Multi-parameter evaluation of sustainable seismic retrofitting strategies for a three-span reinforced concrete bridge

The recently increasing number of bridge failures underscores the urgency of assessment and, where necessary, seismic retrofitting or replacement. While various retrofit solutions can improve seismic capacity in line with code-based requirements, selecting the most appropriate intervention should balance multiple, often conflicting, objectives that extend beyond structural performance and direct construction costs alone. This study describes the use of a Multi Criteria Decision Making (MCDM) framework to evaluate seismic retrofit strategies for a three-span RC bridge located in Italy. The analysis includes both the as-built configuration and four retrofitting alternatives: reinforced concrete jacketing, steel jacketing, Fibre-Reinforced Polymer (FRP) confinement of piers, and seismic isolation of the deck, all designed according to the currently enforced Italian code (i.e., NTC 2018). Each configuration is assessed in terms of non-linear response under two distinct seismic hazard levels estimated through multiple stripe analysis. Key decision variables (DVs) belonging to different categories, such as economic, social, technical and environmental, are quantified. To assess environmental impact, a Life Cycle Assessment (LCA) approach is adopted using the Environmentally Extended Input-Output LCA (EEIO-LCA) database. The comparison of the retrofit options using the MCDM framework shows how DVs associated with environmental sustainability, which are often neglected in traditional engineering assessments, may influence the preferred solution ranking. It also highlights trade-offs between seismic performance, cost, and sustainability. Ultimately, the findings enable for engineers on evidence-based selection of retrofit alternatives that meet both seismic and sustainability goals.