Application of Elastic-Plastic Hinge Method to Uplift Behavior of Flat-Bottom of Cylindrical Tank subject to Seismic Excitation (3rd Report)

Oil storage tanks are usually constructed directly on tank foundations without anchors. In such a flat-bottom cylindrical tank subject to seismic horizontal force, a part of the bottom plate adjacent to the shell will be lifted off the tank foundation by the overturning moment, and excessive plastic strain cyclically occurs at the toe of the inside fillet weld of the shell-to-bottom joint. In the previous papers, expanding the basic theory of Elastic-Plastic Hinge Method (E.P.H.M.) to uplift behavior of flat-bottom of cylindrical tank in consideration of the elastic deformation of the tank sidewall, and calculations are carried out for a 32,000kl oil storage tank of high strength steel SPV490Q. In this paper, the equilibrium equation in consideration of 2 elastic-plastic hinges of uplifted bottom plate is formulated, and analytically calculations are carried out for a 18,200kl oil storage tank of middle strength steel SM490C. Then, the effectiveness of this method is shown by comparing it with results of FEM non-linear analysis.