A finite element model for numerical analysis of the dynamic response of mooring cables is presented. The model takes into account the elasticity of the cable, inertia forces, drag forces and frictional forces between the sea bottom and the cable. The model is capable of handling both two- and three-dimensional problems. The equations of motion are transformed to ordinary differential equations by means of the virtual work principle. The cable is decomposed into elements connected by nodes. For each node the discretized equations of motion are formulated with the displacement of the node as dependent variable. The equations are then solved by means of a simple explicit time integration method based on a central difference formula. The description of the model is considered complete enough to make an understanding of the construction of the model possible. Calculation examples dealing with a displacement excited mooring cable (chain) are presented where two- and three-dimensional calculations are compared. The calculation results show that the risk of obtaining slack, defined as negative strain, grows with increasing drag force. In a three-dimensional case a relatively long time integration is required to obtain a steady-state. A comparison is made with an analytical solution in the case of displacement excitations out of the plane of the cable as well as with calculation results presented in the literature.
Dynamic analysis of mooring cables
Dynamische Analyse von Kabeltauen
1983
39 Seiten, 16 Bilder, 4 Tabellen, 36 Quellen
Aufsatz (Konferenz)
Englisch
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