Building Design and Construction Handbook - Merritt - Ventech!

5.20 SECTION FIVE
decrease in stress. Thus, the materials exhibit plastic deformation. For materials
that do not have a well-defined yield point, the offset yield strength is used as a
measure of the beginning of plastic deformation.
The offset yield strength, or proof stress as it is sometimes referred to, is
defined as the unit stress corresponding to a permanent deformation, usually 0.01%
(0.0001 in/in) or 0.20% (0.002 in/in).
5.2.4 Constant Unit Stress
The simplest cases of stress and strain are those in which the unit stress and strain
are constant. Stresses due to an axial tension or compression load or a centrally
applied shearing force are examples; also an evenly applied bearing load. These
loading conditions are illustrated in Figs. 5.3 to 5.6.
For the axial tension and compression loadings, we take a section normal to the
centroidal axis (and to the applied forces). For the shearing load, the section is
taken along a plane of sliding. And for the bearing load, it is chosen through the
plane of contact between the two members.
FIGURE 5.3 Tension member. FIGURE 5.4 Compression member.
FIGURE 5.5 Bracket in shear. FIGURE 5.6 Bearing load and pressure.