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extreme-waves
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Developing Dynamic Increasing Amplitude and Period (DIAP)Method for Evaluation of Offshore Structures
, M.Sc. Thesis Sharif University of Technology ; Tabeshpour, Mohammad Reza (Supervisor) ; Dastan Diznab, Mohammad Ali (Co-Advisor)
Abstract
In this study, Wave Endurance Time (WET) is introduced as an applicable method for assessment of offshore structures under extreme waves. In this method, artificial records called Wave Functions (WFs) are used instead of usual extreme wave records. WFs are designed so that their excitations gradually increase with time. Therefore, one WF can be replaced by a large number of sea surface records with different excitation levels. The main advantage of proposed method is that it assesses the structural performance under various extreme waves with low computational cost especially in comparison with three-hour simulasions. Moreover, reliability of structures can be evaluated based on the time...
Analysis of Heat and Cold Waves Indices
, M.Sc. Thesis Sharif University of Technology ; Moghim, Sanaz (Supervisor)
Abstract
Heat waves and cold waves are among the most important extreme weather events, which could directly affect human health. The heat wave and cold wave are defined as a period of consecutive days (usually at least 3 days) when hot or cold air persists over a region. However, there is no universal definition of these two phenomena in different scientific references, and the available definitions differ depending on the type of temperature index, the minimum required duration, and the defined threshold temperature. This research aims to examine the main indices of heat waves and cold waves and analyze them in 6 major cities: Tehran, London, Madrid, New York, Shanghai, and Vancouver which have...
A New Method for Assessment of Fixed Offshore Platforms under Wave Load
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor) ; Tabeshpour, Mohammad Reza (Co-Advisor)
Abstract
Nowadays, according to existence of oil resources in offshore areas and the necessity of extracting, constructing of offshore platforms is developed. The design of these structures has high effect on the cost of construction and maintenance and the performance under the loads such as wave, earthquake, impact, etc. Therefore, if the analysis of platform structure is more accurate the evaluation of the behavior and consequently the better design in different conditions is better. In this thesis, a modification of Endurance Wave Analysis (EWA) in evaluation of offshore structures is introduced in this study. EWA is a new method to predict the response of offshore structures in different sea...
Sensitivity analysis of jacket-type offshore platforms under extreme waves
, Article Journal of Constructional Steel Research ; Volume 83 , 2013 , Pages 147-155 ; 0143974X (ISSN) ; Bahaari, M. R ; Bagheri, V ; Ebrahimian, H ; Sharif University of Technology
2013
Abstract
Jacket-type offshore platforms play an important role in oil and gas industries in shallow and intermediate water depths such as Persian Gulf region. Such important structures need accurate considerations in analysis, design and assessment procedures. In this paper, nonlinear response of jacket-type platforms against extreme waves is examined utilizing sensitivity analyses. Results of this paper can reduce the number of random variables and consequently the computational effort in reliability analysis of jacket platforms, noticeably. Effects of foundation modeling have been neglected in majority of researches on the response of jacket platforms against wave loads. As nonlinear response of...
Response spectrum method for extreme wave loading with higher order components of drag force
, Article Journal of Marine Science and Application ; Volume 16, Issue 1 , 2017 , Pages 27-32 ; 16719433 (ISSN) ; Dezfouli, Mani, F ; Dastan Diznab, M. A ; Mohajernasab, S ; Seif, S. M ; Sharif University of Technology
Abstract
Response spectra of fixed offshore structures impacted by extreme waves are investigated based on the higher order components of the nonlinear drag force. In this way, steel jacket platforms are simplified as a mass attached to a light cantilever cylinder and their corresponding deformation response spectra are estimated by utilizing a generalized single degree of freedom system. Based on the wave data recorded in the Persian Gulf region, extreme wave loading conditions corresponding to different return periods are exerted on the offshore structures. Accordingly, the effect of the higher order components of the drag force is considered and compared to the linearized state for different sea...
Modification of endurance wave analysis based on New-wave theory
, Article Ships and Offshore Structures ; Volume 12, Issue 3 , 2017 , Pages 330-340 ; 17445302 (ISSN) ; Dastan Diznab, M. A ; Mehdigholi, H ; Seif, M. S ; Tabeshpour, M. R ; Sharif University of Technology
Taylor and Francis Ltd
2017
Abstract
The main objective of this investigation is to modify endurance wave analysis (EWA) based on New-wave theory for convenient assessment of offshore structures under extreme waves. EWA is a novel time history based approach to evaluate structural performance in various excitation levels of wave loading by intensifying wave records. In this article, modifications are proposed to determine appropriate time duration and intensifying trend for reliable and practical assessment of offshore structures. In this way, a simplified model of a real jacket platform is utilised to investigate the application of this approach under extreme wave conditions in the Persian Gulf and results are compared with...
Assessment of offshore structures under extreme wave conditions by Modified Endurance Wave Analysis
, Article Marine Structures ; Volume 39 , December , 2014 , Pages 50-69 ; ISSN: 09518339 ; Mohajernassab, S ; Seif, M. S ; Tabeshpour, M. R ; Mehdigholi, H ; Sharif University of Technology
Abstract
Recently, various approaches have been introduced to estimate the response of offshore structures in different sea states by stepwisely intensifying records. In this article, a more practical approach entitled Modified Endurance Wave Analysis (MEWA) considering the random and probabilistic nature of wave loading and utilizing optimal time duration is introduced. Generation procedure of this approach is described based on two practical wave theories: random and constrained new-wave. In addition, assessment of a simplified model representing a typical fixed offshore platform under extreme wave conditions in the Persian Gulf is performed making use of MEWA. A comparative analysis has been also...
Assessment of offshore platforms under extreme waves by probabilistic incremental wave analysis
, Article Journal of Constructional Steel Research ; Volume 67, Issue 5 , 2011 , Pages 759-769 ; 0143974X (ISSN) ; Ebrahimian, H ; Bagheri, V ; Holmas, T ; Sharif University of Technology
2011
Abstract
In this study, a novel probabilistic framework named Probabilistic Incremental Wave Analysis (PIWA) is established in order to assess the performance of jacket offshore platforms under extreme waves. The PIWA can take into account the uncertainties in three main elements consisting of sea state parameters, structural response and collapse capacity. The main advantage of the PIWA approach is reflected in decoupling of the wave hazard and structural analyses via an intermediate variable known as the wave height intensity measure. Despite the fact that most of the uncertainties associated with structural response are concentrated in wave hazard, this will enable the PIWA to estimate the...