Need a book? Engineering books recommendations...

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

Re: FTG UPLIFT

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I have seen these discussions but I am wondering why some engineers exempt only the footing from the 0.6 factor itself under uplift per current code combinations. The only reason I have heard is because "they know that footing weight will be there where other dead loads are often overestimated in the building by engineers". Where I think the intent of the code is to have a uniform safety factor through the entire load path including when you get down to the footing itself. 

Will H

On Wed, Nov 23, 2011 at 9:23 AM, Josh Plummer <joshp(--nospam--at)risatech.com> wrote:
There has been a good amount of discussion about this subject in other
locations (Eng-Tips, Structure Magazine or Structural Engineer). I didn't
provides links to these discussions, but they shouldn't be all that tough to
find... just Google it.

The old code requirements were to use 0.9*DL for the uplift combinations.
But, you were required to have a 1.5 Overturning moment safety factor.

The new code consolidates this by using a load factor of 0.9 / 1.5 = 0.6.

So, that's where the 0.6 DL comes from. If you continue to use the old load
combinations (with a 0.9 factor), that would still be valid as long as you
apply the 1.5 safety factor when you check overturning.  If you use the new
LC's then you don't have to worry about doing an overturning stability check
because it is already taken care of.

Sincerely,  

Josh Plummer, SE
 
RISA Technologies



******* ****** ******* ******** ******* ******* ******* ***
*   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
******* ****** ****** ****** ******* ****** ****** ********