The quasi-rectangular tunnel represents a novel cross-section design,intended to supersede the traditional circular and rectangular tunnel formats.Due to the limited capacity of the tunnel vault to withstand vertical ...The quasi-rectangular tunnel represents a novel cross-section design,intended to supersede the traditional circular and rectangular tunnel formats.Due to the limited capacity of the tunnel vault to withstand vertical loads,an interior column is often installed at the center to enhance its load-bearing capacity.This study aims to develop a hyperstatic reaction method(HRM)for the analysis of deformation and structural integrity in this specific tunnel type.The computational model is validated through comparison with the corresponding finite element method(FEM)analysis.Following comprehensive validation,an ensemble machine learning(ML)model is proposed,using numerical benchmark data,to facilitate real-time design and optimization.Subsequently,three widely used ensemble models,i.e.random forest(RF),gradient boosting decision tree(GBDT),and extreme gradient boosting(XGBoost)are compared to identify the most efficient ML model for replacing the HRM model in the design optimization process.The performance metrics,such as the coefficient of determination R2 of about 0.999 and the mean absolute percentage error(MAPE)of about 1%,indicate that XGBoost outperforms the others,exhibiting excellent agreement with the HRM analysis.Additionally,the model demonstrates high computational efficiency,with prediction times measured in seconds.Finally,the HRM-XGBoost model is integrated with the well-known particle swarm optimization(PSO)for the real-time design optimization of quasi-rectangular tunnels,both with and without the interior column.A feature importance assessment is conducted to evaluate the sensitivity of design input features,enabling the selection of the most critical features for the optimization task.展开更多
Tunnels are now an integral part of the infrastructure in major cities around the world. For many reasons, these tunnels have horseshoe-shaped cross-sections with round top and flat bottom. This paper presents some im...Tunnels are now an integral part of the infrastructure in major cities around the world. For many reasons, these tunnels have horseshoe-shaped cross-sections with round top and flat bottom. This paper presents some improvements to the use of the Hyperstatic Reaction Method-HRM for analysing tunnels with horseshoe-shaped cross-sections when these tunnels operate under the influence of earthquakes, particularly in cases when the tunnel lining is a continuous lining. The analysis used parameters of a tunnel from the Hanoi metro system, as well as parameters of the strongest earthquake that may occur in the central Hanoi area in the improved HRM and 2 D numerical methods using the ABAQUS software. On the basis of the results obtained, the paper gives conclusions about the HRM methodology when it is used to calculate tunnels that have horseshoe cross-sections operating under the influence of earthquakes.展开更多
The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques.A novel hyperstatic six-component force/torque sensor based on ...The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques.A novel hyperstatic six-component force/torque sensor based on the Stewart platform structure,which can be used for the force measurement of the robot wrist,is proposed,and its structural optimal design,finite element analysis and calibration experimentation is presented.The characteristic of the sensor structure is analyzed in comparison with the traditional Stewart platform-based sensor.The mathematical expression of the sensor's force mapping matrix is introduced.The condition number and generalized amplifying coefficient defined by singular values of force Jacobian matrix are used to evaluate the performances of isotropy and sensitivity of the sensor respectively.The optimal design of the sensor structure is performed with the objective of achieving high measurement sensitivity and good isotropy.The sensor prototype is fabricated,and the static and dynamic characteristics of the sensor are analyzed with finite element analysis software package ANSYS.The calibration device is manufactured,and the data acquisition and processing system is developed.The theoretical and experimental study of the static calibration of the sensor prototype is carried out.The results of simulation analysis and calibration experimentation prove the feasibility of the hyperstatic sensor structure,and the contents of this paper possess theoretical significance and engineering value for the further research and practical application of the six-component force sensor.展开更多
Purpose–The purpose of this paper is to propose a method to avoid hyperstaticity and eventually reduce the magnitude of undesired force/torques.The authors also study the influence of hyperstaticity on human motor co...Purpose–The purpose of this paper is to propose a method to avoid hyperstaticity and eventually reduce the magnitude of undesired force/torques.The authors also study the influence of hyperstaticity on human motor control during a redundant task.Design/methodology/approach–Increasing the level of transparency of robotic interfaces is critical to haptic investigations and applications.This issue is particularly important to robotic structures that mimic the human counterpart’s morphology and attach directly to the limb.Problems arise for complex joints such as the wrist,which cannot be accurately matched with a traditional mechanical joint.In such cases,mechanical differences between human and robotic joint cause hyperstaticity(i.e.over-constrained)which,coupled with kinematic misalignment,leads to uncontrolled force/torque at the joint.This paper focusses on the prono-supination(PS)degree of freedom of the forearm.The overall force and torque in the wrist PS rotation is quantified by means of a wrist robot.Findings–A practical solution to avoid hyperstaticity and reduce the level of undesired force/torque in the wrist is presented.This technique is shown to reduce 75 percent of the force and 68 percent of the torque.It is also shown an over-constrained mechanism could alter human motor strategies.Practical implications–The presented solution could be taken into account in the early phase of design of robots.It could also be applied to modify the fixation points of commercial robots in order to reduce the magnitude of reaction forces and avoid changes in motor strategy during the robotic therapy.Originality/value–In this paper for the first time the authors study the effect of hyperstaticity on both reaction forces and human motor strategies.展开更多
Subsea tunnel lining structures should be designed to sustain the loads transmitted from surrounding ground and groundwater during excavation. Extremely high pore-water pressure reduces the effective strength of the c...Subsea tunnel lining structures should be designed to sustain the loads transmitted from surrounding ground and groundwater during excavation. Extremely high pore-water pressure reduces the effective strength of the country rock that surrounds a tunnel, thereby lowering the arching effect and stratum stability of the structure. In this paper, the mechanical behavior and shape optimization of the lining structure for the Xiang＇an tunnel excavated in weathered slots are examined. Eight cross sections with different geometric parameters are adopted to study the mechanical behavior and shape optimization of the lining structure. The hyperstatic reaction method is used through finite element analysis software ANSYS. The mechanical behavior of the lining structure is evidently affected by the geometric parameters of crosssectional shape. The minimum safety factor of the lining structure elements is set to be the objective function. The efficient tunnel shape to maximize the minimum safety factor is identified. The minimum safety factor increases significantly after optimization. The optimized cross section significantly improves the mechanical characteristics of the lining structure and effectively reduces its deformation. Force analyses of optimization process and program are conducted parametrically so that the method can be applied to the optimization design of other similar structures. The results obtained from this study enhance our understanding of the mechanical behavior of the lining structure for subsea tunnels. These results are also beneficial to the optimal design of lining structures in general.展开更多
Underground facilities are usually constructed under existing buildings,or buildings are constructed over existing underground structures.It is then imperative to account for the current overburden loads and future su...Underground facilities are usually constructed under existing buildings,or buildings are constructed over existing underground structures.It is then imperative to account for the current overburden loads and future surface loadings in the design of tunnels.In addition,tunnels are often constructed beneath the groundwater level,such as cross-river tunnels.Therefore,it is also important to consider the water pressure impact on the tunnel lining behaviour.Tunnels excavated by a conventional tunnelling method are considered in this paper.The hyperstatic reaction method(HRM)is adopted in this study to investigate the effect of surcharge loading on a horseshoe-shaped tunnel behaviour excavated in saturated soft rocks.The results obtained from the HRM and numerical modelling are in good agreement.Parametric studies were then performed to show the effects of the water pressure,surcharge loading value and its width,and groundwater level on the behaviour of the horseshoe-shaped tunnel lining,in terms of internal forces and displacements.It displays that the bending moment,normal forces and radial displacements are more sensitive to the water pressure,surcharge loading and groundwater level.展开更多
As the strict limitation of primary structure in traditional force method and displacement method in indeterminate analysis may lead to complicated high-order linear equations, a breakthrough of the limitation, i.e., ...As the strict limitation of primary structure in traditional force method and displacement method in indeterminate analysis may lead to complicated high-order linear equations, a breakthrough of the limitation, i.e., the application of irregular force method and irregular displacement method, would be introduced in this paper to ease the difficulty of hand computations. By using hyperstatic primary structures and partly chained primary structures, the primary structures of force method and displacement method are reformed, and the order of the system is decreased. The technique is explained through examples. The significance of the new method is summarized.展开更多
基金funded by the Hanoi University of Mining and Geology(Grant No.T23-44)The research is also funded by the German Research Foundation(DFG e Project number 518862444)in collaboration with the Vietnam National Foundation for Science and Technology Development(NAFOSTED)under grant number DFG.105e2022.03The third author was funded by the Postdoctoral Scholarship Program of the Vingroup Innovation Foundation(VINIF)(VINIF.2023.STS.15).
文摘The quasi-rectangular tunnel represents a novel cross-section design,intended to supersede the traditional circular and rectangular tunnel formats.Due to the limited capacity of the tunnel vault to withstand vertical loads,an interior column is often installed at the center to enhance its load-bearing capacity.This study aims to develop a hyperstatic reaction method(HRM)for the analysis of deformation and structural integrity in this specific tunnel type.The computational model is validated through comparison with the corresponding finite element method(FEM)analysis.Following comprehensive validation,an ensemble machine learning(ML)model is proposed,using numerical benchmark data,to facilitate real-time design and optimization.Subsequently,three widely used ensemble models,i.e.random forest(RF),gradient boosting decision tree(GBDT),and extreme gradient boosting(XGBoost)are compared to identify the most efficient ML model for replacing the HRM model in the design optimization process.The performance metrics,such as the coefficient of determination R2 of about 0.999 and the mean absolute percentage error(MAPE)of about 1%,indicate that XGBoost outperforms the others,exhibiting excellent agreement with the HRM analysis.Additionally,the model demonstrates high computational efficiency,with prediction times measured in seconds.Finally,the HRM-XGBoost model is integrated with the well-known particle swarm optimization(PSO)for the real-time design optimization of quasi-rectangular tunnels,both with and without the interior column.A feature importance assessment is conducted to evaluate the sensitivity of design input features,enabling the selection of the most critical features for the optimization task.
基金supported by the Saint Petersburg Mining University
文摘Tunnels are now an integral part of the infrastructure in major cities around the world. For many reasons, these tunnels have horseshoe-shaped cross-sections with round top and flat bottom. This paper presents some improvements to the use of the Hyperstatic Reaction Method-HRM for analysing tunnels with horseshoe-shaped cross-sections when these tunnels operate under the influence of earthquakes, particularly in cases when the tunnel lining is a continuous lining. The analysis used parameters of a tunnel from the Hanoi metro system, as well as parameters of the strongest earthquake that may occur in the central Hanoi area in the improved HRM and 2 D numerical methods using the ABAQUS software. On the basis of the results obtained, the paper gives conclusions about the HRM methodology when it is used to calculate tunnels that have horseshoe cross-sections operating under the influence of earthquakes.
基金supported by National Natural Science Foundation of China(Grant No.50575192)Hebei Provincial Natural Science Foundation of China(Grant No.E2007000349)
文摘The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques.A novel hyperstatic six-component force/torque sensor based on the Stewart platform structure,which can be used for the force measurement of the robot wrist,is proposed,and its structural optimal design,finite element analysis and calibration experimentation is presented.The characteristic of the sensor structure is analyzed in comparison with the traditional Stewart platform-based sensor.The mathematical expression of the sensor's force mapping matrix is introduced.The condition number and generalized amplifying coefficient defined by singular values of force Jacobian matrix are used to evaluate the performances of isotropy and sensitivity of the sensor respectively.The optimal design of the sensor structure is performed with the objective of achieving high measurement sensitivity and good isotropy.The sensor prototype is fabricated,and the static and dynamic characteristics of the sensor are analyzed with finite element analysis software package ANSYS.The calibration device is manufactured,and the data acquisition and processing system is developed.The theoretical and experimental study of the static calibration of the sensor prototype is carried out.The results of simulation analysis and calibration experimentation prove the feasibility of the hyperstatic sensor structure,and the contents of this paper possess theoretical significance and engineering value for the further research and practical application of the six-component force sensor.
基金the New Funding Initiative 2010(NTU)the Academic Research Fund(AcRF)Tier1(RG 50/11),Ministry of Education,Singapore.
文摘Purpose–The purpose of this paper is to propose a method to avoid hyperstaticity and eventually reduce the magnitude of undesired force/torques.The authors also study the influence of hyperstaticity on human motor control during a redundant task.Design/methodology/approach–Increasing the level of transparency of robotic interfaces is critical to haptic investigations and applications.This issue is particularly important to robotic structures that mimic the human counterpart’s morphology and attach directly to the limb.Problems arise for complex joints such as the wrist,which cannot be accurately matched with a traditional mechanical joint.In such cases,mechanical differences between human and robotic joint cause hyperstaticity(i.e.over-constrained)which,coupled with kinematic misalignment,leads to uncontrolled force/torque at the joint.This paper focusses on the prono-supination(PS)degree of freedom of the forearm.The overall force and torque in the wrist PS rotation is quantified by means of a wrist robot.Findings–A practical solution to avoid hyperstaticity and reduce the level of undesired force/torque in the wrist is presented.This technique is shown to reduce 75 percent of the force and 68 percent of the torque.It is also shown an over-constrained mechanism could alter human motor strategies.Practical implications–The presented solution could be taken into account in the early phase of design of robots.It could also be applied to modify the fixation points of commercial robots in order to reduce the magnitude of reaction forces and avoid changes in motor strategy during the robotic therapy.Originality/value–In this paper for the first time the authors study the effect of hyperstaticity on both reaction forces and human motor strategies.
基金financially supported by the National Natural Science Foundation of China(Grant No.51308012)the Key Laboratory of Transportation Tunnel Engineering+1 种基金Ministry of EducationSouthwest Jiaotong University(Grant No.TTE2014-06)
文摘Subsea tunnel lining structures should be designed to sustain the loads transmitted from surrounding ground and groundwater during excavation. Extremely high pore-water pressure reduces the effective strength of the country rock that surrounds a tunnel, thereby lowering the arching effect and stratum stability of the structure. In this paper, the mechanical behavior and shape optimization of the lining structure for the Xiang＇an tunnel excavated in weathered slots are examined. Eight cross sections with different geometric parameters are adopted to study the mechanical behavior and shape optimization of the lining structure. The hyperstatic reaction method is used through finite element analysis software ANSYS. The mechanical behavior of the lining structure is evidently affected by the geometric parameters of crosssectional shape. The minimum safety factor of the lining structure elements is set to be the objective function. The efficient tunnel shape to maximize the minimum safety factor is identified. The minimum safety factor increases significantly after optimization. The optimized cross section significantly improves the mechanical characteristics of the lining structure and effectively reduces its deformation. Force analyses of optimization process and program are conducted parametrically so that the method can be applied to the optimization design of other similar structures. The results obtained from this study enhance our understanding of the mechanical behavior of the lining structure for subsea tunnels. These results are also beneficial to the optimal design of lining structures in general.
基金The first author is supported by the Fundamental Research Funds for the Central Universities in China.The third author is supported by the Vietnam Ministry of Education and Training under grant number B2020-MDA-15.These funds are greatly appreciated.
文摘Underground facilities are usually constructed under existing buildings,or buildings are constructed over existing underground structures.It is then imperative to account for the current overburden loads and future surface loadings in the design of tunnels.In addition,tunnels are often constructed beneath the groundwater level,such as cross-river tunnels.Therefore,it is also important to consider the water pressure impact on the tunnel lining behaviour.Tunnels excavated by a conventional tunnelling method are considered in this paper.The hyperstatic reaction method(HRM)is adopted in this study to investigate the effect of surcharge loading on a horseshoe-shaped tunnel behaviour excavated in saturated soft rocks.The results obtained from the HRM and numerical modelling are in good agreement.Parametric studies were then performed to show the effects of the water pressure,surcharge loading value and its width,and groundwater level on the behaviour of the horseshoe-shaped tunnel lining,in terms of internal forces and displacements.It displays that the bending moment,normal forces and radial displacements are more sensitive to the water pressure,surcharge loading and groundwater level.
文摘As the strict limitation of primary structure in traditional force method and displacement method in indeterminate analysis may lead to complicated high-order linear equations, a breakthrough of the limitation, i.e., the application of irregular force method and irregular displacement method, would be introduced in this paper to ease the difficulty of hand computations. By using hyperstatic primary structures and partly chained primary structures, the primary structures of force method and displacement method are reformed, and the order of the system is decreased. The technique is explained through examples. The significance of the new method is summarized.
