Concrete slabs are widely used in modern railways to increase the inherent resilient quality of the tracks,provide safe and smooth rides,and reduce the maintenance frequency.In this paper,the elastic performance of a ...Concrete slabs are widely used in modern railways to increase the inherent resilient quality of the tracks,provide safe and smooth rides,and reduce the maintenance frequency.In this paper,the elastic performance of a novel slab trackform for high-speed railways is investigated using three-dimensional finite element modelling in Abaqus.It is then compared to the performance of a ballasted track.First,slab and ballasted track models are developed to replicate the full-scale testing of track sections.Once the models are calibrated with the experimental results,the novel slab model is developed and compared against the calibrated slab track results.The slab and ballasted track models are then extended to create linear dynamic models,considering the track geodynamics,and simulating train passages at various speeds,for which the Ledsgard documented case was used to validate the models.Trains travelling at low and high speeds are analysed to investigate the track deflections and the wave propagation in the soil,considering the issues associated with critical speeds.Various train loading methods are discussed,and the most practical approach is retained and described.Moreover,correlations are made between the geotechnical parameters of modern high-speed rail and conventional standards.It is found that considering the same ground condition,the slab track deflections are considerably smaller than those of the ballasted track at high speeds,while they show similar behaviour at low speeds.展开更多
This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment z...This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment zone.An experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was proposed.The composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab specimens.Two methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel beams.The experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal support.In contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading process.As the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan section.When the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span section.Since GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span section.All test specimens experienced compressive failure of concrete at the mid-span section.Calculation results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support section.The proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.展开更多
The dependence of the subduction regime on three-dimensional slab geometry poses a challenge for accurately estimating the evolving thermal structure of megathrusts globally. Although slab dips and ages have gained at...The dependence of the subduction regime on three-dimensional slab geometry poses a challenge for accurately estimating the evolving thermal structure of megathrusts globally. Although slab dips and ages have gained attention, the specific impacts of oblique subduction remain unmeasured. Here, we present an integrated thermal model that quantifies how slab morphology can shape the thermal state of megathrusts, such as those in the Makran Subduction Zone. The model considers both slab obliquity and depth variations along the trench. We find a considerable match between the slab petrological dehydration zone and the distribution of great crustal earthquakes. We suggest that the accumulation of fluids along megathrusts by slab metamorphism can foster more polarized conditions for decreasing plate coupling and increasing interplate ruptures. It is thus imperative to improve model representation and more realistically represent how drivers of slab geometry affect metamorphic transitions and the occurrence of earthquakes at megathrusts.展开更多
Combining with the physical model of level fluctuation in a thick slab continuous casting mold with the cross-section of 1500 mm×280 mm and argon blowing, the rationalities of estimating the level fluctuation by ...Combining with the physical model of level fluctuation in a thick slab continuous casting mold with the cross-section of 1500 mm×280 mm and argon blowing, the rationalities of estimating the level fluctuation by three traditional quantitative approaches were discussed, and the effects of gas flowrate, casting speed, and the immersion depth of submerged entry nozzle （SEN） on the level fluctuation were also investigated. As a result, it seems that three traditional quantitative approaches are not very suitable for estimating the level fluctuation in a mold with argon blowing, so a new approach for estimating level fluctuation in the mold with argon blowing was presented. The experimental results show that the level fluctuation is mainly in the region around the nozzle wall. When the casting speeds are larger than a certain value, there is the escape of large bubbles near the nozzle wall, which causes an obvious increase of level fluctuation. Furthermore, optimal process parameters, viz., the gas flowrate of 6 NL/min, the casting speed of 1.1 m/min, and the immersion depth of 170 mm, are presented to restrain the level fluctuation by a physical model.展开更多
In the thin slab continuous casting （TSCC） of steel, the issue of optimum fluid flow is very important due to higher casting speeds and has direct influence on the formation of solidified shells and the quality of f...In the thin slab continuous casting （TSCC） of steel, the issue of optimum fluid flow is very important due to higher casting speeds and has direct influence on the formation of solidified shells and the quality of final products. In the current work, a full-scale physical mod- eling of a thin slab easter on the basis of dimensionless Reynolds and Froude similarity criteria was constructed. The flow pattern in the funnel shaped mold with a new tetra-furcated submerged entry nozzle （SEN） was investigated. To determinate optimum operational parameters, some experiments were carried out under various casting conditions. The results show that the tetra-furcated design of the nozzle leads to a special flow pattern in the mold cavity with three-dimensional recirculating flow. It is also shown that the increase of casting speed and gas injection results in surface turbulence. On the other hand, using a higher depth of SEN decreases the vortex in the free surface of the caster. To avoid surface turbulent and related casting problems, it is recommended to use 30-cm and 40-cm SEN depth at the casting speeds of 3.5 and 4.5 m/min, respectively.展开更多
The optimal parameters were determined by the water modeling of slab casting. It was found that there are mainly three types of mold powder entrapment in slab continuous casting, i.e., the entrapment caused by the she...The optimal parameters were determined by the water modeling of slab casting. It was found that there are mainly three types of mold powder entrapment in slab continuous casting, i.e., the entrapment caused by the shearing flow near the narrow face of mold, the entrapment caused by vortexes around the submerged entry nozzle （SEN）, and the entrapment caused by the Ar bubbling. Both the velocity of the surface flow and the level fluctuation of the liquids are enlarged with increasing the casting speed, reducing the submersion depth of SEN, decreasing the downward angles of the nozzle outlets, and increasing the Ar flowrate, all of which increase the tendency of mold powder entrapment. Among the four above-mentioned factors, casting speed has the largest effect.展开更多
A steady three-dimensional fluid flow and solidification model was built based on CFD software by high-Reynolds-number and Lam-Bremhorst low-Reynolds-number k-ε model.During the simulation,the fixed-grid enthalpy-por...A steady three-dimensional fluid flow and solidification model was built based on CFD software by high-Reynolds-number and Lam-Bremhorst low-Reynolds-number k-ε model.During the simulation,the fixed-grid enthalpy-porosity technique was used to represent the solidification,and Darcy law was adopted to simulate the flow in mushy region.The prediction for steel flow and solidification was evaluated by the comparison of two turbulence models.It is found that both Lam-Bremhorst low-Reynolds-number and high-Reynolds-number k-ε models predict the same trend of the steel flow and temperature distribution.However,due to the effect of turbulent flow on heat transfer,the low-Reynolds-number turbulence model predicts longer penetration depth of molten steel in sub-mold region,less shell growth and higher shell surface temperature at the narrow face compared with standard k-ε model.展开更多
A heat transfer model on the solidification process has been established onthe basis of the technical conditions of the slab caster in No.3 steel works of Wuhan Iron & SteelCorporation, and the temperature field i...A heat transfer model on the solidification process has been established onthe basis of the technical conditions of the slab caster in No.3 steel works of Wuhan Iron & SteelCorporation, and the temperature field in the solidifying slab was calculated which was verified bythe measured slab surface temperature. The influences of the main operating factors includingcasting speed, spray cooling patterns, superheat of melt and slab size on the solidification processwere analyzed and the means of enhancing the slab temperature was brought forward. Raising thecasting speed to 1.3 m/min, controlling the flowrate of secondary cooling water and improving thecooling pattern at the lower segments of secondary cooling zone could improve the slab temperatureeffectively. And the increasing the superheat is adverse to the production of high temperature slab.展开更多
The internal cracks in continuously cast slabs are attributed to the excessive tensile strain occurring at the solidifying frontduring the continuous casting process. Based on the understanding, a model for diagnosing...The internal cracks in continuously cast slabs are attributed to the excessive tensile strain occurring at the solidifying frontduring the continuous casting process. Based on the understanding, a model for diagnosing the formation of the internal cracks was established, in which the strains at the solidifying front caused by' bulging, straightening or unbending, and roll misalignment were calculated and compared with a critical strain value to estimate whether the internal cracks form. Moreover, the established model was appliedto a real slab caster to reveal the distribution of the strains in casting direction and its effect on the internal cracks. It was proved that themodel was reliable and useful for optimizing the operation of continuous casting.展开更多
Dynamic model control technologies of secondary cooling and soft reduction of Baosteel are introduced. Model principle and control system architecture are summarized, as well as functions and features. Finally, applic...Dynamic model control technologies of secondary cooling and soft reduction of Baosteel are introduced. Model principle and control system architecture are summarized, as well as functions and features. Finally, applications of model technologies are discussed. The self-developed dynamic secondary cooling model and the dynamic soft reduction model have been applied on several casting machines inside and outside Baosteel, desired control effects were achieved with good stability and reliability. Temperature measurement results verified the correctness of model.展开更多
Non aqueous reactive polymer materials produced by the reaction of isocyanate and polyol have been widely used in infrastructure construction,which may be subjected to explosion loads during complex service conditions...Non aqueous reactive polymer materials produced by the reaction of isocyanate and polyol have been widely used in infrastructure construction,which may be subjected to explosion loads during complex service conditions.The blast response of composite materials is a crucial aspect for applications in engineering structures potentially subjected to extreme loadings.In this work,damage caused to rebar reinforced polymer slabs by surface explosive charges was studied experimentally and numerically.A total of 6 field tests were carried out to investigate the performances of the failure modes of rebar reinforced polymer slabs under contact and near-field explosions.The influence of explosive quantity(10-40 g)and stand-off distances(0-20 cm)at the damage modes were studied.The results show that the failure modes of rebar reinforced polymer slabs under near-field explosion mainly were bending and surface spalling,while under the impact of contact explosion,the failure modes were craters of the top surface,spalling of the bottom surface,and middle perforation.Furthermore,a detailed fully coupled model was developed and validated with the test data.The influences of explosive quantity and slab thickness on rebar reinforced polymer slabs under contact explosion were studied.Based on this,the calculation formula between breach diameter,explosive quantity,and slab thickness is fitted.展开更多
The determinations of flexural behavior of some engineering structures are based on different theories and equations, but it has been observed that some of these equations may not give true representation. This work h...The determinations of flexural behavior of some engineering structures are based on different theories and equations, but it has been observed that some of these equations may not give true representation. This work has looked into the difference that may occur between theoretical and experimental results. An experimental test carried out on models of waffle and solid slabs structures were described and results from twenty test samples are presented. Each specimen was subjected to an incremental axial loading of 1 kN interval after 28 days of casting. The flexural moments, deflections and crack width at failure were obtained. The experimental flexural crack and theoretical flexural cracks for both types of slabs were compared. The result for flexural moments for waffle was 5.526 kNm, while solid slab was 3.684 kNm. The deflections showed that waffle slabs has 3.64 mm while solid has 9.28 mm, hence waffle has a higher structural stiffness than solid slabs, but the flexural cracks did not give the same results especially for the estimated crack width. It was concluded that estimated results based on developed equations may not be accurate because it is based on ideal situation.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
Model study is an efficient method for optimizing the siructure of the mould and the submerged entry nozzle (SEN). Based on the similarity criteria, a full-scale water model has been established in accordance with the...Model study is an efficient method for optimizing the siructure of the mould and the submerged entry nozzle (SEN). Based on the similarity criteria, a full-scale water model has been established in accordance with the mould of thin-slab caster of the CSP (Compact Strip Production) operation. The effects of SEN structure including outlet area, outflow angle, nozzle width, thick-ness and immersion depth have been studied under high speed casting by measuring the amplitude and the impetus of top waves. By the orthogonal experiment design, not only the influence of the faCtors was estimated, but also the optimum work condition was judged. The rules of the fluid flow phenomena were summarized. The principle for choosing a reasonable structure of SEN was discussed.展开更多
In order to analyze the pavement stress caused by vehicle bumping at an approach slab, a simplified four-wheeled bi- axle vehicle-moving model is proposed. The effect of damping and vibration reduction in the process ...In order to analyze the pavement stress caused by vehicle bumping at an approach slab, a simplified four-wheeled bi- axle vehicle-moving model is proposed. The effect of damping and vibration reduction in the process of vehicle-moving is not considered. Based on the position change of vehicle wheels at the approach slab, the vehicle dynamic vibration equations are summarized. Meanwhile, the undetermined coefficients of the vibration equations are obtained using the boundary and initial conditions of the vehicle. The analytical motion solutions of rear and front wheels at different stages are concluded. Consequently, a four-wheeled vehicle model is developed and vibration equations are provided, which can be used to analyze the impact of complicated stress on pavement. The results show that the excessive stress and stress concentration will occur at the approach slab, and it needs to be strengthened.展开更多
基金Engineering and Physical Sciences Research Council (EPSRC) is also acknowledged for funding this work under Grant Number EP/N009207/1.
文摘Concrete slabs are widely used in modern railways to increase the inherent resilient quality of the tracks,provide safe and smooth rides,and reduce the maintenance frequency.In this paper,the elastic performance of a novel slab trackform for high-speed railways is investigated using three-dimensional finite element modelling in Abaqus.It is then compared to the performance of a ballasted track.First,slab and ballasted track models are developed to replicate the full-scale testing of track sections.Once the models are calibrated with the experimental results,the novel slab model is developed and compared against the calibrated slab track results.The slab and ballasted track models are then extended to create linear dynamic models,considering the track geodynamics,and simulating train passages at various speeds,for which the Ledsgard documented case was used to validate the models.Trains travelling at low and high speeds are analysed to investigate the track deflections and the wave propagation in the soil,considering the issues associated with critical speeds.Various train loading methods are discussed,and the most practical approach is retained and described.Moreover,correlations are made between the geotechnical parameters of modern high-speed rail and conventional standards.It is found that considering the same ground condition,the slab track deflections are considerably smaller than those of the ballasted track at high speeds,while they show similar behaviour at low speeds.
基金supported by National Natural Science Foundation of China(Project No.51878156,received by Wen-Wei Wang) and EPC Innovation Consulting Project for Longkou Nanshan LNG Phase I Receiving Terminal(Z2000LGENT0399,received by Wen-Wei Wang and ZhaoJun Zhang).
文摘This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment zone.An experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was proposed.The composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab specimens.Two methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel beams.The experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal support.In contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading process.As the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan section.When the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span section.Since GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span section.All test specimens experienced compressive failure of concrete at the mid-span section.Calculation results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support section.The proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.
基金benefited from the financial support of the Chinese Academy of Sciences Pioneer Hundred Talents Programthe Second Tibetan Plateau Scientific Expedition and Research Program (Grant No. 2019QZKK0708)+2 种基金the MEXT KAKENHI grant (Grant No. 21H05203)the Kobe University Strategic International Collaborative Research Grant (Type B Fostering Joint Research)the “Science of Slowto-Fast Earthquakes” project。
文摘The dependence of the subduction regime on three-dimensional slab geometry poses a challenge for accurately estimating the evolving thermal structure of megathrusts globally. Although slab dips and ages have gained attention, the specific impacts of oblique subduction remain unmeasured. Here, we present an integrated thermal model that quantifies how slab morphology can shape the thermal state of megathrusts, such as those in the Makran Subduction Zone. The model considers both slab obliquity and depth variations along the trench. We find a considerable match between the slab petrological dehydration zone and the distribution of great crustal earthquakes. We suggest that the accumulation of fluids along megathrusts by slab metamorphism can foster more polarized conditions for decreasing plate coupling and increasing interplate ruptures. It is thus imperative to improve model representation and more realistically represent how drivers of slab geometry affect metamorphic transitions and the occurrence of earthquakes at megathrusts.
基金supported by the Fundamental Research Funds for the Central Universities (No.100402017)China Postdoctoral Science Foundation (No.20080431153)Scientific Research Foundation for Doctor of Liaoning Province, China (No.20071020)
文摘Combining with the physical model of level fluctuation in a thick slab continuous casting mold with the cross-section of 1500 mm×280 mm and argon blowing, the rationalities of estimating the level fluctuation by three traditional quantitative approaches were discussed, and the effects of gas flowrate, casting speed, and the immersion depth of submerged entry nozzle （SEN） on the level fluctuation were also investigated. As a result, it seems that three traditional quantitative approaches are not very suitable for estimating the level fluctuation in a mold with argon blowing, so a new approach for estimating level fluctuation in the mold with argon blowing was presented. The experimental results show that the level fluctuation is mainly in the region around the nozzle wall. When the casting speeds are larger than a certain value, there is the escape of large bubbles near the nozzle wall, which causes an obvious increase of level fluctuation. Furthermore, optimal process parameters, viz., the gas flowrate of 6 NL/min, the casting speed of 1.1 m/min, and the immersion depth of 170 mm, are presented to restrain the level fluctuation by a physical model.
文摘In the thin slab continuous casting （TSCC） of steel, the issue of optimum fluid flow is very important due to higher casting speeds and has direct influence on the formation of solidified shells and the quality of final products. In the current work, a full-scale physical mod- eling of a thin slab easter on the basis of dimensionless Reynolds and Froude similarity criteria was constructed. The flow pattern in the funnel shaped mold with a new tetra-furcated submerged entry nozzle （SEN） was investigated. To determinate optimum operational parameters, some experiments were carried out under various casting conditions. The results show that the tetra-furcated design of the nozzle leads to a special flow pattern in the mold cavity with three-dimensional recirculating flow. It is also shown that the increase of casting speed and gas injection results in surface turbulence. On the other hand, using a higher depth of SEN decreases the vortex in the free surface of the caster. To avoid surface turbulent and related casting problems, it is recommended to use 30-cm and 40-cm SEN depth at the casting speeds of 3.5 and 4.5 m/min, respectively.
文摘The optimal parameters were determined by the water modeling of slab casting. It was found that there are mainly three types of mold powder entrapment in slab continuous casting, i.e., the entrapment caused by the shearing flow near the narrow face of mold, the entrapment caused by vortexes around the submerged entry nozzle （SEN）, and the entrapment caused by the Ar bubbling. Both the velocity of the surface flow and the level fluctuation of the liquids are enlarged with increasing the casting speed, reducing the submersion depth of SEN, decreasing the downward angles of the nozzle outlets, and increasing the Ar flowrate, all of which increase the tendency of mold powder entrapment. Among the four above-mentioned factors, casting speed has the largest effect.
文摘A steady three-dimensional fluid flow and solidification model was built based on CFD software by high-Reynolds-number and Lam-Bremhorst low-Reynolds-number k-ε model.During the simulation,the fixed-grid enthalpy-porosity technique was used to represent the solidification,and Darcy law was adopted to simulate the flow in mushy region.The prediction for steel flow and solidification was evaluated by the comparison of two turbulence models.It is found that both Lam-Bremhorst low-Reynolds-number and high-Reynolds-number k-ε models predict the same trend of the steel flow and temperature distribution.However,due to the effect of turbulent flow on heat transfer,the low-Reynolds-number turbulence model predicts longer penetration depth of molten steel in sub-mold region,less shell growth and higher shell surface temperature at the narrow face compared with standard k-ε model.
基金This work was financially sponsored by Jiangsu Youth Science Foundation (No.JDQ2001003).
文摘A heat transfer model on the solidification process has been established onthe basis of the technical conditions of the slab caster in No.3 steel works of Wuhan Iron & SteelCorporation, and the temperature field in the solidifying slab was calculated which was verified bythe measured slab surface temperature. The influences of the main operating factors includingcasting speed, spray cooling patterns, superheat of melt and slab size on the solidification processwere analyzed and the means of enhancing the slab temperature was brought forward. Raising thecasting speed to 1.3 m/min, controlling the flowrate of secondary cooling water and improving thecooling pattern at the lower segments of secondary cooling zone could improve the slab temperatureeffectively. And the increasing the superheat is adverse to the production of high temperature slab.
文摘The internal cracks in continuously cast slabs are attributed to the excessive tensile strain occurring at the solidifying frontduring the continuous casting process. Based on the understanding, a model for diagnosing the formation of the internal cracks was established, in which the strains at the solidifying front caused by' bulging, straightening or unbending, and roll misalignment were calculated and compared with a critical strain value to estimate whether the internal cracks form. Moreover, the established model was appliedto a real slab caster to reveal the distribution of the strains in casting direction and its effect on the internal cracks. It was proved that themodel was reliable and useful for optimizing the operation of continuous casting.
文摘Dynamic model control technologies of secondary cooling and soft reduction of Baosteel are introduced. Model principle and control system architecture are summarized, as well as functions and features. Finally, applications of model technologies are discussed. The self-developed dynamic secondary cooling model and the dynamic soft reduction model have been applied on several casting machines inside and outside Baosteel, desired control effects were achieved with good stability and reliability. Temperature measurement results verified the correctness of model.
基金supported by the National Natural Science Foundation of China(Grant Nos.52009126,51939008)Foundation of Hubei Key Laboratory of Blasting Engineering(Grant No.BL202104)First-class Project Special Funding of Yellow River Laboratory(No.YRL22IR08)。
文摘Non aqueous reactive polymer materials produced by the reaction of isocyanate and polyol have been widely used in infrastructure construction,which may be subjected to explosion loads during complex service conditions.The blast response of composite materials is a crucial aspect for applications in engineering structures potentially subjected to extreme loadings.In this work,damage caused to rebar reinforced polymer slabs by surface explosive charges was studied experimentally and numerically.A total of 6 field tests were carried out to investigate the performances of the failure modes of rebar reinforced polymer slabs under contact and near-field explosions.The influence of explosive quantity(10-40 g)and stand-off distances(0-20 cm)at the damage modes were studied.The results show that the failure modes of rebar reinforced polymer slabs under near-field explosion mainly were bending and surface spalling,while under the impact of contact explosion,the failure modes were craters of the top surface,spalling of the bottom surface,and middle perforation.Furthermore,a detailed fully coupled model was developed and validated with the test data.The influences of explosive quantity and slab thickness on rebar reinforced polymer slabs under contact explosion were studied.Based on this,the calculation formula between breach diameter,explosive quantity,and slab thickness is fitted.
文摘The determinations of flexural behavior of some engineering structures are based on different theories and equations, but it has been observed that some of these equations may not give true representation. This work has looked into the difference that may occur between theoretical and experimental results. An experimental test carried out on models of waffle and solid slabs structures were described and results from twenty test samples are presented. Each specimen was subjected to an incremental axial loading of 1 kN interval after 28 days of casting. The flexural moments, deflections and crack width at failure were obtained. The experimental flexural crack and theoretical flexural cracks for both types of slabs were compared. The result for flexural moments for waffle was 5.526 kNm, while solid slab was 3.684 kNm. The deflections showed that waffle slabs has 3.64 mm while solid has 9.28 mm, hence waffle has a higher structural stiffness than solid slabs, but the flexural cracks did not give the same results especially for the estimated crack width. It was concluded that estimated results based on developed equations may not be accurate because it is based on ideal situation.
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.
文摘Model study is an efficient method for optimizing the siructure of the mould and the submerged entry nozzle (SEN). Based on the similarity criteria, a full-scale water model has been established in accordance with the mould of thin-slab caster of the CSP (Compact Strip Production) operation. The effects of SEN structure including outlet area, outflow angle, nozzle width, thick-ness and immersion depth have been studied under high speed casting by measuring the amplitude and the impetus of top waves. By the orthogonal experiment design, not only the influence of the faCtors was estimated, but also the optimum work condition was judged. The rules of the fluid flow phenomena were summarized. The principle for choosing a reasonable structure of SEN was discussed.
基金The Doctoral Program of Central South University (No. 2010ybfz048)the National High Technology Research and Development Program of China (863 Program) (No. 2007AA021908)
文摘In order to analyze the pavement stress caused by vehicle bumping at an approach slab, a simplified four-wheeled bi- axle vehicle-moving model is proposed. The effect of damping and vibration reduction in the process of vehicle-moving is not considered. Based on the position change of vehicle wheels at the approach slab, the vehicle dynamic vibration equations are summarized. Meanwhile, the undetermined coefficients of the vibration equations are obtained using the boundary and initial conditions of the vehicle. The analytical motion solutions of rear and front wheels at different stages are concluded. Consequently, a four-wheeled vehicle model is developed and vibration equations are provided, which can be used to analyze the impact of complicated stress on pavement. The results show that the excessive stress and stress concentration will occur at the approach slab, and it needs to be strengthened.
