Abstract
Bolt tension behavior of high-strength bolt friction-type joint with frequently repeated slips has been developed. Bolt tension has been measured by a strain gauge inserted into the hole along the bolt axis. The following conclusions are based on the tests of symmetric butt splice subjected to frequently repeated cyclical loads (up to 7 Hz) which exceed the frictional resistance of the joint. (1) Bolt tension keeps almost constant during each major slip, if the joint has the normal hole clearance. (2) Mathematical expression for bolt tension decreasing with repeated slips has been developed. B=B_o+B_f・(1-exp(-(N-1)/T))+k・(N-1) This expression is applicable to the case that either quasi-statical or dynamic loads are applied to the joint. (3) Bolt tension behavior gets into the stationary period, after about three repetitions of slips of the joint. (4) Bolts come loose by nut rotation in case of the slip repetition of the joint. (5) Nut rotation angle increases proportionally to the number of slip repetition. (6) Bolt tension decrement during the stationary period is mostly due to nut rotation. (7) Bolt tension decrement is influenced by either frequency or amplitude of loads. Bolt tension decreases more when the joint is subjected to larger amplitude or lower frequency of loads.
