Bolted Joints Under Tensile Service Loads: The Effect of Torsion in the Bolt on In-Service Clamping Loads

In order to determine how bolted joints behave under conditions of tensile external loading, tests were conducted on bolts which had been tightened into joints by means of (a) elastic range, (b) yield, and (c) over-yielding tightening. The loading tests showed that the maximum clamp load which the bolt would exert on the joint without permanent extension was the uniaxial tensile yield load of the bolt. This was observed even when torsional stress was present in the as-tightened bolt, and for all three tightening methods.