ABSTRACT:

This paper presents a quasi-static mooring analysis model to assist the designer in predicting the performance of a jetty mooring system at exposed locations. The analytical model is based on the quasi-static method using the load incremental method and allows nonlinear elastic behavior of the multisegmented mooring lines. This model will aid the designer to provide quick optimal results of ship movements and mooring line and fender reactions for various alternative mooring arrangements. Results of computer programs were compared with the model test results of ballasted 250,000 DWT tanker moored to an offshore jetty. From the results it may be concluded that the quasi-static analysis model developed in this study could be used to determine the vessel excursions, mooring line forces and fender reactions.

1. INTRODUCTION

For the design of the mooring system of a ship moored at locations exposed to wind, current and waves, it is essential to have the knowledge of the method to assist the designer in predicting the performance of the mooring system. This paper utilizes a quasi-static mooring analysis model (Chernjawski (1980)*) to find more suitable and safer mooring system by means of mooring lines and fenders under severe weather conditions. In general, the design of an appropriate mooring system depends on water depth, ship size, allowable motions of the moored ship and the external forces. Whatever type of mooring arrangement is selected, the size and number of mooring lines will depend on the external forces present such as wind, current and waves. The quasi-static method assumes the wind and current forces to be static and the wave induced forces to be dynamic. In addition, the wave induced force can be decomposed into two parts: the first order high frequency wave forces and the second order mean and slowly varying wave drift forces.

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