Loads on Vertical Pile Groups

For a rigid foundation supported by a group of vertical piles of variable stiffness and general layout, simple formulas were derived by matrix algebra which (a) produce the pile forces caused by vertical loads or moments only, without prior computation of a pile gravity center and principal axes with corresponding load transformation (only one coordinate system is used throughout); (b) produce the constants for the (plane) influence surface of the load of a general pile; and (c) determine, by the zero-lines of the influence surfaces, the Kern-area of the pile group within which the vertical load has to be located to produce compression in all of the piles.