The rise of high-speed railway induces an increased probability of serious derailment accidents of operating high-speed trains during earthquakes.A two-and-half-dimensional finite element model(2.5D FEM)was developed ...The rise of high-speed railway induces an increased probability of serious derailment accidents of operating high-speed trains during earthquakes.A two-and-half-dimensional finite element model(2.5D FEM)was developed to investigate the ground vibration under combined seismic and high-speed train loads.Numerical examples were demonstrated and the proposed method was turned out to provide an effective means for estimating ground vibration caused by high-speed train load during earthquakes.The dynamic ground displacement caused by combined seismic and high-speed train loads increases with the increase of the train speed,and decreases with the increase of the stiffness of ground soil.Compared with the seismic load alone,the coupling effect of the seismic and high-speed train loads results in the low-frequency amplification of ground vibration.The moving train load dominants the medium–high frequency contents of the ground vibration induced by combined loads.It is observed that the coupling effects are significant as the train speed is higher than a critical speed.The critical train speed increases with the increase of the ground stiffness and the intensity of the input earthquake motion.展开更多
High speed train(HST)is an excellent platform to perform ultra-high spatial and temporal resolution observations of atmosphere using global navigation satellite systems(GNSS).However,we find that signal attenuation ca...High speed train(HST)is an excellent platform to perform ultra-high spatial and temporal resolution observations of atmosphere using global navigation satellite systems(GNSS).However,we find that signal attenuation caused by HST window glass is a major barrier for HST-based GNSS applications inside HST chambers.A field experiment is conducted to analyze the effect of HST glass on GNSS signal propagation.In the experiment,GNSS observations are collected and analyzed from a receiver covered with an HST window glass and one with an open-sky view.The size of the HST window glass is 670 mm×720 mm,with a thickness of 34 mm.The window glass is a double-glazing glass in which each layer has an actual thickness of 6 mm,and the two layers are separated by an air gap of 22 mm.The experiment results indicate that HST window glass can cause significant degradation to GNSS signals and even loss of tracking of the signal.Based on statistical results,HST window glass causes 39%,56%,49%,and 59%loss in GPS,GLONASS,Galileo,and BDS signals,respectively.Additionally,up to 20 dB-Hz of carrier-to-noise ratio(C/N0)degradation is also observed in the remaining observations.The significant signal attenuation and loss further lead to the decrease in the number of tracked satellites and occurrence of more cycle slips.The results of the study indicate that 44-230 cycle slips are detected for the HST glass-covered receiver whereas the receiver without glass does not exhibit more than 16 cycle slips.Additionally,the number of GNSS satellites tracked by the HST glass-covered receiver is reduced by 65%owing to the loss of signal.Furthermore,GNSS positioning performances from two receivers are also tested.With respect to GPS+GLONASS static precise point positioning(PPP),HST glass causes a degradation of 1.516 m and 1.159 m in the single-frequency and dual-frequency three-dimensional positioning accuracy,respectively.With respect to the GPS+GLONASS kinematic PPP,the accuracy degradations for single-frequency and dual-frequency kinematic PPP are 2.670 m and 4.821 m,respectively.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos:41372271 and 51978510).
文摘The rise of high-speed railway induces an increased probability of serious derailment accidents of operating high-speed trains during earthquakes.A two-and-half-dimensional finite element model(2.5D FEM)was developed to investigate the ground vibration under combined seismic and high-speed train loads.Numerical examples were demonstrated and the proposed method was turned out to provide an effective means for estimating ground vibration caused by high-speed train load during earthquakes.The dynamic ground displacement caused by combined seismic and high-speed train loads increases with the increase of the train speed,and decreases with the increase of the stiffness of ground soil.Compared with the seismic load alone,the coupling effect of the seismic and high-speed train loads results in the low-frequency amplification of ground vibration.The moving train load dominants the medium–high frequency contents of the ground vibration induced by combined loads.It is observed that the coupling effects are significant as the train speed is higher than a critical speed.The critical train speed increases with the increase of the ground stiffness and the intensity of the input earthquake motion.
基金The authors acknowledge grant supports from the National Natural Science Foundation of China(NSFC,No.41730109)the Hong Kong Research Grants Council(RGC)General Research Fund(GRF)(B-Q52W RGC/Gov No.PolyU 152149/16E,B-Q61L RGC/Gov No.PolyU 152222/17E)+1 种基金the support from the Emerging Frontier Area(EFA)Scheme of Research Institute for Sustainable Urban Development(RISUD)of the Hong Kong Polytechnic University(No.1-BBWJ)The authors also appreciate funding support by the Innovation and Technology Commission of Hong Kong SAR Government to the Hong Kong Branch of National Rail Transit Electrification and Automation Engineering Technology Research Center(Project No.1-BBYH).
文摘High speed train(HST)is an excellent platform to perform ultra-high spatial and temporal resolution observations of atmosphere using global navigation satellite systems(GNSS).However,we find that signal attenuation caused by HST window glass is a major barrier for HST-based GNSS applications inside HST chambers.A field experiment is conducted to analyze the effect of HST glass on GNSS signal propagation.In the experiment,GNSS observations are collected and analyzed from a receiver covered with an HST window glass and one with an open-sky view.The size of the HST window glass is 670 mm×720 mm,with a thickness of 34 mm.The window glass is a double-glazing glass in which each layer has an actual thickness of 6 mm,and the two layers are separated by an air gap of 22 mm.The experiment results indicate that HST window glass can cause significant degradation to GNSS signals and even loss of tracking of the signal.Based on statistical results,HST window glass causes 39%,56%,49%,and 59%loss in GPS,GLONASS,Galileo,and BDS signals,respectively.Additionally,up to 20 dB-Hz of carrier-to-noise ratio(C/N0)degradation is also observed in the remaining observations.The significant signal attenuation and loss further lead to the decrease in the number of tracked satellites and occurrence of more cycle slips.The results of the study indicate that 44-230 cycle slips are detected for the HST glass-covered receiver whereas the receiver without glass does not exhibit more than 16 cycle slips.Additionally,the number of GNSS satellites tracked by the HST glass-covered receiver is reduced by 65%owing to the loss of signal.Furthermore,GNSS positioning performances from two receivers are also tested.With respect to GPS+GLONASS static precise point positioning(PPP),HST glass causes a degradation of 1.516 m and 1.159 m in the single-frequency and dual-frequency three-dimensional positioning accuracy,respectively.With respect to the GPS+GLONASS kinematic PPP,the accuracy degradations for single-frequency and dual-frequency kinematic PPP are 2.670 m and 4.821 m,respectively.
