Session: SE-09-01 Advanced Seismic Evaluation and Code

Paper Number: 61943

Start Time: Tuesday, July 13, 2021, 08:00 PM

61943 - Strength Distribution Characteristics of Elbow Pipes Considering Low Cycle Fatigue Based on Analysis 

In seismic fragility assessment of a nuclear power plant, the failure mode of piping systems is usually assumed as ductile rupture. However, because there are some previous studies that report that the failure mode of piping systems is fatigue, it is important to provide a fragility assessment considering fatigue as the failure mode. In this study, we verified a method for deriving the strength distribution characteristics of elbow pipes from material properties in order to conduct the seismic fragility assessment considering fatigue failure. The number of repetitions was set to 150 times, and the strain occurring at the elbow pipes changed in this verification. The elbow pipes to be examined was made of carbon steel. The nominal size of elbow pipes was 200A and the nominal thickness was schedule 40. The finite element analysis was conducted with the condition that the elbow pipes underwent forced displacement. The strain of elbow pipes was obtained from the analysis and the probability of fatigue failure was evaluated when deformation was repeatedly applied 150 times at this strain level. The probabilistic fatigue curve was obtained from best-fitting fatigue curve and used for the evaluation. The strength distribution characteristics of the elbow pipes was obtained from the relationships between the probability of fatigue failure and the forced displacement because the forced displacement applied to the elbow pipes corresponded to the strain of the elbow pipes.

Presenting Author: Ryuya Shimazu Central Research Institute of Electric Power Industry

Authors:

Ryuya Shimazu Central Research Institute of Electric Power Industry
Michiya Sakai Central Research Institute of Electric Power Industry
Yohei Ono Central Research Institute of Electric Power Industry
Shinichi Matsuura Central Research Institute of Electric Power Industry