Shallow Foundation Iii- Combined Footings And Mat Foundations.pdf |best|

Trapezoidal footings are employed when there is a significant difference in the loads carried by the columns being combined. For instance, if an exterior column carries a light load and an interior column carries a heavy load, a rectangular footing would require the resultant force to be far from the geometric center. A trapezoidal shape allows the wider end to be placed under the heavier load, balancing the system geometrically and physically.

(Soil as independent springs)