The depicted structure is under consideration as the upper portion of a transmission-line tower and is supported at points F, G, H, and I. Point C is directly above the center of rectangle FGHI. Determine the force in member CD. The force is positive if in tension, negative if in compression.

The space between two 15-in.-long concentric cylinders is filled with glycerin (viscosity = 8.5 × 10-3 lb·s/ft2). the inner cylinder has a radius of 1 in. and the gap width between cylinders is 0.1 in. determine (a) the torque and (b) the power required to rotate the inner cylinder at 180 rev/min. the outer cylinder is fixed. assume the velocity distribution in the gap to be linear.