$6-70.$ The $9-$k truck exerts the wheel reactions shown on the deck of a girder bridge. Determine $($a$)$ the largest live shear it creates in the splice at $C,$ and $($b$)$ the largest moment it exerts in the splice. Assume the truck travels in either direction along the center of the deck, and therefore transfers half of the load shown in each of the two side girders. Assume the splice is a fixed connection and, like the girder, can support both shear and moment$\mathrm{.}6-70.$ The $9-$k truck exerts the wheel reactions shown on the deck of a girder bridge. Determine $($a$)$ the largest live shear it creates in the splice at $C,$ and $($b$)$ the largest moment it exerts in the splice. Assume the truck travels in either direction along the center of the deck, and therefore transfers half of the load shown in each of the two side girders. Assume the splice is a fixed connection and, like the girder, can support both shear and moment.

$9-7.$ Determine the vertical displacement of joint $A.$ Each bar is made of steel and has the cross$-$sectional area shown. Take $E=29({10}^3)$ ksi. Use the method of virtual work.

$*9-8.$ Solve Prob. $9-7$ using Castigliano's theorem.

Probs. $9-7/8$

Please explain all steps thoroughly