The quality and the durability of the concrete structures are affected by lots of degradation processes. In the case of reinforced concrete (RC) structures, the most known degradation process is corrosion of reinforcement. RC members have to fulfil the conditions given in Eurocode (STN EN 1992-1-1, STN EN 1992-2). Horizontal beams are mainly subjected to bending and shear. The paper deals with reinforcement corrosion of stirrups (shear reinforcement) and its influence on the load-carrying capacity of the existing bridge concrete structures. There are considered one type of passive stage calculation and one type of active stage calculation in this paper.