Slip Critical Connections 2

[cpthaas]

What are the torque requirements for a 3/4" Dia A325 bolt in a slip critical connection. Where in ASD manual do you find it?

 

[CWIC]

You should be seeking the required tension and not a torque value. Table 4 of the ASTM A325 or A490 Bolts has the information you are looking for in the back of the AISC - ASD, 9th edition. Table 5 will give you the turn of the nut minimum rotational values.

 

[Lutfi]

CWIC is absolutely correct. You need to tension the bolt to the required tension. I recommend that you require the erector to you load indicating washers of some DTIs (direct tension indicators).

Visit the following site

http://www.appliedbolting.com

They have great deal of information on DTIs.

Good luck

 

[jike]

You might want to consider the use of TC (Tension Control) bolts. They have a spline that twists off at the required torque.

 

[CSEllc]

TC bolts are the way to go. I haven't seen a DTI in about 7-8 years. They are clumsy to use.......You need the gage.

Most if not all the erectors in my area (NE-CT) use TC bolts. Even if the SER does not specify them.

Regardless of what bolt type you use. The most critical ( little joke there) is that the bolts be properly tightened. The erector should first snug-up all the bolts to bring the steel (connection angle and beam web) into contact before fully tensioning the bolts. If the bolts are not first "snugged-up", you will have relaxation of the bolts in which they appear to be fully tightened but in reality are loose.

 

[NigelB]

Getting back to your question about bolt torque, the erector should calibrate impact wrenches on site to correlate the torque with the required tension. This should be done with each wrench at least once a day. Similarily the steel inspector should calibrate his torque wrench in the same manner if using torque to check the tightness of bolts.