STUDY ON TENSION LEG PLATFORM VIBRATION CONTROLLING

1. A STUDY ON VIBRATION
CONTROL METHODS OF
TLP PLATFORMS
1
Presented by
Aparna M A
NSS20CESE03
Roll no:3
Guided by,
Dr. Jayalekshmi R
Professor, CED
NSS College of Engineering

2. OVERVIEW
2
 OBJECTIVES
 INTRODUCTION
 TENSION LEG PLATFORMS
 VIBRATION CONTROL METHODS
 CASE STUDY
 CONCLUSIONS
 REFERENCE

3. OBJECTIVES
3
• To study about different types of vibration control methods for Tension Leg Platforms

4. INTRODUCTION
• An offshore structure has no fixed access to dry land and may be
required to stay in position in all weather conditions.
• These may be fixed to seabed or floating.
• Offshore platforms are used for exploration of oil and gas from
seabed and processing.
4
Source : https://skillleaps.com/wp-content/uploads/2020/08/Offshore-Platforms.png

5. Offshore platforms can broadly categorized into two types:
 Fixed platforms
Jacket Platforms Gravity Platforms Compliant Towers
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Source :https://www.offshore-technology.com/wp-content/
uploads/sites/6/2017/09/2-hutton-field.jpg
Source :http://theconstructor.org/wp-
content/uploads/2017/0 1/gravity-based-offshore-
concrete-structrure.jpg
Source : https://www.offshore-technology.com/wp-content/
uploads/sites/6/2017/09/pate1.jpg

6.  Floating Platforms
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 Tension Leg Platform ( TLP )
 Spar
 Semi submersible
 Floating Production Storage & Offloading
Source
https://encryptedtbn0.gstatic.com/images?q=tbn:ANd9GcT52I
NwKrH4qqvbnybRlDsDQo7Mq47AX99dy_pG7z9cPTgpNwaFyJjuIp
YrlxK3OsYX5k0&usqp=CAU

7. Tension leg Platforms ( TLP )
• Tension Leg Platforms (TLPs) are floating facilities that are
tied down to the seabed by vertical steel tubes called tethers.
• This characteristic makes the structure very rigid in the
vertical direction and very flexible in the horizontal plane.
• The vertical rigidity helps to tie in wells for production,
while, the horizontal compliance makes the platform
insensitive to the primary effect of waves.
• Have large columns and Pontoons and a fairly deep draught
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Source : Hamid M Sedighi (2014)

8. Components of TLP
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Source : API RP 2T, 3rd edition, July 2010

9. TLP deck structure
• The structural arrangement provided for supporting the topside equipment or modules.
• Major structural component that ensures pontoons, columns and deck to act as one structural unit.
TLP foundation
• Installations at, or in the seafloor which serve as anchoring of the tendons
• Provides transfer of tendon loads to the foundation soil.
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10. 10
TLP hull
• Consists of buoyant columns, pontoons and intermediate structural bracings, as applicable.
TLP tendon system
• Comprises all components between & including the top connection to the hull and the bottom
connection to the foundation.
• Guidelines, control lines, umbilicals etc. for tendon service and or other permanent installation
aids are considered as part of the tendon system.

11. Why vibration control in TLP?
• TLPs in deep water have longer periods for the heave, pitch and roll motions (up to 6 s) which are
close to the dominant periods of fatigue sea states and thus may be excited at resonance by direct
wave energy.
• TLP drift motions (surge–sway–yaw motion), due to the action of wave forces, can be significant
during extreme weather conditions.
• These motions could affect the performance during operation and maintenance.
11

12. Vibration control methods
Vibration
Control
Methods
Passive
Active
Semi-Active
Hybrid
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13. Passive methods
• It does not require an external power source for its operation.
• It is usually consist of viscoelastic damping layers.
Active methods
• It uses external power to perform its function
• Generate control forces on the structure to control vibrations
13

14. 14
Semi-active methods
• Requires a small external power source for its operation and utilizes the motion of the structure to
develop control force
• It uses the advantages of both active and passive devices.
• Examples include shape memory alloys, pneumatically controlled granules and electro/magneto-
rheological fluids.
Hybrid methods
• Combine robustness of the passive device and high performance of the active devices.

15. Vibration control methods used for TLPs
Passive methods
 Tuned oscillators
 Single and multiple tuned Mass dampers
 Tuned liquid column dampers ( TLCB )
 Tuned liquid column Ball dampers ( TLCBD )
Active Methods
 Active control systems inside the hull
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16. Passive methods
 Tuned Liquid Column Damper ( TLCD )
• Tuned Liquid Column Dampers (TLCD) works on the
principle of motion of a liquid column in a U-shaped tube
counterbalancing external forces imposed onto the
structure.
• The TLCD is found to be successful way of vibration control
when structure is exposed to the wind and earthquake
loading.
Case study 1: To study vibration control using Tuned Liquid Column Damper ( TLCD )
[Source : Hamidreza Feizian et al(2020) ]
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17. In this study a Numerical modelling and Analytical modelling were used to investigate vibration
mitigation by TLCD
The mitigation was evaluated corresponding to the variation of the diameter and the draft of the
pontoon and the mass of the platform system
17
Source : Hamidreza Feizian et al(2020)

18.  Variation of Pontoon Draft (2 m)
Response comparison in X-direction (surge motion) Response comparison in Y-direction (heave motion)
Response comparison in rotation (pitch motion)
18
Source : Hamidreza Feizian et al(2020)
Source : Hamidreza Feizian et al(2020)
Source : Hamidreza Feizian et al(2020)

19. Comparison of the energy dissipation for various platform drafts
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Source : Hamidreza Feizian et al(2020)

20. Comparison of the energy dissipation for various platform mass
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Source : Hamidreza Feizian et al(2020)

21.  Experimental setup
• Testing model was constructed with woods as
well as the polymer material.
• The dimension of the platform is 0.91 m x 0.91
m
• Pontoon leg is 0.75 m long by 0.1 mx0.1 m
section-area anchored to the bottom of the
tank by strained tethers.
21
Source : Hamidreza Feizian et al(2020)

22. Response comparison for the model-platform in the time domain
Response comparison for the model-platform in the frequency domain
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Source : Hamidreza Feizian et al(2020)

23. • Energy dissipated from the TLCD device may reach a value higher than 70%, in many cases over 50%.
• Variation of the parameter of draft and dimension of the platform structure will influence the TLCD
performance.
• The amount of the energy being dissipated is decreased from 73% down to 55% with respect to the
increase of the pontoon dimension.
• Mitigation effect is reduced corresponding to the increase of the pontoon draft from 55% down to about 46%.
• For the mass variation the relevance between the mass variation and the effectiveness of the TLCD is not
significant.
• In the experimental results from a preliminary test for the feasibility of the TLCD application, this device could
be effective on the vibration suppression for the floating platform.
Conclusions from case study 1
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24. Case study 2: To study vibration control using Tuned Mass Damper ( TMD )
• TMD is a spring-mass system, which is attached to the primary
structure to control its response.
• TMD is attached to the primary structure through spring and dashpot
and has its natural frequency tuned closer to that of the primary.
• This scheme of tuning the damping depends on its mass and stiffness.
• Excess energy that is built up in the primary structure is then
transferred to the secondary and subsequently dissipated through the
inertia force
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[Source : S. Chandrasekaran et al (2016)]
[Source : S. Chandrasekaran et al (2016)]

25. • A 1:100 scale model of AUGER TLP is fabricated without top side details.
• Acrylic sheets are used for columns, pontoons and deck.
• Steel wires of high tensile strength are used as tethers.
 Experimental setup
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[Source : S. Chandrasekaran et al (2016)]

26. Sl.No Description Units Prototype Model 1:100
1 Length of deck m 100 1
2 Width of deck m 100 1
3 Column Height m 49 0.49
4 Diameter column m 25 0.25
5 Draft m 30 0.30
6 Width of Pontoon m 11 0.11
7 Pontoon Height m 9 0.09
8 Tethers diameter m 0.7 0.007
9 No : of Tendons m 12 4
Geometric properties of the platform
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27. • TMD, considered in this experiment, consists of a solid mass and a
spring element.
• Mass ratios of 1.5% and 3.0% are chosen.
• A rectangular box of size 120 × 100 mm and 850 mm long and
mass of 0.6 kg is fabricated to obtain the mass ratio of 1.5%.
• 3% mass ratio is achieved by filling sand of 0.6 kg in the box.
Mass used in the TMD.
Springs used in the TMD:
(a) Spring for μ %. = 1.5%;
(b) spring for μ = 3.0
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[Source : S. Chandrasekaran et al (2016)]
[Source : S. Chandrasekaran et al (2016)]

28.  Experimental investigations are carried out in the wave flume under unidirectional regular waves.
 Three configurations of TLP namely:
(i) TLP without TMD;
(ii) TLP with TMD of 1.5% mass ratio.
(iii) TLP with TMD of 3.0% mass ratio.
 Model tests are conducted under regular waves for wave height of 4–8 cm and period ranging from
1.2–44. s with an interval of 0.2 s
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29. 29
Surge
acceleration
m/𝒔2
Pitch ( deg) TMD
acceleration
m/𝒔2
Difference ( %)
Description T(s) ξ (%) T(s) ξ (%) T(s) ξ (%) T(s) ξ (%)
Without damper 4.02 9.97 0.5 35.69
With damper μ =
1.5%
4.2 13.65 0.46 35.98 2.2 8.98 4.47 36.9
With damper μ = 3% 4.4 16.69 0.45 36.25 2.2 12.10 9.45 67.4
Free vibration response of platform with and without tuned mass damper
RESULTS

30. 30
Surge free decay test without damper
Pitch free decay test without damper

31. Displacement time history of TLP and TMD (μ = 1.5%)
Displacement time history of TLP and TMD (μ = 3.0%) 31

32. • Spring-mass system with higher mass ratio is effective for response reduction with
wide range of time period.
• TMD shows better control for the larger wave heights.
• Implementing TMD to the increases the damping ratio of the structure without
altering the characteristics of TLP, which is vital.
• The response reduction increases with the increase in mass ratio of the damper..
Conclusions from case study 2
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33. CONCLUSIONS
• Passive methods are mostly used for vibration control of Tension leg platforms .
• Active methods are rarely used due to high operational costs, less reliability and simplicity.
• General trend for vibration control is progressing from passive to semi active methods.
• Current Researches are based on study of semi active methods.
• Hybrid methods have not been extensively explored
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34. 1. Srinivasan Chandrasekaran, Deepak Kumar and Ranjani Ramanathan (2013), ‘Dynamic response of
tension leg platform with tuned mass dampers’, Journal of Naval Architecture and Marine Engineering.
1. Fayiz C M, Dr. Jayalekshmi R ( 2016) , ‘Vibration control of tension leg platforms using mass dampers
under random waves’, International Journal of Scientific & Engineering Research.
2. Srinivasan Chandrasekaran, Deepak Kumar & Ranjani Ramanthan (2016) ,’ Response control of
tension leg platform with passive damper: experimental investigations’, Ships and Offshore Structures.
3. Ramkumar Kandasamy,Fangsen Cui, Nicholas Townsend, Choon Chiang Foo, Junyan Guo, Ajit
Shenoi,Yeping Xiong Rao (2016) ,’ A review of vibration control methods for marine offshore
structures’, Ocean Engineering, Volume 127.
REFERENCES
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35. 5. Shibin P Shaji, Dr. Jayalekshmi R (2016) ,‘ Earthquake Analysis of Mini Tension Leg Platforms under
Random Waves’, SSRG International Journal of Civil Engineering ,Volume 3.
6.Timothy Murfet and Nagi Abdussamie (2019), ‘Loads and Response of a Tension Leg Platform Wind
Turbine with Non-Rotating Blades: An Experimental Study’, Journal of Marine Science and Engineering.
7. Jianxing Yu, Zhenmian Li, Yang Yu 1, Shuai Hao, Yiqin Fu, Yupeng Cui, Lixin Xu and Han Wu
(2020), ‘Design and Performance Assessment of Multi-Use Offshore Tension Leg Platform Equipped with an
Embedded Wave Energy Converter System’, Journal of Marine Science and Engineering.
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36. 36
8. V Jaksic, C Wright, Afeef Chanayil, Shaikh Faruque Ali, Jimmy Murphy and Vikram Pakrashi
(2015), ‘Performance of a Single Liquid Column Damper for the Control of Dynamic Responses of a
Tension Leg Platform’, Journal of Physics: Conference Series 628 .
9. Hsien Hua Lee and H.H. Juang (2012) , ‘Experimental study on the vibration mitigation of offshore
tension leg platform system with UWTLCD’, Smart Structures and Systems, Vol. 9.

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Thank you!!!