Joint KDOT-MoDOT: Evaluation of FRP Repair Method for Cracked PC Bridge Members

This research program was undertaken to investigate the effects that carbon fiber reinforced polymers (CFRP) have on the shear strength of under-reinforced, lab-scale prestressed concrete (PC) bridge girders. Many bridges in the states of Missouri and Kansas are structurally deficient and require either repair or replacement to ensure functionality. CFRP can offer a cost- and time-effective solution to these problems. For this purpose, 6 lab-scale PC bridge tee-girders were constructed for testing. Two girders were shear sufficient according to today's standards. The remaining 4 girders were shear deficient and required upgrade in order to achieve the same level of shear capacity as the shear-sufficient girders. The shear strengthening of these girders was performed using CFRP laminates applied by manual lay-up and near surface mounted CFRP bars. All beams, with the exception of the control one (i.e., a shear-deficient beam), were also strengthened in flexure using CFRP laminates. The observed failure mode of all strengthened beams was CFRP debonding. The flexural FRP laminate on each girder debonded before other failure modes could be experienced. Despite this, the three shear-strengthened girders did achieve a significant increase in load capacity over the control girder. Compared with the analytical prediction according to existing design guidelines, the shear-strengthened girders showed load carrying capacities equal to 1.01, 0.97 and 0.87 of the predicted value. Had flexural FRP laminate debonding not been the cause of failure, a closer match with prediction would have been possible.