Failure Strain Measurement of the Piping System of a Nuclear Power Plant Using Image Signals

When seismic isolation devices are installed in piping systems, it is expected that such devices will be subjected to larger displacement than before their installation because they handle seismic loads, and it is likely that the seismic risks of some facilities will be increased by such displacement increase. In particular, it is highly likely that the seismic risks of piping systems, which connect seismic-isolated structures with conventional ones, will be increased. Previous studies have revealed that the vulnerable part of piping systems is the elbow, and that failures occur due to the low-cycle ratcheting fatigue in the hoop direction. Therefore, in this study, the ultimate state of the elbow was defined as a leakage, and an in-plane cyclic loading test was conducted. In addition, the hoop-direction strain of the steel pipe elbow was measured using an image measurement system, and the failure strain, which cannot be measured using the conventional sensors, was also measured. (paper)