Experimental Investigation of Boundary Constraints on the Multistory Composite Frame under an Internal-Column Removal Scenario

Abstract

To investigate the anticollapse performance of a multistory composite frame (MSCF) under internal column-removal conditions, a static experiment using a one-third scale, three-story composite frame was conducted. This experiment utilized horizontal loading and specialized boundary-restraint systems. This paper undertook a comprehensive discussion that examined the MSCF’s load-resisting capacity, failure patterns, deformation behaviors, axial force generation, and load-transfer mechanisms. To better understand how different load-bearing mechanisms contribute to structural total resistance, the resistance contribution coefficients for the flexural and catenary mechanisms in double-span beams (DSBs) at various stories were introduced. The results showed that the boundary-restraint systems effectively simulated horizontal constraints on the extended beams across all stories. The axial forces in the beams of each story were unevenly distributed, a phenomenon attributed to the Vierendeel action (VA). The resistance contribution coefficients also varied by story, with values of 43%, 37%, and 20% from the bottom to the top stories. VA played a crucial role in the development of catenary action within each story beam, and its impact on the flexural mechanism was minimal. Finally, the experimental results in this paper were compared with those of prior experimental tests, including a single-story beam-column assembly and two multistory subframes. This comparison further validated the efficacy of experimental loading scheme for MSCFs, providing valuable insights for future collapse-resistance tests.