Earthquake resistance design of reinforced concrete beams in accordance with EN 1998-1 requires the non-collapse and the damage limitation under the design seismic action. The earthquake resistance design in accordance with EC8 is introduced in the beginning. The continuation of diploma thesis introduces the designing of reinforced concrete beams for medium ductility class (DCM) and high ductility class (DCH) in details. In most cases, programs and applications for construction analysis and design enables designing only in accordance with EN 1992-1, the controls of earthquake resistance design must be done by hand. Application called Gredko, designs reinforced concrete beams in accordance with EN 1998-1. Analysis and designing results by EC2 are input parameters for application Gredko, where the conditions of earthquake designing are checked. The completion of designing conditions and results of shear reinforcement determination are visible on output results list. Design resistance to bending in critical and uncritical sections enables the program a completion of designing concrete reinforced beams. Graphical layout of algorithm evidently shows the procedure for beams designing. Program MATLAB was used for making out application. User-friendly way of working with application Gredko is enabled by MATLAB tool, called graphical user interface development environment. The diploma thesis, besides introducing classical programming of functions also introduces principles of working and programming the graphical user interface. Application Gredko was tested by examples and results were compared with results from different analyses. In the first testing example, a procedure of working with application is introduced with interactive windows; by other two examples input parameters and results comparison are shown.