Numerical investigation on dynamic response of reinforced concrete pier columns retrofitted with frp wraps under vehicle collision

Recent years, the vehicle-column collision has occasionally occurred at the existing reinforce concrete (RC) bridge piers, and increasingly posed a threat to the pier column, even the entire bridge. Shear failure is commonly the dominant failure mode for pier column collapse after vehicle collision, which should be avoided since it is a brittle failure and decrease the structural ability to dissipate impact energy. To prevent shear failure and reduce the damage of pier columns under vehicle collision, some effective measures on the existing RC bridge pier columns should be taken. This study is attempting to wrap fiber reinforced polymer (FRP) composites around pier columns to achieve this purpose. Previous studies have demonstrated the effectiveness of applying FRP wraps around RC beams on avoiding shear failure when suffering drop-weight impact loads. However, the understanding on dynamic behavior of RC pier columns strengthened with FRP wraps against vehicle collision is still unclear, due to the difference of impact forces induced by the drop-weight impact and vehicle collision. In this study, finite element numerical simulations are performed to investigate the effectiveness of FRP wrapping scheme on the prevention of shear failure of pier columns under vehicle impact. Parametric studies are designed to investigate the effect of critical factors on the dynamic behavior of pier columns strengthened with FRP composites, such as vehicle velocity and layer number of FRP wraps. The numerical results show that the FRP strengthening can significantly reduce the horizontal deflection of the pier column and change the failure pattern from shear mode to flexure mode with the increase of FRP amounts. There are little differences for FRP-retrofitted pier columns on the impact force during bumper and engine impacts, but visible differences during cargo impact, which is more obvious with the increase of FRP amounts and vehicular velocity.