Bridge Abutments: Formulation of Simple Model for Earthquake Response Analysis

Abstract

A two‐part analytical model is developed to assist in seismic response analysis of highway bridges that have abutments supported on earth embankments. In the first part of the model, an expression is developed for identification of the fundamental transverse frequency of the earth embankment. In the second part, two simple equivalent springs are used to represent the transverse and vertical stiffness of a monolithic abutment system. The springs are based on linear elastic plane‐strain analysis of a typical trapezoidal‐shaped embankment cross section. The spring stiffnesses are related to the cross‐sectional dimensions and the soil properties of the earth embankment, which supports the bridge abutments. These stiffnesses can be incorporated into a detailed dynamic model of the superstructure as the equivalent stiffnesses of the bridge abutments. The frequency and the translational stiffnesses predicted by the model are in good agreement with results from a more complicated analytic theory and from finite element analysis of the abutment soil system. A companion paper illustrates an application of the model and provides comparisons to recorded earthquake responses.