Steel tube slab (STS) structure, a novel pipe-roof structure, of which steel tubes are connected with flange plates, bolts and concrete, is an increasingly popular supporting structure for underground space developmen...Steel tube slab (STS) structure, a novel pipe-roof structure, of which steel tubes are connected with flange plates, bolts and concrete, is an increasingly popular supporting structure for underground space development. Whilst the load-bearing of pipe-roof structures has been the subject of much research, uncertainties of deformation mechanism and the derivation of reliable calculation methods remain a challenge. For efficient design and wider deployment, this paper presents a bidirectional bending test to investigate the bending stiffnesses, load capacities and deformation mechanisms. The results show that the STS specimens exhibit good ductility and experience bending failure, and their deformation curves follow a half-sine wave upon loading. On this basis, the development of an STS composite slab deformation prediction model is proposed, along with the estimation for its bending stiffness. Theoretical predictions are shown to be in good agreement with the experimental measurements, with a maximum error of less than 15%. The outcomes of this investigation can provide references for the design and application of STS structures.展开更多
Arching and cracking of joints between slabs have become a problem in China Railway Track System(CRTS)II slab track.The slab track is susceptible to complex temperature variations as a longitudinal continuous structur...Arching and cracking of joints between slabs have become a problem in China Railway Track System(CRTS)II slab track.The slab track is susceptible to complex temperature variations as a longitudinal continuous structure.Based on measured data,a thermal-mechanical coupling model of the track was established.The deformation characteristics and interfacial damage behavior of joints under typical temperature fields were studied.The findings indicate that the annual extreme temperature range of the slab track,fluctuates from−1.4 to 49.8℃.The annual temperature gradient within the vertical depth range of 0 to 0.2 m of the track varies between−16.19℃/m and 30.15℃/m.The vertical deformation of joints is significantly influenced by high temperatures,with a maximum measured deformation of 0.828 mm.The joint seams are primarily affected by low temperatures,which lead to a separation of 0.9 to 1.0 mm.Conversely,interlayer damage of joints is predominantly influenced by elevated temperatures.In summer,the maximum ratio of interface damage area in the joint can reach up to 95%,with the maximum debonding area ratio can be as high as 84%.The research results can provide help for joint damage regularity and deformation control of CRTS II slab track.展开更多
With the change of the main influencing factors such as structural configuration and impact conditions,reinforced concrete slabs exhibit different mechanical behaviors with different failure patterns,and the failure m...With the change of the main influencing factors such as structural configuration and impact conditions,reinforced concrete slabs exhibit different mechanical behaviors with different failure patterns,and the failure modes are transformed.In order to reveal the failure mode and transformation rule of reinforced concrete slabs under impact loads,a dynamic impact response test was carried out using a drop hammer test device.The dynamic data pertaining to the impact force,support reaction force,structural displacement,and reinforcement strain were obtained through the use of digital image correlation technology(DIC),impact force measurement,and strain measurement.The analysis of the ultimate damage state of the reinforced concrete slab identified four distinct types of impact failure modes:local failure by stamping,overall failure by stamping,local-overall coupling failure,and local failure by punching.Additionally,the influence laws of hammerhead shape,hammer height,and reinforcement ratio on the dynamic response and failure mode transformation of the slab were revealed.The results indicate that:(1)The local damage to the slab by the plane hammer is readily apparent,while the overall damage by the spherical hammer is more pronounced.(2)In comparison to the high reinforcement ratio slabs,the overall bending resistance of the low reinforcement ratio slabs is significantly inferior,and the slab back exhibits further cracks.(3)As the hammer height increases,the slab failure mode undergoes a transformation,shifting from local failure by stamping and overall failure by stamping to local-overall coupling failure and local failure by punching.(4)Three failure mode thresholds have been established,and by comparing the peak impact force with the failure thresholds,the failure mode of the slab can be effectively determined.展开更多
In order to accommodate higher speeds,heavier axle weights,and vibration damping criteria,a new floating slab structure was proposed.The new type of floating slab track structure was composed of three prefabricated fl...In order to accommodate higher speeds,heavier axle weights,and vibration damping criteria,a new floating slab structure was proposed.The new type of floating slab track structure was composed of three prefabricated floating slabs longitudinally interconnected with magnesium ammonium phosphate concrete(MPC).This study investigated the dynamic performance of the structure.We constructd a full-scale indoor experimental model to scrutinize the disparities in the impact performance between a longitudinally connected floating slab track and its longitudinally disconnected counterpart.Additionally,a long-term fatigue experiment was conducted to assess the impact performance of longitudinally connected floating slab tracks under fatigue loading.The findings are described in the following.1)The new structure effectively suppresses ground vibrations,exhibiting a well-balanced energy distribution profile.However,the imposition of fatigue loading leads to a reduction in the damping performance of the steel spring damping system,thereby reducing its capacity to attenuate structural vibrations and leading to an increase in ground vibration energy;2)After 107 loading cycles,the attenuation rate of the vibration acceleration for the MPC increases by 171.9%.Conversely,at the corresponding disconnected location,the attenuation rate of ground vibration acceleration decreases by 65.6%.In conclusion,longitudinally connected floating slab tracks exhibit superior vibration reduction performance.While the vibration reduction performance of longitudinally connected floating slab tracks may diminish to some extent during long-term service,these tracks continue to meet specific vibration reduction requirements.展开更多
To address the issue of extreme thermal-induced arching in CRTS II slab tracks due to joint damage,an optimized joint repair model was proposed.First,the formula for calculating the safe temperature rise of the track ...To address the issue of extreme thermal-induced arching in CRTS II slab tracks due to joint damage,an optimized joint repair model was proposed.First,the formula for calculating the safe temperature rise of the track was derived based on the principle of stationary potential energy.Considering interlayer evolution and structural crack propagation,an optimized joint repair model for the track was established and validated.Subsequently,the impact of joint repair on track damage and arch stability under extreme temperatures was studied,and a comprehensive evaluation of the feasibility of joint repair and the evolution of damage after repair was conducted.The results show that after the joint repair,the temperature rise of the initial damage of the track structure can be increased by 11℃.Under the most unfavorable heating load with a superimposed temperature gradient,the maximum stiffness degradation index SDEG in the track structure is reduced by about 81.16%following joint repair.The joint repair process could effectively reduce the deformation of the slab arching under high temperatures,resulting in a reduction of 93.96%in upward arching deformation.After repair,with the damage to interfacing shear strength,the track arch increases by 2.616 mm.展开更多
The interface of slab track laid in cold regions is prone to debonding under the coupling of freeze-thaw cyclesand temperature loads.Based on the composite specimen tests,the parameters of cohesive zone model were obt...The interface of slab track laid in cold regions is prone to debonding under the coupling of freeze-thaw cyclesand temperature loads.Based on the composite specimen tests,the parameters of cohesive zone model were obtained andused in a simulation model of CRTS III prefabricated slab track to study the interlayer damage.The results show that 1)the digital image correlation(DIC)technique can accurately capture the strain field changes on the interface of compositespecimens under splitting and shear loading;2)when the temperature gradient is−40℃/m−60℃/m,the interfacedamage of the slab track is minimal and presents different patterns of expansion under positive and negative temperaturegradients,each corresponding to damage of the cohesive element dominated by shear stress and normal tensile stress,respectively;3)the reduction of the elastic modulus at the concrete base after freeze-thaw inhibits interface damage andleads to a higher starting temperature gradient load,but cracking can occur on the concrete base after 150 freeze-thaws.For this reason,in the light of damage control of both the interface and concrete base,the elastic modulus of the concretebase is 54%or over that without freeze-thaw cycles.展开更多
基金Project(BK20210721) supported by the Natural Science Foundation of Jiangsu Province,ChinaProjects(52108380,52078506) supported by the National Natural Science Foundation of ChinaProject(2023A1515012159) supported by the Guangdong Basic and Applied Basic Research Foundation,China。
文摘Steel tube slab (STS) structure, a novel pipe-roof structure, of which steel tubes are connected with flange plates, bolts and concrete, is an increasingly popular supporting structure for underground space development. Whilst the load-bearing of pipe-roof structures has been the subject of much research, uncertainties of deformation mechanism and the derivation of reliable calculation methods remain a challenge. For efficient design and wider deployment, this paper presents a bidirectional bending test to investigate the bending stiffnesses, load capacities and deformation mechanisms. The results show that the STS specimens exhibit good ductility and experience bending failure, and their deformation curves follow a half-sine wave upon loading. On this basis, the development of an STS composite slab deformation prediction model is proposed, along with the estimation for its bending stiffness. Theoretical predictions are shown to be in good agreement with the experimental measurements, with a maximum error of less than 15%. The outcomes of this investigation can provide references for the design and application of STS structures.
基金Projects(U23A20666,52178405)supported by the National Natural Science Foundation of ChinaProject(K2022G038)supported by the Science and Technology Research and Development Program of China State Railway Group Co.,Ltd.Project(2021B03)supported by the Science and Technology Plan of Shandong Provincial Department of Transportation,China。
文摘Arching and cracking of joints between slabs have become a problem in China Railway Track System(CRTS)II slab track.The slab track is susceptible to complex temperature variations as a longitudinal continuous structure.Based on measured data,a thermal-mechanical coupling model of the track was established.The deformation characteristics and interfacial damage behavior of joints under typical temperature fields were studied.The findings indicate that the annual extreme temperature range of the slab track,fluctuates from−1.4 to 49.8℃.The annual temperature gradient within the vertical depth range of 0 to 0.2 m of the track varies between−16.19℃/m and 30.15℃/m.The vertical deformation of joints is significantly influenced by high temperatures,with a maximum measured deformation of 0.828 mm.The joint seams are primarily affected by low temperatures,which lead to a separation of 0.9 to 1.0 mm.Conversely,interlayer damage of joints is predominantly influenced by elevated temperatures.In summer,the maximum ratio of interface damage area in the joint can reach up to 95%,with the maximum debonding area ratio can be as high as 84%.The research results can provide help for joint damage regularity and deformation control of CRTS II slab track.
基金Supported by the National Natural Science Foundation of China(Grant No.52078283)Shandong Provincial Natural Science Foundation(Project No.ZR2024MA094)。
文摘With the change of the main influencing factors such as structural configuration and impact conditions,reinforced concrete slabs exhibit different mechanical behaviors with different failure patterns,and the failure modes are transformed.In order to reveal the failure mode and transformation rule of reinforced concrete slabs under impact loads,a dynamic impact response test was carried out using a drop hammer test device.The dynamic data pertaining to the impact force,support reaction force,structural displacement,and reinforcement strain were obtained through the use of digital image correlation technology(DIC),impact force measurement,and strain measurement.The analysis of the ultimate damage state of the reinforced concrete slab identified four distinct types of impact failure modes:local failure by stamping,overall failure by stamping,local-overall coupling failure,and local failure by punching.Additionally,the influence laws of hammerhead shape,hammer height,and reinforcement ratio on the dynamic response and failure mode transformation of the slab were revealed.The results indicate that:(1)The local damage to the slab by the plane hammer is readily apparent,while the overall damage by the spherical hammer is more pronounced.(2)In comparison to the high reinforcement ratio slabs,the overall bending resistance of the low reinforcement ratio slabs is significantly inferior,and the slab back exhibits further cracks.(3)As the hammer height increases,the slab failure mode undergoes a transformation,shifting from local failure by stamping and overall failure by stamping to local-overall coupling failure and local failure by punching.(4)Three failure mode thresholds have been established,and by comparing the peak impact force with the failure thresholds,the failure mode of the slab can be effectively determined.
基金Project(2022-Major-14)supported by the Science and Technology Research and Development Program Project of China Railway Group Limited。
文摘In order to accommodate higher speeds,heavier axle weights,and vibration damping criteria,a new floating slab structure was proposed.The new type of floating slab track structure was composed of three prefabricated floating slabs longitudinally interconnected with magnesium ammonium phosphate concrete(MPC).This study investigated the dynamic performance of the structure.We constructd a full-scale indoor experimental model to scrutinize the disparities in the impact performance between a longitudinally connected floating slab track and its longitudinally disconnected counterpart.Additionally,a long-term fatigue experiment was conducted to assess the impact performance of longitudinally connected floating slab tracks under fatigue loading.The findings are described in the following.1)The new structure effectively suppresses ground vibrations,exhibiting a well-balanced energy distribution profile.However,the imposition of fatigue loading leads to a reduction in the damping performance of the steel spring damping system,thereby reducing its capacity to attenuate structural vibrations and leading to an increase in ground vibration energy;2)After 107 loading cycles,the attenuation rate of the vibration acceleration for the MPC increases by 171.9%.Conversely,at the corresponding disconnected location,the attenuation rate of ground vibration acceleration decreases by 65.6%.In conclusion,longitudinally connected floating slab tracks exhibit superior vibration reduction performance.While the vibration reduction performance of longitudinally connected floating slab tracks may diminish to some extent during long-term service,these tracks continue to meet specific vibration reduction requirements.
基金Project(K2022G038)supported by the Science Technology Research and Development Program of China State Railway Group Co.,LtdProject(52178405)supported by the National Natural Science Foundation of China。
文摘To address the issue of extreme thermal-induced arching in CRTS II slab tracks due to joint damage,an optimized joint repair model was proposed.First,the formula for calculating the safe temperature rise of the track was derived based on the principle of stationary potential energy.Considering interlayer evolution and structural crack propagation,an optimized joint repair model for the track was established and validated.Subsequently,the impact of joint repair on track damage and arch stability under extreme temperatures was studied,and a comprehensive evaluation of the feasibility of joint repair and the evolution of damage after repair was conducted.The results show that after the joint repair,the temperature rise of the initial damage of the track structure can be increased by 11℃.Under the most unfavorable heating load with a superimposed temperature gradient,the maximum stiffness degradation index SDEG in the track structure is reduced by about 81.16%following joint repair.The joint repair process could effectively reduce the deformation of the slab arching under high temperatures,resulting in a reduction of 93.96%in upward arching deformation.After repair,with the damage to interfacing shear strength,the track arch increases by 2.616 mm.
基金Project(52425213)supported by the National Science Fund for Distinguished Young Scholars of ChinaProjects(52278461,52308467)supported by the National Natural Science Foundation of China+1 种基金Projects(2021YFF0502100,2021YFB2600900)supported by the National Key R&D Program of ChinaProject(2022JDTD0015)supported by the Sichuan Province Youth Science and Technology Innovation Team,China。
文摘The interface of slab track laid in cold regions is prone to debonding under the coupling of freeze-thaw cyclesand temperature loads.Based on the composite specimen tests,the parameters of cohesive zone model were obtained andused in a simulation model of CRTS III prefabricated slab track to study the interlayer damage.The results show that 1)the digital image correlation(DIC)technique can accurately capture the strain field changes on the interface of compositespecimens under splitting and shear loading;2)when the temperature gradient is−40℃/m−60℃/m,the interfacedamage of the slab track is minimal and presents different patterns of expansion under positive and negative temperaturegradients,each corresponding to damage of the cohesive element dominated by shear stress and normal tensile stress,respectively;3)the reduction of the elastic modulus at the concrete base after freeze-thaw inhibits interface damage andleads to a higher starting temperature gradient load,but cracking can occur on the concrete base after 150 freeze-thaws.For this reason,in the light of damage control of both the interface and concrete base,the elastic modulus of the concretebase is 54%or over that without freeze-thaw cycles.
