[en] The extreme environmental and abnormal loads are of decisive importance for the statical and dynamical design of the safety related buildings of a nuclear power plant (npp.). The arising forces act for a very short time interval, but as a rule with a load peak, whose intensity has been so far uncustomary in structural engineering practice. The treatment of these loading cases requires dynamic investigations by means of special computer programms. For economical reasons, the non linear behaviour of reinforced concrete (r/c) must be considered in these investigations. For heavily reinforced structural members, whose design is mainly governed by the above mentioned extreme loadings, the utilisation of high tensile steel for example the quality Bst 1080/1320 (reinforcing steel, yield point 1080 N/mm2, ultimate strength 1320 N/mm2) leads to reasonable economical advantages and allows and easier assembly of the reinforcing bars (re-bars). Acc. to German Standards, special high tensile steels can be stressed up to the yield point for loadings with a very low probability. (Author)