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

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4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS compared with the analytical prediction obtained from the model are shown. It is evident that the theoretical and the experimental results do not agree closely. It is interesting to underline that with a modified model in which the contribution of the composite section is not taken into account, the analytical prediction agrees quite well with the experimental results. This means that after the crushing of the concrete the benefit composite action of the beam is lost and the joint behaves simply as steel joint. Similar results are obtained for the exterior joint, as depicted in Figure 4.36; however, different considerations have to be made. COMPLETE JOINT MOMENT (kNm) 360 300 240 180 120 60 0 -60 -120 -180 -240 -300 Experimental Analitical Model -75 -60 -45 -30 -15 0 15 30 45 60 75 ROTATION φ (mrad) Figure 4.36. Comparison between experimental and numerical joint response of the CJ-EXT specimen Under sagging bending moment, the analytical model is capable to predict correctly the maximum strength of the connections, as shown in Figure 4.37, but it is not able to predict the loss of strength due to the crushing of the concrete. Under hogging bending moment the analytical model captures very well the behaviour of the connection, in term both of stiffness and strength. The combination of the response under sagging and of the response under hogging bending moment of the specimen produces a different redistribution of force between connection and web panel in shear, which the model is not able to reproduce. This fact can explicate the differences in the global behaviour between experimental and analytical results. 141
4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS 142 CONNECTION MOMENT (kNm) 360 300 240 180 120 60 0 -60 -120 -180 -240 Experimental Model with concrete -300 -60 -45 -30 -15 0 15 30 45 ROTATION θ (mrad) Figure 4.37. Comparison between experimental and numerical connection response of the CJ-EXT specimen 4.8.4 3D finite element (FE) model To better understand the stress state in the web panel zone and in the concrete slab and therefore the activation of the transfer mechanisms idealized in Section 4.5.1, 3D finite element (FE) models of the composite joints have been developed, such as the one depicted in Figure 4.38. On the basis of the experimental results and the data collection, inelastic FE analyses carried out by means of the ABAQUS code (2001) on the exterior tested complete joints (CJ-EXT) have been calibrated and the stress and strain state of the aforementioned connection was simulated in the monotonic displacement regime. The model includes details such as all re-bars in the concrete slab, boltholes and bolts; surface-to-surface contact elements are used to model the surface interaction. 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. These displacements are held constant throughout the loading. The end of the beam and the bottom of the column in the model have roller and pin boundary conditions, respectively. The material models exploited for 3D elements are those available in the ABAQUS code (2001). Elasto-plastic simulations of composite substructures are performed
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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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5. SEISMIC BEHAVIOUR OF RC COLUMNS
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6. SUMMARY, CONCLUSIONS AND FUTURE
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