Design Implications of Creep and Shrinkage in Integral Abutment Bridges


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Title: Design Implications of Creep and Shrinkage in Integral Abutment Bridges

Author(s): M. Arockiasamy and M. Sivakumar

Publication: Special Publication

Volume: 227


Appears on pages(s): 85-106

Keywords: continuous composite structures; creep; integral abutment bridges; restraining moment; shrinkage

Date: 3/1/2005

Integral abutment bridges are becoming popular among a number of transportation agencies owing to the benefits, arising from elimination of expensive joints, installation, and reduced maintenance cost. Unlike framed structures, in addition to the effects of creep, shrinkage, and temperature, integral bridges are also subjected to the soil¬substructure-superstructure interaction. The analysis of these bridges requires realistic modeling that can include the time-dependent material behavior. Statical indeterminacy in the structure introduces time-dependent variations in the redundant forces. An analytical model is developed in which the redundant forces in the integral abutment bridges are derived considering the time-dependent effects of creep and shrinkage. The analysis includes nonlinearity due to cracking of the concrete, as well as the time dependent deformations of composite cross section due to creep, shrinkage and temperature. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) approaches are considered in modeling the time dependent material behavior. Age-adjusted effective modulus method with relaxation procedure is used to include the creep behavior of concrete. The partial restraint provided by the abutment-pile-soil system is modeled using discrete spring stiffness for translational and rotational degrees of freedom. The effects of creep and shrinkage on the service life are illustrated and the results from the analytical model are compared with the published field test data of a two-span continuous integral abutment bridge.