Planning and Design of Fixed-Berth Structures for 300,000- to 500,000-DWT Tankers
Authors: Toppler J.F. , Weersma J. 
Published: December 2007

To accommodate tankers in the 300,000- to 500,000-DWT size range, fixed-berth structures must be something special. Although the basic designing problems have been largely solved, much could be gained by systematically collecting and evaluating and mooring loads.

Introduction

As a result of the Transshipment Terminal concept, the first two facilities to accommodate tankers of 300,000 DWT were conceived in the early 1960's. In this paper we shall refer to the planning and design of these facilities and to some of the subsequent installations designed for tankers up to 500,000 DWT

Development of Tankers

The phenomenal increase of tanker size in the 1960's required a complete re-evaluation of the design of facilities to handle the new generation of vessels. The largest tanker in service in 1960 was 100,000 DWT, in 1970, 326,000 DWT, and in 1973, 500,000 DWT. Therefore, the size of tankers has increased five times between 1960 and 1973. To meet these new requirements a different philosophy concerning the design of terminals had to be developed. Another aspect to be considered is the spectacular increase in the number of these large tankers. It is interesting to note the tendency in the distribution of vessels in the period from mid-1969 until the end of 1972. Table 1 shows that in these 31/2 years the total number of tankers existing and on order in the range of 200,000 to 250,000 DWT increased by nearly 100 percent and for those in the range of 250,000 to 300,000 DWT the increase was nearly fivefold. Vessels larger than 300,000 DWT increased more than tenfold, and that includes four vessels larger than 450,000 DWT. The planning, engineering, and construction of berthing facilities nominally require 3 to 5 years. However, berths must be planned 15 to 20 years ahead; consequently, the distribution of ships to be accommodated must be carefully considered. While berths are to be designed to cater to the maximum-size vessel that is expected to call, due consideration must also be given to the most common size of vessel that will use the facility. This aspect is especially important for establishing the layout of the facility, loading rates, mechanical installations, and design criteria for berthing and mooring structures. Most of the present-generation tankers are in the range of 200,000 to 300,000 DWT, the most prominent group being the 250,000 to 275,000 DWT. prominent group being the 250,000 to 275,000 DWT. Since these vessels will be in operation for the next 15 to 20 years and since their number is great compared with the number of vessels in the 300,000-DWT class and larger, it may be assumed that this generation of tankers will remain the most prominent for at least the next decade. Therefore most new facilities will have to be designed for a minimum vessel size of 300,000 DWT. The increase in size of vessels is best illustrated by the comparison of physical dimensions. Table 2 and Fig. I give a summary of the dimensions and principal characteristics of the average tanker up to principal characteristics of the average tanker up to 500,000 DWT. (Note that there is a considerable scatter in the physical dimensions for a given size of vessel.)

JPT

P. 764