Behavior and design of intermediate HBE in steel plate shear walls

Steel Plate Shear Walls (SPSW) consist of unstiffened infill steel panels surrounded by columns, called Vertical Boundary Elements (VBE), on both sides, and beams, called Horizontal Boundary Elements (HBE), above and below. These infill steel panels are allowed to buckle in shear and subsequently form a diagonal tension field. SPSW are progressively being used as the primary lateral force resisting systems in buildings. Past monotonic, cyclic and shaking table tests on SPSW in the United States, Canada, Japan, Taiwan and other countries have shown that this type of structural system can exhibit high initial stiffness, behave in a ductile manner and dissipate significant amounts of hysteretic energy, which make it a suitable option for the design of new buildings as well as for the retrofit of existing constructions. Analytical research on SPSW has also validated useful models for design and analysis of this lateral load resisting system. Recent design procedures for SPSW are provided by the CSA Limit States Design of Steel Structures and the AISC Seismic Provision for Structural Steel Buildings. Innovative SPSW designs have also been proposed and experimentally validated to expand the range of applicability of SPSW. However, some impediments still exist that may limit the widespread acceptance of SPSW. For example, little experimental information exists on the behavior of intermediate HBE in SPSW as well as the performance of such HBE having reduced beam section (RBS) connections and composite behavior. Note that intermediate HBE are those to which are welded infill steel panels above and below, by opposition to anchor HBE that have steel panels only below or above. To further address the pressing concerns regarding behavior and design of intermediate HBE, a two-phase experimental program was developed to test a two-story SPSW specimen having an intermediate composite beam with RBS connections under the collaboration of the Multidisciplinary Center for Earthquake Engineering Research (MCEER) in the U.S. and the National Center for Research on Earthquake Engineering (NCREE) in Taipei, Taiwan. In this paper, following a brief review of the experimental observations from the MCEER/NCREE testing, the design recommendations will be presented, followed by examinations and explanations on the observed failure of the intermediate HBE.