Effect of Temperature Induced Bond Degradation on Fire Response of Reinforced Concrete Beams

Abstract

Reinforced concrete structures, when exposed to elevated temperatures lose load carrying capacity due to degradation in mechanical properties as well as deterioration in the interfacial bond between concrete and rebars. The extent of bond deterioration influences stress transfer between concrete and causes a reduction in load carrying capacity of reinforced concrete members. In this paper, the influence of temperature induced bond degradation on response of reinforced concrete beams exposed to fire is investigated. A finite element based numerical model is developed in ABAQUS for tracing the response of reinforced concrete beams exposed to fire. The interfacial bond between concrete and reinforcing steel is taken into account using zero thickness bond-link elements consisting of two orthogonal springs to transfer shear and normal forces in the transition zone between rebar and concrete. The non-linear behavior of the bond-link element is defined using temperature dependent interfacial bond stress-slip models proposed in literature. Predictions from the model are compared against measured response parameters during fire tests. It is illustrated that interfacial bond between reinforcing steel and concrete can significantly influence response of RC beams exposed to fire, and thus needs to be accounted for in evaluating fire resistance of RC members