ABSTRACT
This chapter deals with highway bridge loads and load distribution as specified in the American Association of Highway and Transportation Officials Load and Resistance Factor Design (LRFD) Specifications. The permanent load is distributed to the girders by assigning to each all loads from superstructure elements within half the distance to the adjacent girder. The wheel load, however, may not be positioned any closer than 0.6 m from the lane line, or 0.3 m from the face of curb, barrier, or railing. For fatigue loading, the LRFD Specification uses the design truck alone with a constant axle spacing of 9 m. The load is placed to produce extreme force effects. After forces have been determined from the longitudinal load distribution and the longitudinal members have been designed, the designer may commence load distribution in the transverse direction for deck and substructure design. “Refined analysis” refers to a three-dimensional consideration of the loads and is to be used on more complex structures.
