Performance of Steel-Reinforced Concrete Beam-to-Column Joints after Exposure to Fire

Abstract

This paper presents a numerical analysis on the postfire behavior of steel-reinforced concrete (SRC) column to axially and rotationally restrained SRC beam joints. A finite-element analysis (FEA) model was developed to simulate the reaction of the composite joints under an entire loading and fire phase, including ambient temperature loading, heating, and cooling with constant loads and postfire loading. For validation, the proposed modeling method was used to simulate the results of SRC joint postfire tests and SRC column and joint fire-resistance tests. The comparison demonstrates the accuracy of the proposed FEA model. Based on the validated FEA model, the failure modes of SRC joints with restrained beams were investigated, and the joint deformation and internal force development during the entire loading and fire phase were analyzed. Afterward, two important parameters, namely, residual joint strength index and residual stiffness index, were defined based on the joint moment versus relative rotation angle curve, to quantify the postfire performance of the composite joints. Through regression analysis, formulas were developed to calculate the residual joint strength index and residual stiffness index.