Figure 1 shows a closed tank which is completely filled with water and connected to a Mercury manometer which can be used to determine the water pressure inside the tank. The prismatic shaped gate ABCDE (shaded) prevents the water from escaping. The gate is 3 m wide (into the page) and is supported at D by a pin support and at E by the strut EFG. It can be assumed that there is no force interaction between the gate and the wall of the tank at Point A or with the floor of the tank at Point C. The strut EFG is made from steel rectangular hollow section (RHS): E = 200,000 MPa, oy = 350 MPa. The strut is pinned at each end (E and G) for buckling about x and axes and is laterally restrained at its mid-length (F) in the x direction only (affects buckling about the y axis). If the height of mercury in the manometer is 3 m, using the attached table (Figure 2) determine the lightest (kg/m) RHS section size for the strut EFG that will prevent the strut from failing and releasing the water. Which mode of failure (squashing, buckling about X or buckling about Y) governs the axial compressive capacity of the strut EFG? Neglect the self weight of the gate. Mercury. 3 m pg = 133420 N/m' Water: pg = 9810 N/m' 1.5m 1.5m 1.5m 3 m G 2 m D = 1.5m Gate ABCDE is 3 m wide into the page