Effects of adjacent brace interaction on the out-of-plane flexural behavior of CHS connections

Abstract

This paper studies the effect of adjacent braces interaction (ABI) on seismic and static performance of circular hollow section (CHS) unstiffened tubular connections under out-of-plane bending moment. A comprehensive comparison between CHS KK-connections (each chord side has two identical braces named adjacent braces) and the corresponding CHS X-connections (each chord side has one brace) is performed by experimental testing and finite element (FE) analysis, to evaluate the effect of ABI on the out-of-plane flexural behavior of CHS connections. The test results show that the load-carrying capacity of thin-walled CHS KK-connections (with ABI) is nearly 80% of that of the X-connections (without ABI). Moreover, experimental results indicate that CHS connections with ABI have better energy dissipation and ductility than CHS connections without ABI, which is further confirmed by the proposed load transferring mechanism model. FE parameter analysis results show that the effect of ABI on the moment-rotation curves and capacity is weak for CHS connections with chord radius-to-thickness ratio smaller than 9 and brace-to-chord angle smaller than 50°. But the influence of ABI is relatively larger for those CHS connections with the chord radius-to-thickness ratio larger than 10. Additionally, an equation for the capacity ratio of KK-connections to X-connections is proposed to consider the influence of ABI on the out-of-plane flexural capacity of CHS connections, and the equation has been verified by FE and testing results.