Abstract: Under the action of design vacuum pressure and wind pressure, large storage tanks are prone to instability and failure. So reinforcing rings (or wind girders) are usually set to improve the stability of the oil tank walls. This paper focuses on comparing the instability formulas under external pressure for large storage tank walls in Chinese and American codes for design. Researches show that for atmospheric storage tanks, the basis for determining the instability of the tank walls under external pressure in Chinese and American codes is based on the theoretical formula for minimum critical pressure in short round cylinders. Shape deviation was considered in American design codes, while it was not consi-dered in domestic codes; for large storage tanks under external pressure, the wind pressure selection criteria for instability check formula of tank walls is inconsistent; both Chinese and American codes have not taken the factors of ground roughness (or landform category) and tank wall height into consideration. This paper proposes to take such factors into account when revising the relevant clauses in the codes.

Key words: large storage tank, reinforcing ring, wind load, vacuum, external pressure, stability, critical pressure