Soil Pressures and Value of "e"

[dhoward26]

I'm working on writing my own program (taking the parts of programs I like from people in my firm and adding my own flare) for shear wall foundation design. The question that I am having a hard time answering is this:

Calculating qmax and qmin is easy for eccentrically loaded foundations. What I'm struggling with is when e>L/6, how do you determine where there is "0" soil pressure on the footing? I need to figure out the location so I can finish my free body diagram!

Thank you,

D

 

[BAretired]

When e = L/6, the stress varies from 0 to 2*Average pressure or 2*P/AL.

When e > L/6, the effective length of the footing is reduced to, say B. The c.g. of loads will be located at B/3 from the stressed edge. Now, the stress will vary from 0 to 2*P/AB. The distance x = L - B.

BA

 

[dhoward26]

Thank you BA