PSI - Issue 84

D. Di Fiore et al. / Procedia Structural Integrity 84 (2026) 159–166

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Keywords: Tunnel Asset Management, Decision Support Tool, Infrastructure Lifecycle, Deterioration Modelling, Maintenance Prioritization, Risk-Based Maintenance

1. Introduction and regulatory framework The refurbishment of aging motorway tunnels requires a strategic approach that moves beyond simple maintenance towards long-term asset management. This paper illustrates a methodology developed and deployed as a decision support tool for comparing alternative treatment scenarios This is a mandatory step in modern infrastructure management approaches, preceding the actual design of the refurbishment intervention. The primary objective is to identify the solution that offers the best cost-benefit ratio by balancing technical requirements with financial, operational and environmental sustainability. The framework is aligned with recent national guidelines for risk classification and safety assessment of existing tunnels, making the approach scalable and deployable by any Organization operating in the existing tunnel management industry.

Nomenclature δ

Discount factor

i Discount rate LLGG National guidelines for risk classification, safety assessment and monitoring of existing tunnels

1.1. The TR&NDS methodology The core of the decision-making process is the TR&NDS (Tunnel Refurbishment and New Decision-making Strategies) tool. The tool evaluates intervention strategies applied to standard 20-meter long tunnel segments based on multi-criteria parameters: • Financial Metrics : Capital Expenditure (CapEx) and Operational Expenditure (OpEx), including visual inspection costs, maintenance costs etc.. • Structural Performance : Immediate upgrade and subsequent degradation models for both Global Structural/Geotechnical (SGG) and Local Structural (SLO) performances. • ESG Factors : Environmental impact via Carbon Footprint and social impact through traffic disruption and work durations. Rarely will one strategy outperform the others on all three factors, it will be up to the decision-maker to choose which aspects to prioritise in line with the Organization’s business objectives. TR&NDS is a web application developed in collaboration with academic (Politecnico di Torino) and engineering partners (Jacobs U.K.) which allows the comparison of alternative refurbishment solutions including the “To do nothing” approach. The tool allows Engineers to create and assign typological treatments to standardised 20 m long tunnel segments. Each intervention is characterized by the following parameters: • CapEx – Capital expenditure related to the workload involved in the construction of the typological intervention. • OpEx – Operative expenditure related to the maintenance of the intervention itself and to the frequency of visual inspections of the tunnel, which depends on its structural condition (in accordance with the LLGG framework). • SGG upgrade – Increase in the overall structural and geotechnical performance of the asset upon completion of the intervention. • SLO upgrade – Increase in the structural local performance of the asset upon completion of the intervention. • Degradation SGG – Deterioration model applied to SGG performance right after treatment completion, can change future behaviour of the asset when high performance materials or waterproofing techniques are used.