A numerical study on flow over a stationary deep-draft semi-submersible (DDS) with various corner shapes was carried out to investigate the corner shape effects on the overall hydrodynamics. Three models based on a typical DDS design with different corner shapes were numerically investigated under 45° incidence. The present numerical model has been validated by an experimental test carried out in a circulating water channel. It is demonstrated that, as the corner shape design changed, the hydrodynamic characteristics alter drastically. In addition, the flow patterns were examined to reveal some insights of the fluid physics due to the changing of different corner shape designs. The detailed numerical results from the geometric study will provide a good guidance for future practical designs.
{"title":"Hydrodynamics Around a Deep-Draft Semi-Submersible With Various Corner Shapes","authors":"Yibo Liang, L. Tao","doi":"10.1115/OMAE2018-77135","DOIUrl":"https://doi.org/10.1115/OMAE2018-77135","url":null,"abstract":"A numerical study on flow over a stationary deep-draft semi-submersible (DDS) with various corner shapes was carried out to investigate the corner shape effects on the overall hydrodynamics. Three models based on a typical DDS design with different corner shapes were numerically investigated under 45° incidence. The present numerical model has been validated by an experimental test carried out in a circulating water channel. It is demonstrated that, as the corner shape design changed, the hydrodynamic characteristics alter drastically. In addition, the flow patterns were examined to reveal some insights of the fluid physics due to the changing of different corner shape designs. The detailed numerical results from the geometric study will provide a good guidance for future practical designs.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"77 Suppl 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134482467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chao-qun Sun, Xiaowei Feng, S. Gourvenec, S. R. Neubecker, M. Randolph
The embedded portion of a mooring line plays an important role for efficient and economic design of an overall mooring system. This paper presents a methodology for numerical simulation of the behaviour of an embedded anchor chain as it cuts through the soil, focusing on the tensioning of a catenary mooring. The Coupled Eulerian–Lagrangian (CEL) approach within ABAQUS is used to capture the interaction between the embedded chain (Lagrangian structure) and the soil (Eulerian material). The anchor chain is simulated by a series of rigid cylindrical segments connected together by LINK connectors. Before analysing the global behaviour of an embedded chain, a calibration exercise is undertaken where a straight multi-link portion of the chain is displaced normally and axially in soil. The resulting normal and frictional resistances (per unit length) are compared with those adopted in general practice, in order to calibrate the relationship between the diameter of the cylindrical segments and the bar diameter of the chain. After that, the tensioning process of an anchor chain is simulated, starting from an initial configuration with a 9 m length embedded vertically (attached to a fixed padeye), with the remaining length lying on the seabed. Horizontal tensioning of the chain causes it to cut through the soil until it forms an inverse catenary with an angle of just under 35 degrees to the horizontal at the padeye (and zero degrees at the mudline). The loading curve, and also the inverse catenary profile of the chain for different angles at the padeye, are shown to agree well with the Neubecker-Randolph closed-form analytical solution. However, the ratio of the tensions at the padeye and the mudline from the CEL results differs significantly from the analytical solution. Insights from the CEL results indicate that this is because the frictional soil resistance is not fully mobilised, particularly for the portion of the chain in the stronger soil at depth, near the padeye, where the axial displacements are small. This result has significant implications for the geotechnical design of anchoring systems that involve a (nominally) fixed padeye. The simulation methodology also has considerable potential for exploring the creation of an open trench adjacent to a fixed anchor due to monotonic and cyclic perturbations of the anchor chain.
{"title":"Finite Element Simulation of an Embedded Anchor Chain","authors":"Chao-qun Sun, Xiaowei Feng, S. Gourvenec, S. R. Neubecker, M. Randolph","doi":"10.1115/OMAE2018-77781","DOIUrl":"https://doi.org/10.1115/OMAE2018-77781","url":null,"abstract":"The embedded portion of a mooring line plays an important role for efficient and economic design of an overall mooring system. This paper presents a methodology for numerical simulation of the behaviour of an embedded anchor chain as it cuts through the soil, focusing on the tensioning of a catenary mooring. The Coupled Eulerian–Lagrangian (CEL) approach within ABAQUS is used to capture the interaction between the embedded chain (Lagrangian structure) and the soil (Eulerian material). The anchor chain is simulated by a series of rigid cylindrical segments connected together by LINK connectors.\u0000 Before analysing the global behaviour of an embedded chain, a calibration exercise is undertaken where a straight multi-link portion of the chain is displaced normally and axially in soil. The resulting normal and frictional resistances (per unit length) are compared with those adopted in general practice, in order to calibrate the relationship between the diameter of the cylindrical segments and the bar diameter of the chain. After that, the tensioning process of an anchor chain is simulated, starting from an initial configuration with a 9 m length embedded vertically (attached to a fixed padeye), with the remaining length lying on the seabed. Horizontal tensioning of the chain causes it to cut through the soil until it forms an inverse catenary with an angle of just under 35 degrees to the horizontal at the padeye (and zero degrees at the mudline).\u0000 The loading curve, and also the inverse catenary profile of the chain for different angles at the padeye, are shown to agree well with the Neubecker-Randolph closed-form analytical solution. However, the ratio of the tensions at the padeye and the mudline from the CEL results differs significantly from the analytical solution. Insights from the CEL results indicate that this is because the frictional soil resistance is not fully mobilised, particularly for the portion of the chain in the stronger soil at depth, near the padeye, where the axial displacements are small. This result has significant implications for the geotechnical design of anchoring systems that involve a (nominally) fixed padeye. The simulation methodology also has considerable potential for exploring the creation of an open trench adjacent to a fixed anchor due to monotonic and cyclic perturbations of the anchor chain.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129932204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An improved moving particle semi-implicit (MPS) method was developed to solve water entry problems. The traditional mixed source term was modified based on a prediction-correction scheme to suppress pressure oscillations. An improved free surface identification method was implemented for fluid computations. A weak coupling method was adopted for fluid-structure interaction. The structures were modeled by isotropic linear elastic particles. The application of the source term correction method leads to a better pressure prediction and therefore a more accurate interaction between the fluid and the structure. Validation studies were carried out for water entry of two rigid wedges, a rigid ship section, and a flexible wedge. The results by the present MPS method are in good agreement with experimental data and other published numerical results.
{"title":"Solving 2-D Slamming Problems by the MPS Method With Source Term Correction","authors":"Ruosi Zha, H. Peng, W. Qiu","doi":"10.1115/OMAE2018-78441","DOIUrl":"https://doi.org/10.1115/OMAE2018-78441","url":null,"abstract":"An improved moving particle semi-implicit (MPS) method was developed to solve water entry problems. The traditional mixed source term was modified based on a prediction-correction scheme to suppress pressure oscillations. An improved free surface identification method was implemented for fluid computations. A weak coupling method was adopted for fluid-structure interaction. The structures were modeled by isotropic linear elastic particles. The application of the source term correction method leads to a better pressure prediction and therefore a more accurate interaction between the fluid and the structure. Validation studies were carried out for water entry of two rigid wedges, a rigid ship section, and a flexible wedge. The results by the present MPS method are in good agreement with experimental data and other published numerical results.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129649053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
During the operational phase, the spudcan foundations of a mobile jack-up rig are subjected to combined vertical, horizontal and moment loading. Although previous research has indicated a substantial increase in vertical bearing capacity when a spudcan penetrates through a soft clay layer towards a sand layer, the response of spudcan foundations subjected to combined loadings in such stratification has yet to be understood. This study investigates the effect of the underlying stronger sand layer on the undrained VHM capacity of a spudcan foundation using three-dimensional small-strain finite element analysis. Results show the significant increase in vertical and moment capacity, whereas the horizontal capacity is minimally affected. The soil failure mechanisms are identified and changes in the size and shape of failure envelopes, accounting for the sand layer underneath, are quantified. An analytical expression is proposed to predict the combined capacity of a spudcan foundation in clay overlying sand.
{"title":"Effect of Underlying Sand Layer on Undrained Capacity of Spudcan Foundations in Soft Clay Under Combined Loading","authors":"Yifa Wang, M. Cassidy, B. Bienen","doi":"10.1115/OMAE2018-78198","DOIUrl":"https://doi.org/10.1115/OMAE2018-78198","url":null,"abstract":"During the operational phase, the spudcan foundations of a mobile jack-up rig are subjected to combined vertical, horizontal and moment loading. Although previous research has indicated a substantial increase in vertical bearing capacity when a spudcan penetrates through a soft clay layer towards a sand layer, the response of spudcan foundations subjected to combined loadings in such stratification has yet to be understood. This study investigates the effect of the underlying stronger sand layer on the undrained VHM capacity of a spudcan foundation using three-dimensional small-strain finite element analysis. Results show the significant increase in vertical and moment capacity, whereas the horizontal capacity is minimally affected. The soil failure mechanisms are identified and changes in the size and shape of failure envelopes, accounting for the sand layer underneath, are quantified. An analytical expression is proposed to predict the combined capacity of a spudcan foundation in clay overlying sand.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129576604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Rivera‐Arreba, N. Bruinsma, E. Bachynski, A. Viré, B. T. Paulsen, N. Jacobsen
Floating offshore wind platforms may be subjected to severe sea states, which include both steep and long waves. The hydrodynamic models used in the offshore industry are typically based on potential-flow theory, and/or Morison’s equation. These methods are computationally efficient, and can be applied in global dynamic analysis considering wind loads and mooring system dynamics. However, they may not capture important nonlinearities in extreme situations. The present work compares a fully nonlinear wave tank (NWT), based on the viscous Navier-Stokes equations, and a second-order potential-flow model for such situations. A validation of the NWT is first completed for a moored vertical floating cylinder. The OC5-semisubmersible floating platform is then modelled numerically both in this nonlinear NWT and using a second-order potential-flow based solver. To validate both models, they are subjected to non-steep waves and the response in heave and pitch is compared to experimental data. More extreme conditions are examined with both models. Their comparison shows that if the structure is excited at its heave natural frequency, the dependence of the response in heave on the wave height and the viscous effects cannot be captured by the adjusted potential-flow based model. However, closer to the inertia-dominated region, the two models yield similar responses in pitch and heave.
{"title":"Modeling of a Semisubmersible Floating Wind Platform in Severe Waves","authors":"I. Rivera‐Arreba, N. Bruinsma, E. Bachynski, A. Viré, B. T. Paulsen, N. Jacobsen","doi":"10.1115/OMAE2018-77680","DOIUrl":"https://doi.org/10.1115/OMAE2018-77680","url":null,"abstract":"Floating offshore wind platforms may be subjected to severe sea states, which include both steep and long waves. The hydrodynamic models used in the offshore industry are typically based on potential-flow theory, and/or Morison’s equation. These methods are computationally efficient, and can be applied in global dynamic analysis considering wind loads and mooring system dynamics. However, they may not capture important nonlinearities in extreme situations. The present work compares a fully nonlinear wave tank (NWT), based on the viscous Navier-Stokes equations, and a second-order potential-flow model for such situations.\u0000 A validation of the NWT is first completed for a moored vertical floating cylinder. The OC5-semisubmersible floating platform is then modelled numerically both in this nonlinear NWT and using a second-order potential-flow based solver. To validate both models, they are subjected to non-steep waves and the response in heave and pitch is compared to experimental data.\u0000 More extreme conditions are examined with both models. Their comparison shows that if the structure is excited at its heave natural frequency, the dependence of the response in heave on the wave height and the viscous effects cannot be captured by the adjusted potential-flow based model. However, closer to the inertia-dominated region, the two models yield similar responses in pitch and heave.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130546898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to meet the development need of small-scale marginal oilfield, it is proposed to use the riser and surface casing to bear the loads replacing or partially replacing the steel pipe pile foundation. In this paper, the vertical bearing behavior of variable cross-section composite pile with the diameter of upper part larger than that of lower part (composed of riser and surface casing) is analyzed by finite element method. Then, the influences of different length combinations and diameter combinations of the composite pile on vertical bearing mechanism are studied, and the characteristics of stress concentration at the variable cross-section are revealed. The calculation results show that the increase in pile diameter, pile length and diameter ratio can effectively improve the bearing capacity of riser composite piles. The vertical ultimate bearing capacity of riser composite piles is greatly affected by upper part and less affected by lower part. The bearing capacity of lower part is gradually exerted, as the plastic zone appears at the end of the upper part, meanwhile, the Q-s curve shows as a broken line, which means that a larger pile top settlement is needed in order to effectively activate the bearing capacity of lower part.
{"title":"Study on Vertical Bearing Capacity of the Riser Composite Pile in Clay","authors":"Liang Chao, L. Run, Wan Jun, Gu Pei, Li Xiangyun","doi":"10.1115/OMAE2018-78492","DOIUrl":"https://doi.org/10.1115/OMAE2018-78492","url":null,"abstract":"In order to meet the development need of small-scale marginal oilfield, it is proposed to use the riser and surface casing to bear the loads replacing or partially replacing the steel pipe pile foundation. In this paper, the vertical bearing behavior of variable cross-section composite pile with the diameter of upper part larger than that of lower part (composed of riser and surface casing) is analyzed by finite element method. Then, the influences of different length combinations and diameter combinations of the composite pile on vertical bearing mechanism are studied, and the characteristics of stress concentration at the variable cross-section are revealed. The calculation results show that the increase in pile diameter, pile length and diameter ratio can effectively improve the bearing capacity of riser composite piles. The vertical ultimate bearing capacity of riser composite piles is greatly affected by upper part and less affected by lower part. The bearing capacity of lower part is gradually exerted, as the plastic zone appears at the end of the upper part, meanwhile, the Q-s curve shows as a broken line, which means that a larger pile top settlement is needed in order to effectively activate the bearing capacity of lower part.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130860839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper focuses on the implementation of a nonlinear Lid Technique, as done in the software Diodore™. Several dummy plates are used and modelled as mechanical structures with their own degrees of freedom, capable to account for nonlinear damping. The paper describes first the general equations governing the multi-body sea-keeping model including dummy plate structures, and the expression of the relative quadratic damping. In a second step, examples of applications with gap and moonpool are exposed, demonstrating the capability of the nonlinear Lid Technique with multiple plates to render not only the piston mode, but also the other modes of deformation of the free surface.
{"title":"Nonlinear Lid Technique: Application to Gap and Moonpool Resonance","authors":"B. Lecuyer, M. Rouault","doi":"10.1115/OMAE2018-78623","DOIUrl":"https://doi.org/10.1115/OMAE2018-78623","url":null,"abstract":"This paper focuses on the implementation of a nonlinear Lid Technique, as done in the software Diodore™. Several dummy plates are used and modelled as mechanical structures with their own degrees of freedom, capable to account for nonlinear damping.\u0000 The paper describes first the general equations governing the multi-body sea-keeping model including dummy plate structures, and the expression of the relative quadratic damping. In a second step, examples of applications with gap and moonpool are exposed, demonstrating the capability of the nonlinear Lid Technique with multiple plates to render not only the piston mode, but also the other modes of deformation of the free surface.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126997703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Slowly-varying drift is a phenomenon very familiar to offshore industry, but usually not so much relevant or discussed in naval industry. The classical theoretical background consists in considering a bichromatic wave composed of two regular wave trains of pulsations ω1 and ω2 evolving in the same direction and without any forward speed. The force which varies at low frequency (ω2 – ω1) is known as the slowly-varying drift force and is important in case of moored vessels because it may excite them at their natural periods. The equivalent application in the naval industry is related to maneuvering and added resistance in waves. However, as already indicated, up to the authors’ knowledge, there has not been much work on these issues in the past. State-of-the-art potential flow tools predict well this slowly-varying drift at zero forward speed. However, with an additional forward speed or a strong current, traditional linear potential codes are outside the scope of their underlying hypothesis and cannot predict accurately the low frequency force. With the constant rise of CPU power and accuracy of CFD solvers, this problem may now be addressed in CFD. The results of foamStar, in-house OpenFOAM solver, will be shown with and without additional forward speed.
{"title":"On the Possibility to Compute Slowly-Varying Drift in a CFD Solver","authors":"C. Monroy, Charaf Ouled Housseine, Š. Malenica","doi":"10.1115/OMAE2018-78379","DOIUrl":"https://doi.org/10.1115/OMAE2018-78379","url":null,"abstract":"Slowly-varying drift is a phenomenon very familiar to offshore industry, but usually not so much relevant or discussed in naval industry. The classical theoretical background consists in considering a bichromatic wave composed of two regular wave trains of pulsations ω1 and ω2 evolving in the same direction and without any forward speed. The force which varies at low frequency (ω2 – ω1) is known as the slowly-varying drift force and is important in case of moored vessels because it may excite them at their natural periods. The equivalent application in the naval industry is related to maneuvering and added resistance in waves. However, as already indicated, up to the authors’ knowledge, there has not been much work on these issues in the past.\u0000 State-of-the-art potential flow tools predict well this slowly-varying drift at zero forward speed. However, with an additional forward speed or a strong current, traditional linear potential codes are outside the scope of their underlying hypothesis and cannot predict accurately the low frequency force. With the constant rise of CPU power and accuracy of CFD solvers, this problem may now be addressed in CFD. The results of foamStar, in-house OpenFOAM solver, will be shown with and without additional forward speed.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121532022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vertically driven plate anchors offer an attractive anchoring solution for floating offshore structures, as they are both highly efficient and suitable for a wide range of soil conditions. Since they are oriented vertically after installation, keying is required to orient the anchor into the direction of applied loading. Simulation of the keying process has not been extensively investigated by previous research, especially for cohesionless soil. Reliable prediction of irrecoverable embedment loss during keying is needed, since such loss can lead to significant reduction in the uplift capacity of the plate anchors. Large deformation finite element analyses LDFE method using RITSS (Remeshing and Interpolation Technique with Small Strain) were used to simulate the keying process of strip plate anchor embedded in uniform cohesionless soil. LDFE showed that the loss in embedment depth of plate anchor during rotation is inversely proportional to the loading eccentricity e/B. It was also found that the maximum pullout capacity occurs before the end of keying process at orientations between 60° to 85° degrees for vertical loading. Also, the LDFE study showed that reduced elastic soil stiffness leading to increased levels of displacement at which the peak load is approached.
垂直驱动板锚为浮式海上结构提供了一种极具吸引力的锚固解决方案，因为它们既高效又适用于各种土壤条件。由于它们在安装后是垂直定向的，因此需要按键将锚定向到应用加载的方向。以往的研究尚未对键控过程的模拟进行广泛的研究，特别是对无黏性土壤的键控过程。由于这种损失会导致板锚的提升能力显著降低，因此需要对键控过程中不可恢复的嵌入损失进行可靠的预测。采用基于RITSS (Remeshing and Interpolation Technique with Small Strain)的大变形有限元分析方法，模拟了均匀无黏性土体中条板锚的锚固过程。LDFE结果表明，旋转过程中板锚埋深损失与加载偏心e/B成反比。竖向加载时，在60°~ 85°的方向上，最大拉拔能力出现在键控过程结束前。此外，LDFE研究表明，弹性土刚度的降低导致峰值荷载接近时位移水平的增加。
{"title":"Numerical Investigation Into the Keying Process of a Plate Anchor Vertically Installed in Cohesionless Soil","authors":"Nabil Al Hakeem, C. Aubeny","doi":"10.1115/OMAE2018-78617","DOIUrl":"https://doi.org/10.1115/OMAE2018-78617","url":null,"abstract":"Vertically driven plate anchors offer an attractive anchoring solution for floating offshore structures, as they are both highly efficient and suitable for a wide range of soil conditions. Since they are oriented vertically after installation, keying is required to orient the anchor into the direction of applied loading. Simulation of the keying process has not been extensively investigated by previous research, especially for cohesionless soil. Reliable prediction of irrecoverable embedment loss during keying is needed, since such loss can lead to significant reduction in the uplift capacity of the plate anchors. Large deformation finite element analyses LDFE method using RITSS (Remeshing and Interpolation Technique with Small Strain) were used to simulate the keying process of strip plate anchor embedded in uniform cohesionless soil. LDFE showed that the loss in embedment depth of plate anchor during rotation is inversely proportional to the loading eccentricity e/B. It was also found that the maximum pullout capacity occurs before the end of keying process at orientations between 60° to 85° degrees for vertical loading. Also, the LDFE study showed that reduced elastic soil stiffness leading to increased levels of displacement at which the peak load is approached.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"99 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131779699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Impacts by ship anchors are one of the main reasons for damage to submarine cables. Regulations meet this risk by defining a minimum permanent burial depth of submarine cables. The key parameters for the risk evaluation are the burial depth of the cable as well as the penetration depth of the anchor. In order to meet this risk sufficiently and to reduce the risk of submarine cable damage, the penetration process into the sea bed of the ship anchor has to be understood. Numerical simulations of the anchor penetration in sand are performed, in order to investigate the influence of anchor movement on submarine cables and to identify possible damage mechanisms.
{"title":"Penetration of Ship Anchors and the Influence of Submarine Cables","authors":"J. Grabe, E. Heins","doi":"10.1115/OMAE2018-78314","DOIUrl":"https://doi.org/10.1115/OMAE2018-78314","url":null,"abstract":"Impacts by ship anchors are one of the main reasons for damage to submarine cables. Regulations meet this risk by defining a minimum permanent burial depth of submarine cables. The key parameters for the risk evaluation are the burial depth of the cable as well as the penetration depth of the anchor. In order to meet this risk sufficiently and to reduce the risk of submarine cable damage, the penetration process into the sea bed of the ship anchor has to be understood. Numerical simulations of the anchor penetration in sand are performed, in order to investigate the influence of anchor movement on submarine cables and to identify possible damage mechanisms.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115922110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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