A method for predicting axial forces of columns (VBEs) in steel plate shear walls

Steel Plate Shear Walls (SPSW) are lateral load resisting systems composed of a thin web plate that is surrounded by boundary elements. For more than three decades, they have been used as the principal lateral load resisting system of various buildings in Japan, Canada and United States. However, the design methodology of the SPSW buildings from 70's has shifted. Much thicker web plates used to be preferred and stiffened to prevent buckling. Early research of 1980's by Kulak, Thorburn, Driver, Grondin and others has led the way to a new design methodology that took advantage of post buckling capacity of the web plates. Their work paved the way for numerous research programs that aided in better understanding of the system, especially its relation to earthquake-resistant design. In this new design methodology, boundary members are designed allowing not just tension field action to develop but also yielding of the tension diagonals. SPSW systems can dissipate significant energy through yielding tension diagonals. Their high initial stiffness and ductile response make them suitable in resisting seismic loads. Steel plate shear walls have less structural wall thickness, less contribution to building weight, faster erection and higher ductility compared to concrete shear walls. They can be used in new buildings as well as for retrofitting of existing buildings. Capacity design principles dictate that boundary elements of SPSW systems must be designed with the ability to resist demands from yielding tension diagonals. Internal forces of each member can be calculated using horizontal and vertical components of the tension strips. Vertical components of tension strips result in considerably high axial load demands in VBEs. Unnecessarily large steel sections for VBEs may be calculated with capacity design for SPSWs that are unlikely to yield over their entire height, typically multi-story tall SPSWs. A method is proposed in this thesis to avoid possible overdesign and to obtain realistic design forces for VBEs using square roots of the sum of the squares, SRSS method. For the study, SPSWs are designed for 3 case study buildings with the exact same floor plan but with different building heights; 6 story building, 10 story building and 14 story building. One bay with SPSW is designed for each building, using capacity design principles and proposed method. This method and preliminary design assumptions are then tested with actual earthquake events of the past, by non-linear time history analyses (NLTHA) of case study frames. Each frame is modeled, analyzed, forces and displacements for every member are recorded. Data obtained from NLTHA is compiled and compared with elastic design forces and applicability of the proposed method, SRSS Method, is verified.