PSI - Issue 64

Maciej Kulpa et al. / Procedia Structural Integrity 64 (2024) 1673–1680 Kulpa / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction The use of FRP (fibre reinforced polymer) composite bridge structures has been steadily growing in Poland since 2016, when the country's first bridge made of FRP composites was constructed (Siwowski et al., 2017). The excellent mechanical properties and high durability of this new construction material are the primary reasons for this. The most common applications for FRP composite structures are in the building of new footbridges for pedestrians and bicyclists, as well as in the widening and redecking of already existing road bridges (e.g. Bakis et al., 2002; Manalo, 2017; Siwowski et. al, 2020). The following benefits of FRP composite structures are significant in each of these scenarios: complete prefabrication, low weight (lightness), and easy handling on site. The vacuum-assisted resin transfer moulding (VARTM) process is currently the most popular of the various methods available to produce FRP composite structures in the form of sandwich panels. One of the main bridges in Rzeszów, the capital of the Podkarpackie Voivodeship in south-east Poland, is the Carpathian Bridge built in the early 1970s as an element of the dam on the Wisok River (Fig. 1a). After 50 years of service, the bridge was needed to widen to create a separate two-way bicycle path. The typical widening of the bridge superstructure was impossible because of its full integration with the dam structure. Therefore, it was decided to build an independent structure of the footbridge right next to it, but with the use of supports of existing bridge (Fig. 1b). It was necessary to find a suitable footbridge structure with the lowest possible dead weight. In this case, a FRP composite structure is always the perfect solution. The spans of the new footbridge were designed as five simply supported spans: 4.17 + 23.55 + 23.67 + 23.67 + 23.47 meters, adapted to the length of the existing spans of the road bridge. With a total length of 104.95 meters, the superstructure is believed to be the longest FRP composite footbridge in Poland. Since the footbridge spans are made of an innovative but not fully recognised / proved construction material and due to the size of the bridge and its importance in the city's network of bicycle paths, the decision was made to equip the structure with a reliable structural health monitoring (SHM) system.

Fig. 1. The Carpathian Bridge in Rzeszów (on the left) and the cross -section of new footbridge next to existing bridge (on the right)

2. FRP footbridge description 2.1. Design of the FRP structure

The footbridge was designed as a series of FRP sandwich panels, based on Dutch InfraCore® Inside technology (De Corte et al., 2017). Each panel is made up of upper and lower outer laminates and vertical ribs that stiffen the foam core. Polyester resin and E-glass fibre textiles are used to create laminates, and the PUR foam core with a density of 38 kg/m 3 filled the main body of the panel. The cross-section of the slab structure and ribs arrangement is presented in Fig. 2.