Papers by Author: Chang Hwan Lee

Abstract: The effective breadth of a stiffened plate under bending was investigated. The design parameter of an effective breadth was used when a stiffened plate subjected to a lateral loading was considered. Due to the lateral loads there was shear transmission through the plate from the stiffener, which leads to a non-uniform longitudinal stress distribution across the plate width the effective breadth that takes into account a shear lag can be calculated by the simple beam theory. For a tanker, the existing effective breadth concept has been used when longitudinal stiffeners are fixed at adjacent web frames. However, the effective breadth of each classification’s formula can’t be applied to flexible support condition such as the one prevailing in Ro-Ro vessel. The effective breadth according to the rules of several classification societies was compared and a way to get an accurate analysis as suggested.

Abstract: Recently, most of fatigue cracks in ship structures are reported within a few years after delivery. This type of fatigue characteristics cannot be explained adequately by the S-N curve based on high cycle fatigue. Calculation results under critical loading conditions reveal that stress magnitude higher than three times the yield stress occurs at some critical locations. It shows the fatigue cracks are related to low cycle fatigue. But the existing recommended design procedures in maritime industry do not properly cover low cycle fatigue problems. This work represents the first step in an effort to develop a design code that addresses low cycle fatigue problems. Low cycle fatigue test for uniform round specimen made of base/weld metal and for cruciform welded joint are carried out under constant amplitude alternating load, controlled by strain. Strain-cycle curves for the base metal and weld joints show good agreement with published data as well as some code recommended design curves.