Stiffness Analysis at Failure State of Reinforced Concrete and Prestressed Concrete Tubular Members Under Internal Blast Loading

Large civil infrastructure, such as nuclear power plant containment vessels, is predominantly constructed using prestressed concrete (PSC) or reinforced concrete (RC). Previous experimental studies investigated the internal blast responses of reduced-scale open-ended reinforced concrete containment vessel (RCCV) and prestressed concrete containment vessel (PCCV), providing insight into displacement-based structural behavior. However, these studies were limited by the inability to directly measure internally reflected wall pressures and by the lack of experimental data for enclosed boundary conditions. In this study, a displacement-calibrated LS-DYNA simulation framework is developed to extend prior experimental findings to both open-ended and enclosed RCCV and PCCV configurations. An internal detonation of ammonium nitrate–fuel oil (ANFO) is simulated at the center of a cylindrical vessel. The simulation models are calibrated using reduced-scale open-ended experimental displacement time histories. Simulation results are post-processed to construct force–displacement relationships based on discrete load–displacement points across charge levels and their bilinear regression. Using the resulting stiffness indices and a stiffness-based scaling procedure, failure-inducing internal blast loads are estimated for real-scale vessels under conditions where direct internal pressure measurement is not feasible. The proposed framework enables response-based assessment of semi-confined internal explosions and supports model-informed safety evaluation of containment-type structures.