| This paper is mainly based on the research of one internal sixth generationsemi-submersible platform which is under construction. AQWA is used forhydrodynamic calculation while ANSYS is for hydrodynamic. The yield and bucklingstrength of the semi-submersible platform are checked with the stress calculationresults derived from ANSYS according to DNV standards。Firstly, since the environmental loads of the semi-submersible platform aremainly from wave, the calculation theory and methodology of wave load areintroduced emphatically. The small amplitude wave theory is used, which is the mostmature and practical wave theory in ocean engineering. Morison’s equation anddiffraction/radiation theory are both used since the semi-submersible platformstructure comprises of both slender members and large volume structures. The forcesat the slender brace parts are from Morison’s equation, and the forces at the columnsand pontoons parts are from diffraction/radiation theory. The wave load cases aredetermined by the design wave method from the DNV standards, and thecharacteristic global hydrodynamic responses of the semi-submersible platform arecalculated by AQWA. Then the design waves under each load cases are applied to theplatform by AWWA-WAVE to calculate the hydrodynamic wave loads, which arethen exported as APDL.Secondly, the global structural finite element model of the semi-submersibleplatform was built by ANSYS according to related DNV standards. Load combinationconditions were applied, including wave load, variable load and fixed load. Fixedboundary condition recommended by DNV standards was used to avoid the rigidbody motion of the model. Then the static finite analysis was carried out, under theassumption of linear and small displacement.Finally, the structural yield strength is measured by comparing von Mises stresswith allowable stress, and the bulking strength of plate with continuous stiffenerswere checked according to DNV standards. |
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