Report No.: CCEER 95-01

Authors: Raj Siddharthan, Mahmoud El-Gamal, and Emmanuel A. Maragakis

Date: June 1995

Sponsoring Agency: Nevada Department of Transportation

Performing Organization:

Department of Civil Engineering/258

University of Nevada, Reno

Reno, NV 89557

Executive Summary:

This report presents an efficient approach to evaluate the nonlinear translational spring stiffnesses to represent seat-type abutments. The applicability of previous studies is limited because such studies are incapable of handling many important factors such as the nonlinear soil behavior, the free-field strains induced by an earthquake, the influence of wing walls, and the difference in soil behavior under active and passive conditions. The proposed approach accounts for all of these factors. The procedures adopted in this approach are relatively simple, and emphasis has been placed on easy interpretation and on achieving consistency between design procedures routinely used in the static and seismic design of abutments. Only routinely used soil properties, such as the relative density, unit weight, angle of internal friction, and interface friction angles, are required in the model.

The proposed approach has been used to develop ready to use design curves to estimate abutment stiffnesses. The design curves have been developed as a function of the height and width of the abutment and the seismic coefficient, k_h (Equation 16). Modification factors have also been developed to account for changes in the baseline parameters used in the development of the design curves (Equation 19). The applicability of the proposed approach has also been verified using recently completed large-scale abutment field tests (Summary by authors).