The aim of this work is assessment and analysis of the reliability of the most well-known design models, available for the prediction of the contribution of fiber reinforced polymer (FRP) systems to the shear capacity of strengthened reinforced concrete beams. In this study, current analytical formulations for basic shear design and shear strengthening design are presented in detail and main problems and lacks, being the motivation of this work, are highlighted. The research is based on the comparison of previous experimental studies with both current design guidelines and design models recently proposed by several authors, considering also various recommendations for the angle of inclination of shear cracks. Assessment of design procedures was done using probabilistic aproach, and several descriptive statistical measures, such as the average (AVG) and the coefficient of variation (CoV), have been obtained from database, regarding different strengthening schemes. A more detailed analysis of reduced database was made, considering only Ujacketed configurations with transversal steel. Because of its good performance, a detailed investigation on Pellegrino and Modena (2008) model has been made and in order to predict better results, modification of this model has been proposed.