Short-Term Structural Response of Integral Abutment Bridge Approach Slabs Subjected to Live Loading and Thermal Effects

Integral abutment bridges (IABs) are prevalent in the US due to their lower maintenance and construction costs, as well as longer service life. However, approach slabs at IABs experience complex demands owing to the fact that there are no expansion joints between the ends of a bridge and its approach slabs. To provide comprehensive field data on the response of IAB approach slabs, a four-lane IAB cast-inplace approach slab and a three-lane IAB precast approach slab were instrumented during construction to elucidate approach slab structural behavior due to live load and thermal effects. Static truck load tests were conducted at various traffic lanes and shoulder locations on each of the instrumented approach slabs. Finite-element analysis (FEA) models were developed to simulate slab behavior under controlled live loading and thermal effects. Numerical modeling of slabs subjected to truck loads is used to estimate the modulus of subbase support under the approach slab. The strain and stress results from numerical modeling are consistent with the truck-induced behavior measured in the field, validating key assumptions of approach slab boundary conditions. A nonlinear thermal gradient profile is proposed to improve the ability of the FEA models to properly capture slab behavior under thermal effects. Solar radiation is found to introduce peak stresses greater than the live load stresses. It is also observed that simplified structural analysis in practice (neglecting parapets) can significantly underestimate stresses in approach slab edge regions.