Login
Register
E-alert
2021 Vol. 51, No. 6
Display Method:
2021, 51(6): 1-8.
doi: 10.13204/j.gyjz201909110005
Abstract:
3D concrete printing technique has become the main means of intelligent construction because of its advantages of digitalization, automation and intelligence. The paper firstly introduced the basic principle and corresponding approaches of 3D concrete printing. A comparative analysis of domestic and foreign research on the performance requirements of fresh printable concretes, mechanical properties of hardened concrete, concrete rebar settlement technique, structural mechanical properties and construction examples was followed. In addition, a summary of domestic and foreign 3D concrete printing equipment was conducted. Finally, several future research orientations were proposed, included 3D concrete printing with coarse aggregate, mix design for 3D concrete printing, composite reinforcement arrangement technique, applicability analysis for 3D concrete printing technique, assembly printing equipment and platform integration, etc.
3D concrete printing technique has become the main means of intelligent construction because of its advantages of digitalization, automation and intelligence. The paper firstly introduced the basic principle and corresponding approaches of 3D concrete printing. A comparative analysis of domestic and foreign research on the performance requirements of fresh printable concretes, mechanical properties of hardened concrete, concrete rebar settlement technique, structural mechanical properties and construction examples was followed. In addition, a summary of domestic and foreign 3D concrete printing equipment was conducted. Finally, several future research orientations were proposed, included 3D concrete printing with coarse aggregate, mix design for 3D concrete printing, composite reinforcement arrangement technique, applicability analysis for 3D concrete printing technique, assembly printing equipment and platform integration, etc.
2021, 51(6): 9-15.
doi: 10.13204/j.gyjzG21031901
Abstract:
In recent years, 3D printing has attracted widespread attention and has been successfully applied in the field of civil engineering. The layer-by-layer additive manufacturing method gives it a high degree of flexibility, but it is difficult to achieve the simultaneous implantation of the steel cage, which greatly limits its engineering application. Efficient reinforcement and toughening methods are the core and key to the structural application of 3D concrete printing. The toughening methods and research results of 3D printed concrete structures at home and abroad were summarited, the advantages, characteristics, and applicability of various methods were compared and analyzed. This paper aimed to provide scientific and reasonable suggestions for the improvement of bearing safety of 3D printed concrete structures and further promoting the practical application of 3D concrete printing technique.
In recent years, 3D printing has attracted widespread attention and has been successfully applied in the field of civil engineering. The layer-by-layer additive manufacturing method gives it a high degree of flexibility, but it is difficult to achieve the simultaneous implantation of the steel cage, which greatly limits its engineering application. Efficient reinforcement and toughening methods are the core and key to the structural application of 3D concrete printing. The toughening methods and research results of 3D printed concrete structures at home and abroad were summarited, the advantages, characteristics, and applicability of various methods were compared and analyzed. This paper aimed to provide scientific and reasonable suggestions for the improvement of bearing safety of 3D printed concrete structures and further promoting the practical application of 3D concrete printing technique.
2021, 51(6): 16-23.
doi: 10.13204/j.gyjzG20120105
Abstract:
To quantify the buildability performance of 3D printed concrete, according to its rheological characteristics during pumping, extrusion and deposition, a strength failure model based on yield stress and self-weight stress of printing concrete was established. Based on Mohr-Coulomb yield criterion and Tresca failure theory, the quantitative model was suitable for predicting the number of failure layers when plastic yield occurred. At the same time, because it assumed that the loading rate of botton layer was linearized, the model was a lower bound model for conservative prediction, and its correctness was verified by the existing test data and model in the literature. Considering that each layer might produce compression deformation under the gravity of the upper deposited layer, the total compression deformation of the structure after printing was predicted according to Hook's law.
To quantify the buildability performance of 3D printed concrete, according to its rheological characteristics during pumping, extrusion and deposition, a strength failure model based on yield stress and self-weight stress of printing concrete was established. Based on Mohr-Coulomb yield criterion and Tresca failure theory, the quantitative model was suitable for predicting the number of failure layers when plastic yield occurred. At the same time, because it assumed that the loading rate of botton layer was linearized, the model was a lower bound model for conservative prediction, and its correctness was verified by the existing test data and model in the literature. Considering that each layer might produce compression deformation under the gravity of the upper deposited layer, the total compression deformation of the structure after printing was predicted according to Hook's law.
2021, 51(6): 24-28.
doi: 10.13204/j.gyjzG20122904
Abstract:
The requirements of concrete printing technique make it impossible to install stirrups in beam members. Therefore, printed concrete beam members with different truss-type reinforcements were designed, and static loading tests were carried out. Normal section and oblique section failure tests of printed concrete beams with different truss numbers and sizes were carried out respectively. The failure characteristics, load-deflection curves under static load were studied. The test results showed that the flexural capacity of the printed truss-type reinforced concrete beam with appropriate reinforcement was similar to that of the concrete beam with single reinforcement, but the abdominal reinforcement of the truss improved the stiffness of the beam. There was a big difference between the shear bearing capacity of the oblique section of the bending area of printed truss-type reinforced support and the calculated bearing capacity of the oblique section of reinforced normal concrete where the reinforcement was bent.
The requirements of concrete printing technique make it impossible to install stirrups in beam members. Therefore, printed concrete beam members with different truss-type reinforcements were designed, and static loading tests were carried out. Normal section and oblique section failure tests of printed concrete beams with different truss numbers and sizes were carried out respectively. The failure characteristics, load-deflection curves under static load were studied. The test results showed that the flexural capacity of the printed truss-type reinforced concrete beam with appropriate reinforcement was similar to that of the concrete beam with single reinforcement, but the abdominal reinforcement of the truss improved the stiffness of the beam. There was a big difference between the shear bearing capacity of the oblique section of the bending area of printed truss-type reinforced support and the calculated bearing capacity of the oblique section of reinforced normal concrete where the reinforcement was bent.
2021, 51(6): 29-35.
doi: 10.13204/j.gyjzG21020323
Abstract:
3D printing technique is the frontier field of intelligent construction and new building industrialization. 3D printing technique has a broad application prospect in the construction field. As one of the main components bearing vertical load in the structure, the bearing capacity of the wall is crucial to the structural safety. In practical engineering, the vertical load of the wall is mostly eccentric. Therefore, the paper designed 10 printed concrete walls considering different cross-section forms, material strength and eccentricity, and conducted eccentric compression test on the walls. It was found that the arrangement of ribs in the printed wall could not only increase the stiffness of the wall section, but also enhance the connection between the two printed wall panels, improve the integrity of the wall, and thus improve the bearing capacity of the printed wall. The higher the cement strength grade, the greater the stiffness of concrete wall section, the smaller the vertical displacement under load. Avoiding the direct force of weak parts of the wall could effectively improve the bearing capacity of components. The increase of eccentricity could significantly reduce the bearing capacity of components and accelerate the failure of components.
3D printing technique is the frontier field of intelligent construction and new building industrialization. 3D printing technique has a broad application prospect in the construction field. As one of the main components bearing vertical load in the structure, the bearing capacity of the wall is crucial to the structural safety. In practical engineering, the vertical load of the wall is mostly eccentric. Therefore, the paper designed 10 printed concrete walls considering different cross-section forms, material strength and eccentricity, and conducted eccentric compression test on the walls. It was found that the arrangement of ribs in the printed wall could not only increase the stiffness of the wall section, but also enhance the connection between the two printed wall panels, improve the integrity of the wall, and thus improve the bearing capacity of the printed wall. The higher the cement strength grade, the greater the stiffness of concrete wall section, the smaller the vertical displacement under load. Avoiding the direct force of weak parts of the wall could effectively improve the bearing capacity of components. The increase of eccentricity could significantly reduce the bearing capacity of components and accelerate the failure of components.
2021, 51(6): 36-41,94.
doi: 10.13204/j.gyjzG20121501
Abstract:
Building industrialization and construction intelligence have become the current development trend. With the application of 3D printing technique in the construction field, the mechanical properties of 3D printed components need to be further studied. As one of the main components, mechanical properties of the wall are crucial to the performance of printed buildings under vertical load. Therefore, eight 3D printed concrete walls were designed with different section forms and material strengths, and the axial compression test was carried out. It was found that the two ends of printing walls were the main parts subjected to the external loads, and the failure began at both ends. The arrangement of ribs in the 3D printed wall could enhance the connection between the two wallboards, improve the integrity of the wall and enhance the bearing capacity of the 3D printed wall. The printed wall with higher cement strength had higher section stiffness, smaller vertical displacement and higher cracking load.
Building industrialization and construction intelligence have become the current development trend. With the application of 3D printing technique in the construction field, the mechanical properties of 3D printed components need to be further studied. As one of the main components, mechanical properties of the wall are crucial to the performance of printed buildings under vertical load. Therefore, eight 3D printed concrete walls were designed with different section forms and material strengths, and the axial compression test was carried out. It was found that the two ends of printing walls were the main parts subjected to the external loads, and the failure began at both ends. The arrangement of ribs in the 3D printed wall could enhance the connection between the two wallboards, improve the integrity of the wall and enhance the bearing capacity of the 3D printed wall. The printed wall with higher cement strength had higher section stiffness, smaller vertical displacement and higher cracking load.
2021, 51(6): 42-47,83.
doi: 10.13204/j.gyjzG21020403
Abstract:
As a research hotspot of in-situ utlization techniques for lunar resources, the in-situ forming technique of the lunar soil is the key to the manufacture of construction materials and the implementation of the lunar surface infrastructure. Based on the development status of in-situ lunar soil molding technique, spark plasma sintering (SPS) was used to achieve the modeling of simulated lunar soil. A quasi-static compression test was conducted on the molded specimen to study its compressive strength and elastic modulus. Based on the construction concept of the stone arch bridge structure and tenon structure, the lunar base structure system was designed, and the component connection method was proposed. Moreover, the applicability of arch structure to the construction of lunar soil molding structure was analyzed by finite element simulation. The results could provide a feasible path to achieve the in-situ construction by the lunar soil.
As a research hotspot of in-situ utlization techniques for lunar resources, the in-situ forming technique of the lunar soil is the key to the manufacture of construction materials and the implementation of the lunar surface infrastructure. Based on the development status of in-situ lunar soil molding technique, spark plasma sintering (SPS) was used to achieve the modeling of simulated lunar soil. A quasi-static compression test was conducted on the molded specimen to study its compressive strength and elastic modulus. Based on the construction concept of the stone arch bridge structure and tenon structure, the lunar base structure system was designed, and the component connection method was proposed. Moreover, the applicability of arch structure to the construction of lunar soil molding structure was analyzed by finite element simulation. The results could provide a feasible path to achieve the in-situ construction by the lunar soil.
2021, 51(6): 48-53,58.
doi: 10.13204/j.gyjzG20060103
Abstract:
The industrial zone planned and constructed under the historical limitation of "Heavy Industry Thought" has the characteristics of single function and isolated form. There was a large-scale decline in the process of urbanization and industrialization, which seriously affected the improvement of urban functions. The "production-living-ecological" theory under the background of ecological civilization was used for analyzing the promotion direction and synergy relationship of the three functional sections of production, life and ecology in the existing urban industrial area. According to the leading function of the industrial area promotion, the patterns of renovation were divided and supplemented by case analysis.This research would establish the foundation for the evaluation system of industrial area renovation, which could dynamically measure the effectiveness of function improvement.
The industrial zone planned and constructed under the historical limitation of "Heavy Industry Thought" has the characteristics of single function and isolated form. There was a large-scale decline in the process of urbanization and industrialization, which seriously affected the improvement of urban functions. The "production-living-ecological" theory under the background of ecological civilization was used for analyzing the promotion direction and synergy relationship of the three functional sections of production, life and ecology in the existing urban industrial area. According to the leading function of the industrial area promotion, the patterns of renovation were divided and supplemented by case analysis.This research would establish the foundation for the evaluation system of industrial area renovation, which could dynamically measure the effectiveness of function improvement.
2021, 51(6): 54-58.
doi: 10.13204/j.gyjzG20052908
Abstract:
The study briefly summarized the development process of modern silk reeling industry in China, and summaried the historical evolution of Yongtai Silk Factory. It expounded the heritage value of the silk factory site and main buildings. Based on the literature review and on-site survey, the environment and building overview of Yongtai Silk Factory before regeneration were analyzed, and the conservation and regeneration measures and methods of the factory environment and building were summarized. On this basis, the typical case in the silk factory conservation building-cocoon warehouse building was selected, its characteristics of basic dimensions and facade form, spatial form and structural system were interpreted, and the protective repair methods of the cocoon warehouse building were analyzed.
The study briefly summarized the development process of modern silk reeling industry in China, and summaried the historical evolution of Yongtai Silk Factory. It expounded the heritage value of the silk factory site and main buildings. Based on the literature review and on-site survey, the environment and building overview of Yongtai Silk Factory before regeneration were analyzed, and the conservation and regeneration measures and methods of the factory environment and building were summarized. On this basis, the typical case in the silk factory conservation building-cocoon warehouse building was selected, its characteristics of basic dimensions and facade form, spatial form and structural system were interpreted, and the protective repair methods of the cocoon warehouse building were analyzed.
2021, 51(6): 59-66,23.
doi: 10.13204/j.gyjzG20042108
Abstract:
In order to simplify the connection complexity of precast concrete members and reduce the construction difficulty, a precast concrete beam with H-shaped steel joints on both ends was proposed. The ends of the H-shaped steel of the prefabricated concrete beam was conneted with an end plate, which was connected with the beam ends by anchors, and the longitudinal reinforcement in the concrete beam section was connected with the end plate by perforated plug welding. Four test specimens were designed. The bearing capacity, deformation form and failure mode under concentrated load were experimentally studied, the method for calculating the deflection was proposed. The mechanical properties at the interface between the profile steel with different anchor types and the concrete were studied. The test results showed that when the section was the same, the deformation of the member connected only with webs was greater than that of the member connected with flanges and webs. When the mid-span deformation of the precast reinforced concrete beam of the H-shaped steel joint reached 1/50, the bearing capacity of the precast beam did not decrease, and no significant slip occurred at the junction of the steel and concrete. The flexural performance of the members could meet the requirements of Code for Design of Concrete Structures (GB 50010-2010).
In order to simplify the connection complexity of precast concrete members and reduce the construction difficulty, a precast concrete beam with H-shaped steel joints on both ends was proposed. The ends of the H-shaped steel of the prefabricated concrete beam was conneted with an end plate, which was connected with the beam ends by anchors, and the longitudinal reinforcement in the concrete beam section was connected with the end plate by perforated plug welding. Four test specimens were designed. The bearing capacity, deformation form and failure mode under concentrated load were experimentally studied, the method for calculating the deflection was proposed. The mechanical properties at the interface between the profile steel with different anchor types and the concrete were studied. The test results showed that when the section was the same, the deformation of the member connected only with webs was greater than that of the member connected with flanges and webs. When the mid-span deformation of the precast reinforced concrete beam of the H-shaped steel joint reached 1/50, the bearing capacity of the precast beam did not decrease, and no significant slip occurred at the junction of the steel and concrete. The flexural performance of the members could meet the requirements of Code for Design of Concrete Structures (GB 50010-2010).
2021, 51(6): 67-71.
doi: 10.13204/j.gyjzG20080704
Abstract:
The cambers of three prestressed concrete doubletees with concrete strength grade of C50 at the moment of prestressed tendons releasing and the age of 7 days were measured, meanwhile, the elastic modulus and compressive strength of the concrete specimens with the same material and curing condition were tested. The result showed that when steam curing for 30 hours or natural curing for 3 days, the compressive strength of the concrete could reach 80% of the designed concrete strength grade value, but the elastic modulus of the concrete only reached 38~55% of the standard value. The elastic modulus of the tested concrete with an age of 7 days could reach its standard value. Compared to natural-cured concrete, the compressive strength and elastic modulus of steam-cured concrete developed more rapidly. The time-effect model of concrete elastic modulus within the age of 7 days was obtained by regression analysis. Then a simulation analysis of the cambers at the age of 7 days was carried out based on the model of creep and shrinkage in MC 2010, and the calculated values were almost coincident with the measured values.
The cambers of three prestressed concrete doubletees with concrete strength grade of C50 at the moment of prestressed tendons releasing and the age of 7 days were measured, meanwhile, the elastic modulus and compressive strength of the concrete specimens with the same material and curing condition were tested. The result showed that when steam curing for 30 hours or natural curing for 3 days, the compressive strength of the concrete could reach 80% of the designed concrete strength grade value, but the elastic modulus of the concrete only reached 38~55% of the standard value. The elastic modulus of the tested concrete with an age of 7 days could reach its standard value. Compared to natural-cured concrete, the compressive strength and elastic modulus of steam-cured concrete developed more rapidly. The time-effect model of concrete elastic modulus within the age of 7 days was obtained by regression analysis. Then a simulation analysis of the cambers at the age of 7 days was carried out based on the model of creep and shrinkage in MC 2010, and the calculated values were almost coincident with the measured values.
2021, 51(6): 72-83.
doi: 10.13204/j.gyjzG20080511
Abstract:
The shear bond performance of new-to-old concrete interface with anchor bars is different from that of new-to-old concrete interface without anchor bars. The existing calculation equations for the shear strength of new-to-old concrete interface are mostly based on shear friction theory or fitting the test data. The concrete structure design codes for different countries also propose their shear strength calculation formulas. A total of 85 test data of new-to-old concrete interface with anchor bars were used to verify the applicability for the existing typical recipes. The results showed that these methods were either too conservative or lead to structural unsafe. According to the stress characteristics of the new-to-old concrete interface with anchor bars, the spring-friction block model for the shear transfer of new-to-old concrete interface with anchor bars was established. Meanwhile, the mechanism of shear transfer in the whole process of the interface was thoroughly analyzed by combining with the existing shear test load-slip curve. The results indicated that the shear bearing capacity of new-to-old concrete interface with anchor bars could be divided into four parts:the cohesive force of the new-to-old concrete interface, the mechanical occlusal force of groove, the pin bolt force of anchor bars, and the friction force. Based on the theoretical analysis of the calculation methods of four parts, the calculation formula for the shear strength of new-to-old concrete interface with anchor bars was proposed. The applicability of the proposed formula for calculating the shear bond strength of new-to-old concrete interface with anchor bars was verified by using 20 sets of test data. The average value and standard deviation of the ratio of experimental value to the calculated value were 1.182 and 0.305, respectively. Compared with the existing calculation methods, it was shown that the calculated results of the equation proposed in the paper were in the best agreement with the experimental results, and the discreteness was relatively low.
The shear bond performance of new-to-old concrete interface with anchor bars is different from that of new-to-old concrete interface without anchor bars. The existing calculation equations for the shear strength of new-to-old concrete interface are mostly based on shear friction theory or fitting the test data. The concrete structure design codes for different countries also propose their shear strength calculation formulas. A total of 85 test data of new-to-old concrete interface with anchor bars were used to verify the applicability for the existing typical recipes. The results showed that these methods were either too conservative or lead to structural unsafe. According to the stress characteristics of the new-to-old concrete interface with anchor bars, the spring-friction block model for the shear transfer of new-to-old concrete interface with anchor bars was established. Meanwhile, the mechanism of shear transfer in the whole process of the interface was thoroughly analyzed by combining with the existing shear test load-slip curve. The results indicated that the shear bearing capacity of new-to-old concrete interface with anchor bars could be divided into four parts:the cohesive force of the new-to-old concrete interface, the mechanical occlusal force of groove, the pin bolt force of anchor bars, and the friction force. Based on the theoretical analysis of the calculation methods of four parts, the calculation formula for the shear strength of new-to-old concrete interface with anchor bars was proposed. The applicability of the proposed formula for calculating the shear bond strength of new-to-old concrete interface with anchor bars was verified by using 20 sets of test data. The average value and standard deviation of the ratio of experimental value to the calculated value were 1.182 and 0.305, respectively. Compared with the existing calculation methods, it was shown that the calculated results of the equation proposed in the paper were in the best agreement with the experimental results, and the discreteness was relatively low.
2021, 51(6): 84-94.
doi: 10.13204/j.gyjzG20100401
Abstract:
In order to solve the problem of large amount of spot welding on existing wall-beam joints of steel tube bundle shear wall structure, a new type of anchoring prefabricated wall-beam joint for steel tube bundle shear wall structure was preposed. The failure modes, internal force distribution and the influence of plate thickness, anchorage length, and concrete strength grade on the seismic performance of the joint were studied by using the finite element software ABAQUS. The results showed that the hysteretic curve of the joint was full, showing good ductility and energy dissipation capacity. With the increase of the end plate thickness, the bearing capacity and seismic performance of the joint did not change significantly. With the increase of the anchorage length, the seismic performance of the joint was enhanced, and the bearing capacity increased significantly. However, when the anchorage length was 800 mm, the seismic performance and bearing capacity of the joint did not change significantly. With the improvement of concrete strength grade, the bearing capacity of the joint was less affected and gradually transformed from the local compressive bearing capacity of the concrete of the stud tail to the shear bearing capacity of the studs.
In order to solve the problem of large amount of spot welding on existing wall-beam joints of steel tube bundle shear wall structure, a new type of anchoring prefabricated wall-beam joint for steel tube bundle shear wall structure was preposed. The failure modes, internal force distribution and the influence of plate thickness, anchorage length, and concrete strength grade on the seismic performance of the joint were studied by using the finite element software ABAQUS. The results showed that the hysteretic curve of the joint was full, showing good ductility and energy dissipation capacity. With the increase of the end plate thickness, the bearing capacity and seismic performance of the joint did not change significantly. With the increase of the anchorage length, the seismic performance of the joint was enhanced, and the bearing capacity increased significantly. However, when the anchorage length was 800 mm, the seismic performance and bearing capacity of the joint did not change significantly. With the improvement of concrete strength grade, the bearing capacity of the joint was less affected and gradually transformed from the local compressive bearing capacity of the concrete of the stud tail to the shear bearing capacity of the studs.
2021, 51(6): 95-102.
doi: 10.13204/j.gyjzG20040903
Abstract:
In order to study the mechanical properties of the horizontal corrugated steel plate shear wall, and to compare it with that of flat steel plate shear wall, the shear wall specimens with flat steel plate and horizontal corrugated steel plate were designed and the quasi-static test was carried out. The results showed that the stiffness, bearing capacity and ductility of horizontal corrugated steel plate shear wall were greater than those of flat steel plate shear wall. The overall instability of shear wall was due to the fact that the out-of-plane stiffness of the frame column was insufficient, while the embedded steel plate did not play its full role, and the matching relationship between them was unreasonable. In order to study the reasonable stiffness matching relationship between the steel plate and the frame column, the ABAQUS finite element analysis software was used to establish 20 variable parameter models of horizontal corrugated steel plate shear wall for numerical analysis. By changing the aspect ratio of the embedded steel plate and the flange width of the frame column, the matching stiffness between them were changed. Comparing the simulation results with the test results, it was indicated that finite element analysis results were in good agreement; when the aspect ratio of embedded corrugated steel plate was 2:1 and the flange width of frame column was 150 mm, the matching effect was better.
In order to study the mechanical properties of the horizontal corrugated steel plate shear wall, and to compare it with that of flat steel plate shear wall, the shear wall specimens with flat steel plate and horizontal corrugated steel plate were designed and the quasi-static test was carried out. The results showed that the stiffness, bearing capacity and ductility of horizontal corrugated steel plate shear wall were greater than those of flat steel plate shear wall. The overall instability of shear wall was due to the fact that the out-of-plane stiffness of the frame column was insufficient, while the embedded steel plate did not play its full role, and the matching relationship between them was unreasonable. In order to study the reasonable stiffness matching relationship between the steel plate and the frame column, the ABAQUS finite element analysis software was used to establish 20 variable parameter models of horizontal corrugated steel plate shear wall for numerical analysis. By changing the aspect ratio of the embedded steel plate and the flange width of the frame column, the matching stiffness between them were changed. Comparing the simulation results with the test results, it was indicated that finite element analysis results were in good agreement; when the aspect ratio of embedded corrugated steel plate was 2:1 and the flange width of frame column was 150 mm, the matching effect was better.
2021, 51(6): 103-110,116.
doi: 10.13204/j.gyjzG20070211
Abstract:
In order to study the seismic performance of prefabricated shear wall with concrete filled steel tube frame under the rapid reciprocating load, three full-scaled single-layer single-span precast concrete-filled steel tube frame shear wall specimens were designed and fabricated. The reciprocating loading tests were carried out under the loading rates of 0.1, 5, 20 mm/s respectively, and the failure modes, hysteresis curve, skeleton curve, bearing capacity, ductility index, energy dissipation capacity and stiffness degradation were analyzed. The test results showed that all specimens were broken by concrete collapse at the bottom corner after the frame steel tube yielding, while the joints of steel bar and steel tube did not deform significantly, indicating that the sleeve grouting connection technology could meet the stress requirements of the prefabricated structures. The loading rate had limited impact on the seismic performance of prefabricated shear wall with concrete filled steel tube frame. When the loading rate was 200 times higher than the static loading rate, the bearing capacity of the shear wall increased by 6%, the ductility index decreased by 20%, and the equivalent viscous damping coefficient decreased by 13.1%.
In order to study the seismic performance of prefabricated shear wall with concrete filled steel tube frame under the rapid reciprocating load, three full-scaled single-layer single-span precast concrete-filled steel tube frame shear wall specimens were designed and fabricated. The reciprocating loading tests were carried out under the loading rates of 0.1, 5, 20 mm/s respectively, and the failure modes, hysteresis curve, skeleton curve, bearing capacity, ductility index, energy dissipation capacity and stiffness degradation were analyzed. The test results showed that all specimens were broken by concrete collapse at the bottom corner after the frame steel tube yielding, while the joints of steel bar and steel tube did not deform significantly, indicating that the sleeve grouting connection technology could meet the stress requirements of the prefabricated structures. The loading rate had limited impact on the seismic performance of prefabricated shear wall with concrete filled steel tube frame. When the loading rate was 200 times higher than the static loading rate, the bearing capacity of the shear wall increased by 6%, the ductility index decreased by 20%, and the equivalent viscous damping coefficient decreased by 13.1%.
2021, 51(6): 111-116.
doi: 10.13204/j.gyjzG20072604
Abstract:
To investigate the mechanical properties of the perforated plate shear connections for bamboo-concrete composite structures, the push-out tests on the perforated plate connectors were conducted. The results showed that the typical failure modes of perforated plate shear connections of bamboo-concrete composite structures were the yield of the perforated plate, partial shearing crushing of the concrete, and the slipping of the perforated plate in the bamboo section. The yield of the perforated plate occurred mostly at the perforated plate shear connections of bamboo-concrete. The load-slip curves of perforated plate shear connections of bamboo-concrete structures maintained a high residual load value after reaching the peak load, and the load dropped slowly. The failure modes were ductile no matter whether setting perforated steel bar of not, and its interface slipped evenly along the height of the interface. The bearing capacity of perforated plate shear connections of bamboo-concrete structures were determined by three factors, which were the bearing capacity of the interface between the perforated plate and bamboo, the bearing capacity of the interface between the perforated plate and concrete, and the shear resistance of the weakest section of the perforated plate at the interface. Based on the test results, the analysis method of the bearing capacity was proposed for the perforated plate shear connections of bamboo-concrete structures.
To investigate the mechanical properties of the perforated plate shear connections for bamboo-concrete composite structures, the push-out tests on the perforated plate connectors were conducted. The results showed that the typical failure modes of perforated plate shear connections of bamboo-concrete composite structures were the yield of the perforated plate, partial shearing crushing of the concrete, and the slipping of the perforated plate in the bamboo section. The yield of the perforated plate occurred mostly at the perforated plate shear connections of bamboo-concrete. The load-slip curves of perforated plate shear connections of bamboo-concrete structures maintained a high residual load value after reaching the peak load, and the load dropped slowly. The failure modes were ductile no matter whether setting perforated steel bar of not, and its interface slipped evenly along the height of the interface. The bearing capacity of perforated plate shear connections of bamboo-concrete structures were determined by three factors, which were the bearing capacity of the interface between the perforated plate and bamboo, the bearing capacity of the interface between the perforated plate and concrete, and the shear resistance of the weakest section of the perforated plate at the interface. Based on the test results, the analysis method of the bearing capacity was proposed for the perforated plate shear connections of bamboo-concrete structures.
2021, 51(6): 117-122.
doi: 10.13204/j.gyjzG20041902
Abstract:
Based on the axial compression test of 9 reactive powder concrete (RPC) short columns confined by square steel tubes (the concrete mixed with steel fibers and built-in spiral stirrups), the effects of steel fiber content and spiral stirrup spacing on the failure mode, bearing capacity and ductility of columns were studied. The test results showed that the deformation capacity of the specimen could be greatly improved by adding steel fibers and embedding spiral stirrups, and the increase range of ultimate bearing capacity could be up to 10%~25%. Based on the experiment, the ABAQUS finite element analysis model was established to further analyze the influence of length-thickness ratio and stirrup spacing on the bearing capacity and ductility of columns,the results of theoretical analysis could provide theoretical support for engineering practice.
Based on the axial compression test of 9 reactive powder concrete (RPC) short columns confined by square steel tubes (the concrete mixed with steel fibers and built-in spiral stirrups), the effects of steel fiber content and spiral stirrup spacing on the failure mode, bearing capacity and ductility of columns were studied. The test results showed that the deformation capacity of the specimen could be greatly improved by adding steel fibers and embedding spiral stirrups, and the increase range of ultimate bearing capacity could be up to 10%~25%. Based on the experiment, the ABAQUS finite element analysis model was established to further analyze the influence of length-thickness ratio and stirrup spacing on the bearing capacity and ductility of columns,the results of theoretical analysis could provide theoretical support for engineering practice.
2021, 51(6): 123-132,164.
doi: 10.13204/j.gyjzG20032801
Abstract:
In order to study the influence of key parameters such as steel strength, concrete strength, steel flange thickness, steel web thickness, column height, stud spacing, and stirrup spacing on the bearing capacity and failure mode of L-shaped steel special-shaped columns, a total of 5 sets of comparative members were designed for the finite element analysis under axial compression. The failure mode, load-displacement curve, stress distribution of profiled steel and concrete, etc. were obtained to analyze the performance of the special-shaped column under axial compression. The results showed that the structure of the special-shaped column with L-shaped steel was reasonable. With the increase of steel strength, steel ratio and concrete strength, the bearing capacity gradually increased. When the column height changed from 3 meters to 5 meters, it had little effect on the ultimate bearing capacity of special-shaped columns. The effects of stud spacing and stirrup spacing on the bearing capacity could be ignored.
In order to study the influence of key parameters such as steel strength, concrete strength, steel flange thickness, steel web thickness, column height, stud spacing, and stirrup spacing on the bearing capacity and failure mode of L-shaped steel special-shaped columns, a total of 5 sets of comparative members were designed for the finite element analysis under axial compression. The failure mode, load-displacement curve, stress distribution of profiled steel and concrete, etc. were obtained to analyze the performance of the special-shaped column under axial compression. The results showed that the structure of the special-shaped column with L-shaped steel was reasonable. With the increase of steel strength, steel ratio and concrete strength, the bearing capacity gradually increased. When the column height changed from 3 meters to 5 meters, it had little effect on the ultimate bearing capacity of special-shaped columns. The effects of stud spacing and stirrup spacing on the bearing capacity could be ignored.
2021, 51(6): 133-137.
doi: 10.13204/j.gyjzG20081014
Abstract:
The bearing capacity of compression bars is mostly controlled by stability rather than strength. It is the main goal to improve the stable bearing capacity of the compression members when they are reinforced. Outer sleeve reinforcement is a kind of method with definite load condition and convenient construction, and has been widely used. Rigid prestressed strut reinforcement is also a method to reduce the compressive stress of compression bar. In the paper, the lateral deformation between the steel sleeve and the reinforced compression bar was kept in harmony. The critical value of the stability bearing capacity of the compression bar was obtained by using the condition that the release of compressive strain energy was equal to the absorption of bending strain energy in the case of instability. The formula was also suitable for the design and calculation of the reinforcement with rigid prestressed strut. An example of large deformation geometric nonlinear instability was calculated by ANSYS and the critical values of stability load under four different loading conditions were obtained. The difference from the theoretical analysis value was less than 1%, which verified the correctness of the theoretical value in the paper, and also verified that the outer sleeve and compression bar could meet the requirements of consistent deformation through several node limits.
The bearing capacity of compression bars is mostly controlled by stability rather than strength. It is the main goal to improve the stable bearing capacity of the compression members when they are reinforced. Outer sleeve reinforcement is a kind of method with definite load condition and convenient construction, and has been widely used. Rigid prestressed strut reinforcement is also a method to reduce the compressive stress of compression bar. In the paper, the lateral deformation between the steel sleeve and the reinforced compression bar was kept in harmony. The critical value of the stability bearing capacity of the compression bar was obtained by using the condition that the release of compressive strain energy was equal to the absorption of bending strain energy in the case of instability. The formula was also suitable for the design and calculation of the reinforcement with rigid prestressed strut. An example of large deformation geometric nonlinear instability was calculated by ANSYS and the critical values of stability load under four different loading conditions were obtained. The difference from the theoretical analysis value was less than 1%, which verified the correctness of the theoretical value in the paper, and also verified that the outer sleeve and compression bar could meet the requirements of consistent deformation through several node limits.
2021, 51(6): 138-142.
doi: 10.13204/j.gyjzG20071310
Abstract:
To understand the effect of particle size gradations on mechanical properties of loose granular materials, direct shear tests of specimens with different coarse particle fractions were conducted. The stress-strain curves and shear strength were obtained in the conditions of different normal stress. The results were fitted according to the model of the BoxLucas1 stress transfer. The changes of coarse sand fractions were introduced into the model as a parameter, and a modified model suitable for the strength of loose granular materials was developed. The model could take into account influences of coarse sand fractions and normal stress, and the final calculation results were in good agreements with the experimental results, which could be used to calculate shear strength of loose granular materials.
To understand the effect of particle size gradations on mechanical properties of loose granular materials, direct shear tests of specimens with different coarse particle fractions were conducted. The stress-strain curves and shear strength were obtained in the conditions of different normal stress. The results were fitted according to the model of the BoxLucas1 stress transfer. The changes of coarse sand fractions were introduced into the model as a parameter, and a modified model suitable for the strength of loose granular materials was developed. The model could take into account influences of coarse sand fractions and normal stress, and the final calculation results were in good agreements with the experimental results, which could be used to calculate shear strength of loose granular materials.
2021, 51(6): 143-149,122.
doi: 10.13204/j.gyjzG20071704
Abstract:
In order to study the mechanical and structural characteristics of alluvial-diluvial subgrade fillers with different gradations, the alluvial-diluvial deposits in Luonan, Shaanxi were researched. Based on the N-method in the theory of the maximum density, five different subgrade filler gradations were designed. A large-scale direct shear test was designed to analyze the effects of gradations on the shear strength. A HD digital camera was used to collect the shear plane images of specimens different with gradations. The mesostructure characteristics of the shear plane for specimens were analyzed from the mesoscale by the software of lmage-Pro Plus. The effects of gradations on mechanical properties of fillers were analyzed from the perspective of macro and meso. The results showed that the effect of pore forms in the shear planes on shear characteristics were significant, when the pore form was oblate mainly, the shear strength of fillers was the highest and the form coefficient was 0.55; then it was equiaxed and finally was bar-type. The pore forms of fillers developed from the oblate to the equiaxed, the percentage of the pore areas, fragmentation ratios and fractal dimension values of fillers decreased first and then increased with the increase of n, and finally reached the extreme value when n was 0.55.
In order to study the mechanical and structural characteristics of alluvial-diluvial subgrade fillers with different gradations, the alluvial-diluvial deposits in Luonan, Shaanxi were researched. Based on the N-method in the theory of the maximum density, five different subgrade filler gradations were designed. A large-scale direct shear test was designed to analyze the effects of gradations on the shear strength. A HD digital camera was used to collect the shear plane images of specimens different with gradations. The mesostructure characteristics of the shear plane for specimens were analyzed from the mesoscale by the software of lmage-Pro Plus. The effects of gradations on mechanical properties of fillers were analyzed from the perspective of macro and meso. The results showed that the effect of pore forms in the shear planes on shear characteristics were significant, when the pore form was oblate mainly, the shear strength of fillers was the highest and the form coefficient was 0.55; then it was equiaxed and finally was bar-type. The pore forms of fillers developed from the oblate to the equiaxed, the percentage of the pore areas, fragmentation ratios and fractal dimension values of fillers decreased first and then increased with the increase of n, and finally reached the extreme value when n was 0.55.
2021, 51(6): 150-155.
doi: 10.13204/j.gyjzG20112804
Abstract:
In order to explore the applicability of helical anchor foundation and promote its application in gravel strata, the axial pull-out tests for complete-model and half-model helical anchors in remolded gravel ground were conducted in the laboratory. Based on the test results, the distribution and shape of longitudinal cracks in the gravel, the bearing characteristics of pull-out resistance for helical anchors in gravel and the effects of anchor plates on bearing capacity were analyzed. The bearing mechanisms of pull-out resistance for helical anchors were studied. The results showed that the general shear failure and bearing capacity weakening often occured to anchor plates shallowly emkedded in gravel strata, local shear failure usually occured in the upper soil stratum above anchor plates deeply embeded in gravel strata, which resulted in the deformation to increase continuously. Gravel strata above anchor plates at the initial stage of loading, and the relations between loads and displacement were approximately linear; with the increase of loading, soils above the anchor plates were compressed and sheared, which led to excessive deformation and bearing failure. The more the anchor plates, the deeper the embedment, the larger the bearing capacity of pull-out resistance and the smaller the deformation of the helical anchor. Increasing embedment could play a full role in bearing capacity of pull-out resistance at the stage of small displacement. Therefore, the helical anchors in gravel were a kind of deep foundations, and the interaction between anchor plates and soil was the main factor influcencing bearing capacity.
In order to explore the applicability of helical anchor foundation and promote its application in gravel strata, the axial pull-out tests for complete-model and half-model helical anchors in remolded gravel ground were conducted in the laboratory. Based on the test results, the distribution and shape of longitudinal cracks in the gravel, the bearing characteristics of pull-out resistance for helical anchors in gravel and the effects of anchor plates on bearing capacity were analyzed. The bearing mechanisms of pull-out resistance for helical anchors were studied. The results showed that the general shear failure and bearing capacity weakening often occured to anchor plates shallowly emkedded in gravel strata, local shear failure usually occured in the upper soil stratum above anchor plates deeply embeded in gravel strata, which resulted in the deformation to increase continuously. Gravel strata above anchor plates at the initial stage of loading, and the relations between loads and displacement were approximately linear; with the increase of loading, soils above the anchor plates were compressed and sheared, which led to excessive deformation and bearing failure. The more the anchor plates, the deeper the embedment, the larger the bearing capacity of pull-out resistance and the smaller the deformation of the helical anchor. Increasing embedment could play a full role in bearing capacity of pull-out resistance at the stage of small displacement. Therefore, the helical anchors in gravel were a kind of deep foundations, and the interaction between anchor plates and soil was the main factor influcencing bearing capacity.
2021, 51(6): 156-164.
doi: 10.13204/j.gyjzG19083102
Abstract:
In order to provide a reference to seismic design of multi-stage slopes reinforced with anti-slide piles, a sensitivity study on the stability factors of 3D slopes reinforced with anti-slide piles under earthquake action was conducted. Based on the upper bound theorem and combined with pseudo-static method and strength reduction method, the safety factors of slopes were calculated. The sensitivity sequence from strong to weak influencing safety factors of slopes under seismic forces were cohesion, internal friction angles, slope angles, horizontal seismic force coefficients, pile positions, structural parameters of piles, relative ratios of wideth to height for slopes and berm width. Therefore, in the actual construction, the influence of slope angles, seismic forces and anti-slide piles shoud be fully taken into account, and the relative ratios of width to height for slopes and berm width should be rationally laid out according to actual conditions.
In order to provide a reference to seismic design of multi-stage slopes reinforced with anti-slide piles, a sensitivity study on the stability factors of 3D slopes reinforced with anti-slide piles under earthquake action was conducted. Based on the upper bound theorem and combined with pseudo-static method and strength reduction method, the safety factors of slopes were calculated. The sensitivity sequence from strong to weak influencing safety factors of slopes under seismic forces were cohesion, internal friction angles, slope angles, horizontal seismic force coefficients, pile positions, structural parameters of piles, relative ratios of wideth to height for slopes and berm width. Therefore, in the actual construction, the influence of slope angles, seismic forces and anti-slide piles shoud be fully taken into account, and the relative ratios of width to height for slopes and berm width should be rationally laid out according to actual conditions.
2021, 51(6): 165-169.
doi: 10.13204/j.gyjzG20062808
Abstract:
To study the durability and service life of fiber reinforced concrete in severe cold areas, an accelerated life test of fiber reinforced concrete under temperature changes was designed. The mass loss and relative dynamic modulus of the specimen were periodically measured, and its durability based on the measured data was evaluated and analyzed. At the same time, based on the univariate Wiener degradation process, modeling and accelerated life prediction were conducted. The results showed that as the number of freeze-thaw cycles increased, the specimen was gradually damaged and deteriorated, and the relative mass and relative dynamic elastic modulus of the specimen could effectively reflect the damage process, and the relative dynamic elastic modulus as the evaluation parameter could more accurately and truly reflect the damage and deterioration of the specimen. Reliability modeling was carried out through the univariate Wiener degradation process, and the relative dynamic elastic modulus of specimens was used as the degradation index. After calculation using this model, the probability density function and reliability function of the specimen could be obtained. Data fitting was performed on the results, and it was determined that the longest service life of the fiber reinfoned concrete specimen could reach about 3 500 h under the test conditions.
To study the durability and service life of fiber reinforced concrete in severe cold areas, an accelerated life test of fiber reinforced concrete under temperature changes was designed. The mass loss and relative dynamic modulus of the specimen were periodically measured, and its durability based on the measured data was evaluated and analyzed. At the same time, based on the univariate Wiener degradation process, modeling and accelerated life prediction were conducted. The results showed that as the number of freeze-thaw cycles increased, the specimen was gradually damaged and deteriorated, and the relative mass and relative dynamic elastic modulus of the specimen could effectively reflect the damage process, and the relative dynamic elastic modulus as the evaluation parameter could more accurately and truly reflect the damage and deterioration of the specimen. Reliability modeling was carried out through the univariate Wiener degradation process, and the relative dynamic elastic modulus of specimens was used as the degradation index. After calculation using this model, the probability density function and reliability function of the specimen could be obtained. Data fitting was performed on the results, and it was determined that the longest service life of the fiber reinfoned concrete specimen could reach about 3 500 h under the test conditions.
2021, 51(6): 170-175,155.
doi: 10.13204/j.gyjzG20041411
Abstract:
The reinforced concrete (RC) structures in cold coastal regions or deicing salt condition were under the synthetic effects of loading cracks and corrosion led by freeze-thaw and chloride ingress. The steel was vulnerable to chloridion ingress because the crack provided convenient channel, which shortened the service life of RC structures. The chloridion profile of RC specimens with sustained loading cracks and artificial cracks after being subjected to the combined action of freeze-thaw and chloridion immersion was experimentally studied. This study focused on the difference between the effects of sustained load cracks and artificial cracks on chloridion diffusion and service life. In this study, the widths of sustained loading cracks were 0,0.06,0.07,0.11,0.13 mm and the widths of artificial cracks were 0,0.07,0.13,0.19 mm. The experimental results showed that, when the crack width was less than 0.07 mm, the differences between the effects of sustained loading cracks and artificial cracks on chloridion diffusion were slight. When the crack width was more than 0.07 mm, the effects of sustained loading cracks on chloridion diffusion was larger than that of artificial cracks. In addition, the differences became bigger as the crack width increased. The chloride diffusion in one-dimensional and two-dimensional state were respectively considered. The service life was predicted by Monte-Carlo Method. It was obvious that the service life of RC structures with sustained loading cracks was shorter than that with artificial cracks.
The reinforced concrete (RC) structures in cold coastal regions or deicing salt condition were under the synthetic effects of loading cracks and corrosion led by freeze-thaw and chloride ingress. The steel was vulnerable to chloridion ingress because the crack provided convenient channel, which shortened the service life of RC structures. The chloridion profile of RC specimens with sustained loading cracks and artificial cracks after being subjected to the combined action of freeze-thaw and chloridion immersion was experimentally studied. This study focused on the difference between the effects of sustained load cracks and artificial cracks on chloridion diffusion and service life. In this study, the widths of sustained loading cracks were 0,0.06,0.07,0.11,0.13 mm and the widths of artificial cracks were 0,0.07,0.13,0.19 mm. The experimental results showed that, when the crack width was less than 0.07 mm, the differences between the effects of sustained loading cracks and artificial cracks on chloridion diffusion were slight. When the crack width was more than 0.07 mm, the effects of sustained loading cracks on chloridion diffusion was larger than that of artificial cracks. In addition, the differences became bigger as the crack width increased. The chloride diffusion in one-dimensional and two-dimensional state were respectively considered. The service life was predicted by Monte-Carlo Method. It was obvious that the service life of RC structures with sustained loading cracks was shorter than that with artificial cracks.
2021, 51(6): 176-180,8.
doi: 10.13204/j.gyjzG20072207
Abstract:
The rapid chloridion diffusion coefficient method was used to study the effect of different curing regimes and the use of mineral admixture on chloridion resistance of white concrete. The results showed that the pure white cement concrete had the lowest resistance to chloridion penetration among the three groups of curing regimes. The use of mineral admixtures could greatly reduce the rapid chloridion diffusion coefficient (DRCM) of the white cement concrete; the DRCM of the concrete under standard curing was the lowest, the value of matching curing was the second high and that of steam curing was the highest; the second exothermic peak of white cement hydration in the early stage appeared earliest, and its peak was the highest data. However, the cumulative heat release of pure white cement was lower than that of ordinary cement. In addition, the pure white cement concrete had the highest adiabatic temperature rise (ATR) and the highest temperature, the concrete with cement-mineral powder system possessed the second-high ATR and the concrete with cement-mineral powder-limestone powder had the lowest value. Through the pore structure analysis, it could be seen that although steam curing might stimulate the hydration process of the concrete and reduce the porosity, it would promote the pore structure to develop toward the rough pore and would increase the average pore diameter.
The rapid chloridion diffusion coefficient method was used to study the effect of different curing regimes and the use of mineral admixture on chloridion resistance of white concrete. The results showed that the pure white cement concrete had the lowest resistance to chloridion penetration among the three groups of curing regimes. The use of mineral admixtures could greatly reduce the rapid chloridion diffusion coefficient (DRCM) of the white cement concrete; the DRCM of the concrete under standard curing was the lowest, the value of matching curing was the second high and that of steam curing was the highest; the second exothermic peak of white cement hydration in the early stage appeared earliest, and its peak was the highest data. However, the cumulative heat release of pure white cement was lower than that of ordinary cement. In addition, the pure white cement concrete had the highest adiabatic temperature rise (ATR) and the highest temperature, the concrete with cement-mineral powder system possessed the second-high ATR and the concrete with cement-mineral powder-limestone powder had the lowest value. Through the pore structure analysis, it could be seen that although steam curing might stimulate the hydration process of the concrete and reduce the porosity, it would promote the pore structure to develop toward the rough pore and would increase the average pore diameter.
2021, 51(6): 181-185.
doi: 10.13204/j.gyjzG20082507
Abstract:
Aiming at a high-strength seawater coral aggregate concrete (SCAC),the paper thoroughly examined the effects of several key mix parameters,such as the total cementitious material dosage,the maximum size of coral stone,the amount of composite mineral admixture,the water content of concrete cube,and the sand ratio.Through compressive test on cube samples at 3 d,7 d and 28 d,the compressive strength development of SCAC with different mix proportions were investigated.The results showed that under the condition of 70% usage rate of local materials,the effects of cementing material dosage and water content on SCAC strength were similar to that of normal concrete. The combination of increasing cementing material dosage and reducing water content could improve the 28 d compressive strength up to 58 MPa.The appropriate amount of composite mineral admixture could effectively slow down the early strength development of SCAC,and helped for the long-term strength growth.Decreasing the maximum particle size of aggregate led to increased compressive strength of SCAC,but the extent of this effect was gradually decreased with age.The increase in strength owing to increase of sand ratio was found significant in the mixture with low water-binder ratio,but the sand ratio should be controlled within a reasonable range.
Aiming at a high-strength seawater coral aggregate concrete (SCAC),the paper thoroughly examined the effects of several key mix parameters,such as the total cementitious material dosage,the maximum size of coral stone,the amount of composite mineral admixture,the water content of concrete cube,and the sand ratio.Through compressive test on cube samples at 3 d,7 d and 28 d,the compressive strength development of SCAC with different mix proportions were investigated.The results showed that under the condition of 70% usage rate of local materials,the effects of cementing material dosage and water content on SCAC strength were similar to that of normal concrete. The combination of increasing cementing material dosage and reducing water content could improve the 28 d compressive strength up to 58 MPa.The appropriate amount of composite mineral admixture could effectively slow down the early strength development of SCAC,and helped for the long-term strength growth.Decreasing the maximum particle size of aggregate led to increased compressive strength of SCAC,but the extent of this effect was gradually decreased with age.The increase in strength owing to increase of sand ratio was found significant in the mixture with low water-binder ratio,but the sand ratio should be controlled within a reasonable range.
2021, 51(6): 186-197.
doi: 10.13204/j.gyjzG20062905
Abstract:
Fiber-reinforced polymer (FRP), a new composite material with advantages such as light weight, high strength, corrosion resistance, has been widely used in strengthening of existing structures but much less in new structures. As a non-metallic material, FRP is featured by its linear brittle nature and the lack of energy dissipation, as a result, new structure incorporating FRP cannot be easily connected to other structural members by welding or other measures (riveting, bolting) like in steel structures, which limits the application of FRP in new structures to a certain extent. It is well-known that the performance of beam-to-column joints is very critical to ensure the overall structural performance of a structural system, which is also the technical bottleneck to be solved in the application of FRP in new structures. To this end, this paper provided a state-of-the-art review of beam-to-column joints of FRP new building structures in recent years, in order to identify research needs for the technical difficulties. The FRP new building structures discussed herein included the beam-to-column joints of all-FRP structures, FRP bars reinforced concrete structures and composite structures based on FRP-confined concrete. The shortcomings of the existing research on beam-to-column joints of FRP composite structures were analyzed, and prospects were put forward, which could identify the research needs and provide possible solutions for the application of new structures incorporating FRP in the future.
Fiber-reinforced polymer (FRP), a new composite material with advantages such as light weight, high strength, corrosion resistance, has been widely used in strengthening of existing structures but much less in new structures. As a non-metallic material, FRP is featured by its linear brittle nature and the lack of energy dissipation, as a result, new structure incorporating FRP cannot be easily connected to other structural members by welding or other measures (riveting, bolting) like in steel structures, which limits the application of FRP in new structures to a certain extent. It is well-known that the performance of beam-to-column joints is very critical to ensure the overall structural performance of a structural system, which is also the technical bottleneck to be solved in the application of FRP in new structures. To this end, this paper provided a state-of-the-art review of beam-to-column joints of FRP new building structures in recent years, in order to identify research needs for the technical difficulties. The FRP new building structures discussed herein included the beam-to-column joints of all-FRP structures, FRP bars reinforced concrete structures and composite structures based on FRP-confined concrete. The shortcomings of the existing research on beam-to-column joints of FRP composite structures were analyzed, and prospects were put forward, which could identify the research needs and provide possible solutions for the application of new structures incorporating FRP in the future.
2021, 51(6): 198-205,197.
doi: 10.13204/j.gyjzG20111816
Abstract:
In this paper, flexural bearing capacity of carbon fiber reinforced aluminum laminate (CARALL) beams, with a double-channel cross section and a 3/2 laminated configuration, were experimentally and numerically studied. Two types of specimens using different carbon fiber layup configurations ([0°/90°/0°] and[45°/0°/-45°]) were fabricated by the pressure molding thermal curing forming process. The double-channel CARALL beams were then subjected to static four-point bending tests to determine their ultimate behaviors in terms of ultimate bearing capacity and failure modes. In view of the shortcomings of two-dimensional Hashin failure criterion, the user-defined FORTRAN subroutine VUMAT suitable for ABAQUS/Explicit solver and analysis algorithm was established to obtain a progressive damage prediction of CFRP layer based on three-dimensional Hashin failure criterion. The bearing capacity and failure modes of the proposed CARALL beams with double-channel cross-section were then numerally analyzed. Meanwhile, a theoretical method for predicting the safe bearing capacity of CARALL beams was proposed based on the classic laminate theory. Comparisons of the experimental, numerical, and theoretical results demonstrated good agreement, indicating that the proposed theoretical method was feasible for predicting the safe bearing capacity of CARALL beams with double-channel cross section and could be applied to the design of laminate beam components with special-shaped section.
In this paper, flexural bearing capacity of carbon fiber reinforced aluminum laminate (CARALL) beams, with a double-channel cross section and a 3/2 laminated configuration, were experimentally and numerically studied. Two types of specimens using different carbon fiber layup configurations ([0°/90°/0°] and[45°/0°/-45°]) were fabricated by the pressure molding thermal curing forming process. The double-channel CARALL beams were then subjected to static four-point bending tests to determine their ultimate behaviors in terms of ultimate bearing capacity and failure modes. In view of the shortcomings of two-dimensional Hashin failure criterion, the user-defined FORTRAN subroutine VUMAT suitable for ABAQUS/Explicit solver and analysis algorithm was established to obtain a progressive damage prediction of CFRP layer based on three-dimensional Hashin failure criterion. The bearing capacity and failure modes of the proposed CARALL beams with double-channel cross-section were then numerally analyzed. Meanwhile, a theoretical method for predicting the safe bearing capacity of CARALL beams was proposed based on the classic laminate theory. Comparisons of the experimental, numerical, and theoretical results demonstrated good agreement, indicating that the proposed theoretical method was feasible for predicting the safe bearing capacity of CARALL beams with double-channel cross section and could be applied to the design of laminate beam components with special-shaped section.
2021, 51(6): 206-211,216.
doi: 10.13204/j.gyjzG20102001
Abstract:
Taking the CFRP reinforced concrete circular columns as the research object, a reliability evaluation on the axial compressed members which were designed according to the Technical Code for Infrastructure Application of FRP Composites GB 50608-2010, was conducted by JC method. It was found that the diameter of the columns and concrete strength had little effect on the average reliability index. The steel strength, steel reinforcement ratio, and FRP strength all had a little effect on the average reliability index. By contrast, the FRP reinforcement ratio had an obvious effect on the reliability index, and the average reliability index indicated an increase tendency with a larger FRP reinforcement ratio. Similarly, the average reliability index increased with the increase of load effect ratio, and then became flat when the load effect ratio was larger than 2.0. The average reliability index of CFRP reinforced circular columns under axial loads were 4.40 and 4.53, corresponding to the two typical live loads of residential building and office building respectively. These reliability indexes were about 0.8 lower than the axial compressed columns designed by the Code for Design of Concrete Structures GB 50010-2010. In order to obtain the same reliability level as the axial compressed members in the current code of GB 50010-2010, some suggestions were put forward to revise the original formula provided by the code of GB 50608-2010.
Taking the CFRP reinforced concrete circular columns as the research object, a reliability evaluation on the axial compressed members which were designed according to the Technical Code for Infrastructure Application of FRP Composites GB 50608-2010, was conducted by JC method. It was found that the diameter of the columns and concrete strength had little effect on the average reliability index. The steel strength, steel reinforcement ratio, and FRP strength all had a little effect on the average reliability index. By contrast, the FRP reinforcement ratio had an obvious effect on the reliability index, and the average reliability index indicated an increase tendency with a larger FRP reinforcement ratio. Similarly, the average reliability index increased with the increase of load effect ratio, and then became flat when the load effect ratio was larger than 2.0. The average reliability index of CFRP reinforced circular columns under axial loads were 4.40 and 4.53, corresponding to the two typical live loads of residential building and office building respectively. These reliability indexes were about 0.8 lower than the axial compressed columns designed by the Code for Design of Concrete Structures GB 50010-2010. In order to obtain the same reliability level as the axial compressed members in the current code of GB 50010-2010, some suggestions were put forward to revise the original formula provided by the code of GB 50608-2010.
2021, 51(6): 212-216.
doi: 10.13204/j.gyjzG20031015
Abstract:
Hubei is the birthplace of Chu culture and politics. Jingchu culture, as one of the representative cultures in the south, how to inherit and develop Jingchu culture is the main purpose of this study. Architecture is regarded as the carrier of human civilization. Through the theoretical research of Jingchu architecture, combined with modern building technology materials and green building, the study aims to build modern industrial architecture with traditional regional cultural characteristics, realize the unity of modern architecture and traditional culture, and provide corresponding reference for inheriting Jingchu architecture.
Hubei is the birthplace of Chu culture and politics. Jingchu culture, as one of the representative cultures in the south, how to inherit and develop Jingchu culture is the main purpose of this study. Architecture is regarded as the carrier of human civilization. Through the theoretical research of Jingchu architecture, combined with modern building technology materials and green building, the study aims to build modern industrial architecture with traditional regional cultural characteristics, realize the unity of modern architecture and traditional culture, and provide corresponding reference for inheriting Jingchu architecture.
