This calculator will analysis the rigid rectangular spread footings with up to 8 total piers, and for either uniaxial or biaxial resultant eccentricities. Overturning sliding, and uplift stability checks are made when applicable, and resulting gross soil bearing pressures at the four (4) corners of the footing are calculated. The maximum net soil bearing pressure is also determined.
Calculations assumes that the spread footing is in fact "rigid", so that the bearing pressure is distributed linearly on a homogeneous soil. (Note: the actual footing is generally not "rigid", nor is the pressure beaneth it distributed linearly. However, it has been found that solutions using the assumed "rigid" concept are adequate and generally result in a conservative design.)
A specified permissible value for the factor of safety against overturning. However, a minimum value of 1.5 to 2.0 is suggested, based upon the particular conditions.