Guidebook-1 Load Effects on Structures

8/12/2019 Guidebook-1 Load Effects on Structures

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FOREWORD

The Leonardo da Vinci Project CZ/08/LLP-LdV/TOI/134020 Transfer of Innovations

Provided in Eurocodes addresses the urgent need to implement the new system of European

documents related to design of construction works and products. These documents, called

Eurocodes, are systematically based on the recently developed Council Directive89/106/EEC The Construction Products Directive and its Interpretative Documents ID1 and

ID2. Implementation of Eurocodes in each Member State is a demanding task as each country

has its own long-term tradition in design and construction.

The project should enable an effective implementation and application of the new

methods for designing and verification of buildings and civil engineering works in all the

partner countries (CZ, DE, ES, IT, NL) and in other Member States. The need to explain and

effectively use the latest principles specified in European standards is apparent from various

enterprises, undertakings and public national authorities involved in construction industry and

also from universities and colleges. Training materials, manuals and software programmes for

education are urgently required.

The submitted Guidebook 1 is one of 2 upcoming guidebooks intended to providerequired manuals and software products for training, education and effective implementation

of Eurocodes:

Guidebook 1: Load Effects on Buildings

Guidebook 2: Load Effects on Bridges

It is expected that the Guidebooks will address the following intents in further

harmonisation of European construction industry:

- reliability improvement and unification of the process of design;- development of a single market for products and for construction services;- new opportunities for trained primary target groups in the labour market.The Guidebook 1 is focused on determining load effects on buildings and industrial

structures. The following main topics are treated in particular:- basic requirements on structures,

- basis of structural design,

- actions on buildings including accidental actions,

- combination rules for load effects,

- examples and case studies.

Annex A to the Guidebook 1 provides a review of the basic statistical concepts used in

design assisted by testing, Annex B a short description of general procedures used for

assessment of existing structures and Annex C provides latest information on further

development of Eurocodes. The Guidebook 1 is written in a user-friendly way employing only

basic mathematical tools. Attached software products supplemented by a number of examplesenable direct applications of general rules in practice.

A wide range of potential users of the Guidebooks and other training materials

includes practising engineers, designers, technicians, experts of public authorities, young

people - high school and university students. The target groups come from all territorial

regions of the partner countries. However, the dissemination of the project results is foreseen

to be spread into all Member States of CEN and other interested countries.

Prague 2009


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Contents

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GUIDEBOOK 1 BASIS OF DESIGN AND ACTIONS ON BUILDINGS

CONTENTS

Page

FOREWORD 3

CONTENTS 5

1 BASIC REQUIREMENTS 11Summary 11

1 Introduction 11

2 Basic requirements 12

2.1. Principal requirements 12

2.2 Requirements related to the permanent design situations 13

2.2 Requirements related to the accidental design situations 13

3 Reliability management 14

4 Design working life 155 Durability 16

6 Quality management 17

References 18

Appendix A Reference documents 19

A.1. Introduction 19

A.2. Construction Product Directive 19

A.3. Interpretative document No. 1 Mechanical resistance and stability 20

A.4. Guidance Paper L 23

2 BASIS OF DESIGN GENERAL PRINCIPLES 32

Summary 32

1 Introduction 32

1.1. Background documents 32

1.2 General principles 32

2 Historical development 33

2.1 Uncertainties 33

2.2 Definition of reliability 34

2.3 Development of design methods 35

3 Basic concepts of EN 1990 37

3.1 Design working life and design situation 37

3.2 Limit states 373.3 Ultimate limit states 40

3.4 Serviceability limit states 41

4 Verification of limit states 424.1 Verification of static equilibrium and strength 424.2 Verification of the serviceability limit states 43

5 Concluding remarks 43

Reference 44

Appendix A A reinforced concrete slab various design concepts 45A.1 Introduction 45A.2 A reinforced concrete slab 45

A.3 Design and reliability consideration 45A.4 Concluding remarks 47


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3 RELIABILITY DIFFERENTIATION 48

Summary 48

1 Introduction 48


1.2 General principles 482 Basic reliability elements 49

3 Target reliability in the Eurocodes 50

3.1 General 50

3.2 Reliability classes 50

3.3 Variation with time Discussion 51

3.4 Global failure robustness 53

3.5 Existing structures 53

4 Partial safety factors 51

4.1 Derivation based on reliability methods 54

4.2 Simplified reliability differentiation (Annex B of EN 1990) 55

5 Examples 565.1 Residential steel building 56

5.2 Agricultural steel building 56

5.3 Agricultural concrete building 56


References 57

Appendix A: Risk Acceptance Approaches in Codes 58

A.1 General 58

A.2 Human safety 58

A.3 Calibration 59

A.4 Cost benefit approach 60

References 61

4 ACTIONS 62Summary 62

1 Introduction 62

1.1 Background documents 62

2 Actions and effects of actions 62

2.1 Definitions of actions 622.2 Effect of actions 63

3 Classification of actions 65

3.1 General 653.2 By their variation in time 65

3.3 By their origin 65

3.4 By their variation in space 65

3.5 By their nature or structural response 65

3.6 Bounded and unbounded actions 66

3.7 Environmental influences 66

4 Reference period and distribution of maxima 66

4.1 Climatic actions 66

4.2 Imposed actions 67

5 Characteristic values 69

5.1 General 695.2 Permanent actions 69


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5.3 Variable actions 70

5.4 Imposed loads 71

5.5 Snow loads 73

5.6 Wind loads 76

5.7 Thermal actions 81

6 Representative values 836.1 General 83

6.2 The combination value of a variable action 83

6.3 The frequent value of a variable action 83

6.4 The quasi-permanent value of a variable action 83

7 Representation of dynamic actions 84

8 Representation of fatigue actions 85

9 Representation of environmental influences 85References 85

5 ACCIDENTAL ACTIONS 86

Summary 861 Introduction 86

1.1. History 86


2 Eurocode approach 87

3 Design for impact and explosion loads 903.1 Impact from vehicles 90

3.2 Loads due to explosions 90

3.3 Design example of a column in a building for an explosion 91

4 Robustness of building 94

4.1 Background 94

4.2 Summary of design rules 94

4.2.1 Design Rules for Class 2, Lower Group, Framed structures 94

4.2.2 Rules for Class 2, Lower group, Load-bearing wall construction 95

4.2.3 Rules for Class 2, Upper Group, Framed structures 95

4.2.4 Rules for Class 2, Upper Group, Load-bearing wall construction 95

4.3 Example structures 96

4.3.1 Framed structure, Consequences class 2, Upper Group 96

4.3.2 Wall structure, Consequences class 2, Upper Group 96

5 Conclusions 97

References 97

Appendix A: Methodology related to robustness assessment 98A.1 Conditional probability of collapse 98

A.2 Quantification of robustness 99

A.3 Basic design philosophy 100

References 101

Appendix B: Impact Force Analysis 102

6 COMBINATION RULES IN EUROCODES 103

Summary 103

1 Introduction 103


1.2 General principles 1032 Combination of actions 104


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2.1 General 104

2.2 Combinations of actions in persistent and transient design situations 104

2.3 Combination of actions for accidental and seismic design situations 105

2.4 Combination of actions for serviceability limit states 106

3 Examples 106

3.1 Cantilivered beam 1063.2 Continuous beam of three spans 110

3.3 Cantilivered frame 113

3.4 Three bay two-dimensional frame 118


References 122

Appendix A: Alternative load combinations for the cantilevered beam 123

7 ACTIONS IN TRANSIENT DESIGN SITUATIONS 125

Summary 125

1 Introduction 125

1.1. Background documents 1251.2 General principles 125

2 Design situations during execution 125

2.1. Design situations 125

2.2 Nominal duration of design situations 126

3 Representative and design values of actions during execution 128

4 Combinations of actions 129

5 Actions during execution 129

6 Annex A for buildings and bridges 131

6.1. Annex A1 Supplementary rules for buildings 131

6.2 Annex A2 Supplementary rules for bridges 131

7 Annex B for Actions on structures during alteration, rehabilitation or

demolition 131

8 Concluding remarks 132References 133

8 ACTIONS AND COMBINATION RULES FOR SILOS AND TANKS 134

Summary 134

1 Introduction 1341.1. Background documents 134

1.2 Basic principles 134

2 Design situations 1353 Actions on silos and tanks 136

3.1 Types of actions 136

3.2 Actions specific on silos 136

4 Classification of silos 137

5 Combinations of actions for silos 137

5.1 Combinations of actions in persistent design situations 137

5.2 Combinations of actions in accidental design situations 138

5.3 Combinations of actions in seismic design situations 139

5.4 Combinations of actions in serviceability limit states 139

6 Combinations of actions for tanks 140

6.1 Actions 1406.2 Combinations of actions 140


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7 An example of slender silo 140

7.1 Introduction 140

7.2 Symmetrical filling loads on vertical walls 141

7.3 Filling patch load 143

7.4 Symmetrical discharge load 144

7.5 Discharge patch load 1458 Concluding remarks 145

References 145

9 LOAD EFFECTS IN STRUCTURAL MEMBERS 147Summary 147

1 Introduction 147



2 Verification of static equilibrium and strength 148

3 Verification of serviceability limit states 149

4 Examples 1494.1 Cantilevered beam 149

4.2 Continuous beam of three spans 153

4.3 Cantilevered frame 156


References 161

10 DESIGN OF A REINFORCED CONCRETE BUILDING ACCORDING

TO EUROCODES 162

Summary 162

1 Introduction 162

2 The building 162

3 Actions, loadings and load combinations 164

3.1 Density and self-weight 164

3.2 Imposed loads 164

3.3 Snow load 164

3.4 Wind actions 165

3.5 Load combinations for ULS verifications 167

3.6 Load combinations and limitations for SLS verifications 168

4 Materials 1694.1 Stress-strain diagrams 170

5 Results of the structural analysis 1706 Static verification examples 172

6.1 Verification of the first floor beams 172

6.2 Verification of the corner column 174


References 175

Appendix to Chapter 10 176

A.1 Basic structural drawings of the building 176

ANNEX A: DESIGN ASSISTED BY TESTING 185Summary 185

1 Introduction 1852 Statistical determination of a single property 185


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2.2 Assessment based on the characteristic value 186

2.3 Direct assessment of the design value 187

3 Statistical determination of resistance models 188

3.1 General procedure 188

3.2 An example of a concrete slab 191References 192

ANNEX B: ASSESSMENT OF EXISTING STRUCTURES 193Summary 193

1 Introduction 193

2 Principles and general framework of assessment 194

3 Investigation 197

4 Basic variables 198

5 Evaluation of inspection results 199

6 Structural analysis 2007 Verification 202

8 Assessment in the case of damage 202

9 Final report and decision 203

10 Numerical example 204

10.1 Updating of failure probability 204

10.2 Bayesian method for fractile estimation 205


References 208

ANNEX C: FURTHER DEVELOPMENT OF EUROCODES 209Summary 209

1 Introduction 209

2 New CPR and sustainable constructions 210

3 Evolution of Eurocodes 211

3.1 Maintenance 211

3.2 Harmonization 211

3.3 Promotion 2123.4 Further developments 213

4 Research for further development of Eurocodes 214

References 214


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Chapter 1: Basic requirements

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CHAPTER 1: BASIC REQUIREMENTS

Angel Arteaga1, Ana de Diego

1and Albert Alzate

1

1E. Torroja Institute of Construction Sciences, CSIC. Madrid. Spain

Summary

The Eurocodes system determines a set of basic requirements that all the structures

have to fulfil in order to adequate the structure to its foreseen use and expected live. These

requirements, based on European Commission Directives and other documents, are revised

and explained in this chapter.

1. INTRODUCTION

When a Member State joints the European Union (EU), it transfers some of its

competencies to the European Commission. The European Commission publishes a lot of

Directives that the Member States should adopt.

The competencies referring to the level of safety at each country in all the fields, and

in construction works in particular, are not transferred to EU; that means that each state is

allowed to determine the level of safety applicable inside the country, and, therefore, the

reliability level of its construction works.

In the field of construction, the European Commission delivered the Construction

Products Directive (CPD) [1], compulsory to the Member States, indicating the conditions

needed to facilitate the free circulation of the construction products in the European market(not only for European products). Furthermore, there is a wish in harmonizing all the design

procedures and values in a way that all the construction products and building companies can

move easily all around the EU.

The CPD states in its Annex I the six so-called essential requirements:

1. Mechanical resistance and stability

2. Safety in case of fire

3. Hygiene, health and the environment

4. Safety in use

5. Protection against noise6. Energy economy and heat retention

The Eurocode structural system only deals with the two firsts of these six

requirements. In this Guidebook only the first,Mechanical resistance and stability,will be

treated.

These requirements are complemented by the other EC documents known as

Interpretative Documents No. 1 (ID-1) [2] to Interpretative Documents No 6 (ID-6), each one

dealing with and explaining in detail the corresponding requirement, and the Guidance

Paper L [3], which defines the use of EN Eurocodes for structural design of works and in

technical specifications for structural products, and also the future actions related to the

Eurocode Programme.


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The main points of the CPD, ID-1, and the Guidance Paper Lmentioned above are

summarized in the Annex A of this Chapter.

2. BASIC REQUIREMENTS

2.1. Principal requirements

The essential Requirements 1 and 2, stated in the CPD and developed in the

Interpretative Documents ID-1 and ID-2, indicated above, are translated into clauses in the

Section 2 Requirementsof the Eurocode EN 1990: Basis of structural design[9].The first

requirement: Mechanical resistance and stabil ityis summarized in the first two clauses:

(1)P A structure shall be designed and executed in such a way that it will, during its

intended life, with appropriate degrees of reliability and in an economical way

sustain all actions and influences likely to occur during execution and use, and

remain fit for the use for which it is required.

(2)P A structure shall be designed to have adequate:

structural resistance,

serviceability, and

durability.

The third clause corresponds to the second Essential Requirement: Safety in case of fire.

(3)P In the case of fire, the load-bearing capacity of the structure shall be assured for

the required period of time.

In order to understand adequately this content, it should be distinguished, and so does

the Eurocode, between what is referred to the transient, permanent and accidental design

situations.Permanent design situations are those affecting the structure at most part of its

working life, taking into account aspects related with the safetystructural resistance, i.e.:

Ultimate Limit State (ULS); and with serviceability; i.e.: Serviceability Limit State (SLS);

and also with the durability; that is, the structural conditions that limit the deterioration of the

structure not influencing its performance.

Transient design situations are relevant during a period much shorter than the design

working life of the structure. They refer to temporary conditions of the structure, of use, or

exposure, e.g.during construction, repair or upgrading.

Therefore, taking into account the permanent and transient design situations,

a structure shall be designed, in a way that:

sustains all actions and influences likely to occur during execution and use, and remains fit for the use for which it is required.Accidental situations are those situations which are foreseeable to occur, but with a

small probability, during the working life of the structure.

In case of accidental design situations the EN 1990 [9] states:

A structure shall be designed and executed in such a way that it will not be damaged

by events such as:

explosion, impact, and the consequences of human errors,to an extent disproportionate to the original cause.


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2.2. Requirements related to the permanent design situations

First, it should be noted that the Eurocode system is mainly focused on the conditions

that the designer of the structures must take into account. For this reason the Clause 2.1 reads

that thestructure shall be designed, and executed; nothing is indicated in this clause about the

way the structure should be maintained. But the adequate use and maintenance of the structure

is fundamental for fulfilling these requirements. Therefore, other documents related with thebuildings or civil works must deal with these aspects.

Other important point is what means the so-called intended life, that is: the period of

time the structure is designed to fulfil its functions. This point is treated later in more detail.

The terms with appropriate degrees of reliability and in an economical way will

indicate the necessary trade-off between safety and economy. That is: the probability that the

structure fails to fulfil the requirements and the cost of building and maintenance of the

structure. As a first approach, a safer structure will require more detailed design, more

material (bigger sections), and/or more quality control in all the stages, therefore an increment

in the cost of execution of the work. The designer and owner have to balance this increment

of cost with the increase of safety, taking into account, in any case, the minimum safety

requirement determined in the country (not in the Eurocodes).

The designer must take into account that the structure has to sustain all actions and

influences likely to occur during execution and use; that is: the adequate behaviour taking into

account the Ultimate limit states, and at the same time has to remain fit for the use for which

it is required, the Serviceability Limit States.

Each type of foreseeable failure of the structure and/or its members will correspond to

different ULS: bending, shear, buckling, etc.; or SLS: cracks, deformations, sensibility to

vibrations, etc.; and will correspond to a different Limit State Function; that is, the

relationship (in general in mathematical form) between the actions or the effect of actions and

the resistances of the structural material at the member considered that divides the safe and

unsafe states of the structure or member. The Eurocodes give the way to determine theequations and the design values of the actions and resistances to be applied.

These two requirements are interrelated: traditionally one structure safe enough

fulfilling the ULS requirements was, normally, also stiff enough and it did not have

serviceability problems. Nowadays, the situation is just the opposite: new materials with

much higher resistance, and no stiffer in the same proportion and new design methods, yield

to slender elements, therefore more deformable structures, what is the origin of frequent

pathologies in the structures. It could be said now that one structure stiff enough is, probably,

safe enough.

2.3. Requirements related to the accidental situations

For the design of a structure, an accidental action is a type or value of one action that

is foreseeable to occur in the lifetime of the structure, but not likely; lets say, it has a

probability of 10-4 of occurrence during its working life. Possible accidental actions are not

only those considered in the EN 1990 [9]: gas explosion, impact, and consequences of human

gross errors.

The above-indicated ones are those for which the Eurocode 1 Part 1-7: General

Actions - Accidental actions[10] gives further guidance. Other possible accidental actions are,

for instance: winds or snows in a magnitude greater than foreseeable taking account the

existing statistics, other type of explosions, plane crash, etc. In any case, voluntary actions as

arson, terrorism, etc., are excluded from the Eurocodes. Nevertheless, the general guidance

given in EN 1991-1-7 [10] can be useful even in these cases.


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Conceptually, seismic actions or fire actions are also accidental actions, but due to

their particular importance and specific way of making calculations there are specific

Eurocodes devoted to them.

The philosophy of the Eurocodes to deal with the accidental actions is that it is not

needed to design the structure in a way to sustain these extreme actions without damage.

Some damage is acceptable, but not to an extent disproportionate to the original cause.Thatis: for the sake of example, an impact of a vehicle to a column could cause the failure of this

column and the surrounding floors, but not of the whole structure.

Different strategies can be used to face accidental situations. Recommendations are

given in EN 1990 and also in EN 1991-1-7 [10] to avoid excessive damage. Potential

alternative or concurrent strategies include:

- avoiding, eliminating or reducing the hazards to which the structure can besubjected;

- selecting a structural form which has low sensitivity to the hazards considered;

- selecting a structural form and design that can survive adequately the accidental

removal of an individual member or a limited part of the structure, or the occurrenceof acceptable localised damage;

- avoiding as far as possible structural systems that can collapse without warning;

- tying the structural members together.

Chapter 5 of this Guidebookdeals with these situations in detail.

3. RELIABILITY MANAGEMENT

Evidently neither all the structures, nor every part of a structure, have the same level

of reliability, and even, for each member it also will depend on the type of the studied effect;

i.e.: the different limit state. It is not the same to analyze the failure due to the buckling of

columns (ULS) or the apparition of a crack of determined size (SLS). Indications of the

adequate level of reliability for different circumstances are given in Section 2 of EN 1990 [9].

The concept of risk analysis is not highlighted in this section, but it is clear that it is

behind all that was indicated here. The term risk is assumed to be the product of the

consequences derived from an event and the probabilities that the event occurs; i.e. the

probabilities of reaching that limit state or, in other words, the level of reliability. The

important point is to keep the risk at an acceptable level.

Unfortunately, it is easy to say to keep the risk at acceptable level, but not so easy to

verify it in practical applications. Because both terms of the statement present importantuncertainties. Firstly, as it is difficult to quantify the existing risk, a comprehensive set of

scenarios encompassing all significant events has to be analysed. And, secondly, the exact

knowledge of what is a quantified acceptable level of risk is hardly to be achieved.

In practical applications, the codes, and so do the Eurocodes, assume an implicit

acceptable risk and, for each Limit State, assume, also, a level of average foreseeable

consequences. With these assumptions in mind, the codes determine the acceptable

probabilities of failure for each Limit State (both ULS and SLS); that is: the level of

reliability.

For these considerations it is clear that the higher are the consequences of the failure

the higher has to be the level of reliability. In all the calculations it is assumed that the design

is developed following the Eurocodes 1990 to 1999 and taking care of appropriate executionand quality management measures.


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The choice of design working life will depend on the economic or social importance

of the structure. Indicative values are given for different types of civil and building structures

in EN 1990 [9]. More detailed information may be given in the National Annex. For each

particular case, the design working life can be established by an agreement between the

owner, the National Authorities and the designer.

Structures not included in the scope of the Eurocodes (e.g. dams, tunnels, nuclearpower plants, etc.) could be designed for different design working lives, even longer than

those indicative values given in Table 1.

Table 1: Indicative design working life

Design

working life

category

Indicative

design working

life (years)

Examples

1 10 Temporary structures (1)

2 10-25 Replaceable structural parts, e.g. gantry

girders, bearings3 15-30 Agricultural and similar structures

4 50 Building structures and other common

structures

5 100 Monumental building structures, bridges,

and other civil engineering structures

(1) Structures or parts of structures that can be dismantled with a view of being

re-used should not be considered as temporary.

5. DURABILITY

The ISO/DIS 13823 [8] defines the term durability as:the capability of a structure or

any component to satisfy with planned maintenance the design performance requirements

over a specified period of time under the influence of the environmental actions, or as a result

of a self-ageing process.

Structures, as everything, deteriorate with time adversely influencing their performance.

There are multiple actions affecting the durability of the structure depending mainly on its

materials. The most important of them refer to presence of water moisture with or without

contaminants. The rate of deterioration depends on the environmental conditions, the chosenmaterials and the quality in the design, execution and maintenance.

The requirement in this point is that the structure shall be designed so that deterioration

over its design working life does not impair the performance of the structure below that

intended, having due regard to its environment and the anticipated level of maintenance.

In this point, maintenance has to be understood as the total set of activities (including

inspection, cleaning and repair) performed during the design service life of a structure to

preserve the appropriate structural performance [8].

In order to achieve an adequately durable structure, the following should be taken into

account:

the intended or foreseeable use of the structure; the required design criteria; the expected environmental conditions;

the composition, properties and performance of the materials and products; the properties of the soil;


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the choice of the structural system; the shape of members and the structural detailing; the quality of workmanship, and the level of control; the particular protective measures; the intended maintenance during the design working life.

The Figure 1, adopted from [6] gives an indication on how a structure can perform intime. We can take the performance as a quantitative variable defining the behaviour of the

structure. Once the structure is in use (even before), it starts to deteriorate, and, therefore, to

decrease the value of the chosen variable performance. If we do not take any other measure

that the normal maintenance, the performance after a time, longer or shorter, will reach the

nominal Serviceability Limit State (SLS), defining what would be the actual working life of

the structure. If, even in this point, no measures are taken, the structure will keep on

deteriorating reaching the Ultimate Limit State (ULS) and, eventually, the actual failure of the

structure.

If repairs are undertaken in some points in time of the working life of the structure,

before the SLS is reached, punctual increases of the performance value can be obtained, in

general the performance will keep under the original value, allowing to have a longer workinglife for the structure.

Figure 1. Working life with and without repairs

6. QUALITY MANAGEMENT

Quality management has three main components: quality control, quality assurance

and quality improvement. Quality management is focused not only on product quality, but

also the means to achieve it.

The structure as built has to fulfil all the requirements and the assumptions adopted in

the design phase. To assure this, appropriate quality management measures should be inplace. These measures comprise:


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definition of the reliability requirements, organisational measures and controls at the stages of design, execution, use and maintenance.

REFERENCES

[1] Construction Products Directive (Council Directive 89/106/EEC) . European

Commission, Enterprise Directorate-General, 2003

http://ec.europa.eu/enterprise/construction/internal/cpd/cpd.htm

[2] Interpretative document No. 1: Mechanical resistance and stability. European

Commission, Enterprise Directorate-General, 2004

http://ec.europa.eu/enterprise/construction/internal/intdoc/idoc1.htm

[4] Guidance Paper L (concerning the Construction Products Directive - 89/106/EEC) -

Application and Use of Eurocodes: European Commission, Enterprise Directorate-General,

2004. http://ec.europa.eu/enterprise/construction/internal/guidpap/europart1.htm

[5] Handbook 1. Basis of Structural Design. Leonardo da Vinci Pilot Project CZ/02/B/F/PP-

134007. Gaston, UK. 2004

[6] Gulvanessian, H., Calgaro, J.-A., Holick, M.: Designer's Guide to EN 1990, Eurocode:

Basis of Structural Design; Thomas Telford, London, 2002, 192 pp.

[7] ISO 834 Part 1

[8] ISO/DIS 13823, general Principles on the Design of Structures for Durability, Geneva

2006

[9] EN 1990 Eurocode: Basis of structural design. European Committee for Standardisation,

04/2002.

[10] EN 1991-1-7 Eurocode 1: Actions on structures Part 1-1: General actions Accidentalactions, European Committee for Standardisation, 2006.


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APPENDIX A: REFERENCE DOCUMENTS

A.1 Introduction

In order to better understand what the Essential Requirements express, the most important

items of the documents and their backgrounds are described as follows. The full text of the

documents can be easily obtained from the European Committee web page indicated in thereferences.

A.2 Construction Products Directive

The construction products directive (Council Directive 89/106/EEC) Council Directive

89/106/EEC of 21 December 1988 on the approximation of laws, regulations and

administrative provisions of the Member States relating to construction products

(89/106/EEC) (OJ L 40, 11.2.1989, p.12) amended by: Council Directive 93/68/EEC of 22

July 1993 (OJ L 220, 30.8.1993, p.1) and Regulation (EC) No 1882/2003 of the European

Parliament and of the Council of 29 September 2003 (OJ L 284, 31.10.2003, p.1)

A.2.1 Annex I: Essential requirements

The products must be suitable for construction works, which (as a whole and in their separateparts) are fit for their intended use, account being taken of economy, and in this connection

satisfying the following essential requirements where the works are subjected to regulations

containing such requirements. Such requirements shall, under normal maintenance, be

satisfied for an economically reasonable working life. The requirements generally concern

actions which are foreseeable.

Mechanical resistance and stability

The construction works must be designed and built in such a way that the loadings that are

liable to act on it during its constructions and use will not lead to any of the following:

(a) collapse of the whole or part of the work;

(b) major deformations to an inadmissible degree;

(c) damage to other parts of the works, fittings or installed equipment due to deformation of

the load-bearing structures;

(d) damage by an event to an extent disproportionate to the original cause.

Safety in case of fireThe construction works must be designed and built in such a way that in the event of an

outbreak of fire:

- the load-bearing capacity of the construction can be assumed for a specific period of time,- the generation and spread of fire and smoke within the works are limited,

- the spread of the fire to neighbouring construction works is limited,

- occupants can leave the works or be rescued by other means.

- the safety of rescue teams is taken into consideration.

Hygiene, health and the environment

The construction work must be designed and built in such a way that it will not be a threat to

the hygiene or health of the occupants or neighbours, in particular as a result of any of the

following:

- the giving-off toxic gas,

- the presence of dangerous particles or gases in the air.- the emission of dangerous radiation


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- pollution or poisoning of water or soil,- faulty elimination of waste water, smoke, solid or liquid wastes,- the presence of damp in parts of the works or on surfaces within the works.

Safety in use

The construction work must be designed and built in such a way that it does not presentunacceptable risks of accidents in service or in operation such as slipping, falling, collision,

burns, electrocution, injury from explosion.

Protection against noise

The construction works must be designed and built in such a way that noise perceived by the

occupants or people nearby is kept down to a level that will not threaten their health and will

allow them to sleep, rest and work in satisfactory conditions.

Energy economy and heat retention

The construction works and its heating, cooling and ventilation installations must be designed

and built in such a way that the amount of energy required in use shall be low, having regardto the climatic conditions of the location and the occupants.

A.3 Interpretative document No. 1 Mechanical resistance and stability

A.3.1 Purpose and scope of Interpretative document No. 1

(1) This Interpretative Document relates to Council Directive 89/106/EEC of 21 December

1988 on the approximation of laws, regulations and administrative provisions of the Member

States relating to construction products, hereinafter referred to as the Directive.

(2) Article 3 of the Directive stipulates that the purpose of the Interpretative Documents is to

give concrete form to the essential requirements for the creation of the necessary linksbetween the essential requirements set out in Annex I to the Directive and the mandates for

the preparation of harmonized standards and guidelines for European technical approvals or

the recognition of other technical specifications within the meaning of Articles 4 and 5 of the

Directive.

Where considered necessary, the provisions of this Interpretative Document will be further

specified in each particular mandate. In drafting the mandates, account will be taken, if

necessary, of the other essential requirements of the Directive, as well as of other relevant

Directives concerning construction products.

(3) This Interpretative Document deals with the aspects of the works where Mechanical

resistance and stability may be concerned. It identifies products or product families andcharacteristics relating to their satisfactory performance.

The construction works must be designed and built in such a way that the loadings that are

liable to act on it during its construction and use will not lead to any of the following:

a) collapse of the whole or part of the works;

b) major deformations to an inadmissible degree;

c) damage to other parts of the works or to fittings or installed equipment as a result of major

deformation of the load-bearing construction;

d) damage by an event to an extent disproportionate to the original cause.


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4) In accordance with the Council Resolution of 7 May 1985 (New Approach) and the

preamble of the Directive, this interpretation of the essential requirement is intended not to

reduce the existing and justified levels of protection for works in the Member States.

A.3.2 Meaning of the general terms used in the Interpretative documents.

Construction works

Construction works means everything that is constructed or results from construction

operations and is fixed to the ground. This term covers both buildings and civil engineering

works. In the Interpretative Documents "construction works" are also referred to as the

"works". Construction works include for example: dwellings; industrial, commercial, office,

health, educational, recreational and agricultural buildings; bridges; roads and highways;

railways; pipe networks; stadiums; swimming pools; wharfs; platforms; docks; locks;

channels; dams; towers; tanks; tunnels; etc.

Construction products

(1) This term refers to products which are produced for incorporation in a permanent mannerin the works and placed as such on the market. The terms "construction products" or

"products", where used in the Interpretative Documents, include materials, elements and

components (single or in a kit) of prefabricated systems or installations which enable the

works to meet the essential requirements.

(2) Incorporation of a product in a permanent manner in the works means:

- that its removal reduces the performance capabilities of the works; and

- that the dismantling or the replacement of the product are operations which involve

construction activities.

Normal maintenance

(1) Maintenance is a set of preventive and other measures which are applied to the works

in order to enable the works to fulfil all its functions during its working life. These measures

include cleaning, servicing, repainting, repairing, replacing parts of the works where needed,

etc.

(2) Normal maintenance generally includes inspections and occurs at a time when the costs of

the intervention which has to be made are not disproportionate to the value of the part of the

works concerned, consequential costs being taken into account.

Intended useThe intended use of a product refers to the role(s) that the product is intended to play in the

fulfilment of the essential requirements.

Economically reasonable working life(1) The working life is the period of time during which the performance of the works will be

maintained at a level compatible with the fulfilment of the essential requirements.

(2) An economically reasonable working life presumes that all relevant aspects are taken into

account, such as:

- costs of design, construction and use;

- costs arising from hindrance of use;

- risks and consequences of failure of the works during its working life and costs of insurance

covering these risks;

- planned partial renewal;

- costs of inspections, maintenance, care and repair;- costs of operation and administration;


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- disposal;

- environmental aspects.

Actions

Actions which may affect the compliance of the works with the essential requirements are

brought about by agents acting on the works or parts of the works. Such agents includemechanical, chemical, biological, thermal and electro-magnetic agents.

Performance

Performance is a quantitative expression (value, grade, class or level) of the behaviour of a

works, part of the works or product, for an action to which it is subject or which it generates

under the intended service conditions (for the works or parts of works) or intended use

conditions (for products).

A.3.3. Basis for verification of the satisfaction of the essential requirement "Mechanical

resistance and stability".

General

(1) This chapter identifies basic principles prevailing in Member States for the verification of

the satisfaction of the essential requirement "Mechanical resistance and stability". These

principles are currently complied with when and where the works are subject to regulations

containing this essential requirement.

(2) The essential requirement, as far as applicable, is satisfied with acceptable probability

during an economically reasonable working life of the works.

(3) The satisfaction of the essential requirement is assured by a number of interrelated

measures concerned in particular with:

- the planning and design of the works, the execution of the works and necessary

maintenance;- the properties, performances and use of the construction products.

(4) It is up to the Member States, when and where they feel it necessary, to take measures

concerning the supervision of planning, design and execution of the works, and concerning

the qualifications of parties and persons involved. Where this supervision and this control of

qualifications are directly connected with the characteristics of products, the relevant

provisions shall be laid down in the context of the mandate for the preparation of the

standards and guidelines for European technical approval related to the products concerned.

A.3.4. Working life and durability.

1 Treatment of working life of construction works in relation to the essential requirement(1) It is up to the Member States, when and where they feel it necessary, to take measures

concerning the working life which can be considered reasonable for each type of works, or for

some of them, or for parts of the works, in relation to the satisfaction of the essential

requirements.

(2) Where provisions concerning the durability of works in relation to the essential

requirement are connected with the characteristics of products, the mandates for the

preparation of the European standards and guidelines for European technical approvals,

related to these products, will also cover durability aspects.


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A.4 GUIDANCE PAPER L

A.4.1. Eurocodes Part 1: General

1.1 Aims and benefits of the Eurocode programme

The Eurocodes provide common design methods, expressed in a set of European standards,which are intended to be used as reference documents for Member States to:

prove the compliance of building and civil engineering works or parts thereof withEssential Requirement n1 Mechanical resistance and stability (including such aspects of

Essential Requirement n4 Safety in use, which relate to mechanical resistance and

stability) and a part of Essential Requirement n2 Safety in case of fire, including

durability, as defined in Annex 1 of the CPD

express in technical terms these Essential Requirements applicable to the works and parts

thereof;

determine the performance of structural components and kits with regard to mechanical

resistance and stability and resistance to fire, insofar as it is part of the informationaccompanying CE marking (e.g. declared values).

1.1.2 EN Eurocodes are intended by the European Commission services, and the Member

States, to become the European recommended means for the structural design of works and

parts thereof, to facilitate the exchange of construction services (construction works and

related engineering services) and to improve the functioning of the internal market.

1.1.3 The intended benefits and opportunities of Eurocodes are to:

provide common design criteria and methods to fulfil the specified requirements for

mechanical resistance, stability and resistance to fire, including aspects of durability and

economy,provide a common understanding regarding the design of structures between owners,

operators and users, designers, contractors and manufacturers of construction products

facilitate the exchange of construction services between Members States,

facilitate the marketing and use of structural components and kits in Members States,

facilitate the marketing and use of materials and constituent products, the properties of which

enter into design calculations, in Members States,

be a common basis for research and development, in the construction sector,

allow the preparation of common design aids and software,

increase the competitiveness of the European civil engineering firms, contractors, designers

and product manufacturers in their world-wide activities.

1.2 Background of the Eurocode programme

1.3 Objectives of the Guidance Paper

1.3.1 This Guidance Paper expresses, with the view of achieving the aims and benefits of the

Eurocode programme mentioned in 1.1, the common understanding of the Commission and

the Member States on:

The application of EN Eurocodes in the structural design of works (chapter 2).

The use of EN Eurocodes in harmonised standards and European technical approvals for

structural construction products (chapter 3). A distinction is made between:


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a) products with properties which enter into structural calculations of works, or otherwise

relate to their mechanical resistance and stability, including aspects of durability and

serviceability, and which for this reason should be consistent with the assumptions and

provisions made in the EN Eurocodes ("structural materials" are the most concerned - see

chapter 3.2)

b) products with properties which can directly be determined by methods used for thestructural design of works, and thus should be determined according to the EN Eurocode

methods (prefabricated "structural components and kits" are the most concerned - see chapter

3.3).

A.4.2. Eurocodes Part 2: Use of EN Eurocodes for structural design of works

2.1 National Provisions for the structural design of works

2.1.1 The determination of the levels of safety [The word safety is encompassed in the

Eurocodes in the word reliability] of buildings and civil engineering works and parts thereof,

including aspects of durability and economy [The introductory provisions of Annex I of theCPD lay down: "The products must be suitable for construction works which (as a whole and

in their separate parts) are fit for their intended use, account being taken of economy, and in

this connection satisfy the following essential requirements where the works are subject to

regulations containing such requirements. Such requirements must, subject to normal

maintenance, be satisfied for an economically reasonable working life. The requirements

generally concern actions which are foreseeable." Economic aspects remain within the

competence of the Member States.

2.1.2 Possible differences in geographical or climatic conditions (e.g. wind or snow), or in

ways of life, as well as different levels of protection that may prevail at national, regional or

local level in the sense of article 3.2 of the CPD.

2.1.3 When Member States lay down their Nationally Determined Parameters, they should:

choose from the classes included in the EN Eurocodes, or

use the recommended value, or choose a value within the recommended range of values, for a

symbol where the EN Eurocodes make a recommendation, or

when alternative methods are given, use the recommended method, where the EN Eurocodes

make a recommendation,

take into account the need for coherence of the Nationally Determined Parameters laid down

for the different EN Eurocodes and the various Parts thereof.

Member States are encouraged to co-operate in minimising the number of cases where

recommendations for a value or method are not adopted for their nationally determinedparameters. By choosing the same values and methods, the Member States will enhance the

benefits listed in 1.1.3.

2.1.4 The Nationally Determined Parameters laid down in a Member State should be made

clearly known to the users of the EN Eurocodes and other parties concerned, including

manufacturers.

2.1.5 When the EN Eurocodes are used for the design of construction works, or parts thereof,

the Nationally Determined Parameters of the Member State on whose territory the works are

located shall be applied.


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Note: Any reference to an EN Eurocode design should include the information on which set

of Nationally Determined Parameters was used, whether or not the Nationally Determined

Parameters that were used correspond to the recommendations given in the EN Eurocodes

(see 2.1.3).

2.1.6 National Provisions should avoid replacing any EN Eurocode provisions, e.g.

Application Rules, by national rules (codes, standards, regulatory provisions, etc.).

When, however, National Provisions do provide that the designer may even after the end of

the coexistence period - deviate from or not apply the EN Eurocodes or certain provisions

thereof (e.g. Application Rules), then the design will not be called "a design according to EN

Eurocodes".

2.1.7 When Eurocode Parts are published as European standards, they will become part of the

application of the Public Procurement Directive.

In all cases, technical specifications shall be formulated in public tender enquiries and public

contracts by referring to EN Eurocodes, in combination with the Nationally Determined

Parameters applicable to the works concerned, apart from the exceptions expressed in article10.3 (Directive 93/37, article 10.2).

However, in application of the PPD, and following the spirit of the New Approach, the

reference to EN Eurocodes is not necessarily the only possible reference allowed in a Public

contract. The PPD foresees the possibility for the procuring entity to accept other proposals, if

their equivalence to the EN Eurocodes can be demonstrated by the contractor.

Consequently, the design of works proposed in response to a Public tender can be prepared

according to:

EN Eurocodes (including NDPs), which give a presumption of conformity with all legal

European requirements concerning mechanical resistance and stability, fire resistance and

durability, in compliance with the technical specifications required in the contract for the

works concerned;

Other provisions expressing the required technical specification in terms of performance. In

this case, the technical specification should be detailed enough to allow tenders to know the

conditions on which the offer can be made and the owner to choose the preferred offer. This

applies, in particular, to the use of national codes, as long as Member States maintain their use

in parallel with EN Eurocodes (e.g. a Design Code provided by National Provisions), if also

specified to be acceptable as an alternative to an EN Eurocode Part by the Public tender.

2.2 Indications to writers of EN Eurocodes

2.3 National Annexes of the EN Eurocode Parts

2.3.1 When a Eurocode Part is circulated by CEN for publication as an EN, the final text ofthe approved EN, according to CEN rules, is made available by CEN Management Centre to

CEN members (the NSBs) in the 3 official languages (English, French and German).[This

step corresponds to the DAV Date of Availability]

Each NSB shall implement this EN as a national standard by publication of an equivalent text

(i.e. a version translated into another language) or by endorsement of one of the 3 language

versions provided by CEN Management Centre (by attaching an "endorsement sheet"), within

the timescale agreed for publication.

The National standard transposing the EN Eurocode Part, when published by a National

Standards Body (NSB), will be composed of the EN Eurocode text (which may be preceded

by a National title page and by a National Foreword), generally followed by a NationalAnnex.


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2.3.2 The National Standards Bodies should normally publish a National Annex, on behalf of

and with the agreement of the national competent authorities.

A National Annex is not necessary if an EN Eurocode Part contains no choice open for

Nationally Determined Parameters, or if an EN Eurocode Part is not relevant for the Member

State (e.g. seismic design for some countries).

Note: As stated by the CEN Rules, the National Annex is not a CEN requirement (a NSB can

publish an EN Eurocode Part without one). However, in the context of this Guidance Paper,

the National Annex serves for NSBs to publish the Nationally Determined Parameters, which

will be essential for design.

2.3.3 The National Annex may contain [See EN 1990 and EN 1991 Part 1-1 Foreword

National standards implementing Eurocodes], directly or by reference to specific provisions,

information on those parameters which are left open in the Eurocodes for national choice, the

Nationally Determined Parameters, to be used for the design of buildings and civil

engineering works to be constructed in the country concerned, i.e:

values and/or classes where alternatives are given in the EN Eurocode,values to be used where a symbol only is given in the EN Eurocode,

country specific data (geographical, climatic, etc.), e.g. a snow map,

the procedure to be used where alternative procedures are given in the EN Eurocode.

It may also contain the following:

decisions on the application of informative annexes, and,

reference to non-contradictory complementary information to assist the user in applying the

Eurocode.

2.3.4 A National Annex cannot change or modify the content of the EN Eurocode text in anyway other than where it indicates that national choices may be made by means of Nationally

Determined Parameters.

2.3.5 The National Annex of an EN Eurocode Part will normally be finalised when the safety

and economy levels have been considered, i.e. at the end of the period allocated for the

establishment of the Nationally Determined Parameters (see Annex A).

2.3.6 If a Member State does not choose any NDPs, the choice of the relevant values (e.g. the

recommended value), classes or alternative method will be the responsibility of the designer,

taking into account the conditions of the project and the National provisions.

2.3.7 The National Annex has an informative status. The content of a National Annex can be

the basis for a national standard, via the NSB, and/or can be referred to in a NationalRegulation.

2.3.8 The National Annex can be amended, if necessary, according to CEN rules.

2.4 Packages of EN Eurocode Parts

2.4.1 The purpose of defining Packages, by grouping Parts of EN Eurocode, is to enable a

common date of withdrawal (DoW) [At the date of withdrawal related to a new standard, all

the specifications existing previously in the National collection of standards conflicting with

the new standard have to be withdrawn and the national provisions have to be adapted to

allow the legitimate use of EN Eurocodes] for all of the relevant parts that are needed for a

particular design. Thus conflicting national standards shall have been withdrawn at the end ofthe coexistence period, after all of the EN Eurocodes of a Package are available, and National


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Provisions will have been adapted by the end of the National Calibration period, as described

in Annex A. Publication of the individual Parts in a Package is likely to occur over a long

period of time, so that, for many Parts, the coexistence period will be much longer than the

minimum given in 2.5.5. When a National standard has a wider scope than the conflicting

Eurocode Package, only that part of the National standard whose scope is covered by the

Package has to be withdrawn.When more than one Package of EN Eurocodes is likely to be needed for the design of works,

the dates of withdrawal of the related Packages can be synchronised.

2.4.2 No Parts from EN 1990 or the EN 1991, EN 1997 or EN 1998 series form a Package in

themselves; those Parts are placed in each of the Packages, as they are material independent.

2.4.3 The list of the EN Eurocode Parts contained in the various Packages for each of the

main materials, i.e. concrete, steel, composite concrete and steel, timber, masonry and

aluminium, and their respective target dates, will be updated and made available through the

CEN/MC web-site (see Annex C which presents the Packages as they are currently foreseen)

2.5 Arrangements for the implementation of EN Eurocodes and period of co-existence

with national rules for the structural design of works

2.5.1 The arrangements for the implementation of an EN Eurocode Part include, from the time

the final draft of the EN Eurocode is produced by the CEN/TC250, five periods:

- Two periods before the date of availability (DAV):

Examination period,

CEN process period.

- Three periods after the date of availability:

Translation period,

National calibration period,

Coexistence period.

The detailed content of each of the five periods is given in the table and chart in Annex A.

The progress of each EN Eurocode (or Package), within these periods, will be provided by

CEN/MC on their web-site.

2.5.2 The following basic requirements need to be fulfilled by the EN Eurocode Parts in order

to be referred to in the national provisions:

- Calculations executed on the basis of the Eurocode Part, in combination with the Nationally

Determined Parameters, shall provide an acceptable level of safety.

- The use of the EN Eurocode Part, in combination with the Nationally Determined

Parameters, does not lead to structures that cost significantly more, over their working life

[see Interpretative Document 1, clause 1.3.5], than those designed according to Nationalstandards or provisions, unless changes in safety have been made and agreed.

2.5.3 The European Commission encourages Member States to implement EN Eurocodes in

the framework of their National Provisions. During the coexistence period, the construction

regulation authorities should accept the use of EN Eurocodes, as an alternative to the previous

rules (e.g. National codes, standards or other technical rules included, or referred to, in

national provisions) for the design of construction works. Member States are also encouraged

to adapt their national provisions to withdraw conflicting national rules before the end of the

co-existence period.

2.5.4 When an EN Eurocode Part is made available, the Member States should:

- set officially, before the end of the National calibration period (see Annex A), the NationallyDetermined Parameters to be applied on their territory. In the event of any unexpected


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obstacles to carrying out the calibration of an EN Eurocode Part, the Member State shall

inform the Commission, when an extension of the period could be agreed by the SCC.

- adapt, as far as necessary, their National Provisions so that the EN Eurocode Part can be

used on their territory:

- as a means to prove compliance of construction works with the national requirements for

"mechanical resistance and stability" and "resistance to fire", in the sense of Annex I of theCPD, and

- as a basis for specifying contracts for the execution of public construction works and related

engineering services. If no NDPs are to be produced for an EN Eurocode Part, the co-

existence period begins at DAV and ends at DoW. Thus the EN Eurocode is available and any

existing national standard is still available, so that both can be used during this period.

At the end of the "coexistence period" of the last EN Eurocode Part of a Package, the Member

States should have adapted all their National Provisions which lay down (or refer to) design

rules within the scope of the relevant Package.

2.5.5 Owing to the need for operational Packages (as defined in 2.4), the reference to the

coexistence period of a Package is defined as the coexistence period of the last Eurocode Part

of that Package. In Member States intending to implement EN Eurocodes, the coexistence

period of this last part should be three years. After the three years coexistence period of the

last EN Eurocode Part of a Package, the whole Package-related former conflicting national

standards will be withdrawn, i.e. 5 years maximum after DAV [It is intended that the end of

the coexistence period for each Package will be laid down by the Commission after

consultation of Member States]. Conflicting National Provisions that would not allow the use

of the first parts of a Package should be arranged, in order to allow the legitimate use of those

Parts.

2.5.6 In order to increase the overall transparency of the implementation of the EN Eurocodes,

the Commission wishes to be informed, by the Member States, of the main phases:

translation, national calibration and coexistence Period, for each EN Eurocode Part, and theadaptation of National Provisions.

Note: the Commission intends to prepare, for this purpose, a "test reporting form" on the basis

of the items mentioned in the Annex B.

A.4.3. Eurocodes Part 3: Use of EN Eurocodes in technical specifications for structural

products

This part of the Guidance Paper deals with structural products specified in the CPD as

construction products:

3.1 Distinction is made between specifications for materials to be determined by test and

specifications for components to be determined by calculation.3.1.1 It follows from the CPD [Article 2.1 and 3.3] and the Interpretative Documents that

there is a need for consistency between the technical specifications for construction products

(hEN and ETA) and the technical rules for works.

3.1.2 For construction products, which contribute to the mechanical resistance and stability

and/or fire resistance of works, two types of properties are distinguished, according to the

validation method:

Properties to be determined by testing (generally in the case of structural materials and

constituent products, such as concrete, reinforcing steel for concrete, fire protection material,

etc.), and

Properties to be determined by calculation following methods, which are also used for the

structural design of works (generally for prefabricated structural components and kits,


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consisting of structural components, such as prefabricated concrete components, prefabricated

stairs, timber frame buildings kits, etc.).

For both types of product properties the resulting values are to be "declared" in the

information accompanying the CE marking [by application of CPD and in conformity with

the mandate given by the Commission] of the product and used in the structural design of

works or parts thereof.3.1.3 For the reference to, or use of, EN Eurocodes in harmonised product specifications a

distinction is made in this Part 3 between:

- structural materials and constituent products with properties to be determined by testing, and

- prefabricated structural components and kits consisting of structural components with

properties to be calculated according to EN Eurocode methods.

A.4.4. Eurocodes Part 4: Future actions related to the Eurocode Programme

4.1 Education

4.1.1 To build on the strong pedigree of the EN Eurocodes described above, the Commission

recognises the importance of building on this with programmes of education to help theprofessions to implement the EN Eurocodes.

4.1.2 Aspects of education that need to be covered, include:

informing and making the profession as a whole aware of the EN Eurocodes

providing continuing professional development and training to the profession encouraging the production of handbooks, design aids, software etc. to facilitate the

implementation of the EN Eurocodes

encouraging Universities and Technical Colleges to base their teaching of civil andstructural engineering design on the EN Eurocodes.

4.1.3 The Commission, in liaison with industry and Member States, will encourage:

publication of easily understandable "jargon free" booklets covering the ENEurocodes;

holding of European seminars aimed at the profession as a whole as key ENEurocodes become available as ENs (e.g. EN 1990:Basis of Design);

publication of documents on the adoption of the EN Eurocodes through Governmentor on behalf of Government;

holding of meetings organised by professional and industry bodies to informconstruction professionals and university teachers, to listen to and discuss their

concerns, and to promote the opportunities offered by the EN Eurocodes;

the arrangement of continuing professional development and training courses; the development of aids to implementation.

4.1.4 Central to any initiatives taken on education is the production of :

handbooks, worked examples and background documents; software; guides for everyday structures (e.g. normal buildings) based on the EN Eurocodes.

Publishing companies, software houses and trade organisations will carry out these important

activities, mainly as commercial ventures. Encouragement to these bodies can be given by a

strong commitment to implementation of the EN Eurocodes both by the EC and the Member

States.

4.1.5 Member States should encourage the use of the EN Eurocodes in private contracts,

particularly through education and information campaigns, regardless of what may be

requested by National provisions.


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4.2. Research with regard to EN Eurocodes

4.2.1 The Commission services recognises that, for the Construction sector to remain

competitive in the world construction industry, it is essential that the EN Eurocodes, once

published, should remain the most up to date, useable International Codes of Practice,

meeting the requirements for a profession practising in a competitive environment.

4.2.2 The EN Eurocodes should be further developed taking into account the innovative

pressures of the market and the progress of scientific knowledge.

4.2.3 The pressures from the market are generated by:

new material and new products; new ways for procurement and execution of works; needs for economy whilst maintaining acceptable levels of safety.

The progress of the scientific knowledge and methods are generated by:

the need to avoid disasters in the area of safety (e.g. seismic, fire); a knowledge of phenomena acquired in other domains (e.g. aeronautics for wind

action);

the answer to new economic or social needs (e.g. High Speed Railways, nuclearplants);

the availability of powerful and widely-distributed tools for calculation (computersand software).

4.2.4 Initiatives for research arise from

the industry or the users concerned; public authorities in charge of safety, economy, scientific development and education

(for example, the development of NDPs)

universities and research organisations experienced from their involvement as third

parties.

4.2.5 In many cases there will be a mutual interest for both industry and public authorities

(including the European Commission) in research and this should be reflected by agreements

on common funding according to the following criteria:

Industrial and user's sources - the main funding for research whose objectives areshort-term benefits or particular advantages for special innovative companies and

associated industries and users (e.g. unique verifications and ETA's).

EC or National public funding - the main funding for research whose objectives aremedium to long term benefits for the European construction industry (e.g. for

improving technical specifications and design codes, harmonising models for actions

and resistances, improving safety aspects).

4.3. Maintenance of EN Eurocodes

4.3.1 The maintenance of the EN Eurocodes is essential; the need for updating, revision and

completion is strongly recognised so that an improved second generation of EN Eurocodes

can evolve. However, a period of stability should be observed before embarking on changes

other than to correct errors.

4.3.2 Maintenance work will involve:

reducing open choices (NDPs); urgent matters of health and safety;

correcting errors;


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ensuring the most up to date information is in the EN Eurocodes, recognising recentproven innovations and improvements in construction technology;

feedback from use of the EN Eurocodes in the various Member States through CEN; requests from industrial organisations or public authorities to CEN members for

revision.

4.3.3 The organisation of maintenance should start after the receipt of a positive vote on adraft EN Eurocode, a Maintenance Group should be formed by the relevant CEN/TC250 SC

to:

give further consideration of co-ordination items arising from the work of otherProject Teams (this is necessary as the various parts of the EN Eurocodes are not

being prepared simultaneously);

provide explanations to questions arising from the use of the EN Eurocode, e.g. onbackground and interpretation of rules;

collect comments and requests for amendment; prepare action plans for urgent revision in the case of safety related matters, or future

systematic revisions according to the CEN procedure and as decided by CEN/TC250.

4.3.4 The strategy to provide adequate resources to support the maintenance of the EN

Eurocodes should be decided by the European Commission, Member States, Industry and

CEN seeking to find a balance between:

the requirements for public safety; the competitive demands of industry; the availability of funds.


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Chapter 2: Basis of design general principles

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CHAPTER 2: BASIS OF DESIGN GENERAL PRINCIPLES

Milan Holick1, Jana Markov

1

1Klokner Institute, Czech Technical University in Prague, Czech Republic

Summary

Construction works are complicated technical systems suffering from a number of

significant uncertainties in all stages of execution and use. Reliability is therefore an

important aspect of their design. The most important historical methods include method of

permissible stresses and method of global and partial factors. Present European standard

EN 1990 Eurocode - Basis of structural is based on the concept of limit states in conjunction

with partial factor method. Probabilistic approach and methods of risk assessment are used as

scientific bases of the partial factor method and as an alternative design method.

1 INTRODUCTION

1.1 Background documents

The standard EN 1990 Basis of structural design [1] and EN 1991-1-1 Actions on

structures [2] are the fundamental documents for the whole system of Eurocodes. These

documents are available since April 2002 and at present are implemented into the systems of

national standards. An important background document is the International Standard

ISO 2394 [3], Probabilistic Model Code [5], Designer's Guide to EN 1990 [5] and otherliterature (for example [6]).

1.2 General principles

Two basic sets of limit states should be considered in accordance to the design

principles of EN 1990 [1]. Particularly it should be verified that the load effect E does not

exceed the resistance of the structure in ultimate limit states and the relevant criteria for

serviceability limit states. In common cases the general condition of structural performance

with respect to ultimate or serviceability limit states may be expressed by the following

inequality

E


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Basic concepts of historical development and various design methods are shortly

described in the following section.

2 HISTORICAL DEVELOPMENT

2.1 Uncertainties

It is well recognised that construction works are complicated technical systems

suffering from a number of significant uncertainties in all stages of execution and use. Some

uncertainties can never be eliminated absolutely and must be taken into account when

designing or verifying construction works. Depending on the nature of a structure,

environmental conditions and applied actions, some types of uncertainties may become

critical. The following types of uncertainties can usually be identified:

- natural randomness of actions, material properties and geometric data;

- statistical uncertainties due to a limited size of available data;

- uncertainties of theoretical models caused by a simplification of actual conditions;

- vagueness due to inaccurate definitions of performance requirements;

- gross errors in design, execution and operation of the structure;

- lack of knowledge of the behaviour of new materials in real conditions.

Note that the order of the listed uncertainties corresponds approximately to the

decreasing amount of current knowledge and available theoretical tools to analyse them and to

take them into account in design.

The natural randomness and statistical uncertainties may be relatively well described

by available methods of the theory of probability and mathematical statistics. In fact the

Eurocode [1] and the International Standard [3] provide some guidance on how to proceed.

However, lack of reliable experimental data, i.e. statistical uncertainty, particularly in case of

new materials, some actions including environmental influences and also some geometricaldata, cause significant problems. Moreover, the available data are often inhomogeneous and

obtained under different conditions (for example for material properties, imposed loads,

environmental influences, but also for internal dimensions of reinforced concrete cross-

sections). Then it may be difficult, if not impossible, to analyse such data and to use them in

design.

Uncertainties of theoretical models may be, to a certain extent, assessed on the basis of

theoretical and experimental research. Again the Standards [1, 3] provide some guidance on

how to proceed. The vagueness caused by inaccurate definitions (in particular of

serviceability and other performance requirements) may be partially described by the theory

of fuzzy sets. However, up to now these methods have a little practical significance, as

convincing theoretical models are rarely available. The knowledge of the behaviour of newmaterials and structures may gradually increase due to newly developed theoretical tools and

experimental research.

The lack of available theoretical tools is obvious in the case of gross errors and lack of

knowledge, which are nevertheless often the decisive causes of structural failures. To limit

gross errors due to human activity a quality management system including the methods of

statistical inspection and control may be effectively applied.

Several design methods and operational techniques have been proposed and world-

wide used to control the unfavourable effect of various uncertainties during a specified

working life. Simultaneously the theory of structural reliability has been developed to

describe and analyse the above-mentioned uncertainties in a rational way and to take them

into account in design and verification of structural performance. In fact the development ofthe whole theory was initiated by observed insufficiencies and structural failures caused by


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various uncertainties. At present the theory of structural reliability is extensively used to

calibrate reliability elements of newly proposed standards (partial and various reduction

factors). The term "reliability" itself is, however, often used in a very broad sense and may

need some clarification.

2.2 Definition of reliability

The term reliability is often simplified and used very vaguely and inaccurately. The

concept of reliability is sometimes approached in an absolute (black and white) way the

structure either is or isnt reliable. In accordance with this approach the positive statement is

understood as the failure of the structure will never occur. This is of course an incorrect

oversimplification, the failure may occur even though the structure is correctly declared as

reliable. The interpretation of the complementary (negative) statement is usually understood

more correctly: failures are admitted and the probability or frequency of their occurrence is

then discussed. Thus according to this simplified approach there should be a certain set of

structural conditions determining an area of absolute reliability, where any possibility of

failure occurrence is excluded. Only when exceeding this limit the emergence of failure

would be admitted.

In general, such a simplified interpretation is incorrect. Although it may be unpleasant

and for many perhaps unacceptable, the hypothetical area of absolute reliability for most

structures (apart from exceptional cases) simply does not exist. On the contrary, in the design

it is necessary to admit a certain small probability that the failure may occur within the

intended life of the structure. Otherwise it would not be possible at all to design civil

structures. What is then the correct interpretation of the keyword reliability and what sense

has the generally used statement the structure is safe?

In structural design a number of similar definitions of the term reliability or their

interpretations are used in literature and in national and international documents. ISO 2394 [2]

provides a definition of reliability, which is similar to the approach of other national andinternational standards: reliability is the ability of a structure to comply with given

requirements under specified conditions during the intended life, for which it was designed.

In Eurocode [1] no definition is offered and it is only noted that reliability covers the

load-bearing capacity, serviceability as well as the durability of a structure. In the

Fundamental requirements it is then stated that a structure shall be designed and executed in

such a way that it will, during its intended life with appropriate degrees of reliability and in an

economic way:

- remain fit for the use for which it is required; and

- sustain all actions and influences likely to occur during execution and use.

Generally a different level of reliability for load-bearing capacity and for serviceability

may be accepted. In the document [1] the probability of failure pfand the reliability indexare related to failure consequences.

Note that the above definition of reliability includes four important elements:

- given (performance) requirements the definition of the structural failure,- time period the assessment of the required service-life T,- reliability level the assessment of the probability of failure pf,- conditions of use limiting input uncertainties.An accurate determination of performance requirements and thus an accurate

specification of the term failure is of primary importance. In many cases, mainly when

considering the requirements for the stability and collapse of a structure, the specification of

this term is not very complicated. In many other cases, in particular when dealing with various

requirements of occupants comfort, appearance and characteristics of the environment, theappropriate definitions of failure are dependent on vaguenesses and inaccuracies. The


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transformation of these occupants' requirements into appropriate technical quantities and

precise criteria is very hard and often leads to considerably vague conditions. In the following

the term failure is being used in a very general sense denoting simply any undesirable state of

a structure (e.g. collapse or excessive deformation), which is unambiguously given by

structural conditions.

2.3 Development of design methods

During their historical development the design methods have been closely linked to

the available empirical, experimental as well as theoretical knowledge of mechanics and the

theory of probability. The development of various empirical methods for structural design

gradually stabilised in the twentieth century on three generally used methods, which have

been, in various modifications, applied in standards for structural design till these days. In the

context of efforts to simplify the computational procedures some of these methods are

sometimes modified or rehabilitated. That is why it is useful to briefly mention these three

basic design methods and to indicate those explicit measures, which may affect the

probability of failure and structural reliability.

The first worldwide design method for civil structures is the method of permissible

stresses. It is based on the condition

max< per, where per= crit/ k (2)

where the coefficient k is assessed with regard to uncertainties in the determination of local

load effect maxand of resistance crit, and therefore may ensure with an appropriate level ofsecurity the reliability of the structure. The main insufficiency of this method is perhaps the

local verification of reliability (in the elastic range) and the impossibility to consider

separa

Guidebook-1 Load Effects on Structures

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