Numerical modelling of integral abutment bridges under seasonal thermal cycles

Abstract

Interest in integral abutment bridges (IABs) from the industry has increased in recent years. IABs are robust bridges without joints and bearings and hence they are durable and virtually maintenance free; moreover, the resulting cost-saving associated with their construction is significant, a fact that makes IABs appealing to agencies, contractors and consultants. However, their use in long-span bridges is limited by the complex soil–structure interaction. Thermal movements, horizontal loads and dynamic actions are transferred directly to the backfill soil, leading to settlements, ratcheting effects, high earth pressures and deterioration of the backfill soil. The longer the integral bridge the greater the challenge, as movements are increased. This paper provides an extended review of the techniques used in the international literature and in practice to alleviate the interaction between a bridge abutment and the backfill. Subsequently, the performance of an innovative isolation system for IABs using recycled tyres as a compressible inclusion is studied using detailed numerical models of a representative three-span IAB. The proposed isolation scheme was found to be an effective and sustainable method to isolate the structure from the backfill soil, reducing the pressures experienced by the abutments and the residual vertical displacements of the backfill soil.