PSI - Issue 84

I. Vangelisti et al. / Procedia Structural Integrity 84 (2026) 1247–1254

1253

5. Extension of the nominal service life of temporary interventions The nominal service life of interventions may be extended: • upon completion of the VAL4 process; • following specific verifications carried out outside the scope of the VAL4 framework, when they are placed in a inspection segment on which the VAL4 is not carried out. 5.1. Extension following the VAL4 and verification of the actual degradation state The extended nominal service life of the intervention is defined based on the outcomes of the verifications and verification introduced in the previous sections. For interventions for which the robustness verification is not performed, the extension of the extended nominal service life is determined only on the basis of the results of the load load-bearing capacity verification not fullfilled: the robustness verification is consequently considered not fullfilled for the same scenarios. The nominal service life of the intervention cannot be extended; in this case, appropriate compensatory measures shall be implemented; • load-bearing capacity verification fullfilled up to an extended life of a maximum of ten year, defined on the basis of the outcomes of the robustness verification. Following an extension of the nominal service life of the intervention, a verification of the actual degradation state of the intervention shall be carried out within the fifth year from the execution of the initial verification. The objectives of this verification are: • to assess whether the initial assumptions regarding the rate and kind of degradation progression are fullfilled, acknowledging that scenarios may be more or less conservative than initially assumed; • to verify any evolution of the controlled defect in terms of type, extent, and severity; • to confirm the consistency between the controlled defect and the implemented intervention taking into account any evolutions identified in the previous steps. The minimum activities required to perform this verification shall include: • visual activities: inspection of the interventions and the surrounding lining, with visual assessment of their degradation, including verification of changes in defect severity and extent; • testing activities: measurement of the residual thickness of metallic elements; removal of at least 20% of the steel plates, with pull-out tests performed on at least 2% of the anchors, both exposed and behind the plates; • comparison between the initial verification assumptions and the actual degradation state, with identification of any compensatory measures and possible revision of the extended nominal service life. 5.2. Extension following specific verifications carried out outside the scope of the VAL4 framework For interventions installed on lining inspection segments that are not subject to VAL4, the nominal service life may be extended by a time interval equal to the difference between a maximum of ten years and the current in-service life, calculated from the date of installation of the intervention. To ensure the extension, the fulfilment of a dedicated verification is required, accounting for: • baseline assumptions of the typological design; • survey of the current degradation state of the intervention and of the controlled defect, carried out through visual inspection; • execution of pull-out tests on 2% of the anchors of the intervention. The objective of the procedure is to collect evidence in order to characterise of the actual degradation progression observed in the intervention, which shall be compared with the initial design assumptions. If the actual degradation progression is found to be less severe than that assumed at the design stage, the nominal service life may be considered extended. Conversely, compensatory measures shall be envisaged, such as replacement of deteriorated intervention elements, installation of lightweight protective systems, and similar actions. bearing capacity and durability verification. In particular, the following cases may occur: •