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2020 Vol. 50, No. 8
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2020, 50(8): 1-4.
doi: 10.13204/j.gyjzG20081013
Abstract:
The paper introduced the purpose and significance of the national key research and development plan "Key Techniques and Demonstration for Manufacturing Industrial Building Parts and Components". It focused on the key techniques and product research and development results in the fields of modular coordination, product system, standardization and serialization of production and manufacturing techniques, flexible manufacturing, and intelligent manufacturing of steel structures. Its related contents basically cover the technical difficulties and industry focuses of industrial building manufacturing at present.
The paper introduced the purpose and significance of the national key research and development plan "Key Techniques and Demonstration for Manufacturing Industrial Building Parts and Components". It focused on the key techniques and product research and development results in the fields of modular coordination, product system, standardization and serialization of production and manufacturing techniques, flexible manufacturing, and intelligent manufacturing of steel structures. Its related contents basically cover the technical difficulties and industry focuses of industrial building manufacturing at present.
2020, 50(8): 5-9.
doi: 10.13204/j.gyjzG20052506
Abstract:
In order to promote the establishment of the tolerance theory system for prefabricated buildings suitable in China, the paper focused on the analysis of the relevant contents of the tolerance standard system provided by the International Organization for Standardization. Based on the theory of probability and statistics, the variability of the dimensions of assembly components was proposed as the basic assumption of tolerance or deviation analysis, the geometric significance and the spatial relationship of the tolerance calculation formula of buildings were analyzed, the method for determining the target dimensios of assembly components was propesed, and the calculation process and method of deviation distribution were given. From the perspective of perfecting the tolerance system of industrialized buildings in China, the paper discussed the validity and application value of current international standard tolerance. The suggestions for improving the tolerance system of industrialized buildings in China were also put forward in the paper.
In order to promote the establishment of the tolerance theory system for prefabricated buildings suitable in China, the paper focused on the analysis of the relevant contents of the tolerance standard system provided by the International Organization for Standardization. Based on the theory of probability and statistics, the variability of the dimensions of assembly components was proposed as the basic assumption of tolerance or deviation analysis, the geometric significance and the spatial relationship of the tolerance calculation formula of buildings were analyzed, the method for determining the target dimensios of assembly components was propesed, and the calculation process and method of deviation distribution were given. From the perspective of perfecting the tolerance system of industrialized buildings in China, the paper discussed the validity and application value of current international standard tolerance. The suggestions for improving the tolerance system of industrialized buildings in China were also put forward in the paper.
RESEARCH ON THE INFORMATION PLATFORM FOR MANUFACTURE OF INDUSTRIALIZED BUILDING PARTS AND COMPONENTS
2020, 50(8): 10-15.
doi: 10.13204/j.gyjzG20052509
Abstract:
The fast development of building industrialization has raised higher demands on the manufacturing of prefabricated structure and decoration components, and the informatization of product data and production process has become an important approach to guarantee the quality as well as to increase the efficiency. The paper summarized the technical status of the informatized production of concrete precast member, integrated bathroom, integrated kitchen and the internal separation in industrialized buildings, including the digitalized expression, data transformation and platforming during the design, library and production of those products. Based on the review, a new scheme of the integrated intelligent interaction platform containing four types of components was proposed.
The fast development of building industrialization has raised higher demands on the manufacturing of prefabricated structure and decoration components, and the informatization of product data and production process has become an important approach to guarantee the quality as well as to increase the efficiency. The paper summarized the technical status of the informatized production of concrete precast member, integrated bathroom, integrated kitchen and the internal separation in industrialized buildings, including the digitalized expression, data transformation and platforming during the design, library and production of those products. Based on the review, a new scheme of the integrated intelligent interaction platform containing four types of components was proposed.
2020, 50(8): 16-21.
doi: 10.13204/j.gyjzG20052510
Abstract:
With the advantages of free-form construction, labor and material saving, and environmental protection, 3D printing of concrete attracts more and more attention and develops rapidly. The key points of 3D printing technology include the preparation of materials, the determination of printing parameters and the formation of hardening properties of 3D-printed concrete. Based on the current research results, the paper summarized and discussed the printability and material composition, printing parameters and process control, as well as the hardening performance of 3D printing concrete, which is meaningful for the practice of 3D printing concrete engineering.
With the advantages of free-form construction, labor and material saving, and environmental protection, 3D printing of concrete attracts more and more attention and develops rapidly. The key points of 3D printing technology include the preparation of materials, the determination of printing parameters and the formation of hardening properties of 3D-printed concrete. Based on the current research results, the paper summarized and discussed the printability and material composition, printing parameters and process control, as well as the hardening performance of 3D printing concrete, which is meaningful for the practice of 3D printing concrete engineering.
2020, 50(8): 22-26,171.
doi: 10.13204/j.gyjzG20052511
Abstract:
3D concrete printing is quite different from 3D printing with other materials, printing the concrete modeling is under the influence of the molding process parameters and quality parameters. In order to put forward a modeling method that is suitable for concrete printing, the paper first discussed the steps of 3D printing modeling, then four factors that affect the modeling were studied, which indude print heads speed, discharging speed, lifting height and width of the lap joint, using the method of control variables, the paper explored the influence of each variable on concrele printing, so as to determine the optimal variable. The resules showed that when the traveling speed of printing head was about 30 mm/s, the rotation speed of screw was between 0.9~1.1 r/s, the width of concrete lap joint was more than 5 mm and the layer thickness was 13 mm, the overall deformation of printed concrete was very small, the width of printing lines was relatively ideal, and the modeling quality was high. Therefore, in the modeling process, the influence of process parameters on the modeling should be considered, which could greatly improve the molding quality of 3D printed concrete.
3D concrete printing is quite different from 3D printing with other materials, printing the concrete modeling is under the influence of the molding process parameters and quality parameters. In order to put forward a modeling method that is suitable for concrete printing, the paper first discussed the steps of 3D printing modeling, then four factors that affect the modeling were studied, which indude print heads speed, discharging speed, lifting height and width of the lap joint, using the method of control variables, the paper explored the influence of each variable on concrele printing, so as to determine the optimal variable. The resules showed that when the traveling speed of printing head was about 30 mm/s, the rotation speed of screw was between 0.9~1.1 r/s, the width of concrete lap joint was more than 5 mm and the layer thickness was 13 mm, the overall deformation of printed concrete was very small, the width of printing lines was relatively ideal, and the modeling quality was high. Therefore, in the modeling process, the influence of process parameters on the modeling should be considered, which could greatly improve the molding quality of 3D printed concrete.
2020, 50(8): 27-31,71.
doi: 10.13204/j.gyjzG20052507
Abstract:
The truss connection between the inner and outer leaf wall panels of the prefabricated concrete sandwich insulation wall is in the tension and shear state under the outer wall panel self weight and wind suction. In order to study the mechanical properties of the truss connection under tension and shear composite stress, 6 tensile-shear models of the Peikko PD truss connection were tested. The test results showed that the shear capacity of sandwich wall decreased with the increase of tensile force when the thickness of insulation layer was constant in the tension and shear state,while the shear capacity and deformation of sandwich wall increased with the increase of thickness of insulation layer when the tensile force was constant.According to the final failure form of the specimens, under the tensile-shear composite stress the failure form of the truss connection was that the web member in larger tension was broken or the welding spot was pulled apart at the joint.The test result showed that the tensile-shear bearing capacity of this kind of truss connectors was larger than the current design bearing capacity,which has a certain safety reserve.
The truss connection between the inner and outer leaf wall panels of the prefabricated concrete sandwich insulation wall is in the tension and shear state under the outer wall panel self weight and wind suction. In order to study the mechanical properties of the truss connection under tension and shear composite stress, 6 tensile-shear models of the Peikko PD truss connection were tested. The test results showed that the shear capacity of sandwich wall decreased with the increase of tensile force when the thickness of insulation layer was constant in the tension and shear state,while the shear capacity and deformation of sandwich wall increased with the increase of thickness of insulation layer when the tensile force was constant.According to the final failure form of the specimens, under the tensile-shear composite stress the failure form of the truss connection was that the web member in larger tension was broken or the welding spot was pulled apart at the joint.The test result showed that the tensile-shear bearing capacity of this kind of truss connectors was larger than the current design bearing capacity,which has a certain safety reserve.
2020, 50(8): 32-37,4.
doi: 10.13204/j.gyjzG20052512
Abstract:
Two standard wall panel units were tested under bending load to study the flexural behavior of light-gauge steel stud concrete composite wall panel (SC wall panel) and the stud spacing was considered as an experimental parameter. The experimental results showed that the failure of SC wall panels were mainly caused by the buckling of the stud and the bearing capacity of the SC wall panel was controlled by the serviceability limit state. Moreover, stud spacing had a great influence on the bearing capacity of the SC wall panels. Then, finite element models of SC wall panels were established with ABAQUS and a parameter analysis was conducted. The results showed that the flexural behavior of SC wall panels was mainly influenced by the thickness of the keel, the height of the web, the type of the thermal insulation material, the air layer and the spacing of the shear studs. The flexural capacity of the composite wall panels could be greatly improved when the air layer was cancelled. Besides, replacing the rock wool with foam concrete could effectively restrict the deformation of the stud and improve the flexural capacity and energy dissipation capacity of the SC wall panels.
Two standard wall panel units were tested under bending load to study the flexural behavior of light-gauge steel stud concrete composite wall panel (SC wall panel) and the stud spacing was considered as an experimental parameter. The experimental results showed that the failure of SC wall panels were mainly caused by the buckling of the stud and the bearing capacity of the SC wall panel was controlled by the serviceability limit state. Moreover, stud spacing had a great influence on the bearing capacity of the SC wall panels. Then, finite element models of SC wall panels were established with ABAQUS and a parameter analysis was conducted. The results showed that the flexural behavior of SC wall panels was mainly influenced by the thickness of the keel, the height of the web, the type of the thermal insulation material, the air layer and the spacing of the shear studs. The flexural capacity of the composite wall panels could be greatly improved when the air layer was cancelled. Besides, replacing the rock wool with foam concrete could effectively restrict the deformation of the stud and improve the flexural capacity and energy dissipation capacity of the SC wall panels.
2020, 50(8): 43-47.
doi: 10.13204/j.gyjzG20032604
Abstract:
The main research was on shaping characteristics of contemporary theatrical buildings. The paper analyzed the shaping motivation of theatrical buildings based on their functions, techniques, aesthetics and cultural connotations; and starting from spatial operations, symbolic metaphors and material optimization, discussed the constructing logic and development tendencies for large-scale public buildings by case study of several existing theatres and concert halls. Finally, shaping approaches to rational construction combining with conceptual design innovation of buildings were analyzed.
The main research was on shaping characteristics of contemporary theatrical buildings. The paper analyzed the shaping motivation of theatrical buildings based on their functions, techniques, aesthetics and cultural connotations; and starting from spatial operations, symbolic metaphors and material optimization, discussed the constructing logic and development tendencies for large-scale public buildings by case study of several existing theatres and concert halls. Finally, shaping approaches to rational construction combining with conceptual design innovation of buildings were analyzed.
2020, 50(8): 48-53.
doi: 10.13204/j.gyjzG20012202
Abstract:
With the transition of human society from industrial civilization to information civilization, industrial buildings built in cities in the industrial era have been gradually idled or abandoned, and in the process of continuous renewal and development, cities have changed from incremental expansion to connotation enhancement. Old industrial buildings as urban stock in China is bound to face recycling again. The paper introduced the recycling concept, taking Taiyuan’s old factory of pipe workshop as an example, and combined the three steps of overall safety control, self-recycling, and urban linkage development to explore the elements and methods of urban recycling and recycling of old industrial buildings. Its purpose was to promote the stable and continuous development of cities.
With the transition of human society from industrial civilization to information civilization, industrial buildings built in cities in the industrial era have been gradually idled or abandoned, and in the process of continuous renewal and development, cities have changed from incremental expansion to connotation enhancement. Old industrial buildings as urban stock in China is bound to face recycling again. The paper introduced the recycling concept, taking Taiyuan’s old factory of pipe workshop as an example, and combined the three steps of overall safety control, self-recycling, and urban linkage development to explore the elements and methods of urban recycling and recycling of old industrial buildings. Its purpose was to promote the stable and continuous development of cities.
2020, 50(8): 54-56,100.
doi: 10.13204/j.gyjzG20022111
Abstract:
The function of urban roadway is for vehicles to pass. The inspection well and drainage pipeline under urban roadway are used to solve the ground drainage problem, while the sidewalk almost only has the fuctions of allowing pedestrians to pass and separating vehicles and pedestrians. At present, the underground part of most sidewalks has not been effectively used. The paper analyzed the difficulties that needed to be solved by using the underground part of the sidewalk, and proposed an urban ecological sidewalk and green space construction method with composite irrigation and waterlogging prevention functions. Through the systematic design of storage and drainage layers, inspection wells, drainage pipes, infiltration irrigation pipes, etc., the organic connection among sidewalks, roadways and garden green spaces can improve the drainage efficiency of urban roads, and effectively store rainwater for plant irrigation to achieve the purpose of saving water resources.
The function of urban roadway is for vehicles to pass. The inspection well and drainage pipeline under urban roadway are used to solve the ground drainage problem, while the sidewalk almost only has the fuctions of allowing pedestrians to pass and separating vehicles and pedestrians. At present, the underground part of most sidewalks has not been effectively used. The paper analyzed the difficulties that needed to be solved by using the underground part of the sidewalk, and proposed an urban ecological sidewalk and green space construction method with composite irrigation and waterlogging prevention functions. Through the systematic design of storage and drainage layers, inspection wells, drainage pipes, infiltration irrigation pipes, etc., the organic connection among sidewalks, roadways and garden green spaces can improve the drainage efficiency of urban roads, and effectively store rainwater for plant irrigation to achieve the purpose of saving water resources.
2020, 50(8): 57-64,115.
doi: 10.13204/j.gyjzG19111001
Abstract:
In order to overcome the performance deficiencies of the traditional notched connection and dowel connection,a prefabricated composite connector with screw and reactive powder concrete (RPC) coating was proposed. The push-out test results showed that the slip stiffness and shear bearing capacity increased as increasing of the thickness of RPC cover. The main influence factor for the shear behavior of the connection was the outside diameter instead of the diameter of the screw. The proposed connection had the advantages of high stiffness,high ductility and easy assembly. The four-point bending test was carried out on 2 assembled glubam-concrete composite (BCC) beams with composite connectors.The results showed that the flexural behavior of the assembled BCC beams could be attributed to the partial composite action, corresponding that the connectors near the end of BCC beam exhibited relatively large shear deformation. The BCC beams also showed obvious signs before failure due to the excellent ductility of connection. Vertical anti-pull-out measurement of the composite connector was also reliable. Lightweight-concrete overlay could obviously improve the flexural stiffness and bearing capacity of BCC beams without significantly increasing self-weight of BCC beam. The γ-method, provided by Eurocode 5, was selected to evaluate the bearing capacity of the BCC beams, and the predicting results were significantly higher than the test data. Therefore, the γ-method is not suitable for BCC beams.
In order to overcome the performance deficiencies of the traditional notched connection and dowel connection,a prefabricated composite connector with screw and reactive powder concrete (RPC) coating was proposed. The push-out test results showed that the slip stiffness and shear bearing capacity increased as increasing of the thickness of RPC cover. The main influence factor for the shear behavior of the connection was the outside diameter instead of the diameter of the screw. The proposed connection had the advantages of high stiffness,high ductility and easy assembly. The four-point bending test was carried out on 2 assembled glubam-concrete composite (BCC) beams with composite connectors.The results showed that the flexural behavior of the assembled BCC beams could be attributed to the partial composite action, corresponding that the connectors near the end of BCC beam exhibited relatively large shear deformation. The BCC beams also showed obvious signs before failure due to the excellent ductility of connection. Vertical anti-pull-out measurement of the composite connector was also reliable. Lightweight-concrete overlay could obviously improve the flexural stiffness and bearing capacity of BCC beams without significantly increasing self-weight of BCC beam. The γ-method, provided by Eurocode 5, was selected to evaluate the bearing capacity of the BCC beams, and the predicting results were significantly higher than the test data. Therefore, the γ-method is not suitable for BCC beams.
2020, 50(8): 65-71.
doi: 10.13204/j.gyjzG201908210002
Abstract:
Based on the assumption of elastic pile-pile interaction, the pile-cap-soil interaction was analyzed by the shear displacement method, and an analytical method was then established to research bearing characteristics of group pile foundations embedded in stratified soil considering the reinforcement and barrier effects between piles and soil. Comparisons of the calculated results by the proposed method with the one by the finite element method and measured results, it was verified to be feasible.
Based on the assumption of elastic pile-pile interaction, the pile-cap-soil interaction was analyzed by the shear displacement method, and an analytical method was then established to research bearing characteristics of group pile foundations embedded in stratified soil considering the reinforcement and barrier effects between piles and soil. Comparisons of the calculated results by the proposed method with the one by the finite element method and measured results, it was verified to be feasible.
2020, 50(8): 72-79.
doi: 10.13204/j.gyjzG201905250002
Abstract:
Combined with a super high-rise complex project in Qingyang, Gansu, based on the monitoring data of piled-raft foundation settlement, the three-point method, modified hyperbolic method, Poisson curve method and creep settlement practical algorithm were used to predict the settlement of deep and thick loess foundation. The settlement of high-rise buildings on deep and thick loess foundation was predicted and compared with the measured data on a building site. The research showed that the modified hyperbolic method and the creep settlement practical algorithm were suitable for settlement prediction of super high-rise buildings on deep and thick loess foundation, and the latter could better predict settlement by existing limited measured data; the rationality of effective predict for the creep practical algorithm was verified and based on the settlement prediction about super high-rise buildings by the creep practical algorithm, the effective prediction range by the modified hyperbolic method was obtained according to existing measured data and allowable errors controlled less than 4 mm.
Combined with a super high-rise complex project in Qingyang, Gansu, based on the monitoring data of piled-raft foundation settlement, the three-point method, modified hyperbolic method, Poisson curve method and creep settlement practical algorithm were used to predict the settlement of deep and thick loess foundation. The settlement of high-rise buildings on deep and thick loess foundation was predicted and compared with the measured data on a building site. The research showed that the modified hyperbolic method and the creep settlement practical algorithm were suitable for settlement prediction of super high-rise buildings on deep and thick loess foundation, and the latter could better predict settlement by existing limited measured data; the rationality of effective predict for the creep practical algorithm was verified and based on the settlement prediction about super high-rise buildings by the creep practical algorithm, the effective prediction range by the modified hyperbolic method was obtained according to existing measured data and allowable errors controlled less than 4 mm.
2020, 50(8): 80-84.
doi: 10.13204/j.gyjzG201907080001
Abstract:
The large-scale dynamic machine foundation, nuclear power foundation, land wind power foundation and other infrastructures are easily impacted by the machine disturbance, seismic action, wind load and other dynamic effects, under the action of dynamic load, vibrations of operating machines will cause vibrations of foundations, which will have great adverse impacts on foundations. It may greatly reduce the bearing capacity of foundation and lead to difference settlement of foundation, which may affect normal operation of machines, and might even cause serious accidents in severe cases. A double-pile cap foundation is one of the most common basic forms of these foundations. Combined with actual test projects, two groups of double-pile cap foundations with the same sizes and form but different layout directions were designed. Dynamic vibration characteristics of the two double-pile cap foundation under the action of the vertical, horizontal and torsional vibration were carried out by high-power mechanical vibration exciters under surface and embeded conditions, respectively, to compare the dynamic parameters of each double-pile cap foundation in different directions. The results showed that although the sizes and cap foundation shapes of for the two foundations were the same, but the different structural arrangement directions would have a great difference on dynamic parameters of foundations. The difference would affect design parameters of equipment foundations, so the direction arrangements of double-pile cap foundations should be considered in design of two-pile cap dynamic foundations.
The large-scale dynamic machine foundation, nuclear power foundation, land wind power foundation and other infrastructures are easily impacted by the machine disturbance, seismic action, wind load and other dynamic effects, under the action of dynamic load, vibrations of operating machines will cause vibrations of foundations, which will have great adverse impacts on foundations. It may greatly reduce the bearing capacity of foundation and lead to difference settlement of foundation, which may affect normal operation of machines, and might even cause serious accidents in severe cases. A double-pile cap foundation is one of the most common basic forms of these foundations. Combined with actual test projects, two groups of double-pile cap foundations with the same sizes and form but different layout directions were designed. Dynamic vibration characteristics of the two double-pile cap foundation under the action of the vertical, horizontal and torsional vibration were carried out by high-power mechanical vibration exciters under surface and embeded conditions, respectively, to compare the dynamic parameters of each double-pile cap foundation in different directions. The results showed that although the sizes and cap foundation shapes of for the two foundations were the same, but the different structural arrangement directions would have a great difference on dynamic parameters of foundations. The difference would affect design parameters of equipment foundations, so the direction arrangements of double-pile cap foundations should be considered in design of two-pile cap dynamic foundations.
2020, 50(8): 85-91.
doi: 10.13204/j.gyjzG19110708
Abstract:
The effects of three key factors, including cryogenic temperature, concrete water content and strength grade, on concrete tensile strength were discussed through the splitting tensile experiment under cryogenic temperatures from -40 ℃ to -180 ℃ for the concrete with different water contents (2.0% to 5.5%) and strength grades (C30, C40 and C50), and the corresponding coupling action relationship was also fitted out. From the test results it was shown that the higher the strength grade and water content of concrete, and the lower the cryogenic temperature, the more flat the failure surface and the more obvious the splitting phenomenon of coarse aggregates located in the failure surface. The tensile strength of concrete increased with the increase of water content, and decreased with the decrease in cryogenic temperature at same other conditions, and then tended to be stable. However, the influence of concrete strength grade on its cryogenic temperature tensile strength was relatively small, and the higher the water content, the smaller the increase in splitting tensile strength for the concrete with higher strength grades. These test results and the expressions of concrete splitting tensile strength at cryogenic temperature, including three key factors of cryogenic temperature, water content and strength grade, could be used as references for the improvement of relevant theories and the design and safety evaluation of ultralow temperature concrete structures.
The effects of three key factors, including cryogenic temperature, concrete water content and strength grade, on concrete tensile strength were discussed through the splitting tensile experiment under cryogenic temperatures from -40 ℃ to -180 ℃ for the concrete with different water contents (2.0% to 5.5%) and strength grades (C30, C40 and C50), and the corresponding coupling action relationship was also fitted out. From the test results it was shown that the higher the strength grade and water content of concrete, and the lower the cryogenic temperature, the more flat the failure surface and the more obvious the splitting phenomenon of coarse aggregates located in the failure surface. The tensile strength of concrete increased with the increase of water content, and decreased with the decrease in cryogenic temperature at same other conditions, and then tended to be stable. However, the influence of concrete strength grade on its cryogenic temperature tensile strength was relatively small, and the higher the water content, the smaller the increase in splitting tensile strength for the concrete with higher strength grades. These test results and the expressions of concrete splitting tensile strength at cryogenic temperature, including three key factors of cryogenic temperature, water content and strength grade, could be used as references for the improvement of relevant theories and the design and safety evaluation of ultralow temperature concrete structures.
2020, 50(8): 92-100.
doi: 10.13204/j.gyjzG201905290010
Abstract:
Axial compressive tests were conducted on 48 UHPC (ultra-high performance concrete) cubes cured under sprinkler curing, hot water curing, sprinkler-dry air combined curing, and hot water and dry air combined curing respectively to investigate residual compressive strength of heat-damaged. Axial tensile tests were conducted on 18 dumbbell-shaped specimens cured under hot water curing and hot water and dry air combined curing respectively to investigate the residual tensile strength. The test results showed that compared with the corresponding mono-curing regime, the compressive strength of the specimens subjected to sprinkling-dry air (105 ℃) combined curing and hot water and dry air (105 ℃) combined curing decreased by 36.73% and 14.56%, respectively, and spalled at the temperature of 348 ℃ and 370 ℃, respectively. The residual compressive strength of UHPC subjected to sprinkling-dry air (200 ℃ ) curing regime increased at first and then decreased during the increase of temperature, and the critical temperature was 300 ℃, at which showed the best explosive spalling resistance performance. Residual axial tensile strength of specimen subjected to hot water and dry air (105 ℃) curing also increased firstly and then decreased with the increasing temperature, the axial tensile strength cured under hot water and dry air (105 ℃) curing was only 54.05% of that under hot water curing. The dumbbell-shaped specimens could not avoid the occurrence of explosive spalling when the temperature was over 400 ℃.
Axial compressive tests were conducted on 48 UHPC (ultra-high performance concrete) cubes cured under sprinkler curing, hot water curing, sprinkler-dry air combined curing, and hot water and dry air combined curing respectively to investigate residual compressive strength of heat-damaged. Axial tensile tests were conducted on 18 dumbbell-shaped specimens cured under hot water curing and hot water and dry air combined curing respectively to investigate the residual tensile strength. The test results showed that compared with the corresponding mono-curing regime, the compressive strength of the specimens subjected to sprinkling-dry air (105 ℃) combined curing and hot water and dry air (105 ℃) combined curing decreased by 36.73% and 14.56%, respectively, and spalled at the temperature of 348 ℃ and 370 ℃, respectively. The residual compressive strength of UHPC subjected to sprinkling-dry air (200 ℃ ) curing regime increased at first and then decreased during the increase of temperature, and the critical temperature was 300 ℃, at which showed the best explosive spalling resistance performance. Residual axial tensile strength of specimen subjected to hot water and dry air (105 ℃) curing also increased firstly and then decreased with the increasing temperature, the axial tensile strength cured under hot water and dry air (105 ℃) curing was only 54.05% of that under hot water curing. The dumbbell-shaped specimens could not avoid the occurrence of explosive spalling when the temperature was over 400 ℃.
2020, 50(8): 101-104,159.
doi: 10.13204/j.gyjzG20010102
Abstract:
Shield tunnel construction has entered a period of rapid development in China. At present, shield method with reinforced concrete segments is still the main support form of shield tunnel, but ordinary reinforced concrete segments are thick, heavy, and easy to be damaged and cracked under fabrication, transportation and construction. Through proportion optimization design of steel fiber reinforced concrete mix, it was concluded that the compressive strength of concrete by the secondary synthesis method and equal-volume coarse aggregate replacement instead of steel fiber method was 17.7% and 13.1% higher than that of ordinary concrete, and the splitting strength by both of the methods was 54.2% and 51.1% higher than that of ordinary concrete, respectively. From the aspect of material consumption, the cementitious material consumption could be reduced 25.9% by the equal-volume coarse aggregate replacement method than the secondary synthesis method, and the cost control of steel fiber concrete was more reasonable, which was a relatively economical design method of steel fiber concrete.
Shield tunnel construction has entered a period of rapid development in China. At present, shield method with reinforced concrete segments is still the main support form of shield tunnel, but ordinary reinforced concrete segments are thick, heavy, and easy to be damaged and cracked under fabrication, transportation and construction. Through proportion optimization design of steel fiber reinforced concrete mix, it was concluded that the compressive strength of concrete by the secondary synthesis method and equal-volume coarse aggregate replacement instead of steel fiber method was 17.7% and 13.1% higher than that of ordinary concrete, and the splitting strength by both of the methods was 54.2% and 51.1% higher than that of ordinary concrete, respectively. From the aspect of material consumption, the cementitious material consumption could be reduced 25.9% by the equal-volume coarse aggregate replacement method than the secondary synthesis method, and the cost control of steel fiber concrete was more reasonable, which was a relatively economical design method of steel fiber concrete.
2020, 50(8): 105-115.
doi: 10.13204/j.gyjzG19120404
Abstract:
The shape of the gymnasium of Luan Sports Center is similar to the famous top ten tea products "Luan Guapian", the structure of the gymnasium adopts a space specially-shaped curved steel truss structure with a span of 89.7 m. This paper first proposed three construction plans. Multi-point asymmetrical overall lifting synchronous control scheme with lifting frames in the gymnasium was determined, by comparing the technological advancement, construction safety and economic rationality. Multi-point asymmetric overall lifting synchronous control technique was developed for a space specially-shaped curved steel truss structure. The paper focused on the principle of asymmetric lifting synchronous control of lifting equipment and systems, optimize the lifting point scheme and designed the lifting frame, etc. Using MIDAS, the entire simulation of synchronous lifting and asynchronous lifting was carried out, which provided countermeasures for the overall lifting scheme. Real-time monitoring system based on mass data processing and real-time transmission of cloud platform for stadium steel structures was developed, and the actual measurement results were compared with simulations. The results showed that the multi-point asymmetric overall lifting synchronous control technique was suitable for the construction of the roof structure of the gymnasium of Luan Sports Center. The cloud platform real-time monitoring technology and numerical simulation technology could ensure the safety and reliability of the construction.
The shape of the gymnasium of Luan Sports Center is similar to the famous top ten tea products "Luan Guapian", the structure of the gymnasium adopts a space specially-shaped curved steel truss structure with a span of 89.7 m. This paper first proposed three construction plans. Multi-point asymmetrical overall lifting synchronous control scheme with lifting frames in the gymnasium was determined, by comparing the technological advancement, construction safety and economic rationality. Multi-point asymmetric overall lifting synchronous control technique was developed for a space specially-shaped curved steel truss structure. The paper focused on the principle of asymmetric lifting synchronous control of lifting equipment and systems, optimize the lifting point scheme and designed the lifting frame, etc. Using MIDAS, the entire simulation of synchronous lifting and asynchronous lifting was carried out, which provided countermeasures for the overall lifting scheme. Real-time monitoring system based on mass data processing and real-time transmission of cloud platform for stadium steel structures was developed, and the actual measurement results were compared with simulations. The results showed that the multi-point asymmetric overall lifting synchronous control technique was suitable for the construction of the roof structure of the gymnasium of Luan Sports Center. The cloud platform real-time monitoring technology and numerical simulation technology could ensure the safety and reliability of the construction.
2020, 50(8): 116-119,188.
doi: 10.13204/j.gyjzG20042711
Abstract:
In order to solve the problem that the key parts of the down-hole drilling rig are prone to fatigue damage, the flexible multi-body dynamic model which can reflect the mechanical characteristics of the down-hole drilling rig working device was established by using Lagrange equation and mode superposition method. Using virtual prototyping technology and ADAMS simulation platform, the dynamic analysis of the working device was realized. The stress spectrum of the key parts of the working device of the down-hole drilling machine was obtained by using the measured load spectrum. Based on the nominal stress method, the fatigue damage assessment was realized. The results showed that the stress of fatigue focus could be accurately obtained by the dynamic simulation of flexible multi-body considering the motion attitude of working device, drilling shaft pressure and rotary torque. The most dangerous position of fatigue damage was the hinge of each oil cylinder and welding part of drill arm and the root of hinge support. The stress, fatigue damage and fatigue life of each fatigue focus point were obtained by flexible multi-body dynamics simulation, which could provide a reference for the structural strength improvement and lightweight design.
In order to solve the problem that the key parts of the down-hole drilling rig are prone to fatigue damage, the flexible multi-body dynamic model which can reflect the mechanical characteristics of the down-hole drilling rig working device was established by using Lagrange equation and mode superposition method. Using virtual prototyping technology and ADAMS simulation platform, the dynamic analysis of the working device was realized. The stress spectrum of the key parts of the working device of the down-hole drilling machine was obtained by using the measured load spectrum. Based on the nominal stress method, the fatigue damage assessment was realized. The results showed that the stress of fatigue focus could be accurately obtained by the dynamic simulation of flexible multi-body considering the motion attitude of working device, drilling shaft pressure and rotary torque. The most dangerous position of fatigue damage was the hinge of each oil cylinder and welding part of drill arm and the root of hinge support. The stress, fatigue damage and fatigue life of each fatigue focus point were obtained by flexible multi-body dynamics simulation, which could provide a reference for the structural strength improvement and lightweight design.
EXPERIMENTAL RESEARCH ON A NON-WELDING Y-SHAPED STRENGTHENING TECHNIQUE OF POWER TRANSMISSION TOWERS
2020, 50(8): 120-127.
doi: 10.13204/j.gyjzG201906060007
Abstract:
The bearing capacity of the existing power transmission tower which has been in operation for a long time is reduced, and there is a risk of collapse in strong wind. In the paper, a Y-shaped strengthening technical scheme which can be applied to the existing transmission tower members was presented. The scheme does not need welding and is convenient for construction. Axial compression tests on one unstrengthened specimen and two strengthened specimens adopting this scheme were carried out. The results showed that the axial load bearing capacity of the specimen adopting Y-shaped strengthening scheme was significantly improved. The bearing capacity of the two strengthened specimens was 1.25 and 1.53 times higher than that of the unstrengthened one, respectively. It indicated that the Y-shaped strengthening scheme could effectively improve the bearing capacity of the original section. The friction between the original and auxiliary materials generated by the clamps could gradually transmit the axial force of the original section to the strengthened section, making the original materials and the strengthening components resist the load together. In the later loading stage, the force transmission efficiency of each cross section tended to be stable, and after a certain distance from the loading end, the force transmission efficiency could reach 40% to 60%.
The bearing capacity of the existing power transmission tower which has been in operation for a long time is reduced, and there is a risk of collapse in strong wind. In the paper, a Y-shaped strengthening technical scheme which can be applied to the existing transmission tower members was presented. The scheme does not need welding and is convenient for construction. Axial compression tests on one unstrengthened specimen and two strengthened specimens adopting this scheme were carried out. The results showed that the axial load bearing capacity of the specimen adopting Y-shaped strengthening scheme was significantly improved. The bearing capacity of the two strengthened specimens was 1.25 and 1.53 times higher than that of the unstrengthened one, respectively. It indicated that the Y-shaped strengthening scheme could effectively improve the bearing capacity of the original section. The friction between the original and auxiliary materials generated by the clamps could gradually transmit the axial force of the original section to the strengthened section, making the original materials and the strengthening components resist the load together. In the later loading stage, the force transmission efficiency of each cross section tended to be stable, and after a certain distance from the loading end, the force transmission efficiency could reach 40% to 60%.
2020, 50(8): 128-133.
doi: 10.13204/j.gyjzG201908200007
Abstract:
Electricity transmission lines consists of transmission tower structure and conductors as well as ground wires. Coupling effects of the system are prominent. In order to study the influence of transmission lines on transmission tower under earthquake actions, two finite element models were established based on a 220 kV transmission project, including a single tower model and a tower-line coupling model. Dynamic characteristics analysis and seismic time history analysis were carried out for the two models. By comparing the results of the two models, it can be found that the frequency of transmission tower in the tower-line coupling model was less than that of single tower model. Seismic responses of the transmission tower in the tower-line coupling model with low seismic intensity was higher than that of the single tower model, while the result could be the opposite with high seismic intensity. The mass of transmission lines would amplify the seismic responses of transmission tower, while the nonlinear vibration of them could also dissipate some seismic energy, thus reducing the seismic responses of transmission tower. The nonlinear energy dissipation effects would become more and more obvious with the increase of seismic input intensity.
Electricity transmission lines consists of transmission tower structure and conductors as well as ground wires. Coupling effects of the system are prominent. In order to study the influence of transmission lines on transmission tower under earthquake actions, two finite element models were established based on a 220 kV transmission project, including a single tower model and a tower-line coupling model. Dynamic characteristics analysis and seismic time history analysis were carried out for the two models. By comparing the results of the two models, it can be found that the frequency of transmission tower in the tower-line coupling model was less than that of single tower model. Seismic responses of the transmission tower in the tower-line coupling model with low seismic intensity was higher than that of the single tower model, while the result could be the opposite with high seismic intensity. The mass of transmission lines would amplify the seismic responses of transmission tower, while the nonlinear vibration of them could also dissipate some seismic energy, thus reducing the seismic responses of transmission tower. The nonlinear energy dissipation effects would become more and more obvious with the increase of seismic input intensity.
2020, 50(8): 134-137.
doi: 10.13204/j.gyjzG201906260002
Abstract:
In order to study the bending behavior of aluminum alloy beams with rectangular section, monotonic loading tests were carried out on 9 aluminum alloy beams with shear-span ratios of 1.5, 2 and 2.5 in the paper. Typical failure models, load-deflection curves and peak loads of each specimen were analyzed. The calculated ultimate bearing capacity and measured results were compared. The results showed that with the increase of shear-span ratio, the ultimate bearing capacity of each specimen decreased gradually, and the corresponding deflection of mid-span increased gradually. The calculated values of the ultimate bearing capacity of all specimens were basically consistent with the measured results. With the increase of shear-span ratio, the specimen changed from shear deformation to flexural deformation.
In order to study the bending behavior of aluminum alloy beams with rectangular section, monotonic loading tests were carried out on 9 aluminum alloy beams with shear-span ratios of 1.5, 2 and 2.5 in the paper. Typical failure models, load-deflection curves and peak loads of each specimen were analyzed. The calculated ultimate bearing capacity and measured results were compared. The results showed that with the increase of shear-span ratio, the ultimate bearing capacity of each specimen decreased gradually, and the corresponding deflection of mid-span increased gradually. The calculated values of the ultimate bearing capacity of all specimens were basically consistent with the measured results. With the increase of shear-span ratio, the specimen changed from shear deformation to flexural deformation.
2020, 50(8): 138-144,53.
doi: 10.13204/j.gyjzG201908130009
Abstract:
In order to study the compressive bearing capacity of concrete-filled steel tube (CFST) members with defects, the bearing capacity tests of 9 groups of CFST defective members were carried out, and the change curve of axial deformation of CFST defective members with load strength was obtained. The results showed that the defect had a great influence on the compressive bearing capacity of concrete-filled steel tube specimens, compared with non-defective components, the bearing capacity loss of defective components was as low as 14% and as high as 59%. With the same defect location, the bearing capacity loss of concrete-filled steel tube members was proportional to the defect ratio. The loss of bearing capacity caused by edge defect was greater than that caused by central defect. Through the finite element software, the simulation model of concrete-filled steel tube (CFST) was established, the structure type was expanded, and the accuracy of the test results was verified.
In order to study the compressive bearing capacity of concrete-filled steel tube (CFST) members with defects, the bearing capacity tests of 9 groups of CFST defective members were carried out, and the change curve of axial deformation of CFST defective members with load strength was obtained. The results showed that the defect had a great influence on the compressive bearing capacity of concrete-filled steel tube specimens, compared with non-defective components, the bearing capacity loss of defective components was as low as 14% and as high as 59%. With the same defect location, the bearing capacity loss of concrete-filled steel tube members was proportional to the defect ratio. The loss of bearing capacity caused by edge defect was greater than that caused by central defect. Through the finite element software, the simulation model of concrete-filled steel tube (CFST) was established, the structure type was expanded, and the accuracy of the test results was verified.
2020, 50(8): 145-153,127.
doi: 10.13204/j.gyjzG19102302
Abstract:
In order to study the seismic behavior of prefabricated SRC composite tube (SRCT) shear wall structures, a full-scale model quasi-static test of three prefabricated SRCT shear wall specimens was conducted. The performance of the specimens was evaluated in terms of cracking and failure mode, hysteretic curves, displacement ductility, stiffness degradation and energy dissipation capacity, et al. The results revealed that during the loading process, the concrete and the steel plate cooperated well, and the material function of each part was clear, showing a good overall load performance. SRCT shear wall had high bearing capacity and stiffness, which could meet the aseismatic fortification target of "no collapse under severe earthqnake". The hysteresis curve of the specimen was full, and the displacement ductility coefficient was about 3, showing a good plastic deformation performance and energy dissipation capacity. The distance to thickness ratio had little effect on the bearing capacity and energy dissipation capacity. With the decrease of distance to thickness ratio, the stiffness degraded faster and the ductility decreased slightly. With the decrease of distance to thickness ratio, the tear plate was not easy to buckle, and the internal failure modes changed from local buckling and fracture of U-shaped steel and steel plates to fracture of welds. Reliable measures should be taken to improve the bearing capacity and welding quality of thin steel plate to avoid welding damage. Other connection methods such as bolt connection could also be used.
In order to study the seismic behavior of prefabricated SRC composite tube (SRCT) shear wall structures, a full-scale model quasi-static test of three prefabricated SRCT shear wall specimens was conducted. The performance of the specimens was evaluated in terms of cracking and failure mode, hysteretic curves, displacement ductility, stiffness degradation and energy dissipation capacity, et al. The results revealed that during the loading process, the concrete and the steel plate cooperated well, and the material function of each part was clear, showing a good overall load performance. SRCT shear wall had high bearing capacity and stiffness, which could meet the aseismatic fortification target of "no collapse under severe earthqnake". The hysteresis curve of the specimen was full, and the displacement ductility coefficient was about 3, showing a good plastic deformation performance and energy dissipation capacity. The distance to thickness ratio had little effect on the bearing capacity and energy dissipation capacity. With the decrease of distance to thickness ratio, the stiffness degraded faster and the ductility decreased slightly. With the decrease of distance to thickness ratio, the tear plate was not easy to buckle, and the internal failure modes changed from local buckling and fracture of U-shaped steel and steel plates to fracture of welds. Reliable measures should be taken to improve the bearing capacity and welding quality of thin steel plate to avoid welding damage. Other connection methods such as bolt connection could also be used.
2020, 50(8): 154-159.
doi: 10.13204/j.gyjzG20030902
Abstract:
In order to study the mechanical properties of continuous curved composite girder bridges during operation, taking the actual project of ramp C of Zhibu South Junction as the background, considering the influence of the connection mode of the diaphragms and the curve radius, three continuous curved composite girders with a scale reduction ratio of 1∶10 compared with the actual case were designed. Static load tests under four operating conditions were carried out.The load-deflection curves and the distribution law of the control sections strain along the height and transverse direction under the working conditions were obtained. A comparative study found that under the four operating conditions the partial load of the outer box was the most disadvantaged for cross-center deflection. The eccentric load factor of the composite girder was around 1.30. The curve radius had a certain effect on the mechanical properties of the curved composite girder, and the connection method of the diaphragms had little effect on it.
In order to study the mechanical properties of continuous curved composite girder bridges during operation, taking the actual project of ramp C of Zhibu South Junction as the background, considering the influence of the connection mode of the diaphragms and the curve radius, three continuous curved composite girders with a scale reduction ratio of 1∶10 compared with the actual case were designed. Static load tests under four operating conditions were carried out.The load-deflection curves and the distribution law of the control sections strain along the height and transverse direction under the working conditions were obtained. A comparative study found that under the four operating conditions the partial load of the outer box was the most disadvantaged for cross-center deflection. The eccentric load factor of the composite girder was around 1.30. The curve radius had a certain effect on the mechanical properties of the curved composite girder, and the connection method of the diaphragms had little effect on it.
2020, 50(8): 160-165,181.
doi: 10.13204/j.gyjzG201906150004
Abstract:
In order to explore the mechanical properties of steel-bamboo composite I-beam after being subjected to long-term loading, eight steel-bamboo composite I-beam specimens were designed and fabricated with the parameters of bamboo plate thickness, steel plate thickness and width, and section height. Four of them were long-term loaded specimens. After being subjected to long-term loading, secondary loading failure tests were carried out. The other four were short-term loaded specimens, and loading failure tests were carried out directly for comparison. The long-term and short-term loaded specimens were analyzed, and the failure characteristics, failure modes and failure loads were compared. The load-strain relationship, load-deflection relationship and bearing capacity attenuation of steel-bamboo composite I-beams were studied. The calculation method of bearing capacity and deflection of steel-bamboo composite I-beams after being subjected to long-term loading was discussed. The test results showed that the steel-bamboo composite I-beams still had good mechanical properties after being subjected to long-term loading. Long-term load had no effect on the ultimate failure mode of steel-bamboo composite I-beams. The secondary loading failure and direct loading failure of composite beams had four stages of elasticity, yield, cracking and ultimate strength. The flexural deformation of long-term loaded specimens was little different from that of short-term loaded specimens. Increasing the thickness, width and section height of bamboo plate could improve the ultimate bearing capacity of long-term loaded specimens. The bearing capacity of long-term loaded specimens decreased by about 10%. This paper calculated the bearing capacity and deflection of steel-bamboo composite I-beams after being subjected to long-term loading by using the proposed formula, and the theoretical value was in good agreement with the experimental value.
In order to explore the mechanical properties of steel-bamboo composite I-beam after being subjected to long-term loading, eight steel-bamboo composite I-beam specimens were designed and fabricated with the parameters of bamboo plate thickness, steel plate thickness and width, and section height. Four of them were long-term loaded specimens. After being subjected to long-term loading, secondary loading failure tests were carried out. The other four were short-term loaded specimens, and loading failure tests were carried out directly for comparison. The long-term and short-term loaded specimens were analyzed, and the failure characteristics, failure modes and failure loads were compared. The load-strain relationship, load-deflection relationship and bearing capacity attenuation of steel-bamboo composite I-beams were studied. The calculation method of bearing capacity and deflection of steel-bamboo composite I-beams after being subjected to long-term loading was discussed. The test results showed that the steel-bamboo composite I-beams still had good mechanical properties after being subjected to long-term loading. Long-term load had no effect on the ultimate failure mode of steel-bamboo composite I-beams. The secondary loading failure and direct loading failure of composite beams had four stages of elasticity, yield, cracking and ultimate strength. The flexural deformation of long-term loaded specimens was little different from that of short-term loaded specimens. Increasing the thickness, width and section height of bamboo plate could improve the ultimate bearing capacity of long-term loaded specimens. The bearing capacity of long-term loaded specimens decreased by about 10%. This paper calculated the bearing capacity and deflection of steel-bamboo composite I-beams after being subjected to long-term loading by using the proposed formula, and the theoretical value was in good agreement with the experimental value.
2020, 50(8): 166-171.
doi: 10.13204/j.gyjzG20041404
Abstract:
By setting the activation and deactivation elements and the Bao-Wierzbickis damage criterion, the loading and carbon fiber reinforcement process and the damage situation of the joint area can be simulated, and the ideal calculation accuracy can be obtained. 111 models (0.63≤β ≤ 0.76, 9.70 ≤ γ≤16.92) were numerically analyzed, and the mechanism of CFRP reinforcement was analyzed by comparing the equivalent plastic strains of the measuring points around the intersection line. And by comparing with the reference specimen, the influence of different damage conditions on the bearing capacity of the joints was analyzed. The research results showed that CFRP almost lost the reinforcement effect when the depression displacement of the chord is about one-fifth of the diameter of the chord; the maximum bearing capacity of the damaged joint increased with the increase of the diameter of the chord and the elastic modulus and thickness of the CFRP, and decreased with the thickness of the chord. When the winding orientations of CFRP was close to the circumferential direction, the reinforcement effect of the damaged joint was better.
By setting the activation and deactivation elements and the Bao-Wierzbickis damage criterion, the loading and carbon fiber reinforcement process and the damage situation of the joint area can be simulated, and the ideal calculation accuracy can be obtained. 111 models (0.63≤β ≤ 0.76, 9.70 ≤ γ≤16.92) were numerically analyzed, and the mechanism of CFRP reinforcement was analyzed by comparing the equivalent plastic strains of the measuring points around the intersection line. And by comparing with the reference specimen, the influence of different damage conditions on the bearing capacity of the joints was analyzed. The research results showed that CFRP almost lost the reinforcement effect when the depression displacement of the chord is about one-fifth of the diameter of the chord; the maximum bearing capacity of the damaged joint increased with the increase of the diameter of the chord and the elastic modulus and thickness of the CFRP, and decreased with the thickness of the chord. When the winding orientations of CFRP was close to the circumferential direction, the reinforcement effect of the damaged joint was better.
2020, 50(8): 172-176.
doi: 10.13204/j.gyjzG201908060007
Abstract:
In order to study the effect of sulfate corrosion on the mechanical properties of CFRP (carbon fiber reinforced polymer) sheets, unidirectional tensile tests were carried out on 11 groups of 77 CFRP specimens. The effects of sulfate concentration and corrosion time on tensile failure characteristics, tensile strength, modulus of elasticity and elongation of CFRP sheets were considered. The results showed that: 1) Sulfate dry-wet circulation has little effect on the failure process and failure characteristics of CFRP sheet; 2) The stress-strain relationship of CFRP sheets before and after corrosion was linear elasticity; 3) The tensile strength and elongation of CFRP sheets decreased with the increase of corrosion time, and the more significant the sulfate concentration was higher; 4) Sulfate dry and wet cycle has little effect on the elastic modulus of CFRP sheet. Based on the analysis of the test data, the calculation method of tensile strength considering corrosion time was proposed. The calculated method could reflect the degradation law of tensile strength of CFRP sheet under the action of sulfate dry and wet cycle by comparing the calculated value with the experimental value.
In order to study the effect of sulfate corrosion on the mechanical properties of CFRP (carbon fiber reinforced polymer) sheets, unidirectional tensile tests were carried out on 11 groups of 77 CFRP specimens. The effects of sulfate concentration and corrosion time on tensile failure characteristics, tensile strength, modulus of elasticity and elongation of CFRP sheets were considered. The results showed that: 1) Sulfate dry-wet circulation has little effect on the failure process and failure characteristics of CFRP sheet; 2) The stress-strain relationship of CFRP sheets before and after corrosion was linear elasticity; 3) The tensile strength and elongation of CFRP sheets decreased with the increase of corrosion time, and the more significant the sulfate concentration was higher; 4) Sulfate dry and wet cycle has little effect on the elastic modulus of CFRP sheet. Based on the analysis of the test data, the calculation method of tensile strength considering corrosion time was proposed. The calculated method could reflect the degradation law of tensile strength of CFRP sheet under the action of sulfate dry and wet cycle by comparing the calculated value with the experimental value.
2020, 50(8): 177-181.
doi: 10.13204/j.gyjzG201908020013
Abstract:
Due to the large size of the existing fiber reinforced anchorage is not conducive to engineering application, a new type of multi-cone anchorage structure was proposed. Its outer diameter is small, and the extrusion stress of multi-cone adjustable tendons can reduce the extrusion stress concentration at the loading end. Static tension tests were carried out to verify the effectiveness of the multi-cone anchorage. The experimental phenomena, anchorage efficiency coefficient and the extrusion stress at the loading end of the tendon were analyzed. The results showed that no slippage occurred in the multi-cone anchorage structure, and the anchorage efficiency coefficient reached more than 90%, which met the requirements of the cable anchorage design standard; the circumferential stress of the anchorage could reflect the radial extrusion stress of the internal tendons, and the difference between the circumferential stress of the two inner cones was not significant, which indicated that the new anchorage could effectively reduce the extrusion stress concentration of the tendons at the loading end of the anchorage.
Due to the large size of the existing fiber reinforced anchorage is not conducive to engineering application, a new type of multi-cone anchorage structure was proposed. Its outer diameter is small, and the extrusion stress of multi-cone adjustable tendons can reduce the extrusion stress concentration at the loading end. Static tension tests were carried out to verify the effectiveness of the multi-cone anchorage. The experimental phenomena, anchorage efficiency coefficient and the extrusion stress at the loading end of the tendon were analyzed. The results showed that no slippage occurred in the multi-cone anchorage structure, and the anchorage efficiency coefficient reached more than 90%, which met the requirements of the cable anchorage design standard; the circumferential stress of the anchorage could reflect the radial extrusion stress of the internal tendons, and the difference between the circumferential stress of the two inner cones was not significant, which indicated that the new anchorage could effectively reduce the extrusion stress concentration of the tendons at the loading end of the anchorage.
2020, 50(8): 182-188.
doi: 10.13204/j.gyjzG201908190001
Abstract:
It was found that longitudinal cracking phenomenon could be observed in tensile fatigue test of GFRP pre-tightened teeth connection (PTTC), which seriously affected the static and fatigue properties of the joint. The mechanism of longitudinal cracking was explained from two aspects by theoretical and numerical analysis. The results showed that: the internal interference fit of aluminum sleeve and the tensile load acting on the end of GFRP tube leaded to excessive hoop tensile stress in GFRP tube. Meanwhile, under tensile load, the helix angle caused torsional shear stress in GFRP tube. For the unidirectional fiber reinforced GFRP pultrusion tube, its tensile property was poor, so the hoop tensile stress should be strictly controlled or avoided in engineering.
It was found that longitudinal cracking phenomenon could be observed in tensile fatigue test of GFRP pre-tightened teeth connection (PTTC), which seriously affected the static and fatigue properties of the joint. The mechanism of longitudinal cracking was explained from two aspects by theoretical and numerical analysis. The results showed that: the internal interference fit of aluminum sleeve and the tensile load acting on the end of GFRP tube leaded to excessive hoop tensile stress in GFRP tube. Meanwhile, under tensile load, the helix angle caused torsional shear stress in GFRP tube. For the unidirectional fiber reinforced GFRP pultrusion tube, its tensile property was poor, so the hoop tensile stress should be strictly controlled or avoided in engineering.
2020, 50(8): 189-193.
doi: 10.13204/j.gyjzG201903230004
Abstract:
Spencer Station was built in the early 1960s and was the foundation of the development and prosperity of Melbourne, Australia. In order to improve the condition of the old station on the lack of corresponding infrastructure (comfortable waiting area, public open space, the platform of sunroof and the convenient contact with subway, etc.), and to promote the development of the area surrounding the station, the transformation took a more modern facilities, indoor and outdoor public space, retail shops and restaurants, taxi and subway and bus transfer area and other measures and means. Spencer Station will become a new landmark for Melbourne, the gateway between the Central Business District and the Dockland.
Spencer Station was built in the early 1960s and was the foundation of the development and prosperity of Melbourne, Australia. In order to improve the condition of the old station on the lack of corresponding infrastructure (comfortable waiting area, public open space, the platform of sunroof and the convenient contact with subway, etc.), and to promote the development of the area surrounding the station, the transformation took a more modern facilities, indoor and outdoor public space, retail shops and restaurants, taxi and subway and bus transfer area and other measures and means. Spencer Station will become a new landmark for Melbourne, the gateway between the Central Business District and the Dockland.
