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 CJ connection with 18 mm thickness with the same crack length. The results are then compared. The maximum CTOD required along the end plate width close to the weld toe predicted both by 2D and 3D analyses is depicted in Figure 3.43. The 3D analysis reveals a significant gradient across the width of the flange with a peak value in correspondence with the web. The CTOD ratio between 3D and 2D FE models is around 16 per cent. CTOD (mm) 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 2D Simulation 3D Simulation 0 20 40 60 80 100 120 140 160 180 FLANGE WIDTH (mm) Figure 3.43. 2D versus 3D CTOD distribution at the weld toe for a crack depth of 2.34 mm Yield-to-ultimate stress ratio effects The plastic hinge region in a steel structure decreases as the yield-to-ultimate strength ratio σy/σu increases. In fact, a smaller yielded region imposes greater inelastic strain demands to achieve a specified plastic deformation. Since the production of American structural steel has resulted in steel with much higher ratios (Frank, 1997), recently published specifications from AISC (1997) recognized this effect and limited the yield-to-ultimate strength ratio to 0.85. A similar limitation is required by Eurocode 3 (2001), when plastic analysis has to be performed. In order to study the yield-to-ultimate strength ratio effect on the joint configuration with 12 mm and 18 mm thickness, two strength ratios for the end plate material have been considered. More specifically, for the TM-2 specimen, σy/σu has been chosen to be 0.45 and 0.90 whilst the corresponding specimens are designated ITS2-45 and ITS2-90, respectively. However, two crack lengths equal to 1.30 mm and 2.86 mm have been considered for the specimen ITS2-45 and ITS2-90, respectively, to take account of the increase of crack-initiation threshold with the reduction of a strain hardening amount (Barsom and Rolfe, 1987). The reaction force vs. the controlled displacement of the TM-2 model is shown in Figure 3.44a, 91
3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS whilst the corresponding CTOD demand is illustrated in Figure 3.44b. From the above-mentioned plots, one may observe that at large displacements, the condition in which σy/σu tends to 0.90, viz. ITS2-90, is the most favourable from a fracture mechanics standpoint. 92 REACTION FORCE (kN) CTOD (mm) 300 250 200 150 100 50 1 0.8 0.6 0.4 0.2 0 0 L1 L2 (a) ITS2-45 ITS2-90 0 1 2 3 4 DISPLACEMENT (mm) CTOD c L1 (b) L2 ITS2-45 ITS2-90 0 1 2 3 4 DISPLACEMENT (mm) Figure 3.44. Predicted force and CTOD vs. displacement of TM-2 specimens at σy/σu=0.45 and σy/σu=0.90
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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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