PSI - Issue 84

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

161

• Degradation SLO – Deterioration model applied to SLO performance right after treatment completion. Parameters are time-dependent, they are assigned to each 20 m long segment at the time of treatment, and they change when a new treatment is performed on the same asset. 2. Structural performance 2.1. Deterioration models The tool enables detailed analysis of individual assets and a high-level approach to portfolios. In both cases everything starts with SGG and SLO performance predictions, done using dedicated deterioration models. Nowadays, however, the analytical model “No intervention/IMS” illustrated in Fig. 1 is used for all tunnels prior to the implementation of interventions, as the process of defining dedicated models for “clusters” through the collection of inspection data via the ARGO Gallerie platform is still ongoing.

Fig. 1. Degradation models for tunnels without intervention (black) and after IRS intervention (blue) or TRS intervention (purple)

2.2. Current conditions

The current condition of the asset is defined in relation to two types of possible collapse mechanisms as the level of defect associated with them: LdD SGG – Overall Structural and Geotechnical Defect Level – a parameter that is included in the Vulnerability Class of the relevant preliminary risk assessment. LdD SLO – Local Structural Defect Level – State of cracking and construction defects + under thickness of the lining, a parameter that is included in the Vulnerability Class of the relevant preliminary risk assessment. For each segment, both Defect Levels are assessed based on the extent, intensity and severity of any defects and under-thicknesses that may be present. By dividing the theoretical condition of an asset into 5 equal bandwidths, it is possible to associate an LdD to each of these and identify a minimum level of service for operating conditions. The initial % condition of the asset is equal to: • Between 80% and 100% if the relative LdD is LOW (1), 90% is assumed for simplicity. • Between 60% and 80% if the relative LdD is MEDIUM-LOW (2), 70% is assumed for simplicity. • Between 40% and 60% if the relative LdD is MEDIUM-HIGH (3), 50% is assumed for simplicity. • Between 20% and 40% if the relative LdD is HIGH (4), 30% is assumed for simplicity.