Fatigue Life Simulation of RC Bridge Slab with Initial Defects under Water

Abstract

Initial defects and water have a significant influence on the fatigue behavior of RC bridge slab. Specially, since the RC bridge slab has a relatively high surface-to-volume ratio, initial cracks tend to be generated on the surface with respect to dry shrinkage during curing stage, and therefore the durability and the long-time serviceability of the bridge slab under severe environmental conditions would be influenced significantly. However in the majority of practical cases, this risk is generally omitted in the design stage. The object of this work is to establish a quantitative understanding about the influence of initial defects as well as water on the fatigue performance of RC bridge slab. Here, the fatigue behavior of RC bridge slab subjected to central fixed pulsating loads is experimentally investigated and analytically simulated with full three-dimensional nonlinear finite element analysis. 7 full-size slab specimens are systematically designed with initial defects by means of intentionally inducing dry shrinkage or artificial damage before loading. Then upper surface of some specimens are implemented to water-exposure condition, while other specimens are loaded in dry condition as comparison. According to experimental results, water is found to cause dramatic reduction in fatigue life of RC bridge slab, at least one order shorter than that of air loading cases. The three-dimensional fatigue damage simulation successfully predicts the characteristic mode of failure under fixed-point pulsation. Importantly, analysis indicates that the initial stiffness is reduced and the ultimate failure mode is altered from flexural to shear punching due to dry shrinkage, accordingly the fatigue life of RC slabs is clearly shortened.