Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS 3.7.2 FE Models of the CJ specimens Non-linear FE analyses of the tested Complete Joints were carried out both by 2D and 3D models in a monotonic loading regime. As a matter of fact, 3D finite element analyses of bolted connections are very demanding from a computational standpoint. Hence, 2D models endowed with eight-node CPS8 plane stress elements were adopted to reduce the computational expense. For completeness some analyses have been repeated with 3D FE models, as 2D models tend to average stresses along the joint width. In a way similar to the models used for the Isolated Tee Stubs, 2D models of the CJ specimens exploited FE layers to reproduce the end plate and additional FE layers to simulate the bolt shank. Both the specimens endowed an end plate with flange thickness of 12 mm and 18 mm are modelled. The models include details such as boltholes and bolts; surface-to-surface contact elements are used to model the surface interaction, neglecting friction, which has a negligible effect on the joint response (Bursi and Jaspart, 1998). Moreover, constraint equations are introduced to make the bolt heads continuous with the end plate. Bolt pre-tensioning is applied by prescribed displacements at the end of the bolt shank, in order to entail a final average shank stretch equal to 0.065 mm, similar to that detected during testing. These displacements are held constant throughout the loading. Welding-induced residual stresses develop unavoidably in the welds and in the base metal owing to thermo elasto-plastic deformation. Therefore, an idealised stress distribution as the one highlighted in Figure 3.28 has been introduced. One more time, at the weld toe where stress concentrations are expected, a refined FE mesh is adopted. A crack endowed with a length of 0.26 mm (small-to-moderate root defect) was modelled at the weld toe in order to investigate the behaviour of cracked connections. More specifically, cracking is studied through contour integral evaluation in order to infer J values. The model is shown in Figure 3.33 and represents the JA1-2 CJ specimen, endowed with a 12 mm end plate thickness coupled with the column of HEA180 profile. Keeping the above-mentioned characteristics of the 2D model, a very complex 3D model of the specimen was performed in order to investigate the real stress and strain distribution along the width of the joint. With a view to confirming the hypotheses of 2D analyses, one of the main objectives that it was be obtained with the 3D model was increased accuracy in the computed local stress-strain state of the beam flange region due to weld residual stress and high gradients of stresses, where the connection has the highest fracture potential. The realised model is reported in Figure 3.34 and it represents the JB1-3 CJ specimen, endowed with an 18 mm end plate thickness coupled with the column of HEB180 profile. It is 81
3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS characterized by reduced integration twenty-node solid elements (C3D20R in the ABAQUS library). 82 Figure 3.33. 2D FE model of a complete joint JA1-2 Figure 3.34. 3D FE model of a complete joint JB1-3
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Dipartimento di Ingegneria Meccanic
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UNIVERSITÀ DEGLI STUDI DI TRENTO D
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Ai miei genitori
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INDEX 1 INTRODUCTION...............
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INDEX iii 4.10.3 Results of the PsD
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1.1 Introduction 1 1 INTRODUCTION I
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1. INTRODUCTION imposes precise con
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1. INTRODUCTION joints whilst 2D mo
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7 2 DUCTILITY AND SEISMIC RESPONSE
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2. DUCTILITY AND SEISMIC RESPONSE O
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4. SEISMIC RESPONSE OF PARTIAL-STRE
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5. SEISMIC BEHAVIOUR OF RC COLUMNS
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6. SUMMARY, CONCLUSIONS AND FUTURE
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Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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