Numerical study of circular steel tube confined concrete (STCC) stub columns

In this paper, a new finite element (FE) model using ATENA-3D software was developed to investigate the compressive behavior of circular steel tube confined concrete (STCC) stub columns with taking into account various concrete strengths. The “CC3DNonLinCementitious2User” material type for concrete in ATENA-3D with some modifications of material laws was adopted to simulate the behavior of concrete core with consideration of the confinement effect induced by steel tube. Both ultimate load and axial load versus strain obtained from FE model were compared with those from previous test results. This comparison indicates that the new FE model in ATENA-3D is capable of predicting the compressive behavior of circular STCC stub columns. An extensive parametric analysis using this established FE model was then conducted to examine the influence of concrete compressive strength, steel yield strength and steel tube thickness on the strength and the ductility of circular STCC stub columns. Furthermore, based on previous test database, some analytical model for concrete confined by steel tube was evaluated and a simplified formula for predicting the ultimate load of circular STCC stub columns was also proposed. There was a good agreement between the predictions of the ultimate load using this proposed formula and FE model.