| In current RCSC Specification, ASTM F1852 twist-off tension-control bolt assemblies are directly recognized and twist-off-type tension-control bolt pretensioning is considered as one of the four bolt pretensioning methods. Twist-off tension-control bolt is characterized by the splined end which will be sheared off at a circular notch (torque control groove) when the required pretension is reached. Twist-off tension-control pretensioning is in fact based on torque control. Factors that affect the pretension of twist-of bolts are the bolt material strength, geometric properties of the bolts, thread conditions, lubrication conditions at the bolt and nut threads as well as the washer. A series of test programmes were performed to examine the influence of lubricants on installation, including time delays, weather conditions at time of installation, as well as the effects of other parameters on the bolt pretension. In addition, reinstallations of removed twist-off tension-control bolts with turn-of-nut pretensioning method were also investigated. |
PDF Full Text Request