Numerical analysis of the short-term response of a semi-integral bridge abutment subjected to cyclic lateral movements

Abstract This paper presents a numerical investigation of the daily cyclic response of the backfill-abutment system of a semi-integral bridge subjected to thermally induced lateral movements. A two-dimensional finite element model was developed to investigate lateral earth pressures on the abutment and deformations in the backfill soil resulting from expansion-contraction cycles of the superstructure over 100 daily cycles. The model was validated against field data from earth pressure cells installed on the retained soil side of the abutment. The validation process yielded a product-moment correlation coefficient of 0.95 and a mean absolute error of 1.96 kPa. The analysis shows that a daily displacement amplitude of ± 1.5 mm generates lateral pressure profiles with an approximate trapezoidal shape, differing from the triangular distributions assumed in existing integral bridge design methods. The evaluated design approaches yield deviations of up to 320% in resultant lateral force and up to 250% in overturning moment relative to the numerical results. In addition, the alternate lateral movements of the abutment cause progressive densification and shearing in the retained soil, forming a settlement trough that stretches laterally up to about one backfill height from the abutment wall. After 100 daily cycles, the maximum settlement reaches 8.1 mm, which corresponds to 32% of the 25-mm rutting limit, and the observed trend indicates that this limit may be reached after about 300 daily cycles. The findings of this research refine load estimates and provide practical guidance for the design and early service life maintenance of semi-integral bridge abutments in similar conditions.