FATIGUE BEHAVIOUR OF HYBRID FRP-CONCRETE BRIDGE TRUSS GIRDERS REINFORCED WITH SINGLE-HEADED BARS

摘要

A novel hybrid bridge system comprising transversely spaced precast prestressed concrete truss girders and a concrete deck cast or placed on top has been developed. The girders have top and bottom concrete chords connected by precast vertical and diagonal truss members made of glass fibre-reinforced polymer (GFRP) tubes filled with concrete. The vertical members, predominantly in compression, are connected to the concrete chords by means of dowels. The diagonals, mainly in tension, are connected to the chords using single-headed bars. The concrete chords provide the flexural capacity of the girder while the truss members resist the shear forces. 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 and durable. The light weight allows for longer spans and reduces the initial cost. The potential enhancement in durability reduces the maintenance cost and extends the structure's life span. An experimental evaluation of the behaviour of two-panel truss girders under static and fatigue loading is presented. A total of seven girder specimens were fabricated, of which six were tested under cyclic fatigue loading of different level and amplitude, and one was tested under monotonic loading for comparison. The post-fatigue resistance was also investigated. The test results have shown excellent performance of the truss girders under both static and fatigue loading.