Structural analysis of reinforced concrete chimneys subjected to uncontrolled fire

We studied the behavior and residual structural capacity of reinforced concrete chimneys subjected to an uncontrolled fire. We used a combination of a heat transfer finite element model–to obtain the temporal distributions of temperature during the fire event–and the structural model of concrete chimney design provided by the American Concrete Institute (ACI 307–08). This approach allows estimating the reduction in the vertical (axial) strength and moment strength of the chimney both during a fire and post-fire, and gives a direct estimate of the reduction in the safety factors of the concrete chimney. Using this method, we examined the impact of various design parameters on the residual structural capacity of a concrete chimney subjected to an internal fire. An iterative finite element method was also presented as an alternative to the ACI 307 calculations. Moreover, finite element calculations were used to study the role of thermal stresses on the axial strength of the chimney during fire. Our study provides insight into possible failure mechanisms of concrete chimneys damaged due to fire and could suggest possible approaches for minimizing the risk of chimney failure due to an uncontrolled fire.