This paper presents insights on the combined contribution of posttensioning and beam-to-column joint rocking connection in selfcentering steel plate shear walls (SC-SPSWs). Moment, shear, and axial force diagrams along the boundary beam are developed based on capacity design principles and are compared with nonlinear cyclic pushover analysis results. These closed-form solutions are integrated into a design procedure to select cross-sectional areas of the posttension reinforcement and beam sizes: (1) to prevent in-span plastic hinges; (2) to ensure that posttension reinforcement remains elastic to maintain self-centering capability of the system; (3) to impose sufficient initial posttensioning to overcome wind and gravity loads; (4) to provide adequate beam plastic strength considering reduced moment capacity due to the presence of axial and shear forces; and (5) to consider posttension losses due to axial beam shortening. Using this fundamental behavior knowledge, and adding response-based performance objectives to the design procedure, a companion paper investigates the seismic response of SC-SPSW using time-history nonlinear analyses.
This paper presents results from an investigation of the behavior of unstiffened thin steel plate shear wall ͑SPSW͒ having a regular pattern of openings ͑a.k.a. perforated SPSW͒. Finite element monotonic pushover analyses were conducted, first on a series of individual perforated strips with variation in perforation diameter, to develop a fundamental understanding of the behavior of complete perforated SPSW, then on a corresponding series of complete perforated SPSW having various perforation diameters. Three different sets of wall boundary conditions are considered, namely: flexible beam laterally braced, rigid floor, and rigid beam. Though some differences between the SPSW panel strips and the individual strip results are observed at large monitored strain, at lower monitored strain however the two models are in a good agreement. Based on the analytical results design recommendations of these perforated SPSWs are presented. The shear strength of a SPSW infill plate having a pattern of multiple regularly spaced circular perforations can be calculated as a function of the shear strength of a solid panel, perforation diameter, and distance between perforations.
Assessment of collapse potential and seismic performance was conducted for steel plate shear walls (SPSWs) having infill plates designed per two different philosophies. This assessment was first conducted on SPSWs that were designed neglecting the contribution of their boundary moment resisting frames to resist story shear forces. This assessment of collapse potential was repeated for SPSWs that were designed considering the sharing of story shear forces between the boundary frames and infill plates. Based on these assessments, seismic performance factors [i.e., response modification coefficient (R-factor), system overstrength Ω 0 factor, and deflection amplification C d factor] for both types of SPSWs were identified and compared. Adjustments to improve collapse performance and factors that affect collapse potential were presented. Collapse fragility curves for archetypes with various structural configurations (i.e., panel aspect ratio, intensity level of seismic weight, and number of stories) were investigated. Findings from these analyses demonstrate that the infill plates of SPSWs should be designed to resist the total specified story shears, and that SPSWs designed by sharing these story shears between the boundary frame and infill plates will undergo significantly larger and possibly unacceptable drifts.
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