Practical formula for dimensioning a rectangular footing

The relationship among the flexural formulae and the vertical and rotational equilibrium of forces is correlated analytically to develop a simple and unique expression to determine the required minimum footing area under full compression. The current practice of estimating the size of footing in structural design usually employs the conventional iterative process initiated with the educated guess of designers. The presented formula is a practical algebraical solution as an alternative to the conventional trial and error method for estimating the minimum dimensions of a rectangular footing subjected to the combination of biaxial bending in both axes and vertical column load. The weight of footing and the lateral column loads are also included in the formula. It is straightforward in appearance and application. It is based on a linearly distributed surface pressure regime which disallows the tension to be developed in the footing/elastic-medium interface. It unifies the various formulations common to the field of structural engineering. Paper explains the validity of the new formula by comparing its results with those produced by classical methods. A simple design chart is also provided to determine the minimum dimensions of a rigid rectangular footing resting on elastic mass.