Analytical formulation for limit length of integral abutment bridges

The integral abutment bridge concept has recently become a topic of remarkable interest among bridge engineers, not only for newly built bridges but also for refurbishment processes. The sup er-structure of integral abut ment bridges (IABs) is made continuous through composite cast-in-place concrete deck slabs over pre-stressed concrete or steel girders. The system constituted by the substructure and the super-structure can achieve a composite action responding as a single structural unit; this princi ple is applicable also while converting existing simply supported bridges into IABs. Several guidelines for the design of IABs have been published in the last few years. The main idea is to introduce designers to this kind of structures thereby limiting the total length, skewness and inclination of the deck. The maximum length usually recommended for this kind of structures is around 100 m or less. This limitation is derived from the difficulties introduced by the need to control the soil- structure interaction for imposed temperature variations: This is the main factor affecting increasing of the overall length of the structure. Achieving the maximum length attainable with this kind of structures is intrinsically related to a thorough understanding of the soil- structure interaction behind the abutments or next to the foundation piles. It has been proved that the maximum allowed length for IABs is 400 m. The world record for the longest IAB, which represents the transformation of a simply supported flyover in Verona, Italy, will be discussed in this paper together with the non-linear parametric analyses carried out to determine the solution presented. The paper will deal with the possibility of achieving super-long IABs using standard pre-fabricated cross sections and typical reinforcement ratios for foundation elements and super-structure.