Damage resistance of fiber reinforced polymer composites strengthened reinforced concrete columns exposed to blast loading

Assuming that the threat of a terrorist attack cannot be entirely eliminated, protective measures must be incorporated into reinforced concrete (RC) structures to mitigate the damage caused by explosive blast impacts and to prevent collapse. The primary objective of this study is therefore to evaluate the damage level of RC columns retrofitted with Fiber Reinforced Polymer (FRP) composites when subjected to high-amplitude, short-duration blast loads. A systematic investigation of various column strengthening techniques using FRP was conducted through blast simulations performed with LS-DYNA software. A finite element (FE) model of an RC column retrofitted with FRP composites was developed, including detailed discussion of material models, strain rate effects, and loading methods. Validation of the FE model was carried out against experimental test results. In this research, the residual axial capacity of the RC column was selected as the damage criterion. The results show that at a scaled distance of Z = 0.60 m / kg 1 / 3 , an unstrengthened RC column exhibits a damage degree of D = 0.52 (high damage category). Retrofitting with a 5 mm FRP wrap reduces the damage degree to D = 0.35 (a 33% reduction), while the combined FRP wrap and strips configuration achieves D = 0.20 (a 62% reduction, low damage category). Increasing FRP thickness beyond 5 mm provides diminishing returns. Furthermore, probabilistic fragility analysis is performed to quantify the probability of exceeding damage states, and empirical prediction equations are derived to relate damage degree to scaled distance for each retrofit configuration. These quantitative results demonstrate that FRP retrofitting, particularly the combined wrap and strips configuration, is highly effective in ensuring building protection under blast loading.