Behavior of GFRP Reinforced-Concrete Bubbled One-Way Slabs by Encased Composite Steel I-Sections

Bubbled Reinforced Concrete (RC) slabs have gained popularity in recent years as a practical construction method that eliminates unnecessary concrete in the center, thereby reducing the dead weight of the structure. This study provides a systematic framework to compare the performance and capabilities of one-way bubbled concrete slabs reinforced with Glass Fiber Reinforced Polymer (GFRP) bars and embedded steel I-sections. Four one-way concrete slabs, each with a length of 2,600 mm and a rectangular cross-sectional area of 600 mm in width and 150 mm in depth were employed. These slabs were reinforced with Glass Reinforced Plastics (GRP) rebar at the same reinforcement ratio and tested by two-point bending to failure. Different parameters such as specimen type (solid or bubbled slabs) and internal reinforcement were achieved using steel I-sections in two different shapes (2 and 4 pcs of steel I-sections), where 4I-section shape with a cross-sectional area equivalent to 2I-section shape, channel shear connectors, and bent steel bars (10 mm diameter) were used to improve the shear resistance. The results showed that bubbled slabs experienced a higher range of deformations (including deflection, strains, and cracks) by about (28%-88%) and a 15% decrease in ultimate load capacity compared to solid slabs. On the other hand, the use of steel I-sections as internal reinforcement significantly improved the specimen performance compared to unreinforced slabs (Steel Slab (SS) and Bubbled Slab (BS), respectively). Deflection was reduced by approximately 52% and 87% at the same load level, ultimate load capacity increased by approximately 121% and 179%, and flexural stiffness increased by approximately 197% and 272% at the same load level.