Dynamic Response and Failure Mechanism Analysis of Precast Parking Structures Under Falling Double-Tee Impacts

For nonrigid floor systems, collapse occurs if the in-plane deformation exceeds the length of the end support. Structural collapses typically result in numerous fatalities, substantial property losses, and significant societal impacts. Preventing progressive collapse necessitates thorough analysis and improvement of the structures' impact resistance, as well as a study of their load resistance mechanisms. This paper analyzed the internal forces and bearing capacity of structures, examining the effects of connection stiffness and impact velocity on impact resistance under end impact and mid-span impact scenarios. An analytical technique for evaluating the bearing capacity of floor systems under falling impact was developed, along with recommendations for the impact resistance design of large-span precast parking structures. The results demonstrate that the stiffness of the floor-to-floor connections is crucial for maintaining the stability of the impacted floor and preventing progressive collapse. With increased impact velocity, the flexural and shear deformation of the impacted double-tees significantly increases, often resulting in penetrating shear cracks. These cracks cause the impacted double-tees to become unstable and fall, along with the upper falling double-tees, continuing to impact the lower double-tees at higher speed and mass, leading to progressive collapse of the structure.