Dynamic response analysis of offshore cable structures under wave forces

Research Project

Project/Area Number	02650328
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	土木構造
Research Institution	Setsunan University, Faculty of Technology
Principal Investigator	NAMITA Yoshio Setsunam Univ., Civil Engineering, Prof., 工学部・土木工学科, 教授 (30198379)
Co-Investigator(Kenkyū-buntansha)	HARAGI Hirokazu ditto, Assist.Prof., 工学部・土木工学科, 助教授 (00123612)
Project Period (FY)	1990 – 1992
Project Status	Completed (Fiscal Year 1992)
Budget Amount *help	¥1,800,000 (Direct Cost: ¥1,800,000) Fiscal Year 1992: ¥300,000 (Direct Cost: ¥300,000) Fiscal Year 1991: ¥400,000 (Direct Cost: ¥400,000) Fiscal Year 1990: ¥1,100,000 (Direct Cost: ¥1,100,000)
Keywords	offshore structure / cable / large deformation / time history / curved finite element / ケ-ブル構造 / 潮流・波浪応答解析 / 3節点曲線有限要素 / 3節点曲線要素
Research Abstract	A method of dynamic response analysis of marine structural cables, which are used for the purpose of mooring, staying or guying the offshore structures under the action of tidal current and/or wave forces, is presented. Equations of motion of cable members under the action of fluid forces are derived by employing three node curvilinear finite elements which were formulated by the authors in the past. Truss members, rigid frame members and floating bodies, which are to be connected with marine cables, are also analyzed in the form of finite element formulation. Computer program based on the above theory is developed for practical use. The completed program provides three main functions, i.e., (i) three dimensional statics with large deformation, (ii) Eigenvalue analysis and (iii) time history analysis of dynamic response. Further, the numerical results of time history analysis can be displayed graphically in an automatic process, which makes it easy to read the results of computation. The accuracy of numerical solutions and convergence of nonlinear iteration were fully checked and the practicability of the program was cofirmed after many case studies. Further improvement is intended for the better usage of the program. Numerical examples are shown by setting up cable models which are supposed to be ones utilized in practical offshore structures. Numerical results obtained in this research as to large deformation of cables under the action of statical tidal current and dynamic response of cables subject to time-varying wave forces show fundamental behavior of staying or mooring cables of offshore structures.