In order to study the effect of temperature difference load （TDL） along the vertical direction of a simply supported beam bridge section on the vertical irregularity, a rail-bridge-piers calculation model was establ...In order to study the effect of temperature difference load （TDL） along the vertical direction of a simply supported beam bridge section on the vertical irregularity, a rail-bridge-piers calculation model was established. Taking 32 m simply supported box beam bridge which is widely used in the construction of pas- senger dedicated line in China as an example, influences of the temperature variation between the bottom and top of the bridge, temperature curve index, type of temperature gradient, and beam height on track vertical irregularity were analyzed with the model. The results show that TDL has more effects on long wave track irregularity than on short one, and the wavelength mainly affected is approxi- mately equal to the beam span. The amplitude of irregu- larity caused by TDL is largely affected by the temperature variation, temperature curve index, and type of temperature gradient, so it is necessary to monitor the temperaturedistribution of bridges in different regions to provide accurate calculation parameters. In order to avoid the irregularity exceeding the limit values, the height of 32, 48, and 64 m simply supported box beam bridges must not be less than 2.15, 3.2, and 4.05 m, respectively.展开更多
Using the inverse method, the analytical solution of a simply supported piezoelectric beam subjected to a uniformly distributed loading has been studied.First,the polynomials of stress function and induction function ...Using the inverse method, the analytical solution of a simply supported piezoelectric beam subjected to a uniformly distributed loading has been studied.First,the polynomials of stress function and induction function are given.Then, considering the gradient properties of the elastic parameter and the potential funciton as well as the piezoelectric parameter,the analytical solution of a simply supported beam subjected to a uniformly distributed loading is obtained and discussed.展开更多
A novel approach for analyzing coupled vibrations between vehicles and bridges is presented,taking into account spatiotemporal effects and mechanical phenomena resulting fromvehicle braking.Efficient modeling and solu...A novel approach for analyzing coupled vibrations between vehicles and bridges is presented,taking into account spatiotemporal effects and mechanical phenomena resulting fromvehicle braking.Efficient modeling and solution of bridge vibrations induced by vehicle deceleration are realized using this method.The method’s validity and reliability are substantiated through numerical examples.A simply supported beam bridge with a corrugated steel web is taken as an example and the effects of parameters such as the initial vehicle speed,braking acceleration,braking location,and road surface roughness on the mid-span displacement and impact factor of the bridge are analyzed.The results show that vehicle braking significantly amplifies mid-span displacement and impact factor responses in comparison to uniform vehicular motion across the bridge.Notably,the influence of wheelto-bridge friction forces is of particular significance and cannot be overlooked.When the vehicle initiates braking near the middle of the span,both the mid-span displacement and impact factor of the bridge exhibit substantial increases,further escalating with higher braking acceleration.Under favorable road surface conditions,the midspan displacement and the impact factor during vehicle braking may exceed the design values stipulated by codes.It is important to note that road surface roughness exerts a more pronounced effect on the impact factor of the bridge in comparison to the effects of vehicle braking.展开更多
The stability and local bifurcation of a simply-supported flexible beam （Bernoulli- Euler type） carrying a moving mass and subjected to harmonic axial excitation are investigated. In the theoretical analysis, the pa...The stability and local bifurcation of a simply-supported flexible beam （Bernoulli- Euler type） carrying a moving mass and subjected to harmonic axial excitation are investigated. In the theoretical analysis, the partial differential equation of motion with the fifth-order nonlinear term is solved using the method of multiple scales （a perturbation technique）. The stability and local bifurcation of the beam are analyzed for 1/2 sub harmonic resonance. The results show that some of the parameters, especially the velocity of moving mass and external excitation, affect the local bifurcation significantly. Therefore, these parameters play important roles in the system stability.展开更多
The tangent stiffness matrix of Timoshenko beam element is applied in the buckling of multi-step beams under several concentrated axial forces with elastic supports. From the governing differential equation of lateral...The tangent stiffness matrix of Timoshenko beam element is applied in the buckling of multi-step beams under several concentrated axial forces with elastic supports. From the governing differential equation of lateral deflection including second-order effects,the relationship of force versus displacement is established. In the formulation of finite element method (FEM),the stiffness matrix developed has the same accuracy with the solution of exact differential equations. The proposed tangent stiffness matrix will degenerate into the Bernoulli-Euler beam without the effects of shear deformation. The critical buckling force can be determined from the determinant element assemblage by FEM. The equivalent stiffness matrix constructed by the topmost deflection and slope is established by static condensation method,and then a recurrence formula is proposed. The validity and efficiency of the proposed method are shown by solving various numerical examples found in the literature.展开更多
Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current collection performance of the pantograph-catenary system,a study has been conducted to s...Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current collection performance of the pantograph-catenary system,a study has been conducted to support the beam deflector optimization using a combination of experimental measurements and computational fluid dynamics(CFD)simulations.The results demonstrate that the size,position,and installation orientation of the wind deflectors significantly influence the amount of force compensation.They also indicate that the front strip deflectors should be installed downwards and the rear strip deflectors upwards,thereby forming a“π”shape.Moreover,the lift force compensation provided by the wind deflectors increases with the size of the deflector.Alternative wind compensation strategies,such as control circuits,are also discussed,putting emphasis on the pros and cons of various pantograph types and wind compensation approaches.展开更多
A three-dimensional laminar steady state numerical model was used to investigate the influence of an alternating current(ac)magnetic field during single pass high power laser beam keyhole welding of 20 mm thick alumin...A three-dimensional laminar steady state numerical model was used to investigate the influence of an alternating current(ac)magnetic field during single pass high power laser beam keyhole welding of 20 mm thick aluminum.The three-dimensional heat transfer,fluid dynamics and electromagnetic field equations were solved with the commercial finite element package COMSOL Multiphysics.Dominant physical effects of the process were taken into account:Thermo-capillary(Marangoni)convection at the upper and lower weld pool surfaces,natural convection due to the gravity influence and the latent heat of solid-liquid phase transition.Simulations were conducted for several magnetic field strengths and it was found that the gravity drop-out associated with welding of thick plates due to the hydrostatic pressure can be prevented by the application of an ac magnetic field below the weld specimen of around 70 mT(rms)at an oscillation frequency of 450 Hz.The inductive support system allows for single-pass laser beam welding of thick aluminum plates.The flow pattern in the molten zone and the temperature distributions are significantly changed by the application of the electromagnetic forces in the weld pool.展开更多
Spherical pressure vessels in large sizes are generally supported on legs or columns evenly spaced around the circumference. The legs are attached at or near the equator of the sphere. This research work focussed on f...Spherical pressure vessels in large sizes are generally supported on legs or columns evenly spaced around the circumference. The legs are attached at or near the equator of the sphere. This research work focussed on flexural-torsional buckling of beam-column supports of field fabricated spherical pressure vessels using finite element analysis. Flexuraltorsional buckling is an important limit state that must be considered in structural steel design and it occurs when a structural member experiences significant out-of-plane bending and twisting. This research has therefore considered the total potential energy equation for the flexural-torsional buckling of a beam-column element. The energy equation was formulated by summing the strain energy and the potential energy of the external loads. The finite element method was applied in conjunction with the energy method to analyze the flexural-torsional buckling of beam-column supports. To apply the finite element method, the displacement functions are assumed to be cubic polynomials, and the shape functions used to derive the element stiffness and element geometric stiffness matrices. The element stiffness and geometric stiffness matrices were assembled to obtain the global stiffness matrices of the structure. The final finite element equation obtained was in the form of an eigenvalue problem. The flexural-torsional buckling loads of the structure were determined by solving for the eigenvalue of the equation. The resulting eigenvalue equation from the finite element analysis was coded using FORTRAN 90 programming language to aid in the analysis process. To validate FORTRAN 90 coding developed for the finite element analysis and the methodology, the results given by the software were compared to existing solutions and showed no significant difference P > 0.05.展开更多
This article analyzes the design of a variable-height simply supported steel truss bridge based on an actual project.It includes its basic situation,introduction to variable-height simply supported steel truss bridges...This article analyzes the design of a variable-height simply supported steel truss bridge based on an actual project.It includes its basic situation,introduction to variable-height simply supported steel truss bridges,key design points of such bridges,and finite element analysis of the design effect.The analysis shows that for such bridges,reasonable main structure design and node design are the keys to determining the overall design idea,and through the reasonable application of the finite element analysis method,the design effect can be scientifically determined,providing a reference for the subsequent structural design of such projects.展开更多
In the present study, finite element dynamic analysis or time history analysis of two-span beams subjected to asynchronous multi-support motions is carried out by using the moving support finite element. The elemental...In the present study, finite element dynamic analysis or time history analysis of two-span beams subjected to asynchronous multi-support motions is carried out by using the moving support finite element. The elemental equation of the element is based on total displacements and is derived under the concept of the quasi-static displacement decomposition. The use of moving support element shows that the element is very simple and convenient to represent continuous beam moving, deforming and vibrating simultaneously due to support motions. The comparison between the numerical results and analytical solutions indicates that the FE result agrees with the analytical solution.展开更多
基金supported by the National Science Foundation (U1234201)the Doctorial Innovation Fund of Southwest Jiaotong University
文摘In order to study the effect of temperature difference load （TDL） along the vertical direction of a simply supported beam bridge section on the vertical irregularity, a rail-bridge-piers calculation model was established. Taking 32 m simply supported box beam bridge which is widely used in the construction of pas- senger dedicated line in China as an example, influences of the temperature variation between the bottom and top of the bridge, temperature curve index, type of temperature gradient, and beam height on track vertical irregularity were analyzed with the model. The results show that TDL has more effects on long wave track irregularity than on short one, and the wavelength mainly affected is approxi- mately equal to the beam span. The amplitude of irregu- larity caused by TDL is largely affected by the temperature variation, temperature curve index, and type of temperature gradient, so it is necessary to monitor the temperaturedistribution of bridges in different regions to provide accurate calculation parameters. In order to avoid the irregularity exceeding the limit values, the height of 32, 48, and 64 m simply supported box beam bridges must not be less than 2.15, 3.2, and 4.05 m, respectively.
文摘Using the inverse method, the analytical solution of a simply supported piezoelectric beam subjected to a uniformly distributed loading has been studied.First,the polynomials of stress function and induction function are given.Then, considering the gradient properties of the elastic parameter and the potential funciton as well as the piezoelectric parameter,the analytical solution of a simply supported beam subjected to a uniformly distributed loading is obtained and discussed.
基金supported by the Henan Provincial Science and Technology Research Project under Grant(152102310295).
文摘A novel approach for analyzing coupled vibrations between vehicles and bridges is presented,taking into account spatiotemporal effects and mechanical phenomena resulting fromvehicle braking.Efficient modeling and solution of bridge vibrations induced by vehicle deceleration are realized using this method.The method’s validity and reliability are substantiated through numerical examples.A simply supported beam bridge with a corrugated steel web is taken as an example and the effects of parameters such as the initial vehicle speed,braking acceleration,braking location,and road surface roughness on the mid-span displacement and impact factor of the bridge are analyzed.The results show that vehicle braking significantly amplifies mid-span displacement and impact factor responses in comparison to uniform vehicular motion across the bridge.Notably,the influence of wheelto-bridge friction forces is of particular significance and cannot be overlooked.When the vehicle initiates braking near the middle of the span,both the mid-span displacement and impact factor of the bridge exhibit substantial increases,further escalating with higher braking acceleration.Under favorable road surface conditions,the midspan displacement and the impact factor during vehicle braking may exceed the design values stipulated by codes.It is important to note that road surface roughness exerts a more pronounced effect on the impact factor of the bridge in comparison to the effects of vehicle braking.
文摘The stability and local bifurcation of a simply-supported flexible beam （Bernoulli- Euler type） carrying a moving mass and subjected to harmonic axial excitation are investigated. In the theoretical analysis, the partial differential equation of motion with the fifth-order nonlinear term is solved using the method of multiple scales （a perturbation technique）. The stability and local bifurcation of the beam are analyzed for 1/2 sub harmonic resonance. The results show that some of the parameters, especially the velocity of moving mass and external excitation, affect the local bifurcation significantly. Therefore, these parameters play important roles in the system stability.
基金Sponsored by the National Key Technology Research and Development Program (Grant No.2006BAJ12B03-2)
文摘The tangent stiffness matrix of Timoshenko beam element is applied in the buckling of multi-step beams under several concentrated axial forces with elastic supports. From the governing differential equation of lateral deflection including second-order effects,the relationship of force versus displacement is established. In the formulation of finite element method (FEM),the stiffness matrix developed has the same accuracy with the solution of exact differential equations. The proposed tangent stiffness matrix will degenerate into the Bernoulli-Euler beam without the effects of shear deformation. The critical buckling force can be determined from the determinant element assemblage by FEM. The equivalent stiffness matrix constructed by the topmost deflection and slope is established by static condensation method,and then a recurrence formula is proposed. The validity and efficiency of the proposed method are shown by solving various numerical examples found in the literature.
文摘Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current collection performance of the pantograph-catenary system,a study has been conducted to support the beam deflector optimization using a combination of experimental measurements and computational fluid dynamics(CFD)simulations.The results demonstrate that the size,position,and installation orientation of the wind deflectors significantly influence the amount of force compensation.They also indicate that the front strip deflectors should be installed downwards and the rear strip deflectors upwards,thereby forming a“π”shape.Moreover,the lift force compensation provided by the wind deflectors increases with the size of the deflector.Alternative wind compensation strategies,such as control circuits,are also discussed,putting emphasis on the pros and cons of various pantograph types and wind compensation approaches.
基金Item Sponsored by the Deutsche Forschungsgemeinschaft (BonnGermany) under Grant No.DFG GU 1211/2-1
文摘A three-dimensional laminar steady state numerical model was used to investigate the influence of an alternating current(ac)magnetic field during single pass high power laser beam keyhole welding of 20 mm thick aluminum.The three-dimensional heat transfer,fluid dynamics and electromagnetic field equations were solved with the commercial finite element package COMSOL Multiphysics.Dominant physical effects of the process were taken into account:Thermo-capillary(Marangoni)convection at the upper and lower weld pool surfaces,natural convection due to the gravity influence and the latent heat of solid-liquid phase transition.Simulations were conducted for several magnetic field strengths and it was found that the gravity drop-out associated with welding of thick plates due to the hydrostatic pressure can be prevented by the application of an ac magnetic field below the weld specimen of around 70 mT(rms)at an oscillation frequency of 450 Hz.The inductive support system allows for single-pass laser beam welding of thick aluminum plates.The flow pattern in the molten zone and the temperature distributions are significantly changed by the application of the electromagnetic forces in the weld pool.
文摘Spherical pressure vessels in large sizes are generally supported on legs or columns evenly spaced around the circumference. The legs are attached at or near the equator of the sphere. This research work focussed on flexural-torsional buckling of beam-column supports of field fabricated spherical pressure vessels using finite element analysis. Flexuraltorsional buckling is an important limit state that must be considered in structural steel design and it occurs when a structural member experiences significant out-of-plane bending and twisting. This research has therefore considered the total potential energy equation for the flexural-torsional buckling of a beam-column element. The energy equation was formulated by summing the strain energy and the potential energy of the external loads. The finite element method was applied in conjunction with the energy method to analyze the flexural-torsional buckling of beam-column supports. To apply the finite element method, the displacement functions are assumed to be cubic polynomials, and the shape functions used to derive the element stiffness and element geometric stiffness matrices. The element stiffness and geometric stiffness matrices were assembled to obtain the global stiffness matrices of the structure. The final finite element equation obtained was in the form of an eigenvalue problem. The flexural-torsional buckling loads of the structure were determined by solving for the eigenvalue of the equation. The resulting eigenvalue equation from the finite element analysis was coded using FORTRAN 90 programming language to aid in the analysis process. To validate FORTRAN 90 coding developed for the finite element analysis and the methodology, the results given by the software were compared to existing solutions and showed no significant difference P > 0.05.
文摘This article analyzes the design of a variable-height simply supported steel truss bridge based on an actual project.It includes its basic situation,introduction to variable-height simply supported steel truss bridges,key design points of such bridges,and finite element analysis of the design effect.The analysis shows that for such bridges,reasonable main structure design and node design are the keys to determining the overall design idea,and through the reasonable application of the finite element analysis method,the design effect can be scientifically determined,providing a reference for the subsequent structural design of such projects.
文摘In the present study, finite element dynamic analysis or time history analysis of two-span beams subjected to asynchronous multi-support motions is carried out by using the moving support finite element. The elemental equation of the element is based on total displacements and is derived under the concept of the quasi-static displacement decomposition. The use of moving support element shows that the element is very simple and convenient to represent continuous beam moving, deforming and vibrating simultaneously due to support motions. The comparison between the numerical results and analytical solutions indicates that the FE result agrees with the analytical solution.
