Assessment of the Existing Formulations to Evaluate Shear-Punching Strength in RC Slabs with FRP Bars Without Transverse Reinforcement

Nowadays, the real application of fibre reinforced polymer (FRP) bars in slabs or in bridge decks submitted to environments susceptible of corrosion is very limited. In spite of its cost, one of the reasons might be the limited knowledge about the punching-shear behaviour of this type of elements in their connection slab-column or under point loads. The punching-shear strength of slabs reinforced with FRP bars without transverse reinforcement is a complex phenomenon. The main difference with the conventional reinforced concrete is that the passive reinforcement has a linear elastic behaviour up to failure. There is a limited number of experimental and analytical studies about this subject. According to the existing experimental programs, it seems that the basic perimeter at failure is lower in an FRP reinforced concrete (RC) slab than in a conventional RC slab, strains are higher due to the lower modulus of elasticity of the FRP bars, and the cracks are wider. In this paper, a comparative analysis of the reliability of the existing formulations to evaluate the punching strength of FRP RC slabs without transverse reinforcement is performed. A database of 92 tests compiled from 21 experimental programs has been assembled. Most of the existing formulations to predict punching of FRP RC slabs without transverse reinforcement are an adaption of the existing formulations for conventional RC slabs, which take into account the lower stiffness of the FRP bars. Based on the unified model for shear and punching developed by Mari et al. (2015), a preliminary proposal has been made and its reliability has also been evaluated by means of the assembled database.