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offshore-jacket-platforms
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Damage detection in an offshore jacket platform using genetic algorithm based finite element model updating with noisy modal data
, Article Procedia Engineering, Solo, Jawa Tengah ; Volume 54 , March , 2013 , Pages 480-490 ; 18777058 (ISSN); 9781627486354 (ISBN) ; Golafshani, A. A ; Sharif University of Technology
2013
Abstract
Offshore jacket platforms are one of the most motivating structures for damage detection due to their importance and productivity. In this study, the application of finite element model updating in damage detection of an offshore jacket platform is investigated. The objective function of this method is based on the measured and analytical modal data, including natural frequencies and mode shapes. However, the measured data is expected to be noisy. Also, to avoid obtaining false damage results, a penalty term is added to the objective function. To update the model, genetic algorithm is utilized as a robust global searching tool. Afterward, the efficiency of this method is evaluated on several...
Study of Pattern of Sensor Installation for Analysis of Offshore Jacket Behavior
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor)
Abstract
Nowadays, many offshore jacket platforms have been built in all over the world for excavating oil and gas. Due to cost of construction and maintenance, they are considered as national assets. Jacket platforms are always under various types of loads in their time life, so they cause some damages to them. Hence, on time damage detection can prevent possible extravagant costs of repair and reconstruction. Because many jacket platforms are in Iran, this issue can be very important.Structural health monitoring (SHM) improvised to ensure safety and detect damages of structures uses sensors. They transfer data received from structures to the computers in order that after interpretation of data,...
Damage detection of offshore jacket structures using frequency domain selective measurements
, Article Journal of Marine Science and Application ; Volume 12, Issue 2 , June , 2013 , Pages 193-199 ; 16719433 (ISSN) ; Golafshani, A. A ; Ghodrati, E ; Sharif University of Technology
2013
Abstract
The development of damage detection techniques for offshore jacket structures is vital to prevent catastrophic events. This paper applies a frequency response based method for the purpose of structural healthCgreater detection efficiency. In addition, the performance of the proposed method was evaluated in relation to multiple damages. The aforementioned points are illustrated using the numerical study of a two dimensional jacket platform, and the results proved to be satisfactory utilizing the proposed methodology
Investigation of Crack and Buckling Effects on Ultimate Capacity of Fixed Offshore Platforms with Dynamic Analysis Approach
, Ph.D. Dissertation Sharif University of Technology ; Sayyadi, Hassan (Supervisor) ; Tabeshpoor, Mohammad Reza (Supervisor)
Abstract
Tubular sections and consequently tubular joints in construction of steel structures in the form of space frames is widely used in ground and marine structures, including offshore jacket platforms. The passage of part of the life of the existing offshore platforms has caused cracks in various parts of the joints of these structures due to various reasons, the most important of which is fatigue. In this thesis, by adopting numerous numerical studies and validations with some cited experimental papers, the principles governing the proper buckling behavior of tubular members focusing on the conventional geometries of Persian Gulf platforms as well as the behavior and local flexibility of...
Damage Detection of Offshore Jacket Platforms Using Fitting Vibration Data
, M.Sc. Thesis Sharif University of Technology ; Ali Akbar, Golafshani (Supervisor)
Abstract
In the regard of structural health monitoring the identification of the structural modal parameters is essential. Since the different sources (wind, waves, Devices …) induce vibration on an offshore platform, it is impossible to determine the portion of each source in vibration. Thus the methods that analyze vibrations needless of input measurements are more efficient. These methods apply the ambient factors and obtain the modal properties from the structural response. This procedure has no unwanted effect on the serviceability of structure and by placement of sensors on the platform; one can monitor the structural health.
In the present work a two dimensional jacket offshore platform...
In the present work a two dimensional jacket offshore platform...
Probabalistic Damage Detection of Ofshore Platforms
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor)
Abstract
High construction and installation costs of offshore platforms, and also harsh environments in which they operate, make health monitoring of these structures more important. Conventional methods to solve the health monitoring problem are deterministic, whereas much uncertainties are imposed to the problem. In most methods of health monitoring methods we try to identify natural frequencies and mode shapes of structures by using its dynamic response. This set of data is then compared to results of modal analysis performed on a finite element model of structure in order to detect any possible damage. In deterministic methods each response of structure is pertained to one damage state, in a...
Structural Health Monitoring of Offshore Jacket Platforms by Inverse Vibration Problem
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor) ; Mohtasham Dolatshahi, Kiarash (Co-Advisor)
Abstract
In this thesis selection criteria are present for types, numbers and locations of sensors for structural health monitoring of offshore jacket platform in the Persian Gulf. The selection criteria are chosen by studying structural health monitoring of various structures in civil and aerospace industries. Knowing the types of sensors that can be used, a new approach of inverse vibration problem is introduced for structural health monitoring of offshore jacket platforms. In the previous studies, significant numbers of frequencies and mode shapes are usually used to detect damages by updating components of stiffness matrix. Considering the fact that offshore platforms are composed of a heavy...
Hybrid damping systems in offshore jacket platforms with float-over deck
, Article Journal of Constructional Steel Research ; Vol. 98, Issue. 1 , 2014 , pp. 178-187 ; ISSN: 0143-974X ; Kashani, M ; Parvar, M. R. A ; Golafshani, A. A ; Sharif University of Technology
Abstract
Employing dampers to control wave-induced and seismic vibrations of offshore jacket platforms is an attractive method in order to mitigate fatigue and seismic damage. However, adjustable parameters of a damper are designed by considering only one type of environmental loads; either normal-condition load or extreme-condition load. So, it is important to investigate effectiveness of damping system, for both of two main categories of environmental loads. Also it is ideal for the system to have an acceptable performance in both normal and extreme conditions. The idea investigated in the current study is to use a friction damper device (FDD) and a tuned mass damper (TMD) simultaneously in...
Analytical Studies on Vibration Control of Offshore Jacket Platforms with Hybrid Damping Systems
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor)
Abstract
Employing dampers to control wave-induced and seismic vibrations of offshore jacket platforms is an attractive method in order to mitigate fatigue and seismic damage. However, adjustable parameters of a damper are designed by considering only one type of environmental loads; either normal-condition load or extreme-condition load. So, it is important to investigate effectiveness of damping system, for both of two main categories of environmental loads. Also it is ideal for the system to have an acceptable performance in both normal and extreme conditions. The idea investigated in the current study is to use a friction damper device (FDD) and a tuned mass damper (TMD) simultaneously in...
Structural Health Monitoring Considering Mass and Stiffness Modification
, M.Sc. Thesis Sharif University of Technology ; Mohtasham Dolatshahi, Kiarash (Supervisor)
Abstract
Damage detection of civil structures and infrastructures using partial modal information has been an interesting field of research. So far, three main algorithms are introduced for health monitoring of structures. The first method relies on identifying stiffness and mass properties, as physical parameters, of structures using inverse eigenvalue problem considering mass modifications in 2D and 3D shear-frame models of structures. Comparing the identified matrices with the primary values, one can detect the damage occurrence, its level and severity in the structure. Applicability of this method in health monitoring of offshore jacket platforms as one of noteworthy civil infrastructures has...
Damage Detection in Offshore Jacket Structures Using Invers Vibration Problem (IVP)Technique with a Look on Probabilistic Bayesian Network Modeling
, M.Sc. Thesis Sharif University of Technology ; Abbaspour, Madjid (Supervisor) ; Tabeshpour, Mohammad Reza (Supervisor)
Abstract
Damage detection in all kinds of human-made structures has been given serious attention as one of the main branches of engineering sciences, and significant progress has been made in this field, especially in the field of civil engineering, aerospace and heavy industries. However, although this topic is discussed academically in the field of offshore structures for two decades, not much development has happened in practice and it is still in the stage of knowledge development. One of the most important characteristics of practical online damage detection methods is the ability to be used knowing little information about the modal characteristics of the structure. In this research, an attempt...
Inverse vibration technique for structural health monitoring of offshore jacket platforms
, Article Applied Ocean Research ; Volume 62 , 2017 , Pages 181-198 ; 01411187 (ISSN) ; Lotfi, A ; Dolatshahi, K. M ; Golafshani, A. A ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In this paper a new approach is introduced for structural health monitoring of offshore jacket platforms. The procedure uses the measured ambient vibration responses and the corresponding readable natural frequencies and mode shapes of the structural system. Since offshore platforms are composed of heavy topsides supported by jacket structures, participation of the first mode is dominant in each direction in the response of the structure under field excitations. Moreover, ambient vibrations such as wave loads and boat impacts only excite the first modes of the structure. Therefore, it is difficult to find higher modes and the pertinent frequencies by use of accelerometers data. The...
Health monitoring of structures using few frequency response measurements
, Article Scientia Iranica ; Volume 17, Issue 6 A , NOVEMBER-DECEMBER , 2010 , Pages 493-500 ; 10263098 (ISSN) ; Kianian, M ; Ghodrati, E ; Sharif University of Technology
2010
Abstract
The development of damage detection techniques for offshore jacket structures is vital for preventing catastrophic events. This paper applies a frequency response based method for the purpose of structural health monitoring. In this approach, the concept of a minimum rank perturbation theory is used. The feasibility of using a finite number of sensors and its effect on damage detection capabilities is investigated. In addition, the performance of the proposed method is evaluated in the case of multiple damages. The aforementioned points are illustrated using the numerical study of a two dimensional jacket platform