Retrofitting Short-Span Precast Channel Beam Bridges Constructed without Shear Reinforcement

Abstract

This paper investigates retrofitting precast, nonprestressed, channel beams (PCB) used in short-span bridges to improve beam shear strength and, consequently, beam ductility. Three retrofit approaches were investigated: applying carbon-fiber-reinforced polymer (CFRP) strips, applying an epoxy spray-on, and retrofitting by installing shear bars within the stems of the precast channel beam. Implanting shear bars into each precast channel beam stem was found to be the optimal retrofit based on improved beam strength, installation ease, and economics. The suitability of the shear bar retrofit was further explored by implementing the shear bar retrofit at a short-span precast channel beam bridge. Precast channel beam sections cast without shear reinforcement were used to construct Arkansas Bridge #02992 over the Flat Hollow Branch Creek. The bridge was constructed in 1955, but several of the beams used in the original construction have since been replaced with better-condition similar-style beams. The bridge is made up of four simple spans. Each span consists of 5.79-m (19-ft) precast channel beams cast without shear reinforcement. Five interior beams along with two exterior beams were placed side-by-side to develop the 7.62-m (25-ft) overall bridge cross section. Each interior beam has a width of 1.07 m (3 ft-6 in.), and each exterior beam has a width of 1.14 m (3 ft-9 in.). The exterior beams are slightly wider than the interior beams to incorporate the roadway curb within the cross section. During the implementation study, live-load distribution and dynamic-load amplification for a precast channel beam bridge were investigated.