Experimental Evaluation of Connections in Hybrid Precast Concrete Bridge Truss Girders

An innovative, corrosion-free, precast, prestressed concrete truss girder has been developed for short- and medium-span, slab-on-girder bridges. The girder consists of top and bottom concrete flanges connected by precast vertical and diagonal members and made of fiber-reinforced polymer (FRP) tubes filled with concrete. The verticals and diagonals are connected, respectively, to the concrete flanges by means of glass FRP dowels and stud reinforcement made of corrosion-resistant steel or FRP material. The flanges are pretensioned with carbon FRP tendons. The deck slab is reinforced with corrosion-resistant steel bars in the bottom transverse layer and with glass FRP bars in the bottom longitudinal and the top layers. The girders may be posttensioned with external carbon FRP tendons to balance the slab weight and to provide continuity in multispan bridges. The new system has the advantages of light weight and enhanced durability. The light weight reduces the initial cost and allows for longer spans. The improved durability reduces the maintenance cost and extends the structure's life span. This paper describes the general details of the system and presents an experimental evaluation of its critical components, namely, the FRP tubes and the truss connections. Two types of FRP tubes and four types of connections were investigated. The results are presented of tests of eight connection specimens under static loading and four specimens under fatigue. The tests showed excellent performance of the connections when filament-wound tubes and continuous double-headed studs were used.