Importance of correct torque value of nuts in steel connection

[ABA102]

Hi Experts,

How the torque value of nuts in connection affects the design of the connection of that connection?
Can you please share also the proper way to calculate the toque value of certain bolt size or else manufacturer's recommended torque value can be reliable?

 

[Agent666]

Torque is a very poor measure of the bolt tension you might achieve.

Read you local code, it should cover acceptable methods for achieving acceptable tensioning. Usually either by the part turn method or via load indicating washers.

 

[ajh1]

Download a copy of the RCSC Bolt Installation Specification,

http://www.boltcouncil.org,

for full guidance on the subject. This is a free download. Tension in the bolt is what you are after, torque is the way to get there, i.e., turning the nut. The required torque varies greatly depending upon the lubrication characteristics of the nut and bolt.

 

[atrizzy]

As unfortunate as it is, I have it on good authority from some lifelong iron workers that the way certain crews perform 'turn of nut' tensioning is to, ahem, "Torque the s*it out of 'em with the gun" and paint the 1/3 turn lines on later.

 

[BridgeSmith]

"...certain crews perform 'turn of nut' tensioning is to, ahem, "Torque the s*it out of 'em with the gun" and paint the 1/3 turn lines on later."

Yeah, I've heard that, too. We only do turn of the nut in a few situations, all of which I believe are too big for a 'gun'. We also recheck them with our own hydraulic wrench, which will crank them to 6000 ft-lbs, if needed.

Although we allow load-indicating washers, we see almost exclusively the twist-off bolts. You can tell at a glance whether they've been tensioned.