Behavior of Hollow Core Slabs Reinforced with GFRP Prestressing Bars

An experimental program was designed to study the behavior of full-scale hollow core slabs prestressed with Glass Fiber-Reinforced Polymer (GFRP) bars in the concrete laboratory at the college of engineering, Mataria, Helwan University, Cairo, Egypt. The hollow core slabs were load-tested under uniformly distributed load. The GFRP bars were manufactured from locally available materials with a 10 mm nominal diameter. To improve the bond properties between the bars and concrete, GFRP threads were axially wrapped around the bars manually. The mechanical properties of the bars were investigated in the laboratory. The bars average ultimate tensile strength (fu) and elastic modulus (E) were 1000 MPa and 46 GPa, respectively. Four full-scale concrete hollow core slab specimens with characteristic strength of 80 MPa were constructed and solely reinforced with a single prestressed GFRP bar. Each slab specimen represented one complete vent with a width of 140 mm, 150 mm thickness and 4000 mm total length. These specimens were simply supported during the experiments where the GFRP bar was placed at the centerline of the vent near the soffit. The Bars were prestressed to different stress levels, namely (10, 20, 30 and 40%) of their ultimate tensile strength (fu). All slab specimens were load-tested under uniformly distributed load. The deflection, strain and crack pattern were investigated during load-testing. From the obtained results, it was observed that the optimum prestressing level was 20% of the ultimate tensile strength of the bar for both the moment carrying capacity and the deformation.