Seismic performance and damage analysis of steel-PVA hybrid fiber cementitious composites encased CFST columns

Using axial compression ratio, core concrete strength, steel tube thickness, and SPC strength as research variables, cyclic loading tests were conducted on 12 steel-polyvinyl alcohol (PVA) hybrid fiber cementitious composites(SPC) encased concrete-filled steel tube（CFST）columns to study the seismic performance of specimens under earthquake action, including failure mode, strength, stiffness, ductility, energy dissipation, and second-order effects. According to the study's findings, fiber bridging enabled SPC-encased CFST columns to effectively prevent cracks and maintain high integrity even after failing. The axial compression ratio, core concrete strength, and lateral bearing capacity were positively correlated, with a maximum bearing capacity increase of 46.9%, but their deformation capacity had decreased to varying degrees. The thickness and SPC strength of the steel tube exhibited excellent performance in terms of deformation capacity and energy consumption, with a maximum ductility coefficient of 6.21. In the overall statistical analysis of research variables, it was found that composite columns with core concrete strength grades higher than outer SPC strength had better seismic performance compared to other specimens. This article proposed an improved Park-Ang damage model that effectively evaluates the damage status of SPC-encased CFST columns. The model complies with the boundary conditions of the composite column, and the damage development trend reflected is consistent with experimental phenomena.