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2013 Vol. 43, No. 2
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2013, 43(2): 1-8.
doi: 10.13204/j.gyjz201302001
Abstract:
To improve the seismic behavior of high performance concrete shear wall(HPCW),a new stirrup arrangement of independent closed reinforcement hoops nested with each other in six HPCWs with edge columns was developed,and verified by the pseudo-static test.Aspect ratios of walls are 1～2,and axial load ratios 0.28 ～0.40.The cubic compressive strength of concrete is 89～99 MPa for different specimens.The ultimate strength of stirrup is 737.5 MPa.Development of cracks and failure modes of specimens were compared.Hysteretic characteristics,load-bearings,deformation-ability,and rigid attenuation,strain of reinforcement were analyzed.The displacement ductile ratios measured were 3.75～5.20,the coefficients of energy dissipation were 0.76～1.31.Results showed that the new stirrup arrangement effectively improved the seismic behavior of the HPSW with edge columns such as ductility,deformability,energy dissipation capacity etc.Based on results,allowable values of drift angle and rotation of plastic hinge for four performance levels of shear wall components were presented.
To improve the seismic behavior of high performance concrete shear wall(HPCW),a new stirrup arrangement of independent closed reinforcement hoops nested with each other in six HPCWs with edge columns was developed,and verified by the pseudo-static test.Aspect ratios of walls are 1～2,and axial load ratios 0.28 ～0.40.The cubic compressive strength of concrete is 89～99 MPa for different specimens.The ultimate strength of stirrup is 737.5 MPa.Development of cracks and failure modes of specimens were compared.Hysteretic characteristics,load-bearings,deformation-ability,and rigid attenuation,strain of reinforcement were analyzed.The displacement ductile ratios measured were 3.75～5.20,the coefficients of energy dissipation were 0.76～1.31.Results showed that the new stirrup arrangement effectively improved the seismic behavior of the HPSW with edge columns such as ductility,deformability,energy dissipation capacity etc.Based on results,allowable values of drift angle and rotation of plastic hinge for four performance levels of shear wall components were presented.
2013, 43(2): 9-13,28.
doi: 10.13204/j.gyjz201302002
Abstract:
The objective of this study is to study the axial compression performance,including strength and deformation behaviours of HSC columns confined by high-strength stirrups,and determine experimentally and analytically the magnitude of its strength enhancement.On the basis of a concentric loading test of 31 HSC columns confined by high-strength stirrups,the influences of the tie yield strength,tie spacing,and tie configuration on the characteristics of strength and ductility were evaluated;based on the test data at home and abroad,the formulas to determine peak strength and ultimate strain of high-strength concrete confined by high-strength stirrups were proposed by regression analysis.
The objective of this study is to study the axial compression performance,including strength and deformation behaviours of HSC columns confined by high-strength stirrups,and determine experimentally and analytically the magnitude of its strength enhancement.On the basis of a concentric loading test of 31 HSC columns confined by high-strength stirrups,the influences of the tie yield strength,tie spacing,and tie configuration on the characteristics of strength and ductility were evaluated;based on the test data at home and abroad,the formulas to determine peak strength and ultimate strain of high-strength concrete confined by high-strength stirrups were proposed by regression analysis.
2013, 43(2): 14-17,23.
doi: 10.13204/j.gyjz201302003
Abstract:
Seismic behaviors of three specimens of infilled frame structure with different vertical slit width whose scales were 1∶2,which were studied and compared under low reversed cyclic lateral loading in this paper.Emphasis was put on the evaluation of the failure mechanism,hysteresis loops,displacement ductility,deterioration of strength and stiffness and energy dissipation of the specimens under the seismic loads.This work provided a theoretical basis for the further study and practical application of infilled frame structures.
Seismic behaviors of three specimens of infilled frame structure with different vertical slit width whose scales were 1∶2,which were studied and compared under low reversed cyclic lateral loading in this paper.Emphasis was put on the evaluation of the failure mechanism,hysteresis loops,displacement ductility,deterioration of strength and stiffness and energy dissipation of the specimens under the seismic loads.This work provided a theoretical basis for the further study and practical application of infilled frame structures.
2013, 43(2): 18-23.
doi: 10.13204/j.gyjz201302004
Abstract:
Methods for vibration control of tall buildings under earthquakes were studied.By introducing the decentralized control strategy and combining the linear quadratic optimal control and iterative learning control(ILC),an algorithm of decentralized optimal iterative learning control(DOILC) was presented for the decentralized control of tall buildings vibration.A typical 20-storey seismically excited building was used for comparing the performance of the two control strategies.The results indicated that the decentralized control strategy could effectively mitigate structural seismic response as well as the traditional centralized control strategy but was superior in enhancing the reliability and more efficient in the data real-time processing of the control system.
Methods for vibration control of tall buildings under earthquakes were studied.By introducing the decentralized control strategy and combining the linear quadratic optimal control and iterative learning control(ILC),an algorithm of decentralized optimal iterative learning control(DOILC) was presented for the decentralized control of tall buildings vibration.A typical 20-storey seismically excited building was used for comparing the performance of the two control strategies.The results indicated that the decentralized control strategy could effectively mitigate structural seismic response as well as the traditional centralized control strategy but was superior in enhancing the reliability and more efficient in the data real-time processing of the control system.
2013, 43(2): 24-28.
doi: 10.13204/j.gyjz201302005
Abstract:
Combining with performance grades of reinforced concrete structures at home and abroad,the seismic performance of reinforced concrete shear wall structures can be divided into four levels: normal service,continual service,temporary service,life safety and collapse prevention.Considering four seismic levels,the structure performance objectives and seismic fortification criteria were formed.The equations to calculate physical displacement of shear wall specimens for different performance objectives were derived.Based on the statistical data of the experiments and results of reinforced concrete shear wall structures,quantization indexes of different performance levels of R.C shear wall structure were put forward.
Combining with performance grades of reinforced concrete structures at home and abroad,the seismic performance of reinforced concrete shear wall structures can be divided into four levels: normal service,continual service,temporary service,life safety and collapse prevention.Considering four seismic levels,the structure performance objectives and seismic fortification criteria were formed.The equations to calculate physical displacement of shear wall specimens for different performance objectives were derived.Based on the statistical data of the experiments and results of reinforced concrete shear wall structures,quantization indexes of different performance levels of R.C shear wall structure were put forward.
2013, 43(2): 29-33,44.
doi: 10.13204/j.gyjz201302006
Abstract:
Two-tower-connected high-rise building with enlarged base is a kind of complex structure system,seismic energy dissipation technology is introduced to control the structure's response.Based on 3-D finite element analysis by SAP2000,two models of biaxial axial symmetric and single axial symmetric two-tower-connected high-rise buildings with enlarged base were constructed respectively.Seismic response analysis of biaxial axial symmetric and single axial symmetric two-tower-connected high-rise buildings with enlarged base and corresponding seismic mitigation structures were proceeded by vibration model response spectrum method,the influence of different connecting methods on the structure in seismic resistance was investigated.
Two-tower-connected high-rise building with enlarged base is a kind of complex structure system,seismic energy dissipation technology is introduced to control the structure's response.Based on 3-D finite element analysis by SAP2000,two models of biaxial axial symmetric and single axial symmetric two-tower-connected high-rise buildings with enlarged base were constructed respectively.Seismic response analysis of biaxial axial symmetric and single axial symmetric two-tower-connected high-rise buildings with enlarged base and corresponding seismic mitigation structures were proceeded by vibration model response spectrum method,the influence of different connecting methods on the structure in seismic resistance was investigated.
2013, 43(2): 34-38,58.
doi: 10.13204/j.gyjz201302007
Abstract:
Based on the theoretical analysis and the finite element numerical calculation,the impact analysis of vibration-suppressed effectiveness of core-wall suspension isolation structure caused by dynamic parameter was made.A calculation method for the damping coefficient of the core-wall suspended structure was set up,under action of earthquake,the change law of damping coefficient of displacement and absolute acceleration,the vibration-suppressed effectiveness of core-wall suspension isolation structure caused by mass ratio and frequency ratio was also quantified.Research showed that the vibration-suppressed effectiveness of the relative displacement and absolute acceleration of the suspension isolated structure with bearings was stronger than the traditional suspension structure.It must ensure that mass ratio and frequency ratio should be in a certain range,which then could avoid resonance effect of the suspended structure happening and get an ideal vibration-suppressed effectiveness.
Based on the theoretical analysis and the finite element numerical calculation,the impact analysis of vibration-suppressed effectiveness of core-wall suspension isolation structure caused by dynamic parameter was made.A calculation method for the damping coefficient of the core-wall suspended structure was set up,under action of earthquake,the change law of damping coefficient of displacement and absolute acceleration,the vibration-suppressed effectiveness of core-wall suspension isolation structure caused by mass ratio and frequency ratio was also quantified.Research showed that the vibration-suppressed effectiveness of the relative displacement and absolute acceleration of the suspension isolated structure with bearings was stronger than the traditional suspension structure.It must ensure that mass ratio and frequency ratio should be in a certain range,which then could avoid resonance effect of the suspended structure happening and get an ideal vibration-suppressed effectiveness.
2013, 43(2): 39-44.
doi: 10.13204/j.gyjz201302008
Abstract:
The building layout determines the number of structural wall and wall area in the design of a masonry structure building.In the earthquake,the seismic force is taken by the wall in the direction of earthquake.The larger the wall area,the stronger the seismic capacity.Therefore,the wall area has a critical influence on masonry seismic research.One of the main ways for studying this problem is to find out the rules between the wall area and structure damage the earthquake.By analyzing of a large number of damage houses in the Wenchuan earthquake in 2008,the relationship of the wall area and buildings damage was studied,and based on the existing theory of masonry structure seismic performance assessment,the indicator of the wall areas was proposed to estimate the seismic damage degree of masonry structures.The indicator was applied to the seismic performance evaluation of a multi-storey masonry structure housing,this indicator was reasonable through comparing the on-site damage,the result showed the indicator could estimate the damage degree of the masonry buildings.
The building layout determines the number of structural wall and wall area in the design of a masonry structure building.In the earthquake,the seismic force is taken by the wall in the direction of earthquake.The larger the wall area,the stronger the seismic capacity.Therefore,the wall area has a critical influence on masonry seismic research.One of the main ways for studying this problem is to find out the rules between the wall area and structure damage the earthquake.By analyzing of a large number of damage houses in the Wenchuan earthquake in 2008,the relationship of the wall area and buildings damage was studied,and based on the existing theory of masonry structure seismic performance assessment,the indicator of the wall areas was proposed to estimate the seismic damage degree of masonry structures.The indicator was applied to the seismic performance evaluation of a multi-storey masonry structure housing,this indicator was reasonable through comparing the on-site damage,the result showed the indicator could estimate the damage degree of the masonry buildings.
2013, 43(2): 45-48.
doi: 10.13204/j.gyjz201302009
Abstract:
A innovative technique for retrofitting reinforced concrete(RC) columns using prestressing steel strips(PSS) was introduced,and quasi-static tests of reinforced concrete column retrofitted by this new method under high axial-compression ratio were conducted.In the quasi-static test of these four retrofitted concrete column specimens,the influence on specimens' seismic performance of axial-compression ratio and spacing of the steel strips were studied.And based on the test results,the seismic performance indexes such as characteristic of resilience,skeleton curve,ductility coefficient and energy consumption were all analyzed and discussed.It could be concluded that this innovative retrofit technique could markedly improve the column's deformation ability and ductility,so as to improve the column seismic performance.
A innovative technique for retrofitting reinforced concrete(RC) columns using prestressing steel strips(PSS) was introduced,and quasi-static tests of reinforced concrete column retrofitted by this new method under high axial-compression ratio were conducted.In the quasi-static test of these four retrofitted concrete column specimens,the influence on specimens' seismic performance of axial-compression ratio and spacing of the steel strips were studied.And based on the test results,the seismic performance indexes such as characteristic of resilience,skeleton curve,ductility coefficient and energy consumption were all analyzed and discussed.It could be concluded that this innovative retrofit technique could markedly improve the column's deformation ability and ductility,so as to improve the column seismic performance.
2013, 43(2): 49-54,98.
doi: 10.13204/j.gyjz201302010
Abstract:
Reinforcement and repair methods of earthquake damaged concrete structures was studied in this paper.RC beams with different reinforcement ratio and RC columns with different axial compression ratio were experimented under horizontal low cyclic loading.The effect of pasting armor plate or carbon cloth on damaged concrete structures was analysed.The features of different reinforcement and repair methods were summed up in the paper.Practical suggestions were offered for reinforcement and repair projects.theory evidence was also provieded for revising standard of reinforcement and repair.
Reinforcement and repair methods of earthquake damaged concrete structures was studied in this paper.RC beams with different reinforcement ratio and RC columns with different axial compression ratio were experimented under horizontal low cyclic loading.The effect of pasting armor plate or carbon cloth on damaged concrete structures was analysed.The features of different reinforcement and repair methods were summed up in the paper.Practical suggestions were offered for reinforcement and repair projects.theory evidence was also provieded for revising standard of reinforcement and repair.
2013, 43(2): 55-58.
doi: 10.13204/j.gyjz201302011
Abstract:
In the country's rapid urbanization process and the trend of the worsening ecological environment,it is very significant to the sustainable development of a city by means of deep analysis of ecological environment and a discussion on the construction theory of industrial landscape features in the trend of the worsening ecological environment.Taking the planning of Xifeng Industrial Park in Qingyang City for example,it was studied the construction of ecological environment of an urban industrial park.The final purpose was causing many scholars to pay much attention and do more researches on the development of on industrial parks,and promoting the construction of industrial park into a normal and scientific development way,thereby realizing the services for protecting urban ecological environment and raising the level of people's cultural life.
In the country's rapid urbanization process and the trend of the worsening ecological environment,it is very significant to the sustainable development of a city by means of deep analysis of ecological environment and a discussion on the construction theory of industrial landscape features in the trend of the worsening ecological environment.Taking the planning of Xifeng Industrial Park in Qingyang City for example,it was studied the construction of ecological environment of an urban industrial park.The final purpose was causing many scholars to pay much attention and do more researches on the development of on industrial parks,and promoting the construction of industrial park into a normal and scientific development way,thereby realizing the services for protecting urban ecological environment and raising the level of people's cultural life.
2013, 43(2): 59-60,103.
doi: 10.13204/j.gyjz201302012
Abstract:
In today's intense period of transformation by the wave of industrialization,the conslurction of large-scale industrial parks often forces designer to accommodate the utilitarian value of a building,and neglect ethical function and aesthetic attitudes of the building.Beijng in the forefront of the construction ideology,the designers should find their own course of action from an artistic point of view to establish a starting origin,i.e the stand of the design.
In today's intense period of transformation by the wave of industrialization,the conslurction of large-scale industrial parks often forces designer to accommodate the utilitarian value of a building,and neglect ethical function and aesthetic attitudes of the building.Beijng in the forefront of the construction ideology,the designers should find their own course of action from an artistic point of view to establish a starting origin,i.e the stand of the design.
2013, 43(2): 61-66,142.
doi: 10.13204/j.gyjz201302013
Abstract:
It was studied the surface settlement,excess pore water pressure,deep settlement and lateral displacement etc,as well as improving effect of thick soft subsoil below large overburden treated by vacuum combined surcharge preloading,according to monitoring and detection data on site.The results showed that the curve of surface settlement was smooth and there was no obvious gradient change section during high fill preloading,because of stress diffusion of the overburden.The compressive deformation of subsoil occurred mainly in the soft soil layer below the overburden,and the increase and dissipation of the excess pore water pressure were offected by the co-action of vacuum pressure and filled preloading,which were related to the thickness of the overburden.When the overburden was thin,it had a faster response,so the value of the excess pore water pressure by preloading was larger;when it was thick,the value of the excess pore water pressure was smaller.Hence,it is unfavorable to drainage and improving of a soft soil in case of existing overburden,to which attention should be paid in the design and construction of a project.
It was studied the surface settlement,excess pore water pressure,deep settlement and lateral displacement etc,as well as improving effect of thick soft subsoil below large overburden treated by vacuum combined surcharge preloading,according to monitoring and detection data on site.The results showed that the curve of surface settlement was smooth and there was no obvious gradient change section during high fill preloading,because of stress diffusion of the overburden.The compressive deformation of subsoil occurred mainly in the soft soil layer below the overburden,and the increase and dissipation of the excess pore water pressure were offected by the co-action of vacuum pressure and filled preloading,which were related to the thickness of the overburden.When the overburden was thin,it had a faster response,so the value of the excess pore water pressure by preloading was larger;when it was thick,the value of the excess pore water pressure was smaller.Hence,it is unfavorable to drainage and improving of a soft soil in case of existing overburden,to which attention should be paid in the design and construction of a project.
2013, 43(2): 67-71.
doi: 10.13204/j.gyjz201302014
Abstract:
The centrifugal model tests were used to study mechanical property of cellular diaphragm wall in the clay and in the sand.The strains of the walls,the displacements of the walls and soil pressures were measured in the model tests.The results showed that soil pressure,bending moment and displacement of walls in the sand were greater than in the clay.The displacement model of cellular diaphragm wall was overall forward.The soil pressure in the inner was larger than the outer in the same section.It was reasonable to make front wall thicker than back wall due to the greater bending moment of front wall.Compared with in the sand,the maximum moment for front and back wall increased nearly three times in the clay.
The centrifugal model tests were used to study mechanical property of cellular diaphragm wall in the clay and in the sand.The strains of the walls,the displacements of the walls and soil pressures were measured in the model tests.The results showed that soil pressure,bending moment and displacement of walls in the sand were greater than in the clay.The displacement model of cellular diaphragm wall was overall forward.The soil pressure in the inner was larger than the outer in the same section.It was reasonable to make front wall thicker than back wall due to the greater bending moment of front wall.Compared with in the sand,the maximum moment for front and back wall increased nearly three times in the clay.
2013, 43(2): 72-77,71.
doi: 10.13204/j.gyjz201302015
Abstract:
An approach for evaluating the upper-bound for bearing capacity factor N was presented.The equivalence of limit analysis and limit equilibrium method was analyzed,and then a kinematical admissible failure mechanism,which was composed of a sequence of rigid triangles,was considered in the framework of limit equilibrium method.The recursion formula of inter-slice force was deduced according to the force equilibrium conditions of slice,and optimal bottom inclination of each triangle also was obtained by employing the principle of maximum thrust force.Therefore,the critical failure mechanism and corresponding N value were obtained.Then,the influence of inclined ground surface on N value was discussed.These solutions,presented in the form of graphs,were compared against existing semi-empirical expressions and numerical solutions.Finally,approximate analytical expressions for N and (correction factor of inclined ground surface) were suggested.The present method,which was of simple principle and could be readily implemented into computer software,could solve a lower N value than other's the upper-bound solutions.The study results could be used in theoretical analysis of bearing capacity and provideed some beneficial references for further research on N.
An approach for evaluating the upper-bound for bearing capacity factor N was presented.The equivalence of limit analysis and limit equilibrium method was analyzed,and then a kinematical admissible failure mechanism,which was composed of a sequence of rigid triangles,was considered in the framework of limit equilibrium method.The recursion formula of inter-slice force was deduced according to the force equilibrium conditions of slice,and optimal bottom inclination of each triangle also was obtained by employing the principle of maximum thrust force.Therefore,the critical failure mechanism and corresponding N value were obtained.Then,the influence of inclined ground surface on N value was discussed.These solutions,presented in the form of graphs,were compared against existing semi-empirical expressions and numerical solutions.Finally,approximate analytical expressions for N and (correction factor of inclined ground surface) were suggested.The present method,which was of simple principle and could be readily implemented into computer software,could solve a lower N value than other's the upper-bound solutions.The study results could be used in theoretical analysis of bearing capacity and provideed some beneficial references for further research on N.
2013, 43(2): 78-82,171.
doi: 10.13204/j.gyjz201302016
Abstract:
There are many gullies in the loess plateau region.A most unfavorable topographic condition occured when tunnels passed through the gully region.It meaned that tunnels needed to pass through the ultra-shallow and large-bias sections.In order to obtain the economic and safe crossing scheme,the conception of economic safety coefficient ratio and its calculation principle was brought forward.Firstly,the tunnel crossing schemes through ultra-shallow and large-bias sections were designed.The economic safety coefficient ratio of each tunnel crossing scheme was calculated by the methods of strength reduction method and related quotas.Besides,the tunnel's rock stress,deformations and the primary support's stress were simulated and compared among the three tunnel crossing schemes.Finally,the counterweight fill method was considered to be the best crossing scheme,with which the ultra-shallow and large-bias tunnel was in the steady state during the construction period.Good results were achieved so as to offer reference for the future similar projects.
There are many gullies in the loess plateau region.A most unfavorable topographic condition occured when tunnels passed through the gully region.It meaned that tunnels needed to pass through the ultra-shallow and large-bias sections.In order to obtain the economic and safe crossing scheme,the conception of economic safety coefficient ratio and its calculation principle was brought forward.Firstly,the tunnel crossing schemes through ultra-shallow and large-bias sections were designed.The economic safety coefficient ratio of each tunnel crossing scheme was calculated by the methods of strength reduction method and related quotas.Besides,the tunnel's rock stress,deformations and the primary support's stress were simulated and compared among the three tunnel crossing schemes.Finally,the counterweight fill method was considered to be the best crossing scheme,with which the ultra-shallow and large-bias tunnel was in the steady state during the construction period.Good results were achieved so as to offer reference for the future similar projects.
2013, 43(2): 83-87.
doi: 10.13204/j.gyjz201302017
Abstract:
Integrated the calculation method of the surrounding rock static earth pressure in the Code for Design of Tunnel for Road and Railway,it was assumed that the fracture plane caused by earthquake in the soil of surrounding rock was balanced by the static equilibrium,in which the calculation formulas of tunnel seismic earth pressure were deduced and the seismic lateral soil pressure coefficient commonly used was converged into forms to be checked.The method belongs to general method of sliding wedge-earthquake intensity and compared with several common quasi-statics methods proposed for retaining wall structure,the D-value between the seismic lateral soil pressure coefficient and the static lateral soil pressure coefficient was close to the average value counted by other methods and at the same time the form was close to static earth pressure calculation formula,when horizontal earthquake coefficient was 0,the formula totally coincided with that of the static earth pressure,which was suitable for application by engineers.
Integrated the calculation method of the surrounding rock static earth pressure in the Code for Design of Tunnel for Road and Railway,it was assumed that the fracture plane caused by earthquake in the soil of surrounding rock was balanced by the static equilibrium,in which the calculation formulas of tunnel seismic earth pressure were deduced and the seismic lateral soil pressure coefficient commonly used was converged into forms to be checked.The method belongs to general method of sliding wedge-earthquake intensity and compared with several common quasi-statics methods proposed for retaining wall structure,the D-value between the seismic lateral soil pressure coefficient and the static lateral soil pressure coefficient was close to the average value counted by other methods and at the same time the form was close to static earth pressure calculation formula,when horizontal earthquake coefficient was 0,the formula totally coincided with that of the static earth pressure,which was suitable for application by engineers.
2013, 43(2): 88-93,133.
doi: 10.13204/j.gyjz201302018
Abstract:
To explore the characteristics of high support system of formwork during the process of pouring concrete,an underground club in Xi'an was chosen as research object.While pouring concrete,the electrical measuring method was used to measure the stress of steel pipe in high support system and the measured results were compared with the results simulated by finite element analysis software ANSYS.The results showed that the pouring sequence of concrete had a great impact on axial force trends and the location of the maximum axial force.What's more,in the calculation of the overall stability of high support system for formwork,imaginary horizontal force should be used.To improve the security of the formwork support system,the erection program of high support system and the pouring sequence of concrete should be determined based on the analysis of finite element of high support system for formwork.
To explore the characteristics of high support system of formwork during the process of pouring concrete,an underground club in Xi'an was chosen as research object.While pouring concrete,the electrical measuring method was used to measure the stress of steel pipe in high support system and the measured results were compared with the results simulated by finite element analysis software ANSYS.The results showed that the pouring sequence of concrete had a great impact on axial force trends and the location of the maximum axial force.What's more,in the calculation of the overall stability of high support system for formwork,imaginary horizontal force should be used.To improve the security of the formwork support system,the erection program of high support system and the pouring sequence of concrete should be determined based on the analysis of finite element of high support system for formwork.
2013, 43(2): 94-98.
doi: 10.13204/j.gyjz201302019
Abstract:
Collapses of supporting systems and cracking of the supported floors often happen during the period of construction because of unsuitable configuration and incorrect removal of supporting system.Combined with field detection,three-dimension model of multistory formwork support system was built by FEM,the model could reveal the effects of the removal time and building style of supporting system on the bearing capacity of structure,and propose the corresponding technique key points with different structural styles.The study provided the scientific guides for controlling the safety,high-speed cycling of supports system and the reference to safety of construction.
Collapses of supporting systems and cracking of the supported floors often happen during the period of construction because of unsuitable configuration and incorrect removal of supporting system.Combined with field detection,three-dimension model of multistory formwork support system was built by FEM,the model could reveal the effects of the removal time and building style of supporting system on the bearing capacity of structure,and propose the corresponding technique key points with different structural styles.The study provided the scientific guides for controlling the safety,high-speed cycling of supports system and the reference to safety of construction.
2013, 43(2): 99-103.
doi: 10.13204/j.gyjz201302020
Abstract:
Experimental study on the bending performance of pre-damaged reinforced concrete beams strengthened with bonding CFRP under air and seawater environment was carried out in this contribution.The influence of seawater on the damage mode,cracks development,strain development and bending capacity,and so on of the strengthened beams were measured.Based on the experimental results,it was found that the bending capacity and stiffness of the strengthened pre-damaged beams were improved effectively.And development of cracks was limited.Although their performances were decreased obviously with time prolonged under seawater environment,the effect of reinforcement was still reliable.Finally,it should be pointed out that during the test,strain of the concrete complied with the plane-section assumption.
Experimental study on the bending performance of pre-damaged reinforced concrete beams strengthened with bonding CFRP under air and seawater environment was carried out in this contribution.The influence of seawater on the damage mode,cracks development,strain development and bending capacity,and so on of the strengthened beams were measured.Based on the experimental results,it was found that the bending capacity and stiffness of the strengthened pre-damaged beams were improved effectively.And development of cracks was limited.Although their performances were decreased obviously with time prolonged under seawater environment,the effect of reinforcement was still reliable.Finally,it should be pointed out that during the test,strain of the concrete complied with the plane-section assumption.
2013, 43(2): 104-109.
doi: 10.13204/j.gyjz201302021
Abstract:
Based on the investigation on the flexural toughness according to DBV,it was analysed the steel fiber distribution in the cross-section of testing beams.The results indicated that steel fiber distribution in the failure section could have a high scatter for different beams with the same fiber content;the relationship between the fiber content and fiber number per unit cross-sectional area was established by the linear regression of the statistical data,which could predict the fiber number at the damaged section in case of different fiber content.The test results showed that the toughness of the beam could be significantly affected by the fiber distribution in the cross section.
Based on the investigation on the flexural toughness according to DBV,it was analysed the steel fiber distribution in the cross-section of testing beams.The results indicated that steel fiber distribution in the failure section could have a high scatter for different beams with the same fiber content;the relationship between the fiber content and fiber number per unit cross-sectional area was established by the linear regression of the statistical data,which could predict the fiber number at the damaged section in case of different fiber content.The test results showed that the toughness of the beam could be significantly affected by the fiber distribution in the cross section.
2013, 43(2): 110-112,137.
doi: 10.13204/j.gyjz201302022
Abstract:
Two different BFRP stirrups tensile test methods were described when the members were in the shear state,which could imitate the real stress of such stirrups.One was for L-type BFRP stirrup test,the other was for U-shaped BFRP stirrup tensile test.It was compared the tensile mechanical properties of the stirrups in two components under shear state,and was also analyzed the difference of the two methods.Furthermore,a recommended formula of basalt fiber reinforcement plastics tensile strength when C30 concrete structures under shear conditions was proposed.
Two different BFRP stirrups tensile test methods were described when the members were in the shear state,which could imitate the real stress of such stirrups.One was for L-type BFRP stirrup test,the other was for U-shaped BFRP stirrup tensile test.It was compared the tensile mechanical properties of the stirrups in two components under shear state,and was also analyzed the difference of the two methods.Furthermore,a recommended formula of basalt fiber reinforcement plastics tensile strength when C30 concrete structures under shear conditions was proposed.
2013, 43(2): 113-116,158.
doi: 10.13204/j.gyjz201302023
Abstract:
The effect of steel slag and blast furnace slag,water to cement ratio and air-entraining agent on concrete permeability was studied by measuring the chloride ion diffusivity coefficient and pore feature of cross section of concrete exposed to salt frost.The results showed that increase rate of permeability of hardened concrete would slow down,and impermeability of concrete would increase with the addition of ground steel slag and blast furnace slag.Although exposed to salt frost for a long time,permeability of concrete with the water to cement ratio of 0.39 increased not obviously.The permeability of concrete with the water to cement ratio of 0.6 showed a linear increase with the increase of freeze-thaw cycles;Permeability of air-entrained concrete would surpass the permeability of non-air entrained concrete ultimately.Most air bubbles in concrete were distributed in interface transition zone and,connectivity and diameter of air bubbles increased with the increasing of freeze-thaw cycles.
The effect of steel slag and blast furnace slag,water to cement ratio and air-entraining agent on concrete permeability was studied by measuring the chloride ion diffusivity coefficient and pore feature of cross section of concrete exposed to salt frost.The results showed that increase rate of permeability of hardened concrete would slow down,and impermeability of concrete would increase with the addition of ground steel slag and blast furnace slag.Although exposed to salt frost for a long time,permeability of concrete with the water to cement ratio of 0.39 increased not obviously.The permeability of concrete with the water to cement ratio of 0.6 showed a linear increase with the increase of freeze-thaw cycles;Permeability of air-entrained concrete would surpass the permeability of non-air entrained concrete ultimately.Most air bubbles in concrete were distributed in interface transition zone and,connectivity and diameter of air bubbles increased with the increasing of freeze-thaw cycles.
2013, 43(2): 117-120,127.
doi: 10.13204/j.gyjz201302024
Abstract:
The characteristics of wind pressures distribution on the single and double hemispherical dry-coal-sheds with day-lighting ceiling were investigated by using CFD.Compared with the wind pressures gained by wind tunnel tests in reference,the CFD results were credible.Base on the CFD results,the influences of terrain types,wind directions and interference conditions on the block shape coefficients and drag force and lift force coefficients were discussed.Finally,the block shape coefficients and drag force and lift force coefficients of the total structure were given in the non-interference and interference conditions,which were suitable for engineering application.
The characteristics of wind pressures distribution on the single and double hemispherical dry-coal-sheds with day-lighting ceiling were investigated by using CFD.Compared with the wind pressures gained by wind tunnel tests in reference,the CFD results were credible.Base on the CFD results,the influences of terrain types,wind directions and interference conditions on the block shape coefficients and drag force and lift force coefficients were discussed.Finally,the block shape coefficients and drag force and lift force coefficients of the total structure were given in the non-interference and interference conditions,which were suitable for engineering application.
2013, 43(2): 121-127.
doi: 10.13204/j.gyjz201302025
Abstract:
In order to study the mechanical properties of concrete-filled opening hole damaged steel tubular members,14 concrete-filled opening hole damaged steel tubular specimens were designed for the axial compressive test.The change parameters of opening damage rate,concrete grade strength,slenderness ratio were considered.Through this test,the whole mechanical process and failure pattern of all specimens were observed,the failure mechanism,load-deformation and stress-strain curves of concrete-filled opening hole damaged steel tubular specimens were obtained,The influence of change parameters including opening damage rate,concrete grade strength,slenderness ratio on the mechanical properties of concrete-filled opening hole damaged steel tubular members were analyzed.Test results indicated that the specimens in the loading late stage had good ductility;the failure pattern was the local buckling and tear failure.The opening damage rate of the specimens has some degree of impact on the failure pattern and ultimate bearing capacity.Finally the calculation method of bearing capacity of concrete-filled opening hole damaged steel tubular was discussed,based on the formulas of existing criteria,and the result showed that while the opening damage rate was not big( 0.8%),the calculated results by the existing standard methods of concrete-filled steel tubular were safe.
In order to study the mechanical properties of concrete-filled opening hole damaged steel tubular members,14 concrete-filled opening hole damaged steel tubular specimens were designed for the axial compressive test.The change parameters of opening damage rate,concrete grade strength,slenderness ratio were considered.Through this test,the whole mechanical process and failure pattern of all specimens were observed,the failure mechanism,load-deformation and stress-strain curves of concrete-filled opening hole damaged steel tubular specimens were obtained,The influence of change parameters including opening damage rate,concrete grade strength,slenderness ratio on the mechanical properties of concrete-filled opening hole damaged steel tubular members were analyzed.Test results indicated that the specimens in the loading late stage had good ductility;the failure pattern was the local buckling and tear failure.The opening damage rate of the specimens has some degree of impact on the failure pattern and ultimate bearing capacity.Finally the calculation method of bearing capacity of concrete-filled opening hole damaged steel tubular was discussed,based on the formulas of existing criteria,and the result showed that while the opening damage rate was not big( 0.8%),the calculated results by the existing standard methods of concrete-filled steel tubular were safe.
2013, 43(2): 128-133.
doi: 10.13204/j.gyjz201302026
Abstract:
Chevron braces are commonly used in tall steel building structures.The compressive brace of this bracing system may experience dramatic strength degradation after buckling,which leads to the formation of a vertical unbalance force in the intersection point of the compressive and tensile braces.Thus,the beam of the chevron braced frame should be designed as a strong beam,i.e.capable of resisting this vertical unbalance force.The results of static push-over analyses showed that the lateral force resistance of a chevron braced frame with strong beam depends largely on the yielding load of the tensile brace.However,each of the bracing members is in the compressive or tensile load alternatively when the braced frame undergoes the severe seismic action,and thus the behaviour of the braced frame is more complicated in this case than that revealed via the push-over analysis.It was carried out a series of analyses on the performance of the chevron braced frames under cyclic and seismic loads.
Chevron braces are commonly used in tall steel building structures.The compressive brace of this bracing system may experience dramatic strength degradation after buckling,which leads to the formation of a vertical unbalance force in the intersection point of the compressive and tensile braces.Thus,the beam of the chevron braced frame should be designed as a strong beam,i.e.capable of resisting this vertical unbalance force.The results of static push-over analyses showed that the lateral force resistance of a chevron braced frame with strong beam depends largely on the yielding load of the tensile brace.However,each of the bracing members is in the compressive or tensile load alternatively when the braced frame undergoes the severe seismic action,and thus the behaviour of the braced frame is more complicated in this case than that revealed via the push-over analysis.It was carried out a series of analyses on the performance of the chevron braced frames under cyclic and seismic loads.
2013, 43(2): 134-137.
doi: 10.13204/j.gyjz201302027
Abstract:
The large cantilever crane girder system was formed after removing the corner column in a large wire bar workshop.The load of roof was carried by the roof limb truss and the load of crane was carried by the continuous cantilever crane beam.At the same time,through the design of detail treatment,the system spatial entirety and structural deformation coordination were ensured.
The large cantilever crane girder system was formed after removing the corner column in a large wire bar workshop.The load of roof was carried by the roof limb truss and the load of crane was carried by the continuous cantilever crane beam.At the same time,through the design of detail treatment,the system spatial entirety and structural deformation coordination were ensured.
2013, 43(2): 138-142.
doi: 10.13204/j.gyjz201302028
Abstract:
It was mainly studied the wind load of large power station boiler steel structure,the Chinese Specification for Design of Boiler Steel Structures(GB/T 223952008) and the United States UBC97 and ASCE7 specification were used for static analysis.It was elaborated the norms of the wind load provisions in the boiler steel structure design,and the wind load conversion between each standard;and it was also compared three regulating wind load calculation methods.Through an engineering example,the wind load and vertical load were combined in accordance with the relevant specification calculation,and added to that of the frame,using the structural analysis program STAAD V8i to do structure spatial analysis,it was obtained the horizontal force displacement,the internal force and stress ratio of the structure.
It was mainly studied the wind load of large power station boiler steel structure,the Chinese Specification for Design of Boiler Steel Structures(GB/T 223952008) and the United States UBC97 and ASCE7 specification were used for static analysis.It was elaborated the norms of the wind load provisions in the boiler steel structure design,and the wind load conversion between each standard;and it was also compared three regulating wind load calculation methods.Through an engineering example,the wind load and vertical load were combined in accordance with the relevant specification calculation,and added to that of the frame,using the structural analysis program STAAD V8i to do structure spatial analysis,it was obtained the horizontal force displacement,the internal force and stress ratio of the structure.
2013, 43(2): 143-147.
doi: 10.13204/j.gyjz201302029
Abstract:
For studying the feasibility of the damage identification method based on vibration transmissibility,various simulation experiments on a cantilever beam were done to study the repeatability,sensitivity for damage,and sensitivity for damage location.The results of the simulation experiments showed that the viration transmissibility was independent of the exciting load,sensitive to damage strongly,and can identify the damage locations.But in comparison with identifying several damage locations,the method could identify single damage location more effectively.
For studying the feasibility of the damage identification method based on vibration transmissibility,various simulation experiments on a cantilever beam were done to study the repeatability,sensitivity for damage,and sensitivity for damage location.The results of the simulation experiments showed that the viration transmissibility was independent of the exciting load,sensitive to damage strongly,and can identify the damage locations.But in comparison with identifying several damage locations,the method could identify single damage location more effectively.
2013, 43(2): 148-152,174.
doi: 10.13204/j.gyjz201302030
Abstract:
Construction joints of seven turbine foundations were not treated appropriately during pouring.In the detection and appraisal,density of concrete was detected through core-drilling and redar-detection;bearing capacity analysis and safety evaluation were performed with consideration of the specialty of wind turbine foundations;feasible treatment suggestions like pressure-grouting and adding shear connectors were also proposed,which had achieved good effect.Which supplied a reference for prevention and treatment of stratification of wind turbine foundations.
Construction joints of seven turbine foundations were not treated appropriately during pouring.In the detection and appraisal,density of concrete was detected through core-drilling and redar-detection;bearing capacity analysis and safety evaluation were performed with consideration of the specialty of wind turbine foundations;feasible treatment suggestions like pressure-grouting and adding shear connectors were also proposed,which had achieved good effect.Which supplied a reference for prevention and treatment of stratification of wind turbine foundations.
2013, 43(2): 153-158.
doi: 10.13204/j.gyjz201302031
Abstract:
Based on the first hand information such as the Report of the COI into Collapse of Cooling Towers at Ferrybridge and Proceedings of the First International Symposium on Natural Draught Cooling Towers-Ferrybridge and After,objective and comprehensive introductions were given for the collapse accident at Ferrybridge Power Station.Also,investigations,analyses and viewpoints from different researchers were also collected.Both of them are valuable and consultative for researchers and engineers.
Based on the first hand information such as the Report of the COI into Collapse of Cooling Towers at Ferrybridge and Proceedings of the First International Symposium on Natural Draught Cooling Towers-Ferrybridge and After,objective and comprehensive introductions were given for the collapse accident at Ferrybridge Power Station.Also,investigations,analyses and viewpoints from different researchers were also collected.Both of them are valuable and consultative for researchers and engineers.
2013, 43(2): 159-163.
doi: 10.13204/j.gyjz201302032
Abstract:
When designing structures,engineers should pay attention to various structural changing that may arise in the construction process.Construction enterprises should do their work strictly according to relevant laws and regulations.In the construction process of a shopping mall,the provisional supports on both sides of post-cast strip were removed earlier than required in order to improve the utilization of molds,which caused floor sinking deflection up to about 9 cm.Finite element software ANSYS was used for simulation of the process in which the reinforcement across the post-cast strip was modeled as link element.The finite element model of structure without support between adjacent floors was made.After analysis and calculation,the damaged parts of the structure were located,and the maximum deflection of prediction was 11 cm or so,which was consistent with the actual structure.Furthermore,the capacities of the structure with the existing geometry were analyzed for afterwards strengthening after closing the post-cast strip.
When designing structures,engineers should pay attention to various structural changing that may arise in the construction process.Construction enterprises should do their work strictly according to relevant laws and regulations.In the construction process of a shopping mall,the provisional supports on both sides of post-cast strip were removed earlier than required in order to improve the utilization of molds,which caused floor sinking deflection up to about 9 cm.Finite element software ANSYS was used for simulation of the process in which the reinforcement across the post-cast strip was modeled as link element.The finite element model of structure without support between adjacent floors was made.After analysis and calculation,the damaged parts of the structure were located,and the maximum deflection of prediction was 11 cm or so,which was consistent with the actual structure.Furthermore,the capacities of the structure with the existing geometry were analyzed for afterwards strengthening after closing the post-cast strip.
2013, 43(2): 164-167.
doi: 10.13204/j.gyjz201302033
Abstract:
To improve the environment of derelict industrial land,valuable elements that left in the wasteland were refined,ecological technology and method in the way of memory were used to and restore industrial history,recreate the industrial energy,which could provide a personalized park landscape for creation by artists and relaxation entertainment by citizens.
To improve the environment of derelict industrial land,valuable elements that left in the wasteland were refined,ecological technology and method in the way of memory were used to and restore industrial history,recreate the industrial energy,which could provide a personalized park landscape for creation by artists and relaxation entertainment by citizens.
2013, 43(2): 168-171.
doi: 10.13204/j.gyjz201302034
Abstract:
It was briefly introduced the merits of the adaptive reuse of the existing buildings,taking an industrial plant for example,it was also discussed the thinking and approaches to reuse them.Through studying the building's integrated renovation in many respects and the ideas of the related structural design and reuse scheme were expunded,it was expected to provide a reference and experience for colleagues.
It was briefly introduced the merits of the adaptive reuse of the existing buildings,taking an industrial plant for example,it was also discussed the thinking and approaches to reuse them.Through studying the building's integrated renovation in many respects and the ideas of the related structural design and reuse scheme were expunded,it was expected to provide a reference and experience for colleagues.
2013, 43(2): 172-174.
doi: 10.13204/j.gyjz201302035
Abstract:
Based on the theory of holistic regionalism,features of new Jiageng Builing were studied in terms of general plan,exterior facade,interior space and material details.The target of this study was to discuss how the new building dealed with the relationship between the contemporary architectural system and the traditional Jiageng Builing specialties so as to create new building environment which was in accord with the local nature condition,embodied the authentic extension of regional culture and technology,to provide beneficial architectural practice and theory for the contemporary regional architecture development.
Based on the theory of holistic regionalism,features of new Jiageng Builing were studied in terms of general plan,exterior facade,interior space and material details.The target of this study was to discuss how the new building dealed with the relationship between the contemporary architectural system and the traditional Jiageng Builing specialties so as to create new building environment which was in accord with the local nature condition,embodied the authentic extension of regional culture and technology,to provide beneficial architectural practice and theory for the contemporary regional architecture development.
