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Bolt Direct Tensioning

Bolt Direct Tensioning

Bolt Direct Tensioning

(OP)
Hi all,

When it is specified that a bolt is to be direct tensioned to 70% of capacity, would it mean that I can obtain that direct tension force by multiplying the bolt area by its ultimate strength and then by 0.70, or are there additional factors that I have to take in consideration? A prompt response would be appreciated!  

RE: Bolt Direct Tensioning

(OP)
What are some direct tensioning procedures?

RE: Bolt Direct Tensioning

"direct tensioning procedures" sounds like preload (via torque wrench).

there are "standard" tables for preload in "typical" (shear)applications, depending on the size.  a rule of thumb is T = P*D/5 (T=torque, P-=preload, D = diameter).

the high value of preload you've quoted (70% fty) is usually applicable to bolts with tension loads applied; in order that the joint doesn't gap inservice.

RE: Bolt Direct Tensioning

Use the bolt area at the threads.  Only use high strength bolts, A325 & A490.  Tension indicators are very reliable, either the washers with bumps or paint and the break off bolt.

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