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• A number of pre-damaged beams strengthened with CFRP were tested under multiple impact. • The failure patterns are different under different CFRP strengthening methods. • U-wrapping CFRP has better performance. • A new FEM simulation for multi-impact was tested. In this study, low-velocity impact loads were first applied to produce pre-damages in three reinforced concrete (RC) beams, followed by strengthening with carbon fiber reinforced plastic (CFRP) and reloading under multi-impact. Two strengthening types, say, in straight and U-wrapping ways, were considered in the tests to determine which type is more effective to resist impact load. Furthermore, a 3D nonlinear finite element model was established to compare the experimental results and hopefully to investigate deeply in exploring other reinforcement measures. The results show that cracks of beams with U-wrapping CFRP are mainly concentrated in the mid-span area, and the crack distribution range is significantly reduced compared with un-strengthened RC beams or beams strengthened with straight CFRP. It can be concluded that CFRP can help to improve the performance of the pre-damaged beam, decrease the stiffness loss due to damage and enhance energy dissipation. The deformation recovery capacity of CFRP-strengthened beams is also enhanced under multi-impact, particularly in U-wrapping CFRP beams. In addition, the multi-impact performance in terms of the cracking pattern, impact force, and displacement history can be well visualized in the numerical simulation. [ABSTRACT FROM AUTHOR]

• The dynamic behavior of CFRC strengthen RC beam was studied by three-point bending tests with a drop-hammer impact device. • CFRP can significantly improve the impact resistance of beams. • The DIC method was used to capture the initiation and propagation process of impact multiple-cracks. • The propagation speed of impact multiple-cracks was measured based on the strain field obtained by DIC. In this paper, impact behaviors of reinforced concrete (RC) beam and carbon fiber reinforced plastic (CFRP) strengthen RC beam (CFRP-RC beam), including the damage process, failure pattern, impact force peak value and peak deflection were investigated by means of using three-point bending tests with a drop-hammer impact device. A high-speed camera combined with digital image correlation (DIC) method was used to capture the initiation and propagation process of impact multiple-cracks and to record the cracking strain. The results showed that the changes of hammer impact height and bonded CFRP on beams had different effects on dynamic response of beams, and they also caused change of failure pattern of beams. Introduce of CFRP can significantly reduce the crack widths and mid-span deflections of beams and improve the impact resistance of beams. In addition, the crack velocity in RC beam was inhibited effectively by CFRP, however, the inhibitory effect declined as impact velocity increased. [ABSTRACT FROM AUTHOR]