Simplified impact prediction and damage assessment of fire-exposed FRP-RC slabs

Abstract

Fiber-reinforced polymer (FRP) reinforced concrete structures are increasingly applied in buildings, bridges, dams and other infrastructure. However, most existing studies either examine fire and impact separately or depend on computationally intensive simulations. As a result, simplified analytical methods for evaluating the dynamic response of FRP-reinforced concrete (FRP-RC) slabs under coupling elevated temperature and impact loading remains limited. Motivated by this deficiency, this study presents a simplified analytical framework for evaluating the impact performance and damage of fire-exposed FRP-RC slabs. A coupled thermo-mechanical approach is proposed, integrating a nonlinear finite element heat transfer model with a two-degree-of-freedom (2DOF) dynamic system that simultaneously accounts for stress wave propagation, elevated temperature effect, and strain rate sensitivity. A layered cross-sectional analysis was used to derive temperature- and strain rate-dependent dynamic resistance functions, from which the equivalent stiffness k₂ was obtained. Together with other computable parameters, k₂ was incorporated into the 2DOF analytical model to predict impact force and mid-span displacement of FRP-RC slabs under coupling action of drop-weight impact and fire. Validation against numerous tested and simulated slabs demonstrated that the model achieved high prediction accuracy (R²>0.8) with low computational cost. Furthermore, empirical prediction equations were developed for rapid engineering applications, and a displacement-based damage assessment method was introduced. Impact mass-velocity (m-v) equivalent damage curves were constructed to quantify fire–impact performance, and parametric studies revealed that increasing slab thickness or applying fireproof coatings markedly improves structural resilience. In conclusion, the proposed framework effectively provides a physically-based and computationally efficient tool for performance-based design and quantitative damage evaluation of FRP-RC slabs under coupled fire-impact scenarios.