Fire resistance and flexural load capacity of beam-column welded-bolted hybrid connection joints under post-earthquake fire

This paper investigates the fire resistance and flexural load capacity of beam-column welded-bolted hybrid connection joints (BWHJ) considering the gradient temperature effect under post-earthquake fire (PEF). A computation model of the BWHJ was established using ANSYS. The accuracy and effectiveness of the computational model were validated by comparing with available experimental results. Gradient temperature distribution on beam-column welded-bolted hybrid connection joints was obtained by temperature field analysis. 25 finite element models were created to conduct parameter analysis (width-to-thickness ratio of column flange (alpha), height-to-thickness ratio of column web (i), height-to-thickness ratio of column stiffener (gamma), width-to-thickness ratio of beam flange (delta), height-to-thickness ratio of beam web (beta) and damage variable ((D) over tilde)). Finally, the calculation method for the flexural load capacity of the BWHJ under PEF was proposed. The results showed that the fire resistance time of the BWHJ decrease with the increase of the damage variable. The parameter i has a clear effect on the failure mode of the BWHJ, and parameters i, delta, beta, and (D) over tilde have a significant impact on the PEF performance of the BWHJ. The reduction of flexural capacity caused by damage variables is greater than that caused by temperature. The research findings can provide basic data, theoretical references, and technical support for design and study under PEF.