Research

Jump to: Review

16 pages, 11290 KiB

Open AccessArticle

An Efficient Monte-Carlo Simulation for the Dynamic Reliability Analysis of Jacket Platforms Subjected to Random Wave Loads

by Wei Lin and Cheng Su

J. Mar. Sci. Eng. 2021, 9(4), 380; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9040380 - 02 Apr 2021

Cited by 6 | Viewed by 1991

Abstract

The growing demand for the application of jacket platforms in deep water requires more attention on the assessment of structural reliability. This paper is devoted to the dynamic reliability analysis of jacket platforms subjected to random wave loads with the Monte-Carlo simulation (MCS), [...] Read more.

The growing demand for the application of jacket platforms in deep water requires more attention on the assessment of structural reliability. This paper is devoted to the dynamic reliability analysis of jacket platforms subjected to random wave loads with the Monte-Carlo simulation (MCS), in which a sample size of the order of magnitude of 10⁴ to 10⁵ for repeated time–history analyses is required for small failure probability problems, and a duration time up to three hours needs to be considered in the time–history analyses for a specific sea condition. To tackle the difficulty involved in the MCS, the explicit time-domain method (ETDM) is used for the required time–history analyses of jacket platforms, in which truncated explicit expressions of critical responses with regards to the contributing loading terms are first established and then used for numerous repeated sample analyses. The use of ETDM greatly enhances the computational efficiency of MCS, making it feasible for the dynamic reliability analysis of jacket platforms under random wave loads. A jacket platform with 11,688 degrees of freedom was analyzed for the evaluation of dynamic reliability under a given sea condition, indicating the accuracy and efficiency of the present approach and its feasibility to practical structures. Full article

(This article belongs to the Special Issue Offshore and Subsea Structures)

► Show Figures

Figure 1

26 pages, 8022 KiB

Open AccessArticle

ROMS Based Hydrodynamic Modelling Focusing on the Belgian Part of the Southern North Sea

by Georgios Klonaris, Frans Van Eeden, Jeffrey Verbeurgt, Peter Troch, Denis Constales, Hans Poppe and Alain De Wulf

J. Mar. Sci. Eng. 2021, 9(1), 58; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010058 - 07 Jan 2021

Cited by 6 | Viewed by 3116

Abstract

The North Sea is a shallow sea that forms a complex physical system. The nonlinear interaction of the astronomical tides, varying wind fields and varying pressure systems requires appropriate approaches to be described accurately. An application based on the advanced numerical model Regional [...] Read more.

The North Sea is a shallow sea that forms a complex physical system. The nonlinear interaction of the astronomical tides, varying wind fields and varying pressure systems requires appropriate approaches to be described accurately. An application based on the advanced numerical model Regional Ocean Modeling System (ROMS) was newly developed by the authors, tailored to simulate these hydrodynamic processes in the North Sea and the Belgian Continental Shelf, which is the area of particular interest in the present study. The purpose of this work is to develop and validate a state-of-the-art three-dimensional numerical model to form the basis of a compound operational and forecasting tool for the Belgian coastal zone. The model was validated with respect to water levels and temperature. Validation for astronomical tides was accomplished through the comparison of the principal constituents between the model results and observations at a number of tidal gauges in Belgium and other countries. A statistical analysis of the results showed that the model behaves as expected throughout the North Sea. The model response to the varying meteorological conditions was also validated using hindcast data for 2011 as input. In this case, the comparison between observed and modelled water levels showed a good agreement with average RMSE in Belgium 9.5 cm. Overall, the added value of this work is the development of an independent model for validation and comparison with other models and which can be used as an efficient tool for operational and forecasting purposes. Full article

(This article belongs to the Special Issue Offshore and Subsea Structures)

► Show Figures

Figure 1

24 pages, 18485 KiB

Open AccessArticle

Development of a Comparison Framework for Evaluating Environmental Contours of Extreme Sea States

by Aubrey Eckert, Nevin Martin, Ryan G. Coe, Bibiana Seng, Zacharia Stuart and Zachary Morrell

J. Mar. Sci. Eng. 2021, 9(1), 16; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010016 - 25 Dec 2020

Cited by 9 | Viewed by 2872

Abstract

Environmental contours of extreme sea states are often utilized for the purposes of reliability-based offshore design. Many methods have been proposed to estimate environmental contours of extreme sea states, including, but not limited to, the traditional inverse first-order reliability method (I-FORM) and subsequent [...] Read more.

Environmental contours of extreme sea states are often utilized for the purposes of reliability-based offshore design. Many methods have been proposed to estimate environmental contours of extreme sea states, including, but not limited to, the traditional inverse first-order reliability method (I-FORM) and subsequent modifications, copula methods, and Monte Carlo methods. These methods differ in terms of both the methodology selected for defining the joint distribution of sea state parameters and in the method used to construct the environmental contour from the joint distribution. It is often difficult to compare the results of proposed methods to determine which method should be used for a particular application or geographical region. The comparison of the predictions from various contour methods at a single site and across many sites is important to making environmental contours of extreme sea states useful in practice. The goal of this paper is to develop a comparison framework for evaluating methods for developing environmental contours of extreme sea states. This paper develops generalized metrics for comparing the performance of contour methods to one another across a collection of study sites, and applies these metrics and methods to develop conclusions about trends in the wave resource across geographic locations, as demonstrated for a pilot dataset. These proposed metrics and methods are intended to judge the environmental contours themselves relative to other contour methods, and are thus agnostic to a specific device, structure, or field of application. The metrics developed and applied in this paper include measures of predictive accuracy, physical validity, and aggregated temporal performance that can be used to both assess contour methods and provide recommendations for the use of certain methods in various geographical regions. The application and aggregation of the metrics proposed in this paper outline a comparison framework for environmental contour methods that can be applied to support design analysis workflows for offshore structures. This comparison framework could be extended in future work to include additional metrics of interest, potentially including those to address issues pertinent to a specific application area or analysis discipline, such as metrics related to structural response across contour methods or additional physics-based metrics based on wave dynamics. Full article

(This article belongs to the Special Issue Offshore and Subsea Structures)

► Show Figures

Figure 1

25 pages, 5995 KiB

Open AccessArticle

Re-Evaluation of Fatigue Thickness Effect Based on Fatigue Test Database

by Wangwen Zhao and Wei-Ting Hsu

J. Mar. Sci. Eng. 2020, 8(11), 895; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse8110895 - 10 Nov 2020

Cited by 5 | Viewed by 4266

Abstract

This paper reassesses the detrimental effect on fatigue performance of welded structural steel joints due to thicker sections based on an extensive fatigue strength test database, taken from research programmes worldwide over the past half century, mostly from the offshore oil and gas [...] Read more.

This paper reassesses the detrimental effect on fatigue performance of welded structural steel joints due to thicker sections based on an extensive fatigue strength test database, taken from research programmes worldwide over the past half century, mostly from the offshore oil and gas and marine industries. The data entries in the database were evaluated to ensure its data integrity. Statistical analyses on these S-N data were performed with or without the thickness correction at different exposure levels to a corrosive environment, in order to re-evaluate the suitability of current standards in regard to the thickness effect. The study concentrated on T-joints, transverse butt-welded joints and tubular joints, as these are the most commonly used joint types in the offshore wind industry. The analysis indicates a general agreement of fatigue strength with the thickness effects in current standards for in-air conditions, but great conservatism for corrosive environments. In addition, the statistical models determined in this study can be used for a broader range of studies, such as probabilistic fatigue analysis. Full article

(This article belongs to the Special Issue Offshore and Subsea Structures)

► Show Figures

Figure 1

20 pages, 6210 KiB

Open AccessArticle

Updating the Distributions of Uncertain Parameters Involved in Fatigue Analysis

by Hadi Khalili, Selda Oterkus, Nigel Barltrop and Ujjwal Bharadwaj

J. Mar. Sci. Eng. 2020, 8(10), 778; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse8100778 - 04 Oct 2020

Cited by 4 | Viewed by 1438

Abstract

Fatigue is an important failure mode in offshore jacket platforms. To evaluate the fatigue damage, these platforms are periodically inspected during their lifetime. Regarding fatigue damage, the information from inspection consists of crack measurement. A Bayesian framework can be used to update the [...] Read more.

Fatigue is an important failure mode in offshore jacket platforms. To evaluate the fatigue damage, these platforms are periodically inspected during their lifetime. Regarding fatigue damage, the information from inspection consists of crack measurement. A Bayesian framework can be used to update the probability distribution of the crack size. The main purpose of this study is to develop a framework to update the probability distributions of all uncertain parameters involved in the fatigue crack growth analysis. This methodology maximizes the benefit of the inspection results by updating several uncertain parameters involved in the fracture mechanics approach. Two sets of cracks are used to obtain the updated distributions for uncertain parameters; prior cracks and simulated reality cracks. By comparing these cracks, the updated distributions for uncertain parameters are obtained. The updated crack size distribution can be used to update the estimation of the probability of failure. To demonstrate the developed framework, a tubular joint in a specific jacket platform is considered and the framework is applied for that joint. The results of the developed methodology indicate that the updated distributions of uncertain parameters shift towards the simulated reality distributions. Full article

(This article belongs to the Special Issue Offshore and Subsea Structures)

► Show Figures

Figure 1

18 pages, 4902 KiB

Open AccessArticle

Recent Developments on the Unified Fatigue Life Prediction Method Based on Fracture Mechanics and its Applications

by Fang Wang and Weicheng Cui

J. Mar. Sci. Eng. 2020, 8(6), 427; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse8060427 - 11 Jun 2020

Cited by 6 | Viewed by 2967

Abstract

Safety analysis and prediction of a marine structure is of great concern by many stakeholders and the general public. In order to accurately predict the structural reliability of an in-use marine structure, one needs to calculate accurately the fatigue crack growth at any [...] Read more.

Safety analysis and prediction of a marine structure is of great concern by many stakeholders and the general public. In order to accurately predict the structural reliability of an in-use marine structure, one needs to calculate accurately the fatigue crack growth at any service time. This can only be possible by using fracture mechanics approach and the core of fracture-mechanics-based method is to establish an accurate crack growth rate model which must include all the influential factors of the same order of sensitivity index. In 2011, based on the analysis of various influencing factors, the authors put forward a unified fatigue life prediction (UFLP) method for marine structures. In the following ten years of research, some further improvements of this method have been made and the applications of this UFLP are carried out. In this paper, these progresses are reported and its underlying principles are further elaborated. Some basic test data used to determine model parameters are also provided. Full article

(This article belongs to the Special Issue Offshore and Subsea Structures)

► Show Figures

Figure 1

23 pages, 5812 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Conceptual Design and Numerical Analysis of a Novel Floating Desalination Plant Powered by Marine Renewable Energy for Egypt

by Islam Amin, Mohamed E.A. Ali, Seif Bayoumi, Selda Oterkus, Hosam Shawky and Erkan Oterkus

J. Mar. Sci. Eng. 2020, 8(2), 95; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse8020095 - 04 Feb 2020

Cited by 26 | Viewed by 5825

Abstract

The supply of freshwater has become a worldwide interest, due to serious water shortages in many countries. Due to rapid increases in the population, poor water management, and limitations of freshwater resources, Egypt is currently below the water scarcity limit. Since Egypt has [...] Read more.

The supply of freshwater has become a worldwide interest, due to serious water shortages in many countries. Due to rapid increases in the population, poor water management, and limitations of freshwater resources, Egypt is currently below the water scarcity limit. Since Egypt has approximately 3000 km of coastlines on both the Red Sea and the Mediterranean Sea, seawater desalination powered by marine renewable energy could be a sustainable alternative solution, especially for remote coastal cities which are located far from the national water grid. The objective of this research work is to evaluate the feasibility of a floating desalination plant (FDP) concept powered by marine renewable energy for Egypt. A novel design of the FDP concept is developed as an innovative solution to overcome the freshwater shortage of remote coastal cities in Egypt. A mobile floating platform supported by reverse osmosis (RO) membrane powered by marine renewable power technology is proposed. Based on the abundant solar irradiation and sufficient wind density, Ras Ghareb was selected to be the base site location for the proposed FDP concept. According to the collected data from the selected location, a hybrid solar–wind system was designed to power the FDP concept under a maximum power load condition. A numerical tool, the DNV-GL Sesam software package, was used for static stability, hydrodynamic performance, and dynamic response evaluation. Moreover, WAVE software was used to design and simulate the operation of the RO desalination system and calculate the power consumption for the proposed FDP concept. The results show that the proposed mobile FDP concept is highly suitable for being implemented in remote coastal areas in Egypt, without the need for infrastructure or connection to the national grid for both water and power. Full article

(This article belongs to the Special Issue Offshore and Subsea Structures)

► Show Figures

Figure 1

11 pages, 5263 KiB

Open AccessArticle

Numerical Simulation of Flow Control around a Circular Cylinder by Installing a Wedge-Shaped Device Upstream

by Xiaoshuang Han, Jie Wang, Bo Zhou, Guiyong Zhang and Soon-Keat Tan

J. Mar. Sci. Eng. 2019, 7(12), 422; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse7120422 - 20 Nov 2019

Cited by 9 | Viewed by 2438

Abstract

The effect of a triangular wedge upstream of a circular cylinder has been investigated, and the findings are presented herein. The triangular wedge is equilateral in plan form, and the Reynolds number based on the diameter of the main cylinder is approximately 200. [...] Read more.

The effect of a triangular wedge upstream of a circular cylinder has been investigated, and the findings are presented herein. The triangular wedge is equilateral in plan form, and the Reynolds number based on the diameter of the main cylinder is approximately 200. Contours of vorticity clearly show that two entirely different wake patterns exist between the wedge and the main cylinder. There also exists a critical spacing ratio and side length ratio at which the wake flow pattern shifts from one within the cavity mode to one within the wake impingement mode. For a relatively small side length ratio of

l_{w} / D

= 0.20 and 0.27, where the side length refers to the length of one side of the triangular wedge, the drag and lift coefficients decrease monotonically with the spacing ratio. There is a sudden jump of the drag and lift coefficients at larger side length ratios of

l_{w} / D

= 0.33 and 0.40. This study shows that at a spacing ratio of L/D = 2.8 (where L is the distance between the vertex of the wedge and the center of the cylinder) and a wedge side length of

l_{w} / D

= 0.40, the reduction of the amplitude of lift and mean drag coefficient on the main cylinder are 71.9% and 60.1%, respectively. Full article

(This article belongs to the Special Issue Offshore and Subsea Structures)

► Show Figures

Figure 1

Review

Jump to: Research

22 pages, 8725 KiB

Open AccessReview

Surface Crack Growth in Offshore Metallic Pipes under Cyclic Loads: A Literature Review

by Zongchen Li, Xiaoli Jiang and Hans Hopman

J. Mar. Sci. Eng. 2020, 8(5), 339; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse8050339 - 10 May 2020

Cited by 16 | Viewed by 4483

Abstract

The surface crack, also known as the partly through-thickness crack, is a serious threat to the structural integrity of offshore metallic pipes. In this paper, we review the research progress in regard to surface crack growth in metallic pipes subjected to cyclic loads [...] Read more.

The surface crack, also known as the partly through-thickness crack, is a serious threat to the structural integrity of offshore metallic pipes. In this paper, we review the research progress in regard to surface crack growth in metallic pipes subjected to cyclic loads from the fracture mechanics perspective. The purpose is to provide state-of-the-art investigations, as well as indicate the remaining challenges. First, the available studies on surface cracked metallic pipes are overviewed from experimental, numerical, and analytical perspectives, respectively. Then, we analyse state-of-the-art research and discuss the insufficiencies of the available literature from different perspectives, such as surface cracks and pipe configurations, environmental influential parameters, the girth welding effect, and numerical and analytical evaluation methods. Building on these surveys and discussions, we identify various remaining challenges and possible further research topics that are anticipated to be of significant value both for academics and practitioners. Full article

(This article belongs to the Special Issue Offshore and Subsea Structures)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Offshore and Subsea Structures

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (9 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI