Behavior of FRP–concrete–steel double skin tubular members under lateral impact : experimental study

In this paper, an experimental investigation on the impact performance of FRP–concrete–steel double skin tubular members is presented. Twenty-four tests were carried out to examine the failure modes and the time histories of the impact forces, lateral deformations and strains. The effects of the impact energy and number of FRP layers on the impact behavior of the double skin tubular members were discussed. The results show that FRP–concrete–steel double skin tubular members behave in a ductile manner; there is a long stabilized stage of impact forces and the residual deformation mainly results from the cracking of FRP and concrete, as well as the overall bending deformation. The confinement of the outer FRP layers in the hoop direction to the sandwiched concrete in the composite members is small during the whole impact process. However, increasing the number of the outer FRP layers is somewhat beneficial to improve the dynamic resistance ability. The effect of the impact energy on the dynamic response of the composite members is significant. The difference between the FRP–concrete–steel double skin tubular members, concrete filled double skin steel tubes and concrete filled steel tubes is discussed based on the test results in this paper.