FEM-Design, is a software program for analysis of structural systems using mathematical models and simulations. The technique is used to calculate physical properties of structures, such as stresses and deformations. In this study, FEM-Design is used to calculate bar forces and impact reactions in the design of a deep beam using the strut and tie method, and then compare the results with traditional hand calculations. The purpose of the study is to gain a better understanding of the reliability of FEM-Design in the design of deep beams according to the strut and tie method. The results from FEM-Design are compared to manual calculations and the potential differences form the basis for whether FEM-Design can be used safely with this design method. By analyzing the results of each calculation method, the parts that affect the potential differences can be identified and thus prevented. Finally, we also investigate how FEM-Design can be used most effectively by companies in terms of resource and time efficiency.The deep beam that was designed in the study was provided by WSP in the form of as-built documentations from an apartment building in Jönköping. With manual calculations, reaction forces were first obtained in order to design a strut and tie model. The same strut and tie model was then modeled in FEM-Design under the same conditions for analysis. After obtaining the bar and reaction forces from each calculation method, the comparison began.When comparing the results of the different calculation methods, the differences were very small. The differences in bar forces and reaction forces are 0.0008% - 0.2%, which shows that the results are almost identical. In this case, these results lead to the conclusion that the design, regardless of the method, results in the same amount of reinforcement and design. With such small differences in the results, the user can safely use FEM-Design for the design of deep beams according to the strut and tie method. With a model from the program that the designer can refer to when calculating manually, large calculation errors can be prevented, thereby saving time and energy.Finally, the study shows that FEM-Design can be used safely in the design of deep beams using the strut and tie method. For example, the program can be used as a basis for design according to the strut and tie method and used preventively to avoid large deviations in traditional manual calculations. Furthermore, FEM-Design can also be used to streamline the workflow as an arbitrary model can be used to obtain approximate results and provide an overall understanding of the loadings on the structural element.