The Relationship between Torque, Tension, and Nut Rotation of Large Diameter Anchor Bolts

The purpose of this investigation was to determine the relationship between torque, tension and nut rotation of the large-diameter anchor bolts used on cantilever sign supports. This research was in response to concerns about loose nuts found o these anchor bolts during field inspection of in-service sign supports, along with concerns regarding an unspecified tightening procedure. Results of this investigation were used to determine the appropriate anchor-bolt tightening procedure and to determine whether or not turning the nut past the snug position imparts the desired amount of tension in the anchor bolt. This investigation also determined the appropriate torque for checking anchor-bolt installations in the field, the effects of bolt relaxation, and any problems of thread stripping from tightening.