Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.Th...Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.The problem of heat transfer between the air and concrete has been simplified to the concrete’s heat dissipation boundary.However,in the case of tubular concrete structures,where air inlet and outlet are relatively limited,the internal air temperature does not dissipate promptly to the external environment as it rises.To accurately simulate the temperature and creep stress in tubular concrete structures with enclosed air spaces during construction,we establish an air–concrete coupled heat transfer model according to the principles of conjugate heat transfer,and the accuracy of the model is verified through experiments.Furthermore,we conduct a case study to analyze the impact of airflow within the ship lock corridor on concrete temperature and creep stress.The results demonstrate that enhancing airflow within the corridor can significantly reduce the maximum concrete temperature.Compared with cases in which airflow within the corridor is neglected,the maximum concrete temperature and maximum tensile stress can be reduced by 12.5℃ and 0.7 MPa,respectively,under a wind speed of 4 m/s.The results of the traditional calculation method are relatively close to those obtained at a wind speed of 1 m/s.However,the temperature reduction process in the traditional method is faster,and the method yields greater tensile stress values for the corridor location.展开更多
Mathematical physics equations are often utilized to describe physical phenomena in various fields of science and engineering.One such equation is the Fourier equation,which is a commonly used and effective method for...Mathematical physics equations are often utilized to describe physical phenomena in various fields of science and engineering.One such equation is the Fourier equation,which is a commonly used and effective method for evaluating the effectiveness of temperature control measures for mass concrete.One important measure for temperature control in mass concrete is the use of cooling water pipes.However,the mismatch of grids between large-scale concrete models and small-scale cooling pipe models can result in a significant waste of calculation time when using the finite element method.Moreover,the temperature of the water in the cooling pipe needs to be iteratively calculated during the thermal transfer process.The substructure method can effectively solve this problem,and it has been validated by scholars.The Abaqus/Python secondary development technology provides engineers with enough flexibility to combine the substructure method with an iteration algorithm,which enables the creation of a parametric modeling calculation for cooling water pipes.This paper proposes such a method,which involves iterating the water pipe boundary and establishing the water pipe unit substructure to numerically simulate the concrete temperature field that contains a cooling water pipe.To verify the feasibility and accuracy of the proposed method,two classic numerical examples were analyzed.The results showed that this method has good applicability in cooling pipe calculations.When the value of the iteration parameterαis 0.4,the boundary temperature of the cooling water pipes can meet the accuracy requirements after 4∼5 iterations,effectively improving the computational efficiency.Overall,this approach provides a useful tool for engineers to analyze the temperature control measures accurately and efficiently for mass concrete,such as cooling water pipes,using Abaqus/Python secondary development.展开更多
By relying on the major projects of Beijing-Zhangjiakou HSR,China's railway industry has integrated and applied several digital intelligence technologies to form a complete set of intelligent HSR 1.0 technology,wh...By relying on the major projects of Beijing-Zhangjiakou HSR,China's railway industry has integrated and applied several digital intelligence technologies to form a complete set of intelligent HSR 1.0 technology,which has been popularized and applied to several new lines.With the continuous deepening of intelligent applications in construction,equipment,operation and other fields,there is an increasingly urgent need for integrated sharing and analysis of models and data.The paper analyzes the connotation and key points of model-data integration and puts forward the overall architecture of model-data integration platform composed of model-data convergence tier,model-data storage tier,model-data management tier,model-data calculation tier,model data aggregation tier,etc.Moreover,it looks forward to the prospect of leading key technologies and multiple innovative key technologies such as intelligent engineering survey and generative design,all-discipline intelligent construction,digital twin of railway engineering,CR450 intelligent EMU,new generation of dedicated mobile communication for railway (5G-R), operation safety protection based on multi-source information perception, transmission and fusion analysis, displacement-based full-travel intelligent service (MaaS+), intelligent comprehensive dispatching of regional railway network, wheel-rail integrated intelligent maintenance of EMU, etc. It can provide guidance and reference for digital railway construction and intelligent HSR 2.0 scientific & technological breakthroughs.展开更多
The mechanical properties, corrosion resistance and microstructures of high performance steel （HPS） was investigated by tensile testing machine, Charpy V-Notch （CVN） testing machine, cyclic immersion corrosion tes...The mechanical properties, corrosion resistance and microstructures of high performance steel （HPS） was investigated by tensile testing machine, Charpy V-Notch （CVN） testing machine, cyclic immersion corrosion tester, XRD, optical microscopy （OM）, scanning electron microscopy （SEM）, and electron probe micro-analyzer （EPMA）. The results showed that significant differences existed in the tensile strength, yield strength and impact toughness between HPS and PCS. After 72 h cyclic immersion accelerated corrosion test, the inner rust layer on HPS was com- posed of a-FeOOH phase and denser than that on PCS that was a mixture of a-FeOOH and Fe3 04. The rust formed on HPS provides better protection and HPS has lower corrosion rates than PCS. Copper and chromium in HPS en- rich in the rust layer and enhance the compactness of the rust layer. Based on the results of the accelerated corrosion tests and rust layer analysis, the roles of Cu and Cr against corrosion are discussed, providing HPS with chemical specification which has been industrially successful to produce weathering steel for bridge structure.展开更多
The weldability of 12MnNiVR was examined in terms of the simulated HAZ continuous cooling transformation (SH-CCT) diagram,microstructure and mechanical properties of the simulated coarse grain heat-affected zone (CGHA...The weldability of 12MnNiVR was examined in terms of the simulated HAZ continuous cooling transformation (SH-CCT) diagram,microstructure and mechanical properties of the simulated coarse grain heat-affected zone (CGHAZ).When t 8/5 is shorter,the microstructure mainly consists of lath bainite.When t 8/5 is 60 s,the microstructure becomes coarser bainite.Some acicular ferrite appears beside lath bainite when t 8/5 =100s.Finally,a microstructure composed of polygonal ferrite,acicular ferrite,and small amount pearlite is obtained with a small amount of bainite at t 8/5 】100s.With the increase of t 8/5,the hardness of CGHAZ decreases considerably.The minimum impact toughness of CGHAZ appears at t 8/5 =100s.The hardness and the toughness of CGHAZ remain above the specified values for steel 12MnNiVR.展开更多
基金This work was supported by Construction Simulation and Support Optimization of Hydraulic Tunnel Based on Bonded Block-Synthetic Rock Mass Method and Hubei Province Postdoctoral Innovative Practice Position.
文摘Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.The problem of heat transfer between the air and concrete has been simplified to the concrete’s heat dissipation boundary.However,in the case of tubular concrete structures,where air inlet and outlet are relatively limited,the internal air temperature does not dissipate promptly to the external environment as it rises.To accurately simulate the temperature and creep stress in tubular concrete structures with enclosed air spaces during construction,we establish an air–concrete coupled heat transfer model according to the principles of conjugate heat transfer,and the accuracy of the model is verified through experiments.Furthermore,we conduct a case study to analyze the impact of airflow within the ship lock corridor on concrete temperature and creep stress.The results demonstrate that enhancing airflow within the corridor can significantly reduce the maximum concrete temperature.Compared with cases in which airflow within the corridor is neglected,the maximum concrete temperature and maximum tensile stress can be reduced by 12.5℃ and 0.7 MPa,respectively,under a wind speed of 4 m/s.The results of the traditional calculation method are relatively close to those obtained at a wind speed of 1 m/s.However,the temperature reduction process in the traditional method is faster,and the method yields greater tensile stress values for the corridor location.
文摘Mathematical physics equations are often utilized to describe physical phenomena in various fields of science and engineering.One such equation is the Fourier equation,which is a commonly used and effective method for evaluating the effectiveness of temperature control measures for mass concrete.One important measure for temperature control in mass concrete is the use of cooling water pipes.However,the mismatch of grids between large-scale concrete models and small-scale cooling pipe models can result in a significant waste of calculation time when using the finite element method.Moreover,the temperature of the water in the cooling pipe needs to be iteratively calculated during the thermal transfer process.The substructure method can effectively solve this problem,and it has been validated by scholars.The Abaqus/Python secondary development technology provides engineers with enough flexibility to combine the substructure method with an iteration algorithm,which enables the creation of a parametric modeling calculation for cooling water pipes.This paper proposes such a method,which involves iterating the water pipe boundary and establishing the water pipe unit substructure to numerically simulate the concrete temperature field that contains a cooling water pipe.To verify the feasibility and accuracy of the proposed method,two classic numerical examples were analyzed.The results showed that this method has good applicability in cooling pipe calculations.When the value of the iteration parameterαis 0.4,the boundary temperature of the cooling water pipes can meet the accuracy requirements after 4∼5 iterations,effectively improving the computational efficiency.Overall,this approach provides a useful tool for engineers to analyze the temperature control measures accurately and efficiently for mass concrete,such as cooling water pipes,using Abaqus/Python secondary development.
文摘By relying on the major projects of Beijing-Zhangjiakou HSR,China's railway industry has integrated and applied several digital intelligence technologies to form a complete set of intelligent HSR 1.0 technology,which has been popularized and applied to several new lines.With the continuous deepening of intelligent applications in construction,equipment,operation and other fields,there is an increasingly urgent need for integrated sharing and analysis of models and data.The paper analyzes the connotation and key points of model-data integration and puts forward the overall architecture of model-data integration platform composed of model-data convergence tier,model-data storage tier,model-data management tier,model-data calculation tier,model data aggregation tier,etc.Moreover,it looks forward to the prospect of leading key technologies and multiple innovative key technologies such as intelligent engineering survey and generative design,all-discipline intelligent construction,digital twin of railway engineering,CR450 intelligent EMU,new generation of dedicated mobile communication for railway (5G-R), operation safety protection based on multi-source information perception, transmission and fusion analysis, displacement-based full-travel intelligent service (MaaS+), intelligent comprehensive dispatching of regional railway network, wheel-rail integrated intelligent maintenance of EMU, etc. It can provide guidance and reference for digital railway construction and intelligent HSR 2.0 scientific & technological breakthroughs.
文摘The mechanical properties, corrosion resistance and microstructures of high performance steel （HPS） was investigated by tensile testing machine, Charpy V-Notch （CVN） testing machine, cyclic immersion corrosion tester, XRD, optical microscopy （OM）, scanning electron microscopy （SEM）, and electron probe micro-analyzer （EPMA）. The results showed that significant differences existed in the tensile strength, yield strength and impact toughness between HPS and PCS. After 72 h cyclic immersion accelerated corrosion test, the inner rust layer on HPS was com- posed of a-FeOOH phase and denser than that on PCS that was a mixture of a-FeOOH and Fe3 04. The rust formed on HPS provides better protection and HPS has lower corrosion rates than PCS. Copper and chromium in HPS en- rich in the rust layer and enhance the compactness of the rust layer. Based on the results of the accelerated corrosion tests and rust layer analysis, the roles of Cu and Cr against corrosion are discussed, providing HPS with chemical specification which has been industrially successful to produce weathering steel for bridge structure.
文摘The weldability of 12MnNiVR was examined in terms of the simulated HAZ continuous cooling transformation (SH-CCT) diagram,microstructure and mechanical properties of the simulated coarse grain heat-affected zone (CGHAZ).When t 8/5 is shorter,the microstructure mainly consists of lath bainite.When t 8/5 is 60 s,the microstructure becomes coarser bainite.Some acicular ferrite appears beside lath bainite when t 8/5 =100s.Finally,a microstructure composed of polygonal ferrite,acicular ferrite,and small amount pearlite is obtained with a small amount of bainite at t 8/5 】100s.With the increase of t 8/5,the hardness of CGHAZ decreases considerably.The minimum impact toughness of CGHAZ appears at t 8/5 =100s.The hardness and the toughness of CGHAZ remain above the specified values for steel 12MnNiVR.
