SHEAR DISTRIBUTION IN SIMPLY SUPPORTED SKEW COMPOSITE BRIDGES

Composite steel-concrete bridges remain one of the most common types b uilt. Proper design of new bridges and evaluation of existing bridges requires accurate prediction of their structural response to truck loa ds. The American Association of State Highway and Transportation Offic ials has traditionally applied a load distribution factor for both mom ent and shear. The Ontario Highway Bridge Design Code (OHBDC) consider s several parameters in establishing load distribution factors for mom ent. However, the method is limited to bridges with skew parameters le ss than a certain value specified in the code. The presence of skew re duces the longitudinal moments in the girders. However, it also causes high concentration of shear in the girder closest to the obtuse corne r and reduces shear concentration in the girder closest to the acute c orner as well as in the interior girders. Therefore, shear should be c onsidered in the design of such bridges. In this paper, the influence of skew on the shear distribution factor is investigated. The influenc es of other factors such as girder spacing, bridge aspect ratio, numbe r of lanes, number of girders, end diaphragms, and intermediate cross- beams are presented. An experimental program was conducted on six simp ly supported skew composite steel-concrete bridge models. Results from a finite element analysis showed excellent agreement with the experim ental results. An extensive parametric study was conducted on prototyp e composite bridges subjected to OHBDC truck loading. The parametric s tudy included more than 400 cases. The data generated were used to dev elop empirical formulas for shear distribution factors for OHBDC truck loading and also for dead load. An illustrative example is presented.