TABLE OF CONTENTS Tensile and compressive stresses are sometimes referred to also as normal stresses, because they act normal to the cross section. Under this concept, tensile stresses are considered as positive normal stresses and compressive stresses as negative.
Suppose a member of a structure is acted upon by forces in all directions. For convenience, let us establish a reference set of perpendicular coordinate x, y, and z axes. Now let us take at some point in the member a small cube with sides parallel to the coordinate axes. The notations commonly used for the components of stress acting on the sides of this element and the directions assumed as positive are shown in Fig. 5.7.
For example, for the sides of the element perpendicular to the z axis, the normal component of stress is denoted by f z. The shearing stress v is resolved into two components and requires two subscript letters for a complete description. The first letter indicates the direction of the normal to the plane under consideration. The second letter indicates the direction of the component of the stress. For the sides perpendicular to the z axis, the shear component in the x direction is labeled v zx and that in the y direction v zy.
If, for the small cube in Fig. 5.7,...
