Soil–Structure Interaction of Curved–Integral–Abutment Bridges

This research focuses on the behavior of curved full integral abutment bridges (IAB) designed in Nebraska through field monitoring and numerical simulation to study the complex behavior of curved integral abutment bridges, and recommend maximum lengths and curvatures for this type of bridge. The research team instrumented an IAB in Big Springs, Nebraska following the construction schedules of the bridge between Jan. 2020 to Aug. 2021, and measured the abutment backfill pressure, abutment tilts, backfill moisture, and pile movement profiles. This study documents the field measurements conducted between April 2021 to July 2022, including a complete annual cycle since the bridge has been functioning as a full integral bridge. A three–dimensional finite element model was developed, and the analysis is compared with the field measurements. A parametric study was conducted on curved IABs with different characteristics. These parameters include length, radius of curvature, pile type, soil type, bearing, and shrinkage models. Results show that the total length of the bridge and the longitudinal displacements of the bridge is approximately linearly related regardless of the bridge curvature. A bridge with a smaller radius of curvature exhibits larger lateral displacements, however. Except for bridges shorter than 200–ft, the maximum stress at pile–abutment connection appears to follow a linear relationship with the bridge length. Although the displacements of ACI 209R and CEB–FIP 90 shrinkage models differ in the first couple of years after the bridge is fully integral, both models show comparable displacements at the end of their cycles (5 years). According to the results, the type of soil surrounding the pile has little to no effect on bridge displacements when piles are placed inside a long CMP sleeve (18 ft). The simulation results demonstrate that pile types and orientations do not affect longitudinal displacements while having little impact on lateral displacements. However, the pile head moments and stresses differ by the type and orientation of the piles. The largest bending moments at the pile–abutment connection is in the order of weak axis H piles, pipe piles, and strong axis H piles