STATIC AND FATIGUE PERFORMANCE OF HYBRID PRECAST PRESTRESSED CONCRETE BRIDGE TRUSS GIRDERS

摘要

An innovative system for short and medium-span bridges comprising transversely spaced hybrid precast prestressed concrete truss girders and a cast-in-situ or precast concrete deck slab has been developed. The girders have top and bottom concrete chords connected by vertical compression and diagonal tension members made of concrete-filled fiber reinforced polymer (FRP) tubes. The vertical compression members are connected to the chords by means of dowels protruding from the ends. The diagonal tension members are connected to the chords using double-headed bars. The chords are pretensioned during fabrication. The girders may be post-tensioned by external tendons after erection to balance the slab weight and to provide continuity in multi-span bridges. All reinforcement and prestressing can be made of corrosion-resistant steel or glass and carbon FRP. The proposed truss girder is thus light in weight with enhanced durability. The light weight allows for longer spans and reduces the initial cost. The enhanced durability reduces the maintenance cost and leads to longer life span. An experimental evaluation of performance of large-scale truss girders under static and fatigue loading is presented. A total of ten girder specimens were fabricated and tested. All girders had identical cross-section dimensions with 1.2 m (4 ft) overall depth. Four of the girders consisted of 2, 4, 6, and 8 truss panels, respectively, with span lengths varying from 2.30 to 9.25 m (7.7 to 30.8 ft), and were tested under monotonic loading up to failure. The remaining six girders consisted of two truss panels each and were tested under cyclic fatigue loading of different level and amplitude. The post-fatigue resistance was also investigated. The tests showed excellent performance of the truss girders in terms of strength, stiffness, and fatigue life.