Sustainable strengthening of prestressed concrete bridge girders: an LCA-based comparative evaluation

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A large portion of the Italian bridge stock, built between the 1950s and 1970s with prestressed reinforced concrete (PRC) girders and post-tensioned cables, is nearing the end of its service life. These structures are increasingly vulnerable due to ageing, corrosion, heavier traffic loads, and insufficient maintenance, with prestressing cable deterioration being the most critical failure mechanism. The current Italian standard (LG2020) prescribes evaluation frameworks to identify structural deficiencies and assess residual capacity, often highlighting the need for strengthening interventions to restore safety and extend durability. Traditionally, the choice of intervention techniques has focused on structural performance, applicability, and cost. However, in the transition toward decarbonization and circularity, sustainability-oriented evaluations must be integrated into decision-making. This work proposes a qualitative life-cycle-based evaluation for the comparative assessment of strengthening interventions for PRC bridge girders, embedding Life Cycle Assessment (LCA) principles at a conceptual level. The methodology combines structural analyses with qualitative environmental and economic considerations, enabling the comparison of strategies such as jacketing systems, external post-tensioning, and composite-based solutions. The approach adopts a life-cycle perspective—covering material production, installation, maintenance and end-of-life stages—to support the integrated evaluation of performance, durability and resource efficiency. The framework is illustrated through a case study on an existing bridge girder, comparing different strengthening options in terms of structural effectiveness, cost implications and relative life-cycle sustainability. Integrating life-cycle thinking supports informed decision-making in the selection of retrofit strategies that ensure safety and serviceability while aligning with sustainability and resilience objectives in infrastructure management.