Investigation on the Dynamic Response and Failure Mode of Clay Brick Masonry Walls Under Long-Duration Explosion

Masonry structures are widely used in civil engineering due to their favorable load-bearing capacity and construction efficiency; however, the threat posed by long-duration blast loads from industrial accidents and large-yield explosions has become increasingly prominent. Existing research has primarily focused on the response of masonry walls under conventional short-duration explosions, while systematic investigations remain limited regarding the differentiated failure mechanisms induced by long-duration blasts. To address this gap, this study adopts and validates a full-scale simplified micro-modeling approach for clay brick masonry walls using LS-DYNA. The model enables systematic comparison of long-duration blast loads and conventional blast loads simulated by the CONWEP method under equal peak overpressure and equal impulse conditions. Numerical results indicate that, under equal peak overpressure (0.18 MPa), the long-duration blast load induces global deformation and cumulative damage leading to complete collapse, whereas the conventional blast load results in only elastic response. Under equal impulse (13.5 kPa·s), both loads cause severe damage, yet the conventional blast load triggers instantaneous localized fragmentation with a higher collapse rate, while the long-duration blast load governs failure through sustained overpressure-induced global deformation and crack propagation. The comparison of mid-span displacement–time histories across different loading cases further quantifies these distinct failure modes, revealing fundamentally different deformation development rates and collapse characteristics. The key contributions of this study are summarized as follows: A validated simplified micro-model is developed that reproduces the experimental damage patterns of masonry walls. A comparison identifies and mechanistically explains the differentiated failure modes between the two load types. Under the conditions considered in this study, critical transition thresholds of peak overpressure and impulse governing the damage mode shift from minor cracking to global collapse are determined. These findings provide a scientific basis for distinguishing blast-resistant design strategies for masonry structures according to explosion type.