PSI - Issue 64

Mariniello Giulio et al. / Procedia Structural Integrity 64 (2024) 2101–2108 G. Mariniello, D. Coluccino, A. Bilotta, D. Asprone / Structural Integrity Procedia 00 (2019) 000 – 000

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structural parameters of bridges [Romanello et al. (2024)]. Although visual inspection has traditionally been used to detect surface defects and assess the structural health status, this methodology is subjective, time-consuming, and limited in detecting real-time changes. Thanks to advances in monitoring technologies, Structural Health Monitoring (SHM) has emerged as a promising solution [Mishra et al. (2022)]. Currently, monitoring the health status of bridge structures is primarily evaluated by measuring certain physical quantities of the bridges, such as velocity, displacement, and deformation [Zhang et al. (2019)]. Deformation monitoring provides a powerful diagnostic tool for monitoring the structural health of bridges. Excessive deflections under service loads can be indicative of structural changes, damage, and deterioration, [Huang et al. (2024), Helmi et al. (2015)]. For real-time monitoring of deflections under operational traffic loads, it is often difficult to establish a fixed reference point for displacement transducers because the bridge may span over water or a roadway. Linear Variable Differential Transformers (LVDT) has a very high deflection measurement accuracy of about 0.01 mm. However, the system requires additional supports on the bridge deck to support such sensors, while most bridge decks are not suitable for building such support systems, especially for long-term monitoring, due to factors related to rivers and traffic [Deng et al. (2022)]. Geodetic techniques, such as total stations and static levelling, are widely used in deflection measurement due to their high precision (up to 0.1 mm) and stability. However, they cannot be used to monitor dynamic deflection under traffic loads because their system operation is lengthy and laborious. The use of Global Positioning System (GPS) is also arising in structural monitoring application [Lee et al. (2022), You et al. (2023)]. Despite Structural Health Monitoring being a highly debated topic, difficulties still exist in determining dynamic deflection under traffic loads [Tang et al. (2023)]. This article proposes the use of laser sensors for measuring the deflection of a bridge beam. After verifying that laser sensors can detect even small deformations of the bridge, different sensor arrangements on the Volto Santo bridge are studied to enable wide application. 2. Description of the monitored structure The Volto Santo Bridge spans kilometer 17+586 on the East-West bypass road in Naples, located within the city's municipality. The bridge's total length is about 73 meters, and it is 12.95 meters wide. It features four simply supported spans with respective clear spans of 16.32 meters, 17.10 meters, 17.00 meters, and 16.20 meters. Each span comprises nine longitudinal girders, each 120 cm high, and 46 cm wide reinforced concrete beams with bonded tendons. These beams are spaced 1.40 meters apart, as detailed in the bridge's transversal section shown in Figure 2. These beams are connected by a top slab with a thickness of 25 cm and by 5 stiffening transverse beams, including 2 at the abutment. The vertical structures of the bridge consist of 3 piers and 2 abutments. The piers are identical to each other, and each one consists of 3 circular pillars with a diameter of 120 cm, placed in alignment with three foundation piles of the same diameter. On the other hand, the abutments consist of reinforced concrete walls that also rest on 120 cm diameter piles.

Fig. 1 View from above of the Volto Santo bridge.