Carrying Capacity and Failure Mode of Impact-Damaged FRC Beams

Many concrete structures might be exposed to accidental or induced impacts during their service life. In case of moderate-rate impacts (e.g. rock falls, vehicle hits, etc), reinforced concrete (RC) elements may suffer significant damage even though a complete collapse does not necessarily occur. In such cases, the remaining load carrying capacity or residual performance needs to be assessed in order to ensure the users’ safety or make a decision on the necessity of repair or demolish. The use of fiber-reinforced concrete (FRC) for structures subjected to impacts has been proven to increase the structural strength. Though impact events may lead to severe cracking, spalling or other damage mechanisms, the residual capacity of FRC structures might still be considerable. However, very few specific studies have dealt with the evaluation of impact-damaged structures. In the present contribution, a discussion on the residual capacity and failure mode of FRC beams is presented based on experimental results of beams subjected to a drop-weight impact and a subsequent quasi-static test to failure. Interestingly, it is found that the failure mode of impact-damaged elements can differ from the one of comparative elements, which were not subjected to previous impacts. Also the residual capacity is dependent on the damage level caused by the impact.