Seismic behavior of square concrete columns confined by FRP-steel composite tube

Steel tube confined concrete (STCC) structures have attracted academic and industrial attention in recent years because the additional confinement greatly improves structural performance, but their durability issues have gradually attracted attention. This paper studies the behavior of square fiber-reinforced polymer (FRP)-steel composite tube confined reinforced concrete (FRP-STCC) columns subjected to seismic loads, through a small-scaled quasi-static test and a finite element analysis. The test results show the FRP-STCC columns presented excellent seismic performance and deformation capacity. The lateral confinement of FRP-steel composite tube was verified and a simplified OpenSees-based finite element method model was developed to simulate the hysteresis behavior of the columns. Using the proposed models, a parametric analysis was conducted for investigating the effects of main factors on the seismic behavior of the FRP-STCC columns. Based on the test and numerical analyses, the study discussed the influence of key structural variables on the deformation capacity of the columns, especially ductility, structural characteristic factor, plastic hinge region height, and peak drift ratio of the columns. The results indicate that lateral confinement significantly improves the deformation capacities of the columns. Referring to the previous model, a simple peak drift ratio model was proposed, which can well evaluate the experimental results. •First discussed the structural characteristic coefficient of FRP-STCC composite columns under seismic loads.•Proposed a simple model to predict the peak drift ratio of the confined RC columns.•Proposed a simplified OpenSees-based finite element method (FEM) model for square FRP-STCC) columns.•Deeply discussed the deformation capacity of the columns, especially ductility, plastic hinge region height and peak drift ratio.