Effect of high-temperature transient creep on response of reinforced concrete columns in fire

Abstract

Structural members experience significant creep deformations in later stages of fire exposure, and are susceptible to failure due to high-temperature creep effects. However, in current practice creep deformations are not fully accounted for in evaluating fire resistance. This paper presents an approach to account for high-temperature transient creep in evaluating fire resistance of reinforced concrete (RC) columns. A three dimensional finite element based numerical model is built in ABAQUS to trace the behavior of RC columns under fire. Temperature induced transient creep strains in concrete and reinforcing steel are explicitly accounted for in the analysis. The model also accounts for temperature induced degradation in concrete and reinforcing steel, and material and geometrical nonlinearities. The model is applied to evaluate the effect of high-temperature creep on the response of fire exposed RC columns. Results from the analysis clearly indicate that high-temperature transient creep significantly influence the extent of deformations when the temperatures in concrete exceed 500 °C, and this in turn influences failure time of RC columns. Thus, neglecting temperature dependent transient creep strains can lead to underestimation of predicted deformations and this can result in un-conservative fire resistance estimation in RC columns.