When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.
Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.
Steel plate shear wall (SPSW) is an effective lateral load-resisting system rapidly gaining the attention of many researchers and structural engineers. The system is designed and constructed primarily in seismically active regions. Conventional SPSW uses thin unstiffened steel infill plates, which act as the main ductile fuse of the lateral load-resisting system. It is often required to have openings in the infill plate. One of the main reasons for having an opening in the infill plate is to provide a place for nonstructural elements such as windows or doors. However, when subjected to lateral loads, deformations around the openings are a concern that must be considered. The main objective of this study is to prevent the out-of-plane deformation of the openings and find a practical and efficient solution for this issue. A recognized method commonly used to prevent the buckling of thin steel plate shear walls is attaching stiffeners on the infill plate. Thus, using stiffeners around the opening is the main consideration as a solution for the addressed issue. Commonly used stiffened plates are extensively stiffened and have a relatively large number of stiffeners. This can make the stiffened SPSW system quite expensive and unpopular. This study aims to prevent the deformation of the openings by using as few stiffeners as possible.
In the first part of this research work, the behaviour of stiffened steel plate shear walls is studied analytically and numerically. The analytical study is done by the plate-frame interaction (PFI) model, and the numerical analysis is done using ABAQUS. The analytical study shows that stiffeners in the stiffened infill plate can increase elastic stiffness by 53% and the shear strength by about 15%. A series of SPSW models with horizontal and vertical stiffeners are analyzed, and their buckling behaviour is studied. A close agreement between the PFI method and the finite element analysis is observed. Based on the analysis, an improved stiffness criterion for designing stiffeners in stiffened SPSWs is proposed. FE analysis shows that the proposed stiffness criterion is effective in preventing the global buckling of the stiffened infill plates in SPSWs
In the second part, SPSWs with a rectangular opening are studied using finite element analysis. The results for unstiffened plates show very large deformations around the opening. Different stiffener layouts to prevent deformations are considered and analyzed. The results show that all considered layouts are effective in preventing the deformation around the opening. Based on the analysis, an effective stiffener layout is selected. FE analysis shows that the proposed stiffener layout can improve the behaviour of SPSWs with rectangular openings. FE models with different opening locations and sizes are also analyzed. Analysis shows that the shear strength of the stiffened infill plate depends only on the length of the rectangular opening. It is also observed that the location of the rectangular opening does not have any significant effect on the strength of the infill plate. Finally, a shear strength equation is proposed for the infill plate stiffened with the proposed stiffener layout around the rectangular opening.
In the last part, two one-third-scale single-storey SPSWs are tested. The specimens have a rectangular opening at the center of the plate, and the openings are reinforced using the proposed stiffener layout. The two specimens are identical in size, and the only difference between the specimens is the size of the opening. Cyclic quasi-static loading is applied at the top of the specimens. Various instruments are used to monitor the behaviour of the specimens during the experiment. Both tests show that deformations around the opening are successfully restrained. Test results also show stable hysteresis curves and good energy dissipation capacity for both specimens. In the end, a 4-storey finite element model with a large rectangular opening is selected, and seismic analysis is performed on the model with and without stiffeners. Eleven historical records are selected and scaled for the seismic analysis. Seismic analysis shows that the proposed stiffener layout around the opening can prevent out-of-plane deformation around the opening in the SPSW system.