Development of design criteria for simply supported skew slab and girder bridges

Elastic analyses, using the finite element method, were done on 108 \nsingle span skew slab-and-girder bridges. Each structure had 5 girders and \nstiffnesses were representative of bridges with pretensioned I-girders or \nsteel I-beams. Spans ranged from 40 to 80 ft, girder spacings from 6 to 9 \nft, and the skew angle from zero to 60 degrees. The loadings were multiple \npoint loads representing two HS20 AASHTO vehicles, and the loads were \npositioned to produce maximum bending moments in the girders. Convergence \nstudies to evaluate the precision of the finite element models were also \ndone, and comparisons were made with the results of other studies. \nAn extensive parametric study was done to determine the most important \nvariables and to gain an understanding of the response of the skew bridge. \nExpressions for the design moments in interior and exterior girders were \nthen developed. These take into account the span and spacing of girders, \nthe stiffness of the girders relative to the slab stiffness, and the angle \nof skew. The format is the use of the static moment for a girder, with \nmodifications to this moment based on girder span and spacing, slab to \ngirder stiffness ratio, and skew angle. A similar study was done to obtain \nfactors for the calculation of deflections, starting with the deflection of \na simple beam.