Investigation of the post-blast fire performance of RC members

Abstract

An explosion or blast can trigger a subsequent fire in the building structure. In the case of reinforced concrete (RC) structures, blast loading can result in relatively large residual deformations and locked-in stresses in the affected members prior to fire exposure. Such residual deformations and locked-in stresses can have a detrimental effect on the subsequent fire performance of RC members. Accordingly, this paper presents results from a numerical study investigating the post-blast fire (PBF) performance of isolated RC columns. A simplified numerical model was developed to implement the integrated environment for modeling the interaction between blast and PBF scenarios without employing complex user-defined subroutines in ABAQUS. The developed FE model was validated against the experimental blast and fire tests. The RC column was subjected to blast loads of distinct scaled distances (Z) simulating the far-field and near-field scenarios. Further, the blast-damaged columns were exposed to a standard fire and evaluated the PBF performance. Results indicated that the fire resistance period (FRP) of RC columns is significantly reduced by prior blast damage, with reductions ranging from 0.8 % to 72 % as Z decreases from 2 to 0.8 m/kg1/3. Consequently, to mitigate these detrimental blast effects and ensure adequate PBF resistance, a transverse reinforcement with a diamond configuration in the plastified region of the RC column is recommended. Furthermore, the study explores the impact of axial load levels on RC column performance under PBF scenarios. It's observed that an increase in axial load levels beyond 25 % of the critical axial load-bearing capacity results in a 100 % reduction in the post-blast FRP of the RC columns. Additionally, Pressure-Impulse (P-I) diagrams are developed examining the blast cases that yield specific post-blast FRP for the RC columns. Notably, the diamond configuration demonstrates superior blast resistance for the same post-blast FRP, as evidenced by the P-I diagrams.