of of

The vertical stress at point P located at a depth z below point 0 due to a surcharge q per unit area of ABCD is equal to the algebraic sum of the vertical stresses produced by loading each one of the areas listed on the right hand side of the Eq. (6.16) with q per unit of area. If II to 14 are the influence factors of each of these areas, the total vertical stress is

(6.17)

Example 6.5 ABCD is a raft foundation of a multi-story building [Fig. 6. 9(b)] wherein AB = 65.6 ft, and Be = 39.6 ft. The uniformly distributed load q over the raft is 7310 Ib/ft2• Determine 0' at a depth of

, z 19.7 ft below point 0 [Fig. 6.9(b)] wherein AAI = 13.12 ft andAIO = 19.68 ft. Use Fig. 6.8.