High Strength Friction Grip Bolts (HSFG) bolts are high strength structural bolts which have been tightened such as to induce tension in the bolt shank. Due to the tension in the bolt, the interface between the plies (steel members in a joint) cannot move relative to each other.
High friction grip bolts are commonly used in structural steelwork. They normally consist of high tensile strength bolts and nuts with washers. The bolts are tightened to a shank tension so that the transverse load across the joint is resisted by the friction between the plated rather than the bolt shank’s shear strength.
HSFG bolts have the following advantages when compared with normal bolts: The performance of preloaded HSFG bolts under fatigue loading is good because the prestressed bolts are subjected to reduced stress range during each loading cycle when compared with unloaded bolts. For structures adjacent to machinery which generate substantial vibration, preloading bolts can help to avoid the loosening of bolts. HSFG bolts are used in connections where any slight slip movement would render the integrity of the whole structures break down. (iv) Owing to its high tensile strength, it is commonly used in connections which require the taking up of high flexure and the tensile stress generated could be readily resisted by it high tensile strength.