Retaining Wall - Footing Width
Retaining Wall - Footing Width
(OP)
An architect specified a typical footing with a 3'-6" stemwall and now he wants an 8'-0" wall for a garage. Not a big deal, other than the footing is already poured.
I'm running through retaining wall designs to see just where this thing needs to be...see attached.
When I play with the height of the footing and vary it in depth, the deeper I go, the larger footing I need. This isn't making sense to me. The location of the soil and garage slab relative to the top of the wall are staying the same, however, when I run the calc with an 8ft wall, I need almost a 4ft footing. When I run the calc with basically a 5ft wall, I need a 2ft footing.
Any ideas? Other than the deeper you go the more pressure is on the footing. But in this case, that intuitively does not make sense to me.
I'm running through retaining wall designs to see just where this thing needs to be...see attached.
When I play with the height of the footing and vary it in depth, the deeper I go, the larger footing I need. This isn't making sense to me. The location of the soil and garage slab relative to the top of the wall are staying the same, however, when I run the calc with an 8ft wall, I need almost a 4ft footing. When I run the calc with basically a 5ft wall, I need a 2ft footing.
Any ideas? Other than the deeper you go the more pressure is on the footing. But in this case, that intuitively does not make sense to me.






RE: Retaining Wall - Footing Width
RE: Retaining Wall - Footing Width
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: Retaining Wall - Footing Width
Agreed, it just doesn't intuitively make sense to me. I tried my own retaining wall spreadsheets, ENERCALC, and RetainPro and got basically the same weird result with all of them. It isn't inherently different that a typical garage wall with a footing inside so it's kind of strange.
It makes me wonder if retaining wall design guidance is slightly flawed in that if you have a really deep footing but high soil heights on both sides it doesn't now what to do with it. Strange though.
RE: Retaining Wall - Footing Width
RE: Retaining Wall - Footing Width
In short, it's confusing me.
RE: Retaining Wall - Footing Width
RE: Retaining Wall - Footing Width
1) Modified sheet pile. Assume lateral restraint at the footing elevation and deal with overturning via resisting earth pressure on wall.
2) True retaining wall. Design as though the footing were at grade then shift footing down to desired level without changing anything else.
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: Retaining Wall - Footing Width
RE: Retaining Wall - Footing Width
Your solution 2) doesn't sound like you. More like me.
RE: Retaining Wall - Footing Width
Well, maybe there's hope for me turning a profit yet.
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: Retaining Wall - Footing Width
@jeffhed...you're saying the footings work fine at 24" width? To me, it makes sense that they work at a 24" width, but my dang programs are really confusing me...even my spreadsheet is confusing me on this one.
RE: Retaining Wall - Footing Width