The surface of an elastic body is loaded by a uniform stress of 2000 psf over an area 30 ft by 60 ft, which has coordinates (0, 0) at the center.
Find:
(a) the vertical stress at a depth of 10 ft below a corner of the loaded area.
(b) the vertical stress at a depth of 20 ft below the center of the loaded area.
(c) the vertical stress at a depth of 30 ft below a point which has coordinates 10 ft greater than those of the corner of the loaded area in the first quadrant (first quadrant is the one with positive x and y coordinates).