Author: Chaohui JinPublisher:
ISBN:
Category :
Languages : en
Pages : 768
Book Description
Assessments of Performance and Reliability of Template-type Offshore Platforms Under Extreme Hurricane Conditions
Author: Chaohui JinReliability of Dynamically Sensitive Offshore Platforms Exposed to Extreme Waves
Author: Jalal MirzadehPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The growing interest in the use of offshore platforms in deeper waters and harsher environments, as well as the desire to extend the operation of existing structures beyond their design lives, is increasing attention on the assessment of their dynamic response and their failure conditions under extreme storm loading. There are a large number of factors influencing the performance of dynamically sensitive platforms, but a major issue is how to include all of the irregularity, directionality and nonlinearity that ocean waves cause on their loading. Therefore, the role each plays in the assessment of dynamically sensitive structures under extreme loads is investigated systematically in this thesis. The aim is to develop practical methods to estimate extreme response and the probability of failure of dynamically sensitive offshore structures in a given sea-state. The directionality and nonlinearity of ocean waves has been captured in this thesis by extending the formulations of the NewWave and Constrained NewWave theories. NewWave is a deterministic method that accounts for the spectral composition of the sea-state, and can be used as an alternative to both regular wave and full random time domain simulations of lengthy time histories. Based on this theory a predetermined crest height and the surface elevation around the crest during an extreme event can be theoretically simulated. Constrained NewWave, which is generated by mathematically constraining a NewWave within a random time series, allows the irregularity of ocean waves to be considered. These wave theories have been extended in this thesis to include 2nd order and directionality effects, and their formulations have been written into a new Fortran code for calculation of the water surface and water particle kinematics. The effects of irregularity, directionality and nonlinearity of ocean waves on dynamically sensitive structures are then shown for an example mobile jack-up drilling platform. The sample jack-up platform is modelled in the USFOS software, and includes the effects of material and geometrical nonlinearities as well as spudcan-soil-structure nonlinear interactions. Finally, based on structured application of multiple Constrained NewWaves in combination with the Monte Carlo method, a framework is proposed to estimate the extreme response and the failure probability of dynamically sensitive offshore structures exposed to a given duration of the one extreme sea-state. The results demonstrate that in an extreme event the irregularity, directionality and nonlinearity of ocean waves have considerable effects on the overall performance of the sample jack-up platform. It is shown that the extreme response and the probability of failure of the sample jackup are not only governed by the maximum crest elevation but also depend on the random background of ocean waves. In addition, it is indicated that the inclusion of the directionality effects of ocean waves results in reductions in the extreme response and failure rate of the sample jack-up platform. On the other hand, the nonlinearity effects cause additional energy in low and high frequencies and raise the crest height, which increases the extreme response of the sample jack-up platform. The methods developed in this thesis have application to any dynamically sensitive structure and will help reduce the level of uncertainty in predicting their extreme response or failure probability. This may help in extending their operational conditions, say into deeper waters and harsher sea-states, or in extending their operational life.
Dissertation Abstracts International
Author: Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 856
Book Description
Offshore Compliant Platforms
Author: Srinivasan ChandrasekaranPublisher: John Wiley & Sons
ISBN: 1119669782
Category : Technology & Engineering
Languages : en
Pages : 256
Book Description
A guide to the analysis and design of compliant offshore structures that highlights a new generation of platforms Offshore Compliant Platforms provides an authoritative guideto the analysis and design of compliant offshore structures and puts the focus on a new generation of platforms such as: triceratops, Buoyant Leg Storage and Regasification platforms. Whilst the authors – noted experts on the topic – include basic information on the conceptual development of conventional platforms, the book presents detailed descriptions of the design and development of new deep-water platforms. The book describes the preliminary design of triceratops in ultra-deep waters and presents a detailed analysis of environmental loads that are inherent in offshore locations such as wave, wind and current. The new methodology for the dynamic analysis of triceratops under ice loads, predominantly in ice-covered regions, is also examined with detailed parametric studies. In addition, the book covers the structural geometry and the various methods of analysis for assessing the performance of any other similar offshore platform under the special loads. A discussion of the fatigue analysis and service life prediction is also included. This important book: • Includes the analysis and design of compliant offshore structures with a focus on a new generation of platforms • Examines the preliminary design of triceratops in ultra-deep waters • Covers an analysis of environmental loads that are inherent in offshore locations such as wave, wind and current • Reviews the structural geometry and various methods of analysis for assessing the performance of any other similar offshore platform under special loads • Discusses fatigue analysis and service life prediction Written for engineers and researchers across engineering including civil, mechanical, structural, offshore, ocean and naval architecture, Offshore Compliant Platforms fills the need for a guide to new offshore platforms that provides an understanding of the behaviour of these structures under different loading conditions.
Reliability Assessment of Foundations for Offshore Mooring Systems Under Extreme Environments
Author: Young Jae ChoiPublisher:
ISBN:
Category : Deep-sea moorings
Languages : en
Pages : 406
Book Description
Mooring systems for floating facilities that are used offshore to produce oil and gas, consisting of individual mooring lines and foundations, are currently designed on the basis of individual components and on a case-by-case basis. The most heavily loaded line and anchor are checked under extreme loading conditions (hurricane and loop current) with the system of lines intact and with one line removed. However, the performance of the entire mooring system depends more directly on the performance of the system of lines and foundations rather than on the performance of a single component. In this study, a floating production system design originally developed by the industry consortium, DeepStar, was chosen for study. The mooring system was designed for three different nominal water depths: 1000, 2000 and 3000 m. It is a classic spar with steel mooring lines in 1000 m of water and polyester mooring lines in deeper depths. Based on simulated results of loads on mooring lines and foundations using a numerical model, reliability analyses were conducted using representative probabilistic descriptions of the extreme met-ocean conditions, hurricanes and loop currents, in the Gulf of Mexico. The probability of failure of individual mooring line components during a 20-year design life is calculated first, followed by that of a complete mooring line which consists of top and bottom chains, a steel cable or polyester rope at the middle and a suction caisson foundation, and finally that of the mooring system. It is found that foundations have failure probabilities that are more than an order of magnitude smaller than those for lines under extreme loading. Mooring systems exhibit redundancy in that the failure of the most heavily loaded component during an extreme event does not necessarily lead to failure of the system. The system reliability and redundancy are greater for the taut versus semi-taut systems and is greater for designs governed by loop current versus hurricane events. Although this study concerns about the mooring systems of a classical spar, the methodology of the reliability analysis and the conclusions made in this study may have important implications to the other deepwater mooring systems.
A Probabilistic Screening Methodology for Use in Assessment and Requalification of Steel, Template-type Offshore Platforms
Author: Mehrdad MortazaviReliability Assessment of Offshore Platforms Exposed to Wave-in-deck Loading
Author: E. Asp HansenNear-failure Behavior of Jacket-type Offshore Platforms in the Extreme Wave Environment
Author: Douglas G. SchmuckerPublisher:
ISBN:
Category :
Languages : en
Pages : 522
Book Description
American Doctoral Dissertations
Author: Publisher:
ISBN:
Category : Dissertation abstracts
Languages : en
Pages : 848
Book Description
Author: