live load reduction on wall strip footing?

[DavidStructural08]

I know the answer would be yes for strip footing supporting a concrete/CMU load bearing wall. But what if the wall is cold-formed studs spacing at 12"-24" o.c.

I think probably we could not get much reduction on live load for wall studs due to the spacing (Width * spacing (12"to24"). But it seems for the strip FTG, we could have a much larger tributary area (width * strip FTG length).

am I rite?

 

[hokie66]

Why would you want to do it? Just think about all the other assumptions you have made regarding loading and capacity. Such "precision" in design of a strip footing is unwarranted.

 

[DavidStructural08]

well. just curious from code point of view if we could do that.

 

[msquared48]

I can see that for 3 to 4 floors thie reduction could be quite a bit, especially considering the steel stud bearing walls at 7 to 8 psf dead load as compared to 45 to 50 psf for cmu and 75 to 100 psf for concrete. Relatively speaking, the live load percentage and reduction effect will be realized more with the steel studs.

However, as Hokie said, being the foundation, why would you want to save money on the most basic and critical part of the structure? If your footing was 2' wide, you might get it down to 1'-6", 3', maybe 2'-4".

Money is far more likely to be saved without compromising the structure on a multi-story structure here reather than a residence or single story commercial. Remember that the live (snow) load on the roof is not reduceable, only the floor live loads. Needless to say, I like redundancy in structural systems, even if it is only extra capacity.

Mike McCann
MMC Engineering

 

[haynewp]

I have seen it done before on multi-story parking decks with precast walls.

 

[asixth]

How many floors is the strip footing supporting. Live load reduction is based on the statistical probaility that live load will not occur over the entire tributary area at the same time. If you are only supporting one level above ground I wouldn't be using live load reduction at all.