Practice Question: Eccentrically Loading Wall Footing - Full Contact

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Solution

Eccentricity: \(e = M/P = 9/18 = 0.5\ ft\). In order to determine whether the entire footing width is effective or not, the eccentricity must be

compared to \(B/6\), which is \(6/6 = 1\ ft\).

Since this eccentricity is less than \(B/6\), the resultant load fall within the middle third of the footing base. Maximum soil pressure is given by:

\[q_{max}=\frac{P}{BL}\left(1+\frac{6e}{B}\right)\]We are calculating the pressure on a wall footing, so consider unit length L = 1:

\[q_{max}=\frac{P}{B}\left(1+\frac{6e}{B}\right)=\frac{18}{6}\times (1+\frac{6\times 0.5}{6})\times 1000=4,500\ lb/ft^2\] 

The pressure noted above is per foot of wall.

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