The figure shows a rectangular member OB, made from -in-thick aluminum plate, pinned to the ground at one end, and supported by a -in-diameter round steel rod that is formed into an arc and pinned to...

The figure shows a rectangular member OB, made from -in-thick aluminum plate, pinned to the ground at one end, and supported by a -in-diameter round steel rod that is formed into an arc and pinned to the ground at C. A load of 100 lbf is applied at B. Use Castigliano's theorem to determine the vertical deflection at point B. Justify any choices to neglect any components of strain energy.