DIRECT DISPLACEMENT-BASED BRACE PARAMETERS DESIGN AND ANALYSES OF STEEL FRAME WITH SELF-CENTERING BRACES

The equivalent damping ratio expression of steel frame with pre-pressed spring self-centering energy dissipation (PS-SCED) brace is proposed and validated in this paper. Then the direct displacement-based seismic design method is employed to determine the brace parameters of a 6-story PS-SCED braced frame. The results show that the designed brace stiffness is conservative and the brace bearing capacity demand is too large when the equivalent damping ratio is not considered. However, considering the equivalent damping ratio design makes the stiffness and bearing capacity demand of PS-SCED brace smaller and enables the braced frame to meet the specified performance level. Under the same performance level, the brace stiffness ratio has little effect on the structural displacement responses. Therefore, the designed brace parameters according to the proposed stiffness ratio interval are capable of making the PS-SCED braced frame meet the requirement of deformation limit.