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2011 Vol. 41, No. 1
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2011, 41(1): 1-5,36.
doi: 10.13204/j.gyjz201101001
Abstract:
For application purposes,based on the existing research results and experimental analysis and engineering experience,it was analyzed the high formwork support inner properties,lateral stability of single upright stanchion and the entire system.Hierarchical design,selecting the hinged framework support calculation model,calculated according to the actual load were put forward.The material coefficient impacted by the initial flaw and the importance coefficient of structures were presented.Its also proposed safety strategies,such as construction of invariable structure system of geometric member by building rigid unit structure and rigid layer and the rigid surface,promoting acceptance qualification certificate systems,retaining redundant degree security and improving high formwork supporting system etc.
For application purposes,based on the existing research results and experimental analysis and engineering experience,it was analyzed the high formwork support inner properties,lateral stability of single upright stanchion and the entire system.Hierarchical design,selecting the hinged framework support calculation model,calculated according to the actual load were put forward.The material coefficient impacted by the initial flaw and the importance coefficient of structures were presented.Its also proposed safety strategies,such as construction of invariable structure system of geometric member by building rigid unit structure and rigid layer and the rigid surface,promoting acceptance qualification certificate systems,retaining redundant degree security and improving high formwork supporting system etc.
2011, 41(1): 6-10,32.
doi: 10.13204/j.gyjz201101002
Abstract:
Design and calculation methods of integral-lift scaffolds were comprehensively discussed in the paper.Design and calculation of integral-lift scaffolds included the main structures and the lifting equipments under the three cases such as working,lifting and falling.In the paper,some key factors such as partial safety factors and additional load factors in the basic limit state designing expressions based on probability theory were listed for recommendation.The strength,rigidity and stability checking computation methods were also given for the main structures of the integral-lift scaffolds,of which the differences between scaffold frame structures and other main structures were also discussed.The allowable stress method was also suggested for design and calculation of lifting equipments,suspend rod and sling.
Design and calculation methods of integral-lift scaffolds were comprehensively discussed in the paper.Design and calculation of integral-lift scaffolds included the main structures and the lifting equipments under the three cases such as working,lifting and falling.In the paper,some key factors such as partial safety factors and additional load factors in the basic limit state designing expressions based on probability theory were listed for recommendation.The strength,rigidity and stability checking computation methods were also given for the main structures of the integral-lift scaffolds,of which the differences between scaffold frame structures and other main structures were also discussed.The allowable stress method was also suggested for design and calculation of lifting equipments,suspend rod and sling.
2011, 41(1): 11-14,18.
doi: 10.13204/j.gyjz201101003
Abstract:
In the calculation of stability bearing capacity of scaffold steel tubes,the stability factor of axial compression members mostly still uses the value in the GB 500182002Technical Code of Cold-Formed Thin-Wall Steel Structures.The data show that there are some gaps and differences between the scaffold and GB 500182002 in the calculations,such as,the imperfections and the cross-section.The paper analyzed the stability factor values of domestic and oversea related codes,in accordance with the integrated imperfections standard mathematical model,it is considered the section properties and the actual geometric imperfections of pipe 48 3.5 and it is proposed revisions to the stability factor value.According to the measured structural stability bearing capacity,it was also studied the original curve and the stability factor;and recommended stability factor value were given.
In the calculation of stability bearing capacity of scaffold steel tubes,the stability factor of axial compression members mostly still uses the value in the GB 500182002Technical Code of Cold-Formed Thin-Wall Steel Structures.The data show that there are some gaps and differences between the scaffold and GB 500182002 in the calculations,such as,the imperfections and the cross-section.The paper analyzed the stability factor values of domestic and oversea related codes,in accordance with the integrated imperfections standard mathematical model,it is considered the section properties and the actual geometric imperfections of pipe 48 3.5 and it is proposed revisions to the stability factor value.According to the measured structural stability bearing capacity,it was also studied the original curve and the stability factor;and recommended stability factor value were given.
2011, 41(1): 15-18.
doi: 10.13204/j.gyjz201101004
Abstract:
According to actual construction detection,inspecting the variation of axial force of the strut is a effectual method for insuring safety of high form strut system of formwork.Based on an on-site detection experiment of a projects high form strut system,this article studied about the following elements that the periodic shock effect of pump pipe,the vibration effect of vibrated rods and pouring line during concrete construction in what extent affected the axial force to the formwork support.Finally,it revealed how much the vibrated rods influenced formwork support and the interaction of dynamic axial force and the static axial force of the formwork support.
According to actual construction detection,inspecting the variation of axial force of the strut is a effectual method for insuring safety of high form strut system of formwork.Based on an on-site detection experiment of a projects high form strut system,this article studied about the following elements that the periodic shock effect of pump pipe,the vibration effect of vibrated rods and pouring line during concrete construction in what extent affected the axial force to the formwork support.Finally,it revealed how much the vibrated rods influenced formwork support and the interaction of dynamic axial force and the static axial force of the formwork support.
2011, 41(1): 19-22.
doi: 10.13204/j.gyjz201101005
Abstract:
In China and even world-wide,the method of statics is often use statics point of view to design the formwork support system,which is one of the important factors that leads to collapse of high formwork construction.In order to reflect the real condition of the structure,it requires dynamics rather than statics to design and analyse.Through transient dynamics of the finite element,the mode of high formwork under freely falling shocking was simulated.The displacement and stress of static and dynamic were obtained.Compared with the theoretical method,it was verified the relationship between the coefficient of freely falling chocking and the falling height.
In China and even world-wide,the method of statics is often use statics point of view to design the formwork support system,which is one of the important factors that leads to collapse of high formwork construction.In order to reflect the real condition of the structure,it requires dynamics rather than statics to design and analyse.Through transient dynamics of the finite element,the mode of high formwork under freely falling shocking was simulated.The displacement and stress of static and dynamic were obtained.Compared with the theoretical method,it was verified the relationship between the coefficient of freely falling chocking and the falling height.
2011, 41(1): 23-25.
doi: 10.13204/j.gyjz201101006
Abstract:
The paper constructed the model of the Tube and Couple Scaffold(TCS) system about projects by investigating the spot and making use of SAP 2000 finite element analysis software,and obtained an optimization scheme which erected lateral bracing through researching it.At the same time,the paper also considered how vertical distance,horizontal distance and step effected the stability bearing capacity when they were changed.At last,the paper proposed a new suggestion to further optimize that scheme.
The paper constructed the model of the Tube and Couple Scaffold(TCS) system about projects by investigating the spot and making use of SAP 2000 finite element analysis software,and obtained an optimization scheme which erected lateral bracing through researching it.At the same time,the paper also considered how vertical distance,horizontal distance and step effected the stability bearing capacity when they were changed.At last,the paper proposed a new suggestion to further optimize that scheme.
2011, 41(1): 26-28,56.
doi: 10.13204/j.gyjz201101007
Abstract:
Attached self-lifting scaffolds are widely used in construction of high buildings.Machine position load will re-distributed when attached lifting scaffolding are lifted asynchronously,some members or some machine parts will be overloaded and form incipient faults.A study on measuring the rotational speed of motor was introduced in this paper,which calculated the lifting length difference by detecting the rotational number of motor and then synchronous lifting and declining solution of different machine position were achieved.Based on the principle,the synchronous device was designed using AT89C52 micro chip computer.The operational result shows that attached self-lifting scaffolds can run synchronously with this device.
Attached self-lifting scaffolds are widely used in construction of high buildings.Machine position load will re-distributed when attached lifting scaffolding are lifted asynchronously,some members or some machine parts will be overloaded and form incipient faults.A study on measuring the rotational speed of motor was introduced in this paper,which calculated the lifting length difference by detecting the rotational number of motor and then synchronous lifting and declining solution of different machine position were achieved.Based on the principle,the synchronous device was designed using AT89C52 micro chip computer.The operational result shows that attached self-lifting scaffolds can run synchronously with this device.
CONSTRUCTION TECHNIQUE OF VARIABLE FORMWORK FOR YICHANG WASTE WATER TREATMENT DIGESTION TANK PROJECT
2011, 41(1): 29-32.
doi: 10.13204/j.gyjz201101008
Abstract:
In view of the characteristic of hyperboloid structure of digestion tank space,formwork system,which consists of adjustable steel formwork unit,annular thread steel bars back support,radioactive amplitude bar rack,new type counterpulling bolt bar,can be used for construction of hyperboloid concrete structure.The said system can adapt to the section variation of any elevation and has the advantages of easy processing,simple assembly and repeated usage,efficient installation,precise formation of concrete and having even good looking in external shape,which can resolve the difficulty in the construction of abnormity structure formwork,increase working efficiency and reduce the cost.The formed concrete is condense internally and smooth in external shape,the indexes of various performances meet the requirements of design.
In view of the characteristic of hyperboloid structure of digestion tank space,formwork system,which consists of adjustable steel formwork unit,annular thread steel bars back support,radioactive amplitude bar rack,new type counterpulling bolt bar,can be used for construction of hyperboloid concrete structure.The said system can adapt to the section variation of any elevation and has the advantages of easy processing,simple assembly and repeated usage,efficient installation,precise formation of concrete and having even good looking in external shape,which can resolve the difficulty in the construction of abnormity structure formwork,increase working efficiency and reduce the cost.The formed concrete is condense internally and smooth in external shape,the indexes of various performances meet the requirements of design.
2011, 41(1): 33-36.
doi: 10.13204/j.gyjz201101009
Abstract:
In the construction of the Pudong New Library project,a new type formwork system,which was the columnar formwork made by paper,was used in construction of fair-faced concrete column.The paper columnar formwork was wrapped by multilayer special water-proof complex papers.Its diameter and height could be customized,so it neednt be connected in the field.The deadweight of paper column formwork was so light that the requirement for hoisting machine was low.The self-stiffness of the paper columnar formwork could satisfy the side pressure forming in concrete filling.Three locating hoops were used for the columnar formwork to measure the uprightness,so that it was easy to install and dismantle the formwork.In the same project,the paper columnar formwork was more preponderant than general formwork in environment protection,quality control,construction management and economic benefit,etc.
In the construction of the Pudong New Library project,a new type formwork system,which was the columnar formwork made by paper,was used in construction of fair-faced concrete column.The paper columnar formwork was wrapped by multilayer special water-proof complex papers.Its diameter and height could be customized,so it neednt be connected in the field.The deadweight of paper column formwork was so light that the requirement for hoisting machine was low.The self-stiffness of the paper columnar formwork could satisfy the side pressure forming in concrete filling.Three locating hoops were used for the columnar formwork to measure the uprightness,so that it was easy to install and dismantle the formwork.In the same project,the paper columnar formwork was more preponderant than general formwork in environment protection,quality control,construction management and economic benefit,etc.
2011, 41(1): 37-40.
doi: 10.13204/j.gyjz201101010
Abstract:
In order to prevent more casualty and loss in scaffold accidents in China,this paper mainly analyzed the problems of engineering construction and scaffold industry in China.Taking major scaffold accidents occurred in China for example,the paper also compared different scaffold production techniques and management experiences with developed countries.Furthermore,the paper suggested some solutions to help solve the scaffold problems in China: 1) to use new types of scaffolds with better security performance to replace those outdated fastener scaffolds with lager market share but poorer security performance;2) to establish a proper and efficient supervision system in the field of scaffold industry;3) to set up a fair and square scaffold leasing market;4) to found several large scale enterprises specializing in scaffold making and developing;5) to establish an effective security training system;6) to cultivate and enhance the sense of security of engineering personnel.
In order to prevent more casualty and loss in scaffold accidents in China,this paper mainly analyzed the problems of engineering construction and scaffold industry in China.Taking major scaffold accidents occurred in China for example,the paper also compared different scaffold production techniques and management experiences with developed countries.Furthermore,the paper suggested some solutions to help solve the scaffold problems in China: 1) to use new types of scaffolds with better security performance to replace those outdated fastener scaffolds with lager market share but poorer security performance;2) to establish a proper and efficient supervision system in the field of scaffold industry;3) to set up a fair and square scaffold leasing market;4) to found several large scale enterprises specializing in scaffold making and developing;5) to establish an effective security training system;6) to cultivate and enhance the sense of security of engineering personnel.
2011, 41(1): 41-43,67.
doi: 10.13204/j.gyjz201101011
Abstract:
This paper described connotation of the scientific development concept,it was analyzed the experiences and lessons of the western developed countries in the process of urban development and also analyzed the issues that appeared in Chinas current urban development,such as the old concept,waste of resources,overexpansion,ecological degradation,characteristics loss,as well as the neglect ofscience humanand so on.It was believed that scientific concept of development was an effective response to these problems,which was also the guiding ideology of the new era of urban development.Further more,It was proposed measures and methods of implementing the scientific concept of development in the urban development.
This paper described connotation of the scientific development concept,it was analyzed the experiences and lessons of the western developed countries in the process of urban development and also analyzed the issues that appeared in Chinas current urban development,such as the old concept,waste of resources,overexpansion,ecological degradation,characteristics loss,as well as the neglect ofscience humanand so on.It was believed that scientific concept of development was an effective response to these problems,which was also the guiding ideology of the new era of urban development.Further more,It was proposed measures and methods of implementing the scientific concept of development in the urban development.
2011, 41(1): 44-46,50.
doi: 10.13204/j.gyjz201101012
Abstract:
Taking an existing public building energy efficiency retrofit for example,compared the annual electricity consumption and the electricity consumption for each item before and after retrofit;and the energy efficiency effects corresponding to the different energy efficiency retrofit measures were analyzed.Through the temperature measurement,the indoor thermal environment affected by the building envelope energy efficiency retrofit was analyzed.The research results can offer the direction and emphasis for the existing public building energy efficiency retrofit in the hot summer and cold winter area.
Taking an existing public building energy efficiency retrofit for example,compared the annual electricity consumption and the electricity consumption for each item before and after retrofit;and the energy efficiency effects corresponding to the different energy efficiency retrofit measures were analyzed.Through the temperature measurement,the indoor thermal environment affected by the building envelope energy efficiency retrofit was analyzed.The research results can offer the direction and emphasis for the existing public building energy efficiency retrofit in the hot summer and cold winter area.
2011, 41(1): 47-50.
doi: 10.13204/j.gyjz201101013
Abstract:
It was analysed the problem of lacking of design direction and those of human life including social,ecological and resource issues and so on.It was also proposed strategies for the prevention and cope with to the crisis of public space caused by the urbanization,so as to make provision for the realization of urbanization era,which provided the basis for research and design.
It was analysed the problem of lacking of design direction and those of human life including social,ecological and resource issues and so on.It was also proposed strategies for the prevention and cope with to the crisis of public space caused by the urbanization,so as to make provision for the realization of urbanization era,which provided the basis for research and design.
2011, 41(1): 51-56.
doi: 10.13204/j.gyjz201101014
Abstract:
In the procedure of modal pushover analysis,non-linear time-history analysis is not so operative and its analytical result is unstable,the capacity-spectrum theory is used to take the place of dynamic time-history anslysis.Converting the acceleration response spectrum of current code into displacement response spectrum,the displacement response of equivalent single degree of freedom in each mode of vibration can be calculated by capacity spectrum method.Then the displacement response of multi-degree of freedom can be obtained too,and it is used to compare with the corresponding displacement(storey drift ratio) limits,judging whether the structure satisfies its performance objective or not.The proposed method improves the modal pushover analysisoperation and stability.
In the procedure of modal pushover analysis,non-linear time-history analysis is not so operative and its analytical result is unstable,the capacity-spectrum theory is used to take the place of dynamic time-history anslysis.Converting the acceleration response spectrum of current code into displacement response spectrum,the displacement response of equivalent single degree of freedom in each mode of vibration can be calculated by capacity spectrum method.Then the displacement response of multi-degree of freedom can be obtained too,and it is used to compare with the corresponding displacement(storey drift ratio) limits,judging whether the structure satisfies its performance objective or not.The proposed method improves the modal pushover analysisoperation and stability.
2011, 41(1): 57-63.
doi: 10.13204/j.gyjz201101015
Abstract:
Firstly,the face-to-face central impact experiments with 30 couples of concrete cubic blocks were performed using a pendulum test system and a drop weight test system.Then the experimental processes were recurred by the finite element code LS-DYNA,and the extended and the supplementary numerical tests for face-to-face central impact were carried out respectively.Furthermore,the numerical tests for face-to-face noncentral,line-to-face,point-to-face,line-to-line impacts and the numerical tests that were to study the influence of the shape of concrete blocks were performed.In the end,the models describing the behavior of the different impact modes between concrete blocks were derived from the results of the physical and the numerical tests,by means of the multiple nonlinear regression analysis.
Firstly,the face-to-face central impact experiments with 30 couples of concrete cubic blocks were performed using a pendulum test system and a drop weight test system.Then the experimental processes were recurred by the finite element code LS-DYNA,and the extended and the supplementary numerical tests for face-to-face central impact were carried out respectively.Furthermore,the numerical tests for face-to-face noncentral,line-to-face,point-to-face,line-to-line impacts and the numerical tests that were to study the influence of the shape of concrete blocks were performed.In the end,the models describing the behavior of the different impact modes between concrete blocks were derived from the results of the physical and the numerical tests,by means of the multiple nonlinear regression analysis.
2011, 41(1): 64-67.
doi: 10.13204/j.gyjz201101016
Abstract:
The oblique match-beams are the vital supporting members in a new-type full precast concrete frame structure.In order to obtain the ultimate bearing capacity of oblique match-beams with rigid scarf joint,various failure modes were analyzed with shear-friction theory and strut-and-tie model method,and corresponding design formulas for the ultimate strength were deduced.At last,through the existing experimental data,theoretical calculations on the bearing capacity of the oblique match-beams were verified.The results show that the ultimate bearing capacity formula with high accuracy.
The oblique match-beams are the vital supporting members in a new-type full precast concrete frame structure.In order to obtain the ultimate bearing capacity of oblique match-beams with rigid scarf joint,various failure modes were analyzed with shear-friction theory and strut-and-tie model method,and corresponding design formulas for the ultimate strength were deduced.At last,through the existing experimental data,theoretical calculations on the bearing capacity of the oblique match-beams were verified.The results show that the ultimate bearing capacity formula with high accuracy.
2011, 41(1): 68-72.
doi: 10.13204/j.gyjz201101017
Abstract:
Based on the ACI 209 method for predicting the creep and shrinkage of concrete,a study was conducted using age-adjusted effective modulus method to evaluate the deformation and stress redistribution of the long-term axially loaded concrete columns reinforced with concrete filled steel tube(CCRST),which was an ordinary reinforced-concrete column where there was a steel tube designed to be put in the core additionally.In addition,it was also examined the influence of different parameters,such as the age at first loading,the magnitude of loading and the area ratio of steel to gross section on the deformation and stress redistribution of the axially loaded CCRST columns.The analysis indicates that the deformation caused by the creep and shrinkage develops quickly in the early loading phase(within 4 or 5 months after loading),and the results of the stress redistribution will lead to a remarkable increase of the stress in steel tube.
Based on the ACI 209 method for predicting the creep and shrinkage of concrete,a study was conducted using age-adjusted effective modulus method to evaluate the deformation and stress redistribution of the long-term axially loaded concrete columns reinforced with concrete filled steel tube(CCRST),which was an ordinary reinforced-concrete column where there was a steel tube designed to be put in the core additionally.In addition,it was also examined the influence of different parameters,such as the age at first loading,the magnitude of loading and the area ratio of steel to gross section on the deformation and stress redistribution of the axially loaded CCRST columns.The analysis indicates that the deformation caused by the creep and shrinkage develops quickly in the early loading phase(within 4 or 5 months after loading),and the results of the stress redistribution will lead to a remarkable increase of the stress in steel tube.
2011, 41(1): 73-76,92.
doi: 10.13204/j.gyjz201101018
Abstract:
In this paper,a new kind of prestressed precast hybrid coupled wall(PPHSW) was proposed.Study was carried out with a computer program developed based on th finite element DRAIN-2DX.The results indicated that tension order has nothing to do with the axial force in coupling beams,but the value is less in the frist story coupling beam because of the fixed end in the bottom of the pier,the restraint effect of the fixed end is decayed quickly.Structure has good earthquake resistant behavior,with lateral displacement curve of shear-flexural type,in order to delay the state of yielding of prestressed tendons in coupling beams as much as posssible;throughout the process of loading the degree of coupling basically unchanged,the value should not be too large.
In this paper,a new kind of prestressed precast hybrid coupled wall(PPHSW) was proposed.Study was carried out with a computer program developed based on th finite element DRAIN-2DX.The results indicated that tension order has nothing to do with the axial force in coupling beams,but the value is less in the frist story coupling beam because of the fixed end in the bottom of the pier,the restraint effect of the fixed end is decayed quickly.Structure has good earthquake resistant behavior,with lateral displacement curve of shear-flexural type,in order to delay the state of yielding of prestressed tendons in coupling beams as much as posssible;throughout the process of loading the degree of coupling basically unchanged,the value should not be too large.
2011, 41(1): 77-81,85.
doi: 10.13204/j.gyjz201101019
Abstract:
Aimed at grasping the deformation properties of soft rock in the Three Gorges Reservoir Area,a study on the creep properties of T2 b2 purple siltite in different moisture state was carried out.The fresh T2 b2 siltite for test was collected from Taoshuya tunnel site,and through uniaxial creep test of T2 b2 siltite in four kinds of moisture states,uniaxial strain-time curves of under 5 load levels in different moisture states were got,based on which some basic creep features and laws of the siltite with the changes of stress level and moisture state were presented.The results show that in any moisture state,initial instantaneous strain and strain caused by creep effect increases are both increase with the growth of stress level,and the strain rate in the stable creep stage is transformed from zero to non-zero constant with the growth of stress level;in the condition of being in same stress level and different moisture state,the time for entering the stable creep phase under the same stress level becomes longer with the growth of the water content of rock sample,the instantaneous strain and total strain are also increased with the growth of the water content of rock sample,but the long-term strength of it has a decreasing trend.
Aimed at grasping the deformation properties of soft rock in the Three Gorges Reservoir Area,a study on the creep properties of T2 b2 purple siltite in different moisture state was carried out.The fresh T2 b2 siltite for test was collected from Taoshuya tunnel site,and through uniaxial creep test of T2 b2 siltite in four kinds of moisture states,uniaxial strain-time curves of under 5 load levels in different moisture states were got,based on which some basic creep features and laws of the siltite with the changes of stress level and moisture state were presented.The results show that in any moisture state,initial instantaneous strain and strain caused by creep effect increases are both increase with the growth of stress level,and the strain rate in the stable creep stage is transformed from zero to non-zero constant with the growth of stress level;in the condition of being in same stress level and different moisture state,the time for entering the stable creep phase under the same stress level becomes longer with the growth of the water content of rock sample,the instantaneous strain and total strain are also increased with the growth of the water content of rock sample,but the long-term strength of it has a decreasing trend.
2011, 41(1): 82-85.
doi: 10.13204/j.gyjz201101020
Abstract:
Creep deformation of undisturbed and reconstituted clay was studied based on drained triaxial compression tests.Creep tests were performed several times during monotonic primary loading,unloading and reloading.Test results show:1) the creep deformation of clay is related to the type of clay;2) the deformation of clay creep is related to strain rate is before creep,the larger strain rate,the greater the amount of creep;3) the deformation of clay creep is related to the stress level,as creep stress maintaining higher,the amount of clay creep is larger;and 4) in reloading progress,as stress level increases,the creep of clay show the negative creep,neutral creep to positive creep gradually being transformed.
Creep deformation of undisturbed and reconstituted clay was studied based on drained triaxial compression tests.Creep tests were performed several times during monotonic primary loading,unloading and reloading.Test results show:1) the creep deformation of clay is related to the type of clay;2) the deformation of clay creep is related to strain rate is before creep,the larger strain rate,the greater the amount of creep;3) the deformation of clay creep is related to the stress level,as creep stress maintaining higher,the amount of clay creep is larger;and 4) in reloading progress,as stress level increases,the creep of clay show the negative creep,neutral creep to positive creep gradually being transformed.
2011, 41(1): 86-92.
doi: 10.13204/j.gyjz201101021
Abstract:
Liuyanghe Tunnel is the first shallow,small spacing underwater road tunnel by mining method in China,bench cut method was adopted and circular section steel frame was used as one of primary support measures in construction.The loading state of the arch frame is one of the key factors to be controlled to the stability of the support system.The stress and displacement of the arch frame were measured on site,and based on the massive measured data,the mechanical behavior of section steel frame was analyzed.The research shows that the stress is larger in vault and invert bottom;the stress is changed due to lower bench excavation,pouring concrete at inverted arch and secondary lining,the local stress for section steel frame of the ahead tunnel chamber is increased because of the laggard chamber excavation;the arch frame stress change is related to time-space effect and river water permeability.The test results of stress and displacement show that the bench length is reasonable.
Liuyanghe Tunnel is the first shallow,small spacing underwater road tunnel by mining method in China,bench cut method was adopted and circular section steel frame was used as one of primary support measures in construction.The loading state of the arch frame is one of the key factors to be controlled to the stability of the support system.The stress and displacement of the arch frame were measured on site,and based on the massive measured data,the mechanical behavior of section steel frame was analyzed.The research shows that the stress is larger in vault and invert bottom;the stress is changed due to lower bench excavation,pouring concrete at inverted arch and secondary lining,the local stress for section steel frame of the ahead tunnel chamber is increased because of the laggard chamber excavation;the arch frame stress change is related to time-space effect and river water permeability.The test results of stress and displacement show that the bench length is reasonable.
2011, 41(1): 93-96,138.
doi: 10.13204/j.gyjz201101022
Abstract:
Micropiles commonly use pressure grouting method,which influences the uplift capacity of micropiles.In this paper,field tests about influence of pressure grouting on uplift capacity of micropiles were reported.Study shows that the uplift capacity of primary grouted micropiles is almost the same as the uplift capacity of concrete micropiles.However the uplift capacity of secondary grouted micropiles is enhanced.Increasing the amount of the second-grouting properly can help micropiles enhance the uplift capacity.Calculating the uplift capacity of secondary grouted micropiles must consider the effect of the second-grouting.
Micropiles commonly use pressure grouting method,which influences the uplift capacity of micropiles.In this paper,field tests about influence of pressure grouting on uplift capacity of micropiles were reported.Study shows that the uplift capacity of primary grouted micropiles is almost the same as the uplift capacity of concrete micropiles.However the uplift capacity of secondary grouted micropiles is enhanced.Increasing the amount of the second-grouting properly can help micropiles enhance the uplift capacity.Calculating the uplift capacity of secondary grouted micropiles must consider the effect of the second-grouting.
2011, 41(1): 97-100,129.
doi: 10.13204/j.gyjz201101023
Abstract:
Six self-compacting concrete beams and two corresponding ordinary concrete beams of two different strength grades were used to study anti-bending properties of concrete freely supported beams.The results show: 1)the mean of the experimental data of ultimate load of self-compacting concrete beams is close to that of corresponding ordinary concrete beams,and is higher than its theoretical value;2) the loading-deflection curves,the crack development and the failure mode of the two kinds of beams are basically the same;3) the average strain along section height of self-compacting concrete beams can fit with the assumption of plane section basically.Therefore,it is reasonable and safe to design the self-compacting concrete beams according to the theory of ordinary concrete.
Six self-compacting concrete beams and two corresponding ordinary concrete beams of two different strength grades were used to study anti-bending properties of concrete freely supported beams.The results show: 1)the mean of the experimental data of ultimate load of self-compacting concrete beams is close to that of corresponding ordinary concrete beams,and is higher than its theoretical value;2) the loading-deflection curves,the crack development and the failure mode of the two kinds of beams are basically the same;3) the average strain along section height of self-compacting concrete beams can fit with the assumption of plane section basically.Therefore,it is reasonable and safe to design the self-compacting concrete beams according to the theory of ordinary concrete.
2011, 41(1): 101-104,119.
doi: 10.13204/j.gyjz201101024
Abstract:
Through the compressive experiments on the cubic and prismatic specimens respectively,the influences of temperature,slag powder content,steel fiber volume ratio,polypropylene fiber content and concrete strength grade on compressive strength after high temperature were analyzed.The results show that the cubic and prismatic compressive strength of the fiber reinforced concrete with slag powder reduces along with the rising of temperature,and the cube compressive strength is close to the axial compressive strength gradually.Furthermore,the cubic and prismatic compressive strength of fiber reinforced concrete with slag powder increases with the increasing of slag powder content,steel fiber volume ratio and polypropylene fiber content after the action of high temperature;but the rates of increase are not different.
Through the compressive experiments on the cubic and prismatic specimens respectively,the influences of temperature,slag powder content,steel fiber volume ratio,polypropylene fiber content and concrete strength grade on compressive strength after high temperature were analyzed.The results show that the cubic and prismatic compressive strength of the fiber reinforced concrete with slag powder reduces along with the rising of temperature,and the cube compressive strength is close to the axial compressive strength gradually.Furthermore,the cubic and prismatic compressive strength of fiber reinforced concrete with slag powder increases with the increasing of slag powder content,steel fiber volume ratio and polypropylene fiber content after the action of high temperature;but the rates of increase are not different.
2011, 41(1): 105-111.
doi: 10.13204/j.gyjz201101025
Abstract:
This paper described the research status on durability of post-tensioned concrete both at home bridges domestic and abroad.It analysed the reasons of corrosions of bridges and works out some available measures for durability.To improve the durability of bridges,it was important on design,construction,and maintenance.It also introduced some techniques of non-destructive test and monitoring systems which had better applicability.It also puts forward some suggestions on the problems of durability of post-tensioned eoncrete bridges in the future.
This paper described the research status on durability of post-tensioned concrete both at home bridges domestic and abroad.It analysed the reasons of corrosions of bridges and works out some available measures for durability.To improve the durability of bridges,it was important on design,construction,and maintenance.It also introduced some techniques of non-destructive test and monitoring systems which had better applicability.It also puts forward some suggestions on the problems of durability of post-tensioned eoncrete bridges in the future.
2011, 41(1): 111-119.
doi: 10.13204/j.gyjz201101026
Abstract:
Reduced beam section connection(RBS) can make plastic hinge away from the beam and column interface,improve ductility of the structure and reach the purpose of seismic design of the connections.Element stiffness matrix and rotational displacement equation of the beam with RBS were derived using energy method,and then internal forces were analyzed by example.The results show that RBS leads to decreasing beam bending stiffness and lateral stiffness of rigid frame,the location of the point of inflection moves forward,but the moment of RBS beam fixed-end decreases and midspan moment increases;all the elements in the stiffness matrix decrease as compared with the ordinary connections,the reduction is related to the length of the beam,cutting depth,length of the cuts and distance from end of beam to initiation of the flange reduction.The beam flange reductions have main effect on beam stiffness,relatively small effect on internal force.Simplified calculation just to consider changes in stiffness and ignore the effect of changes in internal force was presented in the paper.
Reduced beam section connection(RBS) can make plastic hinge away from the beam and column interface,improve ductility of the structure and reach the purpose of seismic design of the connections.Element stiffness matrix and rotational displacement equation of the beam with RBS were derived using energy method,and then internal forces were analyzed by example.The results show that RBS leads to decreasing beam bending stiffness and lateral stiffness of rigid frame,the location of the point of inflection moves forward,but the moment of RBS beam fixed-end decreases and midspan moment increases;all the elements in the stiffness matrix decrease as compared with the ordinary connections,the reduction is related to the length of the beam,cutting depth,length of the cuts and distance from end of beam to initiation of the flange reduction.The beam flange reductions have main effect on beam stiffness,relatively small effect on internal force.Simplified calculation just to consider changes in stiffness and ignore the effect of changes in internal force was presented in the paper.
2011, 41(1): 120-123.
doi: 10.13204/j.gyjz201101027
Abstract:
Based on steel frame structure and frame-brace structure,a new type of structure-prestress-mega-braced steel frame was presented.Firstly it was analyzed work principle of prestressed mega brace,then the rule of initial prestress value was proposed,further researching the estimate method of mega brace deformation to set up,theory of initial prestress in mega brace.Initial prestress value should comply in the rule that residual tension in compression brace is near to zero under exterior loads.The vertical displacement of multi-storey prestress-mega-braced steel frame structure nearly equals to the value of steel frame structure under vertical load.And the horizontal displacement at brace end keeps fixed,no matter how to alter the relative stiffness of steel frame.
Based on steel frame structure and frame-brace structure,a new type of structure-prestress-mega-braced steel frame was presented.Firstly it was analyzed work principle of prestressed mega brace,then the rule of initial prestress value was proposed,further researching the estimate method of mega brace deformation to set up,theory of initial prestress in mega brace.Initial prestress value should comply in the rule that residual tension in compression brace is near to zero under exterior loads.The vertical displacement of multi-storey prestress-mega-braced steel frame structure nearly equals to the value of steel frame structure under vertical load.And the horizontal displacement at brace end keeps fixed,no matter how to alter the relative stiffness of steel frame.
2011, 41(1): 124-129.
doi: 10.13204/j.gyjz201101028
Abstract:
Based on random vibration theory,a wind power spectral analysis method in the frequency domain was used to analyze the wind induced vibration of long-span gable roofs supported by steel truss in this paper.The Davenport wind spectrum was used to calculate wind-induced vibration responses and wind vibration factor of the gable roofs.The influences of parameters such as the basic wind pressure,span and weight of the roof,damping ratio,terrain categories and support restraints,and etc on the wind vibration factor were discussed.Using results of the parametric analysis,a practical wind-induced vibration factor formula for long-span steel truss supporting gable roofs was summarized and recommeded.
Based on random vibration theory,a wind power spectral analysis method in the frequency domain was used to analyze the wind induced vibration of long-span gable roofs supported by steel truss in this paper.The Davenport wind spectrum was used to calculate wind-induced vibration responses and wind vibration factor of the gable roofs.The influences of parameters such as the basic wind pressure,span and weight of the roof,damping ratio,terrain categories and support restraints,and etc on the wind vibration factor were discussed.Using results of the parametric analysis,a practical wind-induced vibration factor formula for long-span steel truss supporting gable roofs was summarized and recommeded.
2011, 41(1): 130-135.
doi: 10.13204/j.gyjz201101029
Abstract:
The effective section method is used for design of cold-formed steel members,in which the effect local buckling on the deflections of members is taken into account in the design codes of most foreign countries.Because the ratio of width to thickness of cold-formed steel members is usually large,besides local buckling,distortional buckling is also occurred during the regular service stage and influences the membersdeflection behavior.It was explored a new method which could be used for calculating the overall bending deflection directly by full sectional properties instead of effective sectional properties.This method could be called direct deflection method(DDM).Based on the existing test results,it was also simulated the tests by the finite element program of ANSYS and the results showed good agreement with the test results.C-section pure bending members with upright,inclined and complex edge stiffeners were selected for finite element parametric analysis.The deflection situations were extracted under every load step for all members.By comparing the scatter pointsdistribution of every curve for different parameters and edge stiffener members,the DDM formulas for upright,inclined and complex edge stiffener members with different thicknesses were established.And the deflection calculation progress was enormously simplified.
The effective section method is used for design of cold-formed steel members,in which the effect local buckling on the deflections of members is taken into account in the design codes of most foreign countries.Because the ratio of width to thickness of cold-formed steel members is usually large,besides local buckling,distortional buckling is also occurred during the regular service stage and influences the membersdeflection behavior.It was explored a new method which could be used for calculating the overall bending deflection directly by full sectional properties instead of effective sectional properties.This method could be called direct deflection method(DDM).Based on the existing test results,it was also simulated the tests by the finite element program of ANSYS and the results showed good agreement with the test results.C-section pure bending members with upright,inclined and complex edge stiffeners were selected for finite element parametric analysis.The deflection situations were extracted under every load step for all members.By comparing the scatter pointsdistribution of every curve for different parameters and edge stiffener members,the DDM formulas for upright,inclined and complex edge stiffener members with different thicknesses were established.And the deflection calculation progress was enormously simplified.
2011, 41(1): 136-138.
doi: 10.13204/j.gyjz201101030
Abstract:
The design of multistory masonry structure is particular important,because it is one type of the most practical constructions in our country.GB 50011-2001Code for Seismic Design of Buildingsis the design code for anti-seismic zone and GB 50003-2001Code for Design of Masonry Structuresis one for both non-earthquake protection region and anti-seismic zone,but compared with the former,the latter is not strict enough in some constrains which would be worth to be discussed.As a result,this paper suggests doing necessary advancement.
The design of multistory masonry structure is particular important,because it is one type of the most practical constructions in our country.GB 50011-2001Code for Seismic Design of Buildingsis the design code for anti-seismic zone and GB 50003-2001Code for Design of Masonry Structuresis one for both non-earthquake protection region and anti-seismic zone,but compared with the former,the latter is not strict enough in some constrains which would be worth to be discussed.As a result,this paper suggests doing necessary advancement.
2011, 41(1): 139-141,25.
doi: 10.13204/j.gyjz201101031
Abstract:
Xiange Elementary School in Dujiangyan city as a case of post-earthquake reconstruction after wenchuan Earthquake in 2008 was introduced.It was introduced the new technologies,light gauge wood frame structure used in the school buildings for safety and sustainability.The new school was touched upon many significant issues of the post-earthquake reconstruction,involving the aspects of technology and environment.
Xiange Elementary School in Dujiangyan city as a case of post-earthquake reconstruction after wenchuan Earthquake in 2008 was introduced.It was introduced the new technologies,light gauge wood frame structure used in the school buildings for safety and sustainability.The new school was touched upon many significant issues of the post-earthquake reconstruction,involving the aspects of technology and environment.
