Soundness Evaluation Method Using S-N Curve for Equipment Supports Subjected to Machine Vibrations

Abstract

The degradation factors considered in the evaluation of long-term soundness of reinforced concrete structures in nuclear facilities in Japan are heat (high temperature), irradiation, carbonation, chloride penetration, alkali silica reaction, and machine vibration. As described in the "Guidelines for Maintenance and Management of Structures in Nuclear Facilities," the soundness evaluation of equipment supports against machine vibration is very rudimentary compared with the evaluation methods against other factors since the degradation state due to machine vibration cannot be identified until cracks are visually detected as degradation phenomena. The phenomenon of fatigue of equipment supports can be expressed using an S-N curve that shows the relation between the maximum stress ratio and the fatigue life under repeated loading. During normal operation of nuclear facilities, the maximum stress ratio of repeated load is very low and less than the long-term allowable stress level, and the fatigue life is very long. Since the number of load repetition can be known from the operation period of the facility, soundness against fatigue can be evaluated using an S-N curve. In this paper, a soundness evaluation method using an S-N curve for equipment supports subjected to machine vibrations is proposed.