PSI - Issue 84

Ivan Beltracchi et al. / Procedia Structural Integrity 84 (2026) 1015–1022

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2. Structural health monitoring (SHM) system A prestressed reinforced concrete (PRC) bridge built during the 1970, was selected as a case study for structural analyses and monitoring activities. It is located in the San Polo district, in the Southeast area of Brescia at km 12+280 of the road SPBS11, better known as the Southern Brescia Expressway. The structure is characterized by a single, statically determinate, short-span, with a length of 25,80 meters and at an elevation of 5,45 meters from the underlying road surface. It consists of 13 reinforced PRC beams and a reinforced concrete (RC) deck 18 cm thick. The upper roadway system includes 4 vehicular lanes (2 lanes per direction) and is divided by a central concrete safety barrier. The deck is highly skewed, at approximately 45° with reference to the underlying road, and is supported by two RC abutments 1m thick.

(a) (c) Fig. 1 (a) Viewpoint of the infrastructure selected as a case study, (b) location of the bridge along the expressway and (c) aerial view Detailed on-site inspections showed that the PRC beams, forming the bridge’s main load-bearing system, have an I-shaped cross-section with a total depth of 120 cm. Each beam consists of upper and lower flanges 60 cm wide and 13cm thick, connected by a 12 cm thick web. The beams are spaced at a constant distance of approximately 1.30 m and are laterally connected by three transverse beams. The deck is simply supported on the two abutments. The three transverse stiffening beams, made with cast-in-place reinforced concrete, have a rectangular cross-section of 25×105cm and are located at midspan and at the two end supports. These elements play a key role in distributing transverse loads across primary beams. The superstructure has an overall thickness of 18 cm and consists of cast-in place reinforced concrete slab. An investigation carried out on the road pavement found that it comprises a 20 cm layer of asphalt concrete topped by an approximately 5 cm bituminous wearing course. (b)

(a) (b) Fig. 2 (a) Cross-section geometry of PRC girders and (b) parabolic profile of post-tensioning tendons.

Construction details survey was made using a ground-penetrating radar (GPR) device, together with selective removal of the concrete cover, with aim of providing key information on the layout of steel reinforcement and prestressing cables. These investigations identified straight prestressing tendons as well as post-tensioning tendons with a parabolic profile, along with longitudinal reinforcement and shear reinforcement (stirrups) that is densified near the supports. The average mechanical strength of the aged concrete was also evaluated at multiple locations in accordance with UNI EN 12504-2/4, using a rebound hammer test combined with ultrasonic measurements; the results allowed the concrete to be classified as C50/60.