| In concrete bridge deck slabs supported on longitudinal girders, longitudinal cracks are developed to initiate the arching action. When the deck slab is confined externally, as in steel-free concrete deck slabs, and contains no crack-control grid, longitudinal cracks tend to be quite wide.; This study investigates the fatigue behaviour of a cast-in-situ full-scale concrete bridge deck slab with various kinds of internal reinforcement. The deck slab was cast-in-situ compositely on two steel girders at a center-to-center spacing of 2.0 m through the use of shear connectors, with a 500 mm long cantilever overhang beyond the center of the each girder. In the longitudinal direction, the deck slab was 9.0 m long and 175 mm thick. Although cast monolithically, this full-scale 9.0 m long model of a deck slab was divided into three 3.0 m segments (A, B and C). Segments B and C were both confined externally with steel straps and contained a crack control grid of CFRP and a GFRP respectively. Segment A was confined internally and contained two meshes of steel reinforcement. To investigate fatigue behaviour, a cyclic load was applied through a hydraulic actuator; and the performance of all three segments of the concrete bridge deck slab was monitored using a number of sensors, including linear variable displacement transducers (LVDTs), strain gauges, pi-gauges and linear motion transducers (LMTs).; Each of the three slab segments was tested under a central pulsating load representing the dual tires of a heavy truck. In each cycle, the pulsating load peaked at approximately 25 tonne and all three segments completed 1,000,000 cycles which satisfied the serviceability criterion. All three segments failed under a cyclic load which peaked at 60 tonne. The internally confined Segment A, with two meshes of steel bars, failed after 23,162 cycles. The externally confined deck slabs, Segment B with a crack control grid of CFRP, failed after 198,863 cycles, and the Segment C, with GFRP crack control grid, failed after 420,682 cycles. This outcome shows that deck slabs having the same thickness but confined differently have significantly different fatigue resistance. An internally confined deck slab with two meshes of steel bars has the least fatigue resistance, whereas an externally confined deck slab has the most favourable fatigue resistance.; On the basis of measured data, this study concluded that the externally confined deck slab with a GFRP crack control grid provides the best fatigue resistance for concrete bridge deck slabs. (Abstract shortened by UMI.)... |
