The concrete [E = 29 GPa] pier shown in Figure P5.28/29 is reinforced by four steel [E = 200 GPa] reinforcing rods. If the pier is subjected to an axial force of 670 kN, determine the required...

The concrete [E = 29 GPa] pier shown in Figure P5.28/29 is reinforced by four steel [E = 200 GPa] reinforcing rods. If the pier is subjected to an axial force of 670 kN, determine the required diameter D of each rod so that 20% of the total load is carried by the steel.