Requirements of self-compacting concrete （SCC） applied in pre-stressed mass concrete structures include high fluidity, high elastic modulus, low adiabatic temperature rise and low drying shrinkage, which cannot be s...Requirements of self-compacting concrete （SCC） applied in pre-stressed mass concrete structures include high fluidity, high elastic modulus, low adiabatic temperature rise and low drying shrinkage, which cannot be satisfied by ordinary SCC. In this study, in order to solve the problem, a few principles of SCC design were proposed and the effects of binder amount, fly ash （FA） substitution, aggregate content and gradation on the workability, temperature rise, drying shrinkage and elastic modulus of SCC were investigated. The results and analysis indicate that the primary factor influencing the fluidity was paste content, and the main methods improving the elastic modulusof SCC were a lower sand ratio and an optimized coarse aggregate gradation. Lower adiabatic temperature rise and drying shrinkage were beneficial for decreasing the cement content. Further, based on the optimization of mixture, a C50 grade SCC （with binder amount of only 480 kg/ m3, fly ash substitution of 40%, sand ratio of 51% and proper coarse aggregate gradation （Vs.~0 mm： V10-16 ram： V16.20 mm= 30%： 30%：40%）） with superior workability was successfully prepared. The temperature rise and drying shrinkage of the prepared SCC were significantly reduced, and the elastic modulus reached 37.6 GPa at 28 d.展开更多
The cable-strut structural system is statically and kinematically indeterminate. The initial pre-stress is a key factor for determining the shape and load carrying capacity. A new numerical algorithm is presented here...The cable-strut structural system is statically and kinematically indeterminate. The initial pre-stress is a key factor for determining the shape and load carrying capacity. A new numerical algorithm is presented herein for the initial pre-stress finding procedure of complete cable-strut assembly. This method is based on the linear adjustment theory and does not take into account the material behavior. By using this method,the initial pre-stress of the multi self-stress modes can be found easily and the cal-culation process is simplified and efficient also. Finally,the initial pre-stress and structural performances of a particular Levy cable dome are analyzed comprehensively. The algorithm has proven to be efficient and correct,and the numerical results are valuable for practical design of Levy cable dome.展开更多
The tensile cable-strut structure is a self-equilibrate pre-stressed system.The initial pre-stress cal- culation is the fundamental structural analysis.A new numerical procedure was developed.The force density method ...The tensile cable-strut structure is a self-equilibrate pre-stressed system.The initial pre-stress cal- culation is the fundamental structural analysis.A new numerical procedure was developed.The force density method is the cornerstone of analytical formula,and then introduced into linear adjustment theory;the least square least norm solution,the optimized initial pre-stress,is yielded.The initial pre-stress and structural performances of a particular single-layer saddle-shaped cable-net structure were analyzed with the developed method,which is proved to be efficient and correct.The modal analyses were performed with respect to various pre-stress levels.Finally,the structural performances were investigated comprehensively.展开更多
Determining initial pretension values of pre-stressed cables is one of the key problems for a steel mega frame and pre-stressed composite bracing structure.Through the mechanical analysis of the composite bracing unde...Determining initial pretension values of pre-stressed cables is one of the key problems for a steel mega frame and pre-stressed composite bracing structure.Through the mechanical analysis of the composite bracing under vertical loading,the critical factors deciding the initial pretention value were found.According to these factors,a rule for the initial pretension value was put forward.The determination equations were acquired based on the principle of force equilibrium at nodes.The numerical results indicate that the internal force disequilibrium in composite bracings resulted from symmetrical load can be eliminated only in a symmetrical way,so that initial pretention values are decided only by vertical loads.The influencing coefficient leveling method,taking into account interactions between story and story,is accurate and feasible.展开更多
An anchor bearing plate transfers the anchoring force from anchor plate to the concrete and the pre-stress is formed in the concrete structure. Currently, the main type of anchor bearing plate is cast iron. It is brit...An anchor bearing plate transfers the anchoring force from anchor plate to the concrete and the pre-stress is formed in the concrete structure. Currently, the main type of anchor bearing plate is cast iron. It is brittle during transportation and tension process. This paper presents a new type of anchor bearing plate combined stamping with welding forming. The structure of the new type anchor bearing plate is introduced. The stress states of the anchor bearing plate and anchorage zone under work are studied. Various specifications of anchor bearing plate are studied by ANSYS finite element analysis software following the AASHTO specification. The analysis results are compared with the results of the same type of OVM round-shaped anchor plate. The study results show that the new pre-stressed anchor plates combined stamping with welding forming are feasible and more sturdy which can meet the engineering demand.展开更多
Pre-stressed structure and its application for civil engineering.Specificity of external loads of ships.Corresponded specificity of controllable pre-stressing.An example of pre-stressed structure and an decreasing est...Pre-stressed structure and its application for civil engineering.Specificity of external loads of ships.Corresponded specificity of controllable pre-stressing.An example of pre-stressed structure and an decreasing estimation of its mass(about 10%of the full displacement).Possibility of wider application.展开更多
Concrete structure is commonly used in the anchorages of a large cable-suspended pipeline crossing construction.With the increase of span and load,the stress on the concrete anchorages may rise rapidly.In case of trad...Concrete structure is commonly used in the anchorages of a large cable-suspended pipeline crossing construction.With the increase of span and load,the stress on the concrete anchorages may rise rapidly.In case of traditional anchoring structurefixed by anchor rods,concrete cracking will occur,thereby reducing the anchorage life.To solve this problem,the pre-stressed structure was designed to effectively improve the ef-ficiency of anchoring and reduce engineering cost.In the crossing construction of ChinaeMyanmar Gas Pipeline,the pre-stressed technology was used to establish an effective pre-stressed anchoring system,which integrates the pre-stressed structures(e.g.tunnel anchorages in the anchors)and the optimization measures(e.g.positioning mode,anchorage structure,concrete placement,pre-stressed,and medium injection),in line with the crossing structure and load features of this project.The system can delay the occurrence of concrete cracking and enhance the stress durability of the structure and anchoring efficiency.This technology has been successfully applied in the crossing construction of Chi-naeMyanmar Gas Pipeline,with good economic and social benefits,indicating that this technology is a new effective solution to the opti-mization of suspended pipeline anchorage structures,providing technical support for the development of pipeline crossing structure.展开更多
Pre-stressed rope reinforced anti-sliding pile is a composite anti-sliding structure.It is made up of pre-stressed rope and general anti-sliding pile.It can bring traditional anti-sliding pile's retaining performa...Pre-stressed rope reinforced anti-sliding pile is a composite anti-sliding structure.It is made up of pre-stressed rope and general anti-sliding pile.It can bring traditional anti-sliding pile's retaining performance into full play,and to treat with landslide fast and economically.The difference between them is that the pre-stressed rope will transfix the whole anti-sliding pile through a prearranged pipe in this structure.The working mechanics,the design method and economic benefit are studied.The results show that the pre-stressed rope reinforced anti-sliding pile can treat with the small and middle landslides or high slopes well and possess the notable advantage of technology and economic.展开更多
The paper presents a selected group of tension-strut structural systems designed for the construction of lightweight dome covers of large spans, which can be comparatively easy to assembly and have rises of which can ...The paper presents a selected group of tension-strut structural systems designed for the construction of lightweight dome covers of large spans, which can be comparatively easy to assembly and have rises of which can be relatively small. This will allow significant decrease costs of erection and maintenance of objects covered by these roof structures. The proposed systems have been obtained from the results of suitable transformations of a chosen type of double-layer space frame and an appropriate arrangement of tetrahedron modules in the space of each of the newly designed type of the structural system. All these systems are built by means of concentric hoops having their own integral spatial stiffness obtained after an appropriate pre-stressing. Particular hoops can be mounted on the ground level and then one by one will be hoisted to the designed positions where they will be connected by means of special sets of the tension members. Due to these structural features, the assembly process of each system should be relatively simple, fast and not expensive. The whole tension-strut structure has to be connected to the compression perimeter ring and suitably pre-stressed. There are presented visualizations of the proposed systems prepared on the basis of the appropriate numerical models especially defined for each particular structure.展开更多
When the upper chord beam of the beam-string structure(BSS)is made of concrete-filled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on ...When the upper chord beam of the beam-string structure(BSS)is made of concrete-filled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on the design of the tensioning plans and selection of control measures for the BSS.In order to accurately obtain the bending stiffness of CFST beam and clarify its impact on the mechanical properties of composite BSS during con-struction,the influence of some factors such as height-width ratio,wall thickness of steel tube,elasticity modulus of concrete,and friction coefficient on the bending stiffness are analyzed parametrically by the numerical simula-tion technology based on an actual project.The calculation formula of the equivalent bending stiffness of CFST is also established through mathematical statistical simulation.Then,the equivalent bending stiffness is introduced into the construction and use stages of the composite BSS,respectively,and the mechanical properties such as prestress-tensioning control value,structural deformation,and internal force of key members are comparatively analyzed when adopting two different construction plans.Moreover,the optimal construction plan of concrete placementfirst and then prestress-tensioning is proposed.展开更多
The objectives of this study are to explain the repairing and strengthening methods which are used to improve the structural performance of the bridge structure,to analyze the static and dynamic responses after streng...The objectives of this study are to explain the repairing and strengthening methods which are used to improve the structural performance of the bridge structure,to analyze the static and dynamic responses after strengthening,and to evaluate the performance of the bridge structure after repairing and strengthening.The methods of repairing and strengthening include reconstruction the deck of the bridge by casting 10 cm layer of concrete,strengthening the web and bottom floor of box girders of middle spans and side spans by sticking the steel plates,strengthening the whole bridge structure by using external pre-stressing tendons,and treatment the cracks.The results of theoretical analysis show that the values of tensile stress and vertical deflection are decreased and the compressive stress is increased after strengthening.There are not tensile stresses are appeared in the sections of the bridge structure.The modal analysis results show that the value of natural frequency is equal to 2.09 Hz which is more than the values before strengthening which is equal to 1.64 Hz,indicating that the stiffness of the bridge structure is improved and the strengthening process is effective to improve the cracks resistance and bearing capacity of the bridge structure.展开更多
Concrete members historically have used either pre-stressed steel or steel bars. In recent years there has been an increased interest in the use of fiber reinforced polymer （FRP） materials. However, the flexure beha...Concrete members historically have used either pre-stressed steel or steel bars. In recent years there has been an increased interest in the use of fiber reinforced polymer （FRP） materials. However, the flexure behavior of a hybrid system reinforced by the combination of pre-stressed steel and glass fiber reinforced （GFRP） is still relatively unknown. The purpose of this work is to study this. Two slabs of 100 and 150-millimeter thickness, with a span of 2.1 m reinforced with both pre-stressing steel and GFRP were constructed and tested to failure using ACI 318-11 and ACI 440.1 R-15. The concrete had strength of 31 MPa and the slabs were respectively reinforced with 5#4 bars and 3#5 bars. Each slab had 37.41 mm2 prestressing wire with a failure stress of 1722.5 MPa. The experimental flexural strength and deflection of slabs were compared with their respective sizes theoretical slabs. The theoretical slabs were either reinforced with pre-stressed steel or GFRP rebars, or a hybrid system. It was found that the hybrid system produces better results.展开更多
基金Funded by National Natural Science Foundation of China(Nos.U1134008 and 51302090)the Fundamental Research Funds for the Central Universities(No.2015ZJ0005)
文摘Requirements of self-compacting concrete （SCC） applied in pre-stressed mass concrete structures include high fluidity, high elastic modulus, low adiabatic temperature rise and low drying shrinkage, which cannot be satisfied by ordinary SCC. In this study, in order to solve the problem, a few principles of SCC design were proposed and the effects of binder amount, fly ash （FA） substitution, aggregate content and gradation on the workability, temperature rise, drying shrinkage and elastic modulus of SCC were investigated. The results and analysis indicate that the primary factor influencing the fluidity was paste content, and the main methods improving the elastic modulusof SCC were a lower sand ratio and an optimized coarse aggregate gradation. Lower adiabatic temperature rise and drying shrinkage were beneficial for decreasing the cement content. Further, based on the optimization of mixture, a C50 grade SCC （with binder amount of only 480 kg/ m3, fly ash substitution of 40%, sand ratio of 51% and proper coarse aggregate gradation （Vs.~0 mm： V10-16 ram： V16.20 mm= 30%： 30%：40%）） with superior workability was successfully prepared. The temperature rise and drying shrinkage of the prepared SCC were significantly reduced, and the elastic modulus reached 37.6 GPa at 28 d.
基金Project (No.863-705-210) supported by the Hi-Tech Research and Development Program (863) of China
文摘The cable-strut structural system is statically and kinematically indeterminate. The initial pre-stress is a key factor for determining the shape and load carrying capacity. A new numerical algorithm is presented herein for the initial pre-stress finding procedure of complete cable-strut assembly. This method is based on the linear adjustment theory and does not take into account the material behavior. By using this method,the initial pre-stress of the multi self-stress modes can be found easily and the cal-culation process is simplified and efficient also. Finally,the initial pre-stress and structural performances of a particular Levy cable dome are analyzed comprehensively. The algorithm has proven to be efficient and correct,and the numerical results are valuable for practical design of Levy cable dome.
文摘The tensile cable-strut structure is a self-equilibrate pre-stressed system.The initial pre-stress cal- culation is the fundamental structural analysis.A new numerical procedure was developed.The force density method is the cornerstone of analytical formula,and then introduced into linear adjustment theory;the least square least norm solution,the optimized initial pre-stress,is yielded.The initial pre-stress and structural performances of a particular single-layer saddle-shaped cable-net structure were analyzed with the developed method,which is proved to be efficient and correct.The modal analyses were performed with respect to various pre-stress levels.Finally,the structural performances were investigated comprehensively.
基金Project of Ministry of Housing and Urban-Rural Development of China(No.2012-K2-28)
文摘Determining initial pretension values of pre-stressed cables is one of the key problems for a steel mega frame and pre-stressed composite bracing structure.Through the mechanical analysis of the composite bracing under vertical loading,the critical factors deciding the initial pretention value were found.According to these factors,a rule for the initial pretension value was put forward.The determination equations were acquired based on the principle of force equilibrium at nodes.The numerical results indicate that the internal force disequilibrium in composite bracings resulted from symmetrical load can be eliminated only in a symmetrical way,so that initial pretention values are decided only by vertical loads.The influencing coefficient leveling method,taking into account interactions between story and story,is accurate and feasible.
文摘An anchor bearing plate transfers the anchoring force from anchor plate to the concrete and the pre-stress is formed in the concrete structure. Currently, the main type of anchor bearing plate is cast iron. It is brittle during transportation and tension process. This paper presents a new type of anchor bearing plate combined stamping with welding forming. The structure of the new type anchor bearing plate is introduced. The stress states of the anchor bearing plate and anchorage zone under work are studied. Various specifications of anchor bearing plate are studied by ANSYS finite element analysis software following the AASHTO specification. The analysis results are compared with the results of the same type of OVM round-shaped anchor plate. The study results show that the new pre-stressed anchor plates combined stamping with welding forming are feasible and more sturdy which can meet the engineering demand.
文摘Pre-stressed structure and its application for civil engineering.Specificity of external loads of ships.Corresponded specificity of controllable pre-stressing.An example of pre-stressed structure and an decreasing estimation of its mass(about 10%of the full displacement).Possibility of wider application.
基金2011-2012 S&T project of CNPC Chuanqing Drilling Engineering Co.,“Study on Applicability of crossing construction technology in Chinae-Myanmar pipeline project”。
文摘Concrete structure is commonly used in the anchorages of a large cable-suspended pipeline crossing construction.With the increase of span and load,the stress on the concrete anchorages may rise rapidly.In case of traditional anchoring structurefixed by anchor rods,concrete cracking will occur,thereby reducing the anchorage life.To solve this problem,the pre-stressed structure was designed to effectively improve the ef-ficiency of anchoring and reduce engineering cost.In the crossing construction of ChinaeMyanmar Gas Pipeline,the pre-stressed technology was used to establish an effective pre-stressed anchoring system,which integrates the pre-stressed structures(e.g.tunnel anchorages in the anchors)and the optimization measures(e.g.positioning mode,anchorage structure,concrete placement,pre-stressed,and medium injection),in line with the crossing structure and load features of this project.The system can delay the occurrence of concrete cracking and enhance the stress durability of the structure and anchoring efficiency.This technology has been successfully applied in the crossing construction of Chi-naeMyanmar Gas Pipeline,with good economic and social benefits,indicating that this technology is a new effective solution to the opti-mization of suspended pipeline anchorage structures,providing technical support for the development of pipeline crossing structure.
基金Supported by the Knowledge Innovation PrNeet of Chinese Aeademy of Sciences(KZCX2—306)
文摘Pre-stressed rope reinforced anti-sliding pile is a composite anti-sliding structure.It is made up of pre-stressed rope and general anti-sliding pile.It can bring traditional anti-sliding pile's retaining performance into full play,and to treat with landslide fast and economically.The difference between them is that the pre-stressed rope will transfix the whole anti-sliding pile through a prearranged pipe in this structure.The working mechanics,the design method and economic benefit are studied.The results show that the pre-stressed rope reinforced anti-sliding pile can treat with the small and middle landslides or high slopes well and possess the notable advantage of technology and economic.
文摘The paper presents a selected group of tension-strut structural systems designed for the construction of lightweight dome covers of large spans, which can be comparatively easy to assembly and have rises of which can be relatively small. This will allow significant decrease costs of erection and maintenance of objects covered by these roof structures. The proposed systems have been obtained from the results of suitable transformations of a chosen type of double-layer space frame and an appropriate arrangement of tetrahedron modules in the space of each of the newly designed type of the structural system. All these systems are built by means of concentric hoops having their own integral spatial stiffness obtained after an appropriate pre-stressing. Particular hoops can be mounted on the ground level and then one by one will be hoisted to the designed positions where they will be connected by means of special sets of the tension members. Due to these structural features, the assembly process of each system should be relatively simple, fast and not expensive. The whole tension-strut structure has to be connected to the compression perimeter ring and suitably pre-stressed. There are presented visualizations of the proposed systems prepared on the basis of the appropriate numerical models especially defined for each particular structure.
基金supported by the Project on Excellent Post-Graduate Dissertation of Hohai University,Nanjing,China(422003508)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(SJCX23_0187+2 种基金422003287)the National Natural Science Foundation of China(52250410359)Young Elite Scientists Sponsorship Program by Jiangsu Provincial Association for Science and Technology(TJ-2023-043).
文摘When the upper chord beam of the beam-string structure(BSS)is made of concrete-filled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on the design of the tensioning plans and selection of control measures for the BSS.In order to accurately obtain the bending stiffness of CFST beam and clarify its impact on the mechanical properties of composite BSS during con-struction,the influence of some factors such as height-width ratio,wall thickness of steel tube,elasticity modulus of concrete,and friction coefficient on the bending stiffness are analyzed parametrically by the numerical simula-tion technology based on an actual project.The calculation formula of the equivalent bending stiffness of CFST is also established through mathematical statistical simulation.Then,the equivalent bending stiffness is introduced into the construction and use stages of the composite BSS,respectively,and the mechanical properties such as prestress-tensioning control value,structural deformation,and internal force of key members are comparatively analyzed when adopting two different construction plans.Moreover,the optimal construction plan of concrete placementfirst and then prestress-tensioning is proposed.
文摘The objectives of this study are to explain the repairing and strengthening methods which are used to improve the structural performance of the bridge structure,to analyze the static and dynamic responses after strengthening,and to evaluate the performance of the bridge structure after repairing and strengthening.The methods of repairing and strengthening include reconstruction the deck of the bridge by casting 10 cm layer of concrete,strengthening the web and bottom floor of box girders of middle spans and side spans by sticking the steel plates,strengthening the whole bridge structure by using external pre-stressing tendons,and treatment the cracks.The results of theoretical analysis show that the values of tensile stress and vertical deflection are decreased and the compressive stress is increased after strengthening.There are not tensile stresses are appeared in the sections of the bridge structure.The modal analysis results show that the value of natural frequency is equal to 2.09 Hz which is more than the values before strengthening which is equal to 1.64 Hz,indicating that the stiffness of the bridge structure is improved and the strengthening process is effective to improve the cracks resistance and bearing capacity of the bridge structure.
文摘Concrete members historically have used either pre-stressed steel or steel bars. In recent years there has been an increased interest in the use of fiber reinforced polymer （FRP） materials. However, the flexure behavior of a hybrid system reinforced by the combination of pre-stressed steel and glass fiber reinforced （GFRP） is still relatively unknown. The purpose of this work is to study this. Two slabs of 100 and 150-millimeter thickness, with a span of 2.1 m reinforced with both pre-stressing steel and GFRP were constructed and tested to failure using ACI 318-11 and ACI 440.1 R-15. The concrete had strength of 31 MPa and the slabs were respectively reinforced with 5#4 bars and 3#5 bars. Each slab had 37.41 mm2 prestressing wire with a failure stress of 1722.5 MPa. The experimental flexural strength and deflection of slabs were compared with their respective sizes theoretical slabs. The theoretical slabs were either reinforced with pre-stressed steel or GFRP rebars, or a hybrid system. It was found that the hybrid system produces better results.
