Soil Structure Interaction under Semi Static Loads in an Integral Abutment Bridge

To solve the durability problem of expansion joints and bearings, integral abutment bridges (IABs) have become increasingly popular. Soil Structure Interaction (SSI) is a fundamental aspect for reaching a thorough understanding of this type of structure not only for newly built bridges but also in the retrofitting of existing ones. Under imposed actions, e.g., horizontal expansion and contraction induced by thermal variation and time-dependent effects (creep and shrinkage), the connection between a super- and substructure responding as a frame structure makes IABs different from other conventional bridges that introduce forces due to SSI. Therefore, the overall horizontal stiffness is mainly due to i) the piles' stiffness, which is usually flexible enough to allow for the deformation of the superstructure and strong enough to carry out the vertical loads, and ii) the type of soil behind the bridge abutment, which has a different stiffness depending on its compaction and composition. Several approaches have been proposed in the literature to consider these types of interaction. In this paper, the accuracy of different formulations commonly used in IABs' design and based on p-y curves was evaluated. Formulations for piles and abutments were first introduced. Then, a fully integral abutment bridge built in China was considered as a case study. A finite element model of the bridge using SAP2000 software was implemented, and the influence of different methods and formulations was investigated. Finally, the obtained results for different types of soil and approaches were compared and discussed.