PSI - Issue 62

Stefano Grimaz et al. / Procedia Structural Integrity 62 (2024) 161–168 S. Grimaz et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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for risk assessments. Moreover, the methodology is intended for inspections on a wide range of bridge typologies, also covering the bridges from 0 to 6 meters, which are not addressed by the Italian Bridge Guidelines, but can be critical for local road networks. In the VISIT-bridges methodology, the semeiotic parameters are named as “districts” , because they represent different components of the structure and specific aspects of the context, distinguished on the bases of their physical location or their functional characteristics. In particular, the bridge districts identified in the VISIT methodology are the following: Core districts: • Elevation/support structures: to focus on structural elements with vertical framing. • Horizontal load-bearing structures: to focus on structural elements with horizontal framing. • Foundation structures: to focus on structural elements that distribute the loads received from the superstructure to the ground. Completion districts: • Appurtenances: to focus on non-structural or structurally connected elements (including those associated with the installation of facilities, road furniture, etc.) and on the elements that constitute the road pavement. • Structural seismic vulnerability: to focus on elements or portions of the structure that could lead to vulnerabilities in terms of seismic resistance. • Site seismic criticalities: to focus on site-specific characteristics that could lead to critical situations in the event of seismic events. • Hydraulic criticalities: to focus on site-specific characteristics that could lead to critical situations in the event of water-related events. • Geological criticalities: to focus on site-specific characteristics that could lead to critical situations in the event of geological instabilities. The core districts are identified as “principal s ” , given that they are essential for the maintenance of the structure's integrity and, consequently, for its operational conditions. Therefore, the core districts are functionally indispensable for maintaining the stability and functionality of the structure. Completion districts, on the other hand, represent secondary or functional districts that could anyway reveal situations that may pose potential risk conditions in relation to the interaction with the structure and the maintenance of its operability. For each district VISIT methodology pre-identified the "Significant Observational Elements" (referred to as EOS), to support the identification and categorization of safety issues (namely, safety-deficits) during an inspection. The safety-deficit related to each EOS is evaluated based on how much it deviates from a pre-defined reference situation (using the "deep-delta" method, see Grimaz et al., 2023). Subsequently, it is categorized depending on its impact on user safety or as an indirect sign of management-related problems. The pre-codified approach at the basis of the VISIT methodology ensures consistency in judgments among different inspectors and provides coherent metrics for comparing various inspections and assets. The level of deviation also serves as a warning for informing management entities about the identified safety-deficits. Moreover, VISIT algorithms assign a warning color code to each district based on the encountered deficiencies. A specific “ characterization chart ” that summarizes in a unique graphical indicator all the warnings of each investigated district is then produced. In the VISIT-bridges methodology, EOS are associated with a “ constitutive element” (EC) - a part or portion of the structural system with a specific function. EC are categorized as follows: • Critical EC – Allows control or elimination of specific critical conditions (e.g., unsupported thrusts), or is part of a primary EC performing a specialized balancing/connection/linkage function. For bridges, critical ECs may include supports, anchorages, saddles, stabilizers, etc. • Primary EC – Responsible for transferring forces to the ground. For bridges, common examples are pillars and main beams.