Lag Bolt Load Info

[Debra555]

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.

 

[Debra555]

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.

 

[oldestguy]

The US Forest Products lab Wood Handbook is on line. I think chapter 8 would help you.

http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p

 

[Debra555]

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?

 

[Ron]

Call or email Dr. Joe Loferski or Dr. Frank Woeste at Va Tech. They can give you that info or direct you to it.

 

[Debra555]

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

 

[chicopee]

Kent ME handbook "Design and Production" has information on safe loads for lag bolt under the fastener" section.

 

[bridgebuster]

Try the American Wood Council web site's lag bolt calculator:

http://www.awc.org/calculators/connections/ccstyle.asp

 

[bridgebuster]

Here's an example from AWC:

http://www.awc.org/pdf/DA1-LagScrew.pdf

 

[msquared48]

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)