Failure modes and transformation laws of reinforced concrete slabs under drop hammer impact

With the change of the main influencing factors such as structural configuration and impact conditions, reinforced concrete slabs exhibit different mechanical behaviors with different failure patterns, and the failure modes are transformed. In order to reveal the failure mode and transformation rule of reinforced concrete slabs under impact loads, a dynamic impact response test was carried out using a drop hammer test device. The dynamic data pertaining to the impact force, support reaction force, structural displacement, and reinforcement strain were obtained through the use of digital image correlation technology (DIC), impact force measurement, and strain measurement. The analysis of the ultimate damage state of the reinforced concrete slab identified four distinct types of impact failure modes: local failure by stamping, overall failure by stamping, local-overall coupling failure, and local failure by punching. Additionally, the influence laws of hammerhead shape, hammer height, and reinforcement ratio on the dynamic response and failure mode transformation of the slab were revealed. The results indicate that: (1) The local damage to the slab by the plane hammer is readily apparent, while the overall damage by the spherical hammer is more pronounced. (2) In comparison to the high reinforcement ratio slabs, the overall bending resistance of the low reinforcement ratio slabs is significantly inferior, and the slab back exhibits further cracks. (3) As the hammer height increases, the slab failure mode undergoes a transformation, shifting from local failure by stamping and overall failure by stamping to local-overall coupling failure and local failure by punching. (4) Three failure mode thresholds have been established, and by comparing the peak impact force with the failure thresholds, the failure mode of the slab can be effectively determined.