Develop a Method to Estimate the Tension of Torque-Shear High Strength Bolts

Abstract

High strength bolts are widely used as a connector of steel member for steel structure. When the torque shear type high strength bolt is fastened, a pin-tail of the bolt is twisted off. The clamping force of the high strength bolt is normally carried out with a visual inspection, so it is uncertain to measure the clamping force quantitatively. To solve this problem, this study developed a method to identify the clamping force of high strength bolt at a digital mode. The new method identify the induced tension is to analyse the accumulated electric energy applied to high strength bolts until the pin-tails are broken by electric torque wrenches. Valuations of bolt clamping forces and accumulated current data were collected through various experiments. The function of accumulated current data using regression analysis was conducted with various values of bolt diameter. The function of accumulated current data by various values of bolt diameter considering torque wrench rpm was conducted by using regression analysis. The measuring deviation between the values measured by a tension meter and those estimated by a trial product of a measuring device developed in this study is only around 4%. Also, as a result of the research, the trial product is developed including algorithms that calculate clamping force according to the different bolt diameter and electric wrench types.