PSI - Issue 84

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

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FRP-based solutions are characterized by low added weight and limited material quantities, which are beneficial from a structural efficiency and construction standpoint. Installation is generally moderately invasive, which results in medium-high construction efficiency. However, the production of fibers and polymeric matrices is energy intensive, and durability may be affected by environmental exposure and bond-related failure mechanisms. Recyclability is limited, and disposal options at end-of-life are often unfavorable. Overall, FRP strengthening offers advantages in terms of construction efficiency but presents relevant challenges in terms of qualitative life-cycle performance, particularly related to material production and end-of-life management. External post-tensioning combines a low material demand with high structural effectiveness, resulting in favorable resource efficiency. The construction phase is generally less invasive, with reduced impact on traffic and shorter execution times. From a durability standpoint, the possibility of inspection, re-tensioning, and replacement of tendons enhances adaptability and facilitates long-term management. The technique is largely reversible, and steel components are recyclable, making end-of-life scenarios relatively favorable. Overall, external post-tensioning emerges as the most advantageous solution in terms of qualitative life-cycle performance. Based on the qualitative assessment, Table 1 summarizes the relative performance of the analyzed strengthening techniques across the considered life-cycle criteria.

Table 1. Qualitative life-cycle comparison of strengthening strategies. Criterion

Steel jacketing RC jacketing FRP strengthening External post-tensioning

Material efficiency (A1–A3) Construction efficiency(A4–A5) Durability of the intervention (B) Ease of maintenance (B) Adaptability/reversibility End-of-life management (C)

med-low

low low med med low low

med

high

med med med

med-high

med-high med-high med-high

med med

med-low

med-low

high

med med

low

med-high med-high

Overall qualitative life-cycle performance

med-low med

4. Performance and cost comparative analysis To enable a consistent quantitative comparison of the mentioned strengthening strategies, equivalent retrofit configurations were designed for a prestressed reinforced concrete girder extracted from a case-study bridge built in the 1960s. The interventions were conceived to achieve comparable target increases in flexural capacity (iso performance), thus ensuring consistency among the different techniques. The reference bridge, including its geometry, material properties, and reinforcement layout, is described in detail in a previous work (Santarsiero et al. 2024). The flexural capacity of the girder in its as-built condition was assessed through analytical procedures validated by nonlinear finite element analyses. Starting from this reference capacity, each strengthening solution was designed to provide a predefined increase in bending resistance, within a limited tolerance range ( ΔM = 25% ± 3%) (Santarsiero et al. 2023). For each technique, the design process focused on identifying the key parameters governing the flexural response, such as plate thickness and steel grade for steel jacketing, jacket geometry and reinforcement layout for reinforced concrete jacketing, tendon layout and prestressing force for external post-tensioning, and laminate geometry and mechanical properties for FRP-based systems, while limiting the additional permanent load introduced by the intervention. The detailed analytical formulations, modelling assumptions, and step-by-step design procedures are not reported here for the sake of conciseness and can be found in the referenced studies (Picciano et al. 2025). In the case of FRP strengthening, the design was governed by bond-related failure mechanisms, which typically control the ultimate capacity of externally bonded composite systems. Despite exploring a wide range of commercially available materials and configurations, the achievable flexural capacity increase remained significantly lower than the target value adopted for the other techniques. This limitation is mainly associated with the risk of premature