Results from Stress Measurements of the Structure Supporting the 600 Ton Heavy Derrick

Abstract

Heavy derricker "ATLAS MARU" was delivered to Mitsui O.S.K. Line, Ltd. on March 20th, 1978 by Kobe Shipyard & Engine works of Mitsbishi Heavy Industry, Ltd. employing the authors. The heavy derrick on ATLAS MARU is a Kawasaki guyless omnirange rotary type with 600ton lifting capacity. This capacity is the largest of heavy derrickers in the world. But, because of the limitation of space design, the depth of the tower mast of the heavy derrick under the upper deck was obliged to be smaller than that of the 450ton heavy derrick which had the largest lifting capacity of the same type heavy derricks. Authors carried out the strength analysis by FEM and stress measurements on the base structure of the heavy derrick. Because of good correspondence between both results, it was confirmed that the winch platform contributes to support the heavy derrick, and the simplified method to calculate the strength of the base structure was considered. There was fairly good correspondence between measuremonts and results of simplified method. Accordingly, this method will be available to estimate the scantlings of the base structure of heavy derrick which depend on planning depth of the tower mast under the upper deck.