fall hazards since falls are the most frequently occurring
causation of fatalities on construction sites.
BIM technology’s impact on construction safety
BIM technology, especially BIM applications, could help constructors reduce injury and
fatality rates in the following work areas:
• Safety Planning • Work sequencing • Construction schedule • Clash detection • Improve the construction documents quality: jointly review design decisions • Communicate design intent between trades and design discipline
Safety Planning
The development of project specific safety plans is important to the safety management for
construction projects. The safety plans assist management personnel in establishing a healthy and
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safe working environment which benefits all construction workers. The traditional safety plans
are mainly developed based on 2D drawings. With the prevalence of BIM technology, 3-D and
4-D safety planning have begun to emerge. The 3-D safety plans use virtual reality applications
and tools to help project participants get familiar with the construction site environment. 4-D
safety also becomes a necessary method because poor planning and scheduling usually causes
chaos on construction sites. A well-arranged construction schedule can positively influence
construction site safety. If the schedule of a project gets improved, the safety performance will
be improved. This can be realized by identifying risks and devising better planning control.
When project participants also consider schedule issues when they plan 3-D safety, the 3-D
safety planning evolves into the 4-D safety planning.
3D/Virtual Reality
Designs are becoming more and more complex, and few people on construction sites can
readily read and understand the complex drawings. Many construction requirements rely on
person-to-person instruction. During this process, errors occur when reading drawings,
interpreting them and passing on the information. By using BIM applications, constructors could
pre-build the project in model form far in advance of actual construction. Construction workers
could become familiar with the proposed building structures by viewing 3D walkthroughs which
simulate the view from the perspective of a human who is walking through the facility. With the
development of the virtual reality (VR) technology in recent years, VR laboratoties have been
developed which can be used as VR safety –training systems. Figure 4-1 is a photograph of a
BIM computer lab at the Center for Advanced Construction Information Modeling at the
University of Florida. These advanced 3-D virtual reality devices were set up for tutorial and
training purposes. Students and AEC professionals can learn or assess the building structure and
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internal mechanical, plumbing, electrical and fire protection (MEP/FP) systems in 3-D view
through both of the major projectors and seperately estalished workstations.
Figure 4-1. Photograph of BIM computer lab at Center for Advanced Construction Information
Modeling at the University of Florida (Photo courtesy of Jia Qi)
Schedule/4D
The project schedule undoubtedly impacts construction site safety. For instance,
construction workers tend to neglect surrounding hazards when an expedited schedule is
associated with their tasks, which compromises safety performance. In contrast, a well-organized
project reduces the pressure on construction workers and correspondingly diminishes the
occurrence of accidents. Past research studies have discussed the relationship between the work
schedule and construction site safety. It was found that safe projects and success in scheduling
are jointly achievable (Hinze 2006; Yi and Langford 2006). BIM applications enable "what-if"
scenarios to be examined by visual risk management and time-based workflow planning when
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linked with clash detection. The “what if” analysis is a structured brainstorming method which is
usually used to uncover hidden hazards. 4D models link components in 3D CAD models with
construction schedules. The 4D model allows project participants to view the planned
construction of a facility over time and review the status of a project in the context of a 3D CAD
model. In practice, constructors use 4D models to study different design and schedule
alternatives and educate workers about what would be happening during each stage of
construction.
Although the coordination between scheduling and safety planning has been identified as
an important factor to a successful project, this question has not been fully discussed under a 4-D
environment. BIM technology is being substituted for 2-D CAD technology. With the rapid
progress of BIM technology, it is necessary to propose the concept of four-dimensional-safety
(4-D-Safety). 4-D-Safety is the technology that uses 3-D software to detect the location of
construction site hazards and meanwhile uses scheduling software to identify corresponding
high-risk time periods. There are various construction hazards on construction sites during
different time periods. Since the construction site conditions vary according to the progress of
the building, the construction hazards that exist during the construction process of a building
structure will disappear with the completion of that building structure. The corresponding safety
measures must be applied for the appropriate conditions and at the right timing. This is another
difference between design for construction worker safety suggestions and building codes.
Building codes are used to protect the public and end users who will take occupancy of the
completed building. Model checking software (MCS) developed for code checking just needs to
check the as-build model to ensure that the building fulfills all the code requirements. Design for
construction worker safety protects construction workers during the entire project life-cycle.
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Model checking software developed for this purpose should be able to check the safety
conditions of a building information model at any point in time during the construction phase. By
coordinating the safety planning with scheduling in a 4-D environment, the project participants
could locate potential construction site hazards in advance and then take reasonable measures to
reduce or eliminate the hazards.
Conducting Clash Detection
Construction managers can check distances between different building components and
arrange workflow planning for time and space coordination by using applications such as
NavisWorks. On a construction site, two kinds of conflicts usually exist that can cause accidents:
the static ones and the dynamic ones. The static ones consist of conflicts between in-place
structures and other features such as idle equipment. Construction planning should be done
during the design phase to identify and to address the two kinds of undesirable conflicts. This
requires planning for sufficient space to allow construction workers to build and maintain the
building components and equipment. For example, in a boiler room, the circulator pumps are
generally designed high up near the ceiling. A worker would have to stand on a ladder to replace
the pumps, and would have to work between various piping systems to accomplish the tasks. In
this situation, maintenance workers could readily fall off the ladder, drop the pump, or suffer
some other type of injury when making contact with adjacent piping. A maintenance worker may
need to shut off a valve to work safely. Planning is also needed so that the work of different
construction specialists can be coordinated when activities must run in parallel in order to meet
schedules.
Dynamic conflicts consist of the conflicts between different work crews in the field. This
kind of conflict is usually costly in that both the project budget and the project schedule are
affected. In the past, the coordination ability of project managers was crucial to solving this kind
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of problem. The project with a competent project manager and sound management system
usually could reduce the occurrence of conflicts in the field and make projects more profitable.
Better construction site planning can be arranged by using BIM applications. Past research
validates this by showing that 83 percent of contractors as BIM application users achieve
reduced conflicts.
Increasing Prefabrication
Prefabrication could reduce injuries in two ways. First, fewer workers are needed on a
construction site, which facilitates construction site management. It is understandable that fewer
injuries will occur because more work is being performed in a more controlled environment.
Second, less work will be done at high places or at elevation, which reduces the chance of falling
injuries. While prefabrication can improve construction site safety, inconsistency, inaccuracy,
and uncertainty in design could make it difficult to fabricate materials offsite. When using 2D
drawings, architects often choose to include fewer details in their drawings. Many errors in
construction documents are produced during the design phase. These errors accumulate and are
not found until prefabricated parts are delivered to the construction site. In a manual assembly, if
a structural element is a half-inch off alignment, it may not be noticed. Components that are
added later may not fit and have to be trimmed or shimmed. The prevailing BIM architectural
design models will increase the percentage of prefabrication by producing more accurate
construction documents. Seventy seven percent of the contractors predicted that model-driven
prefabrication will be the dominant value five years from now in the survey conducted by
McGraw-Hill Construction (2009).
Other case studies (Khanzode et al., 2008) also support the above points. The Camino
Medical Office Building, for example, is one of the first project studies that quantitatively
measured the benefits of using BIM tools for MEP coordination. The labor savings ranged from
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20% to 30% for all MEP specialty contractors. In total, 203,448 field work hours were spent on
the construction project and only one recordable injury occurred (Khanzode et al., 2008). The
RIR of the MEP specialty contractors was nearly 1.02, which is far less than the industry
average. These achievements are attributed to the improved workflow due to the use of 3D/4D
models which resulted in more off-site prefabrication and efficient field installations.
When reviewing past BIM surveys and case studies, it was noticed that past research
studies could be improved. First, the lack of a comprehensive and systematic method of defining
goals and choosing among design options impedes the production of design drawings which
incorporate adequate safety considerations. Gane (2008) pointed out that “architectural criteria
(e.g., aesthetics, area efficiency, site views) prevail over engineering performance criteria (e.g.,
energy efficiency, structural performance)”. The same is true of construction safety. Safety
issues often are not an important criterion when designers make decisions. The designers also
seldom conduct safety reviews after the conceptual design to ensure that construction knowledge
is incorporated in the design phase and safety issues are minimized. To change this situation, the
concept of “making zero accidents a reality” should be propagandized in the construction
industry.
Secondly, when calculating the return on investment (ROI) of BIM, the savings related to
improved construction safety also should be considered. Furthermore, past research studies
usually have overlooked the savings caused by decreased indirect costs of construction accidents,
because it is difficult to identify and quantify the hidden costs of injuries. For instance, the ratio
of field indirect costs to direct costs is 0.85 for medical-case injuries. The reduction of both
direct and indirect costs of injuries should be considered when calculating the savings attributed
to BIM.
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Design for Construction Worker Safety Software Tool
In the last section, the application of BIM technology in the AEC domain and its benefit to
construction worker safety were discussed. In this section, the results from different model
checking software are shown.
The design process gets improved by using this “Life Cycle Safety” process. There are
several stages in the design process where the building model can be checked in some way. With
the help of a D4S application tool which can check the level of compliance with specific safety
requirements, the design review process can be further improved and construction site safety can
be enhanced.
Figure 4-2 shows the construction project life cycle after the D4S application tool has been
adopted. It also demonstrates the data flow throughout the whole project lifecycle.
Designer BIM Software
DesignerOwner IFC Files
InspectorDesigner ContractorChecking System
OSHACII UFKnowledge Based Expert System
SubsContractor OSHANew Onsite Fatality/Injuries
InspectorDesigner ContractorReport
Phase 1
Phase 3
Phase 2
Phase 4
Phase 5
Phase 6Phase 7
Figure 4-2. Construction project life cycle safety with a D4S application tool
In Phase 1, drawings are generated by various BIM design applications such as Revit and
ArchiCAD which support the export of multiple versions of IFC files. Then the IFC format file
which consists of geometric information of building components and the relationships between
them is abstracted from these design applications.
In Phase 2, design for construction worker safety suggestions are collected, classified and
compiled into computable rules in a model checking software.
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In Phase 3, a D4S application tool is developed. After the computable rules are imported to
the checking system, IFC format files can be imported into the checking system to check for
compliance, and designers can access design for construction safety knowledge of various
building components.
In Phase 4, the checking system generates both checking reports and visual graphs. Reports
list detected design errors which violate specific rules in the knowledge base. Meanwhile graphs
explicitly show building structures or building areas where design alternatives are available to
avoid construction worker injuries. These reports and graphs can help all project stakeholders by
providing them with valuable D4S information. Designers can acquire useful construction safety
knowledge and revise their drawings before delivering them to the constructors. Code officials
can evaluate the project’s drawings for code compliance, cite deficiencies and request revisions
to resolve potential problems. The constructors also can check their building models before or
during construction, and use temporary structures or PPE to diminish their employees’ exposure
to unsafe working environments.
In Phase 5, constructors finish construction work after the building models have been
checked. Two potential problems may still cause injuries and fatalities on construction sites. The
first problem is the lack of an administrative program which will ensure compliance. The second
problem is that construction workers may not adhere to safety practices. OSHA will collect
information related to new accidents and constructors also will learn considerably from those
incidents.
In Phase 6, researchers will receive feedback from industry professionals to enrich the
design for safety database.
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In Phase 7, more stakeholders of a project will be concerned about construction worker
safety after the industry safety culture has changed. This checking system will be embedded in
the BIM software as a plug-in, which makes it more accessible to users.
The entire process is a learning loop. The project participants should enrich the knowledge-
based expert system with new best practices and innovative techniques as the design is a process
in which more information is to be added as more information is gained through project
successes and failures.
This D4S application tool also helps various stakeholders involved in the work to protect
construction workers. The current situation is that the general contractor is usually expected to
review shop drawings for safety while the architect and engineer are not responsible for any
safety reviews of the shop drawings. To correct design problems before they get frozen into the
fabricated product, designers, constructors and official authorities need to be involved in the
process. By analyzing a typical project lifecycle, two groups of stakeholders are identified as the
main users of a design for construction safety tool. They are the designers and contractors.
Owners also could check designs for safety by using this tool. Figure 4-3 shows when various
project participants could address safety issues during different phases of a project lifecycle. The
black areas are phases when stakeholders should consider construction safety issues. Designers
should address safety from the proposal stage to the construction document stage. Constructors
should consider safety in construction and maintain phases. It is beneficial that owners consider
safety issues throughout the project lifecycle. The gray area is the period when constructors
could ideally cooperate with designers and incorporate construction safety knowledge into the
building design.
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Figure 4-3. Safety effort of different stakeholders in a project lifecycle
Checking Results with a Relational Database
As discussed in Chapter 3, a building model can be exported and saved in a relational
database such as MS Access. The Structured Query Language (SQL) could then be used to query
this database. Here the detailed checking process using MS Access 2007 is given. The D4S rule
used is “Design window sills to be 42 inches minimum above the floor level”.
Step 1. Launch MS Access 2007and open the database that will be queried. In this case,
model 4321.ifc is used.
Step 2. Select Query Design in the Create window to create a new object query. Then
select SQL View in Design View to display the Query window. The user interface is shown in
Figure 4-4.
Step 3. Type the compiled SQL statement in the Query window. This step is shown in
Figure 4-5.
Step 4. Click the Run button to execute the SQL statement, and the result is shown in
Figure 4-6.
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Figure 4-4. Model checking in a Microsoft Access
Figure 4-5. Import computable rule in the Query window
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Figure 4-6. Model checking result in a Microsoft Access
Besides querying a relational database directly with SQL and VBA, more complex model
servers can be developed based on either a relational database or other kinds of storage methods.
These model servers can provide query access to the model using either SOAP (Simple Object
Access Protocol), XML, or Express language. Figure 4-7 shows the simplified architecture of a
multi-layered model server. At the beginning, the IFC files are imported into the database. The
database can be a relational database or other database such as Oracle Berkley DB engine which
is used in BIMserver.org project. There are different layers in an IFC model server. These layers
process data by making a simple query to the model using common language. Kiviniemi (2005)
and Beetz (2010) reviewed the model servers currently in use and the model servers that are
under development.
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Figure 4-7. The architecture of current model server and potential extension
Checking Results with BIMserver
In Chapter 3, the computable rule based on BIMserver was written using Java language
and the IFC hierarchy. The computable rules are enclosed in APPENDIX B and APPENDIX C.
To use BIMserver as the platform for compliance checking, the user first needs to login into the
server and select the project that will be checked. Here the project 4351 is selected to be under
review as shown in Figure 4-8.
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Figure 4-8. Launch BIMserver and select project to be checked
After selecting the project which the user wants to check, the BIMserver provides six
potential functions which can be executed. The Query function is used for a compliance check.
The server further provides two options: Simple Query and Advanced Query. Here the user
should select the Advanced Query option and import the computable rule in the compile
window. This user interface is shown in Figure 4-9.
Figure 4-9. User interface of Advance Query function of BIMServer
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There are two buttons at the bottom right of the user interface. The ‘Compile’ function
automatically checks the validity of the computable rule. It reports the grammar errors if the
imported rule is wrong. The ‘Compile & Run’ function checks errors as ‘Compile’ function and
executes code checking if the imported rule is well written. Here the computable rule is compiled
using the direct approach is first imported and executed. The result of the check is shown in
Figure 4-10.
Figure 4-10. Checking area values of opening elements with BIMserver by using computable rule written in direct approach
Figure 4-10 shows that there are a total of four opening elements in project 4351. This
matches the number of IFC opening elements in the original building model. The retrieved area
values mismatch the true values in the original model. After further validation, it was found that
the retrieved values were the ‘net area value’ of the slabs to which opening elements are
attached. The relationship between the net area value, slab area value and opening element area
value can be linked using the following equation:
Slab area value ̶ Opening area value = Net area value of slab
This relationship is shown in Figure 4-11. Area A is the slab area value, and area B in
white color is a slab opening element. The net area value of the slab is marked in orange color.
Even though the retrieved values are not the area values of opening elements, this does not mean
the direct approach that uses semantic information in the model is wrong. The direct method is
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still a generic method to query an IFC building model when using BIMserver. It may not work in
a few specific circumstances, such as the unusual storage of certain semantic information.
Figure 4-11. The relationship between net area value and opening element area value
The validity of a computable rule written in the indirect approach is checked. The direct
method retrieves the area value using the semantic information already stored in the model. The
indirect method tried to find geometric parameters of opening elements, and obtained the area
value through further calculations. The rule is imported into the query window in the same way
as the rule is compiled in the direct approach. After running the check, the result is shown in
Figure 4-12. The X dimensions, Y dimensions, and area values of all three opening elements in
the rectangular shape are listed. These values match the area value in the origional building
model.
Figure 4-12. Checking area values of opening elements with BIMserver by using computable
rule written in direct approach
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Checking Results with Solibri Model Checker
The building model is exported into an IFC file after being created in a BIM authoring
software such as Autodesk architecture. The model is opened in the Solibri Model Checker
(SMC), ready to be explored and checked. The model checking layout of SMC consists of four
functional sub-windows. Necessary operations to conduct the model checking are realized
through them. They are:
• Rule sets. When the developed computable rules are loaded into the model checking software, they are called “rules sets” in SMC. Users could select rules that will be used to check the model.
• Results View. Noncompliance will be shown in this window.
• 3-Dimensional virtual reality model browser.
• Info View. This description window shows the detailed explanations of the selected safety suggestion.
Figure 4-13 shows functional and informational views which compose the user interface.
Figure 4-13. Checking layout of Solibri Model Checker
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Rule execution/Rule check reporting. Three major steps – Navigation, Rule execution,
and Rule check reporting -- are needed when using this system to check for non-compliance. The
‘Navigation’ function can be activated by selecting the Model Tree tab, which can be expanded
or collapsed to show the components of the subject building. Users can get familiar with the
building model by exploring it. This progress is shown in Figure 4-14.
Figure 4-14. Using the model tree navigates the subject building model
After the users are acquainted with the structure of the subject building, they can load the
design for construction safety rule sets to start checking the building model. The available rule
sets/constraint model is listed at the left side of the interface. Figure 4-15 shows the interface
after adding the rule sets.
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Figure 4-15. Selecting desired constraint model / rule set
After loading the desired rule sets/constraint model, the user can initiate the checking
process by clicking on the Check icon. All non-compliances are reported as checking results. The
checking results will be displayed in the results view, showing whether a specific safety rule has
been satisfied or not. The user could click a single checking result to locate the problem in the
right side 3D view. Meanwhile, the detailed explanation of violated rules can be seen in the
description window. Figure 4-16 shows the user interface after running the checking function.
From the picture there are two windows for which the sill height is lower than the pre-set value.
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Figure 4-16. Checking results
The user can select any checking result in the Result View for a further review as shown in
Figure 4-17. A detailed description of the specific violated rule will be given in the Info View.
Figure 4-17. Description of non-compliance in the Info View
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The Info View can show the user more comprehensive information of the problematic
entity as shown in Figure 4-18. Here the Sill Height of the window is 3 feet, and the window is
located on the second floor. Other PSet_Revit values also can be found from the Info View.
Figure 4-18. The PSet_Revit properties in Info View
Sometimes even though an object violates the design for safety rules, the user might
consider whether some action is needed. It is possible that the violation does not pose a serious
hazard on the construction site, or that other more important rules overpower this one, so the user
might elect to overlook the non-compliance. The ‘Checking Decision’ setting in the ‘Result
Details’ view makes this function possible, which is shown in Figure 4-19. For every identified
non-compliance, the user can decide whether to accept or reject the checking result. If the user
selects the ‘Accepted’ option, the model checking tool will neglect this violation as shown in
Figure 4-20. If the ‘Rejected’ option is selected, this violation will be ear-marked for future
reference.
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Figure 4-19. Result Details view
Figure 4-20. Neglecting the non-compliance after selecting the ‘Accepted’ Option
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A non-compliance report can be created by exporting checking results in PDF, XLS or
XML format. This function makes it is much easier for users to save the checking result for
future usage or share it with other project participants. Figure 4-21 shows the ‘Create Report’
setting of the software tool. The report content and report type can be set through this dialog box.
Figure 4-21. Create report
After finding the non-compliance elements in the subject building model, the project
participants need to decide the appropriate actions, if any, to be taken to address the problems.
The designers could change the building model to make it safer. For example, Figure 4-20, the
safety checking system reports that a window does not conform to the loaded Rule Set. The Info
View also gives a D4S suggestion: ‘Design window sills to be 42 inches minimum above the
floor level.’ The designer could go back to the BIM authoring tool to correct the height of the
window sill. In Figure 4-22 it is evident that, in the authoring tool, the current height of window
sill is 12 inches, which does not meet the safety requirement. The designer should make a change
to the building model to satisfy the minimum requirement.
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The constructor also could take steps on the construction site to eliminate fall hazards.
After finding that the opening in the exterior wall is a potential hazard on the construction site,
the constructor can either negotiate with architects to change the parameter (window sill height)
or install temporary fall protection.
Figure 4-22. Instance properties in BIM authoring tool
After changing the sill height of the window on the second floor in the building design
tool, the user can run the model checking software to check the building model for validation.
Figure 4-23 shows the window on the first floor still does not meet the D4S requirement. This
might be acceptable if the elevation difference between the interior window sill and the exterior
topography does not seriously violate the requirement.
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Figure 4-23. New result of the check after changing the dimension of certain objects
The same procedure can be used to find all floor openings for which the area values violate
the minimum rule of being less than 4 square feet. For model 5351.ifc, it is found that all four
floor openings do not satisfy the requirement. This result of the D4S check is shown in Figure 4-
24. In the result view, four non-compliant openings and their area values are given. In the
navigation view, these non-compliances are clearly marked with red color. Other structural parts
in the same building are shaded to half transparent, so that the user can better recognize the
relative positions.
The user can also select any non-compliance in the result view, and a detailed description
is then given in the bottom info view. Meanwhile, the 3-D view zooms in to the selected non-
compliance, so the user can have a closer review as shown in Figure 4-25.
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Figure 4-24. Result of checking for slab openings
Figure 4-25. Designing alternative given in Info View
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CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS
Conclusions
As designs increase in complexity, it is expected that construction worker safety will
become more and more important during the design phase. Through the review of the literature,
it is evident that Building Information Modeling (BIM) as a tool can be used to address
construction safety. By adopting this new computer technology, safety performance is expected
to improve by increasing the opportunity for prefabrication, conducting clash detection, and
providing virtual reality to help train construction workers to be more familiar with the project.
D4S computable rules are developed based on different software platforms. These
application tools can be used to automatically check for fall hazards in 3D building models and
provide design alternatives to users. They can be used by architects/engineers during the design
process or by constructors before commencing construction work. For instance, engineers can
use the D4S application tool to check project models to identify the opportunities for integrating
safety into the building models during the design process, obviating the need for constructors to
address certain safety measures on-site. If engineers failed to do that, constructors could use the
software to check for potential hazards which were not eliminated when designing the permanent
structure. The constructors would know when and where they should initiate measures to address
hazards by using certain temporary structures to protect the construction workers.
Four application tools are proposed as platforms for compliance checking. They are MS
Access, BIMserver, Solibri Model Checker, and BimServices. The research results showed that a
relational database and its related software, such as MS Access and MS Excel, can be used for
simple code checking. The Construction Operations Building Information Exchange (COBie)
project, which was undertaken by the Engineer Research and Development Center (ERDC), also
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verified that building structural information can be exported from an IFC document to an MS
Excel document. Compliance checking can be conducted based on this COBie format. Therefore,
the construction worker safety issue can be addressed with the same approach. The benefit of
using an IFC File Analyzer or other software tools to export building information into a
relational database is that the user can view all component attributes at once rather than drilling
down to values for an individual entity. Sometimes this functionality is more effective and
convenient.
A current challenge is that there is no specific software tool that has been developed to
extract construction safety related structural information out of a building model. This limits the
effect of code querying with a relational database. The COBie format has been developed
primarily for Facility Management (FM) purposes. It is difficult to propagate compliance
checking using a relational database until a similar application tool is developed to export safety
related information out of the building models.
From the results of the D4S check shown in the Chapter 4, it was found that the three other
software platforms are all powerful tools for code checking. Even though all of them can conduct
compliance checking very well, each of them still has its own characteristics when it comes to
computable rule compiling. The advantages and disadvantages for rule writing are listed in Table
5-1.
For Solibri Model Check, the ‘Ruleset Manager’ is used for writing the computable rule.
The Ruleset manager has a user friendly interface. The default rule library also provides several
rule templates. If a D4S suggestion could fit with any provided template, the rule compiling
process becomes fairly easy. Otherwise, a Solibri consultant can be contacted for additional
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assistance. A new computer language can be developed for rule transferring under the guidance
or permission of Solibri.
For bimServices, the computable rule can be written by either automatically editing with a
‘SMARTcode builder’ or manually adding protocols into a normative document. The
compilation of XLST files which are later used for document mapping are technically
demanding.
For BIMserver, the computable rule is written in Java language with the IFC hierarchy.
Though Java language is a popular computer language, only a few researchers/engineers are
acquainted with the IFC hierarchy prescribed under the BIMserver environment.
Table 5-1. Comparison computable rule compiling process based on three software platforms Model Checking
Software (Platform) Advantage Disadvantage
Solibri Model Checker
Friendly user interface Not an open source software
bimServices Using XML and XLST mapping makes
standardized computable rule possible
The SMARTcode builder/editor
will be released soon
Experienced programmer is needed
BIMserver Easier coding work: directly using Java
language to query the database
Limited documentation is available
Relational Database Easily allow a user to access this software
Information loss
It should be noticed that these advantages and disadvantages are all about the computable
writing process. It has nothing to do with the functionalities of these platforms. All of these
platforms provide multiple functions which are listed in Table 5-2. Besides, the above judgment
is based on the expertise of selected programmers at the University of Florida. Other entities that
want to develop their own computable rules might have different viewpoints based on the coding
experience of their programmers and resources.
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Table 5-2. Comparison of functionalities between three software platforms (Adapted from Bimservices, BIMserver, and Solibri)
With a software tool that could automatically identify safety hazards in building models,
constructors and designers need to cooperate with each other to effectively improve construction
worker safety. Currently it is mainly contractors who initiate, maintain and supervise all safety
precautions and programs because construction methods are within their realm of expertise. In
the era of BIM technology, more and more information is transferred between project
BimServices Transform: To interoperate between IFC, ifcXML and other representations such as COBIE2 and HTML. Filter: To reduce an IFC model by filtering out selected objects and relationships. Compare: To compare two IFC models from the project downwards. Compliance: To check an IFC model for compliance against regulations or code requirements.
BIMserver Merging: To merge sub-models into a base model. Revision management: To get revisions by sub-projects and main project. Change finder: To let the software find changes that were made to the model. Checkout & update warnings: To get a big warning when model inconsistencies seem to appear. Filter & Query: To enlist a specific IFC object in a model. Rules and advanced Query: To use Java code to make advanced queries or rules.
Solibri Model Checker Model checking. Merge: To merger multiple models together in a single, compressed SMC file. Clash detection: To conduct rule-based clash detection. Change finder: To compare two versions of a model and see the changes. Quantity takeoffs: To generate quantity takeoffs that can subsequently be fed to estimating applications.
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participants. This requires that constructors develop procedures for validating information
received from the other stakeholders. With the new D4S application tool, constructors can check
their building models before undertaking the construction works. They can erect warning signs
and adopt reasonable protection methods during the construction process. But from either the
construction safety or the building information perspectives, the constructors cannot substitute
for designers to incorporate D4S knowledge into designs. First, the architect/engineer’s scope of
work is to design permanent structures. If the safety hazards on a construction site have been
“built in” the project models after the initial design work, it will take considerable effort for the
constructor to remedy the deficits by using the temporary structures. From the information life
cycle perspective, in the traditional design-bid-build delivery process, the construction
documents reach the highest level of information maturity at the bid stage. After the contract is
awarded, the maturity level of the construction documents gradually declines as no more
comprehensive compilation is conducted. This is the “information content decay” theory.
Before there is legislation which requires designers to consider the construction site safety
during the design phase, in the short run, cultivating an environment of “information
stewardship” seems an opportunity to promote the idea of D4S. Smith and Tardif (2009) defined
information stewardship as a means that building industry professionals should regard the
information they create with an attitude of stewardship rather than ownership. As it is impossible
for everyone in the building industry to understand other people’s business process and to
anticipate how the information they create will be used by other people, project participants
should recognize the information they create is just a part of the whole task in the project
lifecycle. They should create and organize the information in an integrated and structured
manner to ensure the information is valuable to others.
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In the long run, architectural criteria should include construction worker safety as a goal of
the design process. Currently, the goals of designers are not comprehensive or systematic.
Architectural criteria (e.g., aesthetics, area efficiency, site views) prevail over engineering
performance criteria (e.g., energy efficiency, natural ventilation, structural performance).
Designers seldom consider construction worker safety during the design process. Only when the
construction worker safety issue is clearly set as a goal of the design process will designers
deliberately generate and chose design options which make the construction site safe. The
adoption of the design-build method will most likely benefit from the cooperation. Even when
using the traditional design-bid-build method, the risk for both designers and constructors will be
reduced and the adversarial climate in the construction industry will change.
Designers might ask for increased design fees considering that they are taking more
responsibilities. The business arrangements should compensate the designers for their extra effort
to create a better building information model.
By adopting this process, both designers and constructors will contribute their efforts to
incorporate designing for construction safety information into construction documents and
cooperate to minimize or eliminate non-compliance in drawings. On one hand, it will be easier
for designers to consider construction worker safety during the design phase because this
application tool provides accessibility to related safety knowledge. On other hand, constructors
as the data recipients will also have the ability to check building models and take corresponding
precautions. The safety culture will be changed-- the designers and constructors will work
collaboratively to identify potential hazards early and correct them before accidents occur.
The uniqueness of each construction project makes it difficult to evaluate the benefits of
BIM. With the large number of construction projects that adopted BIM and that have been
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successfully finished in recent years, the evidence shows that BIM technology could improve
construction worker safety.
Finally, it should be realized that no one method is capable of identifying all types of
safety hazards on a construction site. Multiple methods or application tools should be used to
address the full range of design for safety issues.
Drawbacks
The collected D4S suggestions can be classified into two types: quantitative and
qualitative. The first kinds of suggestions are constrained either by precise parameters or by
certain materials. An example of a quantitative constraint is “Design window sills to be 42 inches
minimum above the floor level. Window sills at this height will act as guardrails during
construction.” Another kind of suggestion is more descriptive and difficult to be checked. A
concept can be uncheckable because a building model may never have the information, or
because the information will exist only on site in the actual building, or in the mind of an
inspector. For example, one best practice is “Design appropriate and permanent fall protection
systems for roofs to be used for construction and maintenance purposes. Consider permanent
anchorage points, lifeline attachments, and/or holes in the perimeter for guardrail attachment.”
OSHA standards also correspondingly require that (Appendix C to Subpart M fall protection):
(h) ‘Tie-off considerations.’ (1) One of the most important aspects of personal fall protection systems is fully planning the system before it is put into use. Probably the most overlooked component is planning for suitable anchorage points. Such planning should ideally be done before the structure or building is constructed so that anchorage points can be incorporated during construction for use later for window cleaning or other building maintenance. If properly planned, these anchorage points may be used during construction, as well as afterwards.
However, most building models do not contain such detailed structural objects.
The second drawback of the current safety tool is the lack of a systematic classification of
the results of the D4S check based on its severity. Although the knowledge base of the D4S
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application tool comprehensively and systematically includes a large number of designing for
construction worker safety suggestions, the information about the probability and severity of
violating certain provisions has not been incorporated in the current software tool. This is mainly
due to the lack of related data. As shown in the Chapter 4, Solibri Model Check has the function
to classify non-compliances based on preset severity. Every computable rule could be assigned a
risk rate. Users could set a tolerance level before conducting compliance checking. Only the non-
compliances with a rate higher than the preset risk value would be reported to the user.
The third drawback is that the construction schedule has not been added into the system as
a factor. The situation on construction sites keeps changing day by day. The safety hazards on
site one day might be gone during the next few days as progress is made on the project. Thus,
just checking the final building model will miss many hazards which emerge and subsequently
disappear on a construction site. The project schedule also should be considered when
conducting the code checking.
In Chapter 3, a computable rule based on BIMserver is developed to query the area value
of an IfcOpeningElement. As mentioned in that chapter, the opening element extrusion segments
may have many profiles, and three kinds of profiles are defined in IFC 2×3. They are
IfcRectangleProfileDef, IfcCircleProfileDef and IfcArbitraryClosedProfileDef. The IFC
rectangle profile is the most common profile of the IfcOpeningElement. The rule developed in
Chapter 3 is based on the IfcRectangleProfileDef. However, the other two profiles may also exist
in building models. For instance, Figure 5-1 demonstrates a paragraph of IFC code which defines
an IfcOpeningElement with an arbitrary closed profile. The IfcArbitraryClosedProfileDef defines
an arbitrary 2-D profile. From a list of points stored in IfcPolyLine, the outer boundary of this
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surface or solid can be constructed, which is shown in Figure 5-2. It is relatively difficult to
compute the area value of an opening element with an IfcArbitraryClosedProfileDef.
Figure 5-1. IfcOpeningElement with an IfcArbitraryClosedProfileDef
Figure 5-2. IfcArbitraryClosedProfileDef defined by six points
Recommendations for Future Research
Since D4S knowledge can be incorporated into designs in various ways, research studies
should be conducted to assess different processes and their impact in addressing construction
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worker safety. Research is needed to develop evaluation metrics, identify benchmarks for safety
and health performance, and assess the performance relative to benchmarks.
To support designers in incorporating safety into the design, it is important to know how
designers think and work. The knowledge of the mental process and communication patterns of
designers or design teams is limited. This D4S application tool is currently designed for general
use, which means there are no specific rule sets in this application for certain kinds of buildings.
The function of the building, such as commercial, residential or industrial, will affect the kinds of
provisions that are applicable to a specific construction project. With the improvement of the
database, users such as health centers and educational institutions, could accumulate best
practices for particular types and develop their own rule sets. Furthermore, some provisions in
the D4S database are not applicable to object-oriented compliance checking. They have to be
checked through a manual process.
Last, the design for construction safety application mainly uses IFC to check non-
compliance in finished building drawings, so the features of the current IFC are important to the
performance of code checking applications. The function of the checking system can be
improved in two ways by enhancing the interoperability of IFC and BIM applications. First, the
function of the IFC schema needs to be improved to support the D4S rules checking system to
conduct more types of checks. Currently, the code checking systems are restricted in their
applications because of a “restricted range of objects and parameters for encoding building codes
and domain knowledge”. The good news is that buildingSMART International keeps on updating
the IFC schema. The IFC 2×4 was introduced in 2010 and it is being adopted by more and more
software tools.
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The interoperability between software applications should be further improved. For
participants of a project, software which would enhance the ability of individual firms to
effectively communicate with other firms should be selected. On the other hand, what is more
important is that software producers should guarantee the reliability of the exchanged
information and enhance the integrity of the exchanged data. Although all the BIM software used
in this research study were certified as compliant with IFC release 2×3, a large amount of
applications in the AEC industry still do not support the IFC data format to exchange project
data.
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APPENDIX A FALL PROTECTION BEST PRACTICS
Section 1: FLOOR OPENINGS 1.1 Group floor openings together to create one larger opening rather than many smaller openings. 1.2 Locate floor openings away from passageways, work areas, and the structural perimeter. 1.3 Eliminate tripping hazards around floor openings (Avoid minor changes in floor elevations and raised thresholds). 1.4 When design features such as ventilation systems, trash chutes, chimneys, elevators, skylights, etc. cause floor openings to occur during construction, provide a warning in the plans and specifications for construction, and design in permanent/temporary guardrail systems and sequence them early in the construction process for use by all contractors. Section 2: ROOF OPENINGS 2.1 Locate roof openings away from the edge of the structure. 2.2 Group roof openings together to create one larger opening rather than many smaller openings. 2.3 Provide permanent/temporary guardrails around roof openings. 2.4 Eliminate tripping hazards (raised areas or other encumbrances) around roof openings. 2.5 Locate rooftop mechanical/HVAC equipment away from roof edge and roof openings. 2.6 Locate skylights on flat areas of the roof and away from the roof edges. 2.7 Place skylights on a raised curb (10-12 inches). 2.8 Provide permanent guardrails around skylights. 2.9 Design domed, rather than flat, skylights with shatterproof glass or add strengthening wires. Section 3: ROOF FALL PROTECTION 3.1 Design the parapet to be 42 inches tall. A parapet of this height will provide immediate guardrail protection and eliminate the need to construct a guardrail during construction or for future roof maintenance.
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3.2 Minimize the roof pitch to reduce the chance of workers slipping off the roof. 3.3 Provide a guardrail around roof accesses and roof work areas. 3.4 Design appropriate and permanent fall protection systems for roofs to be used for construction and maintenance purposes. Consider permanent anchorage points, lifeline attachments, and/or holes in perimeter for guardrail attachment. 3.5 Design in a means of attaching a railing and safety lines for roofing operations. 3.6 Design and schedule eye-bolts or other connections used for window maintenance so that they can be constructed as early as possible and used during construction. 3.7 When specifying roofing materials which are not suitable for walking, such as corrugated fiberglass panels, ensure they are distinguishable from safe, secure walking surfaces on the roof, or install guardrails around surfaces not suitable for walking. 3.8 Provide a covering, or extend the roof line over exterior stairs, ramps, and walkways. 3.9 Before demolishing and renovating any roof structure which is damaged, ensure that an engineering survey is performed by a competent person to determine the condition of the roof, trusses, purlins, and the structure itself to evaluate the possibility of the structure and its components failing during the work, and to evaluate how fall protection devices will be incorporated into the structure being demolished/renovated. 3.10 Avoid the design of elevated exterior structures, equipment, etc. next to roof edges. Section 4: STRUCTURAL: STEEL 4.1 In multi-story buildings, design each floor plan to have a smaller area than the story below to prevent objects and workers from falling more than one story. 4.2 To minimize the risk of falling, minimize the number of offsets, and make the offsets a consistent size and as large as possible. 4.3 Prefabricating steel to accommodate fall protection. 4.4 Design special attachments or holes in members at elevated work areas to provide permanent, stable connections for supports, lifelines, guardrails, and scaffolding. 4.5 For tower type structures, design a cable-type lifeline system into the structure that allows workers to be hooked onto the structure and allows for their movement up and down the structure. Section 5: STRUCTURAL: CONCRETE and MASONRY
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5.1 Design scaffolding tie-off points into exterior walls of buildings for construction purposes. 5.2 For precast concrete members, provide inserts or other devices to attach fall protection lines. 5.3 Design perimeter beams and beams above floor openings to support lifelines (minimum dead load of 5400 lbs.). Design connection points along the beams for the lifelines. Note on the contract drawings which beams are designed to support lifelines, how many lifelines, and at what locations along the beams. Section 6: WINDOWS 6.1 Design window sills to be 42 inches minimum above the floor level. Window sills at this height will act as guardrails during construction. Section 7: WALKWAYS and FLOORS 7.1 Protect exterior walkways and platforms from the weather by providing a covering, extending the roof line, or locating them on the sheltered side of the structure. 7.2 Locate exterior walkways and platforms away from the north side of the structure to prevent the buildup of moss and ice due to lack of sun. 7.3 Using natural lighting for stairways and access areas. 7.4 Provide non-slip walking surfaces on floors, walkways and platforms adjacent to open water or exposed to the weather.
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APPENDIX B SAMPLE CODES: NET AREA VALUE OF IFCSLAB
/* Author: ======= Name : Simon Qi Department : Building Construction, University of Florida, USA Work : Design for Construction Worker Safety Advised by : Professor Raymond Issa, Jimmie Hinze Query : Locate the floor/roof opening Description : Find all the query object of IfcOpeningElement which are attached to either a floor/ roof IfcSlab. Approach: 1. Load the Building stories 2. For every stories, get the IfcProduct and check the instance as IfcSlab. 3. Using RelVoidsElement, get related IfcFeatureElementSubtraction for the IfcSlabs 4. Use the collection in step 3 and the IfcRelDefines, get the IfcPropertySetDefintion collection. 5. Check for the IfcElementQuantity instance in the collection at step 4. 6. Using the IfcElementQuantity in step 5, get the IfcPhysicalQuantity 7. Typecast the IfcPhysicalQuantity to IfcQuanityArea to get the required Area Value for consideration. */ package org.bimserver.querycompiler; import java.io.PrintWriter; import org.bimserver.ifc.database.IfcDatabase; import java.util.*; import java.util.ArrayList; import java.util.Iterator; import org.bimserver.ifc.emf.Ifc2x3.*; public class Query implements QueryInterface { private IfcDatabase model; private PrintWriter out; @Override public void query(IfcDatabase model, PrintWriter out) { /* Checking how many element quantity is present in the given model. To ensure the model has element quantity*/
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List<IfcElementQuantity> qty = model.getAll(IfcElementQuantity.class); out.println("Total Element quantity in the model are "+qty.size()); List<IfcBuildingStorey> stories = model.getAll(IfcBuildingStorey.class); List<IfcFeatureElementSubtraction> Opening_subjectToArea = new ArrayList<IfcFeatureElementSubtraction>(); if(!(stories.isEmpty())){ for (IfcBuildingStorey storey : stories) { for (IfcRelContainedInSpatialStructure rel : storey.getContainsElements()) { for (IfcProduct product : rel.getRelatedElements()) { if (product instanceof IfcSlab) { IfcSlab tempSlab = (IfcSlab)product; IfcElement ifcslabElement = (IfcElement)tempSlab; for(IfcRelVoidsElement relVoids : ifcslabElement.getHasOpenings()){ Opening_subjectToArea.add(relVoids.getRelatedOpeningElement()); } } } } } } else{out.println("Building stories not available...");} if (!(Opening_subjectToArea.isEmpty())) { out.println("Total Opening Element in the model which are associated to slabs are " + Opening_subjectToArea.size()); Iterator OE_it = Opening_subjectToArea.iterator(); while (OE_it.hasNext()) { IfcOpeningElement openingElement = (IfcOpeningElement) OE_it.next(); for (IfcRelDefines ifcRelDefines : openingElement.getIsDefinedBy()) { if (ifcRelDefines instanceof IfcRelDefinesByProperties) { IfcRelDefinesByProperties ifcRelDefinesByProperties = (IfcRelDefinesByProperties) ifcRelDefines; IfcPropertySetDefinition relatingPropertyDefinition = ifcRelDefinesByProperties.getRelatingPropertyDefinition(); if (relatingPropertyDefinition instanceof IfcPropertySet) {
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IfcPropertySet ifcPropertySet = (IfcPropertySet)relatingPropertyDefinition; for (IfcProperty ifcProperty : ifcPropertySet.getHasProperties()) { if (ifcProperty instanceof IfcPropertySingleValue) { IfcPropertySingleValue ifcPropertySingleValue = (IfcPropertySingleValue)ifcProperty; if (ifcPropertySingleValue.getNominalValue() instanceof IfcAreaMeasure) { IfcAreaMeasure ifcAreaMeasure = (IfcAreaMeasure)ifcPropertySingleValue.getNominalValue(); out.println("Area for " + openingElement + ": " + ifcAreaMeasure.getWrappedValue()); } } } } } } } } else { out.println("No match for Opening element incorporated to slab");} } }
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APPENDIX C SAMPLE CODES: IFCOPENINGELEMENT AREA VALUE RETRIVEAL
/* Author: ======= Name : Simon Qi Department : Building Construction, University of Florida, USA Work : Design for Construction Worker Safety Advised by : Professor Raymond Issa, Jimmie Hinze Query : Locate the floor/roof opening Description : Find all the query object of IfcOpeningElement which are attached to either a floor/ roof IfcSlab. Approach: 1. Load the Building stories 2. For every story, get the IfcProduct and check the instance as IfcSlab. 3. If the instance is an IfcSlab, get its generalized parent object IfcElement. 4. Using IfcElement, check the object has any opening elements using getHasOpenings() which will be a relationship IfcRelVoidsElement 5. Collect the IfcOpeningElement into a collection from the relationship class IfcRelVoidsElement using getRelatedOpeningElement() 6. Interested IfcOpeningElements are rectangle opening elements and its pertaining area. 7. Iterate the collection of IfcOpeningElements, to get the X Dimension and Y Dimension values to calculate area as follows. 8. Objective is to find the path: IfcOpeningElement -> IfcExtrudedAreaSolid -> IfcRectangleProfileDef for the methods getXDim() & getYDim() 9. Get the IfcRepresentation and iterate over them to find the IfcShapeRepresentation which will return the items of IfcExtrudedAreaSolid 10. IfcExtrudedAreaSolid has the profile defintion among which somewhere IfcRectangleProfileDef. 11. Check for the instance of IfcRectangleProfileDef to invoke the getXDim() and getYDim() 12. Calculate the area as a product of the return values of the above dimension methods. 13. Use the area value for suitable filtering of IfcOpeningElement under subjective search area criteria. */ package org.bimserver.querycompiler; import java.io.PrintWriter; import org.bimserver.ifc.database.IfcDatabase; import java.util.*; import java.util.ArrayList; import java.util.Iterator;
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import org.bimserver.ifc.emf.Ifc2x3.*; public class Query implements QueryInterface { private IfcDatabase model; private PrintWriter out; @Override public void query(IfcDatabase model, PrintWriter out) { List<IfcBuildingStorey> stories = model.getAll(IfcBuildingStorey.class); List<IfcFeatureElementSubtraction> Opening_subjectToArea = new ArrayList<IfcFeatureElementSubtraction>(); if(!(stories.isEmpty())){ for (IfcBuildingStorey storey : stories) { for (IfcRelContainedInSpatialStructure rel : storey.getContainsElements()) { for (IfcProduct product : rel.getRelatedElements()) { if (product instanceof IfcSlab) { IfcSlab tempSlab = (IfcSlab)product; IfcElement ifcslabElement = (IfcElement)tempSlab; for(IfcRelVoidsElement relVoids : ifcslabElement.getHasOpenings()){ Opening_subjectToArea.add(relVoids.getRelatedOpeningElement()); } } } } } } else{out.println("Building stories not available...");} if (!(Opening_subjectToArea.isEmpty())) { out.println("Total Opening Element in the model which are associated to slabs are " + Opening_subjectToArea.size()); Iterator OE_it = Opening_subjectToArea.iterator(); while (OE_it.hasNext()) { IfcOpeningElement openingElement = (IfcOpeningElement) OE_it.next(); IfcProductRepresentation representation = openingElement.getRepresentation();
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IfcProductDefinitionShape ifcProductDefinitionShape = (IfcProductDefinitionShape)representation; for (IfcRepresentation ifcRepresentation : ifcProductDefinitionShape.getRepresentations()) { if (ifcRepresentation instanceof IfcShapeRepresentation) { IfcShapeRepresentation ifcShapeRepresentation = (IfcShapeRepresentation)ifcRepresentation; for (IfcRepresentationItem item : ifcShapeRepresentation.getItems()) { if (item instanceof IfcExtrudedAreaSolid) { IfcExtrudedAreaSolid extrudedAreaSolid = (IfcExtrudedAreaSolid)item; IfcProfileDef sweptArea = extrudedAreaSolid.getSweptArea(); if (sweptArea instanceof IfcRectangleProfileDef) { IfcRectangleProfileDef rectangleProfileDef = (IfcRectangleProfileDef)sweptArea; float area = rectangleProfileDef.getXDim() * rectangleProfileDef.getYDim(); out.println("X dimension:"+rectangleProfileDef.getXDim()); out.println("Y dimension:"+rectangleProfileDef.getYDim()); out.println("Area calculated from geometry: " + area); } } } } } } } else { out.println("No match for Opening element incorporated to slab");} } }
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APPENDIX D SAMPLE CODES: QUERYING RELATIONAL DATABASE WITH SQL
SELECT Windows.[Id], Windows.[Level], Windows.SillHeight FROM Windows WHERE Windows.SillHeight < 1.0668 AND Windows.Level > (SELECT MIN(Floors.Level) FROM Floors) ORDER BY Windows.Level ASC
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BIOGRAPHICAL SKETCH
Jia Qi was born in 1982 in Zhangjiakou, China. He received his Bachelor of Management
degree in Construction Engineering Management at the Shijiazhuang Tiedao University. In 2005
he started his studies in Management Science and Engineering at the Tianjin University. Here, he
got involved in scientific research study as graduate assistant to Professor Jingmin Zha. He
finished his study with a master’s thesis on the topic of corporate social responsibility in the
construction industry in 2007. In the same year he joined the M.E. Rinker, Sr. School of Building
Construction at the University of Florida. He received his Ph.D. from the University of Florida in
the fall of 2011.
His research interests are in the fields of construction worker safety and Building
Information Modeling. He has published several conference papers.
