The seismic safety of offshore wind turbines is an important issue that needs to be solved urgently.Based on a unified computing framework,this paper develops a set of seawater-seabed-wind turbine zoning coupling anal...The seismic safety of offshore wind turbines is an important issue that needs to be solved urgently.Based on a unified computing framework,this paper develops a set of seawater-seabed-wind turbine zoning coupling analysis methods.A 5 MW wind turbine and a site analysis model are established,and a seismic wave is selected to analyze the changes in the seismic response of offshore monopile wind turbines under the change of seawater depth,seabed wave velocity and seismic wave incidence angle.The analysis results show that when the seawater increases to a certain depth,the seismic response of the wind turbine increases.The shear wave velocity of the seabed affects the bending moment and displacement at the bottom of the tower.When the angle of incidence increases,the vertical displacement and the acceleration of the top of the tower increase in varying degrees.展开更多
The interaction between pile and soft soil of the passive pile group subjected to soil movement was analyzed with three-dimensional finite element model by using ANSYS software. The soil was assumed to be elastic-plas...The interaction between pile and soft soil of the passive pile group subjected to soil movement was analyzed with three-dimensional finite element model by using ANSYS software. The soil was assumed to be elastic-plastic complying with the Drucker-Prager yield criterion in the analysis. The large displacement of soil was considered and contact elements were used to evaluate the interaction between pile and soil. The influences of soil depth of layer and number of piles on the lateral pressure of the pile were investigated, and the lateral pressure distributions on the (2×1) pile group and on the (2×2) pile group were compared. The results show that the adjacent surcharge may result in significant lateral movement of the soft soil and considerable pressure on the pile. The pressure acting on the row near the surcharge is higher than that on the other row, due to the "barrier" and arching effects in pile groups. The passive load and its distribution should be taken into account in the design of the passive piles.展开更多
A simplified approach was proposed to analyze the negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge. Based on the concentric cylinder shearing theory, consider...A simplified approach was proposed to analyze the negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge. Based on the concentric cylinder shearing theory, considering the changes of pile shape(such as, taper angle and diameters of pile base, etc.), the load-transfer of special-shaped pile was built. The accuracy of the developed simplified approach was verified by numerical simulation model with the same condition. Then, the influence factors, such as, taper angles, the diameter of pile base, surcharge, and pile-soil interface parameters were analyzed and discussed. The results show that the developed simplified approach can calculate NSF of special-shaped pile under surcharge effectively. A limited parametric study indicates that in many practical situations special-shaped piles(such as belled wedge pile shown in this work) offer a design option that is more economical than traditional uniform cross-section piles.展开更多
The three-stage simulation method based on LS-DYNA was introduced in this study to simulate the progressive collapse of a continuous girder bridge after a ship-bridge collision. The pile-soil dynamic interaction and t...The three-stage simulation method based on LS-DYNA was introduced in this study to simulate the progressive collapse of a continuous girder bridge after a ship-bridge collision. The pile-soil dynamic interaction and the initial stress and deformation of the whole bridge before the collision were considered. By analyzing the damage, deformation, stress distribution and collapse process of the whole bridge, the results show that the displacement response of the cap beam lags behind the pile cap. The response order of the whole bridge's components depends on their distances from the collision region. The plastic deformation of soil around piles has a positive effect on delaying the further increase in the displacement of piles. The impacted pier's losing stability and its superstructure's excessive deformation are the main reasons leading to the progressive collapse of the continuous girder bridge.展开更多
At present,the thrust of an anti-slide pile can be worked out with some calculation methods. However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be...At present,the thrust of an anti-slide pile can be worked out with some calculation methods. However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be easily obtained. In this paper,the authors applied the strength-reduction finite element method (FEM) to several design cases of anti-slide piles. Using this method,it is possible to take the pile-soil interactions into consideration,obtain reasonable resistance in front of pile and the distributions of thrust and resistance,and reasonable lengths of anti-slide piles. In particular,the thrust and resistance imposed on embedded anti-slide piles can be calculated and composite anti-slide pile structures such as anchored piles and braced piles can be optimized. It is proved through the calculation examples that this method is more reliable and economical in the design of anti-slide pile.展开更多
In seismic design of tapered high pier, the analysis of natural vibration frequency is of great importance. According to the engineering features of tapered high pier in mountainous area, a vibration calculation model...In seismic design of tapered high pier, the analysis of natural vibration frequency is of great importance. According to the engineering features of tapered high pier in mountainous area, a vibration calculation model was set up considering the tapered pier characteristics and pile-soil interaction. Based on Southwell frequency composition theory, it consists of elastic deformation of bridge pier and the rigid deformation of group piles, which are respectively solved by the finite-element method and energy method, and then the natural frequency is derived. The comparison between the measured and calculated results shows that the calculation errors with and without considering pile-soil interaction are 4.9% and 14.7%, respectively. Additionally, the main parameters (pier height, section variation coefficient and lateral foundation horizontal proportional coefficient) affecting natural frequency were investigated. The result shows that natural frequency ascends with the increase of the lateral foundation horizontal proportional coefficient; and it is quite necessary to consider the pile-soil interaction in natural frequency calculation of tapered high pier.展开更多
The effective stress method is developed to predict the axial capacity of piles in clay. The effective stress state changes due to the resulting pore pressure change and therefore, the strength and stiffness of the so...The effective stress method is developed to predict the axial capacity of piles in clay. The effective stress state changes due to the resulting pore pressure change and therefore, the strength and stiffness of the soil will change. In this work, the finite element method is utilized as a tool for the analysis of pile-soil systems in undrained condition. The computer program CRISP was developed to suit the problem requirements. CRISP uses the finite element technique and allows predictions to be made of ground deformation using critical state theories. Eight-node isoparametric element was added to the program in addition to the slip element. A pile loading problem was solved in which the pile-soil system is analyzed in undrained condition. The pile is modelled as elastic-plastic material, while the soil is assumed to follow the modified Cam clay model. During undrained loading condition, the settlement values increase by 22% when slip elements are used. The surface settlement increases by about three times when the load is doubled and the surface settlement at all points increases when using slip elements due to the mode of motion which allows smooth movement of the adjacent soil with respect to the pile. The vertical displacement increases as the distance decreases from the pile and negligible values are obtained beyond 10D (where D is the pile diameter) from the center of the pile and these values are slightly increased when slip elements are used. The vertical effective stress along a section at a distance D from the pile center is approximately the same for all load increments and lower values of effective vertical stress can be obtained when slip elements are used.展开更多
Offshore platforms in seismically active areas should be designed to service severe earthquake excitations with no global structural failure. This paper summarizes the dynamic analysis of a typical fixed platform unde...Offshore platforms in seismically active areas should be designed to service severe earthquake excitations with no global structural failure. This paper summarizes the dynamic analysis of a typical fixed platform under the earthquake loading in the seismically active area. The dynamic analysis includes interpretation of dynamic design parameters based on the available site-specific data,together with foundation design recommendations for earthquake loading conditions,which include free-field site response analyses,liquefaction analyses and soil-pile interaction analyses.展开更多
基金supported in part by the National Natural Science Foundation of China(Nos.51978337,U2039209).
文摘The seismic safety of offshore wind turbines is an important issue that needs to be solved urgently.Based on a unified computing framework,this paper develops a set of seawater-seabed-wind turbine zoning coupling analysis methods.A 5 MW wind turbine and a site analysis model are established,and a seismic wave is selected to analyze the changes in the seismic response of offshore monopile wind turbines under the change of seawater depth,seabed wave velocity and seismic wave incidence angle.The analysis results show that when the seawater increases to a certain depth,the seismic response of the wind turbine increases.The shear wave velocity of the seabed affects the bending moment and displacement at the bottom of the tower.When the angle of incidence increases,the vertical displacement and the acceleration of the top of the tower increase in varying degrees.
基金Project(50378036) supported by the National Natural Science Foundation of China
文摘The interaction between pile and soft soil of the passive pile group subjected to soil movement was analyzed with three-dimensional finite element model by using ANSYS software. The soil was assumed to be elastic-plastic complying with the Drucker-Prager yield criterion in the analysis. The large displacement of soil was considered and contact elements were used to evaluate the interaction between pile and soil. The influences of soil depth of layer and number of piles on the lateral pressure of the pile were investigated, and the lateral pressure distributions on the (2×1) pile group and on the (2×2) pile group were compared. The results show that the adjacent surcharge may result in significant lateral movement of the soft soil and considerable pressure on the pile. The pressure acting on the row near the surcharge is higher than that on the other row, due to the "barrier" and arching effects in pile groups. The passive load and its distribution should be taken into account in the design of the passive piles.
基金Projects(51278170,U1134207)supported by the National Natural Science Foundation of ChinaProject(B13024)supported by the Program of Introducing Talents of Discipline to Universities,China
文摘A simplified approach was proposed to analyze the negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge. Based on the concentric cylinder shearing theory, considering the changes of pile shape(such as, taper angle and diameters of pile base, etc.), the load-transfer of special-shaped pile was built. The accuracy of the developed simplified approach was verified by numerical simulation model with the same condition. Then, the influence factors, such as, taper angles, the diameter of pile base, surcharge, and pile-soil interface parameters were analyzed and discussed. The results show that the developed simplified approach can calculate NSF of special-shaped pile under surcharge effectively. A limited parametric study indicates that in many practical situations special-shaped piles(such as belled wedge pile shown in this work) offer a design option that is more economical than traditional uniform cross-section piles.
基金Supported by the National Natural Science Foundation of China(No.51178310)the Foundation of China Scholarship Council(No.201308120137)
文摘The three-stage simulation method based on LS-DYNA was introduced in this study to simulate the progressive collapse of a continuous girder bridge after a ship-bridge collision. The pile-soil dynamic interaction and the initial stress and deformation of the whole bridge before the collision were considered. By analyzing the damage, deformation, stress distribution and collapse process of the whole bridge, the results show that the displacement response of the cap beam lags behind the pile cap. The response order of the whole bridge's components depends on their distances from the collision region. The plastic deformation of soil around piles has a positive effect on delaying the further increase in the displacement of piles. The impacted pier's losing stability and its superstructure's excessive deformation are the main reasons leading to the progressive collapse of the continuous girder bridge.
基金This research was funded by the National Natural Science Foundation of China (Grant No.40872191)NSF of Chongqing(Grant No. CSTC2009BB6178)
文摘At present,the thrust of an anti-slide pile can be worked out with some calculation methods. However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be easily obtained. In this paper,the authors applied the strength-reduction finite element method (FEM) to several design cases of anti-slide piles. Using this method,it is possible to take the pile-soil interactions into consideration,obtain reasonable resistance in front of pile and the distributions of thrust and resistance,and reasonable lengths of anti-slide piles. In particular,the thrust and resistance imposed on embedded anti-slide piles can be calculated and composite anti-slide pile structures such as anchored piles and braced piles can be optimized. It is proved through the calculation examples that this method is more reliable and economical in the design of anti-slide pile.
基金Project(50708033) supported by the National Natural Science Foundation of China
文摘In seismic design of tapered high pier, the analysis of natural vibration frequency is of great importance. According to the engineering features of tapered high pier in mountainous area, a vibration calculation model was set up considering the tapered pier characteristics and pile-soil interaction. Based on Southwell frequency composition theory, it consists of elastic deformation of bridge pier and the rigid deformation of group piles, which are respectively solved by the finite-element method and energy method, and then the natural frequency is derived. The comparison between the measured and calculated results shows that the calculation errors with and without considering pile-soil interaction are 4.9% and 14.7%, respectively. Additionally, the main parameters (pier height, section variation coefficient and lateral foundation horizontal proportional coefficient) affecting natural frequency were investigated. The result shows that natural frequency ascends with the increase of the lateral foundation horizontal proportional coefficient; and it is quite necessary to consider the pile-soil interaction in natural frequency calculation of tapered high pier.
基金Project(RG086/10AET) supported by the Institute of Research Management and Monitoring (IPPP),University of Malaya (UM) under UMRG grant number,Malaysia
文摘The effective stress method is developed to predict the axial capacity of piles in clay. The effective stress state changes due to the resulting pore pressure change and therefore, the strength and stiffness of the soil will change. In this work, the finite element method is utilized as a tool for the analysis of pile-soil systems in undrained condition. The computer program CRISP was developed to suit the problem requirements. CRISP uses the finite element technique and allows predictions to be made of ground deformation using critical state theories. Eight-node isoparametric element was added to the program in addition to the slip element. A pile loading problem was solved in which the pile-soil system is analyzed in undrained condition. The pile is modelled as elastic-plastic material, while the soil is assumed to follow the modified Cam clay model. During undrained loading condition, the settlement values increase by 22% when slip elements are used. The surface settlement increases by about three times when the load is doubled and the surface settlement at all points increases when using slip elements due to the mode of motion which allows smooth movement of the adjacent soil with respect to the pile. The vertical displacement increases as the distance decreases from the pile and negligible values are obtained beyond 10D (where D is the pile diameter) from the center of the pile and these values are slightly increased when slip elements are used. The vertical effective stress along a section at a distance D from the pile center is approximately the same for all load increments and lower values of effective vertical stress can be obtained when slip elements are used.
文摘Offshore platforms in seismically active areas should be designed to service severe earthquake excitations with no global structural failure. This paper summarizes the dynamic analysis of a typical fixed platform under the earthquake loading in the seismically active area. The dynamic analysis includes interpretation of dynamic design parameters based on the available site-specific data,together with foundation design recommendations for earthquake loading conditions,which include free-field site response analyses,liquefaction analyses and soil-pile interaction analyses.
