Design of multiple cross-arm PCS-BRBs considering asymmetric imperfection and initial pre-tensioning force

Abstract

Multiple cross-arm Pre-tensioned Cable Stayed Buckling-Restrained Braces (MPCS-BRBs) can significantly enhance the elastic buckling performance and load resistance over common double-tube BRBs because of the additional cable stayed system. Previous studies conducted by the authors intended to investigate the lower limits of restraining ratios of MPCS-BRBs with pin-ended stays subjected to either monotonic or cyclic axial loads, where the initial geometric imperfection was taken to be consistent with the first order buckling mode. This study is a continuation of the previous paper, and it aims to explore interactive buckling of MPCS-BRBs with pin-ended stays in order to obtain a safe estimate of their load-carrying capacities through nonlinear Finite Element Analysis (FEA). In addition, interactive buckling of MPCS-BRBs is considered by introducing a series of asymmetric imperfections that are the mixtures of symmetric and antisymmetric imperfections during buckling analysis. The effects of different imperfections (symmetric, antisymmetric, and asymmetric) and initial pre-tensioning force of cables on the load-carrying capacities of the MPCS-BRBs with and without minor diagonal cables are explored and compared. Furthermore, a conservative design approach for those MPCS-BRBs can be established by fulfilling the corresponding lower limits of restraining ratios and optimal initial pre-tensioning force of cables based on the findings considering different types of initial geometric imperfections. Finally, such a conservative design approach is validated through nonlinear FEA for MPCS-BRBs subjected to either monotonic or cyclic axial loads. The findings in this study could provide guidance for a preliminary conservative design of the MPCS-BRBs in actual engineering applications.