A wood post of rectangular cross section (see figure) is constructed of 4 in. ( 6 in.

Question:

A wood post of rectangular cross section (see figure) is constructed of 4 in. ( 6 in. structural grade, Douglas fir lumber (Fc = 2,000 psi, E = 1,800,00 psi). The net cross-sectional dimensions of the post are b = 3.5 in. (see Appendix F).
Determine the allowable axial load Pallow for each of the following lengths: L = 5.0 ft, and 10.0 ft.