Planning and Design of Fixed Berth Structures For 300,000 to 500,000 DWT Tankers

ABSTRACT The planning and design of berths for mammoth tankers completed during the past few years and now under construction, is reviewed. All these structures are of the fixed type and accommodate tankers larger than 300,000 DWT. The range of ships to be accommodated predicates the number and spacing of the main structural components and influences the cost of the structure. A tendency of increasing berthing energy capacity for a given size vessel is illustrated. The evaluation of mooring loads is commented on. The cost of the structure as a proportion of the total cost of the installation has significantly changed for the recent projects, due to the increased loading rates and more extensive mechanical provisions. INTRODUCTION In the early sixties the first two facilities for tankers of 300,000 DWT were conceived. At that time the concept of transshipment terminals using very large vessels to shuttle between the Persian Gulf and the transshipment terminal was established. This concept set the stage for the development of a new generation of tankers, namely the mammoth tankers or as they are also known, the Bantry class tankers. During the next few years the concept of transshipment was modified to include shipping directly to receiving ports. This in turn, prompted the construction of more of these vessels and the development of even larger tankers. In this paper reference is made to the planning and design of some of these facilities, starting with Bantry Bay and Kuwait. No attempt was made to give a detailed description of any of the projects, because they have been described in technical publications or will be as soon as the construction is completed. An attempt was made however, to highlight aspects of the planning and design which require special attention. Undoubtedly the design philosophy has changed somewhat since the first of these facilities were built. These changes were the result of the experience gained from the first projects and the data collected from investigations and tests. The two main design aspects are berthing energies and mooring loads, both of which need further study and experimentation. A brief summary of some of the approaches to establish berthing energy is included, while for mooring loads the necessity of model testing is advocated. Mention is also made of the high loading rates and the associated installations. The cost ratio between the main components of the structure and the mechanical installation is given, comparing the first projects against the recent installations. The basic layouts of several facilities which Harris planned and designed during the past years are used to illustrate how various solutions were found for facilities to serve 300,000 - 500,000 DWT tankers. DEVELOPMENT OF TANKERS The phenomenal increase of tanker size in the 19601 s required a complete reevaluation of the design of facilities to handle the new generation vessels. The largest tanker in service in 1960 was 100,000 DWT, in 1970, 326,000 DWT and in 1973 it will be 500,000 DWT.