The Study Of Hydrodynamic Performance And Motion Response For Shore Floating Pier

The floating pier system is a bridge type structure which is made up of many piers and used to transport goods, facilities and vehicle between island and coast. Because the floating pier system is made up of multiple floating bodies, these bodies will produce the hydrodynamic interference. In addition, the connecting lines between adjacent piers and mooring system constitute a nonlinear system. The motion responses of floating pier are complex in the marine environment. Forecasting motion responses of floating pier accurately is significant to the constructionand the safety of operation.This paper is based on light-load floating pier and heavy-Load floating pier that are placed near an island in South Sea. SESAM software based on three dimensional potential flow theory is used to analyze the hydrodynamic performance and forecast the motion responses of floating pier. The major works and research achievements of this paper are as follows:(1) The domestic and overseas research progresses about the hydrodynamic performance and motion responses of multiple floating system are reviewed and summarized. The research method of mooring system is summarized. In addition, the research content and innovation points are introduced.(2) The ultimate principle of the study of hydrodynamic performance of multiple floating system is introduced. And the accuracy of Hydro D/Wadam module, a hydrodynamic analysis program in SESAM software, is validated. The results reveal that the results of Hydro D/Wadam module are similar to the results of theory and experiment of documents.(3) Hydro D/Wadam module of SESAM software is used to calculate the single pier and multiple piers of light-load floating pier in frequency domain and get the hydrodynamic coefficients of single pier under different wave directions. The factors such as the hydrodynamic interference of adjacent piers, the distance between adjacent piers and wave depth are concerned. The results show that the added mass and radiation damping of single pier are all larger than each pier of multiple piers in surge direction. With the increase of distance between adjacent piers, the added mass and radiation damping of pier a5 increase oscillatorily and the transfer function of the second order wave forces decreases oscillatorily. When wave depth is less than 10 m, with the increase of wave depth, the RAO and the first order wave force of pier a5 decrease in surge direction and they increase in heave direction. As wave depth is more than 10 m, the wave depth has less impact for hydrodynamic coefficients of pier a5.(4) SIMO module of SESAM software is used to calculate the single pier of Light-load floating pier under irregular waves in time domain. And FINE/MINE, viscidity fluid calculation software, is used to simulate attenuation test of single pier and obtain damping ratio. Through the comparison among two software, the influence of viscidity on the motion responses and mooring line forces is analyzed. SIMO module is further used to calculate multiple piers of Light-load floating pier under irregular waves in time domain and analyze the influences of the connecting lines and wave directions on the motion responses, mooring line forces and connecting line forces. The results reveal that for single pier, after adding critical damping in heave, roll and pitch directions, the motion responses of single pier decrease. The relative surge and heave motions between adjacent piers with the connecting lines are smaller than without the connecting lines. And the mooring line forces with the connecting lines are larger than without the connecting lines.When wave direction increases from 90° to 180°, the sway and heave motions of pier decrease. When wave direction is 105°, the relative surge motion between adjacent piers is the largest. Above all, the connecting linesbetween adjacent piers can decrease the relative motions. When placing the floating pier, wave direction should be 150°~180°.(5) SIMO module of SESAM software is used to calculate multiple piers of Heave-load floating pier in time domain and analyze the influences of significant wave height and the direction between wave and current on the motion responses, mooring line forces and connecting line forces.The results reveal that with the increase of significant wave height, the relative surge and heave motions between adjacent piers and the forces of mooring lines and connecting lines all increase. When wave direction increases from 90° to 180°, the motion responses of pier increase except roll.The relative sway motion between adjacent piers and the forces of mooring lines and connecting lines also increase, but the relative heave motion decreases.