Axial Load and Bending Moment:

Given figure illustrated an isometric view of a rectangular section loaded along an axial load 'P', applied long its vertical axis from the centroid of the horizontal section. We say such as member is subjected to uniform compressive stress or direct compressive stress of magnitude P/A, here 'A' is the area of the horizontal cross-section.

(1)                           (2)                        (3)                               (4)

If the point of application of load P is displaced by a little distance 'e' from the axis, as illustrated in Figure (b), the distribution of stress in the member is significantly affected. (Here, 'e' is called as the eccentrically of loading.)

Figure (c) illustrated the elevation of the member is viewed from the face ABCD. Because of the eccentric load P, the member is bends or distorted, as illustrated in Figure (d). The left half portion & so the side AD shall be in tension & the right half and so the side BC shall be in compression, thus making the central axis of the member like neutral axis. As a result, with the eccentric load, the member is subjected to direct stress accompanied by the bending stress.