Full Snow + Live Load
Full Snow + Live Load
(OP)
We are having a debate whether to consider full live load + full snow load when designing a member carrying both the roof and the floor, that is 1.2D +1.6L + 1.6S. For example a beam on the second floor level supporting 2nd floor live load as well as the wall supporting the roof trusses. Any thoughts?






RE: Full Snow + Live Load
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Full Snow + Live Load
RE: Full Snow + Live Load
More simply, the basic load combination you show (with typical building load effects) doesn't exist in ASCE therefore it isn't warranted.
"It is imperative Cunth doesn't get his hands on those codes."
RE: Full Snow + Live Load
RE: Full Snow + Live Load
ASCE says there are no shrugs allowed!! ;)
"It is imperative Cunth doesn't get his hands on those codes."
RE: Full Snow + Live Load
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Full Snow + Live Load
1.25D + 1.5L + 0.5S
or
1.25D + 0.5L + 1.5S
whichever produces the most severe loading case. This would be considered the minimum allowed by code and sometimes judgement warrants additional loading be considered.
RE: Full Snow + Live Load
1.2D + 1.6L + 0.5Lr
1.2D + 1.6L + 0.5S
1.2D + 1.6Lr + L
1.2D + 1.6S + L
1.2D + L + 0.5Lr
1.2D + L + 0.5S
A good structural engineer is often a blessing for others.
RE: Full Snow + Live Load
Basically - should we design for full snow on the roof and full live load on the lower floors? I would vote no. From a rational point of view, if you have 3 feet of snow on the roof, you won't have a party in the apartment too.
When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.
-R. Buckminster Fuller
RE: Full Snow + Live Load
Having grown up in the MI's UP with lots of lake effect snow, that full Snow Load can be there for a long, long time.
Also, having worked with Allowable Stress Design for a good deal of my career we would have just added DL + LL + SL and designed for that total. That mindset has not been changed just because the Code's have been changed.
gjc
RE: Full Snow + Live Load
Me no understand - roof live load and snow?
I understand that the nominal loads are a minimum, but circumnavigating their combination doesn't compute for me. Local jurisdictions have always had a history of increasing nominal loads (particularly ground snow, minimum roof live, etc.), but when do you ever see them change their combination?
"It is imperative Cunth doesn't get his hands on those codes."
RE: Full Snow + Live Load
RE: Full Snow + Live Load
There are certainly plenty of code provision which require a grain of salt when reading. Load combinations with well-defined and typical nominal loads is not one of them.
"It is imperative Cunth doesn't get his hands on those codes."
RE: Full Snow + Live Load
See clause 4.1.5.5.
So, the combination of 1.25D+1.5L+0.5S become 1.25D+max(1.5L, 0.5S) for roof.
RE: Full Snow + Live Load
RE: Full Snow + Live Load
Thanks gents!
RE: Full Snow + Live Load