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Seismic behaviour of steel plate shear walls by shake table testing Rezai, Mahmoud

Abstract

This dissertation describes an experimental and analytical study on the behaviour of steel plate shear walls with thin unstiffened webs when used as primary lateral load resisting system in medium- and high-rise buildings. The steel plate shear wall system resembles a vertical plate girder where the theoretical buckling strength of the plate panels is negligible and lateral loads are carried through post-buckling strength of the plate panels in combination with the frame action of the surrounding beams and columns. The theory that governs the design of steel plate shear wall structures is essentially the same as that of plate girders developed by Basler in 1961, although the relatively high bending strength and stiffness of the beams and columns have a significant effect on the overall behaviour, especially when high axial forces and overturning effects dominate the behaviour of the system. To verify the guidelines and design principles provided in the latest version of Canada's National Standard on Limit States Design of Steel Structures, CAN/CSA-S16.1-94 (1994), and to broaden the scope of the code, an experimental testing program accompanied by numerical investigation was conducted at the University of British Columbia. This effort was in collaboration with researchers at the University of Alberta and a team of consulting engineers. During the first phase of the experimental program two single storey single bay specimens were tested cyclically to gain information on the general behaviour of the system and verify the adequacy of fabrication procedures. In the second phase, a single bay four-storey 25% scale specimen was tested under a quasi-static cyclic testing protocol. As the third phase of testing, a similar four-storey specimen was tested on the shake table under low, medium and intense dynamic horizontal base motions. The two single storey and one four-storey test specimens were loaded to maximum displacement ductilities of 7 x δƴ, 6 x δƴ and 1.6 x δƴ, during the first and second phases of testing, respectively. The single storey specimens proved to be very stiff, compared to the bare frame, showed good ductility and energy dissipation characteristics, and exhibited stable behaviour at very large deformations following many cycles of loading. Sufficient data was gathered to establish the overall performance of these structural systems under lateral loading. For the third phase of testing the dynamically tested four-storey specimen was subjected to a number of site-recorded and synthetically generated ground motions with varying intensities. Even though each test gave important information about the dynamic behaviour of the scaled steel plate shear wall specimen, the limited capacity of the shake table prevented the attainment of significant inelastic response in the specimen. Results from the scaled steel plate shear wall tests were used to verify numerical models and to gain an understanding of how the various methods of modelling the shear resistance of thin infill plates would affect the predicted results. In general, the code prescribed strip models overpredicted the elastic stiffness of the test specimens, while the yield and ultimate strength were reasonably well predicted. The load-deformation behaviour of the specimens was considerably affected by small variations of the angle of inclination of the tension struts representing tension field development. The discrepancies between the analytical and experimental results was more dramatic for the four-storey specimen than the single storey specimens. This was deemed to be a function of the overall aspect ratio (total height over panel width) of the specimen. For the four-storey specimens the higher moment to base shear ratio emphasized flexural deformations compared to storey shear behaviour. An improved numerical model was proposed that utilizes discrete strips placed at different angles. A semi-empirical equation was proposed to determine the effective width of the steel panels in resisting storey shears. The proposed model predictions were in good agreement with the envelope of cyclic and dynamic time-history test results obtained from experimental studies at the University of British Columbia and University of Alberta. [Scientific formulae used in this abstract could not be reproduced.]

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