Optimization Research On A Semi-submersible Pipelaying Crane Vessel

With the exploitation of oceanic hydrocarbon resources and the development of large offshore engineering,pipelaying crane vessels have been one of important engineering ships.The progress is being made towards large-scale and professionalization gradually.Large semi-submersible pipelaying crane vessels(SSCV)have drawn more attention during last decades because of many operating characteristics,such as great lifting weight,high stability requirement,strong adaptability to environment and high level of dynamic positioning.Large semi-submersible pipelaying crane vessels always consist of pontoons,columns and upper platforms.Among these structures,columns are the part which makes pontoons and upper platforms connected.There are two effects of columns.One is to support the loading from deck and the equipment,the other is to provide enough area of water plane to ensure the stability and variable loading of platforms.Design experience and research analysis show that,the choice of vessel shape,the scale,position and quantity of pontoons and columns are decided not only by the arrangement of cabins and structural strength,but also primarily by the floating condition,stability,hydrodynamic performance and environmental forces which have effect on the security,effective operation efficiency and economic consideration directly.Therefore,it's necessary to conduct an optimization design on vessel.In this paper,the research object is a semi-submersible pipelaying crane vessel in study.Optimization design is conducted to its structural configuration of global platform,with an emphasis on two kinds of columns' arrangement schemes: eight-columns-type and ten-columns-type.A comparison is made on structural strength,stability in lifting cases,hydrodynamic performance and ability of dynamic positioning.The final optimization solution is obtained through the computation of hydrodynamic performance by HydroSTAR whose results are referred to those from model tests.At last,the verification is made for the performance of the optimization solution to provide reference to engineering applications.