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

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6. SUMMARY, CONCLUSIONS AND FUTURE PERSPECTIVES performance of partial strength bolted extended end plate joints with fillet welds, which represent an alternative to fully welded connections for use in seismic force resisting moment frames; (ii) to verify in a low-cycle fatigue regime, the feasibility of the mechanical approach adopted for joints undergoing monotonic loading, whereby the properties of a complete joint are understood and obtained by assembling the properties of its component parts. 2. Seismic response of partial-strength composite joints: in order to evaluate the feasibility and effectiveness of the composite constructions with partial- strength beam-to-column joints and partially encased columns in earthquake- prone regions, the study aimed at calibrating design rules affecting the aforementioned components and the participation of the concrete slab in the relevant transfer mechanisms. The results of this project led to improved design procedures for composite constructions (Section 7, Part 1 of EC8, 2002). 3. Seismic behaviour of RC columns embedding steel profiles: this last research activity was part of another European Project titled Two Innovations For Earthquake Resistant Design - INERD Project, that deals with the improvement of the resistance and ductility of reinforced concrete (RC) structures using the performance of structural steel profiles. The general objective was to establish a new standard constructional rule able to improve the seismic safety of reinforced concrete structure, without great changes of traditional constructional practice. This rule consists in promoting one specific construction measure for lower storeys of reinforced concrete structures, by which steel profiles would be encased in RC columns in order to provide them with a basic reliable shear and compression resistance. 6.2 Conclusions and future perspectives 6.2.1 Seismic behaviour of bolted end plate beam-to-column steel joints 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 245
6. SUMMARY, CONCLUSIONS AND FUTURE PERSPECTIVES 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. 246 vi. When proper consideration is given to material selection and detailing, extended end plates show a cyclic performance adequate for seismic design. The considered joints exhibit a plastic rotation greater than 35 mrad; therefore, they can be classified as ductile in accordance to Eurocode 8 (2002). In detail, test results on isolated bolted Tee stubs as well complete extended end plate bolted joints have shown that the overall behaviour of the specimens under investigation is governed by the material endowed with the lowest strength, viz. the base metal, in which yielding occurs, effectively. In fact, the weld metal persists in the elastic regime while the contiguous zones are weakened owing to the sharp thermal treatments and to structural as well as shape discontinuities. vii. Component cyclic tests enable identification of the failure mode. Moreover, they allow the Code requirements on the rotational capacity of the joint to be checked. Moreover, the mechanical models provided by the Eurocodes to determine the stiffness and strength characteristics of the individual components showed little agreement with the experimental data. viii. A component model, which approximates the cyclic response of the joints on the basis of the responses of the elemental components, does not seem to possess sufficient accuracy. Conversely, the use of macro- components, incorporating some of the interaction effects among elemental components, appears to be more adequate. ix. The simulations relevant to isolated Tee stub and Complete Joint connections indicate that the numerical model with isotropic hardening rule is able to capture both the monotonic and the cyclic responses but is not able to reproduce properly stiffness and strength degradation. x. A number of parametric analyses have been performed by considering fractures initiating from weld-root defects by means of the onset cracking method. Conclusions drawn from the models indicate that: a. fracture driving force demands are reduced by using fillet welds matching the end plate material; b. welding-induced residual stresses increase the fracture demand;
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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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Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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