PSI - Issue 84

Rosario Montuori et al. / Procedia Structural Integrity 84 (2026) 967–974

973

The traffic intensity coefficient K t is determined based on traffic data provided by the Road Authority, with particular reference to Average Daily Traffic (ADT), and Public Transport Traffic (PTT), defined as the annual number of public transport vehicle crossings. Traffic levels are classified into ranges according to ADT and PTT, which are then combined to determine the traffic intensity coefficient through a reference matrix which is reported in Table 1.

Table 1. Determination of the Traffic Intensity Coefficient K t

Public Transport Traffic (Number per year)

0

1-1000

1001-3000

3001-10000

>10000

0-1500

0.00 0.10 0.20 0.30

0.10 0.20 0.30 0.30

0.20 0.20 0.30 0.30

0.30 0.30 0.40 0.40

0.30 0.30 0.40 0.40

Average Daily Traffic

1501-4000 4001-8000

>8000

The alternative route coefficient K pa is based on the difference between the actual travel time between two significant points located upstream and downstream of the bridge structure T t , and the alternative travel time T at between the same points when the bridge structure is not used. Travel times can be determined using digital navigation tools such as Google Maps. The coefficient increases with the additional travel time required when the bridge is not available, reflecting the increasing impact of service disruption. It is defined as: = { − < − − ≥ , − ≥ [ ~ . ] (9) The indirect damage coefficient K ind accounts for the potential consequences of partial or total collapse of the bridge structure, with reference to the obstacle being crossed. This coefficient assumes a value equal to 1 for bridges crossing urban areas, heavily trafficked roads, and railways; equal to 0.97 for bridges crossing lightly trafficked roads; and equal to 0.95 in other cases, such as bridges over valleys, riverbeds, or non-urbanized areas. 3.4. Phase 4: Classification The coefficients and indices obtained during the evaluation phase are combined to determine the overall classification parameter of the entire bridge structure, referred to as the Intervention Priority Index (IPI). This index represents the key parameter of the fourth and final phase of the methodology and it is evaluated as: = ∙ ∙ ∙ ∙ ∙ [ ~ ] (10) The final outcome of the application of the proposed methodology therefore consists in the assignment of a numerical value, namely the intervention priority index, which automatically identifies the bridge structures that should be addressed first through rehabilitation or repair interventions. It is important to emphasize that no information related to hydraulic risk or landslide risk is taken into account. This choice was driven by the need of the Road Authority to urgently assess those bridge structures that were most severely damaged and therefore required immediate intervention. On the other hand, this situation still reflects the current condition of most Italian provinces, which, with extremely limited resources, are required to manage a vast infrastructure asset that, since its construction, has often never been inspected and therefore never properly maintained. Consequently, the proposed methodology can be regarded as a practical response to the needs of administrations that, due to the magnitude of the problem to be addressed and the limited availability of economic and human resources, cannot realistically apply the 2020 Guidelines in a strict and comprehensive manner.