Horizontal Loads from Surcharging Revisted

[DMWWEngr]

Previously I had asked the effect of an exterior surcharge loading (placed on a SOG) and what it would produce for horizontal loads on a basement wall. The last loading was a uniform loading and I got a lot of great comments.

As "luck" would have it my employer has changed there minds (again) and now I have to consider a different loading. Now it's a point load surcharge (SOG). I found a way to analyze it I'm just looking for experince to see if my solution SEEMS reasonable. The numbers I'm getting seem too small and I'ld like to hear from those of you with experience in this type of analysis.


Soil: Sand fill (placed 40 years ago)

First Wall....I have about a 10000lb load (applied to SOG). The load is 5' away from a 10' tall basement wall. I'm getting a total horizontal reaction of about 575 lbs (on a 1' strip of wall). Does that seem reasonable??

Second Wall...Same load, except slab is tied to this wall. Load is 3' away from a 5' tall retaining wall. I'm getting about 880 lbs of total horizontal reaction. Is that resonable??

To me the answers seem low but I have no feel for this type of analysis. TIA!! ---
Andrew

 

[ishvaaag]

If from the point load only you may be even conservative in the resultatn value since I got lower values from a rectangular area giving the 10000 lbf, from a OCE reference (Colegio Oficial de Arquitectos de Cataluña). But with the active or at rest push of the earths you need to get more total push per foot.

 

[dlew]

DMWWEngr,

The "Steel Sheet Piling design Manual", a 1969 publication of U.S.Steel, and "Foundation Analysis and Design", by Bowles, have the formulas to calculate the pressure distribution (both vertical and horizontal) of a point load.

If you do not have any of those publications, and want to see the formulas, I would be glad to e-mail a copy of that page.

AEF

 

[DMWWEngr]

dlew,

If you could send me an e-mail of one of the pages from EITHER of those books would be great. That would give me another check of my answers. My e-mail is: lundy@dmww.com

My current equations came from from "Principles of Foundation Engineering" by Das and the "Civil Engineering Reference Manual" by Lindeburg. These books had the same equations so it would be nice to see another equation (and better yet a different method to compare answers).

TIA!! ---
Andrew

 

[JAE]

We've developed a spreadsheet that solves a basic retaining wall pressure distribution due to an adjacent load on top. For your 10' basement wall, I got about 15 to 17 psf on the back of the wall. This is a maximum. What this means is that if you look down on the wall (bird's eye) the 15 to 17 psf would be maximum in line with the wall and diminishing on either side of the wall.

Don't know how the load diminishes.

 

[DMWWEngr]

Thanks everyone for the responses.

dlew, your e-mail was very helpful and gave me the exact equation I needed to verify my work.

JAE, my maximum stress is just above 25psf, which would indicate that my solution is less conservative then yours, that's good Probably just depends on which method is used to calculate it.

Thanks again everyone!! ---
Andrew