Retrofitting of damaged industrial buildings

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308

(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME

267

RETROFITTING OF DAMAGED INDUSTRIAL BUILDINGS

Dr. Suchita Hirde*, Ms. Minakshi Jagtap

**

* Professor, Dept. of App. Mechanics Govt. College of Engineering Karad 415124 India

** PG student, (Civil- Structure), Govt. College of Engineering, Karad 415124, India

ABSTRACT

The cost of civil infrastructure constitutes a major portion of the national wealth. The rapid

damage of structure is thus created an urgent need for the development of novel, retrofit & new

construction. Retrofitting of existing structures is a difficult task as compared to the construction of a

new building as each building poses an unique set of constraints & problems requiring due care in

design & detailing. The development of any retrofit scheme involves a thorough study of the

performance of the structure subjected to design forces.

In this paper an attempt has been made to present case studies of rehabilitation & retrofitting

of industrial buildings. Retrofitting of two industrial buildings has been described in this paper. The

case studies include retrofitting of industrial steel structures damaged due to faulty design and a

structure requiring modification for operational purpose. The best possible retrofitting strategy

which is both economical & effective have been worked out and presented in this paper.

KEYWORDS: Damaged industrial building, rehabilitation, retrofitting, analysis

INTRODUCTION

In this paper, analysis of the damaged industrial building for ascertaining the current

performance is carried out by using static linear analysis. Retrofitting strategies required for the same

building is suggested based upon the current performance of structure, expected performance of

structure & type of damage. Strength is ascertained by carrying out the analysis of retrofitted

building. Finally best possible retrofitting strategies that will be both economical & effective are

determined. During the damage stage of any building, a survey is required to investigate the

conditions of such distressed building. Because of the vast variety of the building structures, the

development of a general rule for retrofitting measure is rather difficult and to a large extent each

structure must be approached as a strengthening problem on its own merits. It is necessary to take a

decision whether to demolish a distressed structure or to restore the same for effective load carrying

system. Many a times, the level of distress is such that with minimum restoration measure the

building structure can be brought back to its normalcy and in such situation, rehabilitation or

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ISSN 0976 – 6308 (Print)

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retrofitting is preferred. The process of keeping things in working order is called maintenance.

Proper maintenance of structure is required to prevent damages & decay due to natural agencies &

wear and tear & to keep them in good appearances and working condition as well as to repair the

defects occurred in the structure & strengthen them, if necessary. Maintenance includes servicing,

repairing, rectification, replacement, rehabilitation, retrofit, renovation & restore of structure. In the

process of rehabilitation the existing strength of the structure is retained while in case of retrofitting

it is the structural enhancement for improved performance during hazards. In this paper rehabilitation

and retrofitting of two industrial buildings has been described The case studies include retrofitting of

industrial steel structure damaged due to faulty design and a structure requiring modification for

operational purpose.

RETROFIT OF DAMAGED INDUSTRIAL BUILDINGS

Survey of damaged industrial buildings in Pune region have been carried out and based upon

the review of industrial site visits, two damaged industrial structures are selected for retrofitting

strategy so as to include different type of damages such as steel structures damaged due to faulty

design & structure required modification for operational purpose. The name of the industry is

purposefully omitted from the paper.

Case study 1-Structure damaged due to faulty design An industrial steel building which is structurally failed due to faulty design is presented this

section. In this steel building most of the members of steel roof trusses are deflected along one side

as well as purlins are also failed due to faulty design. Therefore this structure is required to be

redesigned & strengthen.

Building description: The details of this industrial structure are given as follows

Height of Shed = 5.00 m;

Span of truss = 9.00 m;

Length of Shed = 25.9 m

Figure 1 shows photograph of existing structure. The plan & elevation of existing industrial building

is shown in figure 2 & 3 respectively.

Modeling of existing & retrofitted building The existing & retrofitted building is modeled using STAAD-Pro software. The retrofitting

is carried out for an existing industrial building by two ways. In first option additional members are

welded to the various existing structural members while second option consists of introduction of

Figure 1- Photograph of existing structure



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additional truss at the bottom side of the existing truss. Thus the following models have been studied

and presented in the paper.

Model I: Modeling of existing industrial building in order to ascertain the current performance of the

structure.

The existing sizes of various structural members of damaged industrial building are as given

in the following table 1 and model is shown in figure 4.

Table 1: Sizes of structural members of damaged industrial building

Member Size of Section

Bottom chord ISA 50x50x6

Top chord ISA 50x50x6

Inclined member ISA 50x50x6

Vertical member ISA 50x50x6

Column ISMC 100 box 200mm apart

Purlin Angle 50x50x6

Model II : Modeling of retrofitted industrial building in which retrofitting is carried out by

welding unequal angle sections to the existing top & bottom chord members and welding of equal

angle sections to existing inclined members. Existing purlins having size of section

Figure 2- Plan of original structure



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Figure 3- Elevation of original structure

ISA 50x50x6 are replaced by ISMC 75. The existing purlins ISA 50x50x6 are used for welding to all

inclined & vertical members of truss. (Refer figure 5 and figure 6)

Retrofitted sizes of various structural members for option I are as given in the table 2

Table 2: Sizes of structural members in retrofitted building (option I)


Bottom chord ISA 50x50x6 welded with ISA 65x65x6

Top chord ISA 50x50x6 welded with ISA 65x65x6

Inclined member ISA 50x50x6 welded with ISA 50x50x6

Vertical member ISA 50x50x6 welded with ISA 50x50x6


Purlin ISMC 75

Model III : Modeling of retrofitted industrial building in which retrofitting is carried out by

introduction of additional truss at the bottom side of the existing truss. (Refer figure 7)

Retrofitted sizes of various structural members for option II are as given in the table 3

Table 3: Sizes of structural members in retrofitted building (option II)


Bottom chord Existing ISA 50x50x6

Top chord Existing ISA 50x50x6

Inclined member Existing ISA 50x50x6

Vertical member Existing ISA 50x50x6


Purlin ISMC 75

Additional bottom member (0.7m below

bottom chord) 16mm bar

Additional tie members between bottom

chord & additional bottom member 16mm



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Analysis of building Equivalent static analysis is performed on the above 3D models. As the existing building is

industrial building wind load is predominant load along with the dead load & live load because area of

opening is more as compared to other structural buildings. This building is structurally failed

immediately after the construction of building due to faulty design.

Figure 4- Model I : Original structure

Figure 5- Model II: Retrofitted structure (option I)



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Figure 6- Welding of different angle sections

Figure 7- Model III: Retrofitted structure (option II)

Thus for the gravity model analysis only dead load & live load are considered; while wind

load is considered for the analysis of retrofitted model. The building model is then analyzed by the

software STAAD-Pro in order to ascertain the performance of retrofitted structure. Number of trials

has been carried out to get safe sizes for various members. The final sizes which are safe for the

calculated loads have been given in table 2 and 3.



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Comparison of retrofitting Strategy Based on the analysis & design results for damaged industrial building due to faulty design,

retrofitting was suggested for failed structural members by the application of two strategies. In first

retrofitting strategy additional members are welded to the various existing structural members while

second strategy consists of introduction of additional truss at the bottom side of the existing truss.

The static analysis of retrofitted structures is also carried out by using STAAD-Pro software.

Analyzing strategies i.e. strategy-1, welding of different angle sections to the existing top & bottom

chord members and welding of equal angle sections to existing inclined members & strategy-2,

introduction of additional truss at the bottom side of the existing truss, it is observed that strategy two

is effective and economical. But in strategy-2 clear ceiling height is reduced by 0.7 m, also as per

aesthetic point of view strategy-2 is not good as compared to strategy-1. Hence in order to have more

headroom, strategy-1 is suggested.

Case Study 2- Structure required modification for operational purpose

In an industrial building, it is required to remove one column so as to form the large opening

for the industry work facilities. Due to creation of large opening the two columns near the opening

are subjected to heavy loads & for this load these two columns are required to be redesigned as well

as strengthened. Also the footings of same column may require to be redesigning as well as

strengthening.

Building description The details of this industrial structure are given as follows

Height of Shed = 11.00 m; Span of truss = 11.00 m; Length of Shed = 30.9 m

The plan of existing industrial building is shown in figure 8. In plan column marked with circle is

required to be removed for the industry work facilities.

Modeling of building The retrofitting of existing industrial building is carried out by introduction of additional

beam having span 10m between two columns which are adjacent to the opening. to support the truss

which is supported by removed column. The building is modeled using STAAD-Pro software. Thus

the following models have been studied and presented in the paper.

Model I : Modeling of the existing truss which rest on removed column in order to calculate the

reaction of truss.

Model II : Modeling of introduced beam to support the truss (Refer figure 9 and 10)

The sizes of various structural members of this beam are as given below in table 4

Table 4: Details of beam


Bottom chord ISMC 250

Top chord ISMC 250

Inclined member ISA 50x50x6

Vertical member ISA 50x50x6

Model III : Modeling of existing columns which are adjacent to the opening to check for additional

load of introduced beam (as shown in figure 11)



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Analysis of building Equivalent static analysis is performed for all 3D models. As the existing building is

industrial building wind load is predominant load along with the dead load & live load because area

of opening is more as compared to other structural buildings. The building model is analyzed by the

software STAAD-Pro in order to ascertain the performance of retrofitted structure.

Retrofitting Strategy In this structure, modification of structure is done for operational purpose by removing one

column, so as to form large opening. Due to this two columns near the opening are subjected to

additional load.

Figure 8 – Plan



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Figure 9- Model of trusses and beam

Figure 10- Load on beam



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Figure 11- Model of columns

Thus retrofitting of existing structure is carried out by introduction of additional beam

having span 10m between two columns which are adjacent to the opening. The static analysis of the

beam for given reaction of truss is carried out using STADD-Pro software. From the result of

analysis, it is noticed that all members of introduced beams are safe for the applied load. The

analysis of column is carried out to support the beam with additional loads due to trusses. Based on

the result of analysis, it is noticed that the existing sizes of column i. e. 2 ISMC 300 – 900 mm apart

are sufficient to carry the additional load. This strategy of introducing the beam to support the truss is

found to be effective in this case because it is easily feasible on site also it requires less time without

any disturbance to the various structural members & daily activities of industry work.

CONCLUSION

As the number of civil infrastructure systems increases worldwide, the number of damaged

buildings & structures also increases. In those cases complete replacement is likely to be an

increasing financial burden & might certainly be a waste of natural resources. To overcome this

difficulty a viable alternative in the form of upgrading or strengthening is required. The suggested

retrofitting strategies or measures have been found to be effective & economical in order to ensure

the safety of the life & property of the occupants.

REFERENCES

1. Michel Bruneu (2005), “Seismic Retrofit of Steel Structure”, 1st Canadian Conference on

Effective Design of Structure McMaster University Hamilton, Ontario, Canada July 10- 13.

2. Yu, Q.S., Uang, C.M. and Gross, J.L., (2000), “Seismic Rehabilitation Design of Steel Moment

Connection with Welded Haunch”, Journal of Structural Engineering, ASCE, Vol. 126, No. 1,

pp. 57-68.



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3. IS : 875 (Part 1) – 1987: Indian Standard Code of Practice for Design Loads (Other Than

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ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.

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of Civil Engineering & Technology (IJCIET), Volume 4, Issue 1, 2013, pp. 117 - 125,

ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.

Retrofitting of damaged industrial buildings

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