Report on the exposure test of high-strength friction-grip bolt by yield-point method

Abstract

Exposure test of high-strength friction-grip bolts fastened by yield-point method has been conducted for more than 20 years, but delayed fracture of the bolts has not been found. Most of the high-strength friction-grip bolts for Honshu-Shikoku bridges were fastened on the sea by yield-point method, by which high-strength bolts are fastened with higher force than by conventional torque method. Delayed fracture of bolts often occurs in severe corrosive environment and with high stress in the bolts. The exposure test has been conducted to study the characteristic of delayed fracture of the bolts. However, delayed fracture of the bolts has not been found.