An Old Bridge Model

An old bridge can be modeled as a half-cylinder's shell. Consider an old bridge of radius r is placed on a ground. The ground is not perfectly horizontal, but it makes an angle θ with the horizontal. Then a mass M is placed on top of the bridge. See picture below.The bridge's mass can be ignored, compared to M. Assume that the ground is frictionless and the bridge is not glued on the ground. Determine the position of a point where the bridge is most likely to break!