The ringing response is important for tendon extreme tension estimates. This results from an impulse load in an extreme sea state, which will excite a transient response. Similar, but different in origin, is a second high frequency response referred to as ringing. A springing response of a TLP can also result in vertical accelerations, which affect the comfort of personnel. While typically small, springing is usually not negligible and it is important for the estimation of fatigue of the tendons and supporting structure (API RP2T). Wave energy close to the natural period of the platform results in an amplified response at resonance known as “springing”. Since the natural period in heave and pitch is lower than the wave energy, global heave and pitch wave loads on the platform are carried directly by the tendons. However, as a mechanically elastic system, there are vertical and rotational responses to the heave forces and pitch moments. In the usual sense of floating structures, there are no heave or pitch motions. Dynamic offset includes wave frequency and low frequency responses. Offset includes a steady component from steady wind, current and drift forces. 7.47), this is a corresponding downward motion, geometrically coupled to offset. However, what is truly different for a TLP is set-down. Offset from lateral forces is not altogether different from surge/sway response of any compliantly restrained floater.
John Halkyard, in Handbook of Offshore Engineering, 2005 MotionsĪ TLP is highly compliant to lateral forces and, at the same time, is highly resistant to vertical forces.
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