Example $10\mathrm{.}5$: The load from a continuous footing of $1\mathrm{.}8$ metres width, which may be consid$-$

ered to be a strip load of considerable length, is $180k\frac{N}{m^2}.$ Determine the maximum principal

stress at $1\mathrm{.}2$ metres depth below the footing, if the point lies $($i$)$ directly below the centre of the

footing, $($ii$)$ directly below the edge of the footing, and $($iii$)0\mathrm{.}6$ m away from the edge of the

footing. What is the maximum shear stress at each of these points? What is the absolute

maximum shear stress and at what depth will it occur directly below the middle of the foot$-$

ing?