Problem $5\mathrm{.}4.$B $($from text$)$

A simple beam of Hem Fir, select structural grade, has a span of $18ft$ with two concentrated

loads of $4,000$ lbs$.$ each placed at the third points of the span. Neglect the beam's own weight.

a$)$ Compute the maximum bending moment $($hint: you can use Figure $3\mathrm{.}18$ from text$).$

b$)$ Use the tables in Chapter $5$ to determine the allowable bending stress $(F_b).$

c$)$ Assuming $F_b=F_b^{\text{'}}($no correction factors are needed$)$ compute the required section

modulus $($S$).$ Use this value $($and Table A$\mathrm{.}8)$ to select the size of the beam with the

least cross$-$sectional area.