Seismic Performance of Self-Centering Square Concrete-Filled Steel Tubular Column-to-Steel Beam Connection under Variable Axial Force

Abstract

A self-centering square concrete-filled steel tubular column-to-steel beam connection with bolted angles was designed and its behavior analyzed theoretically. Three ½-scale specimens differing only in the loading procedure of the vertical force were tested under cyclic loading conditions. A finite element (FE) model of the self-centering connection was established in the ABAQUS software and its validity verified against experimental results. Compared with experiments, an extended parameter analysis of the variable axial force with a wider variation range of axial force and variable axial force in imitation ground motion was conducted using the proposed FE model. The experimental results showed that specimens with larger axial forces and variable axial forces consumed more energy and had clearer residual drifts compared with those of specimens with smaller axial forces and constant axial forces, respectively. The simulation results showed that a larger axial force considerably decreased the resistance capacity of the lateral load, resulting in a descending skeleton curve. A clear residual drift and asymmetry in the maximum relative rotation were observed under positive and negative displacement upon increasing the axial forces. In addition, a larger range of change in the axial force resulted in a more prominent residual drift compared with a smaller range of change in the axial force under a relatively small lateral displacement, decreasing the reliability of the self-centering capacity of the connection during an earthquake.