Behavior of Retrofitted UHPC Beams Using Carbon Fiber Composites under Impact Loads

In recent years, considerable attention has been focused on the use of ultra-high performance concrete (UHPC) in highway construction for its superior properties such as significantly higher compressive strength and tensile strength than conventional concrete, minimal long-term creep or shrinkage, and exceptional durability, which helps to reduce joint cracking and enhance load transfer in the structures. A 3-D finite element model for understanding the influence of impact loading is somewhat lacking. The response of a beam under impact loading might depend largely on the extent of the local damage experienced due to impact loads. This paper investigates the global structural response of UHPC beams strengthened using CFRP (carbon fiber reinforced polymers) under impact loads. Due to the lack of experimental and numerical research on this topic, the study is conducted using the explicit finite element computer program ABAQUS. The numerical study is verified using the results of strengthened reinforced concrete beams under static loads. Four beams were considered in this study; two conventional and two UHPC beams. Two of the four cases were analyzed without CFRP strengthening and the other two were with CFRP. The impact load was considered equivalent to initial velocity of 100 in/sec. acting at the midspan of all beams. It is concluded that modeling UHPC is feasible in ABAQUS however the lack of the UHPC stress-strain relationship. As anticipated, UHPC showed less deflection, more energy absorption and less concrete damage compared to conventional concrete.