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2015 Vol. 45, No. 2
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2015, 45(2): 1-4.
doi: 10.13204/j.gyjz201502001
Abstract:
The fast freeze-thaw tests with fresh water on high strength concrete ( C60 ) with fly ash or slag and composite admixture，as well as the one without admixtures were conducted． The results showed that for the concrete with admixtures ( slag and fly ash) ，the mass-loss rate was the smallest and the relative dynamic modulus of elasticity was reduced slowest，meanwhile the surface was denuded slightest，indicating a best freezing-thawing resistance performance．For the concrete with 50% slag and concrete without mineral admixtures，the mass-loss rate，the relative dynamic modulus of elasticity and the surface denudation were about the same，meanwhile their freezingthawing resistance performance was a little worse than the concrete with admixtures ( slag and fly ash) ．For the concrete with 50% fly ash，the mass-loss rate and the relative dynamic modulus of elasticity reduced fastest，and the surface was denuded seriously，indicating a worst freezing-thawing resistance performance．
The fast freeze-thaw tests with fresh water on high strength concrete ( C60 ) with fly ash or slag and composite admixture，as well as the one without admixtures were conducted． The results showed that for the concrete with admixtures ( slag and fly ash) ，the mass-loss rate was the smallest and the relative dynamic modulus of elasticity was reduced slowest，meanwhile the surface was denuded slightest，indicating a best freezing-thawing resistance performance．For the concrete with 50% slag and concrete without mineral admixtures，the mass-loss rate，the relative dynamic modulus of elasticity and the surface denudation were about the same，meanwhile their freezingthawing resistance performance was a little worse than the concrete with admixtures ( slag and fly ash) ．For the concrete with 50% fly ash，the mass-loss rate and the relative dynamic modulus of elasticity reduced fastest，and the surface was denuded seriously，indicating a worst freezing-thawing resistance performance．
2015, 45(2): 5-9.
doi: 10.13204/j.gyjz201502002
Abstract:
The strength， the pore structure and freeze-proof durability of air-entrained concrete under 3 ℃ temperature curing and with different air contents were researched by taking air-entrained concrete under low temperature curing ( 3 0. 2) ℃ as the object，adopting strength test mercury intrusion method，pore analytical method and fast freeze-thaw method． The results showed that when concrete of 3 ℃ temperature curing，as the air content was increased，the distribution of pore diameter was uniform and the interior pore structure of concrete was improved significantly，however，the pore structure under the room curing at the same air content of concrete was lower than under 3 ℃ curing． In order to expound the influence of air content on the actual concrete strength in an even better fashion，the concrete compressive strength under 3 ℃ curing can further be estimated by pore structure， which was compared with the room curing actual compressive strength，showing the difference between the two．
The strength， the pore structure and freeze-proof durability of air-entrained concrete under 3 ℃ temperature curing and with different air contents were researched by taking air-entrained concrete under low temperature curing ( 3 0. 2) ℃ as the object，adopting strength test mercury intrusion method，pore analytical method and fast freeze-thaw method． The results showed that when concrete of 3 ℃ temperature curing，as the air content was increased，the distribution of pore diameter was uniform and the interior pore structure of concrete was improved significantly，however，the pore structure under the room curing at the same air content of concrete was lower than under 3 ℃ curing． In order to expound the influence of air content on the actual concrete strength in an even better fashion，the concrete compressive strength under 3 ℃ curing can further be estimated by pore structure， which was compared with the room curing actual compressive strength，showing the difference between the two．
2015, 45(2): 10-14.
doi: 10.13204/j.gyjz201502003
Abstract:
Steel and basalt hybrid fibers reinforced concrete technical route was proposed，through the freeze-thaw test， the influence of steel fiber mixed basalt fiber on the frost-resistance of concrete and freeze-thaw model were studied． The results showed that different fiber dosage had great influence on the frost-resistance of concrete，and when the volume fraction of steel fiber was 1. 5% and basalt fiber was 0. 05%，the frost-resistance of airport pavement concrete attain the level of F250． The freeze-thaw damage mechanism was analyzed，freeze-thaw damage models of hybrid fiber concrete were established by using relative dynamic modulus of elasticity and accumulative freeze-thaw damage，the model based on relative dynamic modulus of elasticity attenuation was superior to the one based on accumulative freezethaw damage，and quadratic function model had a higher fit accuracy as compared to exponential function model．
Steel and basalt hybrid fibers reinforced concrete technical route was proposed，through the freeze-thaw test， the influence of steel fiber mixed basalt fiber on the frost-resistance of concrete and freeze-thaw model were studied． The results showed that different fiber dosage had great influence on the frost-resistance of concrete，and when the volume fraction of steel fiber was 1. 5% and basalt fiber was 0. 05%，the frost-resistance of airport pavement concrete attain the level of F250． The freeze-thaw damage mechanism was analyzed，freeze-thaw damage models of hybrid fiber concrete were established by using relative dynamic modulus of elasticity and accumulative freeze-thaw damage，the model based on relative dynamic modulus of elasticity attenuation was superior to the one based on accumulative freezethaw damage，and quadratic function model had a higher fit accuracy as compared to exponential function model．
2015, 45(2): 15-18.
doi: 10.13204/j.gyjz201502004
Abstract:
In order to get the constitutive relationship model under freeze-thaw cycles for compression masonry，the promoted strain equivalence principle is applied to the masonry structures for the first time and the total damage of the masonry which withstand axial load after freeze-thaw cycles were equaled to the nonlinear coupling of the freeze-thaw damage and axial compression damage． Then based on the basic principles of damage mechanics and the nonhomogeneity of masonry microstructure，deterioration process and damage evolution route for the two damage states were analyzed，the total damage evolution equation of masonry withstanding axial compression after freeze-thaw cycles was derived，finally the constitutive relationship model under freeze-thaw cycles for compression masonry was established and was verified to be rational by existing test data．
In order to get the constitutive relationship model under freeze-thaw cycles for compression masonry，the promoted strain equivalence principle is applied to the masonry structures for the first time and the total damage of the masonry which withstand axial load after freeze-thaw cycles were equaled to the nonlinear coupling of the freeze-thaw damage and axial compression damage． Then based on the basic principles of damage mechanics and the nonhomogeneity of masonry microstructure，deterioration process and damage evolution route for the two damage states were analyzed，the total damage evolution equation of masonry withstanding axial compression after freeze-thaw cycles was derived，finally the constitutive relationship model under freeze-thaw cycles for compression masonry was established and was verified to be rational by existing test data．
2015, 45(2): 19-22.
doi: 10.13204/j.gyjz201502005
Abstract:
According to the temperature changes in cold region，the compressive strength and flexural strength tests of polymer cement mortar after 0，10，20 and 30 cycles under air freezing and air thawing ( air freezing) and air freezing and water thawing ( water freezing) were carried out with the temperature from －18 ℃ to 20 ℃ ( humidity of 90%) ． The effects of the freezing and thawing environment on polymer cement mortar mechanical properties of external thermal insulation composite systems were analyzed． And the effects of the freezing and thawing cycles and powder content( 1. 5%，2. 0% and 2. 5%) on polymer cement mortar compressive strength and flexural strength were also discussed． Therefore the rules of changing in the compressive strength and flexural strength under the freezing and thawing environment were obtained．
According to the temperature changes in cold region，the compressive strength and flexural strength tests of polymer cement mortar after 0，10，20 and 30 cycles under air freezing and air thawing ( air freezing) and air freezing and water thawing ( water freezing) were carried out with the temperature from －18 ℃ to 20 ℃ ( humidity of 90%) ． The effects of the freezing and thawing environment on polymer cement mortar mechanical properties of external thermal insulation composite systems were analyzed． And the effects of the freezing and thawing cycles and powder content( 1. 5%，2. 0% and 2. 5%) on polymer cement mortar compressive strength and flexural strength were also discussed． Therefore the rules of changing in the compressive strength and flexural strength under the freezing and thawing environment were obtained．
2015, 45(2): 23-26.
doi: 10.13204/j.gyjz201502006
Abstract:
Freezing and thawing while causing physical changes in the mechanical properties of concrete，it is bound to change the bond properties between concrete and steel． Center short buried specimens of three concrete strengths C30，C40 and C50 were subjected to the monotonic and cyclic loading tests，the effect of the freeze-thaw damage on concrete and plain bars bond stress-slip curve was studied，and the variation of the peak bond stress，peak slip and residual bond stress under monotonic loading was also analyzed，finally the relationship between the ultimate bond degradation rate and load cycles under cyclic loading was explored．
Freezing and thawing while causing physical changes in the mechanical properties of concrete，it is bound to change the bond properties between concrete and steel． Center short buried specimens of three concrete strengths C30，C40 and C50 were subjected to the monotonic and cyclic loading tests，the effect of the freeze-thaw damage on concrete and plain bars bond stress-slip curve was studied，and the variation of the peak bond stress，peak slip and residual bond stress under monotonic loading was also analyzed，finally the relationship between the ultimate bond degradation rate and load cycles under cyclic loading was explored．
2015, 45(2): 27-31.
doi: 10.13204/j.gyjz201502007
Abstract:
An experiment was carried out of five prestressed concrete beams after different cycles of freeze-thawing to investigate the impact law of freeze-thaw on the load bearing property of specimens． The test results showed that with the number of freeze-thaw increasing，the flexural failure process of specimens speeded up， the ultimate bearing capacity and crack resistance of the specimens gradually decreased，the limit deformation and ductility ability also decreased when the specimens damaged， the specimens had a brittle failure trend． Finite element analysis software ANSYS was used to simulate the bearing property of specimens after freeze-thaw，the results showed that the loaddeflection curve of numerical simulation mated with test results well，and the numerical model could truly reflect the load bearing property of the specimens after freeze-thaw．
An experiment was carried out of five prestressed concrete beams after different cycles of freeze-thawing to investigate the impact law of freeze-thaw on the load bearing property of specimens． The test results showed that with the number of freeze-thaw increasing，the flexural failure process of specimens speeded up， the ultimate bearing capacity and crack resistance of the specimens gradually decreased，the limit deformation and ductility ability also decreased when the specimens damaged， the specimens had a brittle failure trend． Finite element analysis software ANSYS was used to simulate the bearing property of specimens after freeze-thaw，the results showed that the loaddeflection curve of numerical simulation mated with test results well，and the numerical model could truly reflect the load bearing property of the specimens after freeze-thaw．
2015, 45(2): 32-37.
doi: 10.13204/j.gyjz201502008
Abstract:
In order to investigate the shear behaviors of RC beams after freeze-thaw cycles，compressive strength test of concrete cubes after 0，75，100，125，150 freeze-thaw cycles were made，and static shear experiment of 45 RC beams after 0，75，100，125，150 freeze-thaw cycles were also made． The relationships of relative compressive strength of concrete，mass loss rates，relative dynamic modulus of elasticity and freeze-thaw cycles were analyzed． The influences of different numbers of freeze-thaw cycles on the shear behaviors of RC beams with different stirrup spacing were studied． The results showed that concrete cubesmass，relative dynamic modulus of elasticity， relative compressive strength and relative tensile strength were decreased with the increasing of freeze-thaw cycles． Cracking loading and ultimate loading of shear beams were decreased with the increasing of freeze-thaw cycles． Current concrete structure design code about ultimate loading of shear beams is still suitable for RC beams after freeze-thaw cycles．
In order to investigate the shear behaviors of RC beams after freeze-thaw cycles，compressive strength test of concrete cubes after 0，75，100，125，150 freeze-thaw cycles were made，and static shear experiment of 45 RC beams after 0，75，100，125，150 freeze-thaw cycles were also made． The relationships of relative compressive strength of concrete，mass loss rates，relative dynamic modulus of elasticity and freeze-thaw cycles were analyzed． The influences of different numbers of freeze-thaw cycles on the shear behaviors of RC beams with different stirrup spacing were studied． The results showed that concrete cubesmass，relative dynamic modulus of elasticity， relative compressive strength and relative tensile strength were decreased with the increasing of freeze-thaw cycles． Cracking loading and ultimate loading of shear beams were decreased with the increasing of freeze-thaw cycles． Current concrete structure design code about ultimate loading of shear beams is still suitable for RC beams after freeze-thaw cycles．
2015, 45(2): 42-46.
doi: 10.13204/j.gyjz201502010
Abstract:
In the planning and design of most Chinese high-rise residential areas with large space between buildings or low density，generally there are the problems of monotonous layout of green space between houses，excessive pursuit of form and neglecting function，lacking of participation and interaction between people． With the help of the idea of the scheme design of the apartment for youth teachers and staff members in China University of Mining and Technology，by exploring the influence of spatial structure on people's behavior，the participation of people involving in the green space between houses was improved，so as to improve the effectiveness of the use of space，make the green house space have a good use．
In the planning and design of most Chinese high-rise residential areas with large space between buildings or low density，generally there are the problems of monotonous layout of green space between houses，excessive pursuit of form and neglecting function，lacking of participation and interaction between people． With the help of the idea of the scheme design of the apartment for youth teachers and staff members in China University of Mining and Technology，by exploring the influence of spatial structure on people's behavior，the participation of people involving in the green space between houses was improved，so as to improve the effectiveness of the use of space，make the green house space have a good use．
2015, 45(2): 47-49.
doi: 10.13204/j.gyjz201502011
Abstract:
Taking some disperse old industrial areas in different districts of a city as research object and viewing from special angles involving function transformation，building reuse orientation and their relation，merging into city，it was summarized several typical regeneration patterns，which appeared as being center district，being creative industry area， being art area，and being public services． By analyzing some influence factors of forming these regeneration patterns， including geographical location，economic environment and other external conditions，as well as the characteristics of location，the basic characteristics of different patterns and the possible range of application were summarized．
Taking some disperse old industrial areas in different districts of a city as research object and viewing from special angles involving function transformation，building reuse orientation and their relation，merging into city，it was summarized several typical regeneration patterns，which appeared as being center district，being creative industry area， being art area，and being public services． By analyzing some influence factors of forming these regeneration patterns， including geographical location，economic environment and other external conditions，as well as the characteristics of location，the basic characteristics of different patterns and the possible range of application were summarized．
2015, 45(2): 50-56.
doi: 10.13204/j.gyjz201502012
Abstract:
A new type of structural measure was put forward to improve the mechanical property of the flat-fell seam in two-way concrete composite floor． Monotonic tests were conducted on a composite slab strip，a composite slab strip with the flat-fell seam but no enhancing measures and a composite slab strip with enhancing measures on the flat-fell seam． The test results showed that lamination tears phenomenon was easily occurred on untreated rough surface when the joints in the composite slabs were not enhanced． After the crack-resisting steel bar was set on the joint，the limit bearing capacity of the slab strip would be greatly increased，but its effect on the short-period stiffness after cracking was little． The element analysis by ABAQUS 6. 11 program was conducted and the results between test and analysis were close; the impact of in the number of joints on the specimen's mechanical performance was also studied，which provided a basis for the further investigation of concrete superposed floor slabs．
A new type of structural measure was put forward to improve the mechanical property of the flat-fell seam in two-way concrete composite floor． Monotonic tests were conducted on a composite slab strip，a composite slab strip with the flat-fell seam but no enhancing measures and a composite slab strip with enhancing measures on the flat-fell seam． The test results showed that lamination tears phenomenon was easily occurred on untreated rough surface when the joints in the composite slabs were not enhanced． After the crack-resisting steel bar was set on the joint，the limit bearing capacity of the slab strip would be greatly increased，but its effect on the short-period stiffness after cracking was little． The element analysis by ABAQUS 6. 11 program was conducted and the results between test and analysis were close; the impact of in the number of joints on the specimen's mechanical performance was also studied，which provided a basis for the further investigation of concrete superposed floor slabs．
2015, 45(2): 57-61.
doi: 10.13204/j.gyjz201502013
Abstract:
In order to investigate the flexural capacity and deformation performance of prefabrication and assembly beam，three prefabrication and assembly beams and one cast-in-place RC beam were fabricated and the flexural capacity tests of RC beams were carried out． The mechanical properties of prefabrication and assembly beam with cast-in dapped-end connections were analyzed． The results showed that the failure mode and deformation of the prefabrication and assembly beam could meet the design requirements，cracking load and ultimate load were basically the same as the cast-in-place RC beam． Based on test data，the suitable range of the length of the precast section of the prefabrication and assembly beam was found out．
In order to investigate the flexural capacity and deformation performance of prefabrication and assembly beam，three prefabrication and assembly beams and one cast-in-place RC beam were fabricated and the flexural capacity tests of RC beams were carried out． The mechanical properties of prefabrication and assembly beam with cast-in dapped-end connections were analyzed． The results showed that the failure mode and deformation of the prefabrication and assembly beam could meet the design requirements，cracking load and ultimate load were basically the same as the cast-in-place RC beam． Based on test data，the suitable range of the length of the precast section of the prefabrication and assembly beam was found out．
2015, 45(2): 62-64.
doi: 10.13204/j.gyjz201502014
Abstract:
In order to obtain the plane stress strength curve of masonry structure，based on the experimental research of mechanical properties and the test method in current specification，several kinds of tests were carried out， including horizontal compressive strength tests，vertical compressive strength tests，straight-line joint tensile strength tests and vertical tensile strength tests． The results of these tests conforms to the basic mechanical properties of masonry structure with high compressive strength and low tensile strength． The test data could be used to determine the key points on the axis of the plane stress curve． Besides，the method of tensile strength tests in the paper could be applied in all kinds of tensile strength tests for masonry structures．
In order to obtain the plane stress strength curve of masonry structure，based on the experimental research of mechanical properties and the test method in current specification，several kinds of tests were carried out， including horizontal compressive strength tests，vertical compressive strength tests，straight-line joint tensile strength tests and vertical tensile strength tests． The results of these tests conforms to the basic mechanical properties of masonry structure with high compressive strength and low tensile strength． The test data could be used to determine the key points on the axis of the plane stress curve． Besides，the method of tensile strength tests in the paper could be applied in all kinds of tensile strength tests for masonry structures．
2015, 45(2): 65-69.
doi: 10.13204/j.gyjz201502015
Abstract:
As one of the four highest ancient towers in China，Chongwen pagoda suffered serious damages in Whenchuan earthquake．In order to estimate the present situation and safety of Chongwen pagoda，the detailed survey and investigation of seismic damage were made．It was analysed the reason of its seismic damage through the finite element software and the basic mechanics concept，then the safety of the pagoda was evaluated．The analysis indicated that Chongwen pagoda was in unstable condition．
As one of the four highest ancient towers in China，Chongwen pagoda suffered serious damages in Whenchuan earthquake．In order to estimate the present situation and safety of Chongwen pagoda，the detailed survey and investigation of seismic damage were made．It was analysed the reason of its seismic damage through the finite element software and the basic mechanics concept，then the safety of the pagoda was evaluated．The analysis indicated that Chongwen pagoda was in unstable condition．
2015, 45(2): 70-75.
doi: 10.13204/j.gyjz201502016
Abstract:
In order to analyze the effect of segmental joint weak layers on deformation of long span cantilever-casting PC box girders，FE models with segmental joint weak layer elements were established based on the FE model considering construction processes of the assistant shipping channel bridge of humen bridge． Considering variations in thickness and material properties of segmental joint weak layer elements，the problem was studied with FEA． The results showed that deformation of segmental joint weak layers could lead to significant increment in cumulative deformation of long span cantilever-casting PC box girders; the shearing deformation of segmental joint weak layers was quite small，and this effect was mainly induced by bending deformation of segmental joint weak layers． Meanwhile，construction technology measure of chiselling was proposed to decrease the effect．
In order to analyze the effect of segmental joint weak layers on deformation of long span cantilever-casting PC box girders，FE models with segmental joint weak layer elements were established based on the FE model considering construction processes of the assistant shipping channel bridge of humen bridge． Considering variations in thickness and material properties of segmental joint weak layer elements，the problem was studied with FEA． The results showed that deformation of segmental joint weak layers could lead to significant increment in cumulative deformation of long span cantilever-casting PC box girders; the shearing deformation of segmental joint weak layers was quite small，and this effect was mainly induced by bending deformation of segmental joint weak layers． Meanwhile，construction technology measure of chiselling was proposed to decrease the effect．
2015, 45(2): 76-79.
doi: 10.13204/j.gyjz201502017
Abstract:
At present，there is no formula which calculates the quantitative influence of the bottom reinforcement arrangement concentrated at the extent near the pile top on the punching bearing capacity of pile caps． Based on the spatial strut-and-tie theory of pile cap punching failure，a gradual least square method for multiple variables was used，and calculative formulae were derived for that sort of reinforcement of the pile cap． Verification with the published test data of changeable number and arrangement of pile in the literatures both at home and abroad， indicated that the proposed formulae were rational． It was expected that the engineering cost of pile caps and the slab of pile raft could be reduced by the rational arrangement of longitudinal reinforcement．
At present，there is no formula which calculates the quantitative influence of the bottom reinforcement arrangement concentrated at the extent near the pile top on the punching bearing capacity of pile caps． Based on the spatial strut-and-tie theory of pile cap punching failure，a gradual least square method for multiple variables was used，and calculative formulae were derived for that sort of reinforcement of the pile cap． Verification with the published test data of changeable number and arrangement of pile in the literatures both at home and abroad， indicated that the proposed formulae were rational． It was expected that the engineering cost of pile caps and the slab of pile raft could be reduced by the rational arrangement of longitudinal reinforcement．
2015, 45(2): 80-84.
doi: 10.13204/j.gyjz201502018
Abstract:
The tailings strength parameters is the key factor that affects the analysis of tailings dam stability． Based on triaxial tests under high stresses，the nonlinear strength property of tailings was validated． The results showed that the triaxial consolidation undrained shear curves had obviously softening characteristics，and the degree of strain softening increased as the stresses increased． According to triaxial stress-strain curves，an improved hyperbola model was set up for describing the phenomenon of tailings sand strain softening． The quadratic parabolic and power exponent function of envelope lines were adopted to describe the nonlinearity of strength characteristics，and the comparison results showed that the power exponent function of Mohr envelope had high precision as the criterion of breaking strength of tailings sand under high stresses． The function of equivalent normal stress and tangent value of internal friction angle indicated that the internal friction angle of tailings sand under high stresses was not a fixed value，but had nonlinearity characteristics of power exponent function．
The tailings strength parameters is the key factor that affects the analysis of tailings dam stability． Based on triaxial tests under high stresses，the nonlinear strength property of tailings was validated． The results showed that the triaxial consolidation undrained shear curves had obviously softening characteristics，and the degree of strain softening increased as the stresses increased． According to triaxial stress-strain curves，an improved hyperbola model was set up for describing the phenomenon of tailings sand strain softening． The quadratic parabolic and power exponent function of envelope lines were adopted to describe the nonlinearity of strength characteristics，and the comparison results showed that the power exponent function of Mohr envelope had high precision as the criterion of breaking strength of tailings sand under high stresses． The function of equivalent normal stress and tangent value of internal friction angle indicated that the internal friction angle of tailings sand under high stresses was not a fixed value，but had nonlinearity characteristics of power exponent function．
2015, 45(2): 85-89.
doi: 10.13204/j.gyjz201502019
Abstract:
An experimental research on improvement on ground of coral debris mixed with mucky soil by high vacuum densification method ( HVDM) was carried out． Through circulation processing of vacuum drainage and dynamic compaction for three times，groundwater level declined by about 4 m，ground settlement by construction was 68 cm． The improved ground was tested by static cone penetration test ，plate load test，and standard penetration test，the results showed that the bearing capacity value was over 150 kPa and the influence depth was about 10 m． The observation of pore water pressure indicated obvious effect of pressure difference associated with vacuum and dynamic compaction． The tests indicated that HVDM had an excellent effect in the site．
An experimental research on improvement on ground of coral debris mixed with mucky soil by high vacuum densification method ( HVDM) was carried out． Through circulation processing of vacuum drainage and dynamic compaction for three times，groundwater level declined by about 4 m，ground settlement by construction was 68 cm． The improved ground was tested by static cone penetration test ，plate load test，and standard penetration test，the results showed that the bearing capacity value was over 150 kPa and the influence depth was about 10 m． The observation of pore water pressure indicated obvious effect of pressure difference associated with vacuum and dynamic compaction． The tests indicated that HVDM had an excellent effect in the site．
2015, 45(2): 90-94.
doi: 10.13204/j.gyjz201502020
Abstract:
Based on Terzaghi's one dimensional consolidation theory，the practical calculation method of the ground subsidence was proposed under water level change of various types of ground water． The calculation program was compiled to calculate and analyze ground subsidence caused by drawing ground water． This program was also used to compute the ground subsidence in the eastern region of Beijing． By comparison with the measured results，the reliability and rationality of the calculation method and the program were verified．
Based on Terzaghi's one dimensional consolidation theory，the practical calculation method of the ground subsidence was proposed under water level change of various types of ground water． The calculation program was compiled to calculate and analyze ground subsidence caused by drawing ground water． This program was also used to compute the ground subsidence in the eastern region of Beijing． By comparison with the measured results，the reliability and rationality of the calculation method and the program were verified．
2015, 45(2): 95-100.
doi: 10.13204/j.gyjz201502021
Abstract:
With construction of a large number of mountain tunnels，the deformation control of construction in the tunnel of biased soft surrounding rock and its stability have become the focus of attention of the tunnel engineering． Taking Liujiazhuang tunnel of Shanghai-Kunming passenger line． By using the finite element software of ABAQUS， the whole section method，the steps method and the CD method，the construction process of the section passing through coal seam was simulated to get the stress and strain law of surrounding rock and supporting structure under different construction methods． Through optimization of the different methods and monitoring data compared with the results of numerical simulation，it could be concluded that using forepole method of up and down steps is more economic and reasonable than the rest construction schemes，and some measures and advices of deformation control were given，which provided important reference and reference for similar projects．
With construction of a large number of mountain tunnels，the deformation control of construction in the tunnel of biased soft surrounding rock and its stability have become the focus of attention of the tunnel engineering． Taking Liujiazhuang tunnel of Shanghai-Kunming passenger line． By using the finite element software of ABAQUS， the whole section method，the steps method and the CD method，the construction process of the section passing through coal seam was simulated to get the stress and strain law of surrounding rock and supporting structure under different construction methods． Through optimization of the different methods and monitoring data compared with the results of numerical simulation，it could be concluded that using forepole method of up and down steps is more economic and reasonable than the rest construction schemes，and some measures and advices of deformation control were given，which provided important reference and reference for similar projects．
2015, 45(2): 101-106.
doi: 10.13204/j.gyjz201502022
Abstract:
To study safety performance of plug-in steel-tube scaffold ，it was conducted field test researches on the falsework and the exterior scaffolding for special-shaped structure． Also static and buckling analyses were done by ANSYS finite element software to obtain the stress and stability capacity of scaffolding under different constructing conditions． The results indicate that when exceeds or equals 0. 5，the safety coefficient of ADG plug-in scaffold in French steel structure standard is significantly higher than that in the scaffolding code K = 2 in China; as the nodes of plug-in scaffold are semi-rigid，the theoretical values agree well with the experimental values when stiffness takes 20 kNm/rad． Instability of the falsework belongs to the local instability， the overhang length of vertical bar end has an important impact on the bearing capacity for falsework． It was suggested that the design of plug-in scaffold should use semi-rigid sway frames theory．
To study safety performance of plug-in steel-tube scaffold ，it was conducted field test researches on the falsework and the exterior scaffolding for special-shaped structure． Also static and buckling analyses were done by ANSYS finite element software to obtain the stress and stability capacity of scaffolding under different constructing conditions． The results indicate that when exceeds or equals 0. 5，the safety coefficient of ADG plug-in scaffold in French steel structure standard is significantly higher than that in the scaffolding code K = 2 in China; as the nodes of plug-in scaffold are semi-rigid，the theoretical values agree well with the experimental values when stiffness takes 20 kNm/rad． Instability of the falsework belongs to the local instability， the overhang length of vertical bar end has an important impact on the bearing capacity for falsework． It was suggested that the design of plug-in scaffold should use semi-rigid sway frames theory．
2015, 45(2): 107-113.
doi: 10.13204/j.gyjz201502023
Abstract:
When the mode superposition method is applied to the seismic responses analysis of large-span spatial structures，several problems always become difficult to handle，such as the inefficient calculation and the incapable consideration of earthquake random property． To solve the problems，the seismic response components of large-span spatial structures，including the quasi-static components and resonant components were studied and defined． Based on the seismic response component research，a modified strategy for the mode superposition method of seismic responses of large-span spatial structures was proposed． Through numerical analysis of two typical shell structures， the characteristics of the quasi-static responses and resonant responses and effects of correlation between two components were studied． The distribution features of each response component of large-span spatial structures were summarized．
When the mode superposition method is applied to the seismic responses analysis of large-span spatial structures，several problems always become difficult to handle，such as the inefficient calculation and the incapable consideration of earthquake random property． To solve the problems，the seismic response components of large-span spatial structures，including the quasi-static components and resonant components were studied and defined． Based on the seismic response component research，a modified strategy for the mode superposition method of seismic responses of large-span spatial structures was proposed． Through numerical analysis of two typical shell structures， the characteristics of the quasi-static responses and resonant responses and effects of correlation between two components were studied． The distribution features of each response component of large-span spatial structures were summarized．
2015, 45(2): 114-117.
doi: 10.13204/j.gyjz201502024
Abstract:
A new type of long-span spatial steel frame was used for Guangdong Science Center ( GSC) ． The isolation techniques are introduced into the E square of GSC to protect the huge building from damage during external loads， especially typhoon and earthquake，and ensure the safety of people，exhibits and instruments in the building． Isolating bearings were directly placed on the base of the columns． The non-linear dynamic analysis and shaking table tests were used to study the vibration reduction effect of the model with base isolation contrasting to the structure without base isolation，evaluate the improvement degree of the earthquake-resistance capability，and estimate the rationality of the isolation methods by the effect of the bearings on the performance harmony of column deformation． It was shown by the study that the isolation methods could obviously improve the earthquake-resistance capability of the building，modify the torsion performance and enhance the safety during severe earthquakes more markedly，especially for the structures with irregular space． Additionally，isolation bearings had no negative effect on the performance harmony of column deformation for the stiffness． The isolation design methods of GSC were rational，and could be an useful effort for isolation design of large-scale spatial structures．
A new type of long-span spatial steel frame was used for Guangdong Science Center ( GSC) ． The isolation techniques are introduced into the E square of GSC to protect the huge building from damage during external loads， especially typhoon and earthquake，and ensure the safety of people，exhibits and instruments in the building． Isolating bearings were directly placed on the base of the columns． The non-linear dynamic analysis and shaking table tests were used to study the vibration reduction effect of the model with base isolation contrasting to the structure without base isolation，evaluate the improvement degree of the earthquake-resistance capability，and estimate the rationality of the isolation methods by the effect of the bearings on the performance harmony of column deformation． It was shown by the study that the isolation methods could obviously improve the earthquake-resistance capability of the building，modify the torsion performance and enhance the safety during severe earthquakes more markedly，especially for the structures with irregular space． Additionally，isolation bearings had no negative effect on the performance harmony of column deformation for the stiffness． The isolation design methods of GSC were rational，and could be an useful effort for isolation design of large-scale spatial structures．
2015, 45(2): 118-124.
doi: 10.13204/j.gyjz201502025
Abstract:
An uniaxial loaded experiment of beam-pillar supported joint widely used in steel structure workshop was introduced． Three specimens of different working place was studied． A comparison between the result under ultimate load and the result of the present method was made． The axial force of slanting brace was obtained and was compared with the stress of repeatedly loaded experiment． The result showed that the joint had different load carrying capacity in different working place． The present calculation method was safe when the brace was not yielded and the stiffness and strength of the connection angle steel could meet the requirements． The method proposed in this paper could be used when the stiffness and strength of the connection angle steel could not meet the requirements．
An uniaxial loaded experiment of beam-pillar supported joint widely used in steel structure workshop was introduced． Three specimens of different working place was studied． A comparison between the result under ultimate load and the result of the present method was made． The axial force of slanting brace was obtained and was compared with the stress of repeatedly loaded experiment． The result showed that the joint had different load carrying capacity in different working place． The present calculation method was safe when the brace was not yielded and the stiffness and strength of the connection angle steel could meet the requirements． The method proposed in this paper could be used when the stiffness and strength of the connection angle steel could not meet the requirements．
2015, 45(2): 125-130.
doi: 10.13204/j.gyjz201502026
Abstract:
The existing seismic design methods of air-cooled condenser structure do not meet theinvestment benefit criterion because they do not consider the safety of the equipment in earthquake． Through the experimental study on the seismic performance of the structure，performance levels and quantified values of the structure were given，which were suitable for the structure-equipment coupled system，the design methods and steps were established． Finally， displacement-based seismic design method was used to analyze a 1 000 MW air-cooled condenser structure，and the nonlinear dynamic time history analysis was taken for validation． The results showed that displacement-based seismic design method was reasonable．
The existing seismic design methods of air-cooled condenser structure do not meet theinvestment benefit criterion because they do not consider the safety of the equipment in earthquake． Through the experimental study on the seismic performance of the structure，performance levels and quantified values of the structure were given，which were suitable for the structure-equipment coupled system，the design methods and steps were established． Finally， displacement-based seismic design method was used to analyze a 1 000 MW air-cooled condenser structure，and the nonlinear dynamic time history analysis was taken for validation． The results showed that displacement-based seismic design method was reasonable．
2015, 45(2): 131-135.
doi: 10.13204/j.gyjz201502027
Abstract:
Based on the contrast analysis of Eurocode 3 ( EN1993 －1－3) and Technical Code of Cold-Formed Thin-Wall Section Steel Structure( GB 500182002)，analysis and discussion are mentioned about the effective section of cold-formed thin-wall lipped channel purlins． The results showed that the provisions of the effective section modulus in the GB 50018 2002 specifications were too conservative，while the results were close to each other by the Eurocode 3 and facts． Under full stress condition， the reduction factor of the effective section modulus of cold-formed thin-wall lipped channel purlins from C180 to C250 ( 2 mm thickness) was 0. 9 ( Q235 steel) and 0. 8 ( Q345 steel) respectively．
Based on the contrast analysis of Eurocode 3 ( EN1993 －1－3) and Technical Code of Cold-Formed Thin-Wall Section Steel Structure( GB 500182002)，analysis and discussion are mentioned about the effective section of cold-formed thin-wall lipped channel purlins． The results showed that the provisions of the effective section modulus in the GB 50018 2002 specifications were too conservative，while the results were close to each other by the Eurocode 3 and facts． Under full stress condition， the reduction factor of the effective section modulus of cold-formed thin-wall lipped channel purlins from C180 to C250 ( 2 mm thickness) was 0. 9 ( Q235 steel) and 0. 8 ( Q345 steel) respectively．
2015, 45(2): 136-142.
doi: 10.13204/j.gyjz201502028
Abstract:
In order to study the strength，integral stability，local stability and rigidity etc of circular hole cellular beams，experimental investigations and finite element analysis of three simply supported circular hole cellular beams and three steel-concrete composite cellular beams were conducted． The influences on mechanical performance of circular hole cellular beams of different making method ( with or without weld on web) ，flange width，hole size，the width of beam pier and the combined effects were compared and analysed． And the stress distributions on the loading point and pedestal point of the beam were acquired． Experimental and finite element analytical results showed that the impact degree of weld on web on the capacity and rigidity of cellular beams was generally within 20%． And broadening flange，installing stiffener and increasing the width of beam pier could improve the bearing capacity of the cellular beams． The load carrying capacity and the initial stiffness of steel-concrete composite cellular beam were significantly improved as compared with non-composite cellular beams．
In order to study the strength，integral stability，local stability and rigidity etc of circular hole cellular beams，experimental investigations and finite element analysis of three simply supported circular hole cellular beams and three steel-concrete composite cellular beams were conducted． The influences on mechanical performance of circular hole cellular beams of different making method ( with or without weld on web) ，flange width，hole size，the width of beam pier and the combined effects were compared and analysed． And the stress distributions on the loading point and pedestal point of the beam were acquired． Experimental and finite element analytical results showed that the impact degree of weld on web on the capacity and rigidity of cellular beams was generally within 20%． And broadening flange，installing stiffener and increasing the width of beam pier could improve the bearing capacity of the cellular beams． The load carrying capacity and the initial stiffness of steel-concrete composite cellular beam were significantly improved as compared with non-composite cellular beams．
2015, 45(2): 143-148.
doi: 10.13204/j.gyjz201502029
Abstract:
In order to research the mechanical properties of the typical butterfly-shaped joint in a heavy cross layer truss for a new-built steel railway station，model test and numerical calculation were adopted． The test model was designed according to the proportion of 1∶ 4 scale and the counterforce device was designed specially to ensure the boundary condition of the rods being hinged，the weak links and failure modes were clear by pseudo-static test． The model test analysis was verified by numerical calculation considering the material yield and fracture failure． At the same time，the effects of three different reinforced methods including flitch plate joint，cover plate joint and sleeve joint on bearing capacity and energy dissipation ability of the joint were considered to compare with the original joint without any strengthening measures． The results showed that the flitch plate method was worth popularizing for it could improve the energy dissipation of the joint and had a better manufacturability．
In order to research the mechanical properties of the typical butterfly-shaped joint in a heavy cross layer truss for a new-built steel railway station，model test and numerical calculation were adopted． The test model was designed according to the proportion of 1∶ 4 scale and the counterforce device was designed specially to ensure the boundary condition of the rods being hinged，the weak links and failure modes were clear by pseudo-static test． The model test analysis was verified by numerical calculation considering the material yield and fracture failure． At the same time，the effects of three different reinforced methods including flitch plate joint，cover plate joint and sleeve joint on bearing capacity and energy dissipation ability of the joint were considered to compare with the original joint without any strengthening measures． The results showed that the flitch plate method was worth popularizing for it could improve the energy dissipation of the joint and had a better manufacturability．
2015, 45(2): 149-153.
doi: 10.13204/j.gyjz201502030
Abstract:
ABAQUS finite element software was used to analyze the bending performance of web core sandwich plate in low temperature environment，and it was compared the deflection value to the theoretical deflection value under temperature-load，finally it was also，compared the influence of the thin web temperature transfer function and plate thickness change on the web core sandwich plate deflection． The results showed that in low temperature environment， the total deflection of elastic stage of the web core sandwich plate increased linearly and the influence of the temperature transfer function increased gradually on the plate deflection as the temperature lowered． The deflection value of considering temperature transfer is smaller than without considering temperature transfer，theoretical deflection value was between the two，the ratio of the value and the total deflection increased with reducing temperature，and tended to be stable gradually; increasing the thickness of the plate，the total deflection was decreasing gradually with reducing temperature，increasing the thickness of the plate could effectively diminish the deflection，but the proportion of the deflection caused by the temperature effect accounted for the total deflection was increased．
ABAQUS finite element software was used to analyze the bending performance of web core sandwich plate in low temperature environment，and it was compared the deflection value to the theoretical deflection value under temperature-load，finally it was also，compared the influence of the thin web temperature transfer function and plate thickness change on the web core sandwich plate deflection． The results showed that in low temperature environment， the total deflection of elastic stage of the web core sandwich plate increased linearly and the influence of the temperature transfer function increased gradually on the plate deflection as the temperature lowered． The deflection value of considering temperature transfer is smaller than without considering temperature transfer，theoretical deflection value was between the two，the ratio of the value and the total deflection increased with reducing temperature，and tended to be stable gradually; increasing the thickness of the plate，the total deflection was decreasing gradually with reducing temperature，increasing the thickness of the plate could effectively diminish the deflection，but the proportion of the deflection caused by the temperature effect accounted for the total deflection was increased．
2015, 45(2): 154-158.
doi: 10.13204/j.gyjz201502031
Abstract:
A complex steel structure system of combining steel frame-supporting system with intersected trusses was adopted as the main structure of Tianjin library． The stress level in key joints was high in construction process due to frequent changes of the main steel structure system，therefore it was necessary to monitor its stress in the whole constructing process． Three methods，electric resistance static strain testing system，electric resistance dynamic strain testing system and vibrating wire strain gauge system were used for monitoring． Results of these 3 ways are in accordance with each other，which guaranteed the smoothness of construction procedure and the accuracy and validity of monitoring results．
A complex steel structure system of combining steel frame-supporting system with intersected trusses was adopted as the main structure of Tianjin library． The stress level in key joints was high in construction process due to frequent changes of the main steel structure system，therefore it was necessary to monitor its stress in the whole constructing process． Three methods，electric resistance static strain testing system，electric resistance dynamic strain testing system and vibrating wire strain gauge system were used for monitoring． Results of these 3 ways are in accordance with each other，which guaranteed the smoothness of construction procedure and the accuracy and validity of monitoring results．
2015, 45(2): 159-164.
doi: 10.13204/j.gyjz201502032
Abstract:
The method of strengthening steel structure by welding while under load has been widely used in numerous reinforcement projects． However，despite some general tips，there are no specific provisions in present foreign technical standards． The few specific design provisions are only left within Chinese standards Technical Specification for Strengthening Steel Structures ( CECS 77 ∶ 96 ) and Technical Specification for Inspection，Assessment and Strengthening of Steel Structures ( YB 925796) ． The provisions framework of domestic code and specification to solve the problem of strengthening by welding under load was combed． And the calculation examples and analyses related to design methods of steel columns under axial and eccentric load were given． The concept of joint reinforcement coefficient was also proposed to make unified definition for the unreasonable situation in two standards． By comparison，the discrepancies and inadequacies were pointed out to provide reference for the follow-up researches and code revision．
The method of strengthening steel structure by welding while under load has been widely used in numerous reinforcement projects． However，despite some general tips，there are no specific provisions in present foreign technical standards． The few specific design provisions are only left within Chinese standards Technical Specification for Strengthening Steel Structures ( CECS 77 ∶ 96 ) and Technical Specification for Inspection，Assessment and Strengthening of Steel Structures ( YB 925796) ． The provisions framework of domestic code and specification to solve the problem of strengthening by welding under load was combed． And the calculation examples and analyses related to design methods of steel columns under axial and eccentric load were given． The concept of joint reinforcement coefficient was also proposed to make unified definition for the unreasonable situation in two standards． By comparison，the discrepancies and inadequacies were pointed out to provide reference for the follow-up researches and code revision．
2015, 45(2): 165-169.
doi: 10.13204/j.gyjz201502033
Abstract:
The buckling restrained braces were erected on the integral frame consisted of six stories reinforced concrete frame and one story steel frame added at the top． The design of buckling restrained brace was discussed． The performance under frequent earthquake and rare earthquake of the integral structure was calculated and comparatively analyzed by finite element software． The analysis showed that the working performance and the frame torsion were improved，interstory displacement of frame was controled effectively by using the buckling restrained brace．
The buckling restrained braces were erected on the integral frame consisted of six stories reinforced concrete frame and one story steel frame added at the top． The design of buckling restrained brace was discussed． The performance under frequent earthquake and rare earthquake of the integral structure was calculated and comparatively analyzed by finite element software． The analysis showed that the working performance and the frame torsion were improved，interstory displacement of frame was controled effectively by using the buckling restrained brace．
2015, 45(2): 170-173.
doi: 10.13204/j.gyjz201502034
Abstract:
An industry gathering area includes all kinds of development zones，such as: economic and technological development zones，high-tech industrial development zones， industrial parks，modern service industry park． In view of urban geography，urban economics theories，and using many methods，such as urban planning and industrial development planning etc，it was demonstrated that the location choice of fine chemicals industry gathering area in Kaifeng was reasonable，it was planned and studied the arrangements of strategic goals and industries choices， spatial design and supporting measures for it，which provided a reference for the development of relevant industry gathering areas．
An industry gathering area includes all kinds of development zones，such as: economic and technological development zones，high-tech industrial development zones， industrial parks，modern service industry park． In view of urban geography，urban economics theories，and using many methods，such as urban planning and industrial development planning etc，it was demonstrated that the location choice of fine chemicals industry gathering area in Kaifeng was reasonable，it was planned and studied the arrangements of strategic goals and industries choices， spatial design and supporting measures for it，which provided a reference for the development of relevant industry gathering areas．
2015, 45(2): 174-177.
doi: 10.13204/j.gyjz201502035
Abstract:
Industrial workshops have been always designed and constructed by standard templates，it is hard to express their personalities and be short of features． Taking the architectural design of the workshops for Sichuan Langjiu Group Gulin Factory for example，it was analyzed how to blend complicated factors into the industrial building design process，such as the geographical environment，the history and culture context，the production process and the modern production technology; it was searched for the idea of how to organize the regional characteristics in the design of an industrial building under modular construction system．
Industrial workshops have been always designed and constructed by standard templates，it is hard to express their personalities and be short of features． Taking the architectural design of the workshops for Sichuan Langjiu Group Gulin Factory for example，it was analyzed how to blend complicated factors into the industrial building design process，such as the geographical environment，the history and culture context，the production process and the modern production technology; it was searched for the idea of how to organize the regional characteristics in the design of an industrial building under modular construction system．
2015, 45(2): 178-183.
doi: 10.13204/j.gyjz201502036
Abstract:
The mechanical analysis of the structural model is still an isolated part in the information integration chain of BIM ( Building Information Modeling) technology． The composition and characteristic of the structural BIM model was analyzed through studying the data definition layers of BIM． The advantages were compared when the structural BIM model was adopted in the structural analysis and construction drawing design stage，and the included data information of the structural analysis model in the IFC4 version was discussed． An indirect method for the data conversion was proposed between BIM model and structural analysis model based on the methodology research，and a data conversion interface was developed． Four project cases were adopted to test the interface for data conversion between BIM model and structural analysis models，which created by four common finite element softwares． The results show that the data conversion interface has a good effect on different structural types，and can provide technical reference for data integration and sharing in the structural analysis phase by using BIM technology．
The mechanical analysis of the structural model is still an isolated part in the information integration chain of BIM ( Building Information Modeling) technology． The composition and characteristic of the structural BIM model was analyzed through studying the data definition layers of BIM． The advantages were compared when the structural BIM model was adopted in the structural analysis and construction drawing design stage，and the included data information of the structural analysis model in the IFC4 version was discussed． An indirect method for the data conversion was proposed between BIM model and structural analysis model based on the methodology research，and a data conversion interface was developed． Four project cases were adopted to test the interface for data conversion between BIM model and structural analysis models，which created by four common finite element softwares． The results show that the data conversion interface has a good effect on different structural types，and can provide technical reference for data integration and sharing in the structural analysis phase by using BIM technology．
2015, 45(2): 184-185.
doi: 10.13204/j.gyjz201502037
Abstract:
It has been long since Chinese building industry undergoing a messy time． Although the critical voice never stopped，the construction of weird buildings were still carried on． This paper analysed the characteristics of weird buildings，which had been widely discussed in the society recently，and pointed out the causes of their appearance and negative social impacts，so as to promote a scientific and healthy development of Chinese building industry．
It has been long since Chinese building industry undergoing a messy time． Although the critical voice never stopped，the construction of weird buildings were still carried on． This paper analysed the characteristics of weird buildings，which had been widely discussed in the society recently，and pointed out the causes of their appearance and negative social impacts，so as to promote a scientific and healthy development of Chinese building industry．
