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2013 Vol. 43, No. 8
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2013, 43(8): 1-9.
doi: 10.13204/j.gyjz201308001
Abstract:
In order to develop the design theory based on performance, from structure performance concept, performance approach, the basic requirement of performance design, the performance system model of structural whole life-cycle performance design was set up.In this paper load action levels were reflected through load value criteria of different design service life, and the determination method of variable load value criteria was given;The performance levels of structure were divided into three aspects, and the durability of structure was divided into three levels.It was proposed that three level performance indexes(criteria) are taken as control indexes(criteria)of structure performance.It was suggested that while durability levels are one, two and three levels, the risk-based performance indexes should be 1.0, 1.5 and 2.0 respectively.It was proposed that the harmful medium diffusion depth, steel rust corrosion rate and rust expansion crack width index are taken as the control indexes of structural durability design.
In order to develop the design theory based on performance, from structure performance concept, performance approach, the basic requirement of performance design, the performance system model of structural whole life-cycle performance design was set up.In this paper load action levels were reflected through load value criteria of different design service life, and the determination method of variable load value criteria was given;The performance levels of structure were divided into three aspects, and the durability of structure was divided into three levels.It was proposed that three level performance indexes(criteria) are taken as control indexes(criteria)of structure performance.It was suggested that while durability levels are one, two and three levels, the risk-based performance indexes should be 1.0, 1.5 and 2.0 respectively.It was proposed that the harmful medium diffusion depth, steel rust corrosion rate and rust expansion crack width index are taken as the control indexes of structural durability design.
2013, 43(8): 10-14.
doi: 10.13204/j.gyjz201308002
Abstract:
General design formula in seismic combination can be obtained by associating combination of actions based on stochastic processes with design value method.It aims at improving flexibility of design.Due to the large variability of seismic action, the sensitivity factors recommended by international standard are not suitable.If the variability of variables changed greatly, in order to improve the control precision of reliability, standardized sensitivity factor values must be re-valued.Enumeration optimization method is lack of purpose.A function that can give a qualitative optimization direction is proposed.It can give the contribution to the difference between calculated and target value of reliability index caused by the sensitivity factor value of each variable.The function can be used in choosing initial value process and optimizing process, overall optimal result can be obtained under all proportion pairs.The standardized sensitivity factors are used for different design working life and different target reliability index, the errors show that optimization link can use 50-year design working life and a suitable target reliability index.
General design formula in seismic combination can be obtained by associating combination of actions based on stochastic processes with design value method.It aims at improving flexibility of design.Due to the large variability of seismic action, the sensitivity factors recommended by international standard are not suitable.If the variability of variables changed greatly, in order to improve the control precision of reliability, standardized sensitivity factor values must be re-valued.Enumeration optimization method is lack of purpose.A function that can give a qualitative optimization direction is proposed.It can give the contribution to the difference between calculated and target value of reliability index caused by the sensitivity factor value of each variable.The function can be used in choosing initial value process and optimizing process, overall optimal result can be obtained under all proportion pairs.The standardized sensitivity factors are used for different design working life and different target reliability index, the errors show that optimization link can use 50-year design working life and a suitable target reliability index.
2013, 43(8): 15-18.
doi: 10.13204/j.gyjz201308003
Abstract:
A few damage evaluation indicators based on modal flexibility matrix.These indicators, such as the change in modal flexibility, the rate in modal flexibility and the change in the modal flexibility curvature, were valid to some extent.However, these indicators need the flexibility matrix before and after damaging, were restricted to some extent in practical projects.In this paper, a new damage indicator was proposed based on damage flexibility curvature, which does not need the structure information before damaging.Two simulations, a simple beam and a two-span continuous beam, are utilized to verify the new indicator.Through the simulation results indicate that the damage location in structures, with single damage, multiple ones and slighter ones, can be detected efficiently.The value of the indicator is increased with the damage severity, the damage severity can be qualitatively detected.Anti-noise performance of the new damage indicator is better.
A few damage evaluation indicators based on modal flexibility matrix.These indicators, such as the change in modal flexibility, the rate in modal flexibility and the change in the modal flexibility curvature, were valid to some extent.However, these indicators need the flexibility matrix before and after damaging, were restricted to some extent in practical projects.In this paper, a new damage indicator was proposed based on damage flexibility curvature, which does not need the structure information before damaging.Two simulations, a simple beam and a two-span continuous beam, are utilized to verify the new indicator.Through the simulation results indicate that the damage location in structures, with single damage, multiple ones and slighter ones, can be detected efficiently.The value of the indicator is increased with the damage severity, the damage severity can be qualitatively detected.Anti-noise performance of the new damage indicator is better.
2013, 43(8): 19-23.
doi: 10.13204/j.gyjz201308004
Abstract:
Most existing damage detection methods based on curvature should investigate the indicator value changes between the intact and damaged state.However, the 'footprint' in the intact state is usually not available for most actual beams.Therefore, a new damage localization indicator called difference of nearby difference curvature indicator(DNDCI) was introduced for single-span beams.This indicator does not require prior information of the intact beam and is sensitive to the damage occurs at or nearby the measuring points.Practical application method of DNDCI was proposed.Three methods for improving robustness were also proposed.Besides the idealized simply supported beams, it was validated by example that DNDCI is also applicable to the single-span beams supported by bearings.
Most existing damage detection methods based on curvature should investigate the indicator value changes between the intact and damaged state.However, the 'footprint' in the intact state is usually not available for most actual beams.Therefore, a new damage localization indicator called difference of nearby difference curvature indicator(DNDCI) was introduced for single-span beams.This indicator does not require prior information of the intact beam and is sensitive to the damage occurs at or nearby the measuring points.Practical application method of DNDCI was proposed.Three methods for improving robustness were also proposed.Besides the idealized simply supported beams, it was validated by example that DNDCI is also applicable to the single-span beams supported by bearings.
2013, 43(8): 24-28.
doi: 10.13204/j.gyjz201308005
Abstract:
The structural performance degradation and the size and location of damage are determined by structural vibration test and wavelet packet energy spectrum, which can be used for the early damage warning of large ancient wood frame architectures.The acceleration signal of dynamic response is obtained by finite element simulation, the change of signal energy spectrum is obtained to evaluate the structural damage state.It is concluded that the structural natural frequencies are not sensitive to the plane ancient wood frame structure, it is difficult to determine the damage location.With the increase of damage degree, the change of signal energy spectrum increases, which can describe the structural damage state qualitatively and quantitatively.The variation of wavelet sub-signal energy spectrum is related to the location of damage, it is shown that the damage degree is most sensitive to the joint of mortise and tenon, secondly in the midspan of beam, finally in the bottom of column.
The structural performance degradation and the size and location of damage are determined by structural vibration test and wavelet packet energy spectrum, which can be used for the early damage warning of large ancient wood frame architectures.The acceleration signal of dynamic response is obtained by finite element simulation, the change of signal energy spectrum is obtained to evaluate the structural damage state.It is concluded that the structural natural frequencies are not sensitive to the plane ancient wood frame structure, it is difficult to determine the damage location.With the increase of damage degree, the change of signal energy spectrum increases, which can describe the structural damage state qualitatively and quantitatively.The variation of wavelet sub-signal energy spectrum is related to the location of damage, it is shown that the damage degree is most sensitive to the joint of mortise and tenon, secondly in the midspan of beam, finally in the bottom of column.
2013, 43(8): 29-33,23.
doi: 10.13204/j.gyjz201308006
Abstract:
Through a four-story steel frame model experiment under enviromental excitation, the displacement response of each measuring point was recorded, and five time domain methods(the ITD method, STD method, the complex index method, the ERA method and the stochastic subspace method) were used to identify the modal parameters.An acceptable and satisfying result shows that all the methods can be applied to the building structure.The 5 methods have higher precision for identifying frequency, and have relative lower precision for damping ratio.Compared with STD method and the complex index method, the Stochastic Subspace method and the ERA method have higher precision for identifying the model parameters, the ITD method has lower precision.
Through a four-story steel frame model experiment under enviromental excitation, the displacement response of each measuring point was recorded, and five time domain methods(the ITD method, STD method, the complex index method, the ERA method and the stochastic subspace method) were used to identify the modal parameters.An acceptable and satisfying result shows that all the methods can be applied to the building structure.The 5 methods have higher precision for identifying frequency, and have relative lower precision for damping ratio.Compared with STD method and the complex index method, the Stochastic Subspace method and the ERA method have higher precision for identifying the model parameters, the ITD method has lower precision.
2013, 43(8): 34-38.
doi: 10.13204/j.gyjz201308007
Abstract:
The structural damage which is caused by seismic excitation is cumulated with the increment of cyclic loading times.Based on the summary and analysis of domestic and overseas research on the storey damage models, the conclusion that the law of the storey damage evolution can be reflected better in the component level than in the overall structure level is presented.With the finite element program ABAQUS, the different degrees of damage produced by the change of the main design parameters of components such as the effect of floors and the axial-compression ratio are simulated.The law of the storey damage evolution affected by the component damage is revealed.And the storey damage model of RC frame structure is finally established.
The structural damage which is caused by seismic excitation is cumulated with the increment of cyclic loading times.Based on the summary and analysis of domestic and overseas research on the storey damage models, the conclusion that the law of the storey damage evolution can be reflected better in the component level than in the overall structure level is presented.With the finite element program ABAQUS, the different degrees of damage produced by the change of the main design parameters of components such as the effect of floors and the axial-compression ratio are simulated.The law of the storey damage evolution affected by the component damage is revealed.And the storey damage model of RC frame structure is finally established.
2013, 43(8): 39-42.
doi: 10.13204/j.gyjz201308008
Abstract:
A kind of damage identification method was proposed based on relative element stiffness coefficient.Damage index of structure was defined as the ratio of the variation of relative element stiffness to the undamaged one, relative element stiffness was a function of modal parameters.Then, utilizing the modal parameter, damage of structure can be identified clearly.On the basis of soft Simulink, a structure was used to demonstrate the feasibility of the presented method, the relative stiffness of damaged and undamaged structure was calculated, and then damage index was required as defined.The results showed that the method could efficiently identify the damage position and degree of structure.
A kind of damage identification method was proposed based on relative element stiffness coefficient.Damage index of structure was defined as the ratio of the variation of relative element stiffness to the undamaged one, relative element stiffness was a function of modal parameters.Then, utilizing the modal parameter, damage of structure can be identified clearly.On the basis of soft Simulink, a structure was used to demonstrate the feasibility of the presented method, the relative stiffness of damaged and undamaged structure was calculated, and then damage index was required as defined.The results showed that the method could efficiently identify the damage position and degree of structure.
2013, 43(8): 43-47,105.
doi: 10.13204/j.gyjz201308009
Abstract:
A fragility evaluation methodology for bridge is proposed, based on logistic regression model.The methodology incorporates randomness of structural physical parameters and statistical dependence among response values.Using Monte Carlo simulation and random time history analysis, randomness of structural physical parameters was considered.Statistical dependence among response values was plored by Beta-binomial distribution, then logistic regression model was set up to analyse structure fragility.A two-span continuous concrete girder bridge was used as an example to illustrate the approach.Structure physical parameters with design drawings were taken as mean, and an appropriate standard deviation was selected for Monte Carlo simulation which can obtain parameter samples.Random time history analysis was done to get the sample of maximum values of responses, moment estimation and least square were used to obtain respectively Beta-binomial distribution and the unknown parameters of the logistic regression model, then the structure fragility curve under each level failure state was got and compared with fragility curve based on cumulative limit state valve.The results show that the proposed method can achieve a conservative fragility estimation, and better ensure the rationality of the prediction results, providing theoretical evidence for bridge damage detection.
A fragility evaluation methodology for bridge is proposed, based on logistic regression model.The methodology incorporates randomness of structural physical parameters and statistical dependence among response values.Using Monte Carlo simulation and random time history analysis, randomness of structural physical parameters was considered.Statistical dependence among response values was plored by Beta-binomial distribution, then logistic regression model was set up to analyse structure fragility.A two-span continuous concrete girder bridge was used as an example to illustrate the approach.Structure physical parameters with design drawings were taken as mean, and an appropriate standard deviation was selected for Monte Carlo simulation which can obtain parameter samples.Random time history analysis was done to get the sample of maximum values of responses, moment estimation and least square were used to obtain respectively Beta-binomial distribution and the unknown parameters of the logistic regression model, then the structure fragility curve under each level failure state was got and compared with fragility curve based on cumulative limit state valve.The results show that the proposed method can achieve a conservative fragility estimation, and better ensure the rationality of the prediction results, providing theoretical evidence for bridge damage detection.
2013, 43(8): 48-51.
doi: 10.13204/j.gyjz201308010
Abstract:
According to the development background and the analysis of city renewal model of Barcelona, it was elaborated the measures of historical city preservation and coastal areas reconstruction, analyzed the significance of city renewal to urban development.It was also pointed out that cultural policy was the key to successful transformation of Barcelona, from establishing of cultural strategy planning, attaching importance to cultural facilities construction and positively holding cultural events, it was analyzed the role of cultural policy and proposed the inspiration and reference to the renewal of cities in China.
According to the development background and the analysis of city renewal model of Barcelona, it was elaborated the measures of historical city preservation and coastal areas reconstruction, analyzed the significance of city renewal to urban development.It was also pointed out that cultural policy was the key to successful transformation of Barcelona, from establishing of cultural strategy planning, attaching importance to cultural facilities construction and positively holding cultural events, it was analyzed the role of cultural policy and proposed the inspiration and reference to the renewal of cities in China.
2013, 43(8): 52-54.
doi: 10.13204/j.gyjz201308011
Abstract:
In recent years, there have been a lot of different projects, whose tasks are to remould the old plants and turn them into cultural industry parks.Through the design of Liangzhu Jade Cultural Industry Zone, it was put forword the design ideas of keeping traces of the old industry architectures, interrupting orders of the old architecture planning, reconstructing elevations of the old industry architectures and using new forms, so as to explore the general character and the individual character of such projects.
In recent years, there have been a lot of different projects, whose tasks are to remould the old plants and turn them into cultural industry parks.Through the design of Liangzhu Jade Cultural Industry Zone, it was put forword the design ideas of keeping traces of the old industry architectures, interrupting orders of the old architecture planning, reconstructing elevations of the old industry architectures and using new forms, so as to explore the general character and the individual character of such projects.
2013, 43(8): 55-58.
doi: 10.13204/j.gyjz201308012
Abstract:
Energy-saving of buildings can be achieved by the energy storage of phase change material, but the technology has not been widely used by now.Several design methods are introduced in this paper in order to save energy and get thermal comforts.Using phase change material may create a positive effect in buildings'saving energy and have a bright future.
Energy-saving of buildings can be achieved by the energy storage of phase change material, but the technology has not been widely used by now.Several design methods are introduced in this paper in order to save energy and get thermal comforts.Using phase change material may create a positive effect in buildings'saving energy and have a bright future.
STUDY ON ULTIMATE BOND STRENGTH AND ANCHORAGE LENGTH OF THE REBAR IN THE RECYCLED AGGREGATE CONCRETE
2013, 43(8): 59-63,38.
doi: 10.13204/j.gyjz201308013
Abstract:
According to the pull out test, this paper analyzed the influence factors which include the recycled aggregate replacement ratio, type of the rebar and strength grade of recycled concrete on ultimate bond strength and gave the formula to calculate the ultimate bond strength.Analysis shows that the calculated values agree well with the experimental results.The different research results for the influence of the recycled aggregate replacement ratio on the ultimate bond strength were analyzed comparatively, and the analysis shows that the recycled aggregate replacement ratio cannot be used as the only influence factor to analyze the influence on bond performance of the recycled aggregate and also need to consider the material performance of the recycled aggregate and the coupling effects between the recycled aggregate and the coarse aggregate.The increasing coefficient of ultimate bond strength was defined, and analysis shows that influence level of the rebar type is greatest, followed by diameter of the rebar, the influence level of the strength grade is least, and the ultimate bond strength of ordinary concrete is generally slightly larger than the recycled concrete when the recycled aggregate replacement rate is 100%.Finally, the suggested method which can determine the anchorage length was proposed.
According to the pull out test, this paper analyzed the influence factors which include the recycled aggregate replacement ratio, type of the rebar and strength grade of recycled concrete on ultimate bond strength and gave the formula to calculate the ultimate bond strength.Analysis shows that the calculated values agree well with the experimental results.The different research results for the influence of the recycled aggregate replacement ratio on the ultimate bond strength were analyzed comparatively, and the analysis shows that the recycled aggregate replacement ratio cannot be used as the only influence factor to analyze the influence on bond performance of the recycled aggregate and also need to consider the material performance of the recycled aggregate and the coupling effects between the recycled aggregate and the coarse aggregate.The increasing coefficient of ultimate bond strength was defined, and analysis shows that influence level of the rebar type is greatest, followed by diameter of the rebar, the influence level of the strength grade is least, and the ultimate bond strength of ordinary concrete is generally slightly larger than the recycled concrete when the recycled aggregate replacement rate is 100%.Finally, the suggested method which can determine the anchorage length was proposed.
2013, 43(8): 64-68,74.
doi: 10.13204/j.gyjz201308014
Abstract:
The article introduces a technology of applying X-shaped steel mesh combined with high-strength mortar in the reinforcement of brick walls.Then an experiment was conducted to test the effect after the reinforcement under low-cyclic loading.It analysed was the hysteretic characteristics, failure mode, energy dissipation and shear resistance of brick walls with this strengthening method.And the influence of using X-shaped steel mesh combined with high-strength mortar on the seismic behavior of the brick walls was also discussed.The tests show that using this strengthening method can make the walls own a high degree of ultimate shear strength, and greatly improve the walls' ability to resist earthquake forces.Structural deformation and capacity of energy dissipation can also be increased.
The article introduces a technology of applying X-shaped steel mesh combined with high-strength mortar in the reinforcement of brick walls.Then an experiment was conducted to test the effect after the reinforcement under low-cyclic loading.It analysed was the hysteretic characteristics, failure mode, energy dissipation and shear resistance of brick walls with this strengthening method.And the influence of using X-shaped steel mesh combined with high-strength mortar on the seismic behavior of the brick walls was also discussed.The tests show that using this strengthening method can make the walls own a high degree of ultimate shear strength, and greatly improve the walls' ability to resist earthquake forces.Structural deformation and capacity of energy dissipation can also be increased.
2013, 43(8): 69-74.
doi: 10.13204/j.gyjz201308015
Abstract:
Bamboo roof structure has many advantages, such as low cost, fast construction speed, strong and durable use and flexible design, which can be widely used for businesses buildings, school buildings and residential buildings etc.So far, the study of bamboo structure is still at the initial stage, especially, performance of bamboo roof is still unknown.Six full-scale model trusses with two types of configuration and sizes were tested to failure under gradually increased vertical load.The load-deformlation curves and the failure mode of the two roof trusses were obtained through the tests;and the main factors influencing their bearing capacity were also analyzed.
Bamboo roof structure has many advantages, such as low cost, fast construction speed, strong and durable use and flexible design, which can be widely used for businesses buildings, school buildings and residential buildings etc.So far, the study of bamboo structure is still at the initial stage, especially, performance of bamboo roof is still unknown.Six full-scale model trusses with two types of configuration and sizes were tested to failure under gradually increased vertical load.The load-deformlation curves and the failure mode of the two roof trusses were obtained through the tests;and the main factors influencing their bearing capacity were also analyzed.
2013, 43(8): 75-78,54.
doi: 10.13204/j.gyjz201308016
Abstract:
Xinjiang Poplar is endemic to Xinjiang and is widely used in Xinjiang, but there are less researches on the Xinjiang Poplar.It was studied the flexural behavior of Xinjiang Poplar beam, and the basic mechanical properties, moisture content, tensile strength, compressive strength perpendicular to the grain of Xinjiang Poplar were measured.The bending tests of 5 Xinjiang Poplar beams of rectangular cross-section were done to verify the plane section assumption, and the Xinjiang Poplar timber beam's relationships among failure characteristics, ultimate load, load-strain, load-deflection etc were obtained.
Xinjiang Poplar is endemic to Xinjiang and is widely used in Xinjiang, but there are less researches on the Xinjiang Poplar.It was studied the flexural behavior of Xinjiang Poplar beam, and the basic mechanical properties, moisture content, tensile strength, compressive strength perpendicular to the grain of Xinjiang Poplar were measured.The bending tests of 5 Xinjiang Poplar beams of rectangular cross-section were done to verify the plane section assumption, and the Xinjiang Poplar timber beam's relationships among failure characteristics, ultimate load, load-strain, load-deflection etc were obtained.
2013, 43(8): 79-82,89.
doi: 10.13204/j.gyjz201308017
Abstract:
A model consisting of a system of nonlinear differential equations, named block model, was constructed to study the local curvature between two adjacent cracks.Utilizing this model, the deflections at the midspan in 10 RC beams bonded with external CFRP were simulated when the distance between two consecutive cracks was the maximum crack spacing 2Lb and minimum crack spacing Lb, which could be obtained from cracking analysis based on bond stress and slip.Comparisons between the simulated midspan deflection and that of experiment indicate that the proposed nonlinear model is able to predict the deformability behavior of RC beams strengthened with external CFRP sheets.Furthermore, the results indicate that the crack distribution has little influence on deflection of beam, so the traditional approach called moment-average curvature is reasonable to calculate the deflection of beam in practice.
A model consisting of a system of nonlinear differential equations, named block model, was constructed to study the local curvature between two adjacent cracks.Utilizing this model, the deflections at the midspan in 10 RC beams bonded with external CFRP were simulated when the distance between two consecutive cracks was the maximum crack spacing 2Lb and minimum crack spacing Lb, which could be obtained from cracking analysis based on bond stress and slip.Comparisons between the simulated midspan deflection and that of experiment indicate that the proposed nonlinear model is able to predict the deformability behavior of RC beams strengthened with external CFRP sheets.Furthermore, the results indicate that the crack distribution has little influence on deflection of beam, so the traditional approach called moment-average curvature is reasonable to calculate the deflection of beam in practice.
2013, 43(8): 83-89.
doi: 10.13204/j.gyjz201308018
Abstract:
The cumulated axial strain and vibration number curves were obtained through a series of dynamic triaxial tests under different dynamic stress amplitudes, confining pressures and moisture contents.The dynamic strain of link structural potential parameter(mN1), dynamic strain of friction structural potential parameter(mN2), total dynamic strain structural potential parameter(mN) were defined according to the soil structural research results and theories.The relationships among the structural parameters and tests conditions were discussed when the structural strength of aeolian soil's was destroyed.The research results showed that mN1 decreased with vibration numbers increasing, but the mN2 and mN would increased with the vibration numbers increasing.All kinds of structural parameters changed rapidly when vibration numbers were few, which showed that structural damages of aeolian soil were severe at primary vibration step.The larger dynamic stress amplitudes and moisture contents were, the larger the link stable structural dynamic strain potential parameter mfN1, the friction stable structural dynamic strain potential parameter mfN2were, and the total stable dynamic strain structural potential parameter mfN but opposite to confining pressures.The new method to determine the dynamic strength of aeolian soil was established based on the relationship between the total dynamic strain structural potential parameters and vibration numbers.
The cumulated axial strain and vibration number curves were obtained through a series of dynamic triaxial tests under different dynamic stress amplitudes, confining pressures and moisture contents.The dynamic strain of link structural potential parameter(mN1), dynamic strain of friction structural potential parameter(mN2), total dynamic strain structural potential parameter(mN) were defined according to the soil structural research results and theories.The relationships among the structural parameters and tests conditions were discussed when the structural strength of aeolian soil's was destroyed.The research results showed that mN1 decreased with vibration numbers increasing, but the mN2 and mN would increased with the vibration numbers increasing.All kinds of structural parameters changed rapidly when vibration numbers were few, which showed that structural damages of aeolian soil were severe at primary vibration step.The larger dynamic stress amplitudes and moisture contents were, the larger the link stable structural dynamic strain potential parameter mfN1, the friction stable structural dynamic strain potential parameter mfN2were, and the total stable dynamic strain structural potential parameter mfN but opposite to confining pressures.The new method to determine the dynamic strength of aeolian soil was established based on the relationship between the total dynamic strain structural potential parameters and vibration numbers.
2013, 43(8): 90-93,14.
doi: 10.13204/j.gyjz201308019
Abstract:
A series of direct shear tests on coarse-grained soil were performed by large multi-function interface shear apparatus.Two sets of comparative shear tests on special sample with particle diameters of 20~50 mm and 10~20 mm were also performed.Then, the mechanical behaviors and strength parameters of coarse-grained soil were analyzed.After the tests were over, all the samples were sieved, and the particle crushing laws were concluded.The results showed that the coarse-grained soil in shearing tests was a hardening material.The non-linear behaviors in strength and sham cohesions in bad gradation samples were observed.However, there were few changes in frictional strength.The sieving results showed that crushing rates increased obviously with the increasing normal stresses.There were hyperbolic connections between crushing rates and normal stresses.Their fitting parameters were closely related to gradations and particle sizes of the samples.
A series of direct shear tests on coarse-grained soil were performed by large multi-function interface shear apparatus.Two sets of comparative shear tests on special sample with particle diameters of 20~50 mm and 10~20 mm were also performed.Then, the mechanical behaviors and strength parameters of coarse-grained soil were analyzed.After the tests were over, all the samples were sieved, and the particle crushing laws were concluded.The results showed that the coarse-grained soil in shearing tests was a hardening material.The non-linear behaviors in strength and sham cohesions in bad gradation samples were observed.However, there were few changes in frictional strength.The sieving results showed that crushing rates increased obviously with the increasing normal stresses.There were hyperbolic connections between crushing rates and normal stresses.Their fitting parameters were closely related to gradations and particle sizes of the samples.
2013, 43(8): 94-97.
doi: 10.13204/j.gyjz201308020
Abstract:
Prestressed concrete pipe pile is applied widely.Pipe pile and pile cap joints are structural weaknesses that can easily break under a earthquake, thus resulting in serious consequences.By changing the connection form of a pipe pile and pile cap, and imposing cyclic loading on the structure to simulated seismic wave, it was studied on pipe pile load-displacement hysteresis, ductility etc.Test results showed that adding non-prestressed rebar within the filled pipe pile could increase evidently the bearing capacity of pipe piles;and using to non-prestressed rebar dowels inserted at an angle in the connection between the cap and pipe pile could have a great improvement on the structural ductility and seismic energy dissipation of the joint.
Prestressed concrete pipe pile is applied widely.Pipe pile and pile cap joints are structural weaknesses that can easily break under a earthquake, thus resulting in serious consequences.By changing the connection form of a pipe pile and pile cap, and imposing cyclic loading on the structure to simulated seismic wave, it was studied on pipe pile load-displacement hysteresis, ductility etc.Test results showed that adding non-prestressed rebar within the filled pipe pile could increase evidently the bearing capacity of pipe piles;and using to non-prestressed rebar dowels inserted at an angle in the connection between the cap and pipe pile could have a great improvement on the structural ductility and seismic energy dissipation of the joint.
DISSCUSSION ABOUT VIBRATION COMPUTATION OF SPACE FRAME FOUNDATION REGARDED AS PLANE FRAME FOUNDATION
2013, 43(8): 98-100,18.
doi: 10.13204/j.gyjz201308021
Abstract:
It was shown by computing that the computation model of space frame foundation under a machine at a range of 1 000~3 000 r/min, which was a simplified plane frame foundation would result in a great error.Therefore, it was suggested that simplified plane frame model should not be adopted in designing.
It was shown by computing that the computation model of space frame foundation under a machine at a range of 1 000~3 000 r/min, which was a simplified plane frame foundation would result in a great error.Therefore, it was suggested that simplified plane frame model should not be adopted in designing.
2013, 43(8): 101-105.
doi: 10.13204/j.gyjz201308022
Abstract:
The experiments of the mixing of macro-synthetic fibers and polypropylene fibers, the mixing of steel fibers and macro-synthetic fibers reinforced shotcrete on the compressive strength and flexural strength were carried out, whose mechanical properties were compared with those of baseline group and single fibers group, The results show that the compressive strength, flexural strength, flexural compression ratio of hybrid fibers shotcrete are more obviously improved than those of single fibers shotcrete, and it can give full play to the superimposed effect.When the mixing contents are 0.7% of steel fibers and 0.3% of macro-synthetic fibers, the strength and flexural compression ratio of shotcrete are the best, and it is effective to make up for the disadvantages of steel fiber with its easy rust, heavy weight and high cost etc.
The experiments of the mixing of macro-synthetic fibers and polypropylene fibers, the mixing of steel fibers and macro-synthetic fibers reinforced shotcrete on the compressive strength and flexural strength were carried out, whose mechanical properties were compared with those of baseline group and single fibers group, The results show that the compressive strength, flexural strength, flexural compression ratio of hybrid fibers shotcrete are more obviously improved than those of single fibers shotcrete, and it can give full play to the superimposed effect.When the mixing contents are 0.7% of steel fibers and 0.3% of macro-synthetic fibers, the strength and flexural compression ratio of shotcrete are the best, and it is effective to make up for the disadvantages of steel fiber with its easy rust, heavy weight and high cost etc.
2013, 43(8): 106-108.
doi: 10.13204/j.gyjz201308023
Abstract:
High-formwork supports' collapse always occur during the construction process.Through the field investigation and measurement of the supports for 15 m high-formwork, the erection parameters of high-formwork supports were obtained.It was found that there was a larger randomness during the erection of high-formwork supports, to implement full process management for the structure erection, and ensure the consistency of actual erection parameters and special construction scheme.The results show that the stress value of the pole is less than the pre-analysis pole stress, thus reflecting that the load combination proposed by Technical Code for Safety of Coupler Stell Tube Falsework in Construction of Buildings(JGJ 130-2011) is too conservative.the stress of the bottom is greater than the top on the same pole, which proved there is some regulation in horizontal bar and vertical double bridging.The pole stress associated with the height of the frame body, the higher the height of the formwork support, the greater the difference between the bottom and the top of the stress.The results provide data for the design of formwork supports.
High-formwork supports' collapse always occur during the construction process.Through the field investigation and measurement of the supports for 15 m high-formwork, the erection parameters of high-formwork supports were obtained.It was found that there was a larger randomness during the erection of high-formwork supports, to implement full process management for the structure erection, and ensure the consistency of actual erection parameters and special construction scheme.The results show that the stress value of the pole is less than the pre-analysis pole stress, thus reflecting that the load combination proposed by Technical Code for Safety of Coupler Stell Tube Falsework in Construction of Buildings(JGJ 130-2011) is too conservative.the stress of the bottom is greater than the top on the same pole, which proved there is some regulation in horizontal bar and vertical double bridging.The pole stress associated with the height of the frame body, the higher the height of the formwork support, the greater the difference between the bottom and the top of the stress.The results provide data for the design of formwork supports.
2013, 43(8): 109-113.
doi: 10.13204/j.gyjz201308024
Abstract:
Based on the tests of 9 steel reinforced recycled concrete eccentric compression columns with different recycled coarse aggregate replacement percentages and relative eccentricity under eccentric compression, the failure feature and change rule of lateral deflection of eccentric compression columns were investigated.The test results show that the stiffness of steel reinforced recycled concrete eccentric compression columns varies under different stages and has influences on the deformation feature of eccentric compression columns.The maximum deflection of steel reinforced recycled concrete eccentric compression columns increases with the increase of recycled coarse aggregate replacement percentages and relative eccentricity.Based on the test results and the simplified mechanical model of eccentric compression columns, the calculation formula of lateral deflection was derived and the calculation formula of stiffness of eccentric compression columns was also proposed.It is shown that the maximum lateral deflection calculated by the proposed formulas is in good agreement with the test value and can satisfy the calculated requirements.
Based on the tests of 9 steel reinforced recycled concrete eccentric compression columns with different recycled coarse aggregate replacement percentages and relative eccentricity under eccentric compression, the failure feature and change rule of lateral deflection of eccentric compression columns were investigated.The test results show that the stiffness of steel reinforced recycled concrete eccentric compression columns varies under different stages and has influences on the deformation feature of eccentric compression columns.The maximum deflection of steel reinforced recycled concrete eccentric compression columns increases with the increase of recycled coarse aggregate replacement percentages and relative eccentricity.Based on the test results and the simplified mechanical model of eccentric compression columns, the calculation formula of lateral deflection was derived and the calculation formula of stiffness of eccentric compression columns was also proposed.It is shown that the maximum lateral deflection calculated by the proposed formulas is in good agreement with the test value and can satisfy the calculated requirements.
2013, 43(8): 114-119,137.
doi: 10.13204/j.gyjz201308025
Abstract:
In order to study the shear behavior of the steel recycled aggregate concrete short columns and popularize the application of recycled concrete in engineering, the numerical simulations of the shear behavior of 8 steel recycled aggregate concrete short columns under low-cyclic reversed loading were carried out by OpenSees Program based on the flexure-shear interaction displacement-based beam-column element and fiber section.The influence regularity of recycled aggregate replacement ratio, axial compression ratio and volumetric stirrup ratio on the shear behavior of the steel recycled aggregate concrete short columns was analyzed.The results indicate that the shear behavior of steel recycled aggregate concrete short columns is close to that of the steel reinforced concrete short columns, and axial compression ratio and volumetric stirrup ratio have a obvious influence on the shear behavior of the steel recycled aggregate concrete short columns.Non-linear response of the steel recycled aggregate concrete short columns under the combination of compression, bending and shearing action can be simulated by means of OpenSees Program.
In order to study the shear behavior of the steel recycled aggregate concrete short columns and popularize the application of recycled concrete in engineering, the numerical simulations of the shear behavior of 8 steel recycled aggregate concrete short columns under low-cyclic reversed loading were carried out by OpenSees Program based on the flexure-shear interaction displacement-based beam-column element and fiber section.The influence regularity of recycled aggregate replacement ratio, axial compression ratio and volumetric stirrup ratio on the shear behavior of the steel recycled aggregate concrete short columns was analyzed.The results indicate that the shear behavior of steel recycled aggregate concrete short columns is close to that of the steel reinforced concrete short columns, and axial compression ratio and volumetric stirrup ratio have a obvious influence on the shear behavior of the steel recycled aggregate concrete short columns.Non-linear response of the steel recycled aggregate concrete short columns under the combination of compression, bending and shearing action can be simulated by means of OpenSees Program.
2013, 43(8): 120-124,97.
doi: 10.13204/j.gyjz201308026
Abstract:
Taking side-plate reinforced joint as the research object, this study simulated transient welding process for the connecting weld between side-plate and beam flange.Based on above research, the effects of residual stress at the joint of the side plate and beam flange on plastic equivalent strain index and rupture index were analyzed according to the two models either with or without welding residual stress.The results show that welding residual stress affects obviously the brittle fracture possibility of the joint, and the position where a brittle fracture can easily occur is also found out.
Taking side-plate reinforced joint as the research object, this study simulated transient welding process for the connecting weld between side-plate and beam flange.Based on above research, the effects of residual stress at the joint of the side plate and beam flange on plastic equivalent strain index and rupture index were analyzed according to the two models either with or without welding residual stress.The results show that welding residual stress affects obviously the brittle fracture possibility of the joint, and the position where a brittle fracture can easily occur is also found out.
2013, 43(8): 125-132.
doi: 10.13204/j.gyjz201308027
Abstract:
The shells of stepped wall cylinders are widely used for cylindrical containment structures, such as vertical-axis tanks and silos.Buckling failures can easily occur on these structures under external pressures when they are empty or partial empty.Their buckling modes may have several forms due to complicated changes in wall thickness.Hencr how to determine accurately the buckling mode of cylinder wall is a difficult issue in design of such structures.It was introduced a new weighted mean thickness method.Buckling predictions were made using the new hand calculation method and compared both with accurate predictions from finite element calculations using ABAQUS and with the current Eurocode rules.The comparison shows that the weighted mean thickness method provides a precise evaluation of the external buckling strength and modes of stepped wall cylinders for a wide range of short and medium-length shells.
The shells of stepped wall cylinders are widely used for cylindrical containment structures, such as vertical-axis tanks and silos.Buckling failures can easily occur on these structures under external pressures when they are empty or partial empty.Their buckling modes may have several forms due to complicated changes in wall thickness.Hencr how to determine accurately the buckling mode of cylinder wall is a difficult issue in design of such structures.It was introduced a new weighted mean thickness method.Buckling predictions were made using the new hand calculation method and compared both with accurate predictions from finite element calculations using ABAQUS and with the current Eurocode rules.The comparison shows that the weighted mean thickness method provides a precise evaluation of the external buckling strength and modes of stepped wall cylinders for a wide range of short and medium-length shells.
2013, 43(8): 133-137.
doi: 10.13204/j.gyjz201308028
Abstract:
To realize the design objective of no transit, the elevated light railway Line 4 and Line 6 go through Shenzhen North Railway Station.The vibration due to light railway acts on the railway station building directly, and the other parts of the station building.And it will maybe influence the comfort level of the passengers in the waiting hall and the service performance of additional facilities in station.In the station structural design process, the dynamic responses of vehicle-building structure couple system for Shenzhen North Railway Station under the action of light railway Line 4 and Line 6 were studied.The vehicle brake forces time histories were acted on the station building structure, considering the train irregularity and the cases of single train braking, double train braking and 4 Lines braking.The analysis of vibration was focused on the acceleration response of station building.The results showed that vibration effects could meet the requirement of passengerscomforts.
To realize the design objective of no transit, the elevated light railway Line 4 and Line 6 go through Shenzhen North Railway Station.The vibration due to light railway acts on the railway station building directly, and the other parts of the station building.And it will maybe influence the comfort level of the passengers in the waiting hall and the service performance of additional facilities in station.In the station structural design process, the dynamic responses of vehicle-building structure couple system for Shenzhen North Railway Station under the action of light railway Line 4 and Line 6 were studied.The vehicle brake forces time histories were acted on the station building structure, considering the train irregularity and the cases of single train braking, double train braking and 4 Lines braking.The analysis of vibration was focused on the acceleration response of station building.The results showed that vibration effects could meet the requirement of passengerscomforts.
2013, 43(8): 138-143,132.
doi: 10.13204/j.gyjz201308029
Abstract:
The Auditorium of Tsinghua University, built in 1917, is a major historical and cultural site protected at the national level.Before Tsinghua's centennial anniversary in 2011, the auditorium had been comprehensively reinforced and repaired which aims to make up the defects and deficiencies of the original design and bring overall optimization through reinforcing the structure, replacing deteriorated features, enhancing enjoyment of the performance, adjusting acoustic environment, utilizing the underground space, exhibiting the historical heritage, improving the outdoor environment, etc.Meanwhile, the strengthening and reconstruction work tried to maintain the auditorium's original appearance and make the historical building adapt to modern functions and multiple activities' demands from faculty and students.
The Auditorium of Tsinghua University, built in 1917, is a major historical and cultural site protected at the national level.Before Tsinghua's centennial anniversary in 2011, the auditorium had been comprehensively reinforced and repaired which aims to make up the defects and deficiencies of the original design and bring overall optimization through reinforcing the structure, replacing deteriorated features, enhancing enjoyment of the performance, adjusting acoustic environment, utilizing the underground space, exhibiting the historical heritage, improving the outdoor environment, etc.Meanwhile, the strengthening and reconstruction work tried to maintain the auditorium's original appearance and make the historical building adapt to modern functions and multiple activities' demands from faculty and students.
2013, 43(8): 144-149,9.
doi: 10.13204/j.gyjz201308030
Abstract:
Adding steel storeys on the top of the original structure is widely used in practice, for the lightness and superior anti-seismic properties.Taking the case of adding storey of high-rise steel garage and retrofit project, it was explained the strain energy methods that are applied to the calculation of damping ratio of steel-concrete mixed structure, and the comparison of the structural internal force and deformation according to different values of damping ratio.In addition, the design of anti-seismic and retrofit of corresponding parts of structure were also expounded.
Adding steel storeys on the top of the original structure is widely used in practice, for the lightness and superior anti-seismic properties.Taking the case of adding storey of high-rise steel garage and retrofit project, it was explained the strain energy methods that are applied to the calculation of damping ratio of steel-concrete mixed structure, and the comparison of the structural internal force and deformation according to different values of damping ratio.In addition, the design of anti-seismic and retrofit of corresponding parts of structure were also expounded.
2013, 43(8): 150-153,169.
doi: 10.13204/j.gyjz201308031
Abstract:
The causes of frame column through defect in a project were analyzed, and partial structural model was set up for numerical analysis under different load conditions, so as to determine the influence on inner forces of joining structural member caused by the frame column through defect.On this basis, the reliability of the structure was assessed to work out a strengthening scheme using carbon fiber composite, whose strengthening effect was very good.The analytic results indicate that the greater change would occur in the inner forces of joining structural member when frame column has through defect, and the structure could not meet requirement of earthquake proofing construction and potential safety hazard existed.Frame column has through defect should be strengthened in time, and need take effective measures should be taken to assure structure safety in work progress, at the same time, strengthening effect should be detected for assessing whether the strengthened structure meet the design requirement.
The causes of frame column through defect in a project were analyzed, and partial structural model was set up for numerical analysis under different load conditions, so as to determine the influence on inner forces of joining structural member caused by the frame column through defect.On this basis, the reliability of the structure was assessed to work out a strengthening scheme using carbon fiber composite, whose strengthening effect was very good.The analytic results indicate that the greater change would occur in the inner forces of joining structural member when frame column has through defect, and the structure could not meet requirement of earthquake proofing construction and potential safety hazard existed.Frame column has through defect should be strengthened in time, and need take effective measures should be taken to assure structure safety in work progress, at the same time, strengthening effect should be detected for assessing whether the strengthened structure meet the design requirement.
2013, 43(8): 154-156.
doi: 10.13204/j.gyjz201308032
Abstract:
Through introducing the idea of the integration into the design of thermal source plant's coal handling system, so as to design a unique system called integrated coal bunker(ICB), which integrates 20 single buildings of coal handling system in one building.The ICB has fully developed and utilized the three-dimensional space of the architecture, realizing the purpose of coal handling system's covering the fewest area, function's integration and artistic appearance.The ICB has also improved the efficiency of land use and reduced the cost of investment.Furthermore, it can lower the operating cost, improve the image of the thermal source plant and beautify the environment.The ICB can be used as an independent module applied to the design of other thermal power plants.
Through introducing the idea of the integration into the design of thermal source plant's coal handling system, so as to design a unique system called integrated coal bunker(ICB), which integrates 20 single buildings of coal handling system in one building.The ICB has fully developed and utilized the three-dimensional space of the architecture, realizing the purpose of coal handling system's covering the fewest area, function's integration and artistic appearance.The ICB has also improved the efficiency of land use and reduced the cost of investment.Furthermore, it can lower the operating cost, improve the image of the thermal source plant and beautify the environment.The ICB can be used as an independent module applied to the design of other thermal power plants.
2013, 43(8): 157-160,28.
doi: 10.13204/j.gyjz201308033
Abstract:
According to the actual project, using Ecotect Analysis 2010 software, this paper did the architecture physical environment performance-based evaluation from three different aspects of the overall layout, the building monomer and the detailed structure.By comparing the results of the analysis of different architectural forms, the specific architectural forms to adapt to the local climate were proposed as the basis of the program design phase.
According to the actual project, using Ecotect Analysis 2010 software, this paper did the architecture physical environment performance-based evaluation from three different aspects of the overall layout, the building monomer and the detailed structure.By comparing the results of the analysis of different architectural forms, the specific architectural forms to adapt to the local climate were proposed as the basis of the program design phase.
2013, 43(8): 161-164,58.
doi: 10.13204/j.gyjz201308034
Abstract:
It is always thought that the relationship between nature and architectural environment has been opposed.Architects have already recognized their responsibility for weak ecological environment that had been damaged severely.Ebenezer Howard's Garden Cities of Tomorrow showed the social order that he wanted to build and fused with environment tightly, which supplied principles of sustainable development for architects.The renewed sustainable garden city based on Howard's Garden City does not seek for the balance of constructive factors in city simply and isolatedly, but uses city's plan to solve crisis of city's ecological system, and maintain its health and development.
It is always thought that the relationship between nature and architectural environment has been opposed.Architects have already recognized their responsibility for weak ecological environment that had been damaged severely.Ebenezer Howard's Garden Cities of Tomorrow showed the social order that he wanted to build and fused with environment tightly, which supplied principles of sustainable development for architects.The renewed sustainable garden city based on Howard's Garden City does not seek for the balance of constructive factors in city simply and isolatedly, but uses city's plan to solve crisis of city's ecological system, and maintain its health and development.
2013, 43(8): 165-169.
doi: 10.13204/j.gyjz201308035
Abstract:
In information age, information technology has a profound impact on the design of cinema building.Based on some contemporary typical cinemas at home and abroad, it was discussed the layout, the design of humanization space and stylization exterior and the intelligent management model of cinemas age, in information age, in order to provide a reference for the design of cinema buildings in the future.
In information age, information technology has a profound impact on the design of cinema building.Based on some contemporary typical cinemas at home and abroad, it was discussed the layout, the design of humanization space and stylization exterior and the intelligent management model of cinemas age, in information age, in order to provide a reference for the design of cinema buildings in the future.
2013, 43(8): 170-172.
doi: 10.13204/j.gyjz201308036
Abstract:
It was presented a steel structure building for Bavarian Kings Museum that was rewarded with the awards of German steel structure engineer and German steel structure building in 2013.The building was of innovative design, reasonable structure, low cost and friendly environment.The project fully reflected the characteristic of steel structure in novel building type, high quality, convenient construction and reasonable cost.
It was presented a steel structure building for Bavarian Kings Museum that was rewarded with the awards of German steel structure engineer and German steel structure building in 2013.The building was of innovative design, reasonable structure, low cost and friendly environment.The project fully reflected the characteristic of steel structure in novel building type, high quality, convenient construction and reasonable cost.
