Structural, environmental and economic assessment of GFRP and hybrid GFRP–FRC solutions for retrofitting an existing motorway tunnel lining: a case study

Existing motorway tunnels increasingly require major rehabilitation interventions to restore structural performance while limiting environmental and economic burdens. This study investigates the complete renewal of the lining of the Olimpia motorway tunnel in Italy and compares three structurally feasible reinforcement strategies: conventional steel reinforcement, GFRP bars, and a hybrid GFRP–FRC solution. The alternatives were designed under the same project-specific loading conditions and verified at both Ultimate and Serviceability Limit States. Their environmental and economic performance was subsequently assessed through a cradle-to-gate Life Cycle Assessment (LCA) and an intervention-based partial Life Cycle Costing (LCC) covering the complete rehabilitation process. Relative to the conventional solution, the GFRP alternative reduces GWP-total by 5.1 % and direct rehabilitation cost by 14.1 %, whereas the hybrid GFRP–FRC solution achieves the largest GWP reduction (8.7 %) while reducing cost by 10.7 %. The two innovative solutions therefore outperform conventional reinforcement in the GWP–cost plane, although a trade-off remains between minimum cost and minimum climate-change impact. A phase-based analysis also identifies demolition as a major contributor to both environmental impact and cost. Finally, a material-supply scenario analysis shows that the GWP benefits depend strongly on cement type and steel-production route, becoming more pronounced for the proposed GFRP-based solutions when conventional reinforcement is produced through the BF–BOF route rather than recycled EAF steel. The results demonstrate the value of integrating structural design, LCA and cost assessment when comparing tunnel rehabilitation alternatives, while highlighting the need for project-specific inventories and future whole-life durability modelling.