Running safety assessment and tracking irregularity parametric sensitivity analysis of high-speed maglev train-bridge system are of great concern,especially need perfect refinement models in which all properties can b...Running safety assessment and tracking irregularity parametric sensitivity analysis of high-speed maglev train-bridge system are of great concern,especially need perfect refinement models in which all properties can be well characterized based on various stochastic excitations.A three-dimensional refined spatial random vibration analysis model of high-speed maglev train-bridge coupled system is established in this paper,in which multi-source uncertainty excitation can be considered simultaneously,and the probability density evolution method(PDEM)is adopted to reveal the system-specific uncertainty dynamic characteristic.The motion equation of the maglev vehicle model is composed of multi-rigid bodies with a total 210-degrees of freedom for each vehicle,and a refined electromagnetic force-air gap model is used to account for the interaction and coupling effect between the moving train and track beam bridges,which are directly established by using finite element method.The model is proven to be applicable by comparing with Monte Carlo simulation.By applying the proposed stochastic framework to the high maglev line,the random dynamic responses of maglev vehicles running on the bridges are studied for running safety and stability assessment.Moreover,the effects of track irregularity wavelength range under different amplitude and running speeds on the coupled system are investigated.The results show that the augmentation of train speed will move backward the sensitive wavelength interval,and track irregularity amplitude influences the response remarkably in the sensitive interval.展开更多
Extensive high-speed railway(HSR)network resembled the intricate vascular system of the human body,crisscrossing mainlands.Seismic events,known for their unpredictability,pose a significant threat to both trains and b...Extensive high-speed railway(HSR)network resembled the intricate vascular system of the human body,crisscrossing mainlands.Seismic events,known for their unpredictability,pose a significant threat to both trains and bridges,given the HSR’s extended operational duration.Therefore,ensuring the running safety of train-bridge coupled(TBC)system,primarily composed of simply supported beam bridges,is paramount.Traditional methods like the Monte Carlo method fall short in analyzing this intricate system efficiently.Instead,efficient algorithm like the new point estimate method combined with moment expansion approximation(NPEM-MEA)is applied to study random responses of numerical simulation TBC systems.Validation of the NPEM-MEA’s feasibility is conducted using the Monte Carlo method.Comparative analysis confirms the accuracy and efficiency of the method,with a recommended truncation order of four to six for the NPEM-MEA.Additionally,the influences of seismic magnitude and epicentral distance are discussed based on the random dynamic responses in the TBC system.This methodology not only facilitates seismic safety assessments for TBC systems but also contributes to standard-setting for these systems under earthquake conditions.展开更多
Aiming at the problem that it is difficult to obtain the explicit expression of the structural matrix in the traditional train-bridge coupling vibration analysis,a combined simulation system of train-bridge coupling s...Aiming at the problem that it is difficult to obtain the explicit expression of the structural matrix in the traditional train-bridge coupling vibration analysis,a combined simulation system of train-bridge coupling system(TBCS)under earthquake(MAETB)is developed based on the cooperative work of MATLAB and ANSYS.The simulation system is used to analyze the dynamic parameters of the TBCS of a prestressed concrete continuous rigid frame bridge benchmark model of a heavy-haul railway.The influence of different driving speeds,seismic wave intensities,and traveling wave effects on the dynamic response of the TBCS under the actions of the earthquakes is discussed.The results show that the bridge displacement increase in magnitude in the lateral direction is more significant than in the vertical direction under the action of an earthquake.The traveling wave effect can significantly reduce the lateral response of the bridge,but it will significantly increase the train derailment coefficient.When the earthquake intensity exceeds 0.2 g,the partial derailment coefficient of the train has exceeded the limit value of the specification.展开更多
Serviceability and running safety of the high-speed train on/through a bridge are of major concern in China.Due to the uncertainty chain of the train dynamic analysis in crosswinds originating mainly from the aerodyna...Serviceability and running safety of the high-speed train on/through a bridge are of major concern in China.Due to the uncertainty chain of the train dynamic analysis in crosswinds originating mainly from the aerodynamic assessment,this paper primarily reviews five meaningful progresses on the aerodynamics of the train-bridge system done by Wind Tunnel Laboratory of Central South University in the past several years.Firstly,the flow around the train and the uncertainty origin of the aerodynamic assessment are described from the fluid mechanism point of view.After a brief introduction of the current aerodynamic assessment methods with their strengths and weaknesses,a new-developed TRAIN-INFRASTRUCTURE rig with the maximum launch speed of 35 m/s is introduced.Then,several benchmark studies are presented,including the statistic results of the characterized geometry parameters of the currently utilized bridge-decks,the aerodynamics of the train,and the aerodynamics of the flat box/truss bridge-decks.Upon compared with the foregoing mentioned benchmarks,this paper highlights the aerodynamic interference of the train-bridge system associated with its physical natures.Finally,a porosity-and orientation-adjustable novel wind barrier with its effects on the aerodynamics of the train-bridge system is discussed.展开更多
To improve the safety of trains running in an undesirable wind environment,a novel louver-type wind barrier is proposed and further studied in this research using a scaled wind tunnel simulation with 1:40 scale models...To improve the safety of trains running in an undesirable wind environment,a novel louver-type wind barrier is proposed and further studied in this research using a scaled wind tunnel simulation with 1:40 scale models.Based on the aerodynamic performance of the train-bridge system,the parameters of the louver-type wind barrier are optimized.Compared to the case without a wind barrier,it is apparent that the wind barrier improves the running safety of trains,since the maximum reduction of the moment coefficient of the train reaches 58%using the louver-type wind barrier,larger than that achieved with conventional wind barriers(fence-type and grid-type).A louver-type wind barrier has more blade layers,and the rotation angle of the adjustable blade of the louver-type wind barrier is 90–180°(which induces the flow towards the deck surface),which is more favorable for the aerodynamic performance of the train.Comparing the 60°,90°and 120°wind fairings of the louver-type wind barrier blade,the blunt fairing is disadvantageous to the operational safety of the train.展开更多
The train-bridge dynamic interaction problem began with the development of railway technology, and requires an evaluation method for bridge design in order to ensure the safety and stability of the bridge and the runn...The train-bridge dynamic interaction problem began with the development of railway technology, and requires an evaluation method for bridge design in order to ensure the safety and stability of the bridge and the running train. This problem is studied using theoretical analysis, numerical simulation, and experimental study. In the train-bridge dynamic interaction system proposed in this paper, the train vehicle model is established by the rigid-body dynamics method, the bridge model is established by the finite element method, and the wheel/rail vertical and lateral interaction are simulated by the corresponding assumption and the Kalker linear creep theory, respectively. Track irregularity, structure deformation, wind load, collision load, structural damage, foundation scouring, and earthquake action are regarded as the excitation for the system. The train-bridge dynamic interaction system is solved by inter-history iteration. A case study of the dynamic response of a CRH380BL high-speed train running through a standard-design bridge in China is discussed. The dynamic responses of the vehicle and of the bridge subsystems are obtained for speeds ranging from 200 km-b-1 to 400 km.h-1, and the vibration mechanism are analyzed.展开更多
Earthquake is a kind of sudden and destructive random excitation in nature.It is significant to determine the probability distribution characteristics of the corresponding dynamic indicators to ensure the safety and t...Earthquake is a kind of sudden and destructive random excitation in nature.It is significant to determine the probability distribution characteristics of the corresponding dynamic indicators to ensure the safety and the stability of structures when the intensive seismic excitation,the intensity of which is larger than 7,acts in train-bridge system.Firstly,the motion equations of a two-dimensional train-bridge system under the vertical random excitation of track irregularity and the vertical seismic acceleration are established,where the train subsystem is composed of 8 mutually independent vehicle elements with 48 degrees of freedom,while the single-span simple supported bridge subsystem is composed of 102D beam elements with 20 degrees of freedom on beam and 2 large mass degrees of freedom at the support.Secondly,Monte Carlo method and pseudo excitation method are adopted to analyze the statistical parameters of the system.The power spectrum density of random excitation is used to define a series of non-stationary pseudo excitation in pseudo excitation method and the trigonometric series of random vibration history samples in Monte Carlo method,respectively solved by precise integral method and Newmark-βmethod through the inter-system iterative procedure.Finally,the results are compared with the case under the weak seismic excitation,and show that the samples of vertical acceleration response of bridge and the offload factor of train obeys the normal distribution.In a high probability,the intensive earthquakes pose a greater threat to the safety and stability of bridges and trains than the weak ones.展开更多
In recent years,high-speed railways in China have developed very rapidly,and the number and span of the railway bridges are keeping increasing.Meanwhile,frequent extreme disasters,such as strong winds,earthquakes and ...In recent years,high-speed railways in China have developed very rapidly,and the number and span of the railway bridges are keeping increasing.Meanwhile,frequent extreme disasters,such as strong winds,earthquakes and floods,pose a significant threat to the safety of the train–bridge systems.Therefore,it is of paramount importance to evaluate the safety and comfort of trains when crossing a bridge under external excitations.In these aspects,there is abundant research but lacks a literature review.Therefore,this paper provides a comprehensive state-of-the-art review of research works on train–bridge systems under external excitations,which includes crosswinds,waves,collision loads and seismic loads.The characteristics of external excitations,the models of the train–bridge systems under external excitations,and the representative research results are summarized and analyzed.Finally,some suggestions for further research of the coupling vibration of train–bridge system under external excitations are presented.展开更多
To investigate the aerodynamic effect of wind barriers on a high-speed train-bridge system,a sectional model test was conducted in a closed-circuit-type wind tunnel.Several different cases,including with and without b...To investigate the aerodynamic effect of wind barriers on a high-speed train-bridge system,a sectional model test was conducted in a closed-circuit-type wind tunnel.Several different cases,including with and without barriers,with different barrier heights and porosity rates,and with different train arrangements on the bridge were taken into consideration;in addition,the aerodynamic coefficients of the train-bridge system were measured.It is found that the side force and rolling moment coefficients of the vehicle are efficiently reduced by a single-side wind barrier,but for the bridge deck these values are increased.The height and porosity rate of the barrier are two important factors that influence the windbreak effect.Train arrangement on the bridge will considerably influence the aerodynamic properties of the train-bridge system.The side force and rolling moment coefficients of the vehicle at the windward side are larger than at the leeward side.展开更多
Urban transportation systems are facing severe challenges due to the rapid growth of the urban population,especially in China.Suspended monorail system(SMS),as a sky rail transportation form,can effectively alleviate ...Urban transportation systems are facing severe challenges due to the rapid growth of the urban population,especially in China.Suspended monorail system(SMS),as a sky rail transportation form,can effectively alleviate urban traffic congestion due to its independent right-of-way and minimal ground footprint.However,the SMS possesses a special traveling system with unique vehicle structure and bridge configuration,which results in significant differences in both the mechanisms and dynamics problems associated with train–bridge interaction(TBI)when contrasted with those of traditional railway systems.Therefore,a thorough understanding of the SMS dynamics is essential for ensuring the operational safety of the system.This article presents a state-of-the-art review of the TBI modeling methodologies,critical dynamic features,field tests,and practice of the SMS in China.Firstly,the development history,technical features,and potential dynamics problems of the SMS are briefly described,followed by the mechanical characteristics and mechanisms of the train–bridge interactive systems.Then,the modeling methodology of the fundamental elements in the suspended monorail TBI is systematically reviewed,including the suspended train subsystem,bridge subsystem,train–bridge interaction relationships,system excitations,and solution method.Further,the typical dynamic features of the TBI under various operational scenarios are elaborated,including different train speeds,a variety of line sections,and a natural wind environment.Finally,the first new energy-based SMS test line in the world is systematically introduced,including the composition and functionality of the system,the details of the conducted field tests,and the measured results of the typical dynamic responses.At the end of the paper,both the guidance on further improvement of the SMS and future research topics are proposed.展开更多
In this study a 3D numerical analysis approach is developed to predict the ground vibration around rigid-frame viaducts induced by running high-speed trains. The train-bridge-ground interaction system is divided into ...In this study a 3D numerical analysis approach is developed to predict the ground vibration around rigid-frame viaducts induced by running high-speed trains. The train-bridge-ground interaction system is divided into two subsystems： the train-bridge interaction and the soil-structure interaction. First, the analytical program to simulate bridge vibration with consideration of train-bridge interaction is developed to obtain the vibration reaction forces at the pier bottoms. The high- speed train is described by a multi-DOFs vibration system and the rigid-frame viaduct is modeled with 3D beam elements. Second, applying these vibration reaction forces as input external excitations, the ground vibration is simulated by using a general-purpose program that includes soil-structure interaction effects. The validity of the analytical procedure is confirmed by comparing analytical and experimental results. The characteristics of high-speed train-induced vibrations, including the location of predominant vibration, are clarified. Based on this information a proposed vibration countermeasure using steel strut and new barrier is found effective in reducing train-induced vibrations and it satisfies environmental vibration requirements. The vibration screening efficiency is evaluated by reduction VAL based on 1/3 octave band spectral analysis.展开更多
This paper focuses on understanding and evaluating the dynamic effect of the heavy-haul train system on the seismic performance of a long-span railway bridge. A systematic study on the effect of heavy-haul trains on b...This paper focuses on understanding and evaluating the dynamic effect of the heavy-haul train system on the seismic performance of a long-span railway bridge. A systematic study on the effect of heavy-haul trains on bridge seismic response has been conducted, considering the influence of vehicle modeling strategies and dynamic characteristics of the seismic waves. For this purpose, the performance of a long-span cable-stayed railway bridge is assessed with stationary trains atop it, where the heavy-haul vehicles are modeled in two different ways: the multi-rigid body model with suspension system and additional mass model. Comparison of the bridge response in the presence or absence of the train system has been conducted, and the vehicle loading situation, which includes full-load and no-load, is also discussed. The result shows that during the earthquake, the peak moment of the main girder and peak stress of stay cables increase by 80% and by 40% in the presence of fully loaded heavy-haul trains, respectively. At the same time, a considerable decrease appears in the peak acceleration of the main girder. This proves the existence of the damping effect of the heavy-haul train system, and this effect is more obvious for the fully loaded vehicles. Finally, this paper proposes an efficient vehicle modeling method with 2 degrees of freedom(DOF) for simplifying the treatment of the train system in bridge seismic checking.展开更多
Wind barriers are commonly adopted to prevent the effects of wind on high-speed railway trains,but their wind-proofing effects are greatly affected by substructures.To investigate the effects of wind barriers on the a...Wind barriers are commonly adopted to prevent the effects of wind on high-speed railway trains,but their wind-proofing effects are greatly affected by substructures.To investigate the effects of wind barriers on the aerodynamic characteristic of road-rail same-story truss bridge-train systems,wind tunnel experiments were carried out using a 1:50 scale model.Taking a wind barrier with a porosity of 30%as an example,the aerodynamic characteristics of the bridge train system under different wind barrier layouts(single-sided and double-sided),positions(inside and outside)and heights(2.5 m,3.0 m,3.5 m and 4.0 m)were tested.The results indicate that the downstream inside wind barrier has almost no effect on the aerodynamic characteristics of the train-bridge system,but the downstream outside wind barrier increases the drag coefficient of the bridge and reduces both the lift coefficient and drag coefficient of the train due to its effect on the trains wind pressure distribution,especially on the trains leeward surface.When the wind barriers are arranged on the outside,their effects on the drag coefficient of the bridge and shielding effect on the train are greater than when they are arranged on the inside.As the height of the wind barrier increases,the drag coefficient of the bridge also gradually increases,and the lift coefficient and drag coefficient of the train gradually decrease,but the degree of variation of the aerodynamic coefficient with the height is slightly different due to the different wind barrier layouts.When 3.0 m high double-sided wind barriers are arranged on the outside of the truss bridge,the drag coefficient of the bridge only increases by 12%,while the drag coefficient of the train decreases by 55%.展开更多
This study is intended to evaluate the influence of dynamic bridge-train interaction （BTI） on the seismic response of the Shinkansen system in Japan under moderate earthquakes. An analytical approach to simulate the...This study is intended to evaluate the influence of dynamic bridge-train interaction （BTI） on the seismic response of the Shinkansen system in Japan under moderate earthquakes. An analytical approach to simulate the seismic response of the BTI system is developed. In this approach, the behavior of the bridge structure is assumed to be within the elastic range under moderate ground motions. A bullet train car model idealized as a sprung-mass system is established. The viaduct is modeled with 3D finite elements. The BTI analysis algorithm is verified by comparing the analytical and experimental results. The seismic analysis is validated through comparison with a general program. Then, the seismic responses of the BTI system are simulated and evaluated. Some useful conclusions are drawn, indicating the importance of a proper consideration of the dynamic BTI in seismic design.展开更多
There is always some randomness in the material properties of a structure due to several circumstances and ignoring it increases the threat of inadequate structural safety reserves.A numerical approach is used in this...There is always some randomness in the material properties of a structure due to several circumstances and ignoring it increases the threat of inadequate structural safety reserves.A numerical approach is used in this study to consider the spatial variability of structural parameters.Statistical moments of the train and bridge responses were computed using the point estimation method(PEM),and the material characteristics of the bridge were set as random fields following Gaussian random distribution,which were discretized using Karhunen-Loève expansion(KLE).The following steps were carried out and the results are discussed herein.First,using the stochastic finite element method(SFEM),the mean value and standard deviation of dynamic responses of the train-bridge system(TBS)were examined.The effectiveness and accuracy of the computation were then confirmed by comparing the results to the Monte-Carlo simulation(MCS).Next,the influence of the train running speed,bridge vibration frequency,and span of the bridge on dynamic coefficient and dynamic response characteristics of resonance were discussed by using the SFEM.Finally,the lowest limit value of the vibration frequency of the simple supported bridges(SSB)with spans of 24 m,32 m,and 40 m are presented.展开更多
基金Project(2023YFB4302500)supported by the National Key R&D Program of ChinaProject(52078485)supported by the National Natural Science Foundation of ChinaProjects(2021-Major-16,2021-Special-08)supported by the Science and Technology Research and Development Program Project of China Railway Group Limited。
文摘Running safety assessment and tracking irregularity parametric sensitivity analysis of high-speed maglev train-bridge system are of great concern,especially need perfect refinement models in which all properties can be well characterized based on various stochastic excitations.A three-dimensional refined spatial random vibration analysis model of high-speed maglev train-bridge coupled system is established in this paper,in which multi-source uncertainty excitation can be considered simultaneously,and the probability density evolution method(PDEM)is adopted to reveal the system-specific uncertainty dynamic characteristic.The motion equation of the maglev vehicle model is composed of multi-rigid bodies with a total 210-degrees of freedom for each vehicle,and a refined electromagnetic force-air gap model is used to account for the interaction and coupling effect between the moving train and track beam bridges,which are directly established by using finite element method.The model is proven to be applicable by comparing with Monte Carlo simulation.By applying the proposed stochastic framework to the high maglev line,the random dynamic responses of maglev vehicles running on the bridges are studied for running safety and stability assessment.Moreover,the effects of track irregularity wavelength range under different amplitude and running speeds on the coupled system are investigated.The results show that the augmentation of train speed will move backward the sensitive wavelength interval,and track irregularity amplitude influences the response remarkably in the sensitive interval.
基金National Natural Science Foundation of China under Grant Nos.11972379 and 42377184,Hunan 100-Talent PlanNatural Science Foundation of Hunan Province under Grant No.2022JJ10079+1 种基金Hunan High-Level Talent Plan under Grant No.420030004Central South University Research Project under Grant Nos.202045006(Innovation-Driven Project)and 502390001。
文摘Extensive high-speed railway(HSR)network resembled the intricate vascular system of the human body,crisscrossing mainlands.Seismic events,known for their unpredictability,pose a significant threat to both trains and bridges,given the HSR’s extended operational duration.Therefore,ensuring the running safety of train-bridge coupled(TBC)system,primarily composed of simply supported beam bridges,is paramount.Traditional methods like the Monte Carlo method fall short in analyzing this intricate system efficiently.Instead,efficient algorithm like the new point estimate method combined with moment expansion approximation(NPEM-MEA)is applied to study random responses of numerical simulation TBC systems.Validation of the NPEM-MEA’s feasibility is conducted using the Monte Carlo method.Comparative analysis confirms the accuracy and efficiency of the method,with a recommended truncation order of four to six for the NPEM-MEA.Additionally,the influences of seismic magnitude and epicentral distance are discussed based on the random dynamic responses in the TBC system.This methodology not only facilitates seismic safety assessments for TBC systems but also contributes to standard-setting for these systems under earthquake conditions.
基金funded by the Open Projects Foundation of Engineering Research Center of Disaster Prevention and Mitigation of Southeast Coastal Engineering Structures of Fujian Province University(Grant No.2022009)the National Natural Science Foundation of China(Grant No.51708429)the Construction Science and Technology Plan Projects of Hubei Province(Grant No.2023011).
文摘Aiming at the problem that it is difficult to obtain the explicit expression of the structural matrix in the traditional train-bridge coupling vibration analysis,a combined simulation system of train-bridge coupling system(TBCS)under earthquake(MAETB)is developed based on the cooperative work of MATLAB and ANSYS.The simulation system is used to analyze the dynamic parameters of the TBCS of a prestressed concrete continuous rigid frame bridge benchmark model of a heavy-haul railway.The influence of different driving speeds,seismic wave intensities,and traveling wave effects on the dynamic response of the TBCS under the actions of the earthquakes is discussed.The results show that the bridge displacement increase in magnitude in the lateral direction is more significant than in the vertical direction under the action of an earthquake.The traveling wave effect can significantly reduce the lateral response of the bridge,but it will significantly increase the train derailment coefficient.When the earthquake intensity exceeds 0.2 g,the partial derailment coefficient of the train has exceeded the limit value of the specification.
基金Project(2017YFB1201204)supported by National Key R&D Program of ChinaProjects(51925808,U1934209)supported by the National Natural Science Foundation of China。
文摘Serviceability and running safety of the high-speed train on/through a bridge are of major concern in China.Due to the uncertainty chain of the train dynamic analysis in crosswinds originating mainly from the aerodynamic assessment,this paper primarily reviews five meaningful progresses on the aerodynamics of the train-bridge system done by Wind Tunnel Laboratory of Central South University in the past several years.Firstly,the flow around the train and the uncertainty origin of the aerodynamic assessment are described from the fluid mechanism point of view.After a brief introduction of the current aerodynamic assessment methods with their strengths and weaknesses,a new-developed TRAIN-INFRASTRUCTURE rig with the maximum launch speed of 35 m/s is introduced.Then,several benchmark studies are presented,including the statistic results of the characterized geometry parameters of the currently utilized bridge-decks,the aerodynamics of the train,and the aerodynamics of the flat box/truss bridge-decks.Upon compared with the foregoing mentioned benchmarks,this paper highlights the aerodynamic interference of the train-bridge system associated with its physical natures.Finally,a porosity-and orientation-adjustable novel wind barrier with its effects on the aerodynamics of the train-bridge system is discussed.
基金Project(2017T001-G)supported by the Science and Technology Research and Development Program of China Railway CorporationProject(2017YFB1201204)supported by the National Key Research and Development Program of China+2 种基金Project(U1534206)supported by the National Natural Science Foundation of ChinaProject(2015CX006)supported by the Innovation-driven Plan in Central South University,ChinaProject(2017zzts521)supported by the Fundamental Research Funds for the Central Universities,China
文摘To improve the safety of trains running in an undesirable wind environment,a novel louver-type wind barrier is proposed and further studied in this research using a scaled wind tunnel simulation with 1:40 scale models.Based on the aerodynamic performance of the train-bridge system,the parameters of the louver-type wind barrier are optimized.Compared to the case without a wind barrier,it is apparent that the wind barrier improves the running safety of trains,since the maximum reduction of the moment coefficient of the train reaches 58%using the louver-type wind barrier,larger than that achieved with conventional wind barriers(fence-type and grid-type).A louver-type wind barrier has more blade layers,and the rotation angle of the adjustable blade of the louver-type wind barrier is 90–180°(which induces the flow towards the deck surface),which is more favorable for the aerodynamic performance of the train.Comparing the 60°,90°and 120°wind fairings of the louver-type wind barrier blade,the blunt fairing is disadvantageous to the operational safety of the train.
基金Acknowledgements This research is sponsored by the Major State Basic Research Development Program of China （＂973＂ Program） （2013CB036203）, the 111 Project （B13002）, and the National Natural Science Foundation of China （U1434205, U1434210, 51338001 ）.
文摘The train-bridge dynamic interaction problem began with the development of railway technology, and requires an evaluation method for bridge design in order to ensure the safety and stability of the bridge and the running train. This problem is studied using theoretical analysis, numerical simulation, and experimental study. In the train-bridge dynamic interaction system proposed in this paper, the train vehicle model is established by the rigid-body dynamics method, the bridge model is established by the finite element method, and the wheel/rail vertical and lateral interaction are simulated by the corresponding assumption and the Kalker linear creep theory, respectively. Track irregularity, structure deformation, wind load, collision load, structural damage, foundation scouring, and earthquake action are regarded as the excitation for the system. The train-bridge dynamic interaction system is solved by inter-history iteration. A case study of the dynamic response of a CRH380BL high-speed train running through a standard-design bridge in China is discussed. The dynamic responses of the vehicle and of the bridge subsystems are obtained for speeds ranging from 200 km-b-1 to 400 km.h-1, and the vibration mechanism are analyzed.
基金Project(52178101) supported by the National Natural Science Foundation of China。
文摘Earthquake is a kind of sudden and destructive random excitation in nature.It is significant to determine the probability distribution characteristics of the corresponding dynamic indicators to ensure the safety and the stability of structures when the intensive seismic excitation,the intensity of which is larger than 7,acts in train-bridge system.Firstly,the motion equations of a two-dimensional train-bridge system under the vertical random excitation of track irregularity and the vertical seismic acceleration are established,where the train subsystem is composed of 8 mutually independent vehicle elements with 48 degrees of freedom,while the single-span simple supported bridge subsystem is composed of 102D beam elements with 20 degrees of freedom on beam and 2 large mass degrees of freedom at the support.Secondly,Monte Carlo method and pseudo excitation method are adopted to analyze the statistical parameters of the system.The power spectrum density of random excitation is used to define a series of non-stationary pseudo excitation in pseudo excitation method and the trigonometric series of random vibration history samples in Monte Carlo method,respectively solved by precise integral method and Newmark-βmethod through the inter-system iterative procedure.Finally,the results are compared with the case under the weak seismic excitation,and show that the samples of vertical acceleration response of bridge and the offload factor of train obeys the normal distribution.In a high probability,the intensive earthquakes pose a greater threat to the safety and stability of bridges and trains than the weak ones.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51978589 and 51778544).
文摘In recent years,high-speed railways in China have developed very rapidly,and the number and span of the railway bridges are keeping increasing.Meanwhile,frequent extreme disasters,such as strong winds,earthquakes and floods,pose a significant threat to the safety of the train–bridge systems.Therefore,it is of paramount importance to evaluate the safety and comfort of trains when crossing a bridge under external excitations.In these aspects,there is abundant research but lacks a literature review.Therefore,this paper provides a comprehensive state-of-the-art review of research works on train–bridge systems under external excitations,which includes crosswinds,waves,collision loads and seismic loads.The characteristics of external excitations,the models of the train–bridge systems under external excitations,and the representative research results are summarized and analyzed.Finally,some suggestions for further research of the coupling vibration of train–bridge system under external excitations are presented.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2013CB036203)the National Natural Science Foundation of China(Grant No.51308034)the"111"Project(Grant No.B13002)
文摘To investigate the aerodynamic effect of wind barriers on a high-speed train-bridge system,a sectional model test was conducted in a closed-circuit-type wind tunnel.Several different cases,including with and without barriers,with different barrier heights and porosity rates,and with different train arrangements on the bridge were taken into consideration;in addition,the aerodynamic coefficients of the train-bridge system were measured.It is found that the side force and rolling moment coefficients of the vehicle are efficiently reduced by a single-side wind barrier,but for the bridge deck these values are increased.The height and porosity rate of the barrier are two important factors that influence the windbreak effect.Train arrangement on the bridge will considerably influence the aerodynamic properties of the train-bridge system.The side force and rolling moment coefficients of the vehicle at the windward side are larger than at the leeward side.
基金supported by the National Natural Science Foundation of China(Grant Nos.52202483,52108476,and 52388102)。
文摘Urban transportation systems are facing severe challenges due to the rapid growth of the urban population,especially in China.Suspended monorail system(SMS),as a sky rail transportation form,can effectively alleviate urban traffic congestion due to its independent right-of-way and minimal ground footprint.However,the SMS possesses a special traveling system with unique vehicle structure and bridge configuration,which results in significant differences in both the mechanisms and dynamics problems associated with train–bridge interaction(TBI)when contrasted with those of traditional railway systems.Therefore,a thorough understanding of the SMS dynamics is essential for ensuring the operational safety of the system.This article presents a state-of-the-art review of the TBI modeling methodologies,critical dynamic features,field tests,and practice of the SMS in China.Firstly,the development history,technical features,and potential dynamics problems of the SMS are briefly described,followed by the mechanical characteristics and mechanisms of the train–bridge interactive systems.Then,the modeling methodology of the fundamental elements in the suspended monorail TBI is systematically reviewed,including the suspended train subsystem,bridge subsystem,train–bridge interaction relationships,system excitations,and solution method.Further,the typical dynamic features of the TBI under various operational scenarios are elaborated,including different train speeds,a variety of line sections,and a natural wind environment.Finally,the first new energy-based SMS test line in the world is systematically introduced,including the composition and functionality of the system,the details of the conducted field tests,and the measured results of the typical dynamic responses.At the end of the paper,both the guidance on further improvement of the SMS and future research topics are proposed.
基金Doctoral Scientific Research Startup Foundation of Wuhan University of Technology,China(No.40120246)Hubei Key Laboratory of Roadway Bridge and Structure Engineering(Wuhan University of Technology)(No.DQJJ201505)
文摘In this study a 3D numerical analysis approach is developed to predict the ground vibration around rigid-frame viaducts induced by running high-speed trains. The train-bridge-ground interaction system is divided into two subsystems： the train-bridge interaction and the soil-structure interaction. First, the analytical program to simulate bridge vibration with consideration of train-bridge interaction is developed to obtain the vibration reaction forces at the pier bottoms. The high- speed train is described by a multi-DOFs vibration system and the rigid-frame viaduct is modeled with 3D beam elements. Second, applying these vibration reaction forces as input external excitations, the ground vibration is simulated by using a general-purpose program that includes soil-structure interaction effects. The validity of the analytical procedure is confirmed by comparing analytical and experimental results. The characteristics of high-speed train-induced vibrations, including the location of predominant vibration, are clarified. Based on this information a proposed vibration countermeasure using steel strut and new barrier is found effective in reducing train-induced vibrations and it satisfies environmental vibration requirements. The vibration screening efficiency is evaluated by reduction VAL based on 1/3 octave band spectral analysis.
基金Project(51678576) supported by the National Natural Science Foundation of ChinaProject(2017YFB1201204) supported by the National Key R&D Program of China。
文摘This paper focuses on understanding and evaluating the dynamic effect of the heavy-haul train system on the seismic performance of a long-span railway bridge. A systematic study on the effect of heavy-haul trains on bridge seismic response has been conducted, considering the influence of vehicle modeling strategies and dynamic characteristics of the seismic waves. For this purpose, the performance of a long-span cable-stayed railway bridge is assessed with stationary trains atop it, where the heavy-haul vehicles are modeled in two different ways: the multi-rigid body model with suspension system and additional mass model. Comparison of the bridge response in the presence or absence of the train system has been conducted, and the vehicle loading situation, which includes full-load and no-load, is also discussed. The result shows that during the earthquake, the peak moment of the main girder and peak stress of stay cables increase by 80% and by 40% in the presence of fully loaded heavy-haul trains, respectively. At the same time, a considerable decrease appears in the peak acceleration of the main girder. This proves the existence of the damping effect of the heavy-haul train system, and this effect is more obvious for the fully loaded vehicles. Finally, this paper proposes an efficient vehicle modeling method with 2 degrees of freedom(DOF) for simplifying the treatment of the train system in bridge seismic checking.
基金Projects(52078504,51822803,51925808) supported by the National Natural Science Foundation of ChinaProject(2021RC3016) supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘Wind barriers are commonly adopted to prevent the effects of wind on high-speed railway trains,but their wind-proofing effects are greatly affected by substructures.To investigate the effects of wind barriers on the aerodynamic characteristic of road-rail same-story truss bridge-train systems,wind tunnel experiments were carried out using a 1:50 scale model.Taking a wind barrier with a porosity of 30%as an example,the aerodynamic characteristics of the bridge train system under different wind barrier layouts(single-sided and double-sided),positions(inside and outside)and heights(2.5 m,3.0 m,3.5 m and 4.0 m)were tested.The results indicate that the downstream inside wind barrier has almost no effect on the aerodynamic characteristics of the train-bridge system,but the downstream outside wind barrier increases the drag coefficient of the bridge and reduces both the lift coefficient and drag coefficient of the train due to its effect on the trains wind pressure distribution,especially on the trains leeward surface.When the wind barriers are arranged on the outside,their effects on the drag coefficient of the bridge and shielding effect on the train are greater than when they are arranged on the inside.As the height of the wind barrier increases,the drag coefficient of the bridge also gradually increases,and the lift coefficient and drag coefficient of the train gradually decrease,but the degree of variation of the aerodynamic coefficient with the height is slightly different due to the different wind barrier layouts.When 3.0 m high double-sided wind barriers are arranged on the outside of the truss bridge,the drag coefficient of the bridge only increases by 12%,while the drag coefficient of the train decreases by 55%.
基金Japan Society of the Promotion of Science (Grant-in-Aid for Scientif ic Research (B) Under Project No. 17360213)the Hyogo Science and Technology Association
文摘This study is intended to evaluate the influence of dynamic bridge-train interaction （BTI） on the seismic response of the Shinkansen system in Japan under moderate earthquakes. An analytical approach to simulate the seismic response of the BTI system is developed. In this approach, the behavior of the bridge structure is assumed to be within the elastic range under moderate ground motions. A bullet train car model idealized as a sprung-mass system is established. The viaduct is modeled with 3D finite elements. The BTI analysis algorithm is verified by comparing the analytical and experimental results. The seismic analysis is validated through comparison with a general program. Then, the seismic responses of the BTI system are simulated and evaluated. Some useful conclusions are drawn, indicating the importance of a proper consideration of the dynamic BTI in seismic design.
基金Open Fund of Hunan International Scientific and Technological Innovation Cooperation Base of Advanced Construction and Maintenance Technology of Highway(Changsha University of Science and Technology)Project Number kfj210803National Natural Science Foundation of China under Grant Nos.U1934207 and 11972379Fujian University of Technology under Grant No.GY-Z21181。
文摘There is always some randomness in the material properties of a structure due to several circumstances and ignoring it increases the threat of inadequate structural safety reserves.A numerical approach is used in this study to consider the spatial variability of structural parameters.Statistical moments of the train and bridge responses were computed using the point estimation method(PEM),and the material characteristics of the bridge were set as random fields following Gaussian random distribution,which were discretized using Karhunen-Loève expansion(KLE).The following steps were carried out and the results are discussed herein.First,using the stochastic finite element method(SFEM),the mean value and standard deviation of dynamic responses of the train-bridge system(TBS)were examined.The effectiveness and accuracy of the computation were then confirmed by comparing the results to the Monte-Carlo simulation(MCS).Next,the influence of the train running speed,bridge vibration frequency,and span of the bridge on dynamic coefficient and dynamic response characteristics of resonance were discussed by using the SFEM.Finally,the lowest limit value of the vibration frequency of the simple supported bridges(SSB)with spans of 24 m,32 m,and 40 m are presented.
