thomas telford DESIGNERS' GUIDE TO EUROCODE 8: DESIGN OF STRUCTURES FOR EARTHQUAKE RESISTANCE DESIGNERS' GUIDES TO THE EUROCODES

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1 DESIGNERS' GUIDES TO THE EUROCODES DESIGNERS' GUIDE TO EUROCODE 8: DESIGN OF STRUCTURES FOR EARTHQUAKE RESISTANCE DESIGNERS' GUIDE TO EN AND EN EUROCODE 8: DESIGN OF STRUCTURES FOR EARTHQUAKE RESISTANCE GENERAL RULES, SEISMIC ACTIONS, DESIGN RULES FOR BUILDINGS AND RETAINING STRUCTURES M. FARDIS, E. CARVALHO, A. ELNASHAI, E. FACCIOLl, P. PINTO and A. PLUMIER Series editor H. Gulanessian thomas telford

2 Contents Preface Aim of this guide Layout of this guide Acknowledgements Chapter 1 Introduction Scope of Eurocode Scope of Eurocode 8 - Part Scope of Eurocode 8 - Part Use of Eurocode 8 - Parts 1 and 5 with the other Eurocodes Assumptions - distinction between Principles and Application Rules Terms and definitions - symbols 3 Chapter 2 Performance requirements and compliance criteria 2.1. Performance requircments for new designs in Eurocode 8 and associated seismic hazard leels 2.2. Compliance criteria for the performance requirements and their implementation 2.2.]. Compliance criteria for damage limitation Compliance criteria for the no-(local-)collapse requirement 2.3. Exemption from the application of Eurocode Chapter 3 Seismic actions 3.1. Ground conditions Identification of ground types 3.2. Seismic action Seismic zones Basic representation of the seismic action Alternatie representations of the seismic action 3.3. Displacement response spectra Chapter 4 Design of buildings 4.1. Scope 4.2. Conception of structures for earthquake resistant buildings Structural simplicity ] 31

3 DESIGNERS' GUIDE TO EN AND EN Uniformity, symmetry and redundancy Bi-directional resistance and stiffness Torsional resistance and stiffness Diaphragmatic behaiour at the storey leel Adequate foundation Structural regularity and its implications for design Introduction Regularity in plan Regularity in eleation Combination of graity loads and other actions with the design seismic action Combination for local effects Combination for global effects Methods of analysis Oeriew of the menu of analysis methods The lateral force method of analysis Modal response spectrum analysis Linear analysis for the ertical component of the seismic action Non-linear methods of analysis Modelling of buildings for linear analysis Introduction: the leel of discretization Modelling of beams, columns and bracings Special modelling considerations for walls Cracked stiffness in concrete and masonry Accounting for second-order (P-Ll) effects Modelling of buildings for non-linear analysis General requirements for non-linear modelling Special modelling requirements for non-linear dynamic analysis The inadequacy of member models in 3D as a limitation of non-linear modelling Analysis for accidental torsional effects Aceidental eccentricity Estimation of the effects of accidental eccentricity through static analysis Simplified estimation of the effects of accidental eccentricity Combination of the effects of the components of the seismic action 'Primary' ersus 'secondary' seismic elements Definition and role of 'primary' and 'secondary' seismic elements Special requirements for the design of secondary seismic elements Verification Verification for damage limitation Verification for the no-(iocal)-collapse requirement Special rules for frame systems with masonry infills Introduction and scope Design against the aderse effects of planwise irregular infills Design against the aderse effects of heightwise irregular infills 83

4 Chapter 5 Design and detailing mies for concrete buildings Scope Types of concrete elements - definition of 'critical regions' Beams and columns Walls Ductile walls: coupled and uncoupled Large lightly reinforced walls Critical regions in ductile elements Types of structural systems for earthquake resistance of concrete buildings Inerted-pendulum systems Torsionally flexible systems Frame systems Wall systems Dual systems Systems of large lightly reinforced walls Design concepts: design for strength or for ductility and energy dissipation - ductility classes Behaiour factor q of concrete buildings designed for energy dissipation Design strategy for energy dissipation Global and local ductility through capacity design and member detailing: oeriew Implementation of capacity design of concrete frames against plastic hinging in columns Detailing of plastic hinge regions for flexural ductility Capacity design of members against pre-emptie shear failure Detailing rules for the local ductility of concrete members Introduction Minimum longitudinal reinforcement in beams Maximum longitudinal reinforcement ratio in the critical regions of beams Maximum diameter of longitudinal beam bars crossing beam-column joints Verification of beam-column joints in shear Dimensioning of shear reinforcement in critical regions of beams and columns Confinement reinforcement in the critical regions of columns and ductile walls Boundary elements at section ends in the critical region of ductile walls Shear erification in the critical region of ductile walls Minimum clamping reinforcement across construction joints in walls of DCR Special rules for large walls in structural systems of large lightly reinforced walls Introduction Dimensioning for the ULS in bending with axial force Dimensioning for the ULS in shear Detailing of the reinforcement Special rules for concrete systems with masonry or concrete infills Design and detailing of foundation elements 138 CONTENTS

5 DESIGNERS' GUIDE TO EN AND EN Chapter 6 Design and detailing rules for steel buildings Scope Dissipatie ersus low-dissipatie structures Capacity design principle Design for local energy dissipation in the elements and their connections Faourable factors for local ductility Unfaourable factors for local ductility Design rules aiming at the realization of dissipatie zones Background of the deformation capacity required by Eurocode Design against localization of strains Design for global dissipatie behaiour of structures Structural types and behaiour factors Selection of the behaiour factor for design purposes Moment-resisting frames Design objectie Analysis issues in moment-resisting frames Design of beams and columns Design of dissipatie zones Limitation of oerstrength Frarnes with concentric bracings Analysis of frames with concentric bracings considering their eolutie behaiour Simplified design of frames with X bracings Simplified design of frames with decoupled diagonal bracings Simplified design of frames with V bracings Criterion for the formation of a global plastic mechanism Partial strength connections Prames with eccentric bracings General features of the design of frames with eccentric bracings Short links ersus long links Criteria to form a global plastic mechanism Selection of the typology of eccentric bracings Partial strength connections Moment-resisting frames with infills Control of design and construction 165 Chapter 7 Design and detailing of composite steel-concrete buildings Introductory remark Degree of composite character Materials Design for local energy dissipation in elements and their connections Faourable factors for local ductility due to the composite character of structures Unfaourable factors for local ductility due to the composite character of structures Design for the global dissipatie behaiour of structures Behaiour factors of structural types similar to steel Behaiour factors of composite structural systems 171

6 CONTENTS 7.6. Properties of composite sections for analysis of structures and for resistance checks Difficulties in selecting mechanical properties for design and analysis Stiffness of composite sections Effectie width of slabs Composite connections in dissipatie zones Rules for members Design of columns Design options Non-dissipatie composite columns Dissipatie composite columns Composite columns considered as steel columns in the model used for analysis Steel beams composite with a slab Ductility condition for steel beams with a slab under a sagging (positie) moment Ductility condition for steel beams with a slab under a hogging (negatie) moment Seismic reinforcement in the concrete slab in momentresisting frames Design and detailing rules for moment frames General Analysis and design rules for beams, columns and connections Disregarding the composite character of beams with a slab Limitation of oerstrength Composite concentrically braced frames Composite eccentrically braced frames Reinforced-concrete shear walls composite with structural steel elements General Analysis and design rules for beams and columns Composite or concrete shear walls coupled by steel or composite beams Composite steel plate shearwalls 184 Chapter 8 Design and detailing rules for timber buildings Scope General concepts in earthquake resistant timber buildings Materials and properties of dissipatie zones Ductility c1asses and behaiour factors Detailing Safety erifications 189 Chapter 9 Seismic design with base isolation Introduction Dynamics of seismic isolation Design criteria Seismic isolation systems and deices Isolators Supplementary deices 203

7 DESIGNERS' GUIDE TO EN AND EN Modelling and analysis procedures Safety criteria and erifications Design seismic action effects on fixed-base and isolated buildings 207 Chapter 10 Foundations, retaining structures and geotechnical aspects Introduction Scope ofthe Designers' Guide to EN Relationship between EN and EN (Eurocode 7: Geotechnical design. Part 1: General rules) Seismic action Topographie amplification factor 'Artificial' ersus recorded time-history representations Ground properties Strength parameters Partial factors for material properties Stiffness and damping parameters Requirements for siting and for foundation soils Siting 218 Example 10.1: calculation of seismically induced displacements in a reallandslide 221 Example 10.2: liquefaction hazard ealuation Ground inestigations and studies Ground type identification for the determination of the design seismic action 231 Example 10.3: ground-type identification at an actual construction ~~ n3 Example 10.4: a further case of ground-type identification at an actual site Foundation system General requirements - seismically induced ground deformation Rules for conceptual design Transfer ofaction effects to the ground ULS erifications for shallow or embedded foundations 238 Example 10.5: erification of the footing of a iaduct pier against bearing capacity failure 238 Example 10.6: non-linear dynamic analyses of a simple soil-footing model Piles and piers Soil-structure interaction Earth-retaining structures General design considerations Basic models Seismic action Design earth and water pressure 252 Example 10.7: simplified seismic analysis of a flexible earth-retaining structure with the pseudo-static approach 253 Example 10.8: non-linear dynamic analysis of the flexible retaining structure of Example 10.7 subjected to earthquake excitation 259 References Index