Dynamic analysis models of tension leg platforms

Journal Article · Wed Sep 01 00:00:00 EDT 1982 · J. Energy Resour. Technol.; (United States)

DOI:https://doi.org/10.1115/1.3230406· OSTI ID:6274761

Jefferys, E R; Patel, M H

Conventional analysis of tension leg platform structures yields natural frequencies which are well separated from wave excitation frequencies. However, the results presented here show that the tethers can have lateral resonant frequencies in the wave frequency range if the platform is deployed in deep water. Analysis which ignores the lateral tether dynamics gives reasonable estimates of platform motions but can seriously underestimate tether displacements. It is usually assumed that tether tension does not vary with time. However, the vertical waves forces, reacted by the tethers, cause the tension to change with time and this can cause a Mathieu type of instability in the platform sway motion. This phenomenon is investigated using a simple energy balance technique and it is shown that square law fluid damping places an upper bound on oscillation amplitude; it is found that platform sway motions due to Mathieu excitation remain acceptable even in large waves.

• Research Organization: Dept. of Mechanical Engineering, University College London, London
• OSTI ID: 6274761
• Journal Information: J. Energy Resour. Technol.; (United States), Journal Name: J. Energy Resour. Technol.; (United States) Vol. 104:3; ISSN JERTD
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420206* -- Engineering-- Mining & Drilling Equipment & Facilities-- (1980-1989)
423000 -- Engineering-- Marine Engineering-- (1980-)
DIFFERENTIAL EQUATIONS
DYNAMICS
ENERGY-LEVEL TRANSITIONS
EQUATIONS
EXCITATION
FREQUENCY DEPENDENCE
MATHIEU EQUATION
MECHANICAL STRUCTURES
MECHANICS
MOTION
OFFSHORE PLATFORMS
SUPPORTS
WAVE FORCES
WAVE PROPAGATION