Influence of bond on the fatigue behavior of reinforced concrete beams without stirrups

This paper demonstrates the application of nonlinear finite element analysis for studying the behavior of shear-critical reinforced concrete beams with fully and non-bonded longitudinal reinforcement under monotonic and fatigue loading. The analysis platform employed has a built-in direct-path integration scheme which enables the simulation of high cycle fatigue problems. Nonlinear behavior of concrete under repetitive loading is represented by the integration of time-dependent and fatigue constitutive models using the multi-directional fixed-crack approach. The simulation results show that the nature of concrete cracking in the two beams is highly influenced by the bond between concrete and reinforcement. The removal of bond is shown to result in an enhancement in load capacity and deformability, which confirms the experimental evidence. When subjected to fatigue, however, the beam with non-bonded reinforcement is shown to display a significant increase in displacement amplitude and a reduction in fatigue life. A comparable fatigue life to the beam with conventional reinforcement is achieved when the enhancement in load capacity is not considered.