Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Lag Bolt Zperp values in thin members

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I don't "allow" it whan I'm resposible.  My first choice is to set an extra set of columns 2-3' out from the residnece and cantilever back.  That's usually what happens if I'm brought in late.  I've also spec'd using a 4x6 bolted into the ledger (when the ledger is tall), and letting the brick mason leave a "hole" in the brick, every 4' or so.  The down side is having to detail the band/joist/floor/sill connections to take the eccentric moment.  Third option is setting the beams to span from sill to post (perp. to the bldg wall) and running the joists side-to-side.  The downside to this is the large penetration of the building envelope and the ensuing flashing, which usually gets done incorrectly or incompletely.

I have one on the boards now that will require a combination of these. There is a deck at the ground floor, where I can incorporate pilasters in the CMU foundation to carry the beam at the building end. Unfortunately, continuing that vertical support up is impractical as the architect finished the facade before I came on board.

I should mention that the lateral stability of decks is, imho, an issue, especially where there is no direct, continuous ledger at the house.  I don't do enough to have a "standard" way of dealing with it  - I just run  some numbers and add braces each time.
Jordan


Gary Hodgson & Associates wrote:
Jordan,
As a little bit of an aside, what do you do about 
bolting to or through a brick veneer. I received a
second inquiry in two years, this week about a deck
ledger bolted through brick to the rim board; both
times it has been a government official. My position
has been that there is nothing in our code that forbids
bolting to or thru brick.  I don't like bolting directly
and only to a brick veneer, but there are thousands of
home-made decks out there with this manner of connection
without any known problems. TIA
Gary

On 20 Apr 2006 at 8:37, Jordan Truesdell, PE wrote:

  
I've just run across an interesting table in the Virginia version of 
the 2003IRC, and wonder what others thoughts are on the matter. The 
table in question is R502.2.1.1 (you can see the VA table here ) and 
it gives ledger lag spacing for deck connections to residential 
construction. If you back calculate the spans, you get 375# per 1/2" 
lag. For example: 

12' deck joist span, 
50psf TL (10D/40L I'm assuming), 
1/2" diameter lag screw through a 
 2x S. Pine ledger and 
 2x solid sawn rim joist (no species provided, SPF is the most 
common solid sawn rim material)
so 12'/2 (trib) x 1' x 50psf = 300#/ft

For a 12' span, the table requires a 1/2" dia. lag on 15" centers. So 
300#/ft x 1.25' = 375#. 

That's all well and good, except that according to the 2001NDS: 

1) a single shear connection for a 1/2" lag for a 1.5" side member 
when loaded perpendicular to the grain is 250# when the penetration 
into the main member is 8x the lag diameter, or 4". and

2) The minimum penetration is supposed to be 4D, which you cannot 
have with 2x lumber, even if you count the sheathing (7/16"+1.5" < 
2").Even at the minimum penetration of 2", the allowable shear value 
is only 125#. 

3) The table value I gave was for S.Pine/S.Pine., for SPF the value 
drops by 25%. 

Stranger yet, the values for through bolts are nearly double (29" vs 
15") at the 12' deck span. 725# for a single 1/2" through bolt? NDS 
gives 330# for 1-1/2" to 1-1/2" w/ side member loaded perp to grain.

I hadn't taken the time to calc out these numbers until this morning, 
when I got a call on the ledger attachment for a deck with a hot 
tub.I assumed that lags couldn't be used with the tabulated values, 
but that the VA code officials had a specific analysis done for the 
short penetration. Looking at the table more closely, the numbers 
make no sense. I haven't seen a mention anywhere of the values 
determined through testing. Am I missing something technical here?

Thanks to those who made it this far. 

-- 
Jordan
******* ****** ******* ******** ******* ******* ******* *** * Read 
list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was 
sent to you via Structural Engineers * Association of Southern 
California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, 
please go to: * * http://www.seaint.org/sealist1.asp * * Questions to 
seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is 
public domain and may be re-posted * without your permission. Make 
sure you visit our web * site at: http://www.seaint.org ******* 
****** ****** ****** ******* ****** ****** ******** 
    


******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ******** 



  
******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********