Local buckling and hysteretic behavior of Q690 high-strength steel box-section beam–columns

Abstract

High-strength steel structures have favorable mechanical properties and perform economically, but their application in seismic design is limited owing to their poor deformation capacity. In order to evaluate the hysteretic performance of Q690 high-strength steel box-section beam–columns and to assess the rationality of applying Eurocode 3 (EC3) to classify cross-sections of high-strength steel, three non-thin-walled welded box-section beam–columns were designed, and horizontal cyclic loading tests under constant axial force were undertaken. The hysteretic response of the specimens was analyzed from the standpoint of the failure mode, the degree of plastic evolution in the cross-section, energy dissipation capacity and ductility. Following this, numerical models verified from the experimental results were used for a parametric analysis to obtain the hysteretic response over a wider range of variables. The test results show that the local buckling failure of the plate at the base of the beam–column determines the failure mode of all three specimens. For a low axial compression ratio, a section with small width to thickness ratio may experience fracture. The parameter analysis showed that there is a flange-web interaction, and the evolution of cross-section plasticity under axial force is also related to the plate width to thickness ratio. In addition, through an analysis of the degree of plasticity in the cross-section under different parameter combinations, it is found that the classification of high-strength steel box-sections by the current specification is not rational, and that EC3 may be unreliable for 690 MPa box-section columns with Class 1 and Class 2 cross-sections, especially with a large axial compression ratio. A new cross-section classification method suitable for high-strength steel columns considering the influence of web-flange interaction and axial compression should be explored.