In recent years, integral abutment bridges (jointless bridges) have been increasingly used in Canada due to their low construction and maintenance costs. However, accepted equations in current Canadian Highway Bridge Design Code, CHBDC, to determine girder live load distribution factors for such bridges do not exist. Accordingly, the objective of this study was to develop new equations to estimate girder live load distribution factors for single-span integral abutment bridges. First, detailed 2D and 3D finite-element models (FEMs) of integral abutment bridges were developed. Then, a parametric study was performed to study the effects of various substructure and superstructure properties on girder distribution factors. The key parameters considered in this study were abutment height, abutment thickness, wingwall length, wingwall orientation, number of design lanes, span length, girder spacing and the presence and number of intermediate diaphragms. The results obtained from the finite-element models were then compared with the available live load distribution factors obtained from using the Simplified Method of Analysis specified in CHBDC. The results indicated that the live load distribution factors obtained from the FEMs were lower than those obtained from current CHBDC equations. Consequently, sets of empirical expressions were developed in the form of reduction factors that can be applied to CHBDC live load distribution factors for slab-on-girder bridges to accurately calculate the girder distribution factors of integral abutment bridges.
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