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 Therefore, the CTOD demand at the crack tip is low. The aforementioned effect is less marked in the overmatching weld condition ITS3-1. (L1) (L2) (a) (b) Figure 3.40. Equivalent plastic strain (PEEQ) distribution of TM-3 specimens at two levels of applied displacements: (a) overmatching weld (ITS3-1); (b) matching weld (ITS3-2) J (kJ/m 2 ) 700 600 500 400 300 200 100 0 0 2 4 6 8 10 DISPLACEMENT (mm) J 1 J 5 J 10 J 15 Figure 3.41. Values of J-integral for different contours as functions of the applied displacement 89
3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS Similar results are obtained for the TM-2 and JB1-3 specimens. In order to verify the quality of these analyses, the values of J-integral for different paths 1, 5, 10 and 15 are plotted in Figure 3.41 as a function of the applied displacement with reference to the specimens ITS2. More specifically, 1 represents the J-integral computation from the first ring of elements abutting the crack tip whilst 15 corresponds to the path surrounding all the elements of the “spider web” mesh illustrated in Figure 3.29b. The values of J1, J5, J10, and J15 agree with each other entailing path independence at the given applied displacement. It is worthwhile to recall that the estimate provided through the first ring of elements surrounding the crack tip does not provide high accurate results (Bursi et al, 2002). Residual stress effects Rapid uneven heat removal in welded connections entails large welding-induced residual stresses that can influence the joint behaviour in several ways. A detailed investigation of these effects for welded beam-to-column moment connections can be found in (Zhang et Dong, 2000). For the ITS connections of 12 mm thickness, an idealised residual stress pattern like the one highlighted in Figure 3.28 has been used, assuming a crack length equal to 1.30 mm and considering an overmatching weld. Relevant results are reported in Figure 3.42a and Figure 3.42b: results show clearly that the presence of residual stresses increases the toughness demand. REACTION FORCE (kN) 90 350 300 250 200 150 100 50 0 W/o residual stresses With residual stresses 0 1 2 3 4 5 DISPLACEMENT (mm) CTOD (mm) 1 0.8 0.6 0.4 0.2 0 CTOD c W/o residual stresses With residual stresses 0 1 2 3 4 5 DISPLACEMENT (mm) (a) (b) Figure 3.42. (a) Predicted force vs. displacement and (b) CTOD vs. displacement of TM-2 specimens with and without residual stresses The same idealised residual stress pattern has been used also for the ITS connections with 18 mm thickness with a crack length equal to 2.34 mm and for the
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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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