Impact Loading of Concrete Beams Externally Strengthened with CFRP Laminates

Abstract

The quasi-static behavior of flexural members strengthened with carbon fiber reinforced polymer (CFRP) laminates has been well documented in recent years, but there is a gap in knowledge regarding the effects of dynamic and impact loading of such members. This paper presents the test results of four 8 m beams externally strengthened for flexure, two with CFRP laminates and two with steel plates. Impact loading was induced by lifting one end of the simply supported beams and dropping it from given heights. The strain rates induced in the CFRP laminates were at least three orders of magnitude greater than the strain rates used for testing CFRP laminate coupons in tension. Comparisons are made between the dynamic impact behavior of the beams strengthened with CFRP laminates and steel plates, and the behavior of both beam types is modeled using an equation of motion. The beams externally strengthened with CFRP laminates performed well under impact loading, although they could not provide the same energy absorption as the beams externally strengthened with steel plates. Additional anchoring, at least at the ends of the CFRP laminates, would improve the impact resistance of these beams. Good predictions were made with the derived equation of motion by using the flexural stiffness of the beams at their ultimate limit state.