The master thesis discusses the multi-story office-residential building, located in Krško. The reinforced concrete monolithic floor slabs represent the horizontal load-bearing elements and serve for arrangement of the area loads. The slabs are restrained by reinforced concrete walls and reinforced concrete frames. The elements represent the system for transmission of the vertical loads, loads of wind and horizontal seismic impact. From the architectual plans, based on certain simplification, were made idealized models of the load-bearing structure which as realistically as possible must describe the discussed construction. For the analysis of the horizontal load-bearing elements the program softwere SAP2000 is used. In the program an idealized mathematical model of the typical floor slab was created. For the analysis of the vertical load-bearing elements we made an idealized mathematicah model of the load-bearing structure of the global building. Slovenia is located within a seismic area and in most cases for the design of buildings a proper seismic limite state is relevant. For this purpose we used the program softwere ETABS, which is intended for the analysis construction on impect of the horizontal seismic impact. The arrangement of the load-bearing elements in the ground floor vary considerably from the load-bearing elements in story floors. It turns out the original design of the load-bearing structure loads is too big, particularly in the staircase core. By adding reinforced walls the load-bearing structure is strengthened and provided with adequate capacity of the staircase core in seismic design state. The reinforced plans in the program ArmCAD were displayed for reinforced concrete slab and staircase core. The program is an integral part of the AutoCAD and allows the determination of optimal reinforcements.