The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform
Yong Bai - One of the best experts on this subject based on the ideXlab platform.
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Spectral Fatigue Analysis and Design
Marine Structural Design, 2016Co-Authors: Yong Bai, Wei-liang JinAbstract:This chapter discusses spectral Fatigue analysis (SFA) and design. In Simplified Fatigue Assessment, the Fatigue damage is estimated assuming the long-term stress response follows a Weibull distribution. Fatigue analysis and design include several analysis steps including Fatigue screening, detailed structural analysis, and reanalysis of design improvements, welding improvements, combined design and welding improvements, etc. This chapter describes Fatigue analysis of floating structures, such as SFA including computer modeling, load conditions, structural analysis and validation, loading combinations, and Fatigue damage Assessment; time–domain Fatigue analysis; and Fatigue design of local structural details. This chapter explains that some terms applied in Fatigue analysis have specific meanings. This chapter also discusses SFA, including Fatigue damage acceptance criteria and Fatigue damage calculated using frequency–domain solutions. Time–domain Fatigue Assessment is also discussed in this chapter. This section presents aspects of modeling, load evaluation, and structural analysis applicable to overall structural analysis. These loading conditions include hydrodynamic loads due to waves, including dynamic pressure, and inertial loads due to motions, etc. Symmetrical or asymmetrical load conditions are checked to confirm analytical results. This chapter also discusses effective Fatigue analysis and design.
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Simplified Fatigue Assessment
Marine Structural Design, 2016Co-Authors: Yong Bai, Wei-liang JinAbstract:This chapter discusses Simplified Fatigue Assessment. Fatigue Assessment of structural connections is one of the most critical issues in the design of marine structures such as ships, fixed platforms, floating structures, pipelines, risers, and mooring lines. The results of Fatigue Assessment are influenced by several aspects of cost and safety, including the quality of connection materials, quality of welding fabrication, frequency of inspections and repairs, consequences of potential Fatigue failure, and residual strength of partially damaged structural systems. This chapter describes a Simplified procedure for Fatigue Assessment based on a two-parameter Weibull distribution. The Weibull shape parameter depends on the wave climate and the character of the structural response, especially the possible influence of structural dynamics. Cracks around cutout openings are seen often in many types of ship structures. Past studies have concluded that single-hull tankers experience most of this cracking in side shell and bottom shell areas because of cyclic wave pressure. The chapter discusses Simplified Fatigue Assessment, including calculation of accumulated damage, Weibull stress distribution parameters, Simplified Fatigue Assessment for bilinear S–N curves, and design criteria for connections around cutout openings.
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Fatigue Loading and Stresses
Marine Structural Design, 2016Co-Authors: Yong Bai, Wei-liang JinAbstract:This chapter discusses Fatigue loading and stresses. Marine structures may be exposed to a variety of loads during their life cycles. These are commonly classified as functional (dead and live loads), environmental (sea, wind, and seismic loads), and accidental. Fatigue loading is a key parameter in Fatigue analysis. The objective of this chapter is to present a general procedure for long-term Fatigue stress, described using the Weibull distribution function. In this chapter, Fatigue loads for ship and offshore structures have been discussed for Simplified Fatigue Assessment and spectral Fatigue Assessment. For ship structures, key Fatigue loads are global wave loads, local pressure, and internal loads. These Fatigue loads are applied to a structural response model. The Fatigue loads may be applied using Simplified Fatigue Assessment and spectral Fatigue Assessment. Areas that require future research include calculation of loads that accounts for nonlinearities, development of a theoretical method to combine high- and low-frequency responses, development of a hull-stress monitoring system that may link a ship’s service experience with its anticipated Fatigue failure, and quantification of uncertainty in load predictions, including load combinations. This chapter presents three approaches for the estimation of long-term Fatigue stresses that will be used respectively in subsequent chapters. They are long-term Fatigue stress based on the Weibull distribution, deterministic approach, and stochastic approach.
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Chapter 20 – Spectral Fatigue Analysis and Design
Marine Structural Design, 2003Co-Authors: Yong BaiAbstract:Publisher Summary This chapter discusses spectral Fatigue analysis and design. In the Simplified Fatigue Assessment, the Fatigue damage is estimated assuming that the stress follows a Weibull distribution for the long-term response. The Fatigue analysis and design include several steps of analysis including Fatigue screening, detailed structural analysis, reanalysis of welding improvements, reanalysis of design improvements, and reanalysis of design and welding improvements, etc. This chapter describes a Fatigue analysis of floating structures, such as spectral Fatigue analysis, including computer modeling, load conditions, structural analysis and validation, loading combinations, and Fatigue damage Assessment; time-domain Fatigue analysis; and Fatigue design of local structural details. This chapter explains that some terms applied in Fatigue analysis have specific meanings. This chapter also discusses spectral Fatigue analysis, including Fatigue damage acceptance criteria and Fatigue damage calculated using frequency-domain solution. Time-domain Fatigue Assessment is also made in this chapter. This section presents aspects of modeling, load evaluation, and structural analysis applicable to the overall structural analysis. These loading conditions include hydrodynamic loads due to waves, including dynamic pressure; inertial loads due to motions, etc. Symmetrical or asymmetrical load conditions are checked to confirm symmetrical or asymmetrical analysis results. This chapter also discusses Fatigue analysis and design very effectively.
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Chapter 19 – Simplified Fatigue Assessment
Marine Structural Design, 2003Co-Authors: Yong BaiAbstract:Publisher Summary This chapter discusses Simplified Fatigue Assessment. Fatigue Assessment of structural connections is one of the most critical issues in the design of marine structures, such as ships, fixed platforms, floating structures, pipelines, risers, and mooting lines. The results of Fatigue Assessment will influence costs and safety from several aspects, which includes quality of the connection material, quality of welding fabrication, frequency of inspection and repairs, consequence of potential Fatigue failure, and residual strength of partially damaged structural system. This chapter describes a Simplified procedure for Fatigue Assessment based on a two parameter Weibull distribution. The Weibull shape parameter depends on the wave climate and the character of the structural response, especially the possible influence of structural dynamics. Cracks around cutout openings are often seen in many types of ship structures. Past studies have concluded that single-hull tankers experienced most of these cracking in the side shell and bottom shell areas due to cyclic wave pressure. The chapter discusses Simplified Fatigue Assessment, which includes calculation of accumulated damage, Weibuil stress distribution parameters, Simplified Fatigue Assessment for bilinear S–N Curves, and design criteria for connections around cutout openings.
Wei-liang Jin - One of the best experts on this subject based on the ideXlab platform.
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Spectral Fatigue Analysis and Design
Marine Structural Design, 2016Co-Authors: Yong Bai, Wei-liang JinAbstract:This chapter discusses spectral Fatigue analysis (SFA) and design. In Simplified Fatigue Assessment, the Fatigue damage is estimated assuming the long-term stress response follows a Weibull distribution. Fatigue analysis and design include several analysis steps including Fatigue screening, detailed structural analysis, and reanalysis of design improvements, welding improvements, combined design and welding improvements, etc. This chapter describes Fatigue analysis of floating structures, such as SFA including computer modeling, load conditions, structural analysis and validation, loading combinations, and Fatigue damage Assessment; time–domain Fatigue analysis; and Fatigue design of local structural details. This chapter explains that some terms applied in Fatigue analysis have specific meanings. This chapter also discusses SFA, including Fatigue damage acceptance criteria and Fatigue damage calculated using frequency–domain solutions. Time–domain Fatigue Assessment is also discussed in this chapter. This section presents aspects of modeling, load evaluation, and structural analysis applicable to overall structural analysis. These loading conditions include hydrodynamic loads due to waves, including dynamic pressure, and inertial loads due to motions, etc. Symmetrical or asymmetrical load conditions are checked to confirm analytical results. This chapter also discusses effective Fatigue analysis and design.
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Simplified Fatigue Assessment
Marine Structural Design, 2016Co-Authors: Yong Bai, Wei-liang JinAbstract:This chapter discusses Simplified Fatigue Assessment. Fatigue Assessment of structural connections is one of the most critical issues in the design of marine structures such as ships, fixed platforms, floating structures, pipelines, risers, and mooring lines. The results of Fatigue Assessment are influenced by several aspects of cost and safety, including the quality of connection materials, quality of welding fabrication, frequency of inspections and repairs, consequences of potential Fatigue failure, and residual strength of partially damaged structural systems. This chapter describes a Simplified procedure for Fatigue Assessment based on a two-parameter Weibull distribution. The Weibull shape parameter depends on the wave climate and the character of the structural response, especially the possible influence of structural dynamics. Cracks around cutout openings are seen often in many types of ship structures. Past studies have concluded that single-hull tankers experience most of this cracking in side shell and bottom shell areas because of cyclic wave pressure. The chapter discusses Simplified Fatigue Assessment, including calculation of accumulated damage, Weibull stress distribution parameters, Simplified Fatigue Assessment for bilinear S–N curves, and design criteria for connections around cutout openings.
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Fatigue Loading and Stresses
Marine Structural Design, 2016Co-Authors: Yong Bai, Wei-liang JinAbstract:This chapter discusses Fatigue loading and stresses. Marine structures may be exposed to a variety of loads during their life cycles. These are commonly classified as functional (dead and live loads), environmental (sea, wind, and seismic loads), and accidental. Fatigue loading is a key parameter in Fatigue analysis. The objective of this chapter is to present a general procedure for long-term Fatigue stress, described using the Weibull distribution function. In this chapter, Fatigue loads for ship and offshore structures have been discussed for Simplified Fatigue Assessment and spectral Fatigue Assessment. For ship structures, key Fatigue loads are global wave loads, local pressure, and internal loads. These Fatigue loads are applied to a structural response model. The Fatigue loads may be applied using Simplified Fatigue Assessment and spectral Fatigue Assessment. Areas that require future research include calculation of loads that accounts for nonlinearities, development of a theoretical method to combine high- and low-frequency responses, development of a hull-stress monitoring system that may link a ship’s service experience with its anticipated Fatigue failure, and quantification of uncertainty in load predictions, including load combinations. This chapter presents three approaches for the estimation of long-term Fatigue stresses that will be used respectively in subsequent chapters. They are long-term Fatigue stress based on the Weibull distribution, deterministic approach, and stochastic approach.
Nikiforakis Ioannis - One of the best experts on this subject based on the ideXlab platform.
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Determination of Fatigue Assessment of Monopile - Based Offshore Wind Turbines through Fidelity Quantification
2017Co-Authors: Nikiforakis IoannisAbstract:The application of stability checks in simulated offshore wind structures is performed through tools that are established in the offshore wind industry. In particular, the structure should fulfill certain strength and Fatigue criteria among which Fatigue Limit States (FLSs) checks are critical. In terms of the process, Fatigue Assessment can be carried out in both time (TD) and frequency domain (FD), with the former being more popular in the offshore wind energy sector. Nevertheless, Simplified tools in the FD have been suggested, since they yield results similar to those of the TD analysis. In order to decide upon the choice of tool in performing the FLS estimations, a relative comparison should be implemented. Particularly, Fatigue Assessment in the TD, Fatigue Assessment in the FD and a Simplified type of Fatigue Assessment in the FD are examined. These types of Fatigue Assessment are conducted in three respective tools, with the TD type conducted in NREL’s FAST v8 and both the FD types simulated within MATLAB tools. The tools are judged upon the desirable levels of Modelling & Simulation (M&S) fidelity. A set of criteria are defined for the particular use case, in an attempt to express that fidelity. The criteria’s metrics are additionally provided in the proposed methodology and associated measurements are taken during simulations. Only after conducting further multi-criteria decision analyses (MCDA), the eventual levels of fidelity for the three types of Fatigue Assessment result to a consequent ranking among the tools. Therefore, the measured criteria lead to the quantification of these levels of fidelity for all three tools and the application of MCDA results to their ranking. The proposed fidelity framework is applied in a case study in order to evaluate the proposed methodology, as well as to select the type of Fatigue Assessment and consequent tool that should be used within an early design stage. The results indicate that the Simplified Fatigue Assessment in the FD should be preferred over conventional Fatigue Assessment in both TD & FD. In addition, the criteria included in the fidelity framework seem to provide a multifaceted approach, since none of the tools is favored in all categories. Finally, similarities in results between relevant types of conducted comparisons as well as between different types of MCDA, enhance the consistency of the proposed fidelity methodology and increase its credibility.Aerospace Engineering | Aerodynamics and Wind Energ
M.b. Zaayer - One of the best experts on this subject based on the ideXlab platform.
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Simplified Fatigue Assessment of offshore wind support structures accounting for variations in a farm (poster)
2015Co-Authors: M. Michalopoulos, M.b. ZaayerAbstract:Provided the significant contribution of support structures to the capital expenditures of offshore wind, optimisation schemes are often developed to address the need for tailored design of different structures in one farm. A crucial aspect of them is, among others, the Fatigue Limit State (FLS)1234 .To this direction, research is conducted on the response of the structure to cyclic loading in the frequency-domain567 . However, the complexity and the need for advanced software (finite element and/or aero-elastic codes) often limit the flexibility. As a consequence, the design process is not facilitated significantly. The focus of this study is principally placed on the impact that variations in an offshore wind farm (OWF) have on the support structures, particularly on their resistance to cumulative damage caused by wind and wave loading. The vital requirement is therefore that the procedure is computationally affordable to ensure applicability for the early design phase of multiple structures. The goal of this study is to develop such a procedure.
Ioannis Nikiforakis - One of the best experts on this subject based on the ideXlab platform.
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Determination of Fatigue Assessment of Monopile - Based Offshore Wind Turbines through Fidelity Quantification
2017Co-Authors: Ioannis NikiforakisAbstract:The application of stability checks in simulated offshore wind structures is performed through tools that are established in the offshore wind industry. In particular, the structure should fulfill certain strength and Fatigue criteria among which Fatigue Limit States (FLSs) checks are critical. In terms of the process, Fatigue Assessment can be carried out in both time (TD) and frequency domain (FD), with the former being more popular in the offshore wind energy sector. Nevertheless, Simplified tools in the FD have been suggested, since they yield results similar to those of the TD analysis. In order to decide upon the choice of tool in performing the FLS estimations, a relative comparison should be implemented. Particularly, Fatigue Assessment in the TD, Fatigue Assessment in the FD and a Simplified type of Fatigue Assessment in the FD are examined. These types of Fatigue Assessment are conducted in three respective tools, with the TD type conducted in NREL’s FAST v8 and both the FD types simulated within MATLAB tools. The tools are judged upon the desirable levels of Modelling a Simulation (MaS) fidelity. A set of criteria are defined for the particular use case, in an attempt to express that fidelity. The criteria’s metrics are additionally provided in the proposed methodology and associated measurements are taken during simulations. Only after conducting further multi-criteria decision analyses (MCDA), the eventual levels of fidelity for the three types of Fatigue Assessment result to a consequent ranking among the tools. Therefore, the measured criteria lead to the quantification of these levels of fidelity for all three tools and the application of MCDA results to their ranking. The proposed fidelity framework is applied in a case study in order to evaluate the proposed methodology, as well as to select the type of Fatigue Assessment and consequent tool that should be used within an early design stage. The results indicate that the Simplified Fatigue Assessment in the FD should be preferred over conventional Fatigue Assessment in both TD a FD. In addition, the criteria included in the fidelity framework seem to provide a multifaceted approach, since none of the tools is favored in all categories. Finally, similarities in results between relevant types of conducted comparisons as well as between different types of MCDA, enhance the consistency of the proposed fidelity methodology and increase its credibility.