Shallow Fiundation Analysis

[steveyeung]

The well known general equation for the ultimate bearing capacity is for the circular, rectangular or strip foundation. Does anyone know how to modify it so it can be used for L-shape footing?

 

[jdonville]

steveyung,

I would think that you could approximate it as either a square or strip foundation. As long as the calculated FS was significantly greater than 3, there should be no issue. This is one of those times where professional judgement comes into play.

If you wanted to be conservative, assume a strip with the longest dimension of the ell as the footing length "L" and the width of that arm of the ell as "B".

Good Luck,

Jeff


Jeffrey T. Donville, PE
TTL Associates, Inc.

http://www.ttlassoc.com

 

[fndn]

If your L-shaped footing is of equal legs, then use that length as the "B" in the bearing calculations to come up with allowable baring pressures. Then you can use the entire area of the footing for settlement analysis.

If however you have unequal legs of L-shaped footings, we need to consider the centroid being off the footing, associated eccentricity and some of the foundation soils being in tension. Anyhow once you resolve them, you may approximate the area as triangular and use Boussinesq charts.

Good question.

 

[steveyeung]

Thank you for helpsss