Research On Structural Forms For Corrugated Bulkhead Of Large Oil Tanker Based On Common Structural Rules

Oil is the major energy source of our world today. Oil tanker has become the main transport vessel due to its features of big cargo capacity, fixed routes, high efficiency of cargo-handling, good economic returns and other factors. Oil tankers are becoming larger and larger and are being developed in the direction of super large-scale. The submission of the draft standard on the COTCPS means higher requirements to the work of coating. The introduction of the CSR has led to increasing of the lightweight and corresponding increasing of construction costs. The use of the corrugated bulkheads on large oil tankers and the optimization and analysis on the structure of the corrugated bulkheads based on the CSR are very important to the reducing of the coating area, the efficiency of tank washing and cleaning, reasonable control of the tank capacity and improvement of the mechanical characteristics. So it has important practical significance and good value to the design application for full scale ships.The background of this article is a research project of the Marine Design & Research Institute of China. The article developed four designs of corrugated bulkheads with different types of upper stool. After stress assessment based on the CSR, fuzzy comprehensive evaluation was done to the major design criteria of structural performance, economic performance and workmanship. The best is the corrugated bulkhead without upper stool, and the second is the form with single gradient-wall upper stool. By taking into account the actual design, the further research optimized the obliquity of the single gradient-wall of the transverse upper stool.The main works of this article are listed as follows:(1) The article did a design calculation to two types of bulkheads of the cargo section of the tanker under same structural strength, i.e. the flat panel and corrugated bulkhead, and compared the difference of their coating areas. At the same time, the article analyzed different types of bulkhead structures of the classic oil tankers developed worldwide in the past 20 years, and did a comprehensive study on the future application of the corrugated bulkhead on oil tankers and state-of-the-art of the design optimization and application of this structure in worldwide shipbuilding circles.(2) Based on the study on the general principles and requirements of CSR, and its methods of structure design and strength evaluation, by taking the 76 000DWT product/ crude oil Panamax tanker as the study object and by developing the design from rules requirements, the article developed four designs of corrugated bulkheads with different types of upper stool such as single gradient-wall upper stool, double straight-wall upper stool, double lower straight-wall upper stool and the transverse bulkheads with non-upper stool. The article also did design optimization to the sizing of the corrugations for the bulkheads with double straight-wall upper stool and transverse bulkheads without upper stool. As the result, the article presented the dimension for the major structural components of six bulkhead designs created based on above four structure styles.(3) After completing above analysis and design development, the article established FE models covering three cargo tank lengths and applied the loads to do the calculation to the yield strength and buckling strength of the major components of the corrugated bulkheads and stools containing longitudinal and transverse bulkheads for four above-mentioned bulkhead structures. Under the premise of meeting the regulatory requirements, fuzzy comprehensive evaluation was done to the major design criteria of largest tank capacity, minimum lightweight, minimum stress and most easy for construction.(4) According to the result of fuzzy comprehensive evaluation, design optimization and analysis were done to the obliquity of the single gradient-wall of the transverse upper stool. The results proved that with the height of the upper stool remain unchanged but after changing the obliquity to study its effect to the bulkhead structure. By taking into account the actual design and construction effect and stress distribution, when the angle is changed, it was concluded the better angle range. At this point, the bulkhead has good mechanical characteristics and is friendly for practical construction.