An essential requirement for today’s building is to provide long spans with minimizing the weight of concrete for sustainability objectives. A viable option that has evolved is biaxial voided (BubbleDeck) slabs, which reduce concrete weight while preserving structural efficiency. This study analyses the structural behavior of GFRP-reinforced biaxial voided slabs through experimental and numerical investigations. A concentrated load was exerted on twelve slabs. The testing parameters were reinforcement type, diaphragm reinforcement, voids diameter, and loading procedure. Experimental results indicate that slabs with steel reinforcement exhibit superior stiffness and enhanced ultimate load capacity compared to GFRP slabs. The deformability and energy absorption of GFRP slabs were significantly greater. Experimental results showed that the steel-reinforced control slab achieved an ultimate load of 224.2 kN, whereas the GFRP-reinforced ribbed slab showed a 46.3% lower capacity and approximately 4.4 times greater maximum deflection. Under repeated loading, the specimens exhibited progressive stiffness degradation and crack widening while preserving stable flexural behavior throughout the loading cycles. Furthermore, the diaphragm reinforcement arrangement provided the most efficient load-transfer mechanism and superior structural performance. Meanwhile, the smaller void configuration enhanced energy absorption and deformability, demonstrating the important role of void geometry in slab behavior. To further examine the structural response, a nonlinear finite element simulation model was developed by ABAQUS/CAE. The numerical model showed reasonable agreement with the experimental observations, with deviations ranging from 3.0% to 15.2% for ultimate load and deflection predictions. Moreover, a parametric evaluation was carried out, revealing that higher concrete compressive strength plays a key role in improving the overall structural performance of the slab system. The research indicates that BubbleDeck slabs can be fortified with GFRP, rendering them a more efficient and sustainable substitute for reinforced concrete slabs.
