Effect of global stiffness on the force response of thin GFRP reinforced concrete slabs subjected to impact loading

Abstract

The purpose of present study is to investigate the effect of global stiffness on the force response of thin GFRP reinforced concrete slabs simply supported by steel beams under drop-weight impact. Considering the strain rate effect of GFRP bars and concrete materials, a numerical model of GFRP-RC slabs was established and verified. The dynamic equilibrium relationship of the impact force, reaction force and inertial force was analyzed and intuitively explained from the velocity and displacement. Meanwhile, the effects of the global stiffness by varying the slab length, slab thickness and reinforcement ratio on the acceleration distribution, characteristic value of impact force and reaction force, failure pattern, displacement distribution and energy dissipation were evaluated in more detail. Eventually, the semi-empirical formulas considering key parameters were proposed to predict the reaction force time history of simply-supported RC/FRP-RC slabs under drop hammer impact. The results show that the effect of the slab stiffness by varying the slab length and thickness on the reaction force is significant, while the influence of reinforcement ratio is not obvious. The effect of global stiffness of the slab on the plateau value of the reaction force is similar to that on the plateau value of the impact force. The effect of the slab stiffness by varying the slab thickness and reinforcement ratio on the displacement is obvious, while varying the slab length hardly affects the deformation. The fitting equation considering key parameters can predict the simplified reaction force time history of simply-supported RC/FRP-RC slabs under impact loading. However, more experimental validation and extensive parametric studies are needed to improve their accuracy and applicability.