Seismic performance of steel frame with a self-centering beam

Abstract

Self-centering moment-resisting frames are capable of returning to their original plumb position after a severe earthquake, having sustained no or only slight structural damage. In this paper, a steel frame composed of a self-centering I-beam is proposed, with its capacities for self-centering and inelastic deformation provided by post-tensioned (PT) strands and energy dissipating (ED) elements, respectively. Based on an analysis of its mechanical properties, an experiment involving this self-centering frame under cyclic loading was conducted to investigate its load transfer mechanism, bearing capacity, hysteretic behaviour, ductility, energy dissipating capacity and self-centering capacity. The results agree well with the theoretical analysis, and it can be concluded that its force-displacement hysteretic curve has a typical flag shape. The plastic deformation of the specimen is concentrated on the ED elements, which can be replaced easily after an earthquake. As the gap-opening of the anchorage plate occurs, the PT strands and ED elements provide the bending stiffness for the structure. When the story drift is loaded to 4%, the skeleton curve does not have a descending section, which means that the structure still has sufficient bearing and deformation capacities. The analysis of the residual story drift and the equivalent viscous damping coefficient shows that the frame has good energy dissipating and self-centering capabilities. A finite element model is established with OpenSees to simulate the seismic behaviour of the self-centering frame. Using the model, the seismic performance of the frame is analysed in terms of its structural parameters, including the section area of the PT strands, initial stress on the PT strands and section area of the ED elements.