Coupled Thermally Activated Fracture Kinetics and Damage Evolution in Steel Fiber-Reinforced Concrete (SFRC) under Dynamic Response

This study introduces a novel thermofluctuation-based constitutive model for predicting the dynamic compressive behavior of Steel Fiber-Reinforced Concrete (SFRC) under high strain rate loading, with relevance to extreme structural applications. The model incorporates a unique combination of rate-dependent damage mechanics and atomic-scale thermal fluctuation theory to accurately capture the fracture mechanisms in SFRC, which are influenced by both time and temperature. Experimental validation is carried out using data from Split Hopkinson Pressure Bar (SHPB) tests, revealing a substantial increase in dynamic compressive strength, from 40 MPa (quasi-static) to 92 MPa at a strain rate of 78 s⁻¹ and 6% fiber content. Furthermore, the model predicts significant improvements in the modulus of elasticity (26.5 GPa to 29.3 GPa) and estimates failure lifetimes with a deviation of less than 5% from experimental results. The dynamic-to-static strength ratio is observed to reach up to 3.0, highlighting SFRC’s sensitivity to strain rate effects. This work offers a comprehensive framework for simulating SFRC’s performance under extreme loading conditions, providing critical insights for the design of resilient and efficient concrete structures subjected to dynamic and thermal extremes.