TY - JOUR VL - 38 SP - 1417 A1 - Montasir, O.A. A1 - Kurian, V.J. KW - Numerical integrations; Quasi-static analysis; Second orders; Time domain; Truss spar KW - Drag; Dynamic response; Frequency domain analysis; MATLAB; Mooring; Offshore structures; Static analysis; Time domain analysis; Trusses KW - Spar platforms KW - dynamic response; floating structure; gas production; kinematics; numerical method; numerical model; offshore structure; oil production Y1 - 2011/// AV - none ID - scholars1928 N2 - Spar platform has been regarded as a competitive floating structure for deep and ultra deep water oil and gas production. In this paper, an efficient methodology has been developed to determine the slow motion responses of slender floating offshore structures due to wave forces. Based on this methodology, a MATLAB program named 'TRSPAR' was developed to predict the dynamic responses in time domain and it was used in this study to obtain the numerical results of a typical truss spar platform connected to sea bed using nine taut mooring lines. The difference frequency forces were calculated using the principles of the extension of Morison equation for an inclined cylinder and the wave kinematics were predicted using hyperbolic extrapolation. Mooring lines were modelled as nonlinear springs and their stiffness was obtained by conducting the static offset simulation. Because of the lack of detailed calculations in literature, most of the equations used were derived and presented in this paper. The effects of the different sources of the second order difference frequency forces were compared for inertia and drag forces in terms of response spectra. To validate the TRSPAR code, its results were compared to results of a typical truss spar model test. © 2011 Elsevier Ltd. All rights reserved. EP - 1429 UR - https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052258915&doi=10.1016%2fj.oceaneng.2011.07.007&partnerID=40&md5=bec0f28950e4986c6e52a2d5f6f56331 SN - 00298018 IS - 13 JF - Ocean Engineering TI - Effect of slowly varying drift forces on the motion characteristics of truss spar platforms N1 - cited By 17 ER -