Study On The Influence Of Long-period Waves On Vessel Mooring Stability

In recent years, coupled with the requirements of larger ships, the depletion of China’s shorelines which have extraordinary natural conditions for port construction has driven an increasing number of ports to be built in the open deep water far away from coastlines. In addition, China’s port construction companies are speeding up their international pace, more and more designs and constructions of overseas port projects are undertaken by Chinese enterprises. These offshore deepwater ports, at the same time, are facing more harsh natural conditions than those traditional nearshore ports. In particular, long-period waves coming from open sea can lead to substantial movements of mooring vessels. For many times, a number of domestic and overseas ports encountered mooring lines breakage that undermines the normal operation and security of the terminals. Therefore, how do long-period waves influence the ship mooring stability becomes a crucial issue. Since the mooring problem is a complex interaction problem of a mooring system, buffer system and berthing structure, most previous studies on it were carried out through model tests of specific engineering projects, and many research results were obtained about vessel movement, mooring line force as well as impact energy under waves action. However, due to the limitation of the real engineering backgrounds, the research on the influence of long-period waves (period above10seconds) on mooring vessel still lacks at present.On the basis of the literature review of past studies on mooring line force, vessel motions and impact energy of a mooring ship under waves, as well as the model test data of a bulk carrier terminal in Dalian, with the employ of the mooring analyzing software OPTIMOOR, a mathematical model of a mooring bulk carrier was established to study the response of the vessel movement and mooring line force, under different wave actions which varies by wave period (5to25seconds), wave height and wave direction. This paper mainly focus on the response of mooring ship movement and mooring line force with the varying wave period, especially under the long-period waves action, and in order to provides a reference for the design and management of open sea terminals greatly affected by (long-period) waves.