### Author Topic: Ledger Bolt Spacing?  (Read 8094 times)

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#### CAB

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##### Ledger Bolt Spacing?
« on: January 22, 2005, 11:12:58 PM »
I've been looking high & low with no luck for a load table for ledger bolt size/spacing
when bolting a double 2x8, 2x10 or 2x12 pressure treated ledger to an 8" CMU wall for
top chord bearing floor trusses.

SSTD 10-99 has a table but that guide is very conservative and groups the spacing & size based
on floor truss lengths. I would like to see it based on load pounds per bolt or PLF.

Anyone have any info?
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#### Keith™

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##### Ledger Bolt Spacing?
« Reply #1 on: January 23, 2005, 10:06:24 AM »
Try this for a simple way to calculate spans loads and # required.

A single 1/2" A.B. = 1430# in double shear (2 - wood ledger members)

This means that a 1/2" A.B. in a 2x sill would get 1/2 the value of a 1/2" bolt in double shear with members of 3" thick - 1430#/2=715#

Does that make sense?

Based on the above ...

14'-0" Trib span
40# LL
10# DL
50# TL
50#X14'=700# PLF
A.B. in double 2x member = 1430#
1430#/700# = 2'-0 1/2" max spacing

Remember this is based on the bolts being embeded in concrete at pour time and does not include epoxy set bolts. You should check allowable shear for epoxy set A.B. with the supplier.
Also the maximum size of the hole in the ledger is A.B. dia + 1/16". Larger holes reduce the bearing allowance considerably. This is also with loads perpendicular to the grain...although you wouldn't have them any other way on a ledger.
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#### CAB

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##### Ledger Bolt Spacing?
« Reply #2 on: January 23, 2005, 10:39:37 AM »
Great info Keith.
That is how I approach the problem but I have some tables for bolts in shear 1/2" & 5/8" bolts but they are for 'Douglas Fir'.
Do you remember where your source for 1/2" bolt is?
Quote
A single 1/2" A.B. = 1430# in double shear (2 - wood ledger members)

I will usually spec 5/8" bolts for the extra load capacity.
The shear tables I was looking at were excerpts from 'NDS 1991 edition'.
I would purchase the reference if I was sure it had PT pine or SYP tables.

I don't like not knowing where the limits are.

I see many prints in this area where they call for 1/2" bolts @ 24" OC.
And from my calculations they are inadequate for the floor spans.

Thanks
CAB
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#### Keith™

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##### Ledger Bolt Spacing?
« Reply #3 on: January 23, 2005, 12:33:52 PM »
The main problem I have encountered is not the lumber specs, but rather the bolt specs. DFL is comparable to SYP in most properties with DFL being a bit stronger in the deflection values. I think the controlling factor on the SYP would be compression at attachment.

Generally speaking a 1/2"dia bolt will give you about 1 1/4 sqin of bearing per bolt (double ledger). Since deflection is not a factor, we should consider the compression at the connection point. If you do the calculations, I think you will find that 1 1/4" bearing for a 2'-0" span is likely plenty sufficient, even in SPF.

What I normally do is calculate the weight of the span being addressed, in this case 2'-0" and determine if the bearing per bolt is sufficient for the member. I think you will find that many times the required bearing surface is significantly less than you would imagine.

I would suspect that a 5/8" dia A.B. with a good embedment of at least 4" in a poured wall spaced at 24" o/c should suffice for anything in residential up to a 32'-0" span (16'-0" trib distance @ 50# TL)

I'll look and see what I can find, but I don't have my tables at home. When I get to work tomorrow, I'll send you a few things that I am sure you will find very helpful.
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#### CAB

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##### Ledger Bolt Spacing?
« Reply #4 on: January 23, 2005, 01:43:43 PM »
Digging through all my books I did find this Shear table
It looks like you should be able to take the 5/8"  value for 1.5" lumber SP 560# and double it for 2 members. 1120#
But if you look at 3.5" member the value is only 780#
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#### Keith™

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##### Ledger Bolt Spacing?
« Reply #5 on: January 23, 2005, 06:43:40 PM »
I am not sure what to make of that page, it does not seem to jive with any of the engineering data I have received in the past. When I get that info, I'll forward it.
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#### CAB

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##### Ledger Bolt Spacing?
« Reply #6 on: January 23, 2005, 07:34:35 PM »
Thanks
CAB
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#### Bob Garner

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##### Ledger Bolt Spacing?
« Reply #7 on: January 24, 2005, 11:41:58 AM »
A bolt in this connection is in single shear.  The table looks like the same one in NDS '97 (Table 8.2E).  Since this table is for single shear, you don't double the bolt capacity but use the value for a 3" thick side member (interpolate between 2.5" and 3.5" in the table).

Bob

#### CAB

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##### Ledger Bolt Spacing?
« Reply #8 on: January 24, 2005, 12:01:28 PM »
Quote from: Bob Garner
A bolt in this connection is in single shear.  The table looks like the same one in NDS '97 (Table 8.2E).  Since this table is for single shear, you don't double the bolt capacity but use the value for a 3" thick side member (interpolate between 2.5" and 3.5" in the table).

Bob

I would guess you are looking at the same table.
Question is why when the area is doubled, 1.5 to 3, is there such a limited increase of
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#### Bob Garner

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##### Ledger Bolt Spacing?
« Reply #9 on: January 24, 2005, 01:13:22 PM »
The capacity is not proportional to the area because bending of the bolt and subsequent bearing of the bolt on both the wood and the concrete control and they are not linear.  Does that make sense?  Everybody feels the values in this table are very conserviative.  I think it was the magazine, "Journal of Light Construction" that did a test of actual ledger connections in various configurations and came up with more realistic values.  I'll hunt for the article tonight.

Bob

#### CAB

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##### Ledger Bolt Spacing?
« Reply #10 on: January 24, 2005, 04:08:43 PM »
Quote from: Bob Garner
The capacity is not proportional to the area because bending of the bolt and subsequent bearing of the bolt on both the wood and the concrete control and they are not linear.  Does that make sense?  Everybody feels the values in this table are very conserviative.  I think it was the magazine, "Journal of Light Construction" that did a test of actual ledger connections in various configurations and came up with more realistic values.  I'll hunt for the article tonight.

Bob

Yes it makes sense & i though the table was very conservative when I look at what is being done in the field.
I would very much like to see the other table.
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#### CAB

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##### Ledger Bolt Spacing?
« Reply #11 on: January 24, 2005, 08:29:24 PM »
Bob,
I have the 'Residential Structure & Framing' from JOLC and it is a very good reference.
What do you think of the \$99.00 Online offer that they have.
JOLC
Do you research much in there data base? Do you have the CD of back articles?
Have you found it useful?

I looked for the article you mentioned but could not find it.

Thanks
CAB
I've reached the age where the happy hour is a nap. (°¿°)
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#### Bob Garner

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##### Ledger Bolt Spacing?
« Reply #12 on: January 25, 2005, 03:38:24 PM »
Hi Cab,

The JLC article on ledger connections was in March 2004.  I forgot to bring it to work today but I will tomorrow.  I don't have scanning capabilities but I can fax them to you if you shoot me your fax number.  Did you want the NDS Table 8.2E also?

I have a subscription to the magazine but I have never looked into any of their other stuff.

Bob

#### CAB

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##### Ledger Bolt Spacing?
« Reply #13 on: January 26, 2005, 09:33:38 AM »
Quote from: Bob Garner
Hi Cab,

The JLC article on ledger connections was in March 2004.  I forgot to bring it to work today but I will tomorrow.  I don't have scanning capabilities but I can fax them to you if you shoot me your fax number.  Did you want the NDS Table 8.2E also?

I have a subscription to the magazine but I have never looked into any of their other stuff.

Bob

I PMed you with my fax number, in hopes that you can make the long distance call.
Thanks again.
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#### Bob Garner

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##### Ledger Bolt Spacing?
« Reply #14 on: January 26, 2005, 10:22:08 AM »
OK, CAB, the stuff is on it's way.  Make sure you get all the pages (9 plus a cover sheet), our fax machine isn't the best.

Bobber

#### CAB

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##### Ledger Bolt Spacing?
« Reply #15 on: January 26, 2005, 10:28:39 AM »
Quote from: Bob Garner
OK, CAB, the stuff is on it's way.  Make sure you get all the pages (9 plus a cover sheet), our fax machine isn't the best.

Bobber

Got it, Looks like some good info.
I'm going to read now. Got my highliter and I'm ready to go.
Thanks
I've reached the age where the happy hour is a nap. (°¿°)
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