Design of RSFJ Self-centring Brace for Ultimate Limit State

Abstract

In previous studies, it was shown that the RSFJ brace assembly is prone to elastic buckling for which a new mechanism composed of two telescopic sections was introduced as a remedy to increase the elastic buckling load, and it was named as “Anti-buckling tubes” (ABT). However, designing the RSFJ brace for the elastic buckling may not be conservative, though strengthened with ABT, mainly because some part(s) of the brace may fail due to second-order actions (mainly moment) before hitting the elastic buckling. Therefore, in the present study, the inelastic buckling of the RSFJ brace assembly is going to be discussed, which is supposed to be the ultimate strength of the brace in compression. For this, a simplified closed-form formulation is developed which an engineer can simply employ to quantify and approximate that ultimate strength. The suggested framework is validated with a number of numerical examples using ABAQUS finite element software. Apart from those, some seismic design consideration will be discussed in order to guarantee that the brace will perform as it is expected at the time of the seismic event. Finally, and in the interest of further clarification, an example of a brace design procedure for a real case is provided.