Experimental study on seismic behaviour of cover-plate joints in high strength steel frames

Abstract

Improved configurations of beam-to-column joints are required to avoid brittle fractures in earthquakes in the design of high strength steel frames, and the cover-plate beam-to-column joints are expected to be effective to reinforce the welded flange-bolted web joints with negligible additional requirements for construction space and have potential for applications in seismic design of high strength steel frames. A total of 6 specimens of high strength steel double-sided cover-plate beam-to-column joints, considering three different combinations of 345 MPa or 460 MPa steel beams and 460 MPa or 730 MPa steel columns, were designed according to the Chinese code and tested subjected to cyclic loads with axial compressions in columns in consideration. The failure modes, the resistance, the stiffness and the ductility of the specimens were analyzed, and the influences of the panel zone thickness, cover-plate length, attached fillet weld in web connection and shape of the weld access whole were evaluated. According to the test results, continuity plates with sufficient thickness in high strength steel cover-plate joints were necessary to avoid unexpected failure modes, and the panel zone shear rotation would make a considerable contribution to the total story drift angle and the plastic story drift angle of the high strength steel frames. All the 6 specimens reach a story drift angle larger than 0.035 rad with 4 of them larger than 0.04 rad, indicating that the high strength steel cover-plate joint may develop considerable ductility. However, the evaluation methods of joint ductility in high strength steel frames should be further discussed because of the significantly increased elastic deformability of high strength steel members. Based on the test results, design recommendations were proposed for high strength steel cover-plate beam-to-column joints.