Structure’s Strength Induced by Intermittent Welding

Abstract

Welding is the most important of the ship building and assembling process. There are several welding of joining parts on the ship structure components that do not require watertightness such as joining of side longitudinal and the side plate of the ship. In areas that’s not required watertightness or oiltightness the structure components are joined by chain welding instead of continueous welding. The chain welding could become problem of weakness of structure’s integrities due to incontinuous of strength of structure and this could lead to structural failure. Classification rules make limitation of ranges of b/l ratio of chain welding, where b is length of welding step and l is welded length. This study aims to determine the relationship between the intermittent weld distance (chain welding) and the strength of the welded components. The strength calculation and analysis is carried out by using the finite element method by modeling a sample of chain welding of joining the side longitudinal and the side plate. Modelling and calculation is done by Ansys^TM software. It was found that the greater the ratio between the length of the welding step (b) and the length of weld (l) in the chain weld, the higher tensile stress of  the web frame, side longitudinal, and side plates proportionally (relatively linear). In case of b/l > 6.35, the tinsile stress of side longitudinal has passed the BKI allowable stress. The maximum stress, in case of continuous welding and in case of b/l = 5 of chain welding, increased about 68.51%, further incase of b/l = 6.35, the maximum stress increased about 23.34%. Actually the stress in case of b/l = 6.35, the maximum stress is still less then allowed stress stated by BKI, that mean that safety factor  according to BKI rules for ship  construction is high.