5.2.3 Strength parameters

In principle, the strength parameters for concrete, reinforced and pre-stressed concrete, including limits of ultimate limit strains to be observed, must be taken as per DIN 1045­1 [54]. Further details specific to nuclear power plants can be found in DIN 25449 [15].

To determine the design values, the characteristic strength parameters must be divided by the partial safety factor gM in each case. Concrete compression strength fc must be divided by gc and the strength of concrete steel and pre-stressing steel (concrete steel: yield stress fyk and tensile strength ftk, pre-stressing steel: yield point fp0.1k and tensile strength fpk) must be divided by gS, using the partial safety factors as shown in Table 6.2 for the proofs in ULS depending on the category of requirements concerned.

For concrete compression strength, the influence of long-term effects and the influences on design-relevant concrete characteristics, such as the effects of load duration, curing and loading speed, must be taken into account. In certain justified cases, variations from the design-relevant characteristics of concrete as a construction material from the character­istics on which DIN 1045-1 is based may be used (deviations from design values). This applies in particular to the concrete getting stronger as it cures in long-standing reinforced concrete structures and the increase in strength of concrete stressed in multiple axes or high expansion rates and the influence on the ultimate limit strains of concrete.