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2010 Vol. 40, No. 1
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2010, 40(1): 1-4.
doi: 10.13204/j.gyjz201001001
Abstract:
Cracking control in massive concreting has been a conventional but complicated problem.Since the very early application of massive concrete,researchers have been studying the cracking mechanism and methods to control them.It has been well known that concrete cracking is resulted from temperature changing (differential temperature) and cement hydration.However,to study and control the cracking by integrating the temperature with hydration mechanisms is a new topic.This paper presents an integrated stress control method based on the study which integrates the temperature with hydration mechanisms.The research result has been applied successfully to foundation concreting for a number of nuclear power plants.
Cracking control in massive concreting has been a conventional but complicated problem.Since the very early application of massive concrete,researchers have been studying the cracking mechanism and methods to control them.It has been well known that concrete cracking is resulted from temperature changing (differential temperature) and cement hydration.However,to study and control the cracking by integrating the temperature with hydration mechanisms is a new topic.This paper presents an integrated stress control method based on the study which integrates the temperature with hydration mechanisms.The research result has been applied successfully to foundation concreting for a number of nuclear power plants.
2010, 40(1): 5-7,23.
doi: 10.13204/j.gyjz201001002
Abstract:
Conservation methods and technical indicators of mass concrete construction are often selected based on engineering experience,combined with on-site curing according to temperature monitoring,which lacks theoretical foundation,and inappropriate conservation methods and technical indexes will lead to further escalation of construction cracks.In this paper,taking the base of a CPR1000 nuclear power plant for example,through various curing methods and technical indexes,the stress state of concrete is analyzed by finite element method,thereby optimizing the curing methods and technical indexes and then to guide the selection of curing measures.Theoretical analysis results show that the dynamic differentiated technical measures are more conducive to the quality of concrete.All these can provide experience accumulation and theoretical support for curing similar foundations.
Conservation methods and technical indicators of mass concrete construction are often selected based on engineering experience,combined with on-site curing according to temperature monitoring,which lacks theoretical foundation,and inappropriate conservation methods and technical indexes will lead to further escalation of construction cracks.In this paper,taking the base of a CPR1000 nuclear power plant for example,through various curing methods and technical indexes,the stress state of concrete is analyzed by finite element method,thereby optimizing the curing methods and technical indexes and then to guide the selection of curing measures.Theoretical analysis results show that the dynamic differentiated technical measures are more conducive to the quality of concrete.All these can provide experience accumulation and theoretical support for curing similar foundations.
2010, 40(1): 8-10,16.
doi: 10.13204/j.gyjz201001003
Abstract:
There is an inestimable role in a reasonable sliding layer for reducing cracks in mass concrete construction.Actually,many factors have an impact on cracks in concrete construction,but the fundamental and direct causes are temperature stress level and anti-crack measures.There are also many factors to generate different stress level,such as the size and the form of poured concrete foundation,hydration heat and rate of cementitious materials,curing measures,as well as the sliding ability of the sliding layer and so on.In this paper,the finite element models of the sliding layer and the overall structure are built,finite element analysis of temperature stress on upper structure with a sliding layer and strain-monitoring are carried out.The results from the theoretical analysis show that the sliding ability has a direct impact on the level of temperature stress,at the same time,according to results of the test and theoretical analysis,this paper has given quantitative models of the sliding characteristics,which provides practical methods and experience for the theoretical analysis for the batch CPR1000 nuclear power project or similar projects.
There is an inestimable role in a reasonable sliding layer for reducing cracks in mass concrete construction.Actually,many factors have an impact on cracks in concrete construction,but the fundamental and direct causes are temperature stress level and anti-crack measures.There are also many factors to generate different stress level,such as the size and the form of poured concrete foundation,hydration heat and rate of cementitious materials,curing measures,as well as the sliding ability of the sliding layer and so on.In this paper,the finite element models of the sliding layer and the overall structure are built,finite element analysis of temperature stress on upper structure with a sliding layer and strain-monitoring are carried out.The results from the theoretical analysis show that the sliding ability has a direct impact on the level of temperature stress,at the same time,according to results of the test and theoretical analysis,this paper has given quantitative models of the sliding characteristics,which provides practical methods and experience for the theoretical analysis for the batch CPR1000 nuclear power project or similar projects.
2010, 40(1): 11-13,63.
doi: 10.13204/j.gyjz201001004
Abstract:
This paper presents a study which analyzes the entire course of massive concreting and curing,and proposes a method to control the overall stresses of concrete by controlling the temperature.With this method,full consideration of the fast contraction stress of concrete can be made at the early stage and select a pouring method which can effectively lower the concrete stresses and prevent the concrete from cracking.
This paper presents a study which analyzes the entire course of massive concreting and curing,and proposes a method to control the overall stresses of concrete by controlling the temperature.With this method,full consideration of the fast contraction stress of concrete can be made at the early stage and select a pouring method which can effectively lower the concrete stresses and prevent the concrete from cracking.
2010, 40(1): 14-16.
doi: 10.13204/j.gyjz201001005
Abstract:
Prior to massive concreting,calculations shall be made to estimate the highest hydration temperature in order to determine the concrete stresses resulted from temperature.Hydration temperature is related to the type of raw materials used,the structural shape and dimensions,the construction environment,construction methods and sequences.This paper presents a study which investigated massive concreting temperature calculation methods.The result of this study has been used to estimate the temperature of foundation concreting for several nuclear power plants and excellent results have been obtained.
Prior to massive concreting,calculations shall be made to estimate the highest hydration temperature in order to determine the concrete stresses resulted from temperature.Hydration temperature is related to the type of raw materials used,the structural shape and dimensions,the construction environment,construction methods and sequences.This paper presents a study which investigated massive concreting temperature calculation methods.The result of this study has been used to estimate the temperature of foundation concreting for several nuclear power plants and excellent results have been obtained.
2010, 40(1): 17-20.
doi: 10.13204/j.gyjz201001006
Abstract:
Hot and humid environment brings difficulties to pouring concrete and curing of raft foundation for nuclear islands of nuclear power plants,it especially causes the high central temperature of the concrete and a great difference between internal and external temperature,which are harmful for controlling cracks.Based on the monitoring data of temperature strain in the process of pouring concrete of raft foundation for nuclear islands in hot and humid environment,a 3-D finite element numerical simulation model is set up and theoretical analysis results are given,controlling cracks on the concrete during the curing period is analyzed.There are no obvious cracks on the concrete after stripping.Which provides an important basis for crack control of pouring concrete of raft foundations for other nuclear power plants.
Hot and humid environment brings difficulties to pouring concrete and curing of raft foundation for nuclear islands of nuclear power plants,it especially causes the high central temperature of the concrete and a great difference between internal and external temperature,which are harmful for controlling cracks.Based on the monitoring data of temperature strain in the process of pouring concrete of raft foundation for nuclear islands in hot and humid environment,a 3-D finite element numerical simulation model is set up and theoretical analysis results are given,controlling cracks on the concrete during the curing period is analyzed.There are no obvious cracks on the concrete after stripping.Which provides an important basis for crack control of pouring concrete of raft foundations for other nuclear power plants.
2010, 40(1): 21-23.
doi: 10.13204/j.gyjz201001007
Abstract:
Current professional standard YBJ 22491 Technical Regulation of Mass Concrete Construction of Block Foundations doesn't account of conservation indicator calculation of mass concrete by finite element technique in construction.In order to adapt promulgation of the new GB/J 504962009 Technical Specification of Mass Concrete Construction and application of the finite element method,this paper attempts estimation of curing indexes by finite element method and accomplish successfully to guide the construction of a raft foundation.Through analysing theoretical value and measured value,the finite element method for guiding construction is feasible and preponderant.All these can provide a theoretic basis and practical evidences for the publication of the new specifications.
Current professional standard YBJ 22491 Technical Regulation of Mass Concrete Construction of Block Foundations doesn't account of conservation indicator calculation of mass concrete by finite element technique in construction.In order to adapt promulgation of the new GB/J 504962009 Technical Specification of Mass Concrete Construction and application of the finite element method,this paper attempts estimation of curing indexes by finite element method and accomplish successfully to guide the construction of a raft foundation.Through analysing theoretical value and measured value,the finite element method for guiding construction is feasible and preponderant.All these can provide a theoretic basis and practical evidences for the publication of the new specifications.
2010, 40(1): 24-26,38.
doi: 10.13204/j.gyjz201001008
Abstract:
Through theoretic analysis, it can be estimated the concrete temperature and contraction stresses for CPR1000 nuclear power plant massive concretepours. However, it is extremely difficult to modelormeasure the strains due to concrete internalself-restraints. This paper present is a practical ethod, which can fully understand the stress state of the concrete through measuring the concrete elastic strains by a specially engineered measuring device. The resulted information is used further to provide abasis forcontrolling cracking in theconcrete.
Through theoretic analysis, it can be estimated the concrete temperature and contraction stresses for CPR1000 nuclear power plant massive concretepours. However, it is extremely difficult to modelormeasure the strains due to concrete internalself-restraints. This paper present is a practical ethod, which can fully understand the stress state of the concrete through measuring the concrete elastic strains by a specially engineered measuring device. The resulted information is used further to provide abasis forcontrolling cracking in theconcrete.
2010, 40(1): 27-30,4.
doi: 10.13204/j.gyjz201001009
Abstract:
It is proposed a new method of controlling cracks of pouring mass concrete for raft foundation of nuclear power plants.Software ANSYS is used to set up a 3-D finite element numerical simulation model for pouring concrete of raft foundation.A scheme of monitoring the temperature strain is worked out,optimized curing curves are designed,and the curing measures are adjusted dynamically during the curing period.At present,this method is already applied in raft foundation for 6 nuclear islands of different nuclear power plants,there are no obvious cracks on the concrete after stripping.This method has a bright future of application and popularizing.
It is proposed a new method of controlling cracks of pouring mass concrete for raft foundation of nuclear power plants.Software ANSYS is used to set up a 3-D finite element numerical simulation model for pouring concrete of raft foundation.A scheme of monitoring the temperature strain is worked out,optimized curing curves are designed,and the curing measures are adjusted dynamically during the curing period.At present,this method is already applied in raft foundation for 6 nuclear islands of different nuclear power plants,there are no obvious cracks on the concrete after stripping.This method has a bright future of application and popularizing.
2010, 40(1): 31-34,20.
doi: 10.13204/j.gyjz201001010
Abstract:
Chinese national industrial and commercial development in the modern times is basically along the canal flow path,thus leaving behind the coast cities many industrial inheritances which are worth protecting.As the material carriers of the industrial civilization of the area,industrial heritage has already obtained people's acknowledgement.From the analysis of the superiority and the condition in the industrial inheritance based on the analysis and summary of the work of industrial heritage protection and re-use in Wuxi,this article attempts to discuss the significance of industrial heritage re-use to urban memory accumulation and urban cultural revival.
Chinese national industrial and commercial development in the modern times is basically along the canal flow path,thus leaving behind the coast cities many industrial inheritances which are worth protecting.As the material carriers of the industrial civilization of the area,industrial heritage has already obtained people's acknowledgement.From the analysis of the superiority and the condition in the industrial inheritance based on the analysis and summary of the work of industrial heritage protection and re-use in Wuxi,this article attempts to discuss the significance of industrial heritage re-use to urban memory accumulation and urban cultural revival.
2010, 40(1): 35-38.
doi: 10.13204/j.gyjz201001011
Abstract:
With a wide use of multi-ribbed wall slab structure,it is very important to evaluate the reliability of in-service multi-ribbed wall slab structure,which can provide a scientific basis for expansion and reform of structures.The fundamental theory and assessment method on safety assessment of structures based on fuzzy-neural net work are researched in the paper.Which can evaluate the reliability of a real multi-ribbed wall slab structure by the improved model founded on fuzzy-neural network.The results indicate that the proposed means is viable and reasonable.
With a wide use of multi-ribbed wall slab structure,it is very important to evaluate the reliability of in-service multi-ribbed wall slab structure,which can provide a scientific basis for expansion and reform of structures.The fundamental theory and assessment method on safety assessment of structures based on fuzzy-neural net work are researched in the paper.Which can evaluate the reliability of a real multi-ribbed wall slab structure by the improved model founded on fuzzy-neural network.The results indicate that the proposed means is viable and reasonable.
2010, 40(1): 39-45.
doi: 10.13204/j.gyjz201001012
Abstract:
Six in-plane beam-thin wall joints were tested under reversed cyclic loading,considering various design parameters such as longitudinal bar's anchorage condition,stirrup reinforcement ratio of beam within the wall and beam height.Using the nonlinear FEM,numerical simulations of the test specimens and parametric analysis were performed.There is a good agreement between the numerical simulations and the test results.Given a certain straight anchorage length,both the 90-degree hooked anchorage of longitudinal bars and larger stirrup ratio of the beam within the wall can improve the carrying capacity and ductility of the joint,but the 90-degree hooked anchorage is better as far as the overall performance is concerned.The longitudinal bar's straight anchorage length is the basic guarantee of the effective force transmission.The carrying capacity,deformation and ductility of joint can be ensured with the rational stirrup ratio and anchoring method of the joint.
Six in-plane beam-thin wall joints were tested under reversed cyclic loading,considering various design parameters such as longitudinal bar's anchorage condition,stirrup reinforcement ratio of beam within the wall and beam height.Using the nonlinear FEM,numerical simulations of the test specimens and parametric analysis were performed.There is a good agreement between the numerical simulations and the test results.Given a certain straight anchorage length,both the 90-degree hooked anchorage of longitudinal bars and larger stirrup ratio of the beam within the wall can improve the carrying capacity and ductility of the joint,but the 90-degree hooked anchorage is better as far as the overall performance is concerned.The longitudinal bar's straight anchorage length is the basic guarantee of the effective force transmission.The carrying capacity,deformation and ductility of joint can be ensured with the rational stirrup ratio and anchoring method of the joint.
2010, 40(1): 46-50,72.
doi: 10.13204/j.gyjz201001013
Abstract:
Experimental research and theoretic analysis show that the webs of some joints with specially shaped columns exhibit severe failure under low cyclic loading,so the joint with specially shaped columns become the weak part of structures with specially shape columns,and it restricts the storey height of this structure.Based on the low cyclic loading of a exterior joint with specially shaped columns reinforced by polypropylene fiber at the core of the joint and a joint with specially shaped columns not reinforced,it is compared the failure characteristic,the bearing capacity and ductility,the hysteresis curve of the moment-rotation at end of beams of the two specimens;it is studied the change of the stirrup strain of the core of joints,and is also analyzed the cumulated damages with the damage estimating model.It is shown that fiber reinforced concrete could improve the failure characteristic and enhance the cracking load effectively of the joint with specially shaped columns,so the joint is never the weak part of structures with specially shape columns.
Experimental research and theoretic analysis show that the webs of some joints with specially shaped columns exhibit severe failure under low cyclic loading,so the joint with specially shaped columns become the weak part of structures with specially shape columns,and it restricts the storey height of this structure.Based on the low cyclic loading of a exterior joint with specially shaped columns reinforced by polypropylene fiber at the core of the joint and a joint with specially shaped columns not reinforced,it is compared the failure characteristic,the bearing capacity and ductility,the hysteresis curve of the moment-rotation at end of beams of the two specimens;it is studied the change of the stirrup strain of the core of joints,and is also analyzed the cumulated damages with the damage estimating model.It is shown that fiber reinforced concrete could improve the failure characteristic and enhance the cracking load effectively of the joint with specially shaped columns,so the joint is never the weak part of structures with specially shape columns.
2010, 40(1): 51-54.
doi: 10.13204/j.gyjz201001014
Abstract:
Frame-bent structure is the structural form that is frequently used in the main mill building of a thermal power plant,whose structural quality and rigidity are distributed non-uniformly.It is necessary to research earthquake resistant behavior of this structure.In order to achieve the performance of main building under rare earthquake,a time history response analysis is carried out.The result shows that the complete dynamic response process of the structure under seismic loads varying with time is showed with time history method.The frame-bent structure has many weak links,which merits attention during design of such structure.
Frame-bent structure is the structural form that is frequently used in the main mill building of a thermal power plant,whose structural quality and rigidity are distributed non-uniformly.It is necessary to research earthquake resistant behavior of this structure.In order to achieve the performance of main building under rare earthquake,a time history response analysis is carried out.The result shows that the complete dynamic response process of the structure under seismic loads varying with time is showed with time history method.The frame-bent structure has many weak links,which merits attention during design of such structure.
2010, 40(1): 55-58,101.
doi: 10.13204/j.gyjz201001015
Abstract:
By having an analysis of the existing optimization method,aiming at the defect of the easy convergence of the ant colony algorithm's local optimal solution,this paper presents an improved ant colony a algorithm.It could enhance the global optimization ablility of ant colony optimization by genetic algorithm and taboo search.Which could improve the flexibility and expansibility of the arithmetic.It is applied to a design of truss structures,thus building a corresponding model.At last,the study and analysis show that the improved ant colony algorithm is well-grounded on the easy optimization of a ten-bar plane truss.
By having an analysis of the existing optimization method,aiming at the defect of the easy convergence of the ant colony algorithm's local optimal solution,this paper presents an improved ant colony a algorithm.It could enhance the global optimization ablility of ant colony optimization by genetic algorithm and taboo search.Which could improve the flexibility and expansibility of the arithmetic.It is applied to a design of truss structures,thus building a corresponding model.At last,the study and analysis show that the improved ant colony algorithm is well-grounded on the easy optimization of a ten-bar plane truss.
2010, 40(1): 59-63.
doi: 10.13204/j.gyjz201001016
Abstract:
Based on the static loading experiment of four reinforced concrete floor slabs,two ordinary and two superimposed with connections,the paper studied their loading mechanism and bending performance,such as deformation,cracks,bearing capacity and fail modes.With the FEA program,ANSYS,adopted,the nonlinear numerical simulation of the slabs under the monotonous static load is done,and the corresponding results are compared with the experimental ones.Finally,proposals for superimposed slabs' design are put forward.
Based on the static loading experiment of four reinforced concrete floor slabs,two ordinary and two superimposed with connections,the paper studied their loading mechanism and bending performance,such as deformation,cracks,bearing capacity and fail modes.With the FEA program,ANSYS,adopted,the nonlinear numerical simulation of the slabs under the monotonous static load is done,and the corresponding results are compared with the experimental ones.Finally,proposals for superimposed slabs' design are put forward.
2010, 40(1): 64-67.
doi: 10.13204/j.gyjz201001017
Abstract:
The improvement of bearing capacity dependeds on three aspects of soil consolidation,disturb-restore property and shell-effect.The effect of soil consolidation is most important,so the law of time-effect is studied from this aspects of pore pressure dissipation and effective stress increase.By using the theory of spherical cavity expansion,imaging method and formula Henkel,the expression of stress increase after installation is deduced and the expression of pore pressure at any time by computing the equation of pore pressure and time,then stimulation computation method of bearing time-effect in saturated soil is presented.Comparing with test results,it is showed that the calculation is receivable.
The improvement of bearing capacity dependeds on three aspects of soil consolidation,disturb-restore property and shell-effect.The effect of soil consolidation is most important,so the law of time-effect is studied from this aspects of pore pressure dissipation and effective stress increase.By using the theory of spherical cavity expansion,imaging method and formula Henkel,the expression of stress increase after installation is deduced and the expression of pore pressure at any time by computing the equation of pore pressure and time,then stimulation computation method of bearing time-effect in saturated soil is presented.Comparing with test results,it is showed that the calculation is receivable.
2010, 40(1): 68-72.
doi: 10.13204/j.gyjz201001018
Abstract:
Flexural behavior is one of the most important qualifying index of prestressed high strength concrete (PHC) pipe pile.The calculation methods of cracking moment and ultimate failure moment of PHC pipe piles are based on the approaches in the Code for Design of Concrete Structures (GB 500102002) at present.In fact,the concrete strength grade of PHC pipe piles are beyond the adaptable scope of the GB 500102002 Code.The approaches in the code for estimating the cracking moments and ultimate failure moments of PHC pipe piles can not well match the actual bearing capacities.In this paper,combining with the analysis of the flexural experimental results and the behavior of centrifugal shaped producing method of PHC pipe piles,new approaches for calculating the cracking moment and ultimate failure moment of PHC pipe piles are proposed based on the present methods in the code.Comparing analysis shows that the calculation results by the modified methods are well agreed with the experimental results of PHC pipe piles.The suggested approaches for estimating the flexural capacities of PHC pipe piles are suitable in practice design.
Flexural behavior is one of the most important qualifying index of prestressed high strength concrete (PHC) pipe pile.The calculation methods of cracking moment and ultimate failure moment of PHC pipe piles are based on the approaches in the Code for Design of Concrete Structures (GB 500102002) at present.In fact,the concrete strength grade of PHC pipe piles are beyond the adaptable scope of the GB 500102002 Code.The approaches in the code for estimating the cracking moments and ultimate failure moments of PHC pipe piles can not well match the actual bearing capacities.In this paper,combining with the analysis of the flexural experimental results and the behavior of centrifugal shaped producing method of PHC pipe piles,new approaches for calculating the cracking moment and ultimate failure moment of PHC pipe piles are proposed based on the present methods in the code.Comparing analysis shows that the calculation results by the modified methods are well agreed with the experimental results of PHC pipe piles.The suggested approaches for estimating the flexural capacities of PHC pipe piles are suitable in practice design.
2010, 40(1): 73-77,115.
doi: 10.13204/j.gyjz201001019
Abstract:
The top-extended CFG pile composite foundation is a ground treatment technique based on CFG pile foundation.It can make full use of the load collecting function of top-extended piles,and the bearing capacity and the deformation compatibility of soil between piles,which takes advantage of the pile-platform-soil interaction.Taking a highway in Henan Province as the engineering background and study object.Common CFG pile and top-extended CFG-pile composite foundation were analyzed by finite element numerical method,and various factors to the effect on settlement-controlling were discussed.The vertical displacement of the soil under the pile cap were analyzed,and the changing law of stress along the pile and vertical stress of the soil under the pile cap were studied.According to the analysis of the on-site monitoring data,some useful conclusions of the numerical simulation of the top-extended CFG pile were obtained.
The top-extended CFG pile composite foundation is a ground treatment technique based on CFG pile foundation.It can make full use of the load collecting function of top-extended piles,and the bearing capacity and the deformation compatibility of soil between piles,which takes advantage of the pile-platform-soil interaction.Taking a highway in Henan Province as the engineering background and study object.Common CFG pile and top-extended CFG-pile composite foundation were analyzed by finite element numerical method,and various factors to the effect on settlement-controlling were discussed.The vertical displacement of the soil under the pile cap were analyzed,and the changing law of stress along the pile and vertical stress of the soil under the pile cap were studied.According to the analysis of the on-site monitoring data,some useful conclusions of the numerical simulation of the top-extended CFG pile were obtained.
2010, 40(1): 78-81,97.
doi: 10.13204/j.gyjz201001020
Abstract:
In this paper,based on the mechanical capacity of beams reinforced with steel fiber in torsion and taking account of the influence of the steel fiber,the formulas on ultimate torque of the beams are given using the variable angle space truss model.So that the formulas make the function of steel fibers as the equivalent longitude and transverse steel bars,which can joint well with the calculation formulas on ultimate torque of common reinforced concrete beams.Then the prediction results are compared with the results of the test,and the calculation precision of the formulas is high,Which can be used in practice.
In this paper,based on the mechanical capacity of beams reinforced with steel fiber in torsion and taking account of the influence of the steel fiber,the formulas on ultimate torque of the beams are given using the variable angle space truss model.So that the formulas make the function of steel fibers as the equivalent longitude and transverse steel bars,which can joint well with the calculation formulas on ultimate torque of common reinforced concrete beams.Then the prediction results are compared with the results of the test,and the calculation precision of the formulas is high,Which can be used in practice.
2010, 40(1): 82-86.
doi: 10.13204/j.gyjz201001021
Abstract:
The determination of minimum longitudinal reinforcement ratio of flexural concrete members in Code for Design of Concrete Structures (GB 500102002) is presented in this paper.And this paper compares the limit of the minimum longitudinal reinforcement ratio in Chinese concrete design criteria with other countries' criteria.The crack width of a bending member does not satisfy the criteria's limit requirement while minimum reinforcement satisfied through an engineering example.The paper suggests a new formula of the minimum reinforcement ratio,whose serviceability is taken into account to assure that the minimum reinforcement ratio is compatible with the crack control.
The determination of minimum longitudinal reinforcement ratio of flexural concrete members in Code for Design of Concrete Structures (GB 500102002) is presented in this paper.And this paper compares the limit of the minimum longitudinal reinforcement ratio in Chinese concrete design criteria with other countries' criteria.The crack width of a bending member does not satisfy the criteria's limit requirement while minimum reinforcement satisfied through an engineering example.The paper suggests a new formula of the minimum reinforcement ratio,whose serviceability is taken into account to assure that the minimum reinforcement ratio is compatible with the crack control.
2010, 40(1): 87-91.
doi: 10.13204/j.gyjz201001022
Abstract:
Frost damage appeared in concrete after freezing and thawing,its mass loss was increased,while ultrasonic velocity,compressive strength and splitting strength were decreased.With the increasing of freezing and thawing cycles,the bond strength between steel bar and concrete was decreased,and ultimate slippage at free end of the steel bar was increased.Based on the test results,the bond behavior was deteriorated after freezing and thawing,whose main reason was the decrease in concrete strength by damage of concrete due to freezing and thawing cycles.
Frost damage appeared in concrete after freezing and thawing,its mass loss was increased,while ultrasonic velocity,compressive strength and splitting strength were decreased.With the increasing of freezing and thawing cycles,the bond strength between steel bar and concrete was decreased,and ultimate slippage at free end of the steel bar was increased.Based on the test results,the bond behavior was deteriorated after freezing and thawing,whose main reason was the decrease in concrete strength by damage of concrete due to freezing and thawing cycles.
2010, 40(1): 92-97.
doi: 10.13204/j.gyjz201001023
Abstract:
To study the load transfer mechanism of bonded rebars including slip of two interfaces,the bonded rebars system of steel sleeve was studied by nonlinear FE analysis method.In the bonded rebars system of steel sleeve,because the material of steel sleeve is similar to the one of the steel bar,the bond performance between adhesive and steel bar is similar to the one between adhesive and steel sleeve,so that the bond-slip constitutive relationships of steel-adhesive interface and adhesive-sleeve interface are similar.Therefore,according to the bond-slip constitutive relationship including slip of two interfaces which was formed by the experimental research of steel sleeve,the respective and separate bond-slip constitutive relationships of two interfaces were formed by average division.Then by using these two constitutive relationships,the bonded rebars system of steel sleeve was studied by the FE analysis based on the ANSYS program considering slip of two interfaces.According to the analysis result,the bond-slip constitutive relationships of two interfaces are reasonable,and the load transfer mechanism of the bonded rebars system of steel sleeve is understood,which is the fundamental work in the further cognition of the load transfer mechanism of the bonded rebars system.
To study the load transfer mechanism of bonded rebars including slip of two interfaces,the bonded rebars system of steel sleeve was studied by nonlinear FE analysis method.In the bonded rebars system of steel sleeve,because the material of steel sleeve is similar to the one of the steel bar,the bond performance between adhesive and steel bar is similar to the one between adhesive and steel sleeve,so that the bond-slip constitutive relationships of steel-adhesive interface and adhesive-sleeve interface are similar.Therefore,according to the bond-slip constitutive relationship including slip of two interfaces which was formed by the experimental research of steel sleeve,the respective and separate bond-slip constitutive relationships of two interfaces were formed by average division.Then by using these two constitutive relationships,the bonded rebars system of steel sleeve was studied by the FE analysis based on the ANSYS program considering slip of two interfaces.According to the analysis result,the bond-slip constitutive relationships of two interfaces are reasonable,and the load transfer mechanism of the bonded rebars system of steel sleeve is understood,which is the fundamental work in the further cognition of the load transfer mechanism of the bonded rebars system.
2010, 40(1): 98-101.
doi: 10.13204/j.gyjz201001024
Abstract:
In recent years,the integrated ground anchorages technologies have been developed in our country,in order to adapt to the rapid development needs of the construction projects such as civil engineering,water conservancy and hydropower,mining and building.A series of achievements have been achieved on the load transfer mechanism,design,structures and grouting process and long term performance and safety assessment of ground anchors which updated our country's integrated ground anchorage technologies,and the level of ground anchorages engineering applications has entered the ranks of the advanced countries.This is mainly manifested in the following aspects:1)Developing the high-pressure regrouting anchor and jet grouting underreamed anchor,overcoming low capacity and large creep defects of ground anchors in soft soils and complex geotechnical conditions;2)Strengthening the studies of the load transfer mechanism of ground anchorage,proposing the coefficient factor of anchor bond length having effects on the bond strength,determining the reasonable bond length of ground anchor;3)Developing and using load dispersed anchor system(SMBA) widely,with the characteristics of the uniform of bond distribution,good anti-corrosion properties and higher load bearing capacities;4)Making progress obviously in the research on the long term performance and safety assessment of ground anchorage;5)Establishing our nation's ground anchorage standard systems;6)Expanding significantly the field and scale of the ground anchorage engineering applications.
In recent years,the integrated ground anchorages technologies have been developed in our country,in order to adapt to the rapid development needs of the construction projects such as civil engineering,water conservancy and hydropower,mining and building.A series of achievements have been achieved on the load transfer mechanism,design,structures and grouting process and long term performance and safety assessment of ground anchors which updated our country's integrated ground anchorage technologies,and the level of ground anchorages engineering applications has entered the ranks of the advanced countries.This is mainly manifested in the following aspects:1)Developing the high-pressure regrouting anchor and jet grouting underreamed anchor,overcoming low capacity and large creep defects of ground anchors in soft soils and complex geotechnical conditions;2)Strengthening the studies of the load transfer mechanism of ground anchorage,proposing the coefficient factor of anchor bond length having effects on the bond strength,determining the reasonable bond length of ground anchor;3)Developing and using load dispersed anchor system(SMBA) widely,with the characteristics of the uniform of bond distribution,good anti-corrosion properties and higher load bearing capacities;4)Making progress obviously in the research on the long term performance and safety assessment of ground anchorage;5)Establishing our nation's ground anchorage standard systems;6)Expanding significantly the field and scale of the ground anchorage engineering applications.
2010, 40(1): 102-106.
doi: 10.13204/j.gyjz201001025
Abstract:
In order to study the mechanical performance of internal stretch forming lattice structure (ISFL) being influenced by forming method,two methods one is tensioning group by group and the other is tensioning simultaneously step by step,were put forward.Based on the effect on structural moment of upper chord by tensioning method,the mechanical characteristic about structural moment distribution and comparison were fully analyzed by using ANSYS finite element program.The study shows that method tensioning group by group is a feasible program from the point of moment affected by tensioning method.On the forming process of ISFL,the moment is mainly distributed on the middle span,and well-proportioned along structural span.Additionally,it is important to reasonably select structural configuration of the middle of a ISFL.
In order to study the mechanical performance of internal stretch forming lattice structure (ISFL) being influenced by forming method,two methods one is tensioning group by group and the other is tensioning simultaneously step by step,were put forward.Based on the effect on structural moment of upper chord by tensioning method,the mechanical characteristic about structural moment distribution and comparison were fully analyzed by using ANSYS finite element program.The study shows that method tensioning group by group is a feasible program from the point of moment affected by tensioning method.On the forming process of ISFL,the moment is mainly distributed on the middle span,and well-proportioned along structural span.Additionally,it is important to reasonably select structural configuration of the middle of a ISFL.
2010, 40(1): 107-111,45.
doi: 10.13204/j.gyjz201001026
Abstract:
By ANSYS program analysis,stability capacity was computed for circular tube beam-columns under axial compressive force and various biaxial end-moments with different distributions.The comparison of numerical results with the interaction formula in current design code GB 500172003 shows relative big errors.An improvement is presented,and the proposed interaction formula can be applicabe with high accuracy.
By ANSYS program analysis,stability capacity was computed for circular tube beam-columns under axial compressive force and various biaxial end-moments with different distributions.The comparison of numerical results with the interaction formula in current design code GB 500172003 shows relative big errors.An improvement is presented,and the proposed interaction formula can be applicabe with high accuracy.
2010, 40(1): 112-115.
doi: 10.13204/j.gyjz201001027
Abstract:
Based on the results of axial compressive tests of lightweight aggregate concrete filled steel tube (LACFST) columns,the influence of slenderness ratio on failure mode and bearing capacity are studied.The bound slenderness ratio and stability factor calculation results of the empirical formula are compared with the test results.Analyses show that bound slenderness ratio as the demarcation of elastic-plastic damage and elastic damage mode can be calculated by Euler formula.The result of Euler formula is lower than that of the empirical formula.And the larger the slenderness ratio is,the lower the ultimate bearing capacity and stability factor are.
Based on the results of axial compressive tests of lightweight aggregate concrete filled steel tube (LACFST) columns,the influence of slenderness ratio on failure mode and bearing capacity are studied.The bound slenderness ratio and stability factor calculation results of the empirical formula are compared with the test results.Analyses show that bound slenderness ratio as the demarcation of elastic-plastic damage and elastic damage mode can be calculated by Euler formula.The result of Euler formula is lower than that of the empirical formula.And the larger the slenderness ratio is,the lower the ultimate bearing capacity and stability factor are.
2010, 40(1): 116-119,130.
doi: 10.13204/j.gyjz201001028
Abstract:
Through a basemen trebuilding and reinforcement project, this article introduced the application of Underpinning technique in a basement rebuilding project from theoretical analysis and engineering practice. First of all, this article disscussed the result of underpinning project, lift-up force and lift-up displacement in rebuilding design; then introduced application of ground treatment technology in this project; at last,evaluated the effect of the rebuilding project by localm onitoring of the structure displacement and sedimentation observation of building in later period.
Through a basemen trebuilding and reinforcement project, this article introduced the application of Underpinning technique in a basement rebuilding project from theoretical analysis and engineering practice. First of all, this article disscussed the result of underpinning project, lift-up force and lift-up displacement in rebuilding design; then introduced application of ground treatment technology in this project; at last,evaluated the effect of the rebuilding project by localm onitoring of the structure displacement and sedimentation observation of building in later period.
2010, 40(1): 120-123.
doi: 10.13204/j.gyjz201001029
Abstract:
Through a basement rebuilding and reinforcement project,this article introduced the application of Underpinning technique in a basement rebuilding project from theoretical analysis and engineering practice.First of all,this article disscussed the result of underpinning project,lift-up force and lift-up displacement in rebuilding design;then introduced application of ground treatment technology in this project;at last,evaluated the effect of the rebuilding project by local monitoring of the structure displacement and sedimentation observation of building in later period.
Through a basement rebuilding and reinforcement project,this article introduced the application of Underpinning technique in a basement rebuilding project from theoretical analysis and engineering practice.First of all,this article disscussed the result of underpinning project,lift-up force and lift-up displacement in rebuilding design;then introduced application of ground treatment technology in this project;at last,evaluated the effect of the rebuilding project by local monitoring of the structure displacement and sedimentation observation of building in later period.
2010, 40(1): 124-126.
doi: 10.13204/j.gyjz201001030
Abstract:
A theoretical exploration discussion of the architectural style is done by actual analysis of design of a factory building,and a typical form of elevation of a factory building is formed.At the same time,a special design method of wall construction is introduced,and discussed deeply the firefighting connection between main factory building and circumjacent auxiliary buildings.Which will provide a guidance and reference for design of industrial buildings.
A theoretical exploration discussion of the architectural style is done by actual analysis of design of a factory building,and a typical form of elevation of a factory building is formed.At the same time,a special design method of wall construction is introduced,and discussed deeply the firefighting connection between main factory building and circumjacent auxiliary buildings.Which will provide a guidance and reference for design of industrial buildings.
2010, 40(1): 127-130.
doi: 10.13204/j.gyjz201001031
Abstract:
By discussing the functional sub area,organizing form and feature,it is analyzed the necessity and the problems of the detailed design of small apartments.Besides,on the purpose of consummating function,converting negative room to positive space and enhancing the multifunctional use,taking the instance of the improved detailed design of small apartments,the design idea of 'multifunctional housework area' is also proposed.
By discussing the functional sub area,organizing form and feature,it is analyzed the necessity and the problems of the detailed design of small apartments.Besides,on the purpose of consummating function,converting negative room to positive space and enhancing the multifunctional use,taking the instance of the improved detailed design of small apartments,the design idea of 'multifunctional housework area' is also proposed.
2010, 40(1): 131-134.
doi: 10.13204/j.gyjz201001032
Abstract:
Although here are same regionalism crises faced by both China and Latin America,the architects in this area had not been noticed by most of us.Many of them became famous in China these years just because of their awards in some world-class elections.But in fact,after referring Latin American architecture history,it can be found out that the efforts of those architects and the advances they have made in regionalism architecture design have gone far beyond our imagination.The only purpose of this article is to introduce these architects and their works by classifying and summarizing,for our learning,using and studying.
Although here are same regionalism crises faced by both China and Latin America,the architects in this area had not been noticed by most of us.Many of them became famous in China these years just because of their awards in some world-class elections.But in fact,after referring Latin American architecture history,it can be found out that the efforts of those architects and the advances they have made in regionalism architecture design have gone far beyond our imagination.The only purpose of this article is to introduce these architects and their works by classifying and summarizing,for our learning,using and studying.
