| In April2006, the International Association of Classification Societies (IACS) issued two separated Common Structural Rules (CSR), one for double-hull oil tankers and another one for bulk carriers. However, these two rules have certain degrees of technical differences in areas like load, prescriptive rule requirement, finite element analysis, bulking strength requirement, fatigue strength requirement, etc. In order to eliminate these technical differences, IACS has started to set up specialized working groups to conduct research in CSR since2008. According to the requirements of the Goal Based Standards of shipbuilding (GBS) of the International Maritime Organization (IMO), IACS has constructed the Harmonized Common Structural Rules (HCSR), and issued a draft of the rules for industry discussion on1st July,2012.As for the structural strength requirements, the new HCSR is not lower than CSR. Compared to CSR, HCSR not only has adjusted the technical differences but also added supplementary content in areas like residual strength, structural redundancy and human factors analysis, all according to the GBS requirements. This makes HCSR more comprehensive in rules and lays greater emphasis on the role of computational analysis.Direct strength analysis is one of the important ways of evaluating the structural strength of the ship, which attracts more and more industry attention. In CSR and HCSR, direct strength analysis occupies an important position. Compared to the CSR, HCSR extends a range of requirements for direct strength analysis, including not only requires midship cargo hold region, but also forward cargo hold region, after cargo hold region, formost hold and aftmost cargo hold. As a whole, except aft peak tanks and superstructure, the entire hull structure requires direct strength analysis, providing evidence for the importance of direct strength analysis.Hull girder loads are important aspects of the direct strength analysis of HCSR. It composes the entire loading system along with cargo pressure, hydrodynamic pressure, ship structural steel weight and other local load. We should be able to correctly consider the hull girder loads related to the success or failure of direct strength analysis. In cargo hold structural strength analysis, the purpose of considering the hull girder loads are to evaluate the load impact of outside the target cargo hold. In HCSR, it is ensured that the target position of the hull girder load reaches the target value by adjusting the hull girder loads.The main research component of this thesis is in hull girder loads of the direct strength analysis of HCSR. Within the research, the HCSR content is further sorted and specialized. Several key points have been explored and studied including the hull girder loads impact of the longitudinal nodal forces, the applied position of torsional moment adjustment values, the reference position of torsional moment calculation and the necessary of torsional moment adjustment.Through this thesis work, the author obtained comprehensive understanding of the direct strength analysis of HCSR and hull girder loads of the direct strength analysis. Last but not least, this thesis covers some encouraging research outcomes to the existing issues, which can provide a reference for future research and development of rules. |
