To explore the influence of spatially varying ground motion on the dynamic behavior of a train passing through a three-tower cable-stayed bridge,a 3D train–track–bridge coupled model is established for accurately si...To explore the influence of spatially varying ground motion on the dynamic behavior of a train passing through a three-tower cable-stayed bridge,a 3D train–track–bridge coupled model is established for accurately simulating the train–bridge interaction under earthquake excitation,which is made up of a vehicle model built by multi-body dynamics,a track–bridge finite element model,and a 3D rolling wheel–rail contact model.A conditional simulation method,which takes into consideration the wave passage effect,incoherence effect,and site-response effect,is adopted to simulate the spatially varying ground motion under different soil conditions.The multi-time-step method previously proposed by the authors is also adopted to improve computational efficiency.The dynamic responses of the train running on a three-tower cablestayed bridge are calculated with differing earthquake excitations and train speeds.The results indicate that(1)the earthquake excitation significantly increases the responses of the train–bridge system,but at a design speed,all the running safety indices meet the code requirements;(2)the incoherence and site-response effects should also be considered in the seismic analysis for long-span bridges though there is no fixed pattern for determining their influences;(3)different train speeds that vary the vibration characteristics of the train–bridge system affect the vibration frequencies of the car body and bridge.展开更多
Until now,seismic-isolation structures have not yet been applied in the railway field.The reason is that though a seismic-isolation structure can reduce the inertial force to the structure,the energy absorption causes...Until now,seismic-isolation structures have not yet been applied in the railway field.The reason is that though a seismic-isolation structure can reduce the inertial force to the structure,the energy absorption causes big response displacement on the structure,which adversely effects the running safety of the trains supported by the structure.In this paper,a methodology for seismic running safety assessment is introduced,and a new type of seismic-isolation foundation is proposed,which can convert the seismic response displacement in the lateral direction of track to the longitudinal direction that has a less adverse effect on the running safety of the train.The isolation foundation is composed of FPS(Friction Pendulum System)slider,concave plate and guide ditch.Moreover,through model experiments and 3D numerical simulation,it is verified that the proposed foundation can keep both the effects of the seismic isolation and the running safety of the train during an earthquake.展开更多
For the lifetime assessment of the running safety of a train in aggressive environments and earthquake-prone areas,the effects of corrosion on seismic performance must be considered.Research on the running safety of t...For the lifetime assessment of the running safety of a train in aggressive environments and earthquake-prone areas,the effects of corrosion on seismic performance must be considered.Research on the running safety of trains,including corrosion damage,is limited,despite the fact that seismic safety assessment of trains on high-speed railway bridges has been extensively examined.In this work,the running safety of a train was evaluated using a time-varying corroded bridge finite-element model established in OpenSees.Two pier types were considered,and three ground-motion types were selected for performing seismic performance evaluations.Subsequently,the seismic response of the corroded bridge-track structure under an earthquake was analyzed.The spectrum intensity was used as the structural response index for the running safety assessment of trains under earthquakes,and the long-term safety of trains on bridges with different pier heights and earthquake types,considering different corroding deterioration,was evaluated.The results indicate that under low-level earthquakes,piers are primarily in a linear elastic state and least influenced by corrosion;whereas under high-level earthquakes,the running safety of trains on a bridge significantly deteriorates after corrosion,particularly for high-pier bridges,mainly because the corroded piers are more likely to yield lower post-yield stiffness.The results of this study suggest that in the seismic safety assessment of trains on corroded bridges,timevarying seismic performance characteristics should be considered.展开更多
Standardization management is one of the key prerequisites to guarantee the effective and safe functioning of high-level biosafety laboratories.Since the outbreak of SARS,increasing numbers of biosafety laboratory lev...Standardization management is one of the key prerequisites to guarantee the effective and safe functioning of high-level biosafety laboratories.Since the outbreak of SARS,increasing numbers of biosafety laboratory levels have been established in China.Therefore,creating a specialized and standardized management system for biosafety laboratories has become necessary and is a core concern.This paper describes the current status of Chinese standards for biosafety management and analyzes its relation to other laboratory biosafety standard systems in developed countries.Based on the analysis on developing a biosafety laboratory,a laboratory biosafety standard system framework was developed,and a policy environment for building the system was suggested with the aim of promoting the promulgation of specific biosafety standards and securing the effective functioning of high-level biosafety laboratories.展开更多
To improve the fuel economy of rail vehicles,this study presents the feasibility of using power regenerating dampers(PRDs)in the primary suspension systems of railway vehicles and evaluates the potential and recoverab...To improve the fuel economy of rail vehicles,this study presents the feasibility of using power regenerating dampers(PRDs)in the primary suspension systems of railway vehicles and evaluates the potential and recoverable power that can be obtained.PRDs are configured as hydraulic electromagnetic-based railway primary vertical dampers and evaluated in parallel and series modes(with and without a viscous damper).Hydraulic configuration converts the linear behavior of the track into a unidirectional rotation of the generator,and the electromagnetic configuration provides a controllable damping force to the primary suspension system.In several case studies,generic railway vehicle primary suspension systems that are configured to include a PRD in the two configuration modes are modeled using computer simulations.The simulations are performed on measured tracks with typical irregularities for a generic UK passenger route.The performance of the modified vehicle is evaluated with respect to key performance indicators,including regenerated power,ride comfort,and running safety.Results indicate that PRDs can simultaneously replace conventional primary vertical dampers,regenerate power,and exhibit desirable dynamic performance.A peak power efficiency of 79.87%is theoretically obtained in series mode on a top-quality German Intercity Express track(Track 270)at a vehicle speed of 160 mile/h(~257 km/h).展开更多
基金the National Natural Science Foundation of China(Grant No.51678576)the National Key R&D Program of China(Grant No.2017YFB1201204)+1 种基金China Railway Corporation R&D Project(Grant No.2015G001-G)the Fundamental Research Funds for the Central Universities of Central South University(Grant No.2018zzts031).
文摘To explore the influence of spatially varying ground motion on the dynamic behavior of a train passing through a three-tower cable-stayed bridge,a 3D train–track–bridge coupled model is established for accurately simulating the train–bridge interaction under earthquake excitation,which is made up of a vehicle model built by multi-body dynamics,a track–bridge finite element model,and a 3D rolling wheel–rail contact model.A conditional simulation method,which takes into consideration the wave passage effect,incoherence effect,and site-response effect,is adopted to simulate the spatially varying ground motion under different soil conditions.The multi-time-step method previously proposed by the authors is also adopted to improve computational efficiency.The dynamic responses of the train running on a three-tower cablestayed bridge are calculated with differing earthquake excitations and train speeds.The results indicate that(1)the earthquake excitation significantly increases the responses of the train–bridge system,but at a design speed,all the running safety indices meet the code requirements;(2)the incoherence and site-response effects should also be considered in the seismic analysis for long-span bridges though there is no fixed pattern for determining their influences;(3)different train speeds that vary the vibration characteristics of the train–bridge system affect the vibration frequencies of the car body and bridge.
文摘Until now,seismic-isolation structures have not yet been applied in the railway field.The reason is that though a seismic-isolation structure can reduce the inertial force to the structure,the energy absorption causes big response displacement on the structure,which adversely effects the running safety of the trains supported by the structure.In this paper,a methodology for seismic running safety assessment is introduced,and a new type of seismic-isolation foundation is proposed,which can convert the seismic response displacement in the lateral direction of track to the longitudinal direction that has a less adverse effect on the running safety of the train.The isolation foundation is composed of FPS(Friction Pendulum System)slider,concave plate and guide ditch.Moreover,through model experiments and 3D numerical simulation,it is verified that the proposed foundation can keep both the effects of the seismic isolation and the running safety of the train during an earthquake.
基金supported by the National Natural Science Foundation of China (Grant Nos.52278546,52022113,and 52108433)the Fundamental Scientific Research Expenses of IME,China Earthquake Administration (Grant No.2020EEEVL0403)+3 种基金the Fundamental Research Funds for the Central Universities of Central South University (Grant No.2022ZZTS0625)Hunan Provincial Natural Science Foundation of China (Grant No.2021JJ40587)the Open Foundation of the National Engineering Research Center of High-Speed Railway Construction Technology (Grant No.HSR202004)the Technology Research and Development Program Project of China Railway Group Limited (Grant No.2021-Special-04-2)。
文摘For the lifetime assessment of the running safety of a train in aggressive environments and earthquake-prone areas,the effects of corrosion on seismic performance must be considered.Research on the running safety of trains,including corrosion damage,is limited,despite the fact that seismic safety assessment of trains on high-speed railway bridges has been extensively examined.In this work,the running safety of a train was evaluated using a time-varying corroded bridge finite-element model established in OpenSees.Two pier types were considered,and three ground-motion types were selected for performing seismic performance evaluations.Subsequently,the seismic response of the corroded bridge-track structure under an earthquake was analyzed.The spectrum intensity was used as the structural response index for the running safety assessment of trains under earthquakes,and the long-term safety of trains on bridges with different pier heights and earthquake types,considering different corroding deterioration,was evaluated.The results indicate that under low-level earthquakes,piers are primarily in a linear elastic state and least influenced by corrosion;whereas under high-level earthquakes,the running safety of trains on a bridge significantly deteriorates after corrosion,particularly for high-pier bridges,mainly because the corroded piers are more likely to yield lower post-yield stiffness.The results of this study suggest that in the seismic safety assessment of trains on corroded bridges,timevarying seismic performance characteristics should be considered.
基金This work was supported by the International Science and Technology Cooperation Project(2009DFB33040)“Twelfth Five-Year Plan”Special Project(2012ZX10004403)National Natural Science Foundation Project(71103178)and Excellent Talents Project of Chinese Academy of Sciences.
文摘Standardization management is one of the key prerequisites to guarantee the effective and safe functioning of high-level biosafety laboratories.Since the outbreak of SARS,increasing numbers of biosafety laboratory levels have been established in China.Therefore,creating a specialized and standardized management system for biosafety laboratories has become necessary and is a core concern.This paper describes the current status of Chinese standards for biosafety management and analyzes its relation to other laboratory biosafety standard systems in developed countries.Based on the analysis on developing a biosafety laboratory,a laboratory biosafety standard system framework was developed,and a policy environment for building the system was suggested with the aim of promoting the promulgation of specific biosafety standards and securing the effective functioning of high-level biosafety laboratories.
基金The authors are grateful for the financial support provided by the Sichuan Science and Technology Program(Grant No.2019JDRC0081).
文摘To improve the fuel economy of rail vehicles,this study presents the feasibility of using power regenerating dampers(PRDs)in the primary suspension systems of railway vehicles and evaluates the potential and recoverable power that can be obtained.PRDs are configured as hydraulic electromagnetic-based railway primary vertical dampers and evaluated in parallel and series modes(with and without a viscous damper).Hydraulic configuration converts the linear behavior of the track into a unidirectional rotation of the generator,and the electromagnetic configuration provides a controllable damping force to the primary suspension system.In several case studies,generic railway vehicle primary suspension systems that are configured to include a PRD in the two configuration modes are modeled using computer simulations.The simulations are performed on measured tracks with typical irregularities for a generic UK passenger route.The performance of the modified vehicle is evaluated with respect to key performance indicators,including regenerated power,ride comfort,and running safety.Results indicate that PRDs can simultaneously replace conventional primary vertical dampers,regenerate power,and exhibit desirable dynamic performance.A peak power efficiency of 79.87%is theoretically obtained in series mode on a top-quality German Intercity Express track(Track 270)at a vehicle speed of 160 mile/h(~257 km/h).
