Question: A vertical cylindrical steel tank, open at the top, is 4 m in diameter and 20 m high. The tank is filled with water. Determine the required wall thickness at the bottom section of the tank if the allowable tensile stress is 125 MPa. The plates are connected by butt welds of 70% efficiency. Add 3 mm to the required wall thickness to compensate for corrosion over the intended life of the structure.