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TABLE OF CONTENTS
ABSTRACT………iii RINGRAZIAMENTI……..………..v ACKNOWLEDGEMENTS……….vi TABLE OF CONTENTS………...vii LIST OF ABBREVIATIONS………..x CHAPTERS 1. INTRODUCTION………11.1 THE RAINFLOW ANALOGY FOR THE DISSIPATIVE STRUCTURES UNDER SEISMIC ACTION……….………...2
1.2 STEEL HYSTERETIC DAMPERS………..6
1.2.1 History of steel hysteretic dampers………....7
1.2.2 Features of steel hysteretic dampers………..8
1.2.3 Types of steel hysteretic dampers……….….8
1.3 VISCOUS FLUID DAMPERS………13
1.4 OBJECTIVE AND METHODOLOGY………..……….15
1.5 DISSERTATION OUTLINE………...16
2. THE MAURER COMPACT STEEL DAMPER (MCSD): CONCEPT DEVELOPMENT.18 2.1 THE PATENT………..………18
2.2 THE CONFIGURATIONS………..19
2.3 DESCRIPTION OF PREFERRED CONFIGURATIONS………..22
3. ANALYTICAL MODELS………..………..29
3.1 DEFORMATION THEORY OF PLASTICITY………...…..29
3.1.1 The concept of effective stress and strain………....30
3.1.2 Stress-strain relationship for plane stress state………31
3.1.3 Simple elastoplastic constitutive models………..…………...31
3.1.4 Yield conditions for isotropic materials………..…32
3.1.5 Flow theory of plasticity………..33
3.1.6 Fundamental equations………..…..35
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3.2 A UNIFORM TUBE UNDER PURE AXIAL LOAD……….…...……….38
3.2.1 Bilinear material model………..…………..………39
3.2.2 Results comparing between pipe with gap and no-gap………....……….41
3.3 THE STUDY OF THE STRAIN BEHAVIOUR…..……….…..43
3.3.1 Classification of shell as surface of revolution………...…..…44
3.3.2 Analytical calculation of radii surface displacement………45
3.3.2.1 Complete tube radii surface displacement………..……46
3.3.2.2 Tube with longitudinal gaps radii surface displacement……….…49
3.4 BUCKLING ANALYSIS………..…..……….……52
3.4.1 Critical load of cylindrical shell without slot………52
3.4.2 Critical load of cylindrical shell with symmetric longitudinal slot………..……55
3.5 EVALUATION OF THE SISTEM STIFFNESS…..……….………..56
3.5.1 The single pipe stiffness………..……….…59
3.5.2 The device stiffness……….…….60
3.5.3 The increasing of stiffness due by contact between surfaces………..….63
3.6 DIMENSIONING OF THE PROTOTYPE…..………....66
3.7 DESIGN OF THE PROTOTYPE………..……...69
3.7.1 The tensile test……….…….70
3.7.2 The prototype………76
3.8 LOAD-DISPLACEMENT RESPONSE CURVE UNDER MONOTONIC LOAD…...79
3.8.1 The response curves under monotonic load of single pipes……….79
3.8.2 The response curves under monotonic load of the prototype……….…..80
3.9 LOAD-DISPLACEMENT RESPONSE CURVE UNDER CYCLIC LOAD………….82
3.9.1 Linear kinematic Hardening……….…82
3.9.2 The response curves under cyclic load of single pipes……….……85
3.9.3 The response curves under cyclic load of the prototype……….…..87
4. NUMERICAL MODELS……….………..………...…….89
4.1 NUMERICAL METHODS IN PLASTICITY……….89
4.1.1 Finite Element Method………...……..89
4.1.2 Nonlinear material models………90
4.1.3 Solution strategies in nonlinear analysis……….…..…....91
4.1.3.1 Newton-Raphson iteration under load control……….…..….91
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4.2 THE INTERFACE OF THE PROGRAM..………...……...…95
4.2.1 The engineering data………...…..…96
4.2.2 The geometry………97
4.2.3 Meshing………..………..98
4.2.4 The contact tips………..…….100
4.2.5 Boundary condition and load application………..……….102
4.3 THE STRAIN BEHAVIOUR RESULTS………..……103
4.4 NUMERICAL BUCKLING ANALYSIS………..…106
4.5 THE EFFECTS OF THE CONCTACT BETWEEN SURFACES………109
4.6 LOAD-DISPLACEMENT RESPONSE CURVE UNDER MONOTONIC LOAD AND RESULTS COMPARING………...…...114
4.6.1 The response curves under monotonic load of single pipes………...…114
4.6.2 The response curves under monotonic load of the prototype……….……118
4.7 LOAD-DISPLACEMENT RESPONSE CURVE UNDER CYCLIC LOAD AND COMPARING………..………..…123
4.7.1 The response curves under cyclic load of single pipes………...123
4.7.2 The response curves under cyclic load of the prototype……….……126
5. THE EXPERIMENTAL PHASE………..………...…129
5.1 THE EXPERIMENTS OF PROTOTYPE SINGLE PIPES ………..…129
5.1.1 Testing and assessment criteria………..……….130
5.1.2 EN 15129 criteria………...……….…130
5.2 THE SPECIMENS……….…131
5.3 TESTS SETUP………...135
5.4 TESTING PROCEDURE………..….138
5.5 CYCLIC RESPONSE OF SINGLE PIPES………...……….139
6. ASSESMENTS OF THE RESULTS….………..………144
7. CONCLUSIONS………..………150
REFERENCES……….……153
APPENDIX A………..…………156
