Reinforced concrete structures such as slabs-on-ground develop cracks due to drying shrinkage and thermal loading before concentrated vehicle loads are applied to them. These cracks are conduits for ingress of chloride, leading to corrosion of the steel and damage to the slabs. Grade supported slabs reinforced with non-corroding GFRP bars are an attractive alternative that could provide a maintenance free service life of over 100 years. The punching shear capacity of GFRP bars reinforced slabs-onground, which are primarily designed to control shrinkage and crack width, has not been investigated in the literature. This paper presents the results of numerical parametric studies conducted to investigate the performance of grade supported slabs reinforced with GFRP bars. The numerical model developed in the study was calibrated using data obtained from punching shear failure tests performed on the slabs by the authors. After validation of the numerical model, parametric studies were performed to investigate the effects of variables such as concrete strength, reinforcement ratio, and rebar grid location in the slab. Guidelines for the design of GFRP bar reinforcement for slabs-on-grade are provided.