Marine Structures最新文献

Experimental and numerical assessment of ultimate strength of a transversally loaded thin-walled deck structure

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-02-27 DOI: 10.1016/j.marstruc.2025.103793

Beatrice Barsotti , Carlo Battini , Marco Gaiotti , Cesare Mario Rizzo , Gianmarco Vergassola

Many studies have been conducted to determine the ultimate strength of axially loaded ship structures at different levels of complexity, considering grillages, stiffened panels, transverse ring frames as well as complete hull blocks, aimed at assessing progressive collapse analysis of the whole hull girder, both analytically and numerically. However, little research has been conducted on the effects that transversal loads can have on relatively thin shell plating, particularly sensitive to buckling phenomena even for rather low loading thresholds. Moreover, the more and more frequent use of higher and higher strength steels makes ship structures slender and, consequently, likely to be even more sensitive to buckling phenomena. In the framework of a research project funded by Fincantieri R&D Department, a full-scale experimental test is performed on a structure simulating a deck portion characterized by a relatively thin plating, such as to induce an early local elastic buckling with a wide post-buckling range, before the ultimate load is reached. Nonlinear finite element analysis is carried out to design the experiment, considering both the nominal and the actual geometry of the structure as obtained by laser scanning the plating and by 3D reconstruction of the stiffeners. The effect of initial plating imperfection and of welding residual stresses on the numerical models has been considered as well, verifying their impact both, on the load end-shortening curve and on the ultimate strength of the panel.

{"title":"Experimental and numerical assessment of ultimate strength of a transversally loaded thin-walled deck structure","authors":"Beatrice Barsotti , Carlo Battini , Marco Gaiotti , Cesare Mario Rizzo , Gianmarco Vergassola","doi":"10.1016/j.marstruc.2025.103793","DOIUrl":"10.1016/j.marstruc.2025.103793","url":null,"abstract":"<div><div>Many studies have been conducted to determine the ultimate strength of axially loaded ship structures at different levels of complexity, considering grillages, stiffened panels, transverse ring frames as well as complete hull blocks, aimed at assessing progressive collapse analysis of the whole hull girder, both analytically and numerically. However, little research has been conducted on the effects that transversal loads can have on relatively thin shell plating, particularly sensitive to buckling phenomena even for rather low loading thresholds. Moreover, the more and more frequent use of higher and higher strength steels makes ship structures slender and, consequently, likely to be even more sensitive to buckling phenomena. In the framework of a research project funded by Fincantieri R&D Department, a full-scale experimental test is performed on a structure simulating a deck portion characterized by a relatively thin plating, such as to induce an early local elastic buckling with a wide post-buckling range, before the ultimate load is reached. Nonlinear finite element analysis is carried out to design the experiment, considering both the nominal and the actual geometry of the structure as obtained by laser scanning the plating and by 3D reconstruction of the stiffeners. The effect of initial plating imperfection and of welding residual stresses on the numerical models has been considered as well, verifying their impact both, on the load end-shortening curve and on the ultimate strength of the panel.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"103 ","pages":"Article 103793"},"PeriodicalIF":4.0,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143511820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Derivation of design S-N curves for butt welds in support structures for wind turbines 风力涡轮机支撑结构对接焊缝设计 S-N 曲线的推导

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-02-17 DOI: 10.1016/j.marstruc.2025.103795

Inge Lotsberg

The fatigue life of welded connections in structures is normally calculated from bi-linear S-N curves presented in design standards, one part S-N curve for the largest stress ranges that can be determined from constant amplitude testing to the left of the fatigue limit and one part S-N curve for stress ranges lower than the fatigue limit that can be determined from variable amplitude fatigue testing. The second curve is governing the calculated fatigue damage for typical long-term stress distributions for marine structures subjected to cyclic loads from wind and waves. In this study fracture mechanics analyses are performed in a relative way to reduce much of the uncertainties present in such analyses to estimate a second part of the S-N curve as function of fatigue crack growth parameters, threshold stress intensity factor, geometry functions and the long-term stress range distribution. The analysis methodology is calibrated to fatigue test data from constant amplitude loading. Based on the performed analyses it is shown that the second part of the design S-N curve for as-welded butt welds can be lifted to a higher level than presented in design standards of today. For structures supporting wind turbines where the Fatigue Limit State is governing design, this may result in reduction in steel weight as compared with existing design S-N curves in standards. This information may also be useful for lifetime extension of existing structures.

{"title":"Derivation of design S-N curves for butt welds in support structures for wind turbines","authors":"Inge Lotsberg","doi":"10.1016/j.marstruc.2025.103795","DOIUrl":"10.1016/j.marstruc.2025.103795","url":null,"abstract":"<div><div>The fatigue life of welded connections in structures is normally calculated from bi-linear S-N curves presented in design standards, one part S-N curve for the largest stress ranges that can be determined from constant amplitude testing to the left of the fatigue limit and one part S-N curve for stress ranges lower than the fatigue limit that can be determined from variable amplitude fatigue testing. The second curve is governing the calculated fatigue damage for typical long-term stress distributions for marine structures subjected to cyclic loads from wind and waves. In this study fracture mechanics analyses are performed in a relative way to reduce much of the uncertainties present in such analyses to estimate a second part of the S-N curve as function of fatigue crack growth parameters, threshold stress intensity factor, geometry functions and the long-term stress range distribution. The analysis methodology is calibrated to fatigue test data from constant amplitude loading. Based on the performed analyses it is shown that the second part of the design S-N curve for as-welded butt welds can be lifted to a higher level than presented in design standards of today. For structures supporting wind turbines where the Fatigue Limit State is governing design, this may result in reduction in steel weight as compared with existing design S-N curves in standards. This information may also be useful for lifetime extension of existing structures.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"102 ","pages":"Article 103795"},"PeriodicalIF":4.0,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143428685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

State estimation method for deepwater drilling riser system based on monitoring information

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-02-12 DOI: 10.1016/j.marstruc.2025.103792

Zhaowei Liu , Xiuquan Liu , Guole Jia , Lumeng Huang , Yuanjiang Chang , Guoming Chen , Xiaoqiang Guo

The state of the deepwater drilling riser system is critical for risk management. Monitoring is the most direct and accurate way to obtain the state. However, the large-scale deepwater drilling riser system makes it difficult to deploy global monitoring instruments, resulting in only local states that can be obtained by monitoring. Obtaining the global state of the deepwater drilling riser system has long been an engineering challenge. A state estimation methodology based on the locally monitored state and prior model of the drilling riser is proposed to solve the challenge. The locally monitored state includes the current state, floating drilling platform motion state, and riser string local acceleration state. The prior model includes the structural mechanics model of the drilling riser and various load models. A backpropagation model based on cross entropy and gradient descent method is established to modify the local prior model according to the locally monitored state. A global state estimation model is established by extending the modified local prior model with the proposed construction strategy. A drilling riser system with a water depth of 1000 m is selected to test the state estimation method. The results show that the proposed state estimation method can effectively estimate the global state of the deepwater drilling riser system. The estimation effect of the drilling riser state caused by the wave is relatively better than that caused by the current. The monitoring location has a significant effect on the estimation results of the drilling riser state caused by the current.

{"title":"State estimation method for deepwater drilling riser system based on monitoring information","authors":"Zhaowei Liu , Xiuquan Liu , Guole Jia , Lumeng Huang , Yuanjiang Chang , Guoming Chen , Xiaoqiang Guo","doi":"10.1016/j.marstruc.2025.103792","DOIUrl":"10.1016/j.marstruc.2025.103792","url":null,"abstract":"<div><div>The state of the deepwater drilling riser system is critical for risk management. Monitoring is the most direct and accurate way to obtain the state. However, the large-scale deepwater drilling riser system makes it difficult to deploy global monitoring instruments, resulting in only local states that can be obtained by monitoring. Obtaining the global state of the deepwater drilling riser system has long been an engineering challenge. A state estimation methodology based on the locally monitored state and prior model of the drilling riser is proposed to solve the challenge. The locally monitored state includes the current state, floating drilling platform motion state, and riser string local acceleration state. The prior model includes the structural mechanics model of the drilling riser and various load models. A backpropagation model based on cross entropy and gradient descent method is established to modify the local prior model according to the locally monitored state. A global state estimation model is established by extending the modified local prior model with the proposed construction strategy. A drilling riser system with a water depth of 1000 m is selected to test the state estimation method. The results show that the proposed state estimation method can effectively estimate the global state of the deepwater drilling riser system. The estimation effect of the drilling riser state caused by the wave is relatively better than that caused by the current. The monitoring location has a significant effect on the estimation results of the drilling riser state caused by the current.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"102 ","pages":"Article 103792"},"PeriodicalIF":4.0,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143387625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

An experimental study on the strain responses of blades and struts of a 5MW semi-submersible floating vertical-axis wind turbine

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-02-10 DOI: 10.1016/j.marstruc.2025.103794

Yingying Jiang , Zhengshun Cheng , Shi Deng , Peng Chen , Lei Liu , Longfei Xiao

A blade and strut strain sensing system is utilized in this study for a floating vertical-axis wind turbine (VAWT) to monitor and measure dynamic strains in the wave basin model test. The floating VAWT concept consists of a 5MW H-type rotor with three straight blades and a semi-submersible platform. The strain sensing system combines the advantages of Fiber Bragg Grating (FBG) sensors and a fiber optic rotary joint (FORJ). Subsequently, a series of model tests are carried out to investigate the strain response characteristics of blades and struts under various environmental conditions. The results show that the strains on blades and struts are affected by wave, wind, and rotor rotational speed, among which the influence of waves is minor. Under combined wind, rotational speed, with/without wave conditions, the increasing wind speed and rotational speed can lead to increases in mean values and oscillations of blade and strut strains, as well as nP (n times per revolution) components. Besides, blade strain is primarily influenced by the 1P (once-per-revolution) component, while strut strain is mainly affected by the 2P (twice-per-revolution) component for the present FBG sensors arrangement. In summary, this study offers valuable insights into the dynamic strain characteristics of blades and struts of floating VAWT under different environmental conditions, contributing to the advancement of floating VAWT model test technology and the validation of future numerical models.

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引用次数: 0

Evaluation of hull girder ultimate strength for dry cargo inland vessels

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-02-07 DOI: 10.1016/j.marstruc.2025.103790

Nemanja Ilić, Nikola Momčilović

Ultimate strength of sea-going ships is investigated in literature and addressed in the rules and regulations of classification societies, where detailed contemporary methods are defined. However, no systematic assessments or developed regulations for evaluating the ultimate strength of inland vessels have been introduced. This is concerning, considering that around 15,000 inland vessels navigate in Europe alone. These vessels are generally prone to longitudinal strength issues as they face specific design, operational and regulatory challenges, such as a large length-to-height ratio, shallow draught navigation, frequent grounding and overloading accidents, an older fleet and fewer regulatory requirements compared to sea-going ships. Therefore, this study presents a pioneering evaluation: it assesses ultimate strength of ten inland vessels, addressing this significant gap in literature. Five methods are employed for the calculation of ultimate strength: IACS defined progressive collapse analysis (PCA), three modified PCA methods according to different formulations for buckling of stiffeners, and a nonlinear finite element method. Moreover, maximum total bending moments are calculated in order to examine the margin between ultimate and service loads. Selected inland vessels are found to be particularly vulnerable to hull girder collapse, with some of them having extremely low or no margin with respect to hull girder collapse, largely due to the buckling of structural elements acting as a consequence of the selection of unique, dispersed and specific structural features. The research specifically emphasizes that vessels with longitudinal framing achieve higher ultimate strengths, offering greater structural safety against hull girder collapse.

{"title":"Evaluation of hull girder ultimate strength for dry cargo inland vessels","authors":"Nemanja Ilić, Nikola Momčilović","doi":"10.1016/j.marstruc.2025.103790","DOIUrl":"10.1016/j.marstruc.2025.103790","url":null,"abstract":"<div><div>Ultimate strength of sea-going ships is investigated in literature and addressed in the rules and regulations of classification societies, where detailed contemporary methods are defined. However, no systematic assessments or developed regulations for evaluating the ultimate strength of inland vessels have been introduced. This is concerning, considering that around 15,000 inland vessels navigate in Europe alone. These vessels are generally prone to longitudinal strength issues as they face specific design, operational and regulatory challenges, such as a large length-to-height ratio, shallow draught navigation, frequent grounding and overloading accidents, an older fleet and fewer regulatory requirements compared to sea-going ships. Therefore, this study presents a pioneering evaluation: it assesses ultimate strength of ten inland vessels, addressing this significant gap in literature. Five methods are employed for the calculation of ultimate strength: IACS defined progressive collapse analysis (PCA), three modified PCA methods according to different formulations for buckling of stiffeners, and a nonlinear finite element method. Moreover, maximum total bending moments are calculated in order to examine the margin between ultimate and service loads. Selected inland vessels are found to be particularly vulnerable to hull girder collapse, with some of them having extremely low or no margin with respect to hull girder collapse, largely due to the buckling of structural elements acting as a consequence of the selection of unique, dispersed and specific structural features. The research specifically emphasizes that vessels with longitudinal framing achieve higher ultimate strengths, offering greater structural safety against hull girder collapse.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"102 ","pages":"Article 103790"},"PeriodicalIF":4.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The tensile armor behavior of unbonded flexible pipes close to end fitting under uniform bending

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-02-01 DOI: 10.1016/j.marstruc.2024.103761

Leilei Dong , Wei Zhao , Yi Huang , Yingying Wang , Qi Zhang , Hongqi Yang

A theoretical model is presented to investigate the impact of end fitting on slip and stress of tensile armors in unbonded flexible pipes under axial tension and uniform bending in the presence of friction. The problem is characterized by a single armor wire helically wound around a cylindrical supporting surface which is subjected to tension and bending. The deviation from the initial helical angle is used to describe the path of the armor as the pipe is stretched and bent. The integral of this angle change gives the lateral displacement of the wire, which is determined by minimizing the energy functional that consists of the strain energy due to axial strain, local bending and torsion, and the energy dissipated by friction. This leads to a variational problem with fixed endpoints. The obtained differential equation is transformed into a boundary value problem, which is solved numerically. The developed model is verified using a finite element (FE) simulation. Comparisons between the model predictions and the FE results regarding the transverse slip and local bending stress demonstrate good correlations. The results also show that the theoretical solutions of axial slip and stress are in good agreements with the numerical outputs when the wire starts from the intrados or extrados points. The verified model is then applied to study the effects of imposed tension, global curvature, friction coefficient and initial polar angle on the transverse bending stress at the end fitting. The results show that the end restraint could cause a significant stress increase in the armor wire at the end fitting vicinity. The response is linear with respect to tension but nonlinear to curvature. Friction could significantly increase the stress at the end fitting compared to the frictionless case. The critical location is on the tensile side of the pipe. The effect of initial hoop position on the axial stress is also studied. The fixed condition has no influence on the axial stress in the tendon close to the end when it starts from the intrados or extrados points.

{"title":"The tensile armor behavior of unbonded flexible pipes close to end fitting under uniform bending","authors":"Leilei Dong , Wei Zhao , Yi Huang , Yingying Wang , Qi Zhang , Hongqi Yang","doi":"10.1016/j.marstruc.2024.103761","DOIUrl":"10.1016/j.marstruc.2024.103761","url":null,"abstract":"<div><div>A theoretical model is presented to investigate the impact of end fitting on slip and stress of tensile armors in unbonded flexible pipes under axial tension and uniform bending in the presence of friction. The problem is characterized by a single armor wire helically wound around a cylindrical supporting surface which is subjected to tension and bending. The deviation from the initial helical angle is used to describe the path of the armor as the pipe is stretched and bent. The integral of this angle change gives the lateral displacement of the wire, which is determined by minimizing the energy functional that consists of the strain energy due to axial strain, local bending and torsion, and the energy dissipated by friction. This leads to a variational problem with fixed endpoints. The obtained differential equation is transformed into a boundary value problem, which is solved numerically. The developed model is verified using a finite element (FE) simulation. Comparisons between the model predictions and the FE results regarding the transverse slip and local bending stress demonstrate good correlations. The results also show that the theoretical solutions of axial slip and stress are in good agreements with the numerical outputs when the wire starts from the intrados or extrados points. The verified model is then applied to study the effects of imposed tension, global curvature, friction coefficient and initial polar angle on the transverse bending stress at the end fitting. The results show that the end restraint could cause a significant stress increase in the armor wire at the end fitting vicinity. The response is linear with respect to tension but nonlinear to curvature. Friction could significantly increase the stress at the end fitting compared to the frictionless case. The critical location is on the tensile side of the pipe. The effect of initial hoop position on the axial stress is also studied. The fixed condition has no influence on the axial stress in the tendon close to the end when it starts from the intrados or extrados points.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"102 ","pages":"Article 103761"},"PeriodicalIF":4.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Generalized closed-form formulae for characterizing the ultimate strength envelope of ship stiffened panels subjected to combined biaxial compression and lateral pressure

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-01-31 DOI: 10.1016/j.marstruc.2025.103789

Dongyang Li , Zhen Chen

Semi-analytical formula derived from numerical or experimental data is universally recognized as a powerful approach in the ultimate limit state (ULS) design of ship structures. However, it is extremely challenging to formulate a unified equation with excellent accuracy, applicability and practicality for characterizing the ultimate strength envelope of ship stiffened panels under combined biaxial compression and lateral pressure using conventional regression techniques. To address this drawback, this paper proposes a novel strategy mainly involving an equivalent sequential loading approach and artificial intelligence method. The FE model and new loading approach are validated based on the reported experimental data and classical proportional loading approach. Then, traditional implicit interaction relationship of the ultimate strength of stiffened panels under biaxial compression is decoupled by using the new loading method. Afterward, ABAQUS non-linear finite element analysis (FEA) incorporated with a Python code is conducted extensively. Influences of the plate aspect ratio, plate slenderness ratio, column slenderness ratio, transverse/longitudinal load and lateral pressure on the longitudinal/transverse ultimate strength (LUS or TUS) are comprehensively examined. In total, 4009 and 2813 datasets are numerically generated to develop two artificial neural network (ANN) models. The derived explicit formulae used to predict the LUS and TUS both reveal positive agreements with FE results (R = 0.993 and 0.999 for the two test sets), and they are eventually implemented in two user-friendly graphical interface tools. Performance of the proposed generalized closed-form formulae is further verified by using the reported experimental data, empirical formulae and numerical results of other scholars. The proposed formulae can effectively address the ultimate strength assessment of stiffened panels under different load combinations, including pure longitudinal/transverse compression, combined longitudinal/transverse compression & lateral pressure, as well as combined biaxial compression & lateral pressure.

{"title":"Generalized closed-form formulae for characterizing the ultimate strength envelope of ship stiffened panels subjected to combined biaxial compression and lateral pressure","authors":"Dongyang Li , Zhen Chen","doi":"10.1016/j.marstruc.2025.103789","DOIUrl":"10.1016/j.marstruc.2025.103789","url":null,"abstract":"<div><div>Semi-analytical formula derived from numerical or experimental data is universally recognized as a powerful approach in the ultimate limit state (ULS) design of ship structures. However, it is extremely challenging to formulate a unified equation with excellent accuracy, applicability and practicality for characterizing the ultimate strength envelope of ship stiffened panels under combined biaxial compression and lateral pressure using conventional regression techniques. To address this drawback, this paper proposes a novel strategy mainly involving an equivalent sequential loading approach and artificial intelligence method. The FE model and new loading approach are validated based on the reported experimental data and classical proportional loading approach. Then, traditional implicit interaction relationship of the ultimate strength of stiffened panels under biaxial compression is decoupled by using the new loading method. Afterward, ABAQUS non-linear finite element analysis (FEA) incorporated with a Python code is conducted extensively. Influences of the plate aspect ratio, plate slenderness ratio, column slenderness ratio, transverse/longitudinal load and lateral pressure on the longitudinal/transverse ultimate strength (LUS or TUS) are comprehensively examined. In total, 4009 and 2813 datasets are numerically generated to develop two artificial neural network (ANN) models. The derived explicit formulae used to predict the LUS and TUS both reveal positive agreements with FE results (<em>R</em> = 0.993 and 0.999 for the two test sets), and they are eventually implemented in two user-friendly graphical interface tools. Performance of the proposed generalized closed-form formulae is further verified by using the reported experimental data, empirical formulae and numerical results of other scholars. The proposed formulae can effectively address the ultimate strength assessment of stiffened panels under different load combinations, including pure longitudinal/transverse compression, combined longitudinal/transverse compression & lateral pressure, as well as combined biaxial compression & lateral pressure.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"102 ","pages":"Article 103789"},"PeriodicalIF":4.0,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143177775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of geometric parameters on ultimate strength of axially-loaded CFDST chord to CFST brace K-joints

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-01-23 DOI: 10.1016/j.marstruc.2025.103780

Seyed Mohammad Reza Hasani , Morteza Naghipour , Mahdi Nematzadeh

The highest punch shear stress levels at concrete-filled double-skin steel tube (CFDST) K-joints form at chord-brace intersecting point. Increasing the section wall thickness of the outer tube at this point enhances the risk of fracture, thus endangers the entire joint. In order to eliminate such shortcoming, the present study proposes an alternative approach of implementing self-consolidating concrete (SCC) in the space between the inner and outer chords, as well as inside the circular hollow section (CHS) brace members, so as to improve load capacity and eliminate main chord plastification. A laboratory experiment followed by a nonlinear parametric finite element (FE) analysis were done to examine the effects of several mechanical and geometric features of an offshore jacket joint members, including core concrete compressive strength (

f_{c}^{'}

), chord effective length-to-diameter ratio (

α = 2 L / D

), brace-to-chord diameter ratio (

β = d / D

), chord radius-to-wall thickness ratio (

γ = D / 2 T

), brace gap ratio (

ζ = g / D

), chord-to-brace angle (

θ

), and brace-to-chord wall thickness ratio (

τ = t / T

) on the overall joint ductility and strength capacity. Findings show that K- joints with a higher chord-brace angle demonstrate lower ductility factors in general. Also, buckling occurs at brace elements while the chord-brace intersecting point remains intact when the CFDST K-joint members are filled with core concrete. Furthermore, joints with concrete infill had almost twice as much peak loads and greater initial stiffness compared to those with no infill concrete, because of the contribution of confined concrete in raising the overall capacity of the CFDST K-joint.

{"title":"Effect of geometric parameters on ultimate strength of axially-loaded CFDST chord to CFST brace K-joints","authors":"Seyed Mohammad Reza Hasani , Morteza Naghipour , Mahdi Nematzadeh","doi":"10.1016/j.marstruc.2025.103780","DOIUrl":"10.1016/j.marstruc.2025.103780","url":null,"abstract":"<div><div>The highest punch shear stress levels at concrete-filled double-skin steel tube (CFDST) K-joints form at chord-brace intersecting point. Increasing the section wall thickness of the outer tube at this point enhances the risk of fracture, thus endangers the entire joint. In order to eliminate such shortcoming, the present study proposes an alternative approach of implementing self-consolidating concrete (SCC) in the space between the inner and outer chords, as well as inside the circular hollow section (CHS) brace members, so as to improve load capacity and eliminate main chord plastification. A laboratory experiment followed by a nonlinear parametric finite element (FE) analysis were done to examine the effects of several mechanical and geometric features of an offshore jacket joint members, including core concrete compressive strength (<span><math><msubsup><mi>f</mi><mi>c</mi><mo>′</mo></msubsup></math></span>), chord effective length-to-diameter ratio (<span><math><mrow><mi>α</mi><mo>=</mo><mn>2</mn><mi>L</mi><mo>/</mo><mi>D</mi></mrow></math></span>), brace-to-chord diameter ratio (<span><math><mrow><mi>β</mi><mo>=</mo><mi>d</mi><mo>/</mo><mi>D</mi></mrow></math></span>), chord radius-to-wall thickness ratio (<span><math><mrow><mi>γ</mi><mo>=</mo><mi>D</mi><mo>/</mo><mn>2</mn><mi>T</mi></mrow></math></span>), brace gap ratio (<span><math><mrow><mi>ζ</mi><mo>=</mo><mi>g</mi><mo>/</mo><mi>D</mi></mrow></math></span>), chord-to-brace angle (<span><math><mi>θ</mi></math></span>), and brace-to-chord wall thickness ratio (<span><math><mrow><mi>τ</mi><mo>=</mo><mi>t</mi><mo>/</mo><mi>T</mi></mrow></math></span>) on the overall joint ductility and strength capacity. Findings show that K- joints with a higher chord-brace angle demonstrate lower ductility factors in general. Also, buckling occurs at brace elements while the chord-brace intersecting point remains intact when the CFDST K-joint members are filled with core concrete. Furthermore, joints with concrete infill had almost twice as much peak loads and greater initial stiffness compared to those with no infill concrete, because of the contribution of confined concrete in raising the overall capacity of the CFDST K-joint.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"102 ","pages":"Article 103780"},"PeriodicalIF":4.0,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143177776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Improved outflow model for oil tankers following collision events and investigation of relevant statistical properties by Monte Carlo simulation

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-01-15 DOI: 10.1016/j.marstruc.2025.103779

V. Piscopo, A. Sciacca

The paper focuses on the development of an improved outflow model for oil tankers following collision events and the investigation of its statistical properties by Monte Carlo simulation. After a review of the most recent advances, a new oil outflow model is developed for double hull oil tankers, based on a time-domain iterative procedure, until hydrostatic equilibrium is reached at outer and inner side openings. The model allows removing the assumptions related to the negligible dimension of the damaged area, the full loading condition of cargo tank and the detachment of the oil spillage event in a set of subsequent phases. The IMO statistics are employed for random generation of collision damage events, under different assumptions concerning the damage dimensions, assumed both uncorrelated and correlated, in the latter case by the employment of Gaussian copula functions. Two oil tankers are considered in a benchmark study, devoted to investigating the oil outflow statistical properties following collision events and comparing them with the relevant values obtained by the IMO model. The incidence of double hull width is investigated and some suggestions for the possible updating of current IMO guidelines are also provided to improve the safety of oil tankers following collision events.

{"title":"Improved outflow model for oil tankers following collision events and investigation of relevant statistical properties by Monte Carlo simulation","authors":"V. Piscopo, A. Sciacca","doi":"10.1016/j.marstruc.2025.103779","DOIUrl":"10.1016/j.marstruc.2025.103779","url":null,"abstract":"<div><div>The paper focuses on the development of an improved outflow model for oil tankers following collision events and the investigation of its statistical properties by Monte Carlo simulation. After a review of the most recent advances, a new oil outflow model is developed for double hull oil tankers, based on a time-domain iterative procedure, until hydrostatic equilibrium is reached at outer and inner side openings. The model allows removing the assumptions related to the negligible dimension of the damaged area, the full loading condition of cargo tank and the detachment of the oil spillage event in a set of subsequent phases. The IMO statistics are employed for random generation of collision damage events, under different assumptions concerning the damage dimensions, assumed both uncorrelated and correlated, in the latter case by the employment of Gaussian copula functions. Two oil tankers are considered in a benchmark study, devoted to investigating the oil outflow statistical properties following collision events and comparing them with the relevant values obtained by the IMO model. The incidence of double hull width is investigated and some suggestions for the possible updating of current IMO guidelines are also provided to improve the safety of oil tankers following collision events.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"101 ","pages":"Article 103779"},"PeriodicalIF":4.0,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Time-domain simulation, fatigue and extreme responses for a fully flexible TLP floating wind turbine

IF 4 2区工程技术 Q1 ENGINEERING, CIVIL

Marine Structures

Pub Date : 2025-01-14 DOI: 10.1016/j.marstruc.2025.103778

Xiaoming Ran, Erin E. Bachynski-Polić

This study explores the dynamic responses of a tension leg platform (TLP) floating wind turbine (FWT) when all components of the floating platform are considered as flexible (elastic). Advanced aero-hydro-servo-elastic models modelling the platform with beam elements, which have been validated with model tests in previous work, are now extended to a TLP with column and pontoons. First, four coupled numerical models were established in the engineering tool SIMA. Two of them represent the entire platform (floater) as a fully flexible body, while the other two treat it as a rigid body for comparison. The tower, blades, and tendons are considered flexible for all models. The hydrodynamic loads are based on either Morison’s equation or potential flow theory, and are distributed along the body in the models with flexible platform. Fully coupled time domain simulations in still water, regular waves, and combined turbulent wind-irregular wave conditions are used to compare global motions and local sectional internal loads at different locations on the platform, tower, and tendons. Both fatigue damage and extreme axial stresses along the structure (obtained using a modified environmental contour approach) are examined. Platform flexibility influences the platform heave and pitch natural periods and motion amplitudes, particularly at the first bending mode natural frequency. Consequently, the sectional loads of all structure members at the first bending natural frequency are largely affected, and tendon axial stress at the wave-frequency also changes significantly. Overall, the adoption of a flexible platform model results in lower fatigue damage and extreme stress prediction along the tower and tendon. For this TLP FWT, Morison’s models predict larger responses for fatigue. For the extreme axial stresses in parked conditions, resonant responses at the first bending mode natural frequency are dominant.

{"title":"Time-domain simulation, fatigue and extreme responses for a fully flexible TLP floating wind turbine","authors":"Xiaoming Ran, Erin E. Bachynski-Polić","doi":"10.1016/j.marstruc.2025.103778","DOIUrl":"10.1016/j.marstruc.2025.103778","url":null,"abstract":"<div><div>This study explores the dynamic responses of a tension leg platform (TLP) floating wind turbine (FWT) when all components of the floating platform are considered as flexible (elastic). Advanced aero-hydro-servo-elastic models modelling the platform with beam elements, which have been validated with model tests in previous work, are now extended to a TLP with column and pontoons. First, four coupled numerical models were established in the engineering tool SIMA. Two of them represent the entire platform (floater) as a fully flexible body, while the other two treat it as a rigid body for comparison. The tower, blades, and tendons are considered flexible for all models. The hydrodynamic loads are based on either Morison’s equation or potential flow theory, and are distributed along the body in the models with flexible platform. Fully coupled time domain simulations in still water, regular waves, and combined turbulent wind-irregular wave conditions are used to compare global motions and local sectional internal loads at different locations on the platform, tower, and tendons. Both fatigue damage and extreme axial stresses along the structure (obtained using a modified environmental contour approach) are examined. Platform flexibility influences the platform heave and pitch natural periods and motion amplitudes, particularly at the first bending mode natural frequency. Consequently, the sectional loads of all structure members at the first bending natural frequency are largely affected, and tendon axial stress at the wave-frequency also changes significantly. Overall, the adoption of a flexible platform model results in lower fatigue damage and extreme stress prediction along the tower and tendon. For this TLP FWT, Morison’s models predict larger responses for fatigue. For the extreme axial stresses in parked conditions, resonant responses at the first bending mode natural frequency are dominant.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"101 ","pages":"Article 103778"},"PeriodicalIF":4.0,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0