Fire performance of concrete filled steel tubular (CFST) column to RC beam joints

The performance of concrete filled steel tubular—(CFST) column to reinforced concrete (RC) beam joints under fire is investigated in this paper. A three-dimensional finite element analysis (FEA) model is developed for sequentially coupled heat transfer and structural analysis. Four tests on circular CFST column to RC beam joints subjected to the ISO 834 standard fire performed earlier by the authors' research group are reviewed and used to verify the model. The FEA model is then used to construct the model of a typical full-scale CFST column to RC beam joint and perform analysis to the behavior of this joint in fire with respect to effects of parameters such as beam load ratio, column load ratio and beam to column linear stiffness ratio. Failure criteria in the International Standard ISO 834-1 are adopted to investigate the fire resistance and the failure modes. Extensive studies are also performed to the internal force redistribution, the joint stiffness degradation and typical failure modes in the joint. The results indicate that three typical failure modes of beam failure, column failure, and simultaneous beam and column failure should be considered in the design of composite joints under fire loading.

► CFST column to RC beam joints subjected to fire.
► Finite element analysis model developed for the composite joint.
► Parameter analysis.
► Failure modes and fire resistance of the composite joint.