Experimental and numerical investigation of freeze-thaw damaged RC beams subject to impact loading

The degradation of concrete mechanical properties induced by freeze-thaw cycles (FTCs) reduces bridge load-bearing capacity, prompting much concern about their impact on dynamic behavior. Drop-weight impact tests on freeze-thaw damaged reinforced concrete (RC) beams were conducted, and failure mechanisms and impact resistance were investigated. Considering the non-uniform degradation of concrete mechanical properties, caused by freeze-thaw damage gradients at different depths, a three-dimensional nonlinear finite element model for RC beams under impact loads was established. Using the validated model, the effects of the number of FTCs, impact velocities, reinforcement ratios, and stirrup ratios on the impact resistance performance of the beam subjected to FTCs were explored. As the degree of freeze-thaw damage increased and impact velocity rose, the failure mode of RC beams became more transitioned from flexural to shear failure. The effectiveness of increasing the stirrup ratio gradually decreased with the increase in the number of FTCs. Increasing the reinforcement ratio reduced the extent of stress damage at the top of the beam, but provided a limited increase to the local stiffness of freeze-thaw damaged RC beams.