Seismic performance and force transition mechanism of stepped joints through experimental and numerical analyses

This paper proposes a stepped beam-column joint featuring with flush flange surfaces in the connecting segment. Due to the joints’ innovative connection configuration, therefore, a serious of methods were adopted to illustrate its force transfer mechanism. Firstly, two full-scaled T-shaped joint specimens were designed. Through cyclic loading test, the failure modes of the joints were characterized as the opening deformation of endplate surfaces and the buckling of flange plates. Specifically, the hysteretic curves, skeleton curves and energy dissipation capacity of the specimens were analyzed. The test results indicated that the stepped joint exhibited favorable seismic performance. Consequently, detailed finite element (FE) models were established and verified against the test results. Furthermore, parametric analysis focused on endplate and flange thickness was conducted, illustrating that the increase of plate thickness caused variation in joint’s stress distribution and load-bearing capacity. Finally, based on the finite element analysis results, the force transmission mechanism through the connecting surfaces was elucidated, while the horizontal connection surface contributed to force transmission in the plastic stage.