Experimental and numerical research on the multi-stage seismic failure modes of steel frame with end-plate connection

To study the multi-stage seismic failure mode of semi-rigid plane steel frame with end-plate connection, one 1/2-scale specimen of the quasi-static cyclic test was conducted. According to the failure criteria, the mechanical characteristics and the failure process of the specimen at three performance stages (the elastic stage, the elastoplastic stage, and the ultimate stage) were studied. The bearing capacity, stiffness degradation, and the plastic energy dissipation of the test specimen were also analyzed. Moreover, a nonlinear finite element model of the specimen was implemented in the ABAQUS platform to compare and verify the test results, and a parametric analysis was conducted to investigate the influence of the thickness ratio (delta = t(e)/t(f)) of the end-plate (t(e)) to the column flange (t(f)) on frame performance. The specimen has reliable energy dissipation capacity and ductility, and the lateral displacement of the first story accounted for about 40% of the second story displacement, while this ratio increased to 50% in the ultimate stage. The increase of delta can significantly improve the lateral stiffness and bearing capacity of the specimens, but the ductility decreases gradually. The failure order of the specimen was the yield of the end-plate, the yield of the beam end, the buckling of the column base, and the failure of the whole frame, which indicated that the specimen satisfied the design criteria of "strong column weak beam".