Study of Offshore Jacket Platform Attached With Tuned Liquid Column Gas Damper

2017 ◽  
Author(s):  
P. Sathish ◽  
A. S. Sajith
Keyword(s):  
Natural Resources ◽  
Wave Theory ◽  
Wave Force ◽  
Offshore Structures ◽  
Liquid Column ◽  
Offshore Platforms ◽  
Jacket Platform ◽  
Tuned Liquid Dampers ◽  
Offshore Jacket Platform ◽  
Gas Damper

With increase in need of energy, scarcity of natural resources also increases. Need for energy has led the people to move into the ocean since they contain abundant natural resources. Offshore platforms play a major role in exploring and exploiting these resources. Jacket platform being a fixed offshore jacket platform is used in water depths 300 to 400 m. The study of behavior of these offshore structures is vital part in the design since they are subjected to dynamic loading of waves, wind, earthquake, ice etc. These structures in hostile environment are subjected to heavy loads. There is need for controlling the response of these structures. This can be achieved by providing external dampers. There are various dampers available to control the response of structures. Tuned liquid dampers (TLD)s and Tuned Liquid Column Damper (TLCD)s use liquid inside to tune its frequency to natural frequency of structure. Tuned Liquid Column Gas Damper (TLCGD) is latest version of dampers. It has a unique flexibility of tuning frequency compared to all other dampers. In the present study, jacket platform is modeled as Multi degree of freedom (MDOF) system. At later stage, for simplistic analysis, MDOF system is reduced to SDOF system using static condensation. Performance of TLCGD for both the systems is compared. Airy’s wave theory is used for wave force excitation. Equations of motions for Jacket platform models attached with TLCGD are developed and solved using Newmarks β method in MATLAB. TLCGD is found to be very flexible in tuning the frequency and maximum reductions in response, 21.3% and 23.14% are observed at 0.3 MPa for MDOF and SDOF systems respectively. Work done shows that the results for MDOF and SDOF are comparable and hence, jacket as SDOF can be used for analysis for reducing the complexities.

RMS Control of Response of Jacket Structure Using Tuned Liquid Column Ball Gas Damper Under Random Ocean Waves

2021 ◽  
Author(s):  
Satheesh Jothinathan ◽  
Deepak Kumar
Keyword(s):  
Genetic Algorithm ◽  
Oil And Gas ◽  
Good Control ◽  
Wave Force ◽  
Ocean Waves ◽  
Good Alternative ◽  
Offshore Structures ◽  
Liquid Column ◽  
Jacket Structures ◽  
Gas Damper

Abstract Jacket structures are one of the most important offshore structures for extracting oil and gas. The fatigue life is affected due to the continuous dynamic wave force experienced by the structure. Generally, the structure is designed so that the dynamic response is small, which increases the cost. So, controlling its response is a good alternative to increase its life span. In this work, a simplified jacket structure under a random sea state is controlled for its response using a tuned liquid column ball gas damper (TLCBGD). The jacket structure in a water depth of 60m is modeled in a surge degree of freedom. The parameters of TLCBGD are optimized using a genetic algorithm for achieving better control in response quantities. For the analysis purpose, the wave is considered stochastic and presented by Pierson–Moskowitz (PM) spectrum of significant wave height 10m. In such a case, the jacket structure response can be presented using the root mean square (RMS) values obtained from the Lyapunov technique. Based on the random vibration analysis theory, the Lyapunov method can be employed to obtain the RMS of the system driven directly without solving the governing differential equation. This method requires the system to be driven by white noise. So, in this study, filters are developed to get the required narrow banded ocean spectrum. It is noticed that the response quantity is highly sensitive to the filter parameters. This is because a slight change in excitation parameters and a change in filter parameters near the system’s natural frequency affect the response significantly. Further, it is seen that the use of the genetic algorithm for tuning the TLCBGD gives very good control on the response quantity of the jacket structure.

A New Approach for Dynamic Reliability Analysis of Offshore Platforms

2003 ◽  
Author(s):  
Wei-Liang Jin
Keyword(s):  
Reliability Analysis ◽  
Failure Criterion ◽  
Offshore Platform ◽  
Seismic Action ◽  
Offshore Platforms ◽  
Structural Dynamic ◽  
Jacket Platform ◽  
Dynamic Reliability ◽  
Strength Failure ◽  
Offshore Jacket Platform

The theoretical framework of a new dynamic reliability analysis approach for offshore jacket platforms is constructed in this paper. In this approach, the structural dynamic reliability analysis integrates the structural dynamic response theory with the random sampling technique on stochastic variables of the platform. Offshore jacket platform is assumed as a shear type one and is controlled by its horizontal resistance bearing capacity. The failure criterion of offshore platform dynamic reliability includes two aspects: strength failure criterion and deformation failure criterion. The strength failure criterion is based on the double-damage criterion of ultimate dynamic analysis, while the deformation failure criterion depends on the requirement of the offshore oil production. The dynamic reliability formula of offshore platforms is gained on the basis of the first crossing theory. In this paper, uncertainties of offshore jacket platform dynamic reliability subjected to wave hydrodynamic and seismic action are studied respectively. The probabilistic distributions and its statistical characteristics of wave hydrodynamic and seismic action are given on the base of limit bearing state of the platform. The dynamic reliability analysis of an offshore platform W11-4C, located at the gulf of Weizhou, South China Sea, is carried out. Some valuable conclusions are summarized.

Non-Harmonic Decomposition of Sea Measured Data of Offshore Platforms

2016 ◽  
Author(s):  
Fushun Liu ◽  
Jinchao Cao ◽  
Jiefeng Chen ◽  
Wenlong Yang ◽  
Wei Li
Keyword(s):  
Model Updating ◽  
Wave Force ◽  
Offshore Structures ◽  
Measured Data ◽  
External Loading ◽  
Offshore Platforms ◽  
Modal Parameter ◽  
Application Performance ◽  
Harmonic Decomposition ◽  
Harmonic Components

The measured data are often required and taken as the input of different kinds of algorithms for modal parameter identification, model updating and/or damage detection of offshore platforms. This paper investigates the application performance of the approach to offshore platforms, by using real measured data. Considering the fact of a recorded loading is always finite in duration, most likely aperiodic, and even damped because of the existence of damping of the structures, a recent developed complex exponential decomposition method [1] was employed to deal with real measured data. Therefore, in this article, three kinds of measured data will be used. The first one is a measured wave force that was collected through an experiment conducted in the lab of Ocean University of China, to investigate the feasibility of original external loading decomposition. To study the performance of the proposed method when applied to offshore structures, two sets of typical signals are used: one set was collected from the JZ20-2MUQ offshore platform when it was excited by ice, and the other was collected from the WZ11-4D platform when it was excited by waves. The results show that the approach can decompose the real measured data into a series of non-harmonic components, and a large model order is often suggested.

Extremes of Morison-Type Wave Loading on a Single Pile

1978 ◽  
Vol 100 (1) ◽  
pp. 100-104 ◽  
Author(s):  
G. Moe ◽  
S. H. Crandall
Keyword(s):  
Unit Length ◽  
Wave Theory ◽  
Wave Force ◽  
Offshore Structures ◽  
Random Motion ◽  
Linear Wave ◽  
Wave Loading ◽  
Sea State ◽  
Steady Current ◽  
Wave Heights

A statistical estimate of the extreme wave force per unit length acting on a section of a fixed cylindrical pile in a random sea-state is derived. The random motion of the sea is described by a spectrum of wave heights in conjunction with linear wave theory. The wave force is assumed to depend linearly on the water particle acceleration and non-linearly on the water velocity according to the Morison formula. The interaction of the velocity and acceleration contributions and the contribution of a small steady current are accounted for by an asymptotic approximation valid for large forces. The expected rate of occurrences of extremes based on a simple peak definition agrees satisfactorily with a more elaborate result based on a true maximum definition. The formulas derived here provide a basis for a design-force procedure which could provide an improvement over the design-wave procedure commonly used for the analysis of offshore structures.

Finite Element Analysis for Structural Performance of Offshore Platforms under Environmental Loads

2013 ◽  
Vol 569-570 ◽  
pp. 159-166 ◽  
Author(s):  
Shehata E. Abdel Raheem ◽  
Elsayed M.A. Abdel Aal
Keyword(s):  
Finite Element ◽  
Return Period ◽  
Wave Force ◽  
Offshore Structures ◽  
Offshore Platform ◽  
Offshore Platforms ◽  
Offshore Structure ◽  
Current Increase ◽  
Environmental Loads ◽  
Highly Nonlinear

Offshore structures for oil and gas exploitation are subjected to various ocean environmental phenomena which can cause highly nonlinear action effects. Offshore structures should be designed for severe environmental loads and strict requirements should set for the optimum performance. The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. The structure is discretized using the finite element method, wave force is determined according to linearized Morison equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the one year return period wave and must be able to survive the 100 year return period storm conditions. The results show that the nonlinear response analysis is quite crucial for safe design and operation of offshore platform. Fixed Jacket type offshore platforms under extreme wave loading conditions may exhibit significant nonlinear behavior. The effect of current with different angles when hitting the offshore structure with the wave and wind forces, is very important for calculate the stress, the response displacement and deformation shapes. As the current increase or decrease the effect of wave force according to the hitting angle of current.

A method of technical diagnostics for offshore structures

1994 ◽  
Vol 16 (2) ◽  
pp. 43-48
Author(s):  
Do Son
Keyword(s):  
Diagnostic Method ◽  
Joint Venture ◽  
Oil And Gas ◽  
Residual Life ◽  
Life Time ◽  
Offshore Structures ◽  
Technical Diagnostics ◽  
Offshore Platforms ◽  
South Vietnam ◽  
Local Destruction

This paper describes the results of measurements and analysis of the parameters, characterizing technical state of offshore platforms in Vietnam Sea. Based on decreasing in time material characteristics because of corrosion and local destruction assessment on residual life time of platforms is given and variants for its repair are recommended. The results allowed to confirm advantage of proposed technical diagnostic method in comparison with others and have been used for oil and gas platform of Joint Venture "Vietsovpetro" in South Vietnam.

scholarly journals Risk assessment of aging offshore jacket platform group: a case study on “B” Field platforms

2021 ◽  
Vol 649 (1) ◽  
pp. 012068
Author(s):  
R D Riyanto ◽  
I H Helvacioglu ◽  
M Murdjito ◽  
E B Djatmiko ◽  
K Sambodho ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Jacket Platform ◽  
Offshore Jacket Platform ◽  
Group A

Dynamic monitoring of an offshore jacket platform based on RTK-GNSS measurement by CF-CEEMDAN method

2021 ◽  
Vol 115 ◽  
pp. 102844
Author(s):  
Wen Chen ◽  
Chunbao Xiong ◽  
Lina Yu ◽  
Sida Lian ◽  
Zhuang Ye
Keyword(s):  
Dynamic Monitoring ◽  
Jacket Platform ◽  
Offshore Jacket Platform
Sign in / Sign up

Export Citation Format

Share Document