A NEW SEISMIC FATIGUE EVALUATION METHOD FOR PLANT PIPELINE BASED ON VIBRATION VELOCITY

(PHYSICAL INTERPRETATION AND POSSIBLE APPLICATIONS)

抄録

In our previous research, a new seismic fatigue evaluation method based on vibration velocity was developed. By this method, it can be shown that the effect of the high-frequency component of the input seismic motion on the fatigue damage could be small. Also, it was possible for the safe side to evaluate all the pipes of each plant by properly selecting the parameters. These previous results were reviewed in this report, and the following matters were reconsidered. It was suggested in the previous reports that the new method could be applied to general piping, but it was only confirmed analytically when a concentrated mass was attached to the tip of a cantilevered pipe, approximating a thin-walled pipe. In this paper, the new method could be analytically derived for more general straight pipes, and the effect of pipe thickness was investigated, and it was shown that the effect of pipe wall thickness could be small. The relationship between the ASME OM code, the new method, and the fatigue evaluation by CAV was considered on the fatigue diagram. Regarding the method of evaluating fatigue from the CAV of the input acceleration shown in previous studies, it was possible to give correct results if the input acceleration was sinusoidal, but the input seismic motion generally included broadband frequency components, and in this case, fairly conservative values were obtained.