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Lag Bolt Load Info

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Debra555

Mechanical
Joined
Jul 14, 2012
Messages
28
Location
CA
I'm trying to establish a safe lad bolt (1/2 inch diameter) and (3/8 inch diameter) in a SPF ledger + SPF band joist.

Virginia Tech study is based on Southern Pine ledger + SPF band joist. They say testing shows a 30 OC spacing ( 6 ft joists) with 1/2 inch bolts (using 0.39 in throat).

S Pine has a compressive stress (perp to grain) @ 565 psi. At 30 in OC the deck load would be approx. 375#/ bolt? Would this not cause cracking in the ledger (therefore failure)? They say this 30 in OC is based on a SF = 3.0

Can someone suggest an equation, to come close to this test value for 1/2 inch dia bolts, then for 3/8 inch bolts?
I want to establish a safe load for a SPF ledger + SPF band joist (@ SG = 0.42 - comp perp grain @ 425 psi).

Appreciate your help.
 
I tried using the yield Mode Bolt Equation and got 184 pounds / bolt - this is much less than found be V Tech??
The load on the deck was (40 psf LL + 10 psf DL).

Why is this equation not adequate? It gives a load much less than in tables based on V techs data?
I am grateful for your help here, thanks.
 
Thank you.

Yes, that was the yield equation I used to get the 184 pounds / bolt.
Much lower and very conservative compared to V tech data.
Need to find an equation or method that estimates the bolt load near to V tech test data,
Any suggestions, or links?
 
Call or email Dr. Joe Loferski or Dr. Frank Woeste at Va Tech. They can give you that info or direct you to it.
 
Thank you.

I was hoping someone on line might be able to explain this.
I did not think it was too complicated to obtain a reasonable solution in this form.
I would be grateful for your help.
Thank you
 
Kent ME handbook "Design and Production" has information on safe loads for lag bolt under the fastener" section.
 
Interesting that your value of 184 is about half the 375 value... Did you miss a 2 in there somewhere?

Mike McCann, PE, SE (WA)


 
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