CHAPTER 7 - Combined Bending and Direct Stress

Abstract

This chapter discusses the stress distribution across a beam, which within the elastic limit, subjected to transverse loads only, varies linearly from nothing at the neutral axis to a maximum tensile stress and to a maximum compressive stress at opposite outer fibers. The stress in the outer fibers is called the bending stress, and like direct stress, it is a normal stress—in the sense of being perpendicular to the cross-section. Bending stresses arise in these members as a result of the line of action of the longitudinal load not coinciding with the centroid of the cross-section. The longitudinal load may be eccentric to both principal axes, in which case, the total stress in any longitudinal fiber will be the algebraic sum of three stress components, namely, the direct stress, the bending stress caused by bending about one principal axis, and the bending stress caused by bending about the other principal axis.