PSI - Issue 64

A. Cagnoni et al. / Procedia Structural Integrity 64 (2024) 944–950 4 Alessandro Cagnoni, Pierluigi Colombi, Marco A. Pisani, Tommaso D’Antino / Structural Integrity Procedia 00 (2019) 000 – 000

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2.2. Wedge-barrel anchor

The novel anchor system presented in this paper was based on metallic components. A steel barrel was used, whereas wedges made with a peculiar brass-alloy specifically designed to resist to seawater were adopted. Additionally, a connecting ring was used to constrain the free movement between the wedges, thus ensuring the alignment of their top surfaces during the assembling (Fig. 3). The barrel internal surface and wedge external surfaces had a different inclination angle. This specific interface was adopted to reduce and distribute the stress concentration along the composite bar. The barrel was made of steel with an elastic modulus of 210 GPa, while the wedges were made of a specific brass alloy characterized by an elastic modulus of approximately 100 GPa. In fact, the prestressed technology with FRP tendons is adopted in harsh environments and all the components should resist to the degradation phenomenon. Future developments of this system include the use of non-corrosive material also for the barrel.

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Fig. 3 (a) Components of the wedge-barrel anchor and (b) anchor system and CFRP bar before testing.

2.3. Tensile tests Three GFRP bars and three CFRP bars were tested using the novel wedge-barrel anchor. The composite bars had the same characteristics of those reported in section “ 2.1 FRP bars ” except for the total length, which was equal to 1000 mm. To assess the efficiency of the anchor system, the bars were anchored at each end by three brass alloy wedges and inserted within the steel barrel. The barrel was inserted within the hole of a steel plate (with a diameter smaller than that of the barrel) that was connected to the testing machine (Fig. 4). The tests were conducted using a servo-hydraulic testing machine equipped with a load cell of 500 kN. The tensile test was conducted following the prescriptions of ASTM D7205/D7205M-21 (American society for testing and materials (ASTM) (2021)), under displacement control, by monotonically increasing the displacement (stroke  ) of the machine at two different rates: one during the initial settlement of the wedges, and another after the initial settlement phase was concluded. The initial settlement was considered complete when a total force of 10 kN was reached. For the GFRP bars, the two displacement rates were 0.075 mm/s and 0.100 mm/s, while for the CFRP bars, the rates were 0.100 mm/s and 0.150 mm/s.