The stress at a position A due to a load at position B may be determined by using Figure 5, which is derived from Westergaard. The displacement is taken as the distance from the point of maximum stress (position A) to the nearest edge of the adjacent load (at position B). If the adjacent load is at the edge of the slab, a percentage of the edge stress is considered. If the adjacent load is internal, a percentage of the internal stress is considered. The internal stress is also determined and the percentage to be used.
An edge load at position B induces a radial stress along the edge. However, an internal load at position B induces a radial and a tangential stress at position A. The negative portion of the radial stress curves means that the stress is tensile on top of the slab. This would therefore increase the corner stress but reduce the edge and internal stresses.