Alp – Bending moment and shear force diagrams

Consider a pile with applied displacements only.  If the curvature of the profile of applied soil displacements varies down the pile, sometimes describing a concave profile and sometimes a convex profile, then the resulting bending moments and shear forces will have alternating signs in a “zig-zag” fashion down the length of the pile.

However if the applied soil displacements’ profile were always of convex curvature, then there would be a more consistent sign in bending moments and shear forces.  Such a profile of applied soil displacements is shown in Figure 1 in red, compared with a profile that varies between concave and covex, as shown in blue.  At first glance the profiles may appear similar, but while the magnitudes of displacements are not wholly dissimilar their local curvatures are very different.

Figure 1

Figure 2, from Oasys Alp, shows the bending moment and shear force diagrams arising from the applied displacements described by the blue profile of Figure 1…

Figure 2

…whereas the smoother profile of bending moments and shear forces in Figure 3 results from the consistently convex series of applied displacements described by the red profile of Figure 1.

Figure 3