See: see: https://www.physicsforums.com/showthread.php?p=2314761 1. The problem statement, all variables and given/known data Consider a hollow beam of length L where a force F is applied in compression at the bottom of the beam. (An off-center axial point load.) Determine the stress at the top and bottom of the beam at x=L/2. The inside radius is r1, the outside radius is r2. 2. Relevant equations There is both compressive and bending stress in the beam. The compressive stress is -F/A and the bending stress is My/I, where F is the force, A is the cross sectional area, M is the applied bending force, y is the distance to the neutral axis, and I is the second moment of area. 3. The attempt at a solution Applying this force is the same as a pure bending moment, except you gain additional compressive stress. Thus, at all points in the beam, the stress is: S = -F/A + My/I Most of the beam will be in compression, and a smaller part of the beam will be in tension. M is a constant over the whole beam, not a function of x, and is equal to F*r2/2. y, however, is a bit tricker to solve. By definition, y is the distance to the neutral axis. In other words, the stress should be zero at y=0. So, I set the stress S = 0 = -F/A + M(y-y0)/I where y0 = distance from the midpoint to the shifted neutral axis due to compressive stress and solved for y0 (which is -1/2r2 * ((r2^4 - r1^4)/(r2^2 - r1^2))) So now I have: S = -F/A + F*r2*c/2I where c = y-y0 and y0 is a constant and y is the distance from the midpoint of the beam Basically I have moved my coordinate system from the midpoint of the beam to some other point, so "c" (y-y0) is nonzero at zero stress. Thoughts?