Parametric study and design approach of off-center bracing systems

摘要

This paper presents an effective approach for the seismic design of off-center bracing systems (OBSs). The nonlinear behavior of an OBS can be specified by evaluation of two yielding stages representing tensile yielding of different bracings. This can be achieved when stiffness of the corner brace member is deliberately considered less enough to act as a fuse-like component. An accurate two-dimensional finite element modeling for the geometric and material nonlinearity of such systems considering buckling behavior of the brace members is developed. Through an extensive parametric study, the optimal ratios of the influential parameters of OBS are obtained, and their effects on the nonlinear performance of OBS are evaluated. Next, a number of design graphs for determining the trilinear behavior model of different types of the OBS are presented. The aforementioned diagrams are included of non-dimensional force and stiffness parameters that can be used for other frames with the same properties. Then, by extracting an equivalent bilinear model from the trilinear approximated behavior, an effective design algorithm based on the calculation of system's ductility under desired earthquake is presented, and finally, applicability of the proposed design approach is well demonstrated through an example problem.