Seismic performance of a steel frame assembled with a CFST-bordered composite wall structure

Abstract

This paper proposes a steel frame assembled with a concrete-filled steel tubular (CFST)-bordered composite wall structure. The composite wall was fabricated as an assembled seismic member to improve the seismic performance of the steel frame. Therefore, on the basis of a full-sized bare steel frame as a contrast specimen, four full-sized steel frames assembled with CFST-bordered composite wall specimens were designed. The differences among these four specimens include the use of inclined braces in the CFST-bordered composite walls and the different designs of the inclined braces, and these differences are to investigate the influence of the inclined braces on the proposed structures. Low cyclic loading was applied to the specimens, and the seismic behavior of each specimen was analyzed. The experimental results indicated that the seismic performance of the bare frame was greatly enhanced by the assembled CFST-bordered composite wall. The setting of the rebar braces or the CFST braces can significantly increase the yield load, peak load, and dissipation energy capacity, and the inverted V-shaped braces are efficient. The rebar braces can also delay concrete cracking and release strength degeneration. As the first line of defense, the damage of the CFST-bordered composite wall occurs earlier than that of the steel frame, and the damage of the steel frame is slight when the CFST-bordered composite wall is broken. The steel frame can still work as the second line of defense to prevent the collapse of the structure. Furthermore, calculation methods were proposed for determining the bearing capacities of the bare steel frame and the CFST-bordered composite wall based on the failure modes identified during testing and finite element analysis. The calculated results were in good agreement with the test results.