Structure, during their service life, may be subjected to different loading rates. This phenomenon can influence the overall behaviour of the structure as constituent materials are strain rate sensitive. In the previous studies, the behaviour of flexure critical beams being subjected to various loading rates (Static: 0.4 mm/s, Low: 40 mm/s, Medium: 400 mm/s and High: 2000 mm/s) have been conducted. However, the behaviour of shear-critical reinforced concrete (RC) beams has been under-explored. The present study aims to provide insight into the behaviour of shear-critical beams subjected to static and medium loading rates using the displacement control method numerically. To achieve the objective, the Continuous Surface Cap Model (CSCM) for concrete and Piecewise linear plasticity for steel has been adopted, which shows reasonable agreement with the experimental observations. The influence of transverse reinforcement ratio, longitudinal tensile reinforcement ratio, and shear span to effective depth ratio have been summarised. As the loading rate is increased from static to medium, the presence of transverse reinforcement is beneficial for the beams as it aids the concrete in resisting shear force. However, due to the increase in loading rate, the contribution of concrete in shear resistance increases. Additionally, the decrease in the shear span to effective depth ratio and increase in longitudinal tensile reinforcement ratio enhances the load-carrying capacity and stiffness of the shear-critical RC beams. However, for similar longitudinal reinforcement ratios, the lower shear span to effective depth ratio has been beneficial. The behaviour of shear-critical RC beams subjected to high loading rates can be studied in future.