Research On Collision Force Acted By Sway Fender Of Barge During Float-Over Installation Based On Numerical And Field Measurement Method

As marine petroleum exploitation marching toward deep sea,topsides of ocean platforms have a development tendency of larger and larger.Floatover installation method of topsides earns popularity in industries by virtue of heavier installation weight,lower cost and shorter operation cycle.Most inshore oil production platforms in China adopt jacket structural style.It is very important to carry out research on float-over installation of topsides of jacket platforms.This paper investigated collision force acted on jacket legs by sway fenders of barge in the float-over project of LuFeng 7-2 topside.The research was carried out based on strain data of the jacket legs obtained by field measurement during docking stages,combining with method of numerical computation and simulation.Monitoring and calculation method of horizontal collision force acted on Leg Mating Units was introduced at the last part.Main contents in this paper are: designed a system monitoring strains of jacket legs during docking stages of float-over installation and carried out real time measurement;monitored wind,wave,current and barge motions during the float-over installation;restored the collision force acted on jacket legs based on strain data of the jacket legs and yaw angle of the barge acquired by field measurement with numerical method,and calculated the force without yaw angle of the barge and analyzed it;carried out numerical simulation of the docking stages in float-over installation with environmental conditions adopting field measurement results,and compared the collision force of simulation with that calculated based on filed measured strain data;investigated relationship between docking gaps and maximum collision force;monitored strains of Leg Mating Units and calculated the horizontal force acted on Leg Mating Units.Conclusions are summarized as follows: the strain monitoring system can measure strains of jacket legs precisely and send the data to the barge accurately and steadily;maximum collision force during docking stages calculated based on field measured strain data was smaller than design load of the sway fender,the method used in restoring the collision force was comparatively reasonable.;there are some differences between results of numerical simulation and calculation based on field measured data,that was because neglect of docking velocity and other factors;numerical simulation results were lower than field measurement results at some situation,so more conditions that barge was at other equilibrium positions should be calculated at docking stages in numerical simulations;there is no specific rule between docking gaps and maximum collision force;maximum values of the collision force acted on Leg Mating Units were lower than the design load in the monitoring period.