In section 9, we study the effect of combined loadings and moments applied to cross sections. There is no new concept here, just an application of all what we learned in sections 5, 6 and 7. We will take real life examples of cross sections subjected to a combination of shear force, normal force, and bending moments. A step by step procedure on how to solve problems regarding combined loadings is provided.

In section 10, we discuss stress transformations that result from rotating an infinitesimal element with an initial state of stress. We will learn that normal stresses and shear stresses vary upon rotation. As a result, maximum normal stresses occur on a plane different from maximum-in-plane shear stresses. This explains the phenomenon of cracking and how it occurs. You will be able to apply the concepts of this chapter to predict the direction of cracking of a structure subjected to combined loadings, given that you have all the sufficient information.