Nonlinear Analysis of Integral Bridges: Finite-Element Model

Integral abutment bridges (IABs) are jointless bridges where the deck is continuous and connected monolithically with the abutment walls. The biggest uncertainty in the design of these bridges is the reaction of the soil behind the abutments and next to the foundation piles, especially during thermal expansion. This lateral soil reaction is inherently nonlinear and is a function of the magnitude and nature of the wall displacement. Handling the soil-structure interaction in the design of IABs has always been problematic, usually requiring iterative, equivalent linear analysis. This paper describes the implementation of a full 3D finite-element model of an IAB system which explicitly incorporates the nonlinear soil response. This paper also presents the results from a small parametric study on a sample bridge where the soil compaction levels in the cohesionless soils behind the wall and adjacent to the piles were varied. These results show that the level of compaction in the granular backfill strongly dominates the overall soil reaction, and that this reaction greatly impacts the overall structural response of the bridge system.