[en] The new method allows to compute effective primary stress Peff with the help of an efficiency diagram. Distortion of the structure under cyclic loading is near the distortion obtained by the static application of this effective stress. At elevated temperature, the limitation of the value of this effective primary stress at St, insures the limitation of strain at 1%. Therefore it is recommended to use for Peff the same allowable value than for conventional primary stress. Such a recommendation is very different from the current practice at low temperature. It has been pointed out that this current practices tolerates very much larger elongation under cyclic load than under static load