This article focuses on the control of cracks in prestressed concrete structures.It explains the stress characteristics,influencing factors,and causes of crack formation during construction.The article introduces adva...This article focuses on the control of cracks in prestressed concrete structures.It explains the stress characteristics,influencing factors,and causes of crack formation during construction.The article introduces advanced technologies such as intelligent prestressed tensioning,highlights key aspects like high-performance concrete mix design,and discusses various monitoring and control methods.It also covers their practical applications and achievements in real-world projects,and looks ahead to future development directions.展开更多
Crack control of basement roof slab is a key technical challenge to ensure building safety and durability.Based on the requirements of“General Specification for Concrete Structures”(GB55008-2021),this paper systemat...Crack control of basement roof slab is a key technical challenge to ensure building safety and durability.Based on the requirements of“General Specification for Concrete Structures”(GB55008-2021),this paper systematically analyses the causes of cracks,and puts forward a whole-process prevention and control system covering design optimization,low-shrinkage material proportioning,fine control of construction technology,and dynamic monitoring and repair.Through structural finite element simulation,wireless sensor network real-time monitoring,and carbon fibre fabric reinforcement test,the effectiveness of the multi-technology synergistic control framework is verified,and the engineering cases show that the crack width after repair is stable within 0.1mm,and the bearing capacity is increased by more than 30%.The study provides theoretical support for crack prevention and control in super-long underground projects,and looks forward to the direction of integration application of BIM technology and intelligent materials.展开更多
This study presents a decoupling control scheme of fluid catalytic cracking unit to account for the high interaction between two temperature control loops. The feed flow rate load disturbance is introduced to test the...This study presents a decoupling control scheme of fluid catalytic cracking unit to account for the high interaction between two temperature control loops. The feed flow rate load disturbance is introduced to test the proposed decoupling control scheme. Through simulation study shown that the decoupling is effective, stable and it presents advantage over controller without decoupler. Also, this scheme is able to offer good dynamic performance for most disturbances.展开更多
The J-integral as a controlling parameter was applied to the crack growing process in an elastic-plastic state by Hutchinson and Paris[1], and Shih et. al[2]. An engineering approach based on J-integral was proposed b...The J-integral as a controlling parameter was applied to the crack growing process in an elastic-plastic state by Hutchinson and Paris[1], and Shih et. al[2]. An engineering approach based on J-integral was proposed by Ref.[3]. Obviously, it is necessary to determine whether J is really a bask controlling parameter. It has been shown from the results given in this paper that it is not bask, but the Jn-integral defined in this paper is a proper controlling parameter for crack growth in an clastic-plastic state.展开更多
High-grade(API 5L X80)and large-diameter(OD 1422 mm)line pipes are used in the Sino-Russian eastern route gas pipeline project for high pressure(12 MPa)transmission,and this can significantly increase the transmission...High-grade(API 5L X80)and large-diameter(OD 1422 mm)line pipes are used in the Sino-Russian eastern route gas pipeline project for high pressure(12 MPa)transmission,and this can significantly increase the transmission capacity and meet China's energy strategic demand.With the increase of steel grade,transmission pressure,pipe diameter and design coefficient,however,ductile crack of line pipes becomes the dominant crack mode,so it is necessary to focus on crack arrest and control study.In this paper,therefore,an intensive study was performed on the Battelle Two-Curve(BTC)method which is the major solution to the calculation of arrest toughness,as well as the crack resistance curve and decompression curve.Based on the study,the principle and application range of the BTC method were confirmed.In addition,a series of analysis were conducted on the issues which occurred when the BTC method was applied to high-strength,high-toughness line pipe steel,and the commonly used modified approaches to BTC calculation results were also provided.After the crack control scheme of the X80 large OD 1422 mm line pipes for the Russian Bovanenkovo-Ukhta was reviewed,the BTC calculation results were corrected on the basis of the design parameters of the Sino-Russian eastern routine gas pipeline project,the Charpy V-notched(CVN)impact energy which meets the project requirement was finally worked out to be 245 J.展开更多
The "Anti-floating Technical Standard for Construction Engineering" (JGJ476-2019) issued by the Ministry of Housing and Urban-rural Development on March 1, 2020 contains specific regulations and requirements...The "Anti-floating Technical Standard for Construction Engineering" (JGJ476-2019) issued by the Ministry of Housing and Urban-rural Development on March 1, 2020 contains specific regulations and requirements for crack control design of anti-floating anchor bolts. Among them, the anti-floating design grade is Grade A, which is designed according to the principle of no cracks, and the anchoring slurry should not generate tensile stress under the standard combination of load effect. The anti-floating design grade is Class B, which is designed according to crack control. The tensile stress in the anchoring slurry should not be greater than the axial tensile strength of the anchoring slurry under the standard combination of load effect. In order to ensure the safety of the design, while achieving the principles of clear and definite theoretical concepts and taking into account of economy, this paper analyzes and discusses the basic concepts, stress process, design principles and methods of the prestressed anti-floating anchor rod, and at the same time gives the matters needing attention and relevant suggestions in the design process.展开更多
A detailed study of the capabilities of artificial neural networks to diagnoses cracks in massive concrete structures is presented. This paper includes the components of the expert system such as design thought, basic...A detailed study of the capabilities of artificial neural networks to diagnoses cracks in massive concrete structures is presented. This paper includes the components of the expert system such as design thought, basic structure, building of knowledge base and the implementation of neural network applied model. The realizing method of neural network based clustering algorithm in the knowledge base and self study is analyzed emphatically and stimulated by means of the computer. From the above study, some important conclusions have been drawn and some new viewpoints have been suggested.展开更多
1 Project positioning Baihetan Hydropower Station is classified as the second of the four hydropower cascades in the lower reaches of the Jinsha River:Wudongde,Baihetan,Xiluodu and Xiangjiaba.As an important backbone ...1 Project positioning Baihetan Hydropower Station is classified as the second of the four hydropower cascades in the lower reaches of the Jinsha River:Wudongde,Baihetan,Xiluodu and Xiangjiaba.As an important backbone project for China to implement the strategy of West-to-East Power Transmission and optimize the energy structure,it constitutes an important part of the Yangtze River flood control system.Located at the junction of Ningnan County,Sichuan Province and Qiaojia County,Yunnan Province,the hydropower station is the largest hydropower project under construction in the world,with a unit capacity of million-kilowatts ranking the highest in the world and a total installed capacity of 16 million kW,second only to the Three Gorges Project,ranking the second in the world.展开更多
文摘This article focuses on the control of cracks in prestressed concrete structures.It explains the stress characteristics,influencing factors,and causes of crack formation during construction.The article introduces advanced technologies such as intelligent prestressed tensioning,highlights key aspects like high-performance concrete mix design,and discusses various monitoring and control methods.It also covers their practical applications and achievements in real-world projects,and looks ahead to future development directions.
文摘Crack control of basement roof slab is a key technical challenge to ensure building safety and durability.Based on the requirements of“General Specification for Concrete Structures”(GB55008-2021),this paper systematically analyses the causes of cracks,and puts forward a whole-process prevention and control system covering design optimization,low-shrinkage material proportioning,fine control of construction technology,and dynamic monitoring and repair.Through structural finite element simulation,wireless sensor network real-time monitoring,and carbon fibre fabric reinforcement test,the effectiveness of the multi-technology synergistic control framework is verified,and the engineering cases show that the crack width after repair is stable within 0.1mm,and the bearing capacity is increased by more than 30%.The study provides theoretical support for crack prevention and control in super-long underground projects,and looks forward to the direction of integration application of BIM technology and intelligent materials.
文摘This study presents a decoupling control scheme of fluid catalytic cracking unit to account for the high interaction between two temperature control loops. The feed flow rate load disturbance is introduced to test the proposed decoupling control scheme. Through simulation study shown that the decoupling is effective, stable and it presents advantage over controller without decoupler. Also, this scheme is able to offer good dynamic performance for most disturbances.
文摘The J-integral as a controlling parameter was applied to the crack growing process in an elastic-plastic state by Hutchinson and Paris[1], and Shih et. al[2]. An engineering approach based on J-integral was proposed by Ref.[3]. Obviously, it is necessary to determine whether J is really a bask controlling parameter. It has been shown from the results given in this paper that it is not bask, but the Jn-integral defined in this paper is a proper controlling parameter for crack growth in an clastic-plastic state.
文摘High-grade(API 5L X80)and large-diameter(OD 1422 mm)line pipes are used in the Sino-Russian eastern route gas pipeline project for high pressure(12 MPa)transmission,and this can significantly increase the transmission capacity and meet China's energy strategic demand.With the increase of steel grade,transmission pressure,pipe diameter and design coefficient,however,ductile crack of line pipes becomes the dominant crack mode,so it is necessary to focus on crack arrest and control study.In this paper,therefore,an intensive study was performed on the Battelle Two-Curve(BTC)method which is the major solution to the calculation of arrest toughness,as well as the crack resistance curve and decompression curve.Based on the study,the principle and application range of the BTC method were confirmed.In addition,a series of analysis were conducted on the issues which occurred when the BTC method was applied to high-strength,high-toughness line pipe steel,and the commonly used modified approaches to BTC calculation results were also provided.After the crack control scheme of the X80 large OD 1422 mm line pipes for the Russian Bovanenkovo-Ukhta was reviewed,the BTC calculation results were corrected on the basis of the design parameters of the Sino-Russian eastern routine gas pipeline project,the Charpy V-notched(CVN)impact energy which meets the project requirement was finally worked out to be 245 J.
文摘The "Anti-floating Technical Standard for Construction Engineering" (JGJ476-2019) issued by the Ministry of Housing and Urban-rural Development on March 1, 2020 contains specific regulations and requirements for crack control design of anti-floating anchor bolts. Among them, the anti-floating design grade is Grade A, which is designed according to the principle of no cracks, and the anchoring slurry should not generate tensile stress under the standard combination of load effect. The anti-floating design grade is Class B, which is designed according to crack control. The tensile stress in the anchoring slurry should not be greater than the axial tensile strength of the anchoring slurry under the standard combination of load effect. In order to ensure the safety of the design, while achieving the principles of clear and definite theoretical concepts and taking into account of economy, this paper analyzes and discusses the basic concepts, stress process, design principles and methods of the prestressed anti-floating anchor rod, and at the same time gives the matters needing attention and relevant suggestions in the design process.
文摘A detailed study of the capabilities of artificial neural networks to diagnoses cracks in massive concrete structures is presented. This paper includes the components of the expert system such as design thought, basic structure, building of knowledge base and the implementation of neural network applied model. The realizing method of neural network based clustering algorithm in the knowledge base and self study is analyzed emphatically and stimulated by means of the computer. From the above study, some important conclusions have been drawn and some new viewpoints have been suggested.
文摘1 Project positioning Baihetan Hydropower Station is classified as the second of the four hydropower cascades in the lower reaches of the Jinsha River:Wudongde,Baihetan,Xiluodu and Xiangjiaba.As an important backbone project for China to implement the strategy of West-to-East Power Transmission and optimize the energy structure,it constitutes an important part of the Yangtze River flood control system.Located at the junction of Ningnan County,Sichuan Province and Qiaojia County,Yunnan Province,the hydropower station is the largest hydropower project under construction in the world,with a unit capacity of million-kilowatts ranking the highest in the world and a total installed capacity of 16 million kW,second only to the Three Gorges Project,ranking the second in the world.
