Numerical Evaluation of a Semi-Integral Bridge Abutment under Cyclic Thermal Movements

Abstract

This paper presents a two-dimensional Finite Element (FE) simulation of the interaction between a semi-integral stub-type concrete bridge abutment and a granular backfill under cycles of temperature-induced lateral displacements. A numerical model was proposed utilizing an elastoplastic soil constitutive model considering the characteristics of a semi-integral bridge abutment located near the City of Palestine, Texas, USA. The numerical model was validated against data collected in the field from pressure cells installed on the soil side of the abutment of the semi-integral bridge. The long-term response of the backfill-abutment system representing a 50-year period was investigated numerically for annual cycles of expansion–contraction of the bridge. According to the results of the investigation, it is observed that annual cyclic lateral movements of the bridge abutment led to a rapid increase of lateral earth pressures upon the abutment wall. The locus of maximum lateral earth pressures occurred on the upper third of the abutment, which disagrees with the conventional earth pressure distributions often assumed in design guidelines for integral bridge abutments. The magnitude of the settlement trough that formed under annual cycles is deemed sufficient to negatively affect bridge performance soon after start of the bridge operation. Results predicted that cumulative shear strains prevailed in the region of the backfill soil far from the abutment wall. On the other hand, cumulative compressive volumetric strains (densification) dominated in the vicinity of the soil-abutment interface. While stabilization of lateral earth pressures on the soil-abutment interface was predicted to occur with the balance between both densification and shearing effects, settlements adjacent to the soil-abutment interface were predicted to persist as a consequence of the continued growth of cumulative shear strains (ratcheting) in the portion of the soil away from the abutment wall.