NCHRP Report 543, Effective Slab Width for Composite Steel Bridge Members, contains the findings of research performed to develop expressions for the effective slab width of composite steel bridge members. Accompanying CRP-CD-56 contains extensive supporting information, including the recommended specifications and design examples.

The determination of the section properties of composite steel bridge members is influenced by the effective slab width assumed in their calculation. These section properties include the stiffness, which is used to determine the distribution of forces in the structure, and the section modulus, which is used to determine the stresses induced in the member by these forces. As such, the determination of effective slab width directly affects the computed moments, shears, torques, and deflections for the composite section and also affects the proportions of the steel section and the number of shear connectors required. The effective slab width is particularly important for serviceability checks, which can often govern the design.

The objective of this research was to develop recommended revisions to the AASHTO specifications for the effective slab width of composite steel bridge members. The recommended specifications are applicable to all types of composite steel bridge superstructures and are suitable for design office use