Determination of critical circumferential through-wall crack sizes regarding load reduction by increased flexibililty in piping systems

Piping systems in power stations are not only loaded by the system pressure and force controlled bending moments, e.g., due to the weight of the system, but also by additional bending moments caused by the thermal expansion of the hot system and prescribed motions, as in the case of an earthquake, resulting in displacement controlled moments. To determine critical circumferential through-wall crack sizes in pipes, a method based on the J-integral has been developed, which takes into account the load reduction due to the increased flexibility of a flawed section. The method is presented and compared with results by the finite element method and experimental data.