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2020 Vol. 50, No. 10
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2020, 50(10): 1-10.
doi: 10.13204/j.gyjzG20062707
Abstract:
In order to explore the performances and mechanisms of reinforced concrete stub columns with hot-rolled high-strength rebars of 635 MPa under axial compression, a finite element analysis model of reinforced concrete stub columns with hot-rolled rebars under axial compression was modelled, and the accuracy of the model was verified based on the results of the axial compression test. Subsequently, the influences of various parameters such as longitudinal reinforcement ratios, stirrup strength and stirrup volume ratios on its axial compression performances were carried out. The bearing characteristics of stub columns subjected to the axial compression process were revealed and the issue of concrete strength matching with high strength rebars was also discussed. Finally, considering the influence of the stirrup strength, volumetric stirrup ratios and concrete strength, the calculation method for predicting the bearing capacity of reinforced concrete stub columns with hot-rolled ribbed high-strength rebars of 635 MPa subjected to axially compressed loads was proposed based on the results of numerical analysis. The results showed that the failure mode of short reinforced concrete columns with hot-rolled ribbed high-strength rebars of 635 MPa mainly displayed as concrete crushing at the mid-height of the column shafts, and the rebar cages were curved like lanterns; the ultimate axial compression bearing capacity of short columns increased with the increase of concrete strength, longitudinal reinforcement ratios, longitudinal reinforcement strength, stirrup volumetric ratios and stirrup strength; in order to take full use of the strength of hot-rolled ribbed high-strength steel bars of 635 MPa, it was appropriate to match concrete with strength above C50; the proposed calculation formula of ultimate bearing capacity could be used in practical engineering.
In order to explore the performances and mechanisms of reinforced concrete stub columns with hot-rolled high-strength rebars of 635 MPa under axial compression, a finite element analysis model of reinforced concrete stub columns with hot-rolled rebars under axial compression was modelled, and the accuracy of the model was verified based on the results of the axial compression test. Subsequently, the influences of various parameters such as longitudinal reinforcement ratios, stirrup strength and stirrup volume ratios on its axial compression performances were carried out. The bearing characteristics of stub columns subjected to the axial compression process were revealed and the issue of concrete strength matching with high strength rebars was also discussed. Finally, considering the influence of the stirrup strength, volumetric stirrup ratios and concrete strength, the calculation method for predicting the bearing capacity of reinforced concrete stub columns with hot-rolled ribbed high-strength rebars of 635 MPa subjected to axially compressed loads was proposed based on the results of numerical analysis. The results showed that the failure mode of short reinforced concrete columns with hot-rolled ribbed high-strength rebars of 635 MPa mainly displayed as concrete crushing at the mid-height of the column shafts, and the rebar cages were curved like lanterns; the ultimate axial compression bearing capacity of short columns increased with the increase of concrete strength, longitudinal reinforcement ratios, longitudinal reinforcement strength, stirrup volumetric ratios and stirrup strength; in order to take full use of the strength of hot-rolled ribbed high-strength steel bars of 635 MPa, it was appropriate to match concrete with strength above C50; the proposed calculation formula of ultimate bearing capacity could be used in practical engineering.
2020, 50(10): 11-19.
doi: 10.13204/j.gyjzG20021905
Abstract:
Hot-rolled ribbed steel bars of 635 MPa are a new high-strength metal material produced by hot rolling and micro-alloying processes. Compared with heat-treated and cold-rolled high-strength steel bars, they have significant advantages of high strength, good ductility, low cost. In order to study the eccentric compressive performances of concrete columns reinforced with hot-rolled ribbed high-strength rebars of 635 MPa, a total of 20 high-strength reinforced concrete columns with hot-rolled ribbed high-strength rebars of 635 MPa were tested under the eccentric loading. The test parameters were load eccentricity ratios, longitudinal reinforcement ratios, stirrup strength and aspect ratios. The typical failure modes and mechanical properties of the columns were revealed as well. Moreover,deflection curves of columns subjected to eccentric compressive loads and development rules of cross-section strain were obtained. The results indicated that the failure modes of the columns with hot-rolled ribbed high-strength rebars of 635 MPa mainly included compressive failures subjected to large or small eccentric loads. The eccentric compressive strength of columns was enhanced with the decrease of the load eccentric ratios and the aspect ratios, and with the increase of the longitudinal reinforcement ratios and the decrease of stirrup strength. The ductility properties of the columns were obviously improved with the increase of the stirrup strength and the longitudinal reinforcement ratios. Based on the code of GB 50010-2010, the predicted eccentric strength of the columns was compared with those by the experiments. The results showed that the current code could be used to evaluate the eccentric bearing capacity of reinforced concrete columns with high-strength hot-rolled rebars of 635 MPa accurately. The study might provide scientific reference for application of the hot-rolled ribbed high-strength rebars of 635 MPa in concrete structures.
Hot-rolled ribbed steel bars of 635 MPa are a new high-strength metal material produced by hot rolling and micro-alloying processes. Compared with heat-treated and cold-rolled high-strength steel bars, they have significant advantages of high strength, good ductility, low cost. In order to study the eccentric compressive performances of concrete columns reinforced with hot-rolled ribbed high-strength rebars of 635 MPa, a total of 20 high-strength reinforced concrete columns with hot-rolled ribbed high-strength rebars of 635 MPa were tested under the eccentric loading. The test parameters were load eccentricity ratios, longitudinal reinforcement ratios, stirrup strength and aspect ratios. The typical failure modes and mechanical properties of the columns were revealed as well. Moreover,deflection curves of columns subjected to eccentric compressive loads and development rules of cross-section strain were obtained. The results indicated that the failure modes of the columns with hot-rolled ribbed high-strength rebars of 635 MPa mainly included compressive failures subjected to large or small eccentric loads. The eccentric compressive strength of columns was enhanced with the decrease of the load eccentric ratios and the aspect ratios, and with the increase of the longitudinal reinforcement ratios and the decrease of stirrup strength. The ductility properties of the columns were obviously improved with the increase of the stirrup strength and the longitudinal reinforcement ratios. Based on the code of GB 50010-2010, the predicted eccentric strength of the columns was compared with those by the experiments. The results showed that the current code could be used to evaluate the eccentric bearing capacity of reinforced concrete columns with high-strength hot-rolled rebars of 635 MPa accurately. The study might provide scientific reference for application of the hot-rolled ribbed high-strength rebars of 635 MPa in concrete structures.
2020, 50(10): 20-25.
doi: 10.13204/j.gyjz201904280010
Abstract:
In order to explore the applicability of rebar HRB600 for concrete flexural members under normal service conditions, five reinforced concrete beams with rebar HRB600 and different reinforcement ratios, rebar diameters and reinforcement methods were designed and fabrcated. The bending performances test of the above specimens were carried out by the three-point loading method. The results showed that the overall bending performances (crack development, failure modes and ductility) of the beams were the same as that of the concrete beam with ordinary rebars. The calculation deflection values that took quasi-permanent combination and considered long-term load action could meet limit requirements of the code of GB 50010-2010. However, the crack width of the corresponding members could not meet the limit. The reasons that crack width exceed the limits, especially the measures to reduce crack width of the flexural members, were analyzed.
In order to explore the applicability of rebar HRB600 for concrete flexural members under normal service conditions, five reinforced concrete beams with rebar HRB600 and different reinforcement ratios, rebar diameters and reinforcement methods were designed and fabrcated. The bending performances test of the above specimens were carried out by the three-point loading method. The results showed that the overall bending performances (crack development, failure modes and ductility) of the beams were the same as that of the concrete beam with ordinary rebars. The calculation deflection values that took quasi-permanent combination and considered long-term load action could meet limit requirements of the code of GB 50010-2010. However, the crack width of the corresponding members could not meet the limit. The reasons that crack width exceed the limits, especially the measures to reduce crack width of the flexural members, were analyzed.
2020, 50(10): 26-31,68.
doi: 10.13204/j.gyjzG20011902
Abstract:
Corrosion of steel is an important factor affecting the bonding properties of steel and concrete. In order to explore the bonding properties of reinforced concrete with rebar HRB600 under stable corrosion rates, the pull-out tests were carried out on 36 anchorage specimens of bond between rebar HRB600 and high-strength concrete under stable corrosion rates, and the characteristics of the bonding strength and its influencing factors were analyzed. Finally, the variable laws of influencing factors on the bonding properties were calculated by test data under the relatively stable corrosion rates, and the calculation formula of the ultimate bonding strength was fitted.
Corrosion of steel is an important factor affecting the bonding properties of steel and concrete. In order to explore the bonding properties of reinforced concrete with rebar HRB600 under stable corrosion rates, the pull-out tests were carried out on 36 anchorage specimens of bond between rebar HRB600 and high-strength concrete under stable corrosion rates, and the characteristics of the bonding strength and its influencing factors were analyzed. Finally, the variable laws of influencing factors on the bonding properties were calculated by test data under the relatively stable corrosion rates, and the calculation formula of the ultimate bonding strength was fitted.
2020, 50(10): 32-38.
doi: 10.13204/j.gyjzG20070703
Abstract:
Gas stations as parts of the urban infrastructure are the basis for the normal operation of social economy. They are also signs of the development of urban modernization. The quantitative analysis of the service capacity and service area for a gas station is an important guarantee of planning and constructing gas station retionally. In the paper, the distance attenuation theory was introduced and the relationship between service capacity of a gas station and space distances was analyzed. The attenuation coefficient that affected the results of the analysis was studied. Finally, taking the Tangshan towns gas station in Jiangning District as an example, the quantitative analysis of service capacity of the gas station was carried out and proposed an optimization strategy. Research results indicated that:the mothed could reflect the impact of distance decay on service capacity and scope of a gas station. And it could accurately draw the status of service capacity and service area for existing gas stations. This method was more accurate than the traditional service radius method. It could provide reference to rational planning and construction for the gas station
Gas stations as parts of the urban infrastructure are the basis for the normal operation of social economy. They are also signs of the development of urban modernization. The quantitative analysis of the service capacity and service area for a gas station is an important guarantee of planning and constructing gas station retionally. In the paper, the distance attenuation theory was introduced and the relationship between service capacity of a gas station and space distances was analyzed. The attenuation coefficient that affected the results of the analysis was studied. Finally, taking the Tangshan towns gas station in Jiangning District as an example, the quantitative analysis of service capacity of the gas station was carried out and proposed an optimization strategy. Research results indicated that:the mothed could reflect the impact of distance decay on service capacity and scope of a gas station. And it could accurately draw the status of service capacity and service area for existing gas stations. This method was more accurate than the traditional service radius method. It could provide reference to rational planning and construction for the gas station
2020, 50(10): 39-42,48.
doi: 10.13204/j.gyjzG20051704
Abstract:
Urban high-density development is not equal to high volume-ratio development, super high-rise building complexes are not simply a function of space superposition. Under the guidance of planning concept of "small blocks, dense road network", the overall layout, traffic organization and functional layout of super high-rise buildings are restricted and influenced, strategies and measures of architectural design are needed to achieve the deep integration of super high-rise buildings and urban high-density blocks. From the points of multidimensional traffic organization and 3D spatial integration, some design strategies were put forward, such as the combination of pedestrian system and commercial moving line, the sharing of motor vehicle entrances and exits, the creation of open urban public spaces, and the integration of underground space boundary height. Planning and integrating the interior and exterior of the super high-rise building complex as well as the ground and underground system, it was wanted to promote efficiency in high density blocks to build a "vertical city" under high-density blocks.
Urban high-density development is not equal to high volume-ratio development, super high-rise building complexes are not simply a function of space superposition. Under the guidance of planning concept of "small blocks, dense road network", the overall layout, traffic organization and functional layout of super high-rise buildings are restricted and influenced, strategies and measures of architectural design are needed to achieve the deep integration of super high-rise buildings and urban high-density blocks. From the points of multidimensional traffic organization and 3D spatial integration, some design strategies were put forward, such as the combination of pedestrian system and commercial moving line, the sharing of motor vehicle entrances and exits, the creation of open urban public spaces, and the integration of underground space boundary height. Planning and integrating the interior and exterior of the super high-rise building complex as well as the ground and underground system, it was wanted to promote efficiency in high density blocks to build a "vertical city" under high-density blocks.
2020, 50(10): 43-48.
doi: 10.13204/j.gyjzG20021906
Abstract:
With the continuous promotion of sustainable development strategies and the concept of urban ecological civilization construction, the requirements for the regeneration and reconstruction project for old factory areas were constantly improved.Through field investigations, in-depth research and literature review, a value assessment model for regeneration and reconstruction of old plant areas was established. From the perspective on sustainable development, taking the regeneration and reconstruction project of Fenglei Instrument Factory as an example, mathematical statistics and qualitative analysis were carried out. Analyzing the five aspects of space safety, investment values, cultural values, social values, and ecological values, the reconstruction values of the project were determined. The project reconstruction plan was adjusted at the same time, the strategies of regeneration and reconstruction for existing projects was researched.
With the continuous promotion of sustainable development strategies and the concept of urban ecological civilization construction, the requirements for the regeneration and reconstruction project for old factory areas were constantly improved.Through field investigations, in-depth research and literature review, a value assessment model for regeneration and reconstruction of old plant areas was established. From the perspective on sustainable development, taking the regeneration and reconstruction project of Fenglei Instrument Factory as an example, mathematical statistics and qualitative analysis were carried out. Analyzing the five aspects of space safety, investment values, cultural values, social values, and ecological values, the reconstruction values of the project were determined. The project reconstruction plan was adjusted at the same time, the strategies of regeneration and reconstruction for existing projects was researched.
2020, 50(10): 49-56.
doi: 10.13204/j.gyjzG20042403
Abstract:
In the paper, a new fabricated wood-structure wallboard-dovetail-mortise-and-tenon joint wood-structure wallboard, was presented. In order to explore thermal performances of wood structure wallboards, 5 kinds of wallboard specimens were fabricated, and the average heat transfer coefficient was measured by the temperature control box-heat flowmeter method. Based on the 5 insulation materials, theoretical calculation of thermodynamic performances for the wallboards was conducted, and 5 finite element models were modelled by ANSYS, the thermal performance simulation analysis of composite wallboards was made, the comparisons of the test results with the energy-saving standard limit values and the theoretical calculation values showed that the wallboard with XPS plate internal could meet the cold and cold rural area or urban residential energy-saving regmiments. The experimental values were in good agreement with the two calculated values, and the reliability of thermal performances was verified by each other. Finally, ANSYS was used to simulate the thermal performances of 15 groups of XPS panels with different thickness, and a recommended thermal resistance calculation formula was put forward.
In the paper, a new fabricated wood-structure wallboard-dovetail-mortise-and-tenon joint wood-structure wallboard, was presented. In order to explore thermal performances of wood structure wallboards, 5 kinds of wallboard specimens were fabricated, and the average heat transfer coefficient was measured by the temperature control box-heat flowmeter method. Based on the 5 insulation materials, theoretical calculation of thermodynamic performances for the wallboards was conducted, and 5 finite element models were modelled by ANSYS, the thermal performance simulation analysis of composite wallboards was made, the comparisons of the test results with the energy-saving standard limit values and the theoretical calculation values showed that the wallboard with XPS plate internal could meet the cold and cold rural area or urban residential energy-saving regmiments. The experimental values were in good agreement with the two calculated values, and the reliability of thermal performances was verified by each other. Finally, ANSYS was used to simulate the thermal performances of 15 groups of XPS panels with different thickness, and a recommended thermal resistance calculation formula was put forward.
2020, 50(10): 57-62.
doi: 10.13204/j.gyjz201908060008
Abstract:
Eight full-scale reinforced concrete (RC) beams were tested for fire resistance. The effect of boundary conditions, shear span to effective depth ratios, stirrup spacings on shear properties of beams at high temperature was analyzed. The thermal fields within beams, variations of temperature of reinforcing bars, vertical and horizontal displacement and crack developing modes of beams were studied. The fire resistance of RC beams with different parameters was compared. The results showed that the shear span to effective depth ratios had significant influence on shear properties of beams at high temperature, with shear span to effective depth ratios decreased, the fire resistance of beams was improved, however, the failure characteristics of beams were obviously brittle. With stirrup spacings of beams increased, fire resistance of beams was decreased in fire. Different from at room temperature, fire resistance of simply supported beams was better than that of restrained beams, due to internal force redistribution of beams at high temperature.
Eight full-scale reinforced concrete (RC) beams were tested for fire resistance. The effect of boundary conditions, shear span to effective depth ratios, stirrup spacings on shear properties of beams at high temperature was analyzed. The thermal fields within beams, variations of temperature of reinforcing bars, vertical and horizontal displacement and crack developing modes of beams were studied. The fire resistance of RC beams with different parameters was compared. The results showed that the shear span to effective depth ratios had significant influence on shear properties of beams at high temperature, with shear span to effective depth ratios decreased, the fire resistance of beams was improved, however, the failure characteristics of beams were obviously brittle. With stirrup spacings of beams increased, fire resistance of beams was decreased in fire. Different from at room temperature, fire resistance of simply supported beams was better than that of restrained beams, due to internal force redistribution of beams at high temperature.
2020, 50(10): 63-68.
doi: 10.13204/j.gyjzG20061211
Abstract:
There is a current research hotspot on performances of monolithic structure joints composite prestressed concrete slabs. A new monolithic structure joint of composite prestressed concrete slab was proposed, in which the rebars of the prefabricated panel were outstretched with oblique crossing, and several additional rebars were placed close to the top of the prefabricated panel. The experimental results showed that the rebars oblique-cross details of steel bars in the prefabricated panel could effectively transfer the forces between two prefabricated panels. The mechanical performances of the new joint were superior to that of the cast-in-place panel, and the specimens were destroyed on both sides of the joint. Stirrups were used to replace the truss bar, and neither the precast layer nor the composite layer of the composite concrete slab at the joint of the specimen was not disengaged when the specimen was destroyed. It indicated that stirrup bars could effectively limit the development of cracks in the precast and composite layers of concrete. The experimental results of the composite concrete slab with different thickness showed that the bearing capacity and deformation capacity of the new joint could meet the design requirements. It could provide a new idea for design of long-span composite prestressed bi-directional concrete slabs.
There is a current research hotspot on performances of monolithic structure joints composite prestressed concrete slabs. A new monolithic structure joint of composite prestressed concrete slab was proposed, in which the rebars of the prefabricated panel were outstretched with oblique crossing, and several additional rebars were placed close to the top of the prefabricated panel. The experimental results showed that the rebars oblique-cross details of steel bars in the prefabricated panel could effectively transfer the forces between two prefabricated panels. The mechanical performances of the new joint were superior to that of the cast-in-place panel, and the specimens were destroyed on both sides of the joint. Stirrups were used to replace the truss bar, and neither the precast layer nor the composite layer of the composite concrete slab at the joint of the specimen was not disengaged when the specimen was destroyed. It indicated that stirrup bars could effectively limit the development of cracks in the precast and composite layers of concrete. The experimental results of the composite concrete slab with different thickness showed that the bearing capacity and deformation capacity of the new joint could meet the design requirements. It could provide a new idea for design of long-span composite prestressed bi-directional concrete slabs.
2020, 50(10): 69-75.
doi: 10.13204/j.gyjz201906280002
Abstract:
In order to study the accumulative damage evolution law of fatigue for viaducts under impact dynamic response of trains, the 32-meter prestressed-concrete box girder of the Beijing-Tianjin Intercity High-Speed Railway was taken as a prototype to design and manufacture three scale-model beams. A multi-stage variable-amplitude fatigue-loading test was performed on the model beam. The design and fabrication of scale-model beams and the loading and acquisition process of multi-stage variable-amplitude fatigue-loading test were introduced. The development of crack and sensitive damage locations of box girders under fatigue load, as well as fatigue evolution laws and generation mechanism of deflection, rebar and concrete strain were studied. It was concluded that the fatigue of box griders should pay more attention to web parts; the larger the fatigue amplitude, the larger the mechanical indicators such as deflection, rebars and concrete strain, and the more serious the accumulative damage of griders.
In order to study the accumulative damage evolution law of fatigue for viaducts under impact dynamic response of trains, the 32-meter prestressed-concrete box girder of the Beijing-Tianjin Intercity High-Speed Railway was taken as a prototype to design and manufacture three scale-model beams. A multi-stage variable-amplitude fatigue-loading test was performed on the model beam. The design and fabrication of scale-model beams and the loading and acquisition process of multi-stage variable-amplitude fatigue-loading test were introduced. The development of crack and sensitive damage locations of box girders under fatigue load, as well as fatigue evolution laws and generation mechanism of deflection, rebar and concrete strain were studied. It was concluded that the fatigue of box griders should pay more attention to web parts; the larger the fatigue amplitude, the larger the mechanical indicators such as deflection, rebars and concrete strain, and the more serious the accumulative damage of griders.
2020, 50(10): 76-86,93.
doi: 10.13204/j.gyjzGYJZ201805160003
Abstract:
In view of light weight and small stiffness of the new type of cable-grider emergency bridges, vehicle-bridge coupling vibration is worth studying. The vibration differential equations of the vehicle-bridge system were established by the dynamic equilibrium theory and finite element method, and the Newmark-β method was used to solve the differential equations. Analysis programs of vehicle-bridge coupling vibration programming by APDL language in ANSYS, to analyse the dynamic responses of bridges in different connection types of main girders, vehicle speeds, vehicle masses, road surface grades and damping ratios of the bridge. The results indicated that connection types of main girders had a significant impact on vibration responses of bridges, especially on vertical vibration displacement and axial stress of suspenders. With the vehicle velocity increase, although the peak reponses of different location in grider spans were of different trends, the mean responses of vibration increased fundamentally. The dynamic responses of bridges kept close relationships with road surface grade of of bridges, especially with vertical vibration acceleration. With the vehicle-weight increase,the dynamic responses increased linearly. The dynamic responses decreased with the increase of damping ratios of bridges, but the amplitudes changed slightly. The analysis revealed that the vehicle weight could not exceed 30 tons and the vehicle speed coult not exceed 30 km/h. The scheme of emergency bridges needed further improvement if the safeguard capacity needed to be increase.
In view of light weight and small stiffness of the new type of cable-grider emergency bridges, vehicle-bridge coupling vibration is worth studying. The vibration differential equations of the vehicle-bridge system were established by the dynamic equilibrium theory and finite element method, and the Newmark-β method was used to solve the differential equations. Analysis programs of vehicle-bridge coupling vibration programming by APDL language in ANSYS, to analyse the dynamic responses of bridges in different connection types of main girders, vehicle speeds, vehicle masses, road surface grades and damping ratios of the bridge. The results indicated that connection types of main girders had a significant impact on vibration responses of bridges, especially on vertical vibration displacement and axial stress of suspenders. With the vehicle velocity increase, although the peak reponses of different location in grider spans were of different trends, the mean responses of vibration increased fundamentally. The dynamic responses of bridges kept close relationships with road surface grade of of bridges, especially with vertical vibration acceleration. With the vehicle-weight increase,the dynamic responses increased linearly. The dynamic responses decreased with the increase of damping ratios of bridges, but the amplitudes changed slightly. The analysis revealed that the vehicle weight could not exceed 30 tons and the vehicle speed coult not exceed 30 km/h. The scheme of emergency bridges needed further improvement if the safeguard capacity needed to be increase.
A CALCULATION METHOD FOR BEARING CAPACITY OF FOUNDATION UNDER DEEPLY EXCAVATED OR HIGH FILLED SLOPES
2020, 50(10): 87-93.
doi: 10.13204/j.gyjzG20062004
Abstract:
With regard to foundation bearing capacity evaluation related to the basal stability of deep excavation and high filled steep slopes, the weak points of the methods in current engineering practice were discussed, and then an improved calculation method was proposed with reference to the idea first presented by Terzaghi. The improved method took account of the shear stress on the vertical fracture surface in the slope, and made it clear that the foundation bearing capacity should be calculated according to the unilateral slip failure mode, and adopted the more suitable second definition of the safety factor. A complete set of formulas was given, and its rationality and accuracy were validated through comparative calculations with the much refined method of finite element limit analysis.
With regard to foundation bearing capacity evaluation related to the basal stability of deep excavation and high filled steep slopes, the weak points of the methods in current engineering practice were discussed, and then an improved calculation method was proposed with reference to the idea first presented by Terzaghi. The improved method took account of the shear stress on the vertical fracture surface in the slope, and made it clear that the foundation bearing capacity should be calculated according to the unilateral slip failure mode, and adopted the more suitable second definition of the safety factor. A complete set of formulas was given, and its rationality and accuracy were validated through comparative calculations with the much refined method of finite element limit analysis.
2020, 50(10): 94-100,10.
doi: 10.13204/j.gyjzG20031005
Abstract:
It's more prone to bending damage for the embankment supported with rigid pile composite foundation in soft soil areas under the action of seismic loads, even leading to serious damage and other serious consequences. The pile-soil interaction and the subgrade failure under the action of seismic loads were simulated by the discontinuous layout optimization (DLO) method. Also, the characteristics of deformation and load transfer between piles and soil and failure mechanisms of the piles and embankment were studied with different quantities and embeded depths of piles, and different quantities or distribution of higher stiffness piles. The results showed that the numerical results were similar to the ones of the model test. Under the action of the same seismic loads, the closer the piles to the center of the embankment was, the lower the bending moment of piles was. The bending failure of piles appeared more easily than shear failure. Under the seismic action, progressive failure would occur more easily between piles below embankments.
It's more prone to bending damage for the embankment supported with rigid pile composite foundation in soft soil areas under the action of seismic loads, even leading to serious damage and other serious consequences. The pile-soil interaction and the subgrade failure under the action of seismic loads were simulated by the discontinuous layout optimization (DLO) method. Also, the characteristics of deformation and load transfer between piles and soil and failure mechanisms of the piles and embankment were studied with different quantities and embeded depths of piles, and different quantities or distribution of higher stiffness piles. The results showed that the numerical results were similar to the ones of the model test. Under the action of the same seismic loads, the closer the piles to the center of the embankment was, the lower the bending moment of piles was. The bending failure of piles appeared more easily than shear failure. Under the seismic action, progressive failure would occur more easily between piles below embankments.
2020, 50(10): 101-105.
doi: 10.13204/j.gyjzG19121607
Abstract:
The discontinuity is an important characteristic of engineering rock mass, and the seepage characteristic is generally an important factor affecting its stability. In order to further study the seepage characteristic of rock discontinuity, the interface form of natural discontinuity was simplified to be a regular serrated shape, and the artificial rock discontinuity was cast by gypsum, and a series of shearing and seepage coupling tests was carried out to investigate the hydraulic and mechanical properties subjected to discontinuity shearing. The test results showed that the shearing strength of regular serrated interface discontinuity was closely related to serrated angles, normal loading and seepage pressure; the shearing strength decreased obveriously and hydraulic apertures enlarged a lot under high seepage pressure because of softening effect on discontinuity subjected to seepage pressure; the cutting tooth effect was more significant with the increase of seepage pressure during shearing process.
The discontinuity is an important characteristic of engineering rock mass, and the seepage characteristic is generally an important factor affecting its stability. In order to further study the seepage characteristic of rock discontinuity, the interface form of natural discontinuity was simplified to be a regular serrated shape, and the artificial rock discontinuity was cast by gypsum, and a series of shearing and seepage coupling tests was carried out to investigate the hydraulic and mechanical properties subjected to discontinuity shearing. The test results showed that the shearing strength of regular serrated interface discontinuity was closely related to serrated angles, normal loading and seepage pressure; the shearing strength decreased obveriously and hydraulic apertures enlarged a lot under high seepage pressure because of softening effect on discontinuity subjected to seepage pressure; the cutting tooth effect was more significant with the increase of seepage pressure during shearing process.
2020, 50(10): 106-110,62.
doi: 10.13204/j.gyjzG20010110
Abstract:
The creep model described rock materials under freeze-thaw cycles was established in the light of shale in tunnels of the western cold region. And the rock-like material specimens made of cement, sand and fly ash were cast, and after different freezing-thawing cycle tests, uniaxial creep tests were carried out. Finally, the creep characteristics of tunnel surrounding rock in cold regions were simulated by ABAQUS and obtained the stress failure law of "tunnel vault-sidewall-arch bottom". The results showed that:1) the creep model of Nishihara, temperature dampers and NVPB model could describe the creep characteristics of rock-like materials under freeze-thaw cycles; 2) the strain increased greatly with the increase of loads and time. The extent of damage was gradually increased and the deformation resistance was weakened with the increase of freeze-thaw cycles; 3) the maximum stress of tunnel surrounding rock in cold regions was mainly concentrated at the interface between the vault and sidewall, and between the bottom and sidewall.
The creep model described rock materials under freeze-thaw cycles was established in the light of shale in tunnels of the western cold region. And the rock-like material specimens made of cement, sand and fly ash were cast, and after different freezing-thawing cycle tests, uniaxial creep tests were carried out. Finally, the creep characteristics of tunnel surrounding rock in cold regions were simulated by ABAQUS and obtained the stress failure law of "tunnel vault-sidewall-arch bottom". The results showed that:1) the creep model of Nishihara, temperature dampers and NVPB model could describe the creep characteristics of rock-like materials under freeze-thaw cycles; 2) the strain increased greatly with the increase of loads and time. The extent of damage was gradually increased and the deformation resistance was weakened with the increase of freeze-thaw cycles; 3) the maximum stress of tunnel surrounding rock in cold regions was mainly concentrated at the interface between the vault and sidewall, and between the bottom and sidewall.
2020, 50(10): 111-116,121.
doi: 10.13204/j.gyjzG19102507
Abstract:
To study dynamic mechanical properties of freeze-thaw deteriorated concrete under frozen conditions, uniaxial compressive loading tests at different strain rates (1.0×10-5,1.0×10-4,5.0×10-4,1.0×10-3,5.0×10-3 and 5.0×10-3 s-1) after different freeze-thaw cycles (0,10,20,30 and 40 cycles) were carried out with a 10 MN dynamic and static triaxial apparatus.The variation laws of peak stress with different strain rates and degrees of freeze-thaw deterioration were studied.The sensitivity of strain rates and degrees of freeze-thaw deterioration to strength was analyzed.The results showed that at the same degree of freeze-thaw deterioration,the peak stress of frozen concrete increased with increase of the strain rate;increasing with freeze-thaw degrees,the peak stress of frozen concrete increased first and then decreased, without significant difference in failure modes.The slower the strain rate was, the more serious the exfoliation of mortar was on the surface of concrete, and more coarse aggregates were exposed.When strain rates were high,the main cracks on the surface of concrete were very clear.The uniaxial compressive strength of concrete under frozen states still was of a rate effect,and the bonding effect of porous ice crystals on concrete compostion world gradually change to isolation effect with the increase of contents.The sensitivity of freeze-thaw degradation degrees to peak stress was higher than that of strain rates to peak stress.
To study dynamic mechanical properties of freeze-thaw deteriorated concrete under frozen conditions, uniaxial compressive loading tests at different strain rates (1.0×10-5,1.0×10-4,5.0×10-4,1.0×10-3,5.0×10-3 and 5.0×10-3 s-1) after different freeze-thaw cycles (0,10,20,30 and 40 cycles) were carried out with a 10 MN dynamic and static triaxial apparatus.The variation laws of peak stress with different strain rates and degrees of freeze-thaw deterioration were studied.The sensitivity of strain rates and degrees of freeze-thaw deterioration to strength was analyzed.The results showed that at the same degree of freeze-thaw deterioration,the peak stress of frozen concrete increased with increase of the strain rate;increasing with freeze-thaw degrees,the peak stress of frozen concrete increased first and then decreased, without significant difference in failure modes.The slower the strain rate was, the more serious the exfoliation of mortar was on the surface of concrete, and more coarse aggregates were exposed.When strain rates were high,the main cracks on the surface of concrete were very clear.The uniaxial compressive strength of concrete under frozen states still was of a rate effect,and the bonding effect of porous ice crystals on concrete compostion world gradually change to isolation effect with the increase of contents.The sensitivity of freeze-thaw degradation degrees to peak stress was higher than that of strain rates to peak stress.
2020, 50(10): 117-121.
doi: 10.13204/j.gyjzG19113018
Abstract:
Raman spectroscopy, XRD, backscattered electronic images and Mott-Schottky plots were used to explore the redox properties and charge transport characteristics in mill scales of rebars in saturated Ca(OH)2 solution. The results showed that mill scales of rebars could be inwardly oxidized during anodic polarization, and the Fe3O4 in the surface layer of the mill scale was transformed into α-Fe2O3. Reduction happened when it was cathodically polarized, and the α-Fe2O3 in the skin layer disappeared. No new phase was found at the matrix-scale interface. Rebars with mill scales had an n-type semiconductor transporting characteristics in saturated Ca(OH)2 solution and the main carriers were interstitial iron ions.
Raman spectroscopy, XRD, backscattered electronic images and Mott-Schottky plots were used to explore the redox properties and charge transport characteristics in mill scales of rebars in saturated Ca(OH)2 solution. The results showed that mill scales of rebars could be inwardly oxidized during anodic polarization, and the Fe3O4 in the surface layer of the mill scale was transformed into α-Fe2O3. Reduction happened when it was cathodically polarized, and the α-Fe2O3 in the skin layer disappeared. No new phase was found at the matrix-scale interface. Rebars with mill scales had an n-type semiconductor transporting characteristics in saturated Ca(OH)2 solution and the main carriers were interstitial iron ions.
2020, 50(10): 122-128.
doi: 10.13204/j.gyjzG19110401
Abstract:
In order to study the effect of steel fibers and polypropylene fibers on frost resistance of concrete under different environmental conditions, freeze-thaw media, fiber types, fiber contents and acted loads were chosen as variables. Based on the rapid freezing and thawing, the relative elastic modulus, mass loss, compressive strength, flexural strength and bending toughness of fiber reinforced concrete were determined. The results showed that the damage degree of concrete under different factors was ranked from large to small as:loads + chloride + freeze-thaw effect, chloride + freeze-thaw effect, and single freeze-thaw cycle effect, and mixing fibers could reduce freeze-thaw damage effectively. In the case of water freezing and salt freezing, the inclusion of polypropylene fiber could reduce the mass loss and the relative elastic modulus of concrete significantly. Adding 40 kg/m3 steel fibers into concrete matrices could improve the compressive strength and flexural strength after freeze and thaw cycles and improve the flexural toughness of concrete under combined action of loads, chloride salt and freeze-thaw cycles greatly, steel fibers could play a more important role in improving the mechanical properties than polypropylene fibers.
In order to study the effect of steel fibers and polypropylene fibers on frost resistance of concrete under different environmental conditions, freeze-thaw media, fiber types, fiber contents and acted loads were chosen as variables. Based on the rapid freezing and thawing, the relative elastic modulus, mass loss, compressive strength, flexural strength and bending toughness of fiber reinforced concrete were determined. The results showed that the damage degree of concrete under different factors was ranked from large to small as:loads + chloride + freeze-thaw effect, chloride + freeze-thaw effect, and single freeze-thaw cycle effect, and mixing fibers could reduce freeze-thaw damage effectively. In the case of water freezing and salt freezing, the inclusion of polypropylene fiber could reduce the mass loss and the relative elastic modulus of concrete significantly. Adding 40 kg/m3 steel fibers into concrete matrices could improve the compressive strength and flexural strength after freeze and thaw cycles and improve the flexural toughness of concrete under combined action of loads, chloride salt and freeze-thaw cycles greatly, steel fibers could play a more important role in improving the mechanical properties than polypropylene fibers.
2020, 50(10): 129-132,169.
doi: 10.13204/j.gyjzG19111504
Abstract:
Splitting tensile test was conducted on concrete reinforced by 3D steel fibers with single hooked end, as well as 4D and 5D steel fibers with multiple hooked-ends. Then the effects of concrete matrix strength, volume fractions and types of steel fibers on the splitting tensile strength of steel-fiber-reinforced concrete (SFRC) were studied. The results showed that steel fibers could improve the unity of concrete after being damaged. To concrete of grade C40 and C60, the reinforcement of steel fibers could be exploited, thus the splitting tensile strength of SFRC was increased. Also, increasing the volume fractions of steel fibers from 0% to 1.4% was beneficial to improvement of splitting tensile strength of SFRC, especially that the comcrete with 4D and 5D steel fibers was better than that one with 3D steel fibers. Finally, according to the standard JG/T 472-2015 Steel Fiber Reiforced Concrete, a calculation method to predict splitting tensile strength of concrete reinforced by steel fibers with multiple hooked-ends was proposed and showed a good agreement with the test results.
Splitting tensile test was conducted on concrete reinforced by 3D steel fibers with single hooked end, as well as 4D and 5D steel fibers with multiple hooked-ends. Then the effects of concrete matrix strength, volume fractions and types of steel fibers on the splitting tensile strength of steel-fiber-reinforced concrete (SFRC) were studied. The results showed that steel fibers could improve the unity of concrete after being damaged. To concrete of grade C40 and C60, the reinforcement of steel fibers could be exploited, thus the splitting tensile strength of SFRC was increased. Also, increasing the volume fractions of steel fibers from 0% to 1.4% was beneficial to improvement of splitting tensile strength of SFRC, especially that the comcrete with 4D and 5D steel fibers was better than that one with 3D steel fibers. Finally, according to the standard JG/T 472-2015 Steel Fiber Reiforced Concrete, a calculation method to predict splitting tensile strength of concrete reinforced by steel fibers with multiple hooked-ends was proposed and showed a good agreement with the test results.
2020, 50(10): 133-137.
doi: 10.13204/j.gyjzG20042207
Abstract:
The incremental launching construction technique has been widely used in bridge construction due to its low requirements for bridge foundations and construction spaces, and still high construction efficiency, etc. To date the walking incremental launching construction technique for steel box girders of long-span bridges has been studied by finite element simulation or analyzed by construction monitoring data, and few studies combined these two. Based on the Xiabulong Bridge, a finite element model using MIDAS/Civil was modelling to simulate its mechanical properties under representative construction stages, including stress of the most unfavorable section for the steel box girder in eath constrution case and the displacement of the guide beam front end, and the monitoring data from the field test were used for comparative analysis. The results indicated that the stress state of the steel box girder cross-section and the maximum displacement of the guide beam front end calculated by the FE model were in good agreement with the actual construction data, and the errors were less than 15%.
The incremental launching construction technique has been widely used in bridge construction due to its low requirements for bridge foundations and construction spaces, and still high construction efficiency, etc. To date the walking incremental launching construction technique for steel box girders of long-span bridges has been studied by finite element simulation or analyzed by construction monitoring data, and few studies combined these two. Based on the Xiabulong Bridge, a finite element model using MIDAS/Civil was modelling to simulate its mechanical properties under representative construction stages, including stress of the most unfavorable section for the steel box girder in eath constrution case and the displacement of the guide beam front end, and the monitoring data from the field test were used for comparative analysis. The results indicated that the stress state of the steel box girder cross-section and the maximum displacement of the guide beam front end calculated by the FE model were in good agreement with the actual construction data, and the errors were less than 15%.
2020, 50(10): 138-144.
doi: 10.13204/j.gyjz201907310011
Abstract:
A kind of two-end-linear-truss-string structure was studied, and the finite element models of circular-arc truss string structure and two-end-linear-truss-string structure with different end inclination angles were modelled. The difference of internal forces between the two structures was analyzed by the equivalent method of solid web section, and the steel consumption and mechanical properties of the two structures were compared through calculation and analysis under typical loads. The results showed that the steel consumption of the two-end-linear-truss-string structure with the optimal inclination angle of 60° could be saved by about 7% to 18% compared with the circular-arc truss string structure; the combined displacement of the two-end-linear-truss-string structure was larger, but less than the requirement in JGJ 257-2012 Technical Specification for Cable Structures; the maximum horizontal support reaction force could be reduced by 15% compared with another structure; the buckling modes of the two structures were similar, and the two-end-linear-truss-string structure had higher stability bearing capacity.
A kind of two-end-linear-truss-string structure was studied, and the finite element models of circular-arc truss string structure and two-end-linear-truss-string structure with different end inclination angles were modelled. The difference of internal forces between the two structures was analyzed by the equivalent method of solid web section, and the steel consumption and mechanical properties of the two structures were compared through calculation and analysis under typical loads. The results showed that the steel consumption of the two-end-linear-truss-string structure with the optimal inclination angle of 60° could be saved by about 7% to 18% compared with the circular-arc truss string structure; the combined displacement of the two-end-linear-truss-string structure was larger, but less than the requirement in JGJ 257-2012 Technical Specification for Cable Structures; the maximum horizontal support reaction force could be reduced by 15% compared with another structure; the buckling modes of the two structures were similar, and the two-end-linear-truss-string structure had higher stability bearing capacity.
2020, 50(10): 145-151.
doi: 10.13204/j.gyjzGYJZ201907150004
Abstract:
In order to study the coupling mechanism of transmission tower-line systems and explore failure modes and mechanisms of ultimate states, an aeroelastic model of transmission tower-line systems considering ultimate states was designed based on a 220 kV transmission tower-line system in Guangdong province. The wind tunnel tests of a single tower and a tow-line system in the turbulent wind field were carried out, and the phenomenon of tower collapese under the ultimate wind load of transmission tower-line systems was reappeared. The comparisons of the results between the finite element analysis and the tests showd that:1) Based on the equivalent design of stable stress, the model of the transmission tower under ultimate states could be simulated the structive failure well in the wind tunnel test. 2)In the case of strong wind, the coupling vibration caused by the tower line system made vibration caused by the tower-line system made vibration of the tower-line system more complicated than that of a single tower in the same environment. The failure might be related to the occurrence of nonlinear internal resonances and local responses to be amplified, and the elastic-plastic instability failure would occured. 3) designing of transmission tower structure, the stable bearing capacity of the middle of the tower along the direction perpendicular to the conductor direction should be strengthened, and the contribution of the across-wind vibration response should not be ignored.
In order to study the coupling mechanism of transmission tower-line systems and explore failure modes and mechanisms of ultimate states, an aeroelastic model of transmission tower-line systems considering ultimate states was designed based on a 220 kV transmission tower-line system in Guangdong province. The wind tunnel tests of a single tower and a tow-line system in the turbulent wind field were carried out, and the phenomenon of tower collapese under the ultimate wind load of transmission tower-line systems was reappeared. The comparisons of the results between the finite element analysis and the tests showd that:1) Based on the equivalent design of stable stress, the model of the transmission tower under ultimate states could be simulated the structive failure well in the wind tunnel test. 2)In the case of strong wind, the coupling vibration caused by the tower line system made vibration caused by the tower-line system made vibration of the tower-line system more complicated than that of a single tower in the same environment. The failure might be related to the occurrence of nonlinear internal resonances and local responses to be amplified, and the elastic-plastic instability failure would occured. 3) designing of transmission tower structure, the stable bearing capacity of the middle of the tower along the direction perpendicular to the conductor direction should be strengthened, and the contribution of the across-wind vibration response should not be ignored.
2020, 50(10): 152-159,193.
doi: 10.13204/j.gyjzG19111310
Abstract:
An experimental research of 6 high-strength-concrete-filled high-strength-steel square-tube (HCHSST) stub columns subjected to biaxial eccentric loading was performed. The mechanical properties of the members with different eccentricity (0.27 to 0.80) and steel yield strength (554 to 896 MPa) were studied. The finite element analysis models of HCHSST stub columns under biaxial eccentric loading were established by the finite element analysis software ABAQUS.The numerical results were in good agreement with the experimental results, and the whole loading processes of the typical members and influence factors were analyzed. The results showed that concrete strength, steel yield strength and steel ratios had a little bit of influences on the initial stiffness of the load-lateral deflection curves of members. However, eccentricity had a relatively large influence on the initial stiffness of members, the ultimate bearing capacity of members increased with the increase of concrete strength, steel yield strength and steel ratios, and decreased with the increase of eccentricity. The ductility of members increased with the increase of eccentricity and steel ratios, and decreased with the increase of concrete strength.
An experimental research of 6 high-strength-concrete-filled high-strength-steel square-tube (HCHSST) stub columns subjected to biaxial eccentric loading was performed. The mechanical properties of the members with different eccentricity (0.27 to 0.80) and steel yield strength (554 to 896 MPa) were studied. The finite element analysis models of HCHSST stub columns under biaxial eccentric loading were established by the finite element analysis software ABAQUS.The numerical results were in good agreement with the experimental results, and the whole loading processes of the typical members and influence factors were analyzed. The results showed that concrete strength, steel yield strength and steel ratios had a little bit of influences on the initial stiffness of the load-lateral deflection curves of members. However, eccentricity had a relatively large influence on the initial stiffness of members, the ultimate bearing capacity of members increased with the increase of concrete strength, steel yield strength and steel ratios, and decreased with the increase of eccentricity. The ductility of members increased with the increase of eccentricity and steel ratios, and decreased with the increase of concrete strength.
2020, 50(10): 160-169.
doi: 10.13204/j.gyjzG20020406
Abstract:
The pseudo-static tests and simulations of six walls with different spacings frames vertical limbs and foam concrete densities PX-1, PX-2, PX-3, PX-4, PX-5 and PX-6 were finished up. The bearing performances of walls under different spacings of vevtical limbs and the densities of foam concrete were studied, the test and simulation results showed that:at the beginning of loading, the wall had no obvious sign of cracking. At the later stage of loading, the number of cracks on the wall gradually increased, the crack width became larger. At that time, although the internal steel frames of the wall still had a large bearing capacity, the overall shear and compression performances of the wall decreased. Under the condition that the spacing and layout of the steel frame were the same, the densities of the foam concrete had a greater impact on the axial bearing capacity performance of walls, and as densities of foam concrete increased, the overall bearing capacity of the wall also increased. The combined wall had good bearing performances.
The pseudo-static tests and simulations of six walls with different spacings frames vertical limbs and foam concrete densities PX-1, PX-2, PX-3, PX-4, PX-5 and PX-6 were finished up. The bearing performances of walls under different spacings of vevtical limbs and the densities of foam concrete were studied, the test and simulation results showed that:at the beginning of loading, the wall had no obvious sign of cracking. At the later stage of loading, the number of cracks on the wall gradually increased, the crack width became larger. At that time, although the internal steel frames of the wall still had a large bearing capacity, the overall shear and compression performances of the wall decreased. Under the condition that the spacing and layout of the steel frame were the same, the densities of the foam concrete had a greater impact on the axial bearing capacity performance of walls, and as densities of foam concrete increased, the overall bearing capacity of the wall also increased. The combined wall had good bearing performances.
2020, 50(10): 170-179,198.
doi: 10.13204/j.gyjzG20020408
Abstract:
In the paper, the three composite concrete two-way slabs of SXB-1, SXB-2, and SXB-3 reinforced with cold-formed thin-wall square steel tubes and with a density of 1 600 kg/m3 of foam concrete were tested and compared by FEM simulations. The failure phenomena of the three composite two-way slabs and the mechanical performance of the composite concrete two-way slabs were got. Influence of different spacings of tubes on the baring capatity performances of composite concrete two-way slabs was analyzed. Taking as the wall thickness of the section steel tubes, the strength of the section steel, and the spacing of the section steel as control variables, the effect on the mechanical properties of the composite concrete two-way slab was studied. The results showed that:the composite concrete slabs had good bearing performances in the X and Y directions, and the cracks at the bottom of the slabs at the time of failure eventually showed intersecting butterfly shape or X-shape development; the smaller the section spacing, the higher the stiffness and bearing capacity of the composite concrete slabs, the smaller the deflection and strain; as the section wall thickness increased, the steel material strength increased, the grid sizes decreased, the strength and rigidity of the steel frame itself, increased and the same as the the composite concrete two-way slabs.
In the paper, the three composite concrete two-way slabs of SXB-1, SXB-2, and SXB-3 reinforced with cold-formed thin-wall square steel tubes and with a density of 1 600 kg/m3 of foam concrete were tested and compared by FEM simulations. The failure phenomena of the three composite two-way slabs and the mechanical performance of the composite concrete two-way slabs were got. Influence of different spacings of tubes on the baring capatity performances of composite concrete two-way slabs was analyzed. Taking as the wall thickness of the section steel tubes, the strength of the section steel, and the spacing of the section steel as control variables, the effect on the mechanical properties of the composite concrete two-way slab was studied. The results showed that:the composite concrete slabs had good bearing performances in the X and Y directions, and the cracks at the bottom of the slabs at the time of failure eventually showed intersecting butterfly shape or X-shape development; the smaller the section spacing, the higher the stiffness and bearing capacity of the composite concrete slabs, the smaller the deflection and strain; as the section wall thickness increased, the steel material strength increased, the grid sizes decreased, the strength and rigidity of the steel frame itself, increased and the same as the the composite concrete two-way slabs.
2020, 50(10): 180-186,75.
doi: 10.13204/j.gyjz201904140005
Abstract:
Shear walls are main lateral resistance members of high-rise and super-high-rise buildings, which are very important to the seismic performances of building structures. The pseudo-static analysis of seven hybrid FRP-steel-reinforced concrete shear walls with axial compression ratios of 0.2, 0.3 and 0.4 were simulated by finite element analysis software ABAQUS. The effects of axial compression ratios and mechanical properties of FRP bars on hysteretic properties, skeleton curves, seismic characteristics and residual deformation of shear walls were studied. The damage development characteristics of shear walls were compared and analyzed. The results showed that the longitudinal reinforcement in the edge members of RC shear walls with FRP bars could effectively decrease the residual deformation of shear walls, improve the ductility of the shear wall, and promote the joint work of reinforcement bars and concrete. The higher the strength or elastic modulus of FRP bars was, the more obvious the effect was, but the lower the energy consumption capacity of walls ware. With the increase of the axial compression, the ultimate bearing capacity of shear walls with FRP bars gradually increased, and the ultimate lateral displacement gradually increased when the axial compression ratios were less than 0.3, the adverse effect of the axial compression ratio on residual deformation of walls were small, and when axial compression ratios were greater than 0.3, the adverse effect of the axial compression ratio on residual deformation of walls increased sharply.
Shear walls are main lateral resistance members of high-rise and super-high-rise buildings, which are very important to the seismic performances of building structures. The pseudo-static analysis of seven hybrid FRP-steel-reinforced concrete shear walls with axial compression ratios of 0.2, 0.3 and 0.4 were simulated by finite element analysis software ABAQUS. The effects of axial compression ratios and mechanical properties of FRP bars on hysteretic properties, skeleton curves, seismic characteristics and residual deformation of shear walls were studied. The damage development characteristics of shear walls were compared and analyzed. The results showed that the longitudinal reinforcement in the edge members of RC shear walls with FRP bars could effectively decrease the residual deformation of shear walls, improve the ductility of the shear wall, and promote the joint work of reinforcement bars and concrete. The higher the strength or elastic modulus of FRP bars was, the more obvious the effect was, but the lower the energy consumption capacity of walls ware. With the increase of the axial compression, the ultimate bearing capacity of shear walls with FRP bars gradually increased, and the ultimate lateral displacement gradually increased when the axial compression ratios were less than 0.3, the adverse effect of the axial compression ratio on residual deformation of walls were small, and when axial compression ratios were greater than 0.3, the adverse effect of the axial compression ratio on residual deformation of walls increased sharply.
2020, 50(10): 187-193.
doi: 10.13204/j.gyjzG20011609
Abstract:
Based on verification of fimite element analysis results with relevant experiment data, the axial compression properties of concrete-encased concrete-filled steel tubular (CFST) stub columns at room temperatures, post-fire and strengthened with cladding steel after exposure to fire were studied.The effects of fire exposure time, intervals of batten plate and thickness of cladding steel on the bearing capacity and axial stiffness of specimens were analyzed. The results showed that strengthened with cladding steel, the bearing capacity and stiffness of the specimens were obviously improved, even exceeding the ones of specimens at room temperature. Through parameter analysis, it was found that the degree of reduction for bearing capacity of specimens had experienced a process of increasing first and then decreasing, and the effects of repaired specimens with cladding steel were gradually weakened. The bearing capacity gradually decreased with the increase of intervals of batten plates, but the reduction was small, and the stiffness of specimens was evidently affected. Increasing the thickness of the clading steel could obviously improve the bearing capacity of specimens, and improve their stiffness more significantly.
Based on verification of fimite element analysis results with relevant experiment data, the axial compression properties of concrete-encased concrete-filled steel tubular (CFST) stub columns at room temperatures, post-fire and strengthened with cladding steel after exposure to fire were studied.The effects of fire exposure time, intervals of batten plate and thickness of cladding steel on the bearing capacity and axial stiffness of specimens were analyzed. The results showed that strengthened with cladding steel, the bearing capacity and stiffness of the specimens were obviously improved, even exceeding the ones of specimens at room temperature. Through parameter analysis, it was found that the degree of reduction for bearing capacity of specimens had experienced a process of increasing first and then decreasing, and the effects of repaired specimens with cladding steel were gradually weakened. The bearing capacity gradually decreased with the increase of intervals of batten plates, but the reduction was small, and the stiffness of specimens was evidently affected. Increasing the thickness of the clading steel could obviously improve the bearing capacity of specimens, and improve their stiffness more significantly.
ARCHITECTURAL DESIGN OF THE MEMORIAL HALL FOR RED SISTER-IN-LAWS IN YIMEMG AREA IN THE LOCAL CONTEXT
2020, 50(10): 194-198.
doi: 10.13204/j.gyjzG20032905
Abstract:
The locality expressed by Red Buildings of villages can effectively highlight the symbolic meaning and connotative characteristics of Red Cultures.Through analysis and explanation of the on-site design concepts of rural Red Buildings, combined with the detailed introduction of the architectural design for the Memorial Hall of the Red Sister-in-Laws in Yimeng, the three aspects of local identities in the project-interpretation of topographic features, local translation of human histories, and local utilization of construction techniques were interpreted, which was wanteds to provide reference to design of rural Red exhibitions Buildings in the new ear.
The locality expressed by Red Buildings of villages can effectively highlight the symbolic meaning and connotative characteristics of Red Cultures.Through analysis and explanation of the on-site design concepts of rural Red Buildings, combined with the detailed introduction of the architectural design for the Memorial Hall of the Red Sister-in-Laws in Yimeng, the three aspects of local identities in the project-interpretation of topographic features, local translation of human histories, and local utilization of construction techniques were interpreted, which was wanteds to provide reference to design of rural Red exhibitions Buildings in the new ear.
