Dynamic assessment of RC and steel structures under progressive collapse with consideration of strain rate

Strain rate effects play a vital role in evaluating the structural responses under dynamic loading. Accordingly, a nonlinear single-degree-of-freedom model incorporating strain rate effects is developed in this study to determine the dynamic progressive collapse responses of steel and reinforced concrete (RC) structures, utilizing the dynamic increase factor (DIF)-strain rate model while encompassing both the structural static and dynamic resistance. Previous experimental results are used to validate the proposed static and dynamic models. The study reveals the impacts of DIF-strain rate models and solution methods on the structural dynamic responses. Furthermore, incremental dynamic analysis (IDA) and fragility analysis are utilized to evaluate dynamic responses of steel and RC structures. Findings demonstrate that the proposed model reasonably predicts the structural progressive collapse responses, with prediction accuracy improving by over 10 % when strain rate effects are considered. Structural sensitivity to strain rate is most pronounced in the small deformation stage, and in RC structures this effect is predominantly governed by the reinforcement. These findings underscore the necessity of incorporating steel strain rate effects in flexural and compressive arch actions for anti-progressive collapse design. IDA and fragility results indicate that RC structures exhibiting performance intermediate between steel structures with rigid and weak connections.