| Summary: | The growing demand for efficient construction methods has led to the investigation of alternative formwork technologies, such as permanent precast panelling formwork (PPPF), as substitutes for traditional reinforced concrete (RC) formwork. However, the structural performance of such systems, particularly under flexural loads, has not been extensively explored. This gap in knowledge raises concerns about their reliability and limits wider adoption in structural applications. This study investigates the feasibility of employing PPPF in reinforced concrete beams by evaluating their flexural behaviour and comparing performance with that of conventional RC beams. The specific objectives are to evaluate the load-bearing capacity, structural response, failure mechanisms, and bond characteristics of PPPF beams under diverse flexural loading scenarios. The study focuses on simply supported RC beams incorporating PPPF as permanent formwork, compared against conventional RC beams. A total of eight full-scale beams, each with dimensions of 150 mm × 300 mm in cross-section and 3000 mm in length, were fabricated. Four beams were constructed as conventional RC beams serving as control specimens, while the other four incorporated modular precast panels forming the PPPF system. Each PPPF beam was assembled using 600 mm × 300 mm × 25 mm precast panels to form a permanent casing for cast-in-place concrete. The reinforcement detailing complied with Eurocode 2 (EN 1992-1-1:2004), using 12 mm and 16 mm high tensile steel bars for tension, 12 mm bars for compression, and 8 mm stirrups at 150 mm spacing for shear resistance. The flexural behaviour was evaluated through three-point and four-point bending tests in accordance with clause 6.2 of Eurocode 2, while push-out tests were conducted to assess bond strength as per clause 8.4. The results showed that conventional RC beams exhibited greater moment resistance, while PPPF beams demonstrated a 15.2% to 27.3% reduction in flexural strength, primarily attributed to diminished concrete confinement. Nonetheless, increasing the reinforcement size in PPPF beams improved flexural capacity by up to 35.2%, demonstrating the system's adaptability. Push-out tests revealed minor discrepancies between theoretical and experimental bond strength values, highlighting the need for empirical validation. The observed failure modes were predominantly brittle; however, specific PPPF configurations exhibited improved ductility. The study demonstrates that modular PPPF systems have potential structural applications and offer benefits such as ease of installation and material optimisation. These findings provide valuable insights into the structural performance of PPPF beams and support the development of standardised design frameworks to promote the adoption of precast technologies in reinforced concrete construction.
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