Primary Research Of A Telescopic Pile Positioning Facility For VLFS Deployed In Shallow Water

The Very large floating structure(VLFS)has a promising future with many advantages,such as large deck room and strong carrying capacity.The continuous length of a VLFS can be up to over two thousand meters,much longer than the deck length of the aircraft carrier.It can meet the requirement of most aircrafts' landings and taking-offs for runway length.In this paper,a telescopic pile positioning facility is proposed for VLFS deployed in shallow water,which has high positioning accuracy and is convenient and quick.Each single module(SMOD)of the VLFS is equipped with ten telescopic piles.The plugging and pulling processes can be realized by adjusting the module draught and the weight of the ballast water without the aid of auxiliary vessels.The main research contents of this paper is listed as follows:1.A suitable design of telescopic pile facility for the structural characteristic of the VLFS module is proposed.And the hydrodynamic loads of the SMOD in the operational and the survival conditions are obtained through the model test.2.Based on 3-D finite element method,the static bearing capacity calculation,dynamic response analyses and the plugging and pulling processes simulation of the telescopic pile facility are conducted by Abaqus software.And the yield and the buckling strengths of the telescopic pile are checked.The diameter and the penetration depth of the telescopic pile are preliminarily determined in the static bearing capacity calculation.In the dynamic response analyses,the time history displacement response of the SMOD under the hydrodynamic load of is investigated and the vertical precompression of the pile is determined.The results of the plugging and pulling processes simulation shows that these two processes both can be realized by the VLFS itself through adjusting the ballast water and the draft.According to relevant rules,the yield and the buckling strengths of the telescopic pile are checked and the results show that both have a large safety margin.3.The computational cost of the telescopic pile's lateral bearing capacity by 3-D FEM is quite high,thus a fast evaluation method for the capacity is proposed based on p-y curve method.The accuracy of this method is investigated.The lateral bearing capacities of the telescopic pile and the traditional uniform pile are compared.4.The load for the VLFS from the piles is considered in the motion equations of the VLFS by Matlab programming,to calculate the surge and sway of the VLFS under regular wave.And they are compared with the motions of the VLFS with mooring positioning facility.The results shows that the positioning ability of the pile positioning facility is much better than mooring.In this paper,the conceptual design and feasibility certification of the telescopic pile positioning facility are carried out.The conclusions obtained have certain reference value in the engineering application of this facility.