Seismic performance improvement of tension-only-braced frames with Energy-Dissipative Rocking Columns

Abstract

Steel braced frames consisting of strong beams, weak columns, and tension-only braces (BTFs) have been extensively used in low-rise steel buildings, since it is prefabricated rapidly and is cost-efficient. However, BTFs are vulnerable to soft story failure due to the negligible post-yielding stiffness of tension-only braces. A novel device of Energy-Dissipative Rocking Column (EDRC) is proposed to improve the seismic performance of BTFs. An EDRC consists of dual hinge supported steel column branches and replaceable steel strip dampers between them. Firstly, the effectiveness of EDRCs were verified through nonlinear time history analyses on benchmark multi-story BTFs using a suite of far-field ground motion records. Secondly, systematic parametric studies are conducted to quantify the effect of key influencing factors such as stiffness ratio of EDRC to BTF and bending stiffness of column branches on the seismic performance improvement of BTF-EDRC systems. The results show that the maximum inter-story drift and inter-story drift concentration under earthquakes as well as the residual drift after earthquakes can be significantly mitigated by coupling with EDRC. It is found that the maximum inter-story drift ratio can be reduced by 50% when the stiffness ratio of EDRC to BTF reached 1.0. The most effective stiffness ratio of EDRC to BTF for mitigating the inter-story drift concentration and residual drift ratio falls in a range of no more than 0.2 and 0.4, respectively.