Collapse load analysis of continuous, posttensioned voided slab bridge models

Two voided slab bridge models, one straight and the other curved in plan, were tested to failure under simulated American Assoc. of State Highway and Transportation Officials (AASHTO) truck loading. Each model was quarter-scale, two-lane, continuous, and longitudinally and transversely posttensioned, with two equal spans of 8.0 m (26.27 ft) measured along the centerline, and were 2.0 m (6 ft 7 in.) wide. The curved bridge subtended an arc of 40° on a radius of curvature of 22.92 m (75.2 ft). The failure load was obtained for symmetrical placement of four simulated AASHTO trucks, one in each lane and each span. The observed failure mode in both bridge models was similar to that of a continuous beam, i.e., initiated by the formation of successive plastic hinges at the support and at the maximum positive moment location, respectively. The test results are compared against predictions from one-dimensional beam analysis and two-dimensional grillage analysis based on limit analysis using interaction relations for bending, shear, and torsion as failure criterion. Both analyses predict failure loads and failure modes that are in reasonable agreement, with test results from the one-dimensional analysis providing a somewhat higher estimate.