$5\mathrm{.}1-81$ Full Alternative Text $$

a$.$ Guess which component will contribute most to the vertical

displacement at $D$ : axial force in the cross$-$member, bending in

the cross$-$member, axial force in the post, or bending in the post.

b$.$ Estimate the vertical displacement at $D$ by considering the

cross$-$member to be cantilevered out from a fixed support $($i$.$e$.,$ no

rotation at $B).$ You can use the formulas inside the front cover of

this text along with superposition. Will this provide an upper

bound, a lower bound, or just an approximation for the actual

displacement? Justify your answer.

Prob. $5\mathrm{.}21$b

Figure $5\mathrm{.}21$b Full Alternative Text $$

c$.$ Calculate the vertical displacement at $D$ for the full structure

due to the self$-$weight of the structure and signals.

d$.$ Evaluate the displacement prediction using your results from

part $($b$).$

e$.$ Which contributed most to the displacement: axial force in the

cross$-$member, bending in the cross$-$member, axial force in the

post, or bending in the post? If you wanted to reduce the vertical

displacement at the end, what cross$-$sectional property do you

recommend be increased? Why that one?

f$.$ Comment on why your guess in part $($a$)$ was or was not close to

vour answer in part $($e$),$