Effect of Bearing Pad Arrangement on Capacity of Slab Panel Bridge Members

Slab panel bridges (elsewhere referred to as flat-slab bridges) are constructed with multiple precast pretensioned slab panels that are placed side by side and act compositely with a cast-in-place concrete topping. Design standards from the Florida Department of Transportation specify that individual slab panels be supported by a tripod system of bearing pads. A single bearing pad is placed at one end, and two bearing pads at the opposite end. This paper presents experimental research on the effect that this bearing pad arrangement has on the behavior and capacity of slab panel members. Four full-scale tests on slab panels were conducted, with variables that included the bearing pad arrangement (single or double bearing), and the position of the load point [shear span-to-depth (a/d) ratio of 2.0 and 3.3]. For slab panels loaded at a/d of 3.3, test results indicated that the behavior and capacity were independent of the bearing pad arrangement. For the panel loaded at a/d of 2.0 with a single bearing pad, the failure mode was bond shear. The panel loaded at a/d of 2.0 with two bearing pads failed in flexure. Experimental results were compared with theoretical capacities calculated with American Concrete Institute and AASHTO codes. Design recommendations were made on the basis of the experimental results and on the comparison with theoretical capacities.