Research On Wave Load Calculation Of Truss Very Large Floating Structures

Very Large Floating Structures(VLFS)attracts widely attention all over the world,for its unique advantages in exploitation of marine resources and utilization of space.Truss Very Large Floating Structure is a new type of floating structures,and there is no mature theory and rules to guide its design.This paper mainly research on VLFS's hydroelastic response on wave with the combination of Time-Frequency hybrid STF and model of orthotropic plate,to provide guidance for structural design,then studies how to determine the structure design load reasonably and complete the analysis of strength assessment appropriately.Main contents are as follows:Firstly,the three-dimensional structure of VLFS was simplified as a equal stiffness two-dimensional "orthotropic plate",whose bending and vibration equation was derived,at the same time,the dry modal of displacement of the plate was obtained by software,and the Normalization Processing way is given,then the modal of shear and bending moment was gotten,which are the important inputs of the method of mode-superposition.Secondly,excluding mutual interference between buoys,two-dimensional potential theory in the frequency domain was used to build the boundary conditions for a single buoy,and whose coefficient of added mass and damping and the diffraction force were obtained with the source-sink distribution method.Thirdly,an efficient nonlinear method to forecast hydroelastic response of Truss VLFS was studied based on Time-Frequency hybrid STF.To consider the nonlinear of the force of the floating body suitably and the computational efficiency,the radiation force and diffraction force of buoys were gotten by linear interpolation,but Froude-Krylov force,hydrostatic buoyancy of buoys and the Morison force of small scale components were obtained on the instantaneous immerse hull,then the vibration equation of Truss VLFS was established,and whose solving format was studied by linear multistep.Take a 900 m Truss VLFS as an example,its hydroelastic response was calculated in time domain,and the result was compared with the experimental result.Finally,the method to predict the design load of Truss VLFS was studied,referring to CCS rules,the design load of structure was determined based on linear spectral analysis;and considering of the computer memory and computational efficiency,the simplified loading method was given out and the strength assessment of a Truss VLFS was accomplished.