Pub Date : 2025-03-06DOI: 10.1016/j.marstruc.2025.103796
Li Yin , Dongsheng Qiao , Guoguang Sun , Pengfei Liu , Guoqiang Tang , Lin Lu , Jinping Ou
The blade installation system using the floating installation vessel comprises several parts, including the vessel equipped with the dynamic positioning system, the ship-mounted crane, and the double pendulum system. The interaction within the system will significantly impact the dynamic responses of the blade. To analyze the coupling responses of each part, the model-based design method is employed. The hydrodynamic analysis module of the installation vessel is built by the Cummins method, the kinematic module is constructed by the coordinate transformation and the double pendulum model, as well as the dynamic module is developed by the Lagrangian method. The aforementioned modules are integrated to develop the analysis program. By code-to-code comparison, the dynamic responses of the entire installation process can be accurately assessed by the program when the forces on the blade as well as the motion of installation vessel and ship-mounted crane are considered. In addition, the program can effectively improve calculation efficiency. In Part II of this paper, the dynamic responses of blade installation system are analyzed.
{"title":"Dynamic response analysis of the installation system during hoisting and mating phases using a floating vessel. Part Ⅰ: Model formulation and verification","authors":"Li Yin , Dongsheng Qiao , Guoguang Sun , Pengfei Liu , Guoqiang Tang , Lin Lu , Jinping Ou","doi":"10.1016/j.marstruc.2025.103796","DOIUrl":"10.1016/j.marstruc.2025.103796","url":null,"abstract":"<div><div>The blade installation system using the floating installation vessel comprises several parts, including the vessel equipped with the dynamic positioning system, the ship-mounted crane, and the double pendulum system. The interaction within the system will significantly impact the dynamic responses of the blade. To analyze the coupling responses of each part, the model-based design method is employed. The hydrodynamic analysis module of the installation vessel is built by the Cummins method, the kinematic module is constructed by the coordinate transformation and the double pendulum model, as well as the dynamic module is developed by the Lagrangian method. The aforementioned modules are integrated to develop the analysis program. By code-to-code comparison, the dynamic responses of the entire installation process can be accurately assessed by the program when the forces on the blade as well as the motion of installation vessel and ship-mounted crane are considered. In addition, the program can effectively improve calculation efficiency. In Part II of this paper, the dynamic responses of blade installation system are analyzed.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"103 ","pages":"Article 103796"},"PeriodicalIF":4.0,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143552054","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}
Pub Date : 2025-03-03DOI: 10.1016/j.marstruc.2025.103797
A.R. Damanpack
In this paper, a novel approach is presented to improve the accuracy and reduce the computational time of the finite element analysis of massive lattice structures. To achieve these goals, the global structure is discretized based on the beam elements while joint connections are replaced with joint elements. Then, the proposed joint element matrices are formulated in the local model with solid elements and consequently formed according to the beam theory. The present formulation is able to impose the details of joint connections in the global matrices. To verify and evaluate the proposed model, the numerical results of various cases are compared with ANSYS and those reported in the open literature. Moreover, a special study on the real-life offshore jacket structure has been carried out subjected to static loads and free vibrations. The comparison study shows the consistency of joint elements in both mass and stiffness matrices by reducing errors significantly to 0 % and 5 % while the error of using only beam elements reaches up to 300 % in some cases. It is concluded that the present approach can be efficiently implemented for the modeling of 3D massive lattice structures with reasonable accuracy and computational time.
{"title":"A new finite joint element to model joint connections in offshore structures","authors":"A.R. Damanpack","doi":"10.1016/j.marstruc.2025.103797","DOIUrl":"10.1016/j.marstruc.2025.103797","url":null,"abstract":"<div><div>In this paper, a novel approach is presented to improve the accuracy and reduce the computational time of the finite element analysis of massive lattice structures. To achieve these goals, the global structure is discretized based on the beam elements while joint connections are replaced with joint elements. Then, the proposed joint element matrices are formulated in the local model with solid elements and consequently formed according to the beam theory. The present formulation is able to impose the details of joint connections in the global matrices. To verify and evaluate the proposed model, the numerical results of various cases are compared with ANSYS and those reported in the open literature. Moreover, a special study on the real-life offshore jacket structure has been carried out subjected to static loads and free vibrations. The comparison study shows the consistency of joint elements in both mass and stiffness matrices by reducing errors significantly to 0 % and 5 % while the error of using only beam elements reaches up to 300 % in some cases. It is concluded that the present approach can be efficiently implemented for the modeling of 3D massive lattice structures with reasonable accuracy and computational time.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"103 ","pages":"Article 103797"},"PeriodicalIF":4.0,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143528964","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}
Pub Date : 2025-02-27DOI: 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}
Pub Date : 2025-02-17DOI: 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}
Pub Date : 2025-02-12DOI: 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}
Pub Date : 2025-02-10DOI: 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.
{"title":"An experimental study on the strain responses of blades and struts of a 5MW semi-submersible floating vertical-axis wind turbine","authors":"Yingying Jiang , Zhengshun Cheng , Shi Deng , Peng Chen , Lei Liu , Longfei Xiao","doi":"10.1016/j.marstruc.2025.103794","DOIUrl":"10.1016/j.marstruc.2025.103794","url":null,"abstract":"<div><div>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 <em>n</em>P (<em>n</em> 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.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"102 ","pages":"Article 103794"},"PeriodicalIF":4.0,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143379329","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}
Pub Date : 2025-02-07DOI: 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}
Pub Date : 2025-02-01DOI: 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}
Pub Date : 2025-01-31DOI: 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}
Pub Date : 2025-01-23DOI: 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 (), chord effective length-to-diameter ratio (), brace-to-chord diameter ratio (), chord radius-to-wall thickness ratio (), brace gap ratio (), chord-to-brace angle (), and brace-to-chord wall thickness ratio () 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}
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