This paper presents an experimental investigation and nonlinear finite element analysis (NLFEA), using the numerical analysis tool ANSYS © , carried out on the shear and diagonal cracking effect on the behaviour of reinforced-concrete (RC) beams made of normal strength concrete (NSC) and highstrength concrete (HSC), with and without transverse reinforcement. Beams were tested using fourpoint bending, by means of digital image correlation (DIC). In the experimental setup, the shear zone was digitised using a high-resolution camera to assess the deformation of concrete in the compression zone and to measure the diagonal crack widths. The results show that transverse reinforcement does efficiently control the diagonal crack width, increases the shear capacity of the beams, shifts the mode failure from shear to flexure, and significantly improves the ductility of beams in the ultimate state particularly when using HSC, given the better quality of the bond developed in the concrete with steel reinforcement. The values of ultimate shear strength obtained experimentally were compared to the corresponding empirical values available in the literature. Furthermore, detailed 3D finite element analysis (FEA) was used to predict the load-deflection response, the ultimate load, the cracking load, the ultimate deflection, the maximum diagonal crack widths and the cracks patterns in RC beams. The difference values between the numerical and experimental values range from −11.08 to +0.6%, from −2.02 to −0.52% and from −13.27 to −1.01% for cracking load, for ultimate load and for ultimate midspan deflection, respectively. The ratio of the predicted to experimental maximum diagonal crack width for the beams ranged between 0.95 and 1.06. Also, a good agreement between the experimental and numerical crack patterns was achieved. Consequently, the FEA model is able to predict the shear response of RC beams with a good accuracy.