Finite-Element Analysis Methodology for Sequential Impact Events of Dry Storage Containers

Dry storage containers (DSCs) are required to endure consecutive high-energy drops during routine handling and transport. This study proposes a two-stage nonlinear finite element procedure to evaluate their cumulative elastic–plastic response. The model was stabilized after a 9 m oblique free-drop simulation until residual oscillations and stress-rate criteria were satisfied, and the resulting stress–strain field was used as the initial condition for the subsequent impact. Regulatory baseline analyses identified the 9 m oblique free drop and 1 m horizontal puncture as the most demanding Type B conditions; thus, these cases were systematically analyzed to assess the stabilization procedure’s effectiveness. The results confirmed that when a second impact occurs before the oscillatory responses of the first impact have stabilized, the peak von Mises stress and plastic strain in the canister increase markedly. Once stabilization is achieved, additional increases become negligible. All scenarios satisfied the limits specified in ASME BPVC Section III, Division 3. Strain-based evaluations revealed that impact spacing and sequence, rather than impact magnitude alone, govern the available design margin. The proposed approach reproduces cumulative impact behavior with minimal computational cost while enhancing physical fidelity and can be extended to other large shell structures subjected to repeated impacts.