Analysis on dynamic response and time-frequency characteristics of building structures subjected to blast influence

Blast-induced seismic waves and air-shock overpressures pose substantial threats to the structural integrity and safety of adjacent buildings. Due to stringent experimental requirements and complex theoretical modeling, accurately characterization the blasting response patterns and detailed time-frequency characteristics remains a notable challenge. Vibration monitoring experiments shows that blast vibrations have obvious directional differences and frequency selectivity in amplitude and time-frequency distribution. The longitudinal and tangential components exhibit a remarkable elevation amplification, while the vertical component fluctuates periodically. Vibration amplitude decreases with increasing blast-source depth. The time-domain responses and high-frequency components distributions are primarily governed by the floor elevation. As blasting vibrations propagate from the ground into buildings, the dominant frequency (DF) decreases and vibration energy shifts toward the lower frequency bands. Subsequently, a kinematic model for wall structures is established. Wall deflection decreases with increasing elastic modulus and wall thickness, with a gradually diminishing reduction rate; by contrast, deflection increases nearly linearly with applied pressure. Degraded structural constraints and prolonged loading duration intensify damped-vibration responses and amplify structural deflections. Numerical simulation results show that wall damage caused by air shock wave is dominated by horizontal cracks propagating along mortar joints, exhibiting a dispersed failure pattern; in comparison, seismic waves trigger additional diagonal and vertical cracks. Damage evolution is further affected by pre-existing cracks and window openings.