Field Monitoring and Analysis of Abutment Foundation Behavior for a Curved Integral Abutment Bridge under Thermal Loading

The construction of integral abutment bridges (IABs), including semi-IABs, has increased substantially in the past two decades, partly because of reduced construction and maintenance costs. However, temperature-driven lateral movements, associated with the elimination of expansion joints, lead to a complex interaction between the bridge structure and the soils behind and under the abutment, which could result in soil densification, void formation, and settlement in the approach slab. The bridge's structure, geometry, and location all play an essential role in how the IAB responds to those movements. In addition, if the IAB is curved, it brings more complexity to its behavior. Nonetheless, there has been very little research on the behavior of curved IABs to date. This study investigates the behavior of a newly constructed curved IAB via field monitoring and numerical simulation. Field measurements included the backfill pressure, horizontal translation, and rotation imposed on the abutments during seasonal thermal fluctuations. The abutments rotate and translate toward backfill in summer and away from it in winter because of thermal expansion and contraction of the superstructure. Such thermal movements contributed to the increase in the lateral pressure to 85 kPa in the first year and to 140 kPa in the second year of monitoring. This implies that irreversible deformation may occur during seasonal temperature changes, supported by the monitored displacements. The bridge curvature, different skew angles at both ends, and the abutment geometry resulted in different movements and backfill pressures at each corner. A numerical simulation is also performed to provide more insights into the behavior of the curved IAB with more seasonal temperature cycles.