Quantifying transient creep effects on fire response of reinforced concrete columns

This paper quantifies effect of transient creep on response of reinforced concrete (RC) columns under severe fire exposure scenarios. A three-dimensional finite element model is built in ABAQUS to trace the influence of transient creep on RC columns under simultaneous loading and fire exposure. Temperature induced transient creep strains in concrete and reinforcing steel are explicitly accounted for in fire resistance analysis, together with property degradation in constituent materials, and associated material and geometrical nonlinearities. The model is applied to assess influence of transient creep on fire response of RC columns under different conditions, including different fire exposures, load levels, and number of exposed sides. Results from the numerical studies clearly indicate that severe fire exposure induces higher capacity degradation in RC columns in much shorter duration than exposure to a standard building fire. Moreover, asymmetric thermal gradients resulting from two or three side fire exposure on a column can increase transient creep effects and, thus, affect fire resistance. Overall, results from the analysis infer that neglecting transient creep can lead to lower estimation of axial displacements and, thus, overestimation of fire resistance in RC columns, particularly when subjected to severe fire scenarios and with higher thermal gradients.