DEVELOPMENT OF DESIGN CRITERIA FOR SIMPLY SUPPORTED SKEW SLAB-AND-GIRDER BRIDGES. FINAL REPORT

Elastic analyses, using the finite element method, were done on 108 single span skew slab-and-girder bridges. Each structure had 5 girders and stiffnesses were representative of bridges with pretensioned I-girders or steel I-beam. Spans ranged from 40 to 80 ft, girder spacings from 6 to 9 ft, and the skew angle from zero to 60 degrees. The loadings were multiple point loads representing two HS20 AASHTO vehicles, and the loads were positioned to produce maximum bending moments in the girders. Convergence studies to evaluate the precision of the finite element models were also done, and comparisons were made with the results of other studies. An extensive parametric study was done to determine the most important variables and to gain an understanding of the response of the skew bridge. Expressions for the design moments in interior and exterior girders were then developed. These take into account the span and spacing of girders, the stiffness of the girders relative to the slab stiffness, and the angle of skew. The format is the use of the static moment for a girder, with modifications to this moment based on girder span and spacing, slab to girder stiffness ratio, and skew angle. A similar study was done to obtain factors for the calculation of deflections, starting with the deflection of a simple beam.