Effect of elevated temperature on the low-velocity impact performances of GFRP reinforced concrete slabs

The objective of the present study is to study the impact resistance of GFRP reinforced concrete slabs under elevated temperature. Considering the high temperature softening effect and strain rate enhancement effect of FRP bars and concrete materials, the numerical model for the study of fire and impact resistance of GFRP reinforced concrete slabs were established and compared with the fire resistance test and drop hammer impact test respectively, which verified the rationality of the numerical model. The failure mechanism of GFRP reinforced concrete slabs under the combined action of high temperature and impact loading was analyzed. The influence of fire scenario (at high temperature or after natural cooling) and fire time on GFRP reinforced concrete slabs was revealed. Eventually, the residual bearing capacity of damaged slabs after high temperature and impact loading was obtained. The results show that high temperature significantly degrades the impact resistance of GFRP reinforced concrete slabs. The slab at high temperature shows worse impact resistance than the slab after cooling down. With the increase of fire time, the punching failure of GFRP reinforced concrete slabs become more serious while the central displacement of the slabs and the impact duration increase, accompanied by decreased impact force. Compared with RC slabs, the deformation and impact force of GFRP reinforced concrete slabs under impact loading are more affected by high temperature, while the residual bearing capacity is less affected. Under the combined action of fire and impact loading, the slab is mainly local damage while energy dissipated by concrete accounts for most of the impact energy absorbed by the slabs.