Bolt Tention

[RonBurgundy]

I've come across a question that I can't find the answer to.

For a bolt placed in tension. Is there a AISC formula for determining whether the bolt head could shear through a connecting plate and "pull out" or "pull through"? Not in the bolt bearing tearout sense calculated in J3-6a which deals with a bolt shear situation. But rather in the perpendicular direction to that in a bolt tension situation.

I know for cold form steel. AISI does screw pull-out and Pull-Over formulas for tapping screws, but I don't know of any equivalent measures for bolts.

I would expect a formula that looks like Constant * the bolt head diameter * the thickness of the connecting plate * FU

 

[Ron]

For hex head bolts, that is a failure mode that would most likely not occur. The bolt heads are designed to prevent "pull over".

It can happen in very thin materials (sheet), but isn't a big consideration for thicker materials (plate).

 

[RonBurgundy]

thanks guys,

I do have the bolts connecting through a thin plate (18ga). Its not my design we are doing due diligence on a job that we took over, and the contractor is concerned because the curtain wall isn't supported by angle brackets anchored into the concrete but rather cold form steel stud framing.

For this situation should I do the "pull-over" calc and use the hex head as the washer diameter? Or is it not really a concern?

 

[Ron]

For 18ga material, I would do the calcs, but I would also expect them to be OK unless your bolt size is quite large relative to the sheet steel. Generally, for that thickness, I would expect screws, not bolts, and probably not larger than 1/4" dia.

 

[RonBurgundy]

I am giving them the choice between bolts or #14 self tapping screws.

Thanks for the help.

 

[racookpe1978]

Reminder!

Use the actual area of the hex head - the area of the HOLE in the plate.

Don't use the area of the bolt itself - that won't be the "pull through" diameter that is important. The drilled/punched hole determines what the theoretical limiting area comes from.

Also: The limiting shear "distance" is that minimum distance between the edge of the drilled hole and the closest hex corner when the bolt is at its closest point of approach as it slides around inside the drilled hole.

To illustrate - and slightly exaggerate! Imagine a 1/4 dia bolt with a nominal 7/16 (across-the-flats) head "rattling around" inside 3/8 diameter hole. Your pull-out value would be significantly different than that same 1/4 dia bolt sitting inside a 1/4 dia standard washer, much less compared to a 1/4 dia fender washer that's 1-1/2 inches across.