Deformation-Based Protective Performance Assessment of the Entrance-Side Front Wall of a Double-Door-Type RC Covered Artillery Position Under Frontal Standoff Blast Loading

Verification of the blast resistance capacity of military protective structures is generally conducted through experimental testing; however, repeated experiments are limited due to spatial, temporal, economic, and safety constraints. Accordingly, this study evaluated the global deformation-based protective performance of the entrance-side front wall of a covered artillery position (double-door type) using three-dimensional numerical analysis based on ANSYS AUTODYN. The blast scenario was defined as a frontal standoff blast using a 00.0 kg TNT-equivalent charge, corresponding to a 000 kg class munition with a charge-to-weight ratio of 00%, at a standoff distance of 0.0 m. A coupled fluid–structure interaction analysis was applied to consider the interaction between the blast pressure transmission medium and the reinforced concrete structure. The entrance-side front wall surrounding the double-door opening was selected as the primary evaluation member because it is directly exposed to the incoming blast wave and forms part of the entrance zone of the facility. The analysis results showed that the maximum wall-applied reflected pressure was 1487.6 kPa at approximately 5.8 ms, and the maximum front-wall displacement was 0.505 mm at approximately 7.0 ms. The support rotation angle calculated from the maximum displacement was 0.012° based on a wall height of 2.3 m, which was within the elastic design limit of 0–2° specified in UFC 3-340-02. Therefore, under the specified numerical scenario, the entrance-side front wall was assessed to remain within the Protection Level A limit based on the UFC support rotation criterion. (The standoff distance and TNT charge weight are masked under the restriction on disclosure due to military secrets).