Login
Register
E-alert
2020 Vol. 50, No. 11
Display Method:
2020, 50(11): 1-5.
doi: 10.13204/j.gyjzG20042401
Abstract:
As an important supplementary type of urban green space, post-industrial landscape reconstruction method based on different classification protection system is still subjective and uncertain. Faced with the industrial logic, realistic event logic and ecological logic in the reconstruction design, through the case analysis of Beijing Shougang capital steel landscape reconstruction, the paper put forward the method of landscape reconstruction based on the logic of difference stratification, which was to establish the space skeleton of the site, to deal with the stratification structure and to harmonize the relationship between the layers, so as to provide a reference for the future related projects.
As an important supplementary type of urban green space, post-industrial landscape reconstruction method based on different classification protection system is still subjective and uncertain. Faced with the industrial logic, realistic event logic and ecological logic in the reconstruction design, through the case analysis of Beijing Shougang capital steel landscape reconstruction, the paper put forward the method of landscape reconstruction based on the logic of difference stratification, which was to establish the space skeleton of the site, to deal with the stratification structure and to harmonize the relationship between the layers, so as to provide a reference for the future related projects.
2020, 50(11): 6-10.
doi: 10.13204/j.gyjzG20072115
Abstract:
Shougang park is currently a larger urban renewal project in China. Under the background of a series of events such as policy guidance, urban revitalization, industrial transformation and cultural and creative activities, how to reasonably and effectively protect Shougang industrial heritage, the coordinated development with economy, society and environment is an important problem to realize the urban renewal of the old industrial park in the west of Beijing.Through the practice of the reconstruction and utilization of the 3rd blast furnace museum of Shougang, this paper probed into the reconstruction methods of protection and utilization of the industrial heritage from four aspects of retaining the rust color original appearance,highlighting the industrial mark, constructing the charming dynamic line, and constructing the night scene lighting, with a view to providing a reference for the follow-up renovation.
Shougang park is currently a larger urban renewal project in China. Under the background of a series of events such as policy guidance, urban revitalization, industrial transformation and cultural and creative activities, how to reasonably and effectively protect Shougang industrial heritage, the coordinated development with economy, society and environment is an important problem to realize the urban renewal of the old industrial park in the west of Beijing.Through the practice of the reconstruction and utilization of the 3rd blast furnace museum of Shougang, this paper probed into the reconstruction methods of protection and utilization of the industrial heritage from four aspects of retaining the rust color original appearance,highlighting the industrial mark, constructing the charming dynamic line, and constructing the night scene lighting, with a view to providing a reference for the follow-up renovation.
2020, 50(11): 11-17,45.
doi: 10.13204/j.gyjzG201908100003
Abstract:
Taking the factory and enterprise buildings of the small third-line construction in western Anhui as the research object, the research of investigation, preservation and regeneration was carried out through field reconnaissance combined with literature sorting. Firstly, the background status, spatial pattern and architectural features of the industrial heritage of the small third-line in western Anhui were analyzed by the crossover method of architecture and industrial archaeology. Then the paper combined the tourism economic characteristics of Dabie mountains in western Anhui with the environmental characteristics of "backer, concealment and dispersion" of the construction of small third-line, and explored the internal mechanism and technical path of dualistic symbiosis between industrial heritage and rural tourism. Finally, this paper analyzed the interpretation and survival of the historical and cultural value of the industrial heritage in western Anhui from the perspectives of historical research, industrial heritage protection and rural revitalization.
Taking the factory and enterprise buildings of the small third-line construction in western Anhui as the research object, the research of investigation, preservation and regeneration was carried out through field reconnaissance combined with literature sorting. Firstly, the background status, spatial pattern and architectural features of the industrial heritage of the small third-line in western Anhui were analyzed by the crossover method of architecture and industrial archaeology. Then the paper combined the tourism economic characteristics of Dabie mountains in western Anhui with the environmental characteristics of "backer, concealment and dispersion" of the construction of small third-line, and explored the internal mechanism and technical path of dualistic symbiosis between industrial heritage and rural tourism. Finally, this paper analyzed the interpretation and survival of the historical and cultural value of the industrial heritage in western Anhui from the perspectives of historical research, industrial heritage protection and rural revitalization.
2020, 50(11): 18-24,56.
doi: 10.13204/j.gyjzG19102310
Abstract:
The academic circles have paid earlier attention and research on the activation and renewal of large or medium-sized industrial heritages such as iron and steel plants, textile mills, and railways. However, there is little writing about the future development and activation and renewal strategies of light industrial heritage such as tea factories. Taking Xindi Tea Factory in Fuliang County, Jingde zhen as an example, the paper proposed an oriented activation strategy based on a value perspective by analyzing the tea plant's renewal demands and heritage values, with a view to providing references for the revitalization of small-sized light industrial heritage.
The academic circles have paid earlier attention and research on the activation and renewal of large or medium-sized industrial heritages such as iron and steel plants, textile mills, and railways. However, there is little writing about the future development and activation and renewal strategies of light industrial heritage such as tea factories. Taking Xindi Tea Factory in Fuliang County, Jingde zhen as an example, the paper proposed an oriented activation strategy based on a value perspective by analyzing the tea plant's renewal demands and heritage values, with a view to providing references for the revitalization of small-sized light industrial heritage.
2020, 50(11): 25-31.
doi: 10.13204/j.gyjzG20021803
Abstract:
The royal rear garden in Bianjing of the Jin Dynasty was considered to be a physical heritage from Dongjing of the Northern Song Dynasty. After Comparing and analyzing a large number of literatures, it was found that the royal rear garden built in Dongjing of the Northern Song Dynasty was burned out in the regin of Wanyan Liang, and the royal rear garden of the Jin Dynasty was reconstructed in the period, whose orientation, style and architectural concept had been changed. In the Northern Song Dynasty, the quantity and volume of buildings in the royal rear garden were large, artificial mountains were not very prominent, which were almost mounds and were displayed strong political imagery, resonating with the style of royal gardens the Sui and Tang Dynasties. The quantity and volume of buildings in the royal rear garden of the Jin Dynasty decreased significantly, and large-scale artificial mountains were adopted, and political functions were weakened. The differences between garden styles were related to the function, status and construction times of them. The uniqueness of the architectural style for the royal rear garden in Bianjing of the Jin Dynasty verified the existence of Kaifeng Royal Garden in the Jin Dynasty.
The royal rear garden in Bianjing of the Jin Dynasty was considered to be a physical heritage from Dongjing of the Northern Song Dynasty. After Comparing and analyzing a large number of literatures, it was found that the royal rear garden built in Dongjing of the Northern Song Dynasty was burned out in the regin of Wanyan Liang, and the royal rear garden of the Jin Dynasty was reconstructed in the period, whose orientation, style and architectural concept had been changed. In the Northern Song Dynasty, the quantity and volume of buildings in the royal rear garden were large, artificial mountains were not very prominent, which were almost mounds and were displayed strong political imagery, resonating with the style of royal gardens the Sui and Tang Dynasties. The quantity and volume of buildings in the royal rear garden of the Jin Dynasty decreased significantly, and large-scale artificial mountains were adopted, and political functions were weakened. The differences between garden styles were related to the function, status and construction times of them. The uniqueness of the architectural style for the royal rear garden in Bianjing of the Jin Dynasty verified the existence of Kaifeng Royal Garden in the Jin Dynasty.
2020, 50(11): 32-38,132.
doi: 10.13204/j.gyjzG20011603
Abstract:
The concrete printing process of one-by-one extrusion and layer forming makes the mechanical properties of the printed concrete material show obvious anisotropy. In addition, the reinforcement method is limited by the printing process. Rebar can only be placed between horizontal layers and then laminated to print. The bonding performance between concrete and steel bars is affected by many factors such as printing process and steel bar placement. In this paper, the effects of steel bar diameter, strength of printed concrete, printing technology and placement of steel bar on the bonding properties of steel bar and printed concrete were studied by designing orthogonal experiment. It is concluded that the method of printing along the lines should be preferentially used and the method of embedding the reinforcing bars should be buried to improve the bonding performance between the reinforcing bars and the printed concrete.
The concrete printing process of one-by-one extrusion and layer forming makes the mechanical properties of the printed concrete material show obvious anisotropy. In addition, the reinforcement method is limited by the printing process. Rebar can only be placed between horizontal layers and then laminated to print. The bonding performance between concrete and steel bars is affected by many factors such as printing process and steel bar placement. In this paper, the effects of steel bar diameter, strength of printed concrete, printing technology and placement of steel bar on the bonding properties of steel bar and printed concrete were studied by designing orthogonal experiment. It is concluded that the method of printing along the lines should be preferentially used and the method of embedding the reinforcing bars should be buried to improve the bonding performance between the reinforcing bars and the printed concrete.
2020, 50(11): 39-45.
doi: 10.13204/j.gyjzG19122311
Abstract:
In order to study the seismic behavior of ECC composite columns, four ECC columns and one RC column were tested under axial force and lateral cyclic loading. On this basis, ABAQUS was used to analyze the ECC composite columns. The test results showed that the hysteresis curves of torque T-twist rate θ of the five specimens were all in inverse S-shape, and the pinch phenomenon was obvious; increasing fiber volume ratio, reducing stirrup spacing and increasing shear span ratio could slow down the degradation of strength and stiffness; under the same parameters, the peak torque and cumulative energy dissipation capacity of reinforced ECC columns were 1.65 times and 6.89 times of RC columns respectively, which showed that the hysteretic performance of reinforced ECC columns was better than that of RC columns.In addition, the simulation results of hysteretic curve of reinforced ECC columns were basically consistent with the test results, which showed that it was feasible to use ABAQUS to simulate the seismic behavior of reinforced ECC composite columns. Finally, the influence of different parameters on the seismic behavior of ECC composite columns was studied.
In order to study the seismic behavior of ECC composite columns, four ECC columns and one RC column were tested under axial force and lateral cyclic loading. On this basis, ABAQUS was used to analyze the ECC composite columns. The test results showed that the hysteresis curves of torque T-twist rate θ of the five specimens were all in inverse S-shape, and the pinch phenomenon was obvious; increasing fiber volume ratio, reducing stirrup spacing and increasing shear span ratio could slow down the degradation of strength and stiffness; under the same parameters, the peak torque and cumulative energy dissipation capacity of reinforced ECC columns were 1.65 times and 6.89 times of RC columns respectively, which showed that the hysteretic performance of reinforced ECC columns was better than that of RC columns.In addition, the simulation results of hysteretic curve of reinforced ECC columns were basically consistent with the test results, which showed that it was feasible to use ABAQUS to simulate the seismic behavior of reinforced ECC composite columns. Finally, the influence of different parameters on the seismic behavior of ECC composite columns was studied.
2020, 50(11): 46-51.
doi: 10.13204/j.gyjzG19102703
Abstract:
Based on the concept of "strong horizontal seam and weak vertical seam" of prefabricated shear wall structure, the specimens of the prefabricated shear wall and the cast-in-place shear wall were designed.Based on the results of quasi-static loading test,the results showed that the overall working performance of the shear wall connected by damper was good, the bearing capacity was not very different from that of the cast-in-place shear wall specimen, but the ductility coefficient was obviously better than that of the cast-in-place shear wall specimen.The damper dissipated energy in the process of force, and played a certain protective role on the wall. In the process of force, the wall could meet the design requirements.
Based on the concept of "strong horizontal seam and weak vertical seam" of prefabricated shear wall structure, the specimens of the prefabricated shear wall and the cast-in-place shear wall were designed.Based on the results of quasi-static loading test,the results showed that the overall working performance of the shear wall connected by damper was good, the bearing capacity was not very different from that of the cast-in-place shear wall specimen, but the ductility coefficient was obviously better than that of the cast-in-place shear wall specimen.The damper dissipated energy in the process of force, and played a certain protective role on the wall. In the process of force, the wall could meet the design requirements.
2020, 50(11): 52-56.
doi: 10.13204/j.gyjzG19081103
Abstract:
An experimental study on shear performances of fiber-reinforced self-compacting concrete T-beam was carried out. Eight simple-supported T-beams subjected to two concentrated loading placed symmetrically were tested, to study the influences of fiber types, fiber contents and diameters, spacings and strength of stirrups on ultimate shear capacity, shear-force-displacement curves, longitudinal rebar strain and failure modes. The experimental results showed that the ultimate shear capacity of T-beams increased due steel fibers of being mixed or hybrid fibers. Fibers could restricted strain propagation of longitudinal rebars, delay appearance and development of cracks and change failure modes from brittle shear collapse into ductile flexural failure. The stirrups could be partially replaced by steel fibers or hybrid fibers. The design requirements for contents or strength of stirrups for beams could were reduced in combination with fibers and stirrups.
An experimental study on shear performances of fiber-reinforced self-compacting concrete T-beam was carried out. Eight simple-supported T-beams subjected to two concentrated loading placed symmetrically were tested, to study the influences of fiber types, fiber contents and diameters, spacings and strength of stirrups on ultimate shear capacity, shear-force-displacement curves, longitudinal rebar strain and failure modes. The experimental results showed that the ultimate shear capacity of T-beams increased due steel fibers of being mixed or hybrid fibers. Fibers could restricted strain propagation of longitudinal rebars, delay appearance and development of cracks and change failure modes from brittle shear collapse into ductile flexural failure. The stirrups could be partially replaced by steel fibers or hybrid fibers. The design requirements for contents or strength of stirrups for beams could were reduced in combination with fibers and stirrups.
2020, 50(11): 57-64.
doi: 10.13204/j.gyjzG20010811
Abstract:
In order to study the seismic behavior of diagrid core-tube structure in high-rise buildings under frequent and rare earthquakes, according to the Guangzhou West Tower project, the diagrid core-tube structure was established in accordance with the Code for Seismic Design of Buildings(GB 50011-2010). Based on the principle of equal material consumption, the traditional frame-shear wall structure with the same consumption of materials as the diagrid core-tube structure was established. On this basis, the distribution laws of lateral stiffness, shear lag, internal and external tube shear force and overturning moment of the structure, the development and failure extent of plastic hinge, the collapse mechanism and the ductility of the structure were compared and analyzed. The results showed that the diagrid core-tube structure had stronger spatial overall collaborative stress performance compared with the traditional frame shear-wall structure, and the effect of the outer tube of the inclined column on the overall stiffness was obvious, and the growth of the harmful inter-story drift ratio was far less than that of the diagrid core-tube structure. Diagrid core-tube structure had higher importance of outer tube inclined column, less plastic hinge development, less energy consumption capacity and poor ductility. Therefore, the design of strength and stability of the inclined columns of outer tube was the key to ensure that the entire structure will not collapse under the rare earthquake.
In order to study the seismic behavior of diagrid core-tube structure in high-rise buildings under frequent and rare earthquakes, according to the Guangzhou West Tower project, the diagrid core-tube structure was established in accordance with the Code for Seismic Design of Buildings(GB 50011-2010). Based on the principle of equal material consumption, the traditional frame-shear wall structure with the same consumption of materials as the diagrid core-tube structure was established. On this basis, the distribution laws of lateral stiffness, shear lag, internal and external tube shear force and overturning moment of the structure, the development and failure extent of plastic hinge, the collapse mechanism and the ductility of the structure were compared and analyzed. The results showed that the diagrid core-tube structure had stronger spatial overall collaborative stress performance compared with the traditional frame shear-wall structure, and the effect of the outer tube of the inclined column on the overall stiffness was obvious, and the growth of the harmful inter-story drift ratio was far less than that of the diagrid core-tube structure. Diagrid core-tube structure had higher importance of outer tube inclined column, less plastic hinge development, less energy consumption capacity and poor ductility. Therefore, the design of strength and stability of the inclined columns of outer tube was the key to ensure that the entire structure will not collapse under the rare earthquake.
2020, 50(11): 65-70.
doi: 10.13204/j.gyjz201904290005
Abstract:
The finite element model was established by using ABAQUS software to simulate push-out test of perfobond rib shear connector. The influence of perforated rebar on the shear capacity of perfobond rib shear connector was studied. The results showed that the results of the nonlinear finite element method calculation agreed well with the experimental results. The finite element method could simulate true force bearing behavior of perfobond rib shear connector. The yield strength and diameter of rebar had significant influence on the ultimate shear strength of perfobond rib shear connector. With the increase of yield strength and diameter of the rebar, the shear capacity of perfobond rib shear connector also increased linearly. The length and position of perforated rebar had little influence on the ultimate shear capacity of perfobond rib shear connector. Based on the research results, the relationships between shear capacity and yield strength, diameter and length of perforated rebar were presented.
The finite element model was established by using ABAQUS software to simulate push-out test of perfobond rib shear connector. The influence of perforated rebar on the shear capacity of perfobond rib shear connector was studied. The results showed that the results of the nonlinear finite element method calculation agreed well with the experimental results. The finite element method could simulate true force bearing behavior of perfobond rib shear connector. The yield strength and diameter of rebar had significant influence on the ultimate shear strength of perfobond rib shear connector. With the increase of yield strength and diameter of the rebar, the shear capacity of perfobond rib shear connector also increased linearly. The length and position of perforated rebar had little influence on the ultimate shear capacity of perfobond rib shear connector. Based on the research results, the relationships between shear capacity and yield strength, diameter and length of perforated rebar were presented.
2020, 50(11): 71-77,111.
doi: 10.13204/j.gyjzG20020501
Abstract:
To quantify damage of ancient timber structures under ambient excitation, according to the lamination theory, a method was proposed to divide wood into damaged surface layers and undamaged middle layers by layered solid elements of the finite element method. The damage depth was taken as a new variable, combined with the total energy-change rates of wavelets as feature parameters and input into an improved BP neural network, and the reduction ratios of elastic moduli were considered as output parameters. Appling the method respectively to multi-scale models of a timber frame and Xi'an Bell Tower, the result showed that the maximum error of identification results was less than 2%, which meant it feasible to simulate wood damage by layered solid elements and adopt the damage depth as a parameter to quantify the damage of wood beams, which could provide reference for the study of damage early warning and local damage analysis of complex structures under ambient excitation
To quantify damage of ancient timber structures under ambient excitation, according to the lamination theory, a method was proposed to divide wood into damaged surface layers and undamaged middle layers by layered solid elements of the finite element method. The damage depth was taken as a new variable, combined with the total energy-change rates of wavelets as feature parameters and input into an improved BP neural network, and the reduction ratios of elastic moduli were considered as output parameters. Appling the method respectively to multi-scale models of a timber frame and Xi'an Bell Tower, the result showed that the maximum error of identification results was less than 2%, which meant it feasible to simulate wood damage by layered solid elements and adopt the damage depth as a parameter to quantify the damage of wood beams, which could provide reference for the study of damage early warning and local damage analysis of complex structures under ambient excitation
2020, 50(11): 78-81,70.
doi: 10.13204/j.gyjzG19121616
Abstract:
In order to study the influence of matrix suction on shear strength of expansive soil in Hefei under different initial dry densities in a large suction range, direct shear tests of expansive soil under different initial dry densities and moisture contents were carried out, the matric suction at shear surfaces of shear specimens was measured by the filter paper method, the influence of dry densities and matric suction on shear strength indexes of expansive soil in Hefei was analyzed. The experimental results showed that dry densities and matric suction had significant effect on the cohesion of the expansive soil, but little effect on the internal friction angles; when the matrix suction value ranged from 0 and 400 kPa, the effect of dry densities on cohesion was great; when the cohesion was over 400 kPa, the effect of dry densities on cohesion was weakened; there was a good linear relationship between cohesion and logarithm of matric suction; the shear strength of expansive soil increased nonlinearly with the increase of matric suction, and the growth rate decreased gradually.
In order to study the influence of matrix suction on shear strength of expansive soil in Hefei under different initial dry densities in a large suction range, direct shear tests of expansive soil under different initial dry densities and moisture contents were carried out, the matric suction at shear surfaces of shear specimens was measured by the filter paper method, the influence of dry densities and matric suction on shear strength indexes of expansive soil in Hefei was analyzed. The experimental results showed that dry densities and matric suction had significant effect on the cohesion of the expansive soil, but little effect on the internal friction angles; when the matrix suction value ranged from 0 and 400 kPa, the effect of dry densities on cohesion was great; when the cohesion was over 400 kPa, the effect of dry densities on cohesion was weakened; there was a good linear relationship between cohesion and logarithm of matric suction; the shear strength of expansive soil increased nonlinearly with the increase of matric suction, and the growth rate decreased gradually.
2020, 50(11): 82-90.
doi: 10.13204/j.gyjzG20042102
Abstract:
To reveal the mechanisms of hazards induced by leakage of groundwater and sand under different water pressure, DEM-CFD method was adopted to simulate leaking processes based on a laboratory model test. Considering the effect of water leakage into the traditional gravity flow test, the numerical analysis model by DEM-CFD method was built. The variations of soil and water loss patterns, loss amounts, soil deformation, forces on the bottom plate of the testing chamber and soil stress were studied. The results showed that the soil zone of loose ellipse induced by a leaking process was influenced by both the soil loss and water leakage. A fast-flowing zone existed near the leaking point, and a hydraulic channel formed with the development of the leaking process. High water pressure increased the width of hydraulic channels. The amounts of leakage flow and ground surface movement went through a slow development stage and a sudden increasement stage, the high water pressure widened hydraulic channels. The loss of water and soil occured in the stages of slow development and sudden increasement, the high water pressure mainly influenced the sudden increasement stage. Besides, soil loss led to occurrence of the sudden increasement stage directly. During the water-sand leaking process, the variation process of forces on the bottom plate of the testing chamber could be divided into three stages:the steep decreasing stage, the slow decreasing stage and the relative stability stage. The leaking process induced the occurrence of soil arches. High water pressure made the soil arch more prone to be damaged, which caused more severe soil loss. The process of soil loss and the influence of high water pressure were quite different before and after formation of hydraulic channels.
To reveal the mechanisms of hazards induced by leakage of groundwater and sand under different water pressure, DEM-CFD method was adopted to simulate leaking processes based on a laboratory model test. Considering the effect of water leakage into the traditional gravity flow test, the numerical analysis model by DEM-CFD method was built. The variations of soil and water loss patterns, loss amounts, soil deformation, forces on the bottom plate of the testing chamber and soil stress were studied. The results showed that the soil zone of loose ellipse induced by a leaking process was influenced by both the soil loss and water leakage. A fast-flowing zone existed near the leaking point, and a hydraulic channel formed with the development of the leaking process. High water pressure increased the width of hydraulic channels. The amounts of leakage flow and ground surface movement went through a slow development stage and a sudden increasement stage, the high water pressure widened hydraulic channels. The loss of water and soil occured in the stages of slow development and sudden increasement, the high water pressure mainly influenced the sudden increasement stage. Besides, soil loss led to occurrence of the sudden increasement stage directly. During the water-sand leaking process, the variation process of forces on the bottom plate of the testing chamber could be divided into three stages:the steep decreasing stage, the slow decreasing stage and the relative stability stage. The leaking process induced the occurrence of soil arches. High water pressure made the soil arch more prone to be damaged, which caused more severe soil loss. The process of soil loss and the influence of high water pressure were quite different before and after formation of hydraulic channels.
2020, 50(11): 91-96.
doi: 10.13204/j.gyjzG20031006
Abstract:
Through research and application in deep excavation without horizontal supports, oblique-vertical alternate piles have been popularized gradually in practice and proven effective in controlling deformation and stability of slopes. To study the mechanical characteristics of the technique, a model test and infinite element analysis by Plaxis 2D were performed. The results showed that compared with vertical piles, oblique-vertical alternate piles were more advantageous in controlling deformation and improving stability of slope. The lateral deformation of piles decreased with the increase tilt angles of oblique piles. And when the distances between piles and toes of slopes increased, the lateral deformation and bending moment of piles increased accordingly. In engineering practice, site and construction conditions should be considered to achieve more safety and economic.
Through research and application in deep excavation without horizontal supports, oblique-vertical alternate piles have been popularized gradually in practice and proven effective in controlling deformation and stability of slopes. To study the mechanical characteristics of the technique, a model test and infinite element analysis by Plaxis 2D were performed. The results showed that compared with vertical piles, oblique-vertical alternate piles were more advantageous in controlling deformation and improving stability of slope. The lateral deformation of piles decreased with the increase tilt angles of oblique piles. And when the distances between piles and toes of slopes increased, the lateral deformation and bending moment of piles increased accordingly. In engineering practice, site and construction conditions should be considered to achieve more safety and economic.
2020, 50(11): 97-101.
doi: 10.13204/j.gyjzG19090330
Abstract:
In seismic fortification zones, foundation strengthened by CFG piles needs to be checked for seismic resistance. In view of the fact that there was no specific provisions on adjustment coefficients of seismic bearing capacity for CFG-pile composite foundation in relevant regulations and codes, the paper concluded different methods to determine adjustment coefficients of seismic bearing capacity for CFG-pile composite foundation by combining and analyzing the design and calculation theory of existing regulations and specifications. Through comparative analysis, it was found that in the design and calculation of CFG-pile composite foundation, the adjustment factor ζ'a of seismic bearing capacity for CFG-pile composite foundation was 1.3, which was more reasonable.
In seismic fortification zones, foundation strengthened by CFG piles needs to be checked for seismic resistance. In view of the fact that there was no specific provisions on adjustment coefficients of seismic bearing capacity for CFG-pile composite foundation in relevant regulations and codes, the paper concluded different methods to determine adjustment coefficients of seismic bearing capacity for CFG-pile composite foundation by combining and analyzing the design and calculation theory of existing regulations and specifications. Through comparative analysis, it was found that in the design and calculation of CFG-pile composite foundation, the adjustment factor ζ'a of seismic bearing capacity for CFG-pile composite foundation was 1.3, which was more reasonable.
2020, 50(11): 102-105,31.
doi: 10.13204/j.gyjzG20082406
Abstract:
The bearing capacity of friction piles depends on the shear characteristics of the pile-soil interface. In order to study the influence of moisture content and soil quality conditions on the friction resistance of friction piles, a test device for the pile-soil contact surface shear characteristics of friction piles was designed, and three types of silty clay, silt and fine sand were tested. There were 9 sets of laboratory tests on soil and three kinds of water content. The results showed that the lateral friction resistance of friction piles was hyperbolic with the settlement of the pile. The initial shear stiffness coefficient and the essential settlement for approaching ultimate lateral friction resistance were determined by the type of soil and the moisture content. The initial shear stiffness of fine sand was slightly higher than that of silty clay and fine sand with the same compaction coefficient; while the ultimate lateral frictional resistance of silty clay was higher than that of silty clay and fine sand with the same compaction coefficient; the ultimate frictional resistance of sand changed significantly, but it was relatively insensitive to the change of ultimate frictional resistance of silty clay, and the maximum value of the ultimate frictional resistance occured at the optimal moisture content.
The bearing capacity of friction piles depends on the shear characteristics of the pile-soil interface. In order to study the influence of moisture content and soil quality conditions on the friction resistance of friction piles, a test device for the pile-soil contact surface shear characteristics of friction piles was designed, and three types of silty clay, silt and fine sand were tested. There were 9 sets of laboratory tests on soil and three kinds of water content. The results showed that the lateral friction resistance of friction piles was hyperbolic with the settlement of the pile. The initial shear stiffness coefficient and the essential settlement for approaching ultimate lateral friction resistance were determined by the type of soil and the moisture content. The initial shear stiffness of fine sand was slightly higher than that of silty clay and fine sand with the same compaction coefficient; while the ultimate lateral frictional resistance of silty clay was higher than that of silty clay and fine sand with the same compaction coefficient; the ultimate frictional resistance of sand changed significantly, but it was relatively insensitive to the change of ultimate frictional resistance of silty clay, and the maximum value of the ultimate frictional resistance occured at the optimal moisture content.
2020, 50(11): 106-111.
doi: 10.13204/j.gyjzG19112905
Abstract:
Based on the carbonation test of concrete with various admixtures (fly ash, mineral powder and gangue) in natural exposure environment, the influence of carbonation time and curing time on the early carbonation depth of concrete with admixtures was analyzed. Results showed that the carbonation depth of concrete with admixtures developed very fast within 90 days after pouring, while tended to slowly from 90 days to 180 days due to the phenomenon of alkali return, and the carbonation depth of concrete with admixtures continued to develop and tended to be stable after 180 days. The carbonation depth of concrete with admixtures had a linear relationship with the square root of carbonation time. The early carbonation speed of concrete slowed down with the extension of curing time, and the slowing down degree of concrete with single, double and triple admixtures weakened in turn. Combined with the previous research results, considering the type and amount of admixtures, curing time, carbonation time, carbonation position, water-binder ratio and other factors, the calculation model of early carbonation depth of concrete with admixtures was established, and the applicability of the model was verified by comparing with test results from others.
Based on the carbonation test of concrete with various admixtures (fly ash, mineral powder and gangue) in natural exposure environment, the influence of carbonation time and curing time on the early carbonation depth of concrete with admixtures was analyzed. Results showed that the carbonation depth of concrete with admixtures developed very fast within 90 days after pouring, while tended to slowly from 90 days to 180 days due to the phenomenon of alkali return, and the carbonation depth of concrete with admixtures continued to develop and tended to be stable after 180 days. The carbonation depth of concrete with admixtures had a linear relationship with the square root of carbonation time. The early carbonation speed of concrete slowed down with the extension of curing time, and the slowing down degree of concrete with single, double and triple admixtures weakened in turn. Combined with the previous research results, considering the type and amount of admixtures, curing time, carbonation time, carbonation position, water-binder ratio and other factors, the calculation model of early carbonation depth of concrete with admixtures was established, and the applicability of the model was verified by comparing with test results from others.
2020, 50(11): 112-118,96.
doi: 10.13204/j.gyjzG19122606
Abstract:
In the process of recycling construction waste to produce recycled aggregate, a large number of small particles with particle size less than 0.16 mm, namely recycled micro powder, are produced. These particles have certain activity and can be added into concrete as mineral admixture instead of cement. 10%, 20%, 30% and 40% replacement rates of recycled fine powder were used to replace cement to study the influence of such factors as replacement rate of recycled fine powder and water-binder ratio on the mechanical and frost resistance of recycled fine powder concrete, and to make a comparative study with fly ash concrete prepared by replacing cement with equivalent amount of fly ash. The results showed that the compressive strength of recycled fine powder concrete decreased with the increase of the content of recycled micro powder, but the law of frost resistance was just the opposite. When the water-binder ratio was 0.35, the compressive strength and frost resistance of the recycled fine powder concrete were slightly higher. Under the same conditions, the frost resistance of recycled fine-powder concrete was better than that of ordinary concrete and fly ash concrete. When the water-cement ratio was 0.35 and the recycled fine powder content was 30%, the recycled fine powder concrete had the best frost resistance, and the freeze-thaw cycle could reach 175 times.
In the process of recycling construction waste to produce recycled aggregate, a large number of small particles with particle size less than 0.16 mm, namely recycled micro powder, are produced. These particles have certain activity and can be added into concrete as mineral admixture instead of cement. 10%, 20%, 30% and 40% replacement rates of recycled fine powder were used to replace cement to study the influence of such factors as replacement rate of recycled fine powder and water-binder ratio on the mechanical and frost resistance of recycled fine powder concrete, and to make a comparative study with fly ash concrete prepared by replacing cement with equivalent amount of fly ash. The results showed that the compressive strength of recycled fine powder concrete decreased with the increase of the content of recycled micro powder, but the law of frost resistance was just the opposite. When the water-binder ratio was 0.35, the compressive strength and frost resistance of the recycled fine powder concrete were slightly higher. Under the same conditions, the frost resistance of recycled fine-powder concrete was better than that of ordinary concrete and fly ash concrete. When the water-cement ratio was 0.35 and the recycled fine powder content was 30%, the recycled fine powder concrete had the best frost resistance, and the freeze-thaw cycle could reach 175 times.
2020, 50(11): 119-124.
doi: 10.13204/j.gyjzG20091706
Abstract:
The whole construction process of a super-long super-wide super-rigid seamless multi-story steel frame workshop was simulated and analyzed by using the finite element program MIDAS Gen. The influence of temperature on the construction process was studied from three aspects:the overall structure, the construction steps and the structural closure. The calculation results showed that the environmental temperature was the key factor in the construction stage, the setting of different temperature segments and the use of different divisional closure sequences had an important influence on the internal force of the overall structure. On this basis, the temperature control range, the overall structure construction partition and the optimal closure mode that meet the structural deformation and stress during the construction stage were proposed. The construction of the overall structure was gradually expanded from the middle part along the length direction and installed symmetrically. The optimal closure mode of steel frame in temperature zone was lifted transverse first, then lifted longitudinally and finally poured concrete floor. Setting closure belt was not necessary in the construction of light-weight roof of steel frame. Pouring the steel-concrete composite floor after completing the steel frame was beneficial to reduce the temperature stress of the overall structure. It was suggested that the temperature control range in the construction stage of the project should be at the initial temperature of 15℃, and the temperature rising/falling should above or below 8℃ fulctuation.
The whole construction process of a super-long super-wide super-rigid seamless multi-story steel frame workshop was simulated and analyzed by using the finite element program MIDAS Gen. The influence of temperature on the construction process was studied from three aspects:the overall structure, the construction steps and the structural closure. The calculation results showed that the environmental temperature was the key factor in the construction stage, the setting of different temperature segments and the use of different divisional closure sequences had an important influence on the internal force of the overall structure. On this basis, the temperature control range, the overall structure construction partition and the optimal closure mode that meet the structural deformation and stress during the construction stage were proposed. The construction of the overall structure was gradually expanded from the middle part along the length direction and installed symmetrically. The optimal closure mode of steel frame in temperature zone was lifted transverse first, then lifted longitudinally and finally poured concrete floor. Setting closure belt was not necessary in the construction of light-weight roof of steel frame. Pouring the steel-concrete composite floor after completing the steel frame was beneficial to reduce the temperature stress of the overall structure. It was suggested that the temperature control range in the construction stage of the project should be at the initial temperature of 15℃, and the temperature rising/falling should above or below 8℃ fulctuation.
2020, 50(11): 125-132.
doi: 10.13204/j.gyjzG20070605
Abstract:
Theoretical analysis and numerical simulation analysis methods was used. A study was conducted on the influence of changes in the structural parameters of the prefabricated beam-column high-strength bolted joint on the flexural capacity of the joint.The influences of parameters such as the thickness of the external diaphragm, the width of the external diaphragm, the arc radius of the external diaphragm and the length of the external diaphragm on the flexural capacity of the joint were studied.The research results show that the numerical calculation results of the finite element have achieved good agreement with the experimental and theoretical analysis results. The flexural capacity of the joint is obviously affected by the thickness of the external diaphragm. As the thickness of the external diaphragm increases, the flexural capacity of the joint increases and the ductility decreases. It is recommended that the thickness of the external diaphragm should not be less than the thickness of the beam flange, but should not exceed the thickness of the beam flange by 2 mm. The width of the external diaphragm is increased, which has a certain strengthening effect on the column joint domain. The width of the external diaphragm is limited to a reasonable range, which is beneficial to improve the flexural capacity of the joint.The flexural capacity of the joint is not significantly affected by the length of the external diaphragm. It is recommended that the length of the external diaphragm can meet the lower limit of the high-strength bolt hole construction requirements. Nodal stress transmission is greatly affected by the arc radius. It is recommended that the ratio of the arc radius to the width of the external diaphragm is about 4 times.
Theoretical analysis and numerical simulation analysis methods was used. A study was conducted on the influence of changes in the structural parameters of the prefabricated beam-column high-strength bolted joint on the flexural capacity of the joint.The influences of parameters such as the thickness of the external diaphragm, the width of the external diaphragm, the arc radius of the external diaphragm and the length of the external diaphragm on the flexural capacity of the joint were studied.The research results show that the numerical calculation results of the finite element have achieved good agreement with the experimental and theoretical analysis results. The flexural capacity of the joint is obviously affected by the thickness of the external diaphragm. As the thickness of the external diaphragm increases, the flexural capacity of the joint increases and the ductility decreases. It is recommended that the thickness of the external diaphragm should not be less than the thickness of the beam flange, but should not exceed the thickness of the beam flange by 2 mm. The width of the external diaphragm is increased, which has a certain strengthening effect on the column joint domain. The width of the external diaphragm is limited to a reasonable range, which is beneficial to improve the flexural capacity of the joint.The flexural capacity of the joint is not significantly affected by the length of the external diaphragm. It is recommended that the length of the external diaphragm can meet the lower limit of the high-strength bolt hole construction requirements. Nodal stress transmission is greatly affected by the arc radius. It is recommended that the ratio of the arc radius to the width of the external diaphragm is about 4 times.
2020, 50(11): 133-136.
doi: 10.13204/j.gyjzG201909120001
Abstract:
The non-linear finite element model of high-strength bolts friction type connection is established by finite element software ABAQUS, and the accuracy and applicability of the finite element model are verified by experiments. Finally, the force-displacement curve simplified model of high strength bolt friction connection in friction and sliding stages is established. Its significance lies in:1)Providing structural analysis with more accurate simplified treatment method of joints, improving analysis efficiency on the premise of ensuring accuracy; 2)Applying simplified model to stress analysis of bolts connecting brake plate and bent column of crane girder, clarifying the actual stress situation of bolts and effectively solving bolt loosening problem.
The non-linear finite element model of high-strength bolts friction type connection is established by finite element software ABAQUS, and the accuracy and applicability of the finite element model are verified by experiments. Finally, the force-displacement curve simplified model of high strength bolt friction connection in friction and sliding stages is established. Its significance lies in:1)Providing structural analysis with more accurate simplified treatment method of joints, improving analysis efficiency on the premise of ensuring accuracy; 2)Applying simplified model to stress analysis of bolts connecting brake plate and bent column of crane girder, clarifying the actual stress situation of bolts and effectively solving bolt loosening problem.
2020, 50(11): 137-144,152.
doi: 10.13204/j.gyjzG20011705
Abstract:
The experimental data of circular concrete filled stainless steel tube (CFSST) were collected and compared with the calculation values of current normal concrete filled steel tube codes. The results showed that the calculation values of current codes were more conservative. Therefore, it is necessary to provide a simplified calculation formula for the bearing capacity of CFSST. In view of this, the finite element (FE) model of CFSST member was established, and the parameters affecting the axial compression bearing capacity of CFSST were analyzed by using the FE model. The results showed that the axial compression strength bearing capacity increased with the increase of stainless steel yield strength, concrete strength and steel ratio. Based on the regression of the simplified calculation formula of the strength capacity of CFSST under axial compression, the simplified calculation formula of the stability bearing capacity of CFSST under axial compression was obtained. The simplified formula proposed in this paper was more consistent with the test data than the current codes.
The experimental data of circular concrete filled stainless steel tube (CFSST) were collected and compared with the calculation values of current normal concrete filled steel tube codes. The results showed that the calculation values of current codes were more conservative. Therefore, it is necessary to provide a simplified calculation formula for the bearing capacity of CFSST. In view of this, the finite element (FE) model of CFSST member was established, and the parameters affecting the axial compression bearing capacity of CFSST were analyzed by using the FE model. The results showed that the axial compression strength bearing capacity increased with the increase of stainless steel yield strength, concrete strength and steel ratio. Based on the regression of the simplified calculation formula of the strength capacity of CFSST under axial compression, the simplified calculation formula of the stability bearing capacity of CFSST under axial compression was obtained. The simplified formula proposed in this paper was more consistent with the test data than the current codes.
2020, 50(11): 145-152.
doi: 10.13204/j.gyjzG19121302
Abstract:
In order to study the difference of interface bond performance of recycled concrete filled square and circular steel tube (RCFSST, RCFCST) short column after being subjected to elevated temperatures and spray cooling, 22 RCFSST and 22 RCFCST specimens were designed for push-out test, with the variable parameters of maximum temperature, concrete strength, constant temperature time, anchorage length and cooling mode considered. The mechanical failure pattern of specimens was observed, and the mechanical properties such as bond strength, shear bond stiffness and interface energy dissipation of the specimens were compared and analyzed. The results showed that with the increase of the maximum temperature, the difference of the interface bond performance between the two sections of steel tube subjected to elevated temperatures and spray cooling was large, and the performance indexes of circular specimen were better than those of square specimen. The increase of concrete strength could improve the bond strength between steel tube and concrete. The influence of constant temperature time on the bond strength of square specimen was greater, with the increase of constant temperature time, the change rule of shear bond stiffness of specimens with two cross-section was opposite. With the increase of anchorage length, the interface bond strength would be reduced, which had a greater impact on the shear bond stiffness and energy dissipation capacity of the circular specimens. Compared with the natural cooling specimens, the spray-cooled specimens had lower bond strength and shear bond stiffness, and higher energy dissipation capacity.
In order to study the difference of interface bond performance of recycled concrete filled square and circular steel tube (RCFSST, RCFCST) short column after being subjected to elevated temperatures and spray cooling, 22 RCFSST and 22 RCFCST specimens were designed for push-out test, with the variable parameters of maximum temperature, concrete strength, constant temperature time, anchorage length and cooling mode considered. The mechanical failure pattern of specimens was observed, and the mechanical properties such as bond strength, shear bond stiffness and interface energy dissipation of the specimens were compared and analyzed. The results showed that with the increase of the maximum temperature, the difference of the interface bond performance between the two sections of steel tube subjected to elevated temperatures and spray cooling was large, and the performance indexes of circular specimen were better than those of square specimen. The increase of concrete strength could improve the bond strength between steel tube and concrete. The influence of constant temperature time on the bond strength of square specimen was greater, with the increase of constant temperature time, the change rule of shear bond stiffness of specimens with two cross-section was opposite. With the increase of anchorage length, the interface bond strength would be reduced, which had a greater impact on the shear bond stiffness and energy dissipation capacity of the circular specimens. Compared with the natural cooling specimens, the spray-cooled specimens had lower bond strength and shear bond stiffness, and higher energy dissipation capacity.
2020, 50(11): 153-161,194.
doi: 10.13204/j.gyjzG20020603
Abstract:
In this paper, the finite element parameters of a kind of Z-joint of concrete filled steel tubular L-shaped column and H-shaped steel beam were analyzed. By changing seven parameters, 22 models were established to analyze the mechanical properties of each joint. The analysis showed that the connection of the splice plate at the web could be omitted, and the stiffeners of the weakened upper and lower flange could be used to replace the stiffeners of the rectangular upper and lower flange; increasing the number of high-strength flange bolts could improve the bearing capacity and total energy consumption of the joint, but the ductility performance was reduced; increasing the pretension of flange high-strength bolts could improve the sliding load and total energy consumption, and delay the slip of the joint; increasing the thickness of the upper and lower flange stiffeners could improve the positive peak load and total energy consumption of the joint; increasing the height of the upper and lower flange stiffeners could improve the slip load and total energy consumption of the joint; the upper and lower flange stiffeners could significantly improve the mechanical properties of the joint. Each joint had good ductility and plastic rotation capacity.
In this paper, the finite element parameters of a kind of Z-joint of concrete filled steel tubular L-shaped column and H-shaped steel beam were analyzed. By changing seven parameters, 22 models were established to analyze the mechanical properties of each joint. The analysis showed that the connection of the splice plate at the web could be omitted, and the stiffeners of the weakened upper and lower flange could be used to replace the stiffeners of the rectangular upper and lower flange; increasing the number of high-strength flange bolts could improve the bearing capacity and total energy consumption of the joint, but the ductility performance was reduced; increasing the pretension of flange high-strength bolts could improve the sliding load and total energy consumption, and delay the slip of the joint; increasing the thickness of the upper and lower flange stiffeners could improve the positive peak load and total energy consumption of the joint; increasing the height of the upper and lower flange stiffeners could improve the slip load and total energy consumption of the joint; the upper and lower flange stiffeners could significantly improve the mechanical properties of the joint. Each joint had good ductility and plastic rotation capacity.
2020, 50(11): 162-167.
doi: 10.13204/j.gyjzG19120618
Abstract:
High-strength aluminum alloy has great application prospects in large-scale infrastructure projects due to its corrosion resistance, high strength and good ductility. In this paper, based on the comparative analysis of the commonly used calculation theory of bearing capacity of confined concrete columns under axial compression, the calculation method of bearing capacity of aluminum alloy tubular confined concrete columns was proposed. Then,the finite element model of 7075 high-strength aluminum alloy tubular confined concrete column under axial compression was established by ABAQUS. The finite element simulation results were compared with the calculation results based on the existing experimental results of aluminum alloy tubular confined concrete column. The results showed that the Eurocode 4 did not take the restraint factor of steel pipe on concrete into account, which led to the calculated result biased towards a safe value. The "unified theory" rectangular steel tube calculation formula did not suitable for aluminum alloy confined concrete rectangular column. According to Code for Design of Steel-Concrete composite Structure (DL/T 5085-1999) and Technical specifications for Early-Strength Model Composite Structure Used for Nary Port Emergency Repair in Wartime (GJB 4142-2000), however, the obtained bearing capacity of aluminum alloy tubular confined concrete column was only about 4 percent higher than the finite element simulation value which indicated the finite element simulation results were consistent with the test results. Finally, based on DL/T code and GJB code while treating the constraint effect coefficient as the parameter, the calculation method of axial compressive capacity of concrete column restrained by aluminum alloy tube was proposed.
High-strength aluminum alloy has great application prospects in large-scale infrastructure projects due to its corrosion resistance, high strength and good ductility. In this paper, based on the comparative analysis of the commonly used calculation theory of bearing capacity of confined concrete columns under axial compression, the calculation method of bearing capacity of aluminum alloy tubular confined concrete columns was proposed. Then,the finite element model of 7075 high-strength aluminum alloy tubular confined concrete column under axial compression was established by ABAQUS. The finite element simulation results were compared with the calculation results based on the existing experimental results of aluminum alloy tubular confined concrete column. The results showed that the Eurocode 4 did not take the restraint factor of steel pipe on concrete into account, which led to the calculated result biased towards a safe value. The "unified theory" rectangular steel tube calculation formula did not suitable for aluminum alloy confined concrete rectangular column. According to Code for Design of Steel-Concrete composite Structure (DL/T 5085-1999) and Technical specifications for Early-Strength Model Composite Structure Used for Nary Port Emergency Repair in Wartime (GJB 4142-2000), however, the obtained bearing capacity of aluminum alloy tubular confined concrete column was only about 4 percent higher than the finite element simulation value which indicated the finite element simulation results were consistent with the test results. Finally, based on DL/T code and GJB code while treating the constraint effect coefficient as the parameter, the calculation method of axial compressive capacity of concrete column restrained by aluminum alloy tube was proposed.
2020, 50(11): 168-173.
doi: 10.13204/j.gyjzG201906100004
Abstract:
To study the mechanical behavior of the modular box-type integrated house structure under the horizontal cyclic loading, the quasi-static test of the full-box structure under the combined vertical and horizontal loading was carried. In the test, the vertical load was equivalently replaced by the weight, and the horizontal load was equivalent to the joint load. The overall mechanical behavior of the box was evaluated by the combined effect of the above loads. The test results indicated that the vertical deformation of specimens under the vertical loading was small, and the specimen was not damaged. Under the horizontal cyclic loading, the upper and lower connectors played a good connection. During the entire loading process, most of the strain data of the measuring points were within the elastic range. In the loading and unloading process of the specimen, the specimen was in intact except partial damage and falling off of the partial wall panel and the auxiliary structure, which meet its safety requirements.
To study the mechanical behavior of the modular box-type integrated house structure under the horizontal cyclic loading, the quasi-static test of the full-box structure under the combined vertical and horizontal loading was carried. In the test, the vertical load was equivalently replaced by the weight, and the horizontal load was equivalent to the joint load. The overall mechanical behavior of the box was evaluated by the combined effect of the above loads. The test results indicated that the vertical deformation of specimens under the vertical loading was small, and the specimen was not damaged. Under the horizontal cyclic loading, the upper and lower connectors played a good connection. During the entire loading process, most of the strain data of the measuring points were within the elastic range. In the loading and unloading process of the specimen, the specimen was in intact except partial damage and falling off of the partial wall panel and the auxiliary structure, which meet its safety requirements.
2020, 50(11): 174-177,183.
doi: 10.13204/j.gyjzG20051604
Abstract:
In order to compare the effects of different reinforcement methods on the performance improvement of the damaged bridge members in corrosive environment, four reinforcement methods, such as pasting CFRP sheet, pasting BFRP sheet, anchoring and pasting steel plate and increasing section method, were carried out to analyze the mechanical properties of the corroded reinforced concrete beam bridge members after reinforcement. The bearing capacity, stiffness and safety reserve of the corroded beams under the above four strengthening methods were compared through the test results and theoretical analysis. The results showed that the above four strengthening methods could greatly improve the ultimate bearing capacity of corroded beams, but the yield and failure modes of corroded beams were quite different under different strengthening methods. In addition, the method of anchoring and pasting steel plate had the largest increase in stiffness and the largest safety reserve before damage; the method of pasting CFRP had the second increase in stiffness, but the minimum safety reserve before damage; the method of pasting BFRP and increasing section had the same increase in stiffness of corroded beam and was smaller than that of pasting CFRP, but the safety reserve before damage was better than that of pasting CFRP.
In order to compare the effects of different reinforcement methods on the performance improvement of the damaged bridge members in corrosive environment, four reinforcement methods, such as pasting CFRP sheet, pasting BFRP sheet, anchoring and pasting steel plate and increasing section method, were carried out to analyze the mechanical properties of the corroded reinforced concrete beam bridge members after reinforcement. The bearing capacity, stiffness and safety reserve of the corroded beams under the above four strengthening methods were compared through the test results and theoretical analysis. The results showed that the above four strengthening methods could greatly improve the ultimate bearing capacity of corroded beams, but the yield and failure modes of corroded beams were quite different under different strengthening methods. In addition, the method of anchoring and pasting steel plate had the largest increase in stiffness and the largest safety reserve before damage; the method of pasting CFRP had the second increase in stiffness, but the minimum safety reserve before damage; the method of pasting BFRP and increasing section had the same increase in stiffness of corroded beam and was smaller than that of pasting CFRP, but the safety reserve before damage was better than that of pasting CFRP.
2020, 50(11): 178-183.
doi: 10.13204/j.gyjzG20030608
Abstract:
In order to study the change law of the tensile mechanical properties of CFRP (Carbon Fiber Reinforced Polymer) grids in marine corrosive environment, a single-limb tensile performance test of CFRP grids with different initial stress levels in seawater environment was carried out. The results show that the degree of surface erosion of the CFRP grid increases with aging time, the surface color becomes darker, the original gloss of the matrix is lost, and it becomes rough; the failure mode is from the tensile failure of most specimens in the early stage to the burst failure in the later stage. At the level of (0.6 fu), individual specimens showed layered damage, and the damage was more obvious. In addition, after immersed in seawater for 360 days, the retention rates of tensile strength of CFRP grids with stress levels of 0, 0.3 fu and 0.6 fu were 89.8%, 87.7% and 79.8%, respectively, and the retention rates of elastic modulus were 96.4% and 95.0% and 92.9%, respectively. Indicating that the presence of stress accelerates the degradation of the mesh strength, and as the stress level increases, the degradation of the tensile strength and elastic modulus of the CFRP mesh becomes more obvious.
In order to study the change law of the tensile mechanical properties of CFRP (Carbon Fiber Reinforced Polymer) grids in marine corrosive environment, a single-limb tensile performance test of CFRP grids with different initial stress levels in seawater environment was carried out. The results show that the degree of surface erosion of the CFRP grid increases with aging time, the surface color becomes darker, the original gloss of the matrix is lost, and it becomes rough; the failure mode is from the tensile failure of most specimens in the early stage to the burst failure in the later stage. At the level of (0.6 fu), individual specimens showed layered damage, and the damage was more obvious. In addition, after immersed in seawater for 360 days, the retention rates of tensile strength of CFRP grids with stress levels of 0, 0.3 fu and 0.6 fu were 89.8%, 87.7% and 79.8%, respectively, and the retention rates of elastic modulus were 96.4% and 95.0% and 92.9%, respectively. Indicating that the presence of stress accelerates the degradation of the mesh strength, and as the stress level increases, the degradation of the tensile strength and elastic modulus of the CFRP mesh becomes more obvious.
2020, 50(11): 184-189,167.
doi: 10.13204/j.gyjzG19110801
Abstract:
Based on the method of dimension analysis, the four-floor steel frame structure was designed as existing building(natural period 0.1~0.4 s) and the two-floor steel frame structure was selected as additional story to satisfy simulation ratio. According to the shaking table tests,the seismic behavior of extension-story structure, the isolation effectiveness and mechanism of isolation layer were compared and studied for the fixed base model, base sliding-isolation model, combined isolation model. The dynamic characteristic of prototypes were extrapolated by using finite element software. The results showed that:1)with no base isolation, the added layer would have dramatic increase of the dynamic response due to whiplash effect. 2)After adopting the isolation technology, the dynamic response of superstructures were greatly reduced. The decreasing amplitude ratio and economy of the base sliding isolation were better than the combined isolating system of foundation. Compared with the base sliding isolation, the inter-layer displacement amplitude of combined isolation had been reduced more drastically. 3)The original 4-story structure which the natural vibration period was 0.204 s with 2 added layers, the seismic response of structure was reduced and the seismic behavior of structure was improved after adopting the base isolation.
Based on the method of dimension analysis, the four-floor steel frame structure was designed as existing building(natural period 0.1~0.4 s) and the two-floor steel frame structure was selected as additional story to satisfy simulation ratio. According to the shaking table tests,the seismic behavior of extension-story structure, the isolation effectiveness and mechanism of isolation layer were compared and studied for the fixed base model, base sliding-isolation model, combined isolation model. The dynamic characteristic of prototypes were extrapolated by using finite element software. The results showed that:1)with no base isolation, the added layer would have dramatic increase of the dynamic response due to whiplash effect. 2)After adopting the isolation technology, the dynamic response of superstructures were greatly reduced. The decreasing amplitude ratio and economy of the base sliding isolation were better than the combined isolating system of foundation. Compared with the base sliding isolation, the inter-layer displacement amplitude of combined isolation had been reduced more drastically. 3)The original 4-story structure which the natural vibration period was 0.204 s with 2 added layers, the seismic response of structure was reduced and the seismic behavior of structure was improved after adopting the base isolation.
2020, 50(11): 195-199.
doi: 10.13204/j.gyjzG20050806
Abstract:
The treatment of thermal bridges blocking up of ultra-low energy consumption building caused by curtain wall components has often been overlooked. The impact of these thermal bridges on the energy consumption of the building should not be underestimated. At present, the thermal blocking-up method of these penetrations is variety in different projects, and their impact on energy consumption of the entire building has not been researched. Therefore, combining two project examples in the cold climate zone B, the thermal bridge simulation software and energy consumption calculation software were used to analyze the thermal bridge effect of such joints and the impact on building energy consumption. It is concluded that compared with the tradition design method, the design of thermal bridge blocking-up joint should select thicker insulation materials, smaller size of the increased steel material sections, and shorter steel materials in the insulation layer, so as to help reduce thermal bridge coefficient.
The treatment of thermal bridges blocking up of ultra-low energy consumption building caused by curtain wall components has often been overlooked. The impact of these thermal bridges on the energy consumption of the building should not be underestimated. At present, the thermal blocking-up method of these penetrations is variety in different projects, and their impact on energy consumption of the entire building has not been researched. Therefore, combining two project examples in the cold climate zone B, the thermal bridge simulation software and energy consumption calculation software were used to analyze the thermal bridge effect of such joints and the impact on building energy consumption. It is concluded that compared with the tradition design method, the design of thermal bridge blocking-up joint should select thicker insulation materials, smaller size of the increased steel material sections, and shorter steel materials in the insulation layer, so as to help reduce thermal bridge coefficient.
