Live Load Distribution in Girder Bridges Subject to Oversized Trucks

A significant challenge facing motor carriers and engineers in this nation is the limitation of vehicle size and weight based on pavement and bridge capacity. However, the current demands of society and industry occasionally require a truck to carry a load that exceeds the size and weight of the legal limit. In these cases, engineering analysis is required before a permit is issued to ensure the safety of the structures and roadways on the vehicle's route. A truck with a wheel gauge larger than the standard 1.83 m (6 ft) gauge requires additional engineering effort because the wheel load girder distribution factors (GDFs) established by AASHTO cannot be used to accurately estimate the live load in the girders. In this study, the finite-element method is used to develop modification factors for the AASHTO flexure and shear GDFs to account for oversized trucks. The results of the analysis showed that the use of the proposed modification factors with the specification-based GDFs can help increase the allowable loads on slab-on-girder bridges.