Low-Velocity Impact Response of Small-Scale RC Beams Strengthened with CFRP: Experimental and Numerical Investigation

The collision between an external body and a structural system is an extreme condition that must be considered in certain cases, such as vehicle–bridge impacts, iceberg–offshore structure collisions, and projectile impacts from explosions or by falling objects. The presented study investigates the low-velocity impact behaviour of small-scale reinforced concrete (RC) beams strengthened with carbon-fibre-reinforced polymer (CFRP) under drop-weight impact loading through experimental testing and numerical simulations. The beams with a span length of 0.5 m were subjected to impact loads at varying drop heights (0.5 m and 1 m) with varying levels of CFRP flexural strengthening (unstrengthened control, single layer, and two layers). At a 0.5 m drop height, CFRP strengthening demonstrated a significant reduction in mid-span deformations by 50% and an increase in support reaction forces by 43%, compared to unstrengthened specimens. However, at higher impact energy (1 m drop height), strengthening effectiveness decreased due to a transition from flexural failure to CFRP-end shear failure. The findings highlight the effectiveness of CFRP strengthening in improving impact resistance within certain energy limits, beyond which more critical failure mechanism are activated. Furthermore, a validated three-dimensional numerical model enabled detailed visualization of crack propagation, revealing dominant-shear-crack development at higher impact energies, which suggests that additional shear strengthening, such as CFRP U-wraps at FRP ends, may be necessary for improved performance.