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 On the other hand, the corresponding strain distributions highlighted in Figure 3.45 indicate that the end plate yield zone is smaller for the specimen labelled ITS2-90. Therefore, a balance between the two opposite requirements has to be found. (L1) (L2) Figure 3.45. Equivalent plastic strain (PEEQ) distributions of TM-2 specimens at two levels of applied displacements: (a) σy/σu=0.45 (ITS2-45); (b) σy/σu=0.90 (ITS2-90) As far as the ITS connections with 18 mm thickness is concerned, two strength ratios σy/σu for the end plate material equal to 0.60 and 0.90 have been considered and the corresponding specimens are called ITS3-60 and ITS3-90, respectively. Again, to take into account that the crack-initiation threshold increases with a strain-hardening reduction, two crack lengths equal to 2.34 mm and 4.95 mm have been chosen for the specimen ITS3-60 and ITS3-90, respectively. Similar results are obtained, as shown in Figure 3.46. So far we have estimated critical states both in 2D and 3D models through the use of a critical value of the CTOD, which amounts to 0.31 mm for the joints under examination. It is possible to define critical stress states through the use of response indices, which do not require a crack modelling. One of these indices is the Rupture Index related to the stress triaxiality ratio σm/σeff, where σm defines the hydrostatic stress and σeff is the von Mises stress. Several FE analyses were conducted to estimate this index at the weld toe. 2D simulations confirm that end plates with σy/σu = 0.6 exhibit a favourable value of the triaxiality ratio of about 0.49, implying a ductile behaviour. The corresponding 3D analyses yield a maximum triaxiality ratio sampled at the weld toe in the middle of the end plate of 93
3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS about 0.62; such value does not entail a limited ductility of the joints or a high potential for crack initiation. 94 CTOD (mm) 3.8 Conclusions 1 0.8 0.6 0.4 0.2 0 CTOD c L1 L2 ITS3-60 ITS3-90 0 1 2 3 4 DISPLACEMENT (mm) Figure 3.46. Predicted CTOD vs. displacement of TM-3 specimens at σy/σu=0.60 and σy/σu=0.90 A general test programme was presented, comprising partial strength bolted extended end plate joints with fillet welds and component parts, which represent an alternative to fully welded connections for use in seismic force resisting moment frames. The main results indicate that partial strength bolted extended end plate connections are suitable for use in seismic moment resisting frames. They represent an alternative to fully welded connections, as together with the column web panel yielding, they can exhibit favourable ductility and energy dissipation properties. As far as the understanding of the low-cycle fracture behaviour of ITS, CTS, and CJ connections is concerned, experiments and numerical analyses under monotonic and cyclic loading have provided insights in order to develop rules able to reduce fracture in the aforementioned connection components. The main conclusions of this study follow.
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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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3. SEISMIC BEHAVIOUR OF BOLTED END
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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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