High stress concentrations around underground excavations can result in significant damage to deep hard-rock mines.These conditions can be the result of stopping activities,blasting,seismicity,or other mining activiti...High stress concentrations around underground excavations can result in significant damage to deep hard-rock mines.These conditions can be the result of stopping activities,blasting,seismicity,or other mining activities.Large anisotropic deformation and excavation closure,especially under high-stress conditions,are expected if the excavation is located in a foliated or thin-bedded rock mass.In this research,the behaviour of excavations under deep and high-stress conditions was investigated and categorised.The main purpose was to enhance the existing knowledge of managing large anisotropic deformations and to help prepare suitable measures for handling such contingencies.Numerical simulations using the distinct element method(DEM)and model calibration were performed to reproduce the anisotropic deformation of an ore drive based on the collected field data.Then,the roles of key factors(i.e.stress ratio,slenderness ratio,foliation orientation,and foliation considering excavation orientation)on the large deformation and damage depth of the excavations were investigated.This study found that increasing both the stress ratio and slenderness ratio induced linear increases in wall closure and damage depth,whereas increasing the foliation angle first increases the deformation and damage depth and then reduces them both before and after 45.The wall closure and damage thickness decreased with increasing orientation intercept.The deformation and damage levels were classified based on these factors.展开更多
Tunnel-type anchorages(TTAs)installed in human gathering areas are characterized by a shallow burial depth,and in many instances,they utilize soft rock as the bearing stratum.However,the stability control measures and...Tunnel-type anchorages(TTAs)installed in human gathering areas are characterized by a shallow burial depth,and in many instances,they utilize soft rock as the bearing stratum.However,the stability control measures and the principle of shallow TTAs in soft rock have not been fully studied.Hence,a structure suitable for improving the stability of shallow TTAs in soft rock strata,named the anti-pull tie(APT),was added to the floor of the back face.Physical tests and numerical models were established to study the influence of the APT on the load transfer of TTAs,the mechanical response of the surrounding rock,the stress distribution of the interface,and the failure model.The mechanical characteristics of APTs were also studied.The results show that the ultimate bearing capacity of TTAs with an APT is increased by approximately 11.8%,as compared to the TTAs without an APT.Also,the bearing capacity of TTAs increases approximately linearly with increasing height,width,length,and quantity of APTs,and decreases approximately linearly with increasing distance from the back face and slope angle of the tie slope.The normal squeezing between the tie slope and the surrounding rock increases the shear resistance of the interface and expands the range of the surrounding rock participating in bearing sharing.Both tension and compression zones exist in the APT during loading.The tension zone extends from the tie toe to the tie bottom along the tie slope.The range of the tie body tension zone constantly expands to the deep part of the APT with an increasing load.The peak tensile stress value is located at the tie toe.The distribution of compressive stress in the tie body is the largest at the tie top,followed by the tie slope,and then the tie bottom.展开更多
Seismic resistance systems for small and mid-span girder bridges often lacks hierarchically repeatable earthquake resistance, leading to challenging and time-consuming post-earthquake repairs. This research introduces...Seismic resistance systems for small and mid-span girder bridges often lacks hierarchically repeatable earthquake resistance, leading to challenging and time-consuming post-earthquake repairs. This research introduces a novel quasi-floating seismic resistance system (QFSRS) with hierarchically sacrificial components to enable multiple instances of earthquake resistance and swift post-earthquake restoration. Finite element modeling, a numerical probabilistic approach, and earthquake-simulating shake-table tests identified highly sensitive parameters from the QFSRS to establish theoretical equations describing the mechanical model and working mechanism of the system. The results indicate that the working mechanism of the QFSRS under seismic conditions aligns with the theoretical design, featuring four hierarchically sacrificial seismic stages. Specifically, under moderate (0.3g) or higher seismic conditions, QFSRS reduced relative displacement between piers and beams by 55.15% on average. The strain at pier bases increased 6.17% across all seismic scenarios, significantly enhancing bridge seismic performance. The QFSRS provides resilient and restorable earthquake resistance for girder bridges.展开更多
In order to make further study on the mechanical property of CRTSIII type slab non-ballast track structures,which was self-designed in China,based on the method of the multiscale finite element model(FEM),the traditio...In order to make further study on the mechanical property of CRTSIII type slab non-ballast track structures,which was self-designed in China,based on the method of the multiscale finite element model(FEM),the traditional FEM of slab non-ballast track structures was improved.The multiscale FEM of CRTSII type slab nonballast track structures was established based on the general finite element program ABAQUs.Then the comparative calculation was made between various FEMs,showing that the high solution precision,fast modelling speed and high solution efficiency could be obtained.Therefore,the multiscale FEM was suitable for the parametric study on mechanical behaviour of CRTSII type slab non-ballast track structures,and then the key influence factor and constructions could be optimized.展开更多
To analyze the impact effect induced by vehicle-bridge coupling vibration during traffic congesting, hundreds and thousands of congestion scenarios consisting of various vehicle platoons were collected and used to dev...To analyze the impact effect induced by vehicle-bridge coupling vibration during traffic congesting, hundreds and thousands of congestion scenarios consisting of various vehicle platoons were collected and used to develop vehicle models as well as traffic congestion load models. Furthermore, the idling vehicle-bridge coupling model was established by the finite element method and the congestion models were applied to calculate dynamic impact factors. Compared with the value specified in Chinese codes, the calculated values were 1.15-2.67 times as large as the latter, which indicates the impact factors caused by idling vehicle-bridge coupling under congestion situations were much larger than those in normal traffic conditions. As a result, a calibration factor of 1.7 was recommended for bridge design or evaluation when considering vehicle-bridge coupling vibration under heavy traffic congestion. The proposed analytical model, analysis method, and results could also be beneficial references to further investigation in this field.展开更多
Failure tests were conducted on two concrete-filled steel tubular(CFST)truss arch bridges with a span of approximately 12 m to investigate the influence of initial geometric defects on the in-plane bearing capacity of...Failure tests were conducted on two concrete-filled steel tubular(CFST)truss arch bridges with a span of approximately 12 m to investigate the influence of initial geometric defects on the in-plane bearing capacity of CFST truss arch bridges.The effects of antisymmetric defect on the ultimate bearing capacity,failure mode,structural response,and steel–concrete confinement effect of CFST truss arch bridges under quarter-point loading were analyzed.On this basis,numerical simulations were conducted to investigate the in-plane bearing capacity of CFST truss arch bridges further under different scenarios.The initial defect formof the archwas obtained by using theoretical deduction,and the theoretical basis for the weakening of the ultimate bearing capacity of the arch bridge caused by geometric defects was clarified.Results indicate that the antisymmetric defect does not change the four-hinge failure mode of the model arch under quarter-point loading but increases the local cracking area and crack density of the concrete inside the pipe.The sine geometric defect with an amplitude of L/250 resulted in a 44.4%decrease in the yield load of the single hinge of the model arch,a 10.5%decrease in the failure load of the four hinges,and a 40.9%increase in themaximum vertical deformation during failure.At the initial stage of loading,the steel pipe and the concrete inside the pipe were subjected to relatively independent forces.After reaching 67%of the ultimate load,the catenary arch ribs began to produce a steel pipe concrete constraint effect.The initial geometric defects resulted in a decrease in the load when the constraint effect occurred.The antisymmetric defects with the same amplitude have a greater impact on the in-plane bearing capacity of the CFST arch bridge than the initial geometric defects with symmetry.The linear deviation at L/4 caused by constructionmust be controlled to be less than L/600 to ensure that the internal bearing capacity of the CFST arch bridge reaches 95%of the design bearing capacity.The structural deformation caused by geometric initial defects increases linearly with the increase in defect amplitude.The bearing capacity is weakened because the structural deflection and bending moment are amplified by initial defects.展开更多
The goaf formed by coal seam mining would dramatically reduce the strength and stiffness of the ground in and around the goaf,which is not conducive to tunnel excavation near the mined-out area.By establishing the Fin...The goaf formed by coal seam mining would dramatically reduce the strength and stiffness of the ground in and around the goaf,which is not conducive to tunnel excavation near the mined-out area.By establishing the Finite differential method and Discrete element method coupling numerical analysis method and conducting similar model test,the influence of dip angle,thickness and distance of coal seam goaf on the stability of unsupported tunnel excavation is studied.The results show that when the tunnel under the goaf is exca-vated,the circumferential stress increment increases first and then decreases along the radial direction of the tunnel,the radial stress increment gradually decreases to zero along the radial direction of the tunnel,the displacement is approximately distributed in a trough shape,and the maximum displacement is at the top of the tunnel.The area of the stress loosening zone(SLZ)is negatively correlated with the dip angle and the distance of the goaf,and positively correlated with the thickness.The SLZ near the goaf is larger,and the peak value of the asymmetry is about 1.35.When the thickness of the mined-out area is 1.8–2.1 m,the SLZ and displacement around the tunnel increase sharply and then become stable.When the dip angle of the mined-out area is greater than 30°or the distance exceeds 1.3 times tunnel diameter(D),the asymmetry converges.The research results of this paper are of great importance to the design and construction of tunnel support and the formulation of excavation schemes.展开更多
Bridge widening involves phased construction of adjacent structures to maintain uninterrupted traffic flow.This process exposes freshly placed longitudinal joints between staged deck constructions to vehicle-induced v...Bridge widening involves phased construction of adjacent structures to maintain uninterrupted traffic flow.This process exposes freshly placed longitudinal joints between staged deck constructions to vehicle-induced vibrations,potentially compromising their mechanical integrity.This study investigates the flexural behavior of ultra-highperformance concrete(UHPC)longitudinal joints under such vibrations through model tests.To simulate actual site conditions,we developed a novel vibration test setup that replicates the dynamic environment experienced by these joints during construction.Micro-and meso-scale tests were conducted to examine the flexural behavior of longitudinal joints following vibration exposure.Results revealed that vibration amplitude significantly influences fiber orientation and flexural strength of ultra-high-performance concrete(UHPC)wet joint specimens.Low-amplitude vibrations(3 Hz at 1 mm and 3 mm)enhanced fiber orientation,increasing flexural strength by 11.5%to 19.8%and ultimate load capacity by 17%compared to non-vibrated specimens.Conversely,high-amplitude vibrations(3 Hz at 5 mm)adversely affected fiber orientation,decreasing flexural strength by 23.9%and ultimate load capacity by 19%relative to non-vibrated specimens.展开更多
In this study, by taking the accretions into account, the observed shadows and rings cast by the Brane-World black hole were numerically investigated when the observer was located at the cosmological horizon. The resu...In this study, by taking the accretions into account, the observed shadows and rings cast by the Brane-World black hole were numerically investigated when the observer was located at the cosmological horizon. The results showed that the radius rpof the photon sphere increased with the cosmological parameter α and dark matter parameter β, while the impact parameter bpdecreased with α and increased with β. For thin disk accretion, the total observed intensity is mainly composed of direct emission.Simultaneously, the lensing ring and photon ring have only small and negligible contributions, respectively. We also found that shadows and rings exhibit different and exciting features when the disk is located at different positions. For static and infalling spherical accretions, it is evident that the size of shadows is always the same for both accretions. This implies that shadows are only related to space-time geometry in this case. The luminosity of the shadow and photon sphere is closely associated with the Doppler effect and the emissivity per unit volume j(νe). In addition, the influence of dark matter and cosmological constant on the observed intensity of shadows and rings is carefully emphasized throughout this paper. Finally, we obtained the burring images of shadows and rings using the nominal resolution of the event horizon telescope. We also studied the upper limits of the X-clod dark matter parameter β using the data of the shadow of M87.展开更多
As a charged fermion drops into a BTZ black hole, the laws of thermodynamics and the weak cosmic censorship conjecture are investigated in both the normal and extended phase space, where the cosmological parameter and...As a charged fermion drops into a BTZ black hole, the laws of thermodynamics and the weak cosmic censorship conjecture are investigated in both the normal and extended phase space, where the cosmological parameter and renormalization length are regarded as extensive quantities. In the normal phase space, the first and second law of thermodynamics, and the weak cosmic censorship are found to be valid. In the extended phase space, although the first law and weak cosmic censorship conjecture remain valid, the second law is dependent on the variation of the renormalization energy dK. Moreover, in the extended phase space, the configurations of extremal and near-extremal black holes are not changed, as they are stable, while in the normal phase space, the extremal and near-extremal black holes evolve into non-extremal black holes.展开更多
We study the Einstein images of a charged Rastall AdS black hole(BH)within the fabric of AdS/CFT correspondence.Considering the holographic setup,we analyze the amplitude of the total response function for various val...We study the Einstein images of a charged Rastall AdS black hole(BH)within the fabric of AdS/CFT correspondence.Considering the holographic setup,we analyze the amplitude of the total response function for various values of model parameters.With an increase in parameterλand temperature T,the amplitude of the response function decreases,while it increases with an increase in electric charge e and chemical potentialμ.The influence of frequencyωalso plays an important role in the bulk field,as it is found that decreasingωleads to an increase in the periods of the waves,which means that the amplitude of the response function also depends on the wave source.The relation between T and the inverse of the horizon for various values of parameterλis interpreted under fixed values of other involved parameters.These,in turn,affect the behavior of the response function and the Einstein ring,which may be used to differentiate the present study from previous ones.We construct the holographic images of the BH in bulk via a special optical system.The results show that the Einstein ring always appears with concentric stripes at the position of the north pole,and this ring transforms into a luminosity-deformed ring or bright light spot when the distant observer lies away from the north pole.Finally,we discuss the influence of the associated parameters on the Einstein ring radius,which is consistent with wave optics.展开更多
Using AdS/CFT correspondence,we analyze the holographic Einstein images via the response function of the complex scalar field as a probe wave on an AdS Schwarzschild scalar-tensor-vector gravity(STVG)black hole(BH).We...Using AdS/CFT correspondence,we analyze the holographic Einstein images via the response function of the complex scalar field as a probe wave on an AdS Schwarzschild scalar-tensor-vector gravity(STVG)black hole(BH).We find that the amplitude of the response function||decreases with increasing values of coupling parameter a and increases with decreasing temperature T.The frequencyωof the wave source also plays a significant role in wave periods;as we increase the values ofω,the periods of waves decrease,indicating that the total response function closely depends on the wave source.Further,we investigate the optical appearance of the holographic images of the BH in bulk.We found that the holographic ring always appears with surrounding concentric stripes when the observer is located at the north pole,and an extremely bright ring appears when the observer is at the position of the photon sphere of the BH.This ring changes into a luminosity-deformed ring or a bright light spot as the observational angle changes.The corresponding brightness profiles show that the luminosity of the ring decreases and the shadow radius increases with increasing values of a.The relation between temperature T and the inverse of the horizonh_e is discussed;T is small at the beginning of the horizon he and then increases as the horizon radius increases.This effect can be used to distinguish the STVG BH solution from other BH solutions.Moreover,these significant features are also reflected in the Einstein ring and corresponding brightness profiles.In addition,we compare the results obtained by wave optics and geometric optics,which align well,implying that the holographic scheme adopted in this study is valid.展开更多
This study undertook verification of the applicability and accuracy of wind data measured using a WindCube V2 Doppler Wind Lidar(DWL).The data were collected as part of a field experiment in Zhoushan,Zhejiang Province...This study undertook verification of the applicability and accuracy of wind data measured using a WindCube V2 Doppler Wind Lidar(DWL).The data were collected as part of a field experiment in Zhoushan,Zhejiang Province(China),which was conducted by Shanghai Typhoon Institute of China Meteorological Administration during the passage of Super Typhoon Lekima(2019).The DWL measurements were compared with balloon-borne GPS radiosonde(GPS sonde)data,which were acquired using balloons launched from the DWL location.Results showed that wind speed measured by GPS sonde at heights of<100 m is unreliable owing to the drift effect.Optimal agreement(at heights of>100 m)was found for DWL-measured wind speed time-averaged during the ascent of the GPS sonde from the ground surface to the height of 270 m(correlation coefficient:0.82;root mean square(RMS):2.19 m·h^(-1)).Analysis revealed that precipitation intensity(PI)exerts considerable influence on both the carrier-to-noise ratio and the rate of missing DWL data;however,PI has minimal effect on the wind speed bias of DWL measurements.Specifically,the rate of missing DWL data increased with increasing measurement height and PI.For PI classed as heavy rain or less(PI<12 mm·h^(-1)),the DWL data below 300 m were considered valid,whereas for PI classed as a severe rainstorm(PI>90 m·h^(-1)),only data below 100 m were valid.Up to the height of 300 m,the RMS of the DWL measurements was nearly half that of wind profile radar(WPR)estimates(4.32 m·s^(-1)),indicating that DWL wind data are more accurate than WPR data under typhoon conditions.展开更多
Considering the cosmological constant as the pressure,this study addresses the laws of thermodynamics and weak cosmic censorship conjecture in the Reissner-Nordstrom-AdS black hole surrounded by quintessence dark ener...Considering the cosmological constant as the pressure,this study addresses the laws of thermodynamics and weak cosmic censorship conjecture in the Reissner-Nordstrom-AdS black hole surrounded by quintessence dark energy under charged Particle absorption.The first law of thermodynamics i5 found to be valid as a Particle is absorbed by the black hole.The second law,however,is violated for the extremal and near-extremal black holes,because the entropy of these black hole decrease.Moreover,we find that the extremal black hole does not change its configuration in the extended phase space,implying that the weak cosmic censorship conjecture is valid.Remarkably,the near-extremal black hole can be overcharged beyond the extremal condition under charged particle absorption.Hence,the cosmic censorship conjecture could be violated for the near-extremal black hole in the extended phase space.For comparison,we also discuss the first law,second law,and the weak cosmic censorship conjecture in normal phase space,and find that all of them are valid in this case.展开更多
In this study,we examine the laws of thermodynamics and the weak cosmic censorship conjecture in the normal and extended phase spaces of Born-Infeld-anti-de Sitter black holes by considering a charged particle absorpt...In this study,we examine the laws of thermodynamics and the weak cosmic censorship conjecture in the normal and extended phase spaces of Born-Infeld-anti-de Sitter black holes by considering a charged particle absorption.In the normal phase space,the first and second laws of thermodynamics as well as the weak cosmic censorship are still valid.However,in the extended phase space,the second law of thermodynamics is violated for double-horizon black holes and part of single-horizon black holes.The first law of thermodynamics and the weak cosmic censorship conjecture are still valid for all types of black holes.In addition,we found that the shift of the metric function,which determines the locations of the horizons,takes the same form at the minimum point in both the normal and extended phase spaces,indicating that the weak cosmic censorship conjecture is independent of the thermodynamic phase space.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.5183900341801053),the Science and Technology Research Project of Chongqing Education Commission(KJQN201800724)+2 种基金the Natural Science Foundation of Chongqing(No.CSTC2019JCYJ-MSXMX0835),the Fund(Nos.SKLFSE201903 and SKLBT-19-003)the China Postdoctoral Science Foundation(No.2020M683710XB)the Key Scientific Research Project of Inner Mongolia Universities(No.NJZZ20300).
文摘High stress concentrations around underground excavations can result in significant damage to deep hard-rock mines.These conditions can be the result of stopping activities,blasting,seismicity,or other mining activities.Large anisotropic deformation and excavation closure,especially under high-stress conditions,are expected if the excavation is located in a foliated or thin-bedded rock mass.In this research,the behaviour of excavations under deep and high-stress conditions was investigated and categorised.The main purpose was to enhance the existing knowledge of managing large anisotropic deformations and to help prepare suitable measures for handling such contingencies.Numerical simulations using the distinct element method(DEM)and model calibration were performed to reproduce the anisotropic deformation of an ore drive based on the collected field data.Then,the roles of key factors(i.e.stress ratio,slenderness ratio,foliation orientation,and foliation considering excavation orientation)on the large deformation and damage depth of the excavations were investigated.This study found that increasing both the stress ratio and slenderness ratio induced linear increases in wall closure and damage depth,whereas increasing the foliation angle first increases the deformation and damage depth and then reduces them both before and after 45.The wall closure and damage thickness decreased with increasing orientation intercept.The deformation and damage levels were classified based on these factors.
基金the financial support provided by the National Natural Science Foundation of China(Grant No.42302332)the Special Funding of Chongqing Postdoctoral Research Project(Grant No.2022CQBSHTB2061,2022CQBSHTB1010)+3 种基金the Chongqing Postdoctoral Science Foundation(Grant No.CSTB2022NSCQ-BHX0738,CSTB2023NSCQBHX0223)the China Postdoctoral Science Foundation(Grant No.2023M730432)the Natural Science Foundation of Chongqing(Grant No.CSTB2023NSCQMSX0913,cstc2021jcyj-msxm X0869)the Postdoctoral Science Foundation of Chongqing Jiaotong University(Grant No.F1220105,22JDKJC-A008)。
文摘Tunnel-type anchorages(TTAs)installed in human gathering areas are characterized by a shallow burial depth,and in many instances,they utilize soft rock as the bearing stratum.However,the stability control measures and the principle of shallow TTAs in soft rock have not been fully studied.Hence,a structure suitable for improving the stability of shallow TTAs in soft rock strata,named the anti-pull tie(APT),was added to the floor of the back face.Physical tests and numerical models were established to study the influence of the APT on the load transfer of TTAs,the mechanical response of the surrounding rock,the stress distribution of the interface,and the failure model.The mechanical characteristics of APTs were also studied.The results show that the ultimate bearing capacity of TTAs with an APT is increased by approximately 11.8%,as compared to the TTAs without an APT.Also,the bearing capacity of TTAs increases approximately linearly with increasing height,width,length,and quantity of APTs,and decreases approximately linearly with increasing distance from the back face and slope angle of the tie slope.The normal squeezing between the tie slope and the surrounding rock increases the shear resistance of the interface and expands the range of the surrounding rock participating in bearing sharing.Both tension and compression zones exist in the APT during loading.The tension zone extends from the tie toe to the tie bottom along the tie slope.The range of the tie body tension zone constantly expands to the deep part of the APT with an increasing load.The peak tensile stress value is located at the tie toe.The distribution of compressive stress in the tie body is the largest at the tie top,followed by the tie slope,and then the tie bottom.
基金supported by the General Program of China Postdoctoral Science Foundation(2023MD734111)Chongqing Natural Science Foundation General Project(CSTB2023NSCO-MSX0853,CSTB2023NSCO-MSX0433)Scientific and Technological Research Program of Chongqing Municipal Education Commission(KJZD-K202301205).
文摘Seismic resistance systems for small and mid-span girder bridges often lacks hierarchically repeatable earthquake resistance, leading to challenging and time-consuming post-earthquake repairs. This research introduces a novel quasi-floating seismic resistance system (QFSRS) with hierarchically sacrificial components to enable multiple instances of earthquake resistance and swift post-earthquake restoration. Finite element modeling, a numerical probabilistic approach, and earthquake-simulating shake-table tests identified highly sensitive parameters from the QFSRS to establish theoretical equations describing the mechanical model and working mechanism of the system. The results indicate that the working mechanism of the QFSRS under seismic conditions aligns with the theoretical design, featuring four hierarchically sacrificial seismic stages. Specifically, under moderate (0.3g) or higher seismic conditions, QFSRS reduced relative displacement between piers and beams by 55.15% on average. The strain at pier bases increased 6.17% across all seismic scenarios, significantly enhancing bridge seismic performance. The QFSRS provides resilient and restorable earthquake resistance for girder bridges.
基金supported by“111”Project(B18062)Fundamental Research Funds for the Central Universities(2019CDQYTM028).
文摘In order to make further study on the mechanical property of CRTSIII type slab non-ballast track structures,which was self-designed in China,based on the method of the multiscale finite element model(FEM),the traditional FEM of slab non-ballast track structures was improved.The multiscale FEM of CRTSII type slab nonballast track structures was established based on the general finite element program ABAQUs.Then the comparative calculation was made between various FEMs,showing that the high solution precision,fast modelling speed and high solution efficiency could be obtained.Therefore,the multiscale FEM was suitable for the parametric study on mechanical behaviour of CRTSII type slab non-ballast track structures,and then the key influence factor and constructions could be optimized.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51708069)the Natural Science Foundation of Chongqing(Grant No.cstcstc2018jcyjA2535)。
文摘To analyze the impact effect induced by vehicle-bridge coupling vibration during traffic congesting, hundreds and thousands of congestion scenarios consisting of various vehicle platoons were collected and used to develop vehicle models as well as traffic congestion load models. Furthermore, the idling vehicle-bridge coupling model was established by the finite element method and the congestion models were applied to calculate dynamic impact factors. Compared with the value specified in Chinese codes, the calculated values were 1.15-2.67 times as large as the latter, which indicates the impact factors caused by idling vehicle-bridge coupling under congestion situations were much larger than those in normal traffic conditions. As a result, a calibration factor of 1.7 was recommended for bridge design or evaluation when considering vehicle-bridge coupling vibration under heavy traffic congestion. The proposed analytical model, analysis method, and results could also be beneficial references to further investigation in this field.
基金National Natural Science Foundation of China(Grant No.52408314)Science and Technology Project of Sichuan Provincial TransportationDepartment(GrantNo.2023-ZL-03)Science and Technology Project of Guizhou Provincial Transportation Department(Grant No.2024-122-018).
文摘Failure tests were conducted on two concrete-filled steel tubular(CFST)truss arch bridges with a span of approximately 12 m to investigate the influence of initial geometric defects on the in-plane bearing capacity of CFST truss arch bridges.The effects of antisymmetric defect on the ultimate bearing capacity,failure mode,structural response,and steel–concrete confinement effect of CFST truss arch bridges under quarter-point loading were analyzed.On this basis,numerical simulations were conducted to investigate the in-plane bearing capacity of CFST truss arch bridges further under different scenarios.The initial defect formof the archwas obtained by using theoretical deduction,and the theoretical basis for the weakening of the ultimate bearing capacity of the arch bridge caused by geometric defects was clarified.Results indicate that the antisymmetric defect does not change the four-hinge failure mode of the model arch under quarter-point loading but increases the local cracking area and crack density of the concrete inside the pipe.The sine geometric defect with an amplitude of L/250 resulted in a 44.4%decrease in the yield load of the single hinge of the model arch,a 10.5%decrease in the failure load of the four hinges,and a 40.9%increase in themaximum vertical deformation during failure.At the initial stage of loading,the steel pipe and the concrete inside the pipe were subjected to relatively independent forces.After reaching 67%of the ultimate load,the catenary arch ribs began to produce a steel pipe concrete constraint effect.The initial geometric defects resulted in a decrease in the load when the constraint effect occurred.The antisymmetric defects with the same amplitude have a greater impact on the in-plane bearing capacity of the CFST arch bridge than the initial geometric defects with symmetry.The linear deviation at L/4 caused by constructionmust be controlled to be less than L/600 to ensure that the internal bearing capacity of the CFST arch bridge reaches 95%of the design bearing capacity.The structural deformation caused by geometric initial defects increases linearly with the increase in defect amplitude.The bearing capacity is weakened because the structural deflection and bending moment are amplified by initial defects.
基金supported by the National Natural Science Fund of China(Grant No.52078090)the general program of Chongqing Natural Science Foundation(Grant No.cstc2020jcyj-msxmX0679)the Fund of State Key Laboratory of Mountain Bridge and Tunnel Engineering(Grant Nos.SKLBT-19-006,SKLBT-YF2106).
文摘The goaf formed by coal seam mining would dramatically reduce the strength and stiffness of the ground in and around the goaf,which is not conducive to tunnel excavation near the mined-out area.By establishing the Finite differential method and Discrete element method coupling numerical analysis method and conducting similar model test,the influence of dip angle,thickness and distance of coal seam goaf on the stability of unsupported tunnel excavation is studied.The results show that when the tunnel under the goaf is exca-vated,the circumferential stress increment increases first and then decreases along the radial direction of the tunnel,the radial stress increment gradually decreases to zero along the radial direction of the tunnel,the displacement is approximately distributed in a trough shape,and the maximum displacement is at the top of the tunnel.The area of the stress loosening zone(SLZ)is negatively correlated with the dip angle and the distance of the goaf,and positively correlated with the thickness.The SLZ near the goaf is larger,and the peak value of the asymmetry is about 1.35.When the thickness of the mined-out area is 1.8–2.1 m,the SLZ and displacement around the tunnel increase sharply and then become stable.When the dip angle of the mined-out area is greater than 30°or the distance exceeds 1.3 times tunnel diameter(D),the asymmetry converges.The research results of this paper are of great importance to the design and construction of tunnel support and the formulation of excavation schemes.
基金support from the Natural Science Foundation of China(Grant No.52278147,52208302,52278293,U20A20314)the Science and Technology Research Program of Chongqing Municipal Education Commission(KJZD-M202300706)+4 种基金the Natural Science Foundation of Chongqing,China(CSTB2023NSCQ-MSX0019)the Chongqing Science and Technology Project(CSTB2022TIAD-KPX0205)the China Railway Major Project(2022-ZD-11)the Guangxi key research and development plan project(Grant No.GuikeAB22036007)the Research and Innovation Program for Graduate Students in Chongqing(Grant Nos.CYB23245).
文摘Bridge widening involves phased construction of adjacent structures to maintain uninterrupted traffic flow.This process exposes freshly placed longitudinal joints between staged deck constructions to vehicle-induced vibrations,potentially compromising their mechanical integrity.This study investigates the flexural behavior of ultra-highperformance concrete(UHPC)longitudinal joints under such vibrations through model tests.To simulate actual site conditions,we developed a novel vibration test setup that replicates the dynamic environment experienced by these joints during construction.Micro-and meso-scale tests were conducted to examine the flexural behavior of longitudinal joints following vibration exposure.Results revealed that vibration amplitude significantly influences fiber orientation and flexural strength of ultra-high-performance concrete(UHPC)wet joint specimens.Low-amplitude vibrations(3 Hz at 1 mm and 3 mm)enhanced fiber orientation,increasing flexural strength by 11.5%to 19.8%and ultimate load capacity by 17%compared to non-vibrated specimens.Conversely,high-amplitude vibrations(3 Hz at 5 mm)adversely affected fiber orientation,decreasing flexural strength by 23.9%and ultimate load capacity by 19%relative to non-vibrated specimens.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11875095, and 11903025)Starting Fund of China West Normal University (Grant No. 18Q062)+1 种基金Sichuan Youth Science and Technology Innovation Research Team (Grant No. 21CXTD0038)Central Government Funds of Guiding Local Scientific and Technological Development for Sichuan Province (Grant No. 2021ZYD0032)。
文摘In this study, by taking the accretions into account, the observed shadows and rings cast by the Brane-World black hole were numerically investigated when the observer was located at the cosmological horizon. The results showed that the radius rpof the photon sphere increased with the cosmological parameter α and dark matter parameter β, while the impact parameter bpdecreased with α and increased with β. For thin disk accretion, the total observed intensity is mainly composed of direct emission.Simultaneously, the lensing ring and photon ring have only small and negligible contributions, respectively. We also found that shadows and rings exhibit different and exciting features when the disk is located at different positions. For static and infalling spherical accretions, it is evident that the size of shadows is always the same for both accretions. This implies that shadows are only related to space-time geometry in this case. The luminosity of the shadow and photon sphere is closely associated with the Doppler effect and the emissivity per unit volume j(νe). In addition, the influence of dark matter and cosmological constant on the observed intensity of shadows and rings is carefully emphasized throughout this paper. Finally, we obtained the burring images of shadows and rings using the nominal resolution of the event horizon telescope. We also studied the upper limits of the X-clod dark matter parameter β using the data of the shadow of M87.
基金Supported by National Natural Science Foundation of China(11875095)Basic Research Project of Science and Technology Committee of Chongqing(cstc2018jcyjA2480,cstc2019jcyjA2091)
文摘As a charged fermion drops into a BTZ black hole, the laws of thermodynamics and the weak cosmic censorship conjecture are investigated in both the normal and extended phase space, where the cosmological parameter and renormalization length are regarded as extensive quantities. In the normal phase space, the first and second law of thermodynamics, and the weak cosmic censorship are found to be valid. In the extended phase space, although the first law and weak cosmic censorship conjecture remain valid, the second law is dependent on the variation of the renormalization energy dK. Moreover, in the extended phase space, the configurations of extremal and near-extremal black holes are not changed, as they are stable, while in the normal phase space, the extremal and near-extremal black holes evolve into non-extremal black holes.
基金Supported by the National Natural Science Foundation of China (11675140,11705005,12375043)the Innovation and Development Joint Foundation of Chongqing Natural Science Foundation (CSTB2022NSCQ-LZX0021)the Basic Research Project of Science and Technology Committee of Chongqing (CSTB2023NSCQ-MSX0324)。
文摘We study the Einstein images of a charged Rastall AdS black hole(BH)within the fabric of AdS/CFT correspondence.Considering the holographic setup,we analyze the amplitude of the total response function for various values of model parameters.With an increase in parameterλand temperature T,the amplitude of the response function decreases,while it increases with an increase in electric charge e and chemical potentialμ.The influence of frequencyωalso plays an important role in the bulk field,as it is found that decreasingωleads to an increase in the periods of the waves,which means that the amplitude of the response function also depends on the wave source.The relation between T and the inverse of the horizon for various values of parameterλis interpreted under fixed values of other involved parameters.These,in turn,affect the behavior of the response function and the Einstein ring,which may be used to differentiate the present study from previous ones.We construct the holographic images of the BH in bulk via a special optical system.The results show that the Einstein ring always appears with concentric stripes at the position of the north pole,and this ring transforms into a luminosity-deformed ring or bright light spot when the distant observer lies away from the north pole.Finally,we discuss the influence of the associated parameters on the Einstein ring radius,which is consistent with wave optics.
基金Supported by the National Natural Science Foundation of China(11675140,11705005,12375043)the Innovation and Development Joint Foundation of Chongqing Natural Science Foundation(CSTB2022NSCQ-LZX0021)the Basic Research Project of Science and Technology Committee of Chongqing(CSTB2023NSCQ-MSX0324)。
文摘Using AdS/CFT correspondence,we analyze the holographic Einstein images via the response function of the complex scalar field as a probe wave on an AdS Schwarzschild scalar-tensor-vector gravity(STVG)black hole(BH).We find that the amplitude of the response function||decreases with increasing values of coupling parameter a and increases with decreasing temperature T.The frequencyωof the wave source also plays a significant role in wave periods;as we increase the values ofω,the periods of waves decrease,indicating that the total response function closely depends on the wave source.Further,we investigate the optical appearance of the holographic images of the BH in bulk.We found that the holographic ring always appears with surrounding concentric stripes when the observer is located at the north pole,and an extremely bright ring appears when the observer is at the position of the photon sphere of the BH.This ring changes into a luminosity-deformed ring or a bright light spot as the observational angle changes.The corresponding brightness profiles show that the luminosity of the ring decreases and the shadow radius increases with increasing values of a.The relation between temperature T and the inverse of the horizonh_e is discussed;T is small at the beginning of the horizon he and then increases as the horizon radius increases.This effect can be used to distinguish the STVG BH solution from other BH solutions.Moreover,these significant features are also reflected in the Einstein ring and corresponding brightness profiles.In addition,we compare the results obtained by wave optics and geometric optics,which align well,implying that the holographic scheme adopted in this study is valid.
基金supported by the National Key R&D Program of China(No.2018YFB1501104)Key Program for International S&T Cooperation Projects of China(No.2017YFE0107700)+1 种基金National Natural Science Foundation of China(Grant No.41805088)Natural Science Foundation of Shanghai(No.18ZR1449100).
文摘This study undertook verification of the applicability and accuracy of wind data measured using a WindCube V2 Doppler Wind Lidar(DWL).The data were collected as part of a field experiment in Zhoushan,Zhejiang Province(China),which was conducted by Shanghai Typhoon Institute of China Meteorological Administration during the passage of Super Typhoon Lekima(2019).The DWL measurements were compared with balloon-borne GPS radiosonde(GPS sonde)data,which were acquired using balloons launched from the DWL location.Results showed that wind speed measured by GPS sonde at heights of<100 m is unreliable owing to the drift effect.Optimal agreement(at heights of>100 m)was found for DWL-measured wind speed time-averaged during the ascent of the GPS sonde from the ground surface to the height of 270 m(correlation coefficient:0.82;root mean square(RMS):2.19 m·h^(-1)).Analysis revealed that precipitation intensity(PI)exerts considerable influence on both the carrier-to-noise ratio and the rate of missing DWL data;however,PI has minimal effect on the wind speed bias of DWL measurements.Specifically,the rate of missing DWL data increased with increasing measurement height and PI.For PI classed as heavy rain or less(PI<12 mm·h^(-1)),the DWL data below 300 m were considered valid,whereas for PI classed as a severe rainstorm(PI>90 m·h^(-1)),only data below 100 m were valid.Up to the height of 300 m,the RMS of the DWL measurements was nearly half that of wind profile radar(WPR)estimates(4.32 m·s^(-1)),indicating that DWL wind data are more accurate than WPR data under typhoon conditions.
基金Supported by the National Natural Science Foundation of China(11875095)Basic Research Project of Science and Technology Committee of Chongqing(cstc2018jcyj A2480)
文摘Considering the cosmological constant as the pressure,this study addresses the laws of thermodynamics and weak cosmic censorship conjecture in the Reissner-Nordstrom-AdS black hole surrounded by quintessence dark energy under charged Particle absorption.The first law of thermodynamics i5 found to be valid as a Particle is absorbed by the black hole.The second law,however,is violated for the extremal and near-extremal black holes,because the entropy of these black hole decrease.Moreover,we find that the extremal black hole does not change its configuration in the extended phase space,implying that the weak cosmic censorship conjecture is valid.Remarkably,the near-extremal black hole can be overcharged beyond the extremal condition under charged particle absorption.Hence,the cosmic censorship conjecture could be violated for the near-extremal black hole in the extended phase space.For comparison,we also discuss the first law,second law,and the weak cosmic censorship conjecture in normal phase space,and find that all of them are valid in this case.
基金Supported by the National Natural Science Foundation of China(11875095,11675140,11705005)Basic Research Project of Science and Technology Committee of Chongqing(cstc2018jcyjA2480)。
文摘In this study,we examine the laws of thermodynamics and the weak cosmic censorship conjecture in the normal and extended phase spaces of Born-Infeld-anti-de Sitter black holes by considering a charged particle absorption.In the normal phase space,the first and second laws of thermodynamics as well as the weak cosmic censorship are still valid.However,in the extended phase space,the second law of thermodynamics is violated for double-horizon black holes and part of single-horizon black holes.The first law of thermodynamics and the weak cosmic censorship conjecture are still valid for all types of black holes.In addition,we found that the shift of the metric function,which determines the locations of the horizons,takes the same form at the minimum point in both the normal and extended phase spaces,indicating that the weak cosmic censorship conjecture is independent of the thermodynamic phase space.
