PSI - Issue 64

Bartosz Piątek et al. / Procedia Structural Integrity 64 (2024) 1581–1588 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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2.1. Beam Characteristics The QPT beams had a rectangular cross-section with dimensions of 200 x 300 mm and a length of 1.4 m. The lower reinforcement of the beams consisted of two bars of φ16 mm, while the upper reinforcement comprised two bars of φ12 mm (B500SP steel grade). S tirrups made of φ8 mm bars were used at a spacing of 100 mm. In the QPT beams, cable ducts were embedded with a single prestressing strand of φ15.7 mm made of Y1860S7 steel inside the ducts. The PT beams had a trapezoidal cross-section with a height of 600 mm and a width ranging from 450 to 550 mm. The beams had the plain reinforcement made of B500SP steel grade in the form of ϕ 16 mm rebars at the bottom and top edges, as well as circumferential reinforcement with ϕ 10 mm rebars. Shear reinforcement was also applied using double stirrups with a diameter of ϕ 12 mm. Each PT beam was equipped with 2 tendons with 4 prestressing strands placed in each tendon. After casting the beams, the tendons were prestressed with an initial force of 1500 kN. The cross-sections and longitudinal sections of the QPT1 and PT1 beams are presented in Fig. 1.

Fig. 1. Cross-sections and longitudinal sections of the QPT1 and PT1 beams.

2.2. Simulation of damages Damage in the QPT2 beam, in the form of a void in the cable duct, was simulated by placing polyurethane foam approximately 20 cm long inside the duct close to the beam’s midspan. On the other hand, in the PT2 beam, after tensioning of the tendons, the ducts were not fully filled with grout. Approximately 1.4 m of free space from the ends of the beam was left in the ducts. This resulted in the creation of 4 unfilled duct segments, one of which remained empty (representing a real void in the duct), while in the others, simulations of corrosion (representing a real void and corroded prestressing tendons) and partial filling with polyurethane foam were performed. Accelerated corrosion of the tendons was achieved by filling the channels with a 5% NaCl solution and connecting the tendon through a cathode to an electric current of constant intensity of 990 mA for a period of 80 h (which should result in a weight loss of approximately 5%). This method was described in detail by Abouhussien & Hassan, (2014). The schematic view of the simulated damages in the beams QPT2 and PT2 is shown in Fig. 2.

Fig. 2. Damages simulated in the QPT2 and PT2 beams.