Column Load on Foundation Wall

[dazataz]

I've designed a residence with (2) center posts and (2) end posts on the end walls. The length of the Girder is 40' with 12.5' end spans.
My question is innoculous enough, the end columns carry 8700# LL & 3100# DL each. With a 18" wide footer on 1500 psi soil that equates to about 5.25 linear feet of footer.
What is the load path down through the foundation, is it a 45 degree angle each side of vertical?
Oh, and for fun the center posts carry about 30000# total DL+LL each on 4.25 ft sq piers.
Thanks

 

[DaveAtkins]

Basically, yes, you can assume the load spreads at a 45 degree angle through the foundation or basement wall to the strip footing. I suppose a more exact analysis would consider the foundation or basement wall to be a grade beam, with a uniform soil pressure pushing up and the column load pushing down.

DaveAtkins

 

[miecz]

I'd put in a couple of #5s under the posts, at the bottom of the wall.

 

[UcfSE]

Make sure you check that your loads are concentric on the portion of the footing below that you are using or else design the footing with an eccentric load. You could just make the footing a little wider like a spread footing at the column location and at the end posts.

 

[cap4000]

Check ACI Chapter 14 for an equivalent horizontal length of wall under a point load. 4 x the wall thickness + width of your base plate is standard for your case. Good Luck