Parametric Study of Concrete Integral Abutment Bridges

A parametric study was conducted to extend the results of an experimental program on a concrete integral abutment (IA) bridge in Rochester, MN to other integral abutment bridges with different design variables including pile type, size, orientation, depth of fixity, and type of surrounding soil, fixity of the connection between the abutment pile cap and abutment diaphragm, bridge span and length, and size and orientation of the wingwalls. The numerical results indicated that bridge length and soil types surrounding the piles had a significant impact on the behavior of IA bridges. To select pile type and orientation, there is a need to balance the stresses in the piles with the stresses in the superstructure for long IA bridges or IA bridges in stiff soils. Plastic hinge formation is possible at the pile section near the pile head for combined critical variables, such as long span, compliant piles in weak axis bending, deep girders, and stiff soils. Because large pile curvatures or stresses may be caused due to the rotation of the pile cap during temperature increases, hinged connections between the abutment pile cap and diaphragm are not recommended for the practice of IA bridges. Cast-in-place piles are recommended only for short-span IA bridges because their relatively large bending stiffness can cause large superstructure concrete stresses during temperature changes.