PSI - Issue 84

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

971

Traffic intensity, aggressive environmental conditions, climatic factors, excessive loads, occasional impacts, and above all the inadequacy of the drainage system for meteorological water, are all factors that contribute to the deterioration of materials and structural elements. Deterioration may also occur suddenly, may appear on different elements, and may develop at an increasing rate over time. For these reasons, the planning of an appropriate frequency of inspection checks is of fundamental importance. The issue of surveillance through regular and scheduled bridge inspections has been addressed in numerous Italian and international standards; however, only in the last decade has the awareness of infrastructure managers increased to such an extent as to allow, over a large part of the national territory, an effective application of those legislative principles. The accurate execution of visual inspections lays solid foundations for an efficient and intelligent automated management system, which, it should be recalled, is a technically and economically demanding operation. All data collected during the first two phases are subsequently used in the third phase, namely the risk assessment phase. In this phase, specific indices are defined in order to determine not only the level of deterioration of each structural element and of each bridge structure, but also to evaluate the reliability of the collected information and the parameters influencing the functionality of the structure and the associated risk, considering the bridge structure as part of a wider system. The risk assessment phase is, in turn, subdivided into three levels: Level 1 Local damage assessment Level 2 Local structural assessment Level 3 Territorial assessment Level 1 Local damage assessment Within the local damage assessment, four indices are defined: Element Damage Index, Element Reliability Index, Maximum Damage Index, Global Damage Index Each bridge or viaduct is subdivided into j structural elements. For each j-th element, a value referred to as the element weight is assigned. This weight assumes a unit value for girders, deck slabs, cross-beams, piers, abutments, arches, and arch piers, while it is equal to 0.30 for expansion joints. This choice is motivated by the lower structural relevance of expansion joints compared to the other elements. By compiling the Inspection Form of the individual structural element j, two key indices can be determined: the Element Damage Index (EDI J ) and the Element Reliability Index (ERI J ). The Element Damage Index expresses, on a normalized scale, the damage condition of the structural element by accounting for the gravity and severity of the observed defects and the relevance of the element itself. The Element Reliability Index represents the reliability of the damage evaluation for the element and depends on both the observable portion of the element and the number of defects that could actually be assessed with respect to those that are theoretically applicable. They are defined as: =100 ∙ ∙∑ ∙ = 1 ∑ = 1 [0~100] (1) = % ∙ ( , ) [% ] (2) Where: j = j-th structural element; i = i-th defect; n ril = number of defects that could be assessed; n tot,es = total number of defects that are applicable to the element; W j = element weight; G i = damage gravity (1;2;3;4;5) S i = damage severity (0;0.25;0.50;0.75;1.00) 3.3. Phase 3: Risk assessment