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
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
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
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
Aβ-solidifying Ti-40 Al-9 V-0.5 Y(at.%)alloy with a high cracking sensitivity has been successfully fabricated by selective laser melting(SLM)in this study.The influence factors for cracking sensitivity,cracking beha...Aβ-solidifying Ti-40 Al-9 V-0.5 Y(at.%)alloy with a high cracking sensitivity has been successfully fabricated by selective laser melting(SLM)in this study.The influence factors for cracking sensitivity,cracking behavior and crack inhibition mechanism were investigated.The results show that the effects of process parameters on cracking sensitivity strongly depend on the cooling rate in molten pool with different heat transfer modes.The conduction mode with higher cooling rates exhibits a higher cracking sensitivity in comparison to the keyhole mode.Microstructure characteristics and phase transformations controlled by cooling rate determine the inherent ductility ofβ-solidifyingγ-Ti Al alloys during SLM.On this basis,the formation and inhibition mechanism of solidification and cold cracking are proposed.Finally,the crackfree Ti-40 Al-9 V-0.5 Y sample with fine equiaxed microstructures and favorable mechanical properties(microhardness of 542±19 HV,yield strength of 1871±12 MPa,ultimate strength of 2106±13 MPa and ultimate compressive strain of 10.89±0.57%)can be produced by SLM.The strengthening mechanism can be attributed to grain refinement and precipitation strengthening.展开更多
A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the tem...A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the temperature and stress field of the Cao＇e Sluice during the construction period. From the calculated results, we can find that the temperaiure and stress of concrete cooled with plastic pipes are much lower than those of concrete without pipes. Moreover, plastic pipes could not be corroded by seawater. That is to say, a good effect of temperature control and cracking prevention can be achieved, which provides a useful reference for other similar nearshore concrete projects.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
Multi-layer laser cladding manufacturing is a newly developed rapid manufacturing technology. It is a powerful tool for direct fabrication of three-dimensional fully dense metal components and part repairing. In this ...Multi-layer laser cladding manufacturing is a newly developed rapid manufacturing technology. It is a powerful tool for direct fabrication of three-dimensional fully dense metal components and part repairing. In this paper, the microstructure evolution and properties of 316L stainless steel deposited with this technology was investigated, compact components with properties similar to the as-cast and wrought annealed material was obtained. Cracking was eliminated by introducing of supersonic vibration and application of parameter adjustment technologies.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
This paper proposes a case study in the control of a heavy oil pyrolysis/cracking furnace with a newly extended U-model based pole placement controller(U-PPC). The major work of the paper includes: 1) establishing a c...This paper proposes a case study in the control of a heavy oil pyrolysis/cracking furnace with a newly extended U-model based pole placement controller(U-PPC). The major work of the paper includes: 1) establishing a control oriented nonlinear dynamic model with Naphtha cracking and thermal dynamics; 2) analysing a U-model(i.e., control oriented prototype) representation of various popular process model sets; 3)designing the new U-PPC to enhance the control performance in pole placement and stabilisation; 4) taking computational bench tests to demonstrate the control system design and performance with a user-friendly step by step procedure.展开更多
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.
基金supported financially by the Pre-research Fund Project of Ministry of Equipment and Development of China(No.61409230301)the Fundamental Research Funds for the Central Universities through Program no.2019kfyXMPY005 and no.2019kfyXKJC042.
文摘Aβ-solidifying Ti-40 Al-9 V-0.5 Y(at.%)alloy with a high cracking sensitivity has been successfully fabricated by selective laser melting(SLM)in this study.The influence factors for cracking sensitivity,cracking behavior and crack inhibition mechanism were investigated.The results show that the effects of process parameters on cracking sensitivity strongly depend on the cooling rate in molten pool with different heat transfer modes.The conduction mode with higher cooling rates exhibits a higher cracking sensitivity in comparison to the keyhole mode.Microstructure characteristics and phase transformations controlled by cooling rate determine the inherent ductility ofβ-solidifyingγ-Ti Al alloys during SLM.On this basis,the formation and inhibition mechanism of solidification and cold cracking are proposed.Finally,the crackfree Ti-40 Al-9 V-0.5 Y sample with fine equiaxed microstructures and favorable mechanical properties(microhardness of 542±19 HV,yield strength of 1871±12 MPa,ultimate strength of 2106±13 MPa and ultimate compressive strain of 10.89±0.57%)can be produced by SLM.The strengthening mechanism can be attributed to grain refinement and precipitation strengthening.
基金supported by the National Natural Science Foundation of China (Grant No. 50779010)
文摘A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the temperature and stress field of the Cao＇e Sluice during the construction period. From the calculated results, we can find that the temperaiure and stress of concrete cooled with plastic pipes are much lower than those of concrete without pipes. Moreover, plastic pipes could not be corroded by seawater. That is to say, a good effect of temperature control and cracking prevention can be achieved, which provides a useful reference for other similar nearshore concrete projects.
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.
基金supported by the National Natural Science Foundation of China under the Grant No.50375096
文摘Multi-layer laser cladding manufacturing is a newly developed rapid manufacturing technology. It is a powerful tool for direct fabrication of three-dimensional fully dense metal components and part repairing. In this paper, the microstructure evolution and properties of 316L stainless steel deposited with this technology was investigated, compact components with properties similar to the as-cast and wrought annealed material was obtained. Cracking was eliminated by introducing of supersonic vibration and application of parameter adjustment technologies.
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.
基金partially supported by the National Natural Science Foundation of China(61273188,61473312)Taishan Scholar Construction Engineering Special Funding of Shandong
文摘This paper proposes a case study in the control of a heavy oil pyrolysis/cracking furnace with a newly extended U-model based pole placement controller(U-PPC). The major work of the paper includes: 1) establishing a control oriented nonlinear dynamic model with Naphtha cracking and thermal dynamics; 2) analysing a U-model(i.e., control oriented prototype) representation of various popular process model sets; 3)designing the new U-PPC to enhance the control performance in pole placement and stabilisation; 4) taking computational bench tests to demonstrate the control system design and performance with a user-friendly step by step procedure.
