Stiffness of non-skew monolithic bridge abutments for seismic analysis

Abstract

A simple analytic model is developed to describe the stiffness of non-skew monolithic highway bridge abutments for purposes of seismic bridge analysis. The model permits an evaluation of six equivalent discrete spring stiffnesses for three translational and three rotational degrees-of-freedom of the abutment and includes effects of the abutment walls, pile foundations and soil. These springs can be incorporated as boundary elements in a more detailed finite element analysis of the dynamic response of the bridge superstructure. A parametric study examines a range of abutment stiffnesses for 2, 4 and 6 lane highway bridges. Application of the model to a single span bridge indicates the importance of including abutment stiffness in the determination of bridge frequencies and mode shapes in the transverse and vertical directions.