Residual behavior of reinforced steel fiber-reinforced concrete beams damaged by impact

The awareness of damage caused by impacts in civil structures has increased during the last decades. Existing research has shown that impact strength of concrete structures can be improved with the addition of steel fibers, but little attention has been paid at the assessment of the structural condition after the impact. In fact, the residual capacity of reinforced steel fiber-reinforced concrete (SFRC) can be considered as one of the main advantages of the employ of SFRC in structures expected to suffer impact damage. The understanding of the residual capacity of impact-damaged structures, in terms of strength and energy absorption, might be decisive to safely perform evacuation and recovery operations, as well as evaluate rehabilitation tasks. This paper presents a research on the residual capacity of preimpacted reinforced SFRC beams. Seven mixtures of SFRC are evaluated, including three types of steel fibers and two values of fiber amount (as well as companion unreinforced plain concrete mixture). The research includes an experimental campaign as well as a model to understand the contribution of the SFRC to the strength and ductility of undamaged and damaged specimens. Among the conclusions, it has been found out that the failure mode (i.e., shear- or flexure-governed) of damaged specimens depends on the crack pattern caused by the impact, and it can be different from the failure mode of undamaged specimens.