Influence of Deckhouses and Superstructures on the Longitudinal Strength of Ships

Abstract

This paper deals with both analytical and experimental investigations into the effective length of deckhouses and superstructures as well as the necessary extent of the strengthening at bridge ends from view point of the longitudinal strength of ships. Based on the Bleich's method for analyzing the structural interaction of deckhouses with their main hull girders, a general criterion for the determination of the effective length is first discussed for the cases of actual ship scantlings. Furthermore, tests are carried out by using steel models in order to obtain the side stiffness and the deviation factors of the superstructures, taking into consideration the effect of the tapered-down side shell plating at bridge ends upon the structural interaction. The results of the study have revealed such conclusions that the effective length of the deckhouses and superstructures can be regarded as 0.25L and 0.15L respectively (i being equal to ship length), and the thickness of upper deck plating inside of bridge should be maintained within a distance of 0.05L from the ends equivalent to that of the strength deck, as specified in the Rules of the Ship Classification Society.