APPLICATION OF TUNED LIQUID COLUMN DAMPER FOR PITCH MOTION REDUCTION OF SEMISUBMERSIBLE FLOATING PLATFORMS

Publish Year: 1397
نوع سند: مقاله کنفرانسی
زبان: English
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ICOPMAS13_076

تاریخ نمایه سازی: 6 بهمن 1397

Abstract:

Offshore floating platforms have been employed worldwide in many applications for decades. For the sake of safety, human comfort and increasing productivity it issuitable to reduce motions and vibrations of platforms as much as possible. Many researches have been conducted on different methods to reduce the motions of floatingplatforms. Recently, utilizing passive methods such as Tuned Mass Dampers (TMD) and Tuned Liquid Column Dampers (TLCD) are being considered increasingly [1].Among all passive methods, using TLCD is the most attractive one, because of its low cost, easy handling and few maintenance requirements [2, 3]. TLCD is a U-shaped tube, containing a liquid (commonly water). Usually, there is at least one orifice at the middle part of the tube causing a head loss when the liquid oscillates in the tube, resulting in energy dissipation. Application of TLCD in floating platforms is mostly studied on Tension-Leg Platforms (TLPs), so far. Lee et al. incorporated a TLP with a huge TLCD forthe first time on the topside in order to reduce the waveinduced vibration of the floating platform [4]. In order to calculate the response spectrum of the structure-TLCDsystem, they derived a transfer function for each DOF and multiplied it by the wave spectrum. A TLP, equipped with an underwater TLCD; known as UWTLCD; was later studied experimentally by Lee and Juang [5]. The pontoons of the platform were used as the vertical parts of the TLCD while connected with a horizontal small diameter tube. This scheme was used to equip the platform with a TLCD without any space occupation on the topside. As mentioned, both of the studies are concerning TLPs and application of TLCD isnot studied on semisubmersibles. In this study application of TLCD on a semisubmersible drilling rig is surveyed and especially the pitch motion of the platform is concerned.Because of slackness of semisubmersible catenary mooring lines, it is free to rotate and reducing the pitch motion is of importance.

Authors

Hamidreza Feizian

PHD Candidate, Civil Engineering Department, Tarbiat Modares, Tehran, Iran

Roozbeh Panahi

Assistant Professor, Civil Engineering Department, Tarbiat Modares, Tehran, Iran,