Determine the variation in the depth d of a cantilevered beam that supports a concentrated force P at its end so that it has a constant maximum bending stress \sigma_{\text {allow }} throughout its length. The beam has a constant width b_{0}.
Determine the variation in the depth d of a cantilevered beam that supports a concentrated force P at its end so that it has a constant maximum bending stress \sigma_{\text {allow }} throughout its length. The beam has a constant width b_{0}.
Section properties:
I=\frac{1}{12} b_{0} d^{3} ; \quad S=\frac{I}{c}=\frac{\frac{1}{12} b_{0} d^{3}}{\frac{d}{2}}=\frac{b_{0} d^{2}}{6}Maximum bending stress:
\sigma_{\text {allow }}=\frac{M}{S}=\frac{P x}{b_{0} \frac{d^{2}}{6}}=\frac{6 P x}{b_{0} d^{2}}\quad(1)At x=L, \quad d=h
\sigma_{\text {allow }}=\frac{6 P L}{b_{0} h^{2}}\quad(2)Equating Eqs (1) and (2),
\frac{6 P x}{b_{0} d^{2}}=\frac{6 P L}{b_{0} h^{2}}d=h \sqrt{\frac{x}{L}}