Cyclic performance of precast steel beam-to-CECFST column exterior sub-assemblages with dry connections: experimental studies and mechanism analyses

Abstract

Combining advantages of both reinforced concrete (RC) and concrete-filled steel tube (CFST), concrete-encased concrete-filled steel tube (CECFST) members demonstrate superior structural performance over pure RC or CFST counterparts. Nevertheless, current research in this domain has primarily focused on member and connection behaviour of CECFST columns, with no attention given to frame-level performance. This significantly impedes applications of this form of high-performance composite members into actual engineering practice. To bridge this research gap, a novel precast steel beam-to-CECFST column composite system is proposed in this study. This is followed by a comprehensive experimental programme, where seven precast steel beam-to-CECFST column exterior sub-assemblages were tested under cyclic loads. In the test specimens, three types of connections, including beam-to-beam (B-B), column-to-column (C-C) and beam-to-column (B-C), were incorporated to establish a precast steel beam-to-CECFST column sub-assemblage. Horizontal displacement versus shear force relationship and failure mode of the test specimens are reported, followed by a detailed analysis of test results and findings. Furthermore, a comprehensive mechanism analysis is presented, with emphasis on energy dissipation behaviour and deformation mechanism of the proposed precast composite system. The test results show that the proposed precast composite system has comparable load-carrying capacity and energy dissipation capacity in comparison with conventional cast-in-place counterparts. This indicates that despite using precast beam-to-beam and column-to-column connections, structural performance of the composite frame system would not be significantly affected, showing that this form of precast steel beam-to-CECFST column composite system has considerable potential to be adopted in actual engineering practice.