PSI - Issue 84

Valentina Picciano et al. / Procedia Structural Integrity 84 (2026) 922–930

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1. Introduction A large portion of the existing bridge stock in Italy was constructed between the 1950s and 1970s, a period characterized by the extensive use of prestressed reinforced concrete (PRC) girders with post-tensioned cables. Over the decades, most of these structures have undergone limited or no systematic maintenance, leading to a progressive deterioration of their structural components (Di Prisco 2019). This construction typology is particularly vulnerable to durability-related issues, as the corrosion of prestressing tendons represents one of the most critical and difficult-to detect damage mechanisms (Godart 2020). As a result, the gradual loss of prestressing force may significantly reduce the load-bearing capacity of the girders, compromising both safety and serviceability. Moreover, the continuous increase in traffic loads, along with geometric and functional modifications introduced over time, has led to demand levels often exceeding those originally envisaged. The structural fragility of existing bridges is further highlighted by the numerous collapse events reported worldwide over recent decades, emphasizing the urgency of systematic assessment and intervention strategies (Deng et al. 2016). In this context, the Italian Guidelines (MIT 2020) for the classification and risk management, safety assessment, and monitoring of existing bridges have been introduced as a multi-level and multirisk framework to support the evaluation of existing infrastructure. While this framework primarily focuses on structural safety and risk classification, the growing emphasis on sustainability in the construction sector calls for the integration of additional criteria related to long-term environmental performance, durability, and resource efficiency (Passoni et al 2022). In recent years, the evaluation of strengthening and retrofit strategies for existing bridges has progressively evolved from purely performance- and cost-based approaches toward broader life-cycle-oriented perspectives. From this viewpoint, different intervention techniques that provide comparable structural benefits may exhibit significantly different implications in terms of material consumption, construction processes, maintenance requirements, and end of-life management. These aspects are particularly relevant in the current transition toward decarbonization and circularity, where assets’ management is increasingly expected to account for sustainability-related objectives alongside traditional engineering requirements (Milić and Bleiziffer 2024). Within this framework, the present study focuses on strengthening strategies for prestressed reinforced concrete bridge girders, with specific reference to post-tensioned systems commonly adopted in viaducts with grid deck configurations. A first objective is to provide an overview of the most widely adopted strengthening techniques, including traditional solutions, as well as more advanced approaches. Building upon this classification, the core contribution of this paper is the proposal of a qualitative life-cycle-based comparative evaluation for the assessment of strengthening techniques. The evaluation embeds Life Cycle Assessment (LCA) principles (ISO 2006, ISO 2018) at a conceptual level and is intended to support early-stage decision-making, especially in contexts where detailed quantitative inventory data are not available. The comparison integrates structural performance and cost aspects with qualitative life-cycle considerations, accounting for material production, construction, maintenance, and end-of-life stages. The evaluation is illustrated through a case study on an existing PRC bridge girder (Santarsiero et al. 2024), for which different strengthening solutions are designed to achieve equivalent flexural capacity enhancements. This allows a consistent comparison of the techniques in terms of structural effectiveness and economic implications. The ultimate goal is to provide a transparent and practical decision-support tool capable of highlighting potential trade-offs between safety, efficiency, cost, and long-term sustainability, thereby promoting more informed and resilient retrofit strategies for ageing bridge infrastructure. 2. Strengthening strategies for prestressed reinforced concrete bridge girders A wide range of strengthening strategies is currently available for the rehabilitation of prestressed reinforced concrete (PRC) bridge girders. These techniques differ not only in terms of mechanical behavior and achievable performance improvements, but also with respect to material demand, construction processes, durability, and long term management.