Sections $12\mathrm{.}1-12\mathrm{.}2$

For Problems $12\mathrm{.}1$ through $12\mathrm{.}17$ use the force method $($method of con$-$

sistent distortions$)$ to find the value of the redundant force indicated for

each truss. $E$ is constant for all members.

P$12\mathrm{.}1$ Find redundant $N_{BD}.$ Bar areas given in in ${?}^2$ are $AD=4,$

$BD=5,$ and $CD=4.($Ans: $N_{BD}=20\mathrm{.}08k)$