Although reinforced concrete is the most commonly used construction material worldwide, there are still ongoing discussions about the shear behaviour of reinforced concrete beams without stirrups. While there is a general consensus about the existing mechanisms transferring shear forces, their ultimate bearing capacity is highly controversial. Complex interactions between these mechanisms and their tendencies to change with alternating crack patterns hinder the development of a worldwide approved mechanical model. Nowadays only empirical approaches with a partial analytical background have been developed, which lead to different results depending on the used model and its variation of the transferring shear forces. The first chapter introduces the problem, with the objective to find a generally acknowledged shear model based on a mechanical background. Relying on literature research, the second chapter presents existing models for the calculation of the total lateral force bearing capacity, and design models based on different common standards will be discussed. Under the guidance of T. Huber, a total of fifteen „Push-Off“ experiments and seven shear tests on beams were performed at the institutes own laboratory in November 2015 and afterwards described and evaluated by Hackl. In addition to the friction of cracks, different types and grades of concrete were examined and compared with each other. The compressive strength was also varied between 40 and 60N/mm2. Supplementing these tests, through the course of this work, the series of experiments was extended by six more „Push-Off“- and three shear tests on beams, including still missing concrete grades DNC40 (normal concrete with granular aggregate from crushed dolomite) and QSCC40 (self-compacting concrete with quartzitic sand). In order to measure the crack kinematics continuously, a three-dimensional digital image correlation system was used. The experimental design, the structure and measuring concept are described in chapter three. Finally, in chapters four and five, the obtained measurement results are evaluated and compared to existing models. Therefore, the crack kinematics and shear stress curves, obtained by evaluating the „Push-Off“ experiments, were compared with each other and investigated with respect to possible influences from various parameters. Furthermore, the obtained distributions of stress are compared with predictions of existing friction models to evaluate their differences and determine their accuracy in calculating existing stresses. Subsequently the shear force carrying capacities obtained by investigating the shear force tests are compared with available design concepts and different models for shear. Also, diverse approaches to describe the shear transverse actions such as aggregate interlock, dowel action and the shear stresses of the fracture process zone and the concrete compression zone are compared. Based on results derived from these comparisons, a combination of models was found which suites the shear resistance in order to investigate the load components prevailing therein. A conclusion transpires, in which the majority of the shear force is either transferred from the concrete compression zone or by the aggregate interlock. Through the course of this masters thesis, the image correlation system proved to be a viable measuring tool to record and analyse „Push-Off“ experiments and shear tests, since the behaviour of the crack patterns with increasing load applications could be measured and evaluated. Due to 6 those measurements, a relation between crack opening, sliding and tilting was found. Furthermore, the linear model for aggregate interlock released by Model Code 2010 proved to be a good calculation method to estimate the quantity of shear force transferred with aggregate interlock. In combination with the concrete compression zone model by Zink a satisfactory consensus could be achieved with the experimentally obtained shear resistances. Apparently, additional tests containing similar experimental procedures and analyses will be necessary, since no general statements could be made due to the variance of the measured shear resistances. Moreover, previously observed tendencies could be confirmed and a connection between concrete quality and shear force bearing behaviour could be identified through additional tests.