Residual clamping force of bolt connections caused by sectional damage of nuts

Abstract To consider sectional damage of bolt connections by corrosion damage for the maintenance of steel structures, the residual clamping force of bolt connections was quantitatively examined depending on sectional damage of the nut sections developed from artificial cutting in this study. Thus, friction connection specimens using high-strength bolt connections were fabricated, and the nut sections in the bolt connections were artificially damaged using handheld cutting tools. To measure the change in the clamping force of the bolt connections, the change in strain measured in the bolt using a strain gage was examined after clamping and inducing artificial sectional damage to the nut. The bolt size and the shape and extent of sectional damage were the parameters considered in this study. The weight of the nut was measured after inducing artificial sectional damage to nut to calculate induced sectional damage of nut. From tests results for bolt connection with artificial sectional damaged nuts. The residual clamping forces of the bolt connections were decreased because of the reduced tensile resistance of the bolt connections, affected by the sectional damage of the nut. In case of high sectional damage in the nut section, a relatively higher change in the clamping force was found in the tested series of nuts. From regression analysis of the residual clamping force of the bolt connections, the estimation equations for the change in the residual clamping force developed from sectional damage of the nut were formulated using the damaged volume of the nut and diameter of the remaining nut section for the maintenance of bolt connections in steel structures.