供用中検査を受ける高力ボルトの信頼性解析

点検間隔と抜取り率の決定について

抄録

A large number of high tension bolts are used in highway and railway bridges. High tension bolts are known to be susceptible to delayed fracture in humid environments. In order to assure the safety of bridges, these bolts are subjected to in-service inspection by sampling. In the present paper, a reliability analysis is carried out for inspection by random sampling at a constant interval. First, a theoretical equation of the reliability of a bolt subjected to inspection and replacement is derived as a function of n and q, where n is the number of inspections during the design life and q is sampling fraction. Then, by using this equation, numerical examinations are conducted for several cases to find possible combinations of n and q which satisfy a given reliability requirement. The time to failure of a bolt is assumed to follow a two-parameter Weibull distribution. The results show that the reliability of a bolt subjected to inspection and replacement is almost determined by the product of n and q.