An optimal design configuration of leading edge extensions （LEXs） is presented based on the standard genetic algorithms （GAs）. Aircraft longitudinal dynamic response of the system with and without LEX is analyzed ...An optimal design configuration of leading edge extensions （LEXs） is presented based on the standard genetic algorithms （GAs）. Aircraft longitudinal dynamic response of the system with and without LEX is analyzed by solving the state equation of aircraft longitudinal motion. Aerodynamic force, moments, and longitudinal stability derivatives are estimated by three-dimensional low-order panel method. A novel aircraft model with LEX is optimized and its lift curve slope is increased by 13%-17% for Ma=0. 4-0. 9 and 12% for Ma=1. 5. Numerical results show that because the frequency and damping ratio in a short period are improved, the aircraft rapidly responds to a specified deflection control input in the battle area when LEX is installed. Finally, compared the results from the panel method with those from the Cy-20 aircraft flight test data,aerodynamic characteristics are verified.展开更多
The surcharge load at the ground surface inevitably breaks the original equilibrium state between the underneath tunnel and the surrounding soil,which will impact the service performance of a subway tunnel.This paper ...The surcharge load at the ground surface inevitably breaks the original equilibrium state between the underneath tunnel and the surrounding soil,which will impact the service performance of a subway tunnel.This paper presents a novel semi-analytical approach for assessing the time-dependent,longitudinal responses of a subway tunnel in soft soil strata induced by the surcharge load.The solution is developed based on the framework of the classical"two-stage method"but innovatively incorporates the effects of ground stratification,the consolidation process,and the longitudinal stiffness reduction of the lining.Biot’s poroelastic theory in conjunction with the Laplace-Fourier transform technique is selected to model the deformation of the stratified ground,while the Timoshenko beam on a Pasternak foundation is employed to model the mechanical responses of the tunnel.The proposed semi-analytical solution is validated not only by comparison with benchmark solutions and a finite element model,but also by predicting a well-documented field measurement.Parametric analyses are conducted to investigate the effects of the elastic modulus and the permeability coefficient of the stratified ground on the longitudinal responses of the tunnel.It is expected that the proposed solution can serve as a useful tool for evaluating the effects of the surcharge load on the longitudinal responses of a subway tunnel.展开更多
For the longitudinal seismic response analysis of a tunnel structure under asynchronous earthquake excitations,a longitudinal integral response deformation method classified as a practical approach is proposed in this...For the longitudinal seismic response analysis of a tunnel structure under asynchronous earthquake excitations,a longitudinal integral response deformation method classified as a practical approach is proposed in this paper.The determinations of the structural critical moments when maximal deformations and internal forces in the longitudinal direction occur are deduced as well.When applying the proposed method,the static analysis of the free-field computation model subjected to the least favorable free-field deformation at the tunnel buried depth is performed first to calculate the equivalent input seismic loads.Then,the equivalent input seismic loads are imposed on the integral tunnel-foundation computation model to conduct the static calculation.Afterwards,the critical longitudinal seismic responses of the tunnel are obtained.The applicability of the new method is verified by comparing the seismic responses of a shield tunnel structure in Beijing,determined by the proposed procedure and by a dynamic time-history analysis under a series of obliquely incident out-of-plane and in-plane waves.The results show that the proposed method has a clear concept with high accuracy and simple progress.Meanwhile,this method provides a feasible way to determine the critical moments of the longitudinal seismic responses of a tunnel structure.Therefore,the proposed method can be effectively applied to analyze the seismic response of a long-line underground structure subjected to non-uniform excitations.展开更多
This paper aims to clarify the mechanism of the longitudinal response of a tunnel under normal faulting via a comprehensive analysis of available experimental data and numerical simulations.Four 1 g condition model te...This paper aims to clarify the mechanism of the longitudinal response of a tunnel under normal faulting via a comprehensive analysis of available experimental data and numerical simulations.Four 1 g condition model tests were reviewed and reanalysed to highlight the key characteristics of the tunnel response under normal faulting:S-shaped deformation and inverted S-shaped bending strain distribution in the longitudinal direction;the main affected zone of faulting is approximately six times the tunnel diameter to the fault plane.A threedimensional finite element model was also established and verified,followed by a sensitivity analysis of key parameters,including the fault dislocation,dip angle,tunnel rigidity and relative stiffness between the hanging wall and footwall.All results reveal that the longitudinal mechanical response under normal faulting is dominated by a combination of bending,tension,and shearing.Bending and shearing are induced by the large unbalanced rock pressure at the vault in the hanging wall and the inverted arch in the footwall;the value of unbalanced rock pressure is directly proportional to the dislocation but negatively correlated with the dip angle.Although the main part of the tunnel stays in tension,axial compressive strain exists around the fault plane when the dip angle is greater than 70 °,which may be related to the ovaling effect of the tunnel.Such an ovaling effect is caused by the compression at the cross-section of the tunnel and may lead to more complicated internal strain.展开更多
文摘An optimal design configuration of leading edge extensions （LEXs） is presented based on the standard genetic algorithms （GAs）. Aircraft longitudinal dynamic response of the system with and without LEX is analyzed by solving the state equation of aircraft longitudinal motion. Aerodynamic force, moments, and longitudinal stability derivatives are estimated by three-dimensional low-order panel method. A novel aircraft model with LEX is optimized and its lift curve slope is increased by 13%-17% for Ma=0. 4-0. 9 and 12% for Ma=1. 5. Numerical results show that because the frequency and damping ratio in a short period are improved, the aircraft rapidly responds to a specified deflection control input in the battle area when LEX is installed. Finally, compared the results from the panel method with those from the Cy-20 aircraft flight test data,aerodynamic characteristics are verified.
基金supported by the Shanghai Municipal Science and Technology Project,China(Grant No.21XD1430900)the Fundamental Research Funds for the Central Universities,the Top Discipline Plan of Shanghai Universities-Class I(Grant No.2022-3-YB-02)Open Research Project from Key Laboratory of Geotechnical and Underground Engineering,Tongji University,China(Grant No.KLE-TJGE-B2101).
文摘The surcharge load at the ground surface inevitably breaks the original equilibrium state between the underneath tunnel and the surrounding soil,which will impact the service performance of a subway tunnel.This paper presents a novel semi-analytical approach for assessing the time-dependent,longitudinal responses of a subway tunnel in soft soil strata induced by the surcharge load.The solution is developed based on the framework of the classical"two-stage method"but innovatively incorporates the effects of ground stratification,the consolidation process,and the longitudinal stiffness reduction of the lining.Biot’s poroelastic theory in conjunction with the Laplace-Fourier transform technique is selected to model the deformation of the stratified ground,while the Timoshenko beam on a Pasternak foundation is employed to model the mechanical responses of the tunnel.The proposed semi-analytical solution is validated not only by comparison with benchmark solutions and a finite element model,but also by predicting a well-documented field measurement.Parametric analyses are conducted to investigate the effects of the elastic modulus and the permeability coefficient of the stratified ground on the longitudinal responses of the tunnel.It is expected that the proposed solution can serve as a useful tool for evaluating the effects of the surcharge load on the longitudinal responses of a subway tunnel.
基金National Natural Science Foundation of China under Grant No.51478247。
文摘For the longitudinal seismic response analysis of a tunnel structure under asynchronous earthquake excitations,a longitudinal integral response deformation method classified as a practical approach is proposed in this paper.The determinations of the structural critical moments when maximal deformations and internal forces in the longitudinal direction occur are deduced as well.When applying the proposed method,the static analysis of the free-field computation model subjected to the least favorable free-field deformation at the tunnel buried depth is performed first to calculate the equivalent input seismic loads.Then,the equivalent input seismic loads are imposed on the integral tunnel-foundation computation model to conduct the static calculation.Afterwards,the critical longitudinal seismic responses of the tunnel are obtained.The applicability of the new method is verified by comparing the seismic responses of a shield tunnel structure in Beijing,determined by the proposed procedure and by a dynamic time-history analysis under a series of obliquely incident out-of-plane and in-plane waves.The results show that the proposed method has a clear concept with high accuracy and simple progress.Meanwhile,this method provides a feasible way to determine the critical moments of the longitudinal seismic responses of a tunnel structure.Therefore,the proposed method can be effectively applied to analyze the seismic response of a long-line underground structure subjected to non-uniform excitations.
基金finically supported by the National Natural Science Foundation of China(No.41941018),2019QZKK0708Key Technology Research on Water Diversion Project for Central Area of Yunnan Province.
文摘This paper aims to clarify the mechanism of the longitudinal response of a tunnel under normal faulting via a comprehensive analysis of available experimental data and numerical simulations.Four 1 g condition model tests were reviewed and reanalysed to highlight the key characteristics of the tunnel response under normal faulting:S-shaped deformation and inverted S-shaped bending strain distribution in the longitudinal direction;the main affected zone of faulting is approximately six times the tunnel diameter to the fault plane.A threedimensional finite element model was also established and verified,followed by a sensitivity analysis of key parameters,including the fault dislocation,dip angle,tunnel rigidity and relative stiffness between the hanging wall and footwall.All results reveal that the longitudinal mechanical response under normal faulting is dominated by a combination of bending,tension,and shearing.Bending and shearing are induced by the large unbalanced rock pressure at the vault in the hanging wall and the inverted arch in the footwall;the value of unbalanced rock pressure is directly proportional to the dislocation but negatively correlated with the dip angle.Although the main part of the tunnel stays in tension,axial compressive strain exists around the fault plane when the dip angle is greater than 70 °,which may be related to the ovaling effect of the tunnel.Such an ovaling effect is caused by the compression at the cross-section of the tunnel and may lead to more complicated internal strain.
