Numerical Simulations of Steel Integral Abutment Bridges under Thermal Loading

Although integral abutment bridges (IABs) can reduce construction and maintenance costs compared with conventional jointed bridges, certain aspects of their structural behavior are still not well understood. Most prior IAB research was related to substructure behavior, and as a result, most limit states that have been considered in design guidelines have been based on substructure considerations. However, integral abutment construction also affects superstructure behavior and demands, and superstructure properties directly influence substructure behavior. This paper presents numerical simulations evaluating the behavior of IABs with composite steel I-girders subjected to temperature changes consistent with seasonal fluctuations in the state of Illinois. Bridge superstructures, abutments, piers, and pile foundations were modeled to determine various structural demands imposed by these temperature changes. A suite of nonlinear bridge models is introduced in which key bridge parameters were varied, such as overall bridge length, intermediate-span length, pile size, and skew. Results indicate that effective expansion length (EEL) has a primary influence on bridge longitudinal movement under thermal loads regardless of girder, abutment, or pile design. Also, results show that superstructure girder response (elastic) and substructure pile response (inelastic) to superstructure temperature change are influenced by parameters such as EEL, pile size, skew, and the rotational restraint that the superstructure imposes on the substructure. Results presented herein suggest that superstructure geometry should be directly or indirectly considered in IAB substructure design, and that thermally induced stresses and strains should be accounted for in superstructure and substructure design.