Experimental and analytical research on the seismic performance of CEEP joint

In this paper, the seismic performance of two cruciform extended end-plate (CEEP) joints was investigated through experimental and theoretical analysis methods. The low-frequency cyclic loading experiments were performed on the joints, and the failure modes, M−θ curves, strain distributions, and seismic performance indices, including hysteretic behaviors, skeleton curves, ductility coefficients, stiffness degradation, and energy dissipation coefficients, were obtained and compared. Experimentally-validated FEMs were applied to quantitatively investigate the specific effects of column web thickness, end-plate thickness, and bolt diameter on the joint performance. The critical stiffness value of rigid and semi-rigid joints was proposed based on the failure modes, FE results and initial stiffness, and it was demonstrated that the two joints were a semi-rigid and a rigid joint, respectively. The FE results showed that for the semi-rigid joints, increasing the column web thickness was the most effective method to improve the stiffness. For the rigid joints, increasing the end plate thickness was a cost-effective method to enhance the stiffness. A theoretical method to evaluate the initial stiffness of the CEEP joints was proposed, and the accuracy of the method was testified.