In the realm of subway shield tunnel operations,the impact of tunnel settlement on the operational performance of subway vehicles is a crucial concern.This study introduces an advanced analytical model to investigate ...In the realm of subway shield tunnel operations,the impact of tunnel settlement on the operational performance of subway vehicles is a crucial concern.This study introduces an advanced analytical model to investigate rail geometric deformations caused by settlement within a vehicle-track-tunnel coupled system.The model integrates the geometric deformations of the track,attributed to settlement,as track irregularities.A novel“cyclic model”algorithm was employed to enhance computational efficiency without compromising on precision,a claim that was rigorously validated.The model’s capability extends to analyzing the time-history responses of vehicles traversing settlement-affected areas.The research primarily focuses on how settlement wavelength,amplitude,and vehicle speed influence operational performance.Key findings indicate that an increase in settlement wavelength can improve vehicle performance,whereas a rise in amplitude can degrade it.The study also establishes settlement thresholds,based on vehicle operation comfort and safety.These insights are pivotal for maintaining and enhancing the safety and efficiency of subway systems,providing a valuable framework for urban infrastructure management and long-term maintenance strategies in metropolitan transit systems.展开更多
Due to the wide railway network and different characteristics of many earthquake zones in China,considering the running safety performance of trains(RSPT)in the design of high-speed railway bridge structures is very n...Due to the wide railway network and different characteristics of many earthquake zones in China,considering the running safety performance of trains(RSPT)in the design of high-speed railway bridge structures is very necessary.In this study,in order to provide the seismic design and evaluation measure of the bridge structure based on the RSPT,a calculation model of RSPT on bridge under earthquake was established,and the track surface response measure when the derailment coefficient reaches the limit value was calculated by referring to 15 commonly used ground motion(GM)intensity measures.Based on the coefficient of variation of the limit value obtained from multiple GM samples,the optimal measures were selected.Finally,the limit value of bridge seismic response based on RSPT with different train speeds and structural periods was determined.展开更多
Background Quantifying the potential benefits of advanced footwear technology(AFT)track shoes(i.e.,“spikes”)in middle-distance events is challenging,because repeated maximal effort trials(as in sprinting)or aerobic ...Background Quantifying the potential benefits of advanced footwear technology(AFT)track shoes(i.e.,“spikes”)in middle-distance events is challenging,because repeated maximal effort trials(as in sprinting)or aerobic running economy trials(as in long-distance running)are not feasible.Methods We introduce a novel approach to assess the benefits of AFT spikes,consisting of a series of 200-m runs at self-perceived middle-distance race pace with 10 min recovery,and conduct 4 experiments to evaluate its validity,sensitivity,reproducibility,and utility.Results In Experiment 1,participants ran 1.2%slower in spikes with 200 g added mass vs.control spikes,which is exactly equal to the known effects of shoe mass on running performance.In Experiment 2,participants ran significantly faster in AFT prototype spikes vs.traditional spikes.In Experiment 3,we compared 2 other AFT prototype spikes against traditional spikes on 3 separate days.Group-level results were consistent across days,but our data indicates that at least 2 separate sessions are needed to evaluate individual responses.In Experiment 4,participants ran significantly faster in 2 AFT spike models vs.traditional spikes(2.1%and 1.6%).Speed was similar between a third AFT spike model and the traditional spikes.These speed results were mirrored by changes in step length as participants took significantly longer steps in the 2 faster AFT spike models(2.3%and 1.9%),while step length was similar between the other spikes.Conclusion Our novel,interval-based approach is a valid and reliable method for quantifying differences between spikes at middle-distance running intensity.展开更多
Background The ankle and foot together contribute to over half of the positive and negative work performed by the lower limbs during running.Yet,little is known about how foot kinetics change throughout a run.The amou...Background The ankle and foot together contribute to over half of the positive and negative work performed by the lower limbs during running.Yet,little is known about how foot kinetics change throughout a run.The amount of negative foot work may decrease as tibialis anterior(TA)electromyography(EMG)changes throughout longer-duration runs.Therefore,we examined ankle and foot work as well as TA EMG changes throughout a changing-speed run.Methods Fourteen heel-striking subjects ran on a treadmill for 58 min.We collected ground reaction forces,motion capture,and EMG.Subjects ran at 110%,100%,and 90%of their 10-km running speed and 2.8 m/s multiple times throughout the run.Foot work was evaluated using the distal rearfoot work,which provides a net estimate of all work contributors within the foot.Results Positive foot work increased and positive ankle work decreased throughout the run at all speeds.At the 110%10-km running speed,negative foot work decreased and TA EMG frequency shifted lower throughout the run.The increase in positive foot work may be attributed to increased foot joint work performed by intrinsic foot muscles.Changes in negative foot work and TA EMG frequency may indicate that the TA plays a role in negative foot work in the early stance of a run.Conclusion This study is the first to examine how the kinetic contributions of the foot change throughout a run.Future studies should investigate how increases in foot work affect running performance.展开更多
基金funded by the Scientific Research Startup Foundation of Fujian University of Technology (GY-Z21067 and GY-Z21026).
文摘In the realm of subway shield tunnel operations,the impact of tunnel settlement on the operational performance of subway vehicles is a crucial concern.This study introduces an advanced analytical model to investigate rail geometric deformations caused by settlement within a vehicle-track-tunnel coupled system.The model integrates the geometric deformations of the track,attributed to settlement,as track irregularities.A novel“cyclic model”algorithm was employed to enhance computational efficiency without compromising on precision,a claim that was rigorously validated.The model’s capability extends to analyzing the time-history responses of vehicles traversing settlement-affected areas.The research primarily focuses on how settlement wavelength,amplitude,and vehicle speed influence operational performance.Key findings indicate that an increase in settlement wavelength can improve vehicle performance,whereas a rise in amplitude can degrade it.The study also establishes settlement thresholds,based on vehicle operation comfort and safety.These insights are pivotal for maintaining and enhancing the safety and efficiency of subway systems,providing a valuable framework for urban infrastructure management and long-term maintenance strategies in metropolitan transit systems.
基金Projects(U1934207,51778630,11972379)supported by the National Natural Science Foundation of ChinaProject(2020zzts148)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(GJJ200657)supported the Research Project of Jiangxi Provincial Education Department,China。
文摘Due to the wide railway network and different characteristics of many earthquake zones in China,considering the running safety performance of trains(RSPT)in the design of high-speed railway bridge structures is very necessary.In this study,in order to provide the seismic design and evaluation measure of the bridge structure based on the RSPT,a calculation model of RSPT on bridge under earthquake was established,and the track surface response measure when the derailment coefficient reaches the limit value was calculated by referring to 15 commonly used ground motion(GM)intensity measures.Based on the coefficient of variation of the limit value obtained from multiple GM samples,the optimal measures were selected.Finally,the limit value of bridge seismic response based on RSPT with different train speeds and structural periods was determined.
基金partly supported by a research contract from PUMA SE with the University of Massachusetts,Amherst.
文摘Background Quantifying the potential benefits of advanced footwear technology(AFT)track shoes(i.e.,“spikes”)in middle-distance events is challenging,because repeated maximal effort trials(as in sprinting)or aerobic running economy trials(as in long-distance running)are not feasible.Methods We introduce a novel approach to assess the benefits of AFT spikes,consisting of a series of 200-m runs at self-perceived middle-distance race pace with 10 min recovery,and conduct 4 experiments to evaluate its validity,sensitivity,reproducibility,and utility.Results In Experiment 1,participants ran 1.2%slower in spikes with 200 g added mass vs.control spikes,which is exactly equal to the known effects of shoe mass on running performance.In Experiment 2,participants ran significantly faster in AFT prototype spikes vs.traditional spikes.In Experiment 3,we compared 2 other AFT prototype spikes against traditional spikes on 3 separate days.Group-level results were consistent across days,but our data indicates that at least 2 separate sessions are needed to evaluate individual responses.In Experiment 4,participants ran significantly faster in 2 AFT spike models vs.traditional spikes(2.1%and 1.6%).Speed was similar between a third AFT spike model and the traditional spikes.These speed results were mirrored by changes in step length as participants took significantly longer steps in the 2 faster AFT spike models(2.3%and 1.9%),while step length was similar between the other spikes.Conclusion Our novel,interval-based approach is a valid and reliable method for quantifying differences between spikes at middle-distance running intensity.
基金supported by Biomechanigg Sport & Heath Research which provided salary support to ECH,VvT and BMN
文摘Background The ankle and foot together contribute to over half of the positive and negative work performed by the lower limbs during running.Yet,little is known about how foot kinetics change throughout a run.The amount of negative foot work may decrease as tibialis anterior(TA)electromyography(EMG)changes throughout longer-duration runs.Therefore,we examined ankle and foot work as well as TA EMG changes throughout a changing-speed run.Methods Fourteen heel-striking subjects ran on a treadmill for 58 min.We collected ground reaction forces,motion capture,and EMG.Subjects ran at 110%,100%,and 90%of their 10-km running speed and 2.8 m/s multiple times throughout the run.Foot work was evaluated using the distal rearfoot work,which provides a net estimate of all work contributors within the foot.Results Positive foot work increased and positive ankle work decreased throughout the run at all speeds.At the 110%10-km running speed,negative foot work decreased and TA EMG frequency shifted lower throughout the run.The increase in positive foot work may be attributed to increased foot joint work performed by intrinsic foot muscles.Changes in negative foot work and TA EMG frequency may indicate that the TA plays a role in negative foot work in the early stance of a run.Conclusion This study is the first to examine how the kinetic contributions of the foot change throughout a run.Future studies should investigate how increases in foot work affect running performance.
