Practice Question: Bearing Pressure for an Eccentrically Loaded Foundation

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Solution

Width of Footing:
\[B=7 \ ft\]
Length of Footing: 
\[L=7 \ ft\]
Vertical Load:
\[P=100 \ k\]
Lateral Load:
\[V=15\ k\]
Distance from Base of Footing:
\[h=5 \ ft\]
Moment at Base of Footing:
\[M=V×h\]
\[M=15 \ k*5 \ ft=75 \ k⋅ft\]
Eccentricity:
\[e=M/P=(75 \ k⋅ft)/(100 \ k)\]
\[e=0.75 \ ft\]
Check that eccentricity is less than B/6:
\[e<B/6=\frac{7 \ ft}6=1.12 \ ft\]

Since eccentricity is less than B/6, minimum bearing pressure can be calculated as follows:
\[q_{max}= \frac{P}{BL} (1 + \frac{6e}{B})\]
\[q_{max}= \frac{100 \ k}{7 \ ft × 7 \ ft} (1+ \frac{6×0.75 \ ft}{7 \ ft})\]\[q_{max}=3.35 \ ksf\]

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