Retrofit of Existing Bridges with Concept of Integral Abutment Bridge: Static and Dynamic Parametric Analysis

The integral abutment bridge (IAB) constituted by the superstructure and the substructure can achieve a composite action responding as a single structural unit by eliminating or reducing expansion joints and bearings. Accordingly, the construction and maintenance costs can be reduced. Therefore, the IAB concept has recently become a topic of remarkable interest among bridge engineers, not only for newly built bridges but also during refurbishment processes. The research topic concerns the retrofit of existing bridges with the IAB concept. In order to investigate the retrofitting technique with the IAB concept, the literature survey on the practical applications of this approach in worldwide was carried out firstly, including retrofitting motivations, detailed processes and structural performance after retrofitting. Besides, another literature review on the critical issues of analysis on the IAB, such as soil-structure interactions, modelling approaches and plastic hinge simulations, was conducted in order to find out the most suitable method in modelling. The case study of a simply supported prestressed concrete bridge (named Viadotto Serrone) with three spans constructed in 1972 was analyzed, which has some durability problems nowadays. The finite element model was built, involving soil-structure interactions, non-linear behaviors and retrofitting processes. The original and updated Italian design codes are compared through static analysis and seismic analysis. Another investigation was conducted to prove the necessity of considering soil-structure interactions in the IAB. Based on the appropriate finite element model, a large number of static sensitive analyses were carried out, taking thermal actions; bridge types; soil conditions and substructure heights as parameters. Through analysing the responses of girders, piers, abutment stems and piles, some important factors and the corresponding influence were found, which could be adopted to guide the retrofitting technique with the IAB concept. Then, the verification was conducted in order to check if the existing sections could be reused without any changes and point out the most critical components, which need to be repaired or replaced. Moreover, the dynamic performance of bridge before and after retrofitting was investigated preliminarily through modal analysis and response spectrum analysis.