Book Description

The analysis of bridge superstructures is complicated by the geometric boundaries and loading conditions. AASHTO Bridge Specifications contain a simple procedure used in the analysis and design of steel girder bridges. This procedure is to isolate individual girders subjected to a single line of w heel loads from a design truck and then calculate the maximum bending moments. The wheel loads are positioned on the girder to produce maximum bending moment which is then multiplied by an empirical distribution factor. Recently, these factors have been updated based on finite-clement analysis and parametric studies to include major bridge parameters such as: girder spacing, span length, and cross-sectional properties. The findings of previous research reported by the authors about the performance of common finite-element modeling techniques will be employed to investigate other bridge parameters thought to influence the wheel load distribution. Previous research reported in the literature did not investigate the effect of sidewalks and railings on the wheel load distribution in steel girder bridges, the current research will employ recommended dimensions for sidewalks and railings by the AASHTO Bridge Specifications to study their influence on the wheel load distribution. A typical one-span, two-lane, composite steel girder highway bridge was selected to perform the parametric study. The bridge superstructure will be idealized using: (a) quadrilateral plate bending and stretching (shell) elements for the concrete slab, sidewalk, and railing, and space frame elements for steel girders with the centroid of girders coinciding with the one of the concrete slab; (b) eight-node brick elements for the concrete slab, sidewalk, and railing, and quadrilateral shell elements for the flanges and web of the steel girders, This research wilt report the wheel load distribution results of bridges with various combinations of span lengths and girder spacings along with the presence of sidewalks and/or railings on one or both sides of the bridge cross-section The results will serve to assess the current AASHTO practice which is conservative by ignoring the presence of sidewalks and railing when evaluating or designing highway bridges.