Experimental and Analytical Investigation of Stiffness and Ultimate Capacity of Bridge Abutments: Fid-Bau Portal

Experimental and Analytical Investigation of Stiffness and Ultimate Capacity of Bridge Abutments

A. Bozorgzadeh / S. A. Ashford / J. I. Restrepo / N. Nimityongskul

Abutments are earth-retaining structures which provide resistance to deformation and earthquake induced inertial forces from the bridge superstructure. In order to limit the inertial forces transmitted into the abutment walls and piles, the abutment walls are designed to be sheared off in major seismic events. Therefore, the force-resistance mechanism of bridge abutments in the longitudinal direction is mainly provided by backwall-soil interaction, and the passive earth pressure of the structure backfill of the abutments. Current design practice in California makes use of the bi-linear load-deformation curve and does not account for the structure backfill properties. This experimental and analytical research program was conducted to investigate the effect of the structure backfill properties, area of structure backfill, backfill height, and vertical wall movement on the abutment capacity and stiffness. The experimental program included five large-scale tests. The study shows that soil properties, abutment geometry, and the area of structure backfill play important roles in ultimate capacity and stiffness of bridge abutments, and an evaluation of the current Caltrans procedure is provided in this context. In addition, forcases where post-peak softening behavior is deemed to be important in system modeling efforts, an improved soil spring model for predicting the stiffness and capacity of the bridge abutments in longitudinal direction is proposed.