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2023 Vol. 53, No. 7
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2023, 53(7): 1-6.
doi: 10.13204/j.gyjzG22062309
Abstract:
The indoor thermal environment of buildings in Qinghai-Tibet Plateau is a serious problem in winter, which is manifested by the large diurnal temperature difference and the low diurnal temperature in the North.The paper explored the correlation mechanism between solar energy utilization and building space, and constructed a theoretical model of space regulation. In order to demonstrate the superiority of the theory model, a comparative study of indoor thermal environment before and after the renovation was carried out to typical buildings.The purpose of the paper was to establish an architectural space regulation method of solar energy utilization in order to solve the spatial-temporal imbalance in Qinghai-Tibet Plateau.
The indoor thermal environment of buildings in Qinghai-Tibet Plateau is a serious problem in winter, which is manifested by the large diurnal temperature difference and the low diurnal temperature in the North.The paper explored the correlation mechanism between solar energy utilization and building space, and constructed a theoretical model of space regulation. In order to demonstrate the superiority of the theory model, a comparative study of indoor thermal environment before and after the renovation was carried out to typical buildings.The purpose of the paper was to establish an architectural space regulation method of solar energy utilization in order to solve the spatial-temporal imbalance in Qinghai-Tibet Plateau.
2023, 53(7): 7-15,31.
doi: 10.13204/j.gyjzG22020705
Abstract:
The arid climate of China is mainly distributed in the southern part of Xinjiang, Gansu, Qinghai and northwestern Inner Mongolia and other frontier areas. These areas are classified as severe cold and cold regions in building thermal design zoning, and the energy efficiency of urban buildings mainly emphasizes thermal isolation in winter, while the guidance of passive cooling design in summer is urgently needed. Differently, the local vernacular buildings show climate adaptability, and the shading strategies were used to adjust indoor and outdoor thermal environments, the formed unique passive cooling mode needs to be inherited and developed urgently. For the reason, the Turpan vernacular buildings in extreme arid climate were taken as an example, based on field investigation, the shading objects such as streets, courtyards, roofs, walls and windows, and the shading methods such as grape drying rooms, Ayiwang, elevated trellis, canopies, gable porches, grapevine shelves, permeable walls, and lattice windows were summarized. In addition, through the method of field tests and thermal simulations, a thermal shiledling model for Turpan vernacular buildings was established based on EnergyPlus and its effectiveness was verified. On the basis, the orthogonal test method was applied to evaluate the thermal energy-saving effects of four types of shading objects. The order of thermal shielding effect from large to small was courtyard shading, roof shading, wall shading and window shading, and the best combination of their shading area levels was obtained, i.e., roof shading 100%, wall shading 100%, window shading 25%. Furthermore, according to the existing feasible shading types, the roof grape-drying room and software elevated trellis were recommended as the comprehensive shading for the roof, courtyard, wall and window. Taking the differences in shading needs in different seasons into account, the elevated trellis should apply light-weight construction or grapevine planting method, which was easy to remove in winter.
The arid climate of China is mainly distributed in the southern part of Xinjiang, Gansu, Qinghai and northwestern Inner Mongolia and other frontier areas. These areas are classified as severe cold and cold regions in building thermal design zoning, and the energy efficiency of urban buildings mainly emphasizes thermal isolation in winter, while the guidance of passive cooling design in summer is urgently needed. Differently, the local vernacular buildings show climate adaptability, and the shading strategies were used to adjust indoor and outdoor thermal environments, the formed unique passive cooling mode needs to be inherited and developed urgently. For the reason, the Turpan vernacular buildings in extreme arid climate were taken as an example, based on field investigation, the shading objects such as streets, courtyards, roofs, walls and windows, and the shading methods such as grape drying rooms, Ayiwang, elevated trellis, canopies, gable porches, grapevine shelves, permeable walls, and lattice windows were summarized. In addition, through the method of field tests and thermal simulations, a thermal shiledling model for Turpan vernacular buildings was established based on EnergyPlus and its effectiveness was verified. On the basis, the orthogonal test method was applied to evaluate the thermal energy-saving effects of four types of shading objects. The order of thermal shielding effect from large to small was courtyard shading, roof shading, wall shading and window shading, and the best combination of their shading area levels was obtained, i.e., roof shading 100%, wall shading 100%, window shading 25%. Furthermore, according to the existing feasible shading types, the roof grape-drying room and software elevated trellis were recommended as the comprehensive shading for the roof, courtyard, wall and window. Taking the differences in shading needs in different seasons into account, the elevated trellis should apply light-weight construction or grapevine planting method, which was easy to remove in winter.
2023, 53(7): 16-24,78.
doi: 10.13204/j.gyjzG22120509
Abstract:
At present, the nearly zero energy consumption building is showing the trend of scale promotion in China, and the design and evaluation standards from the national to the local have been gradually improving, and most of the standards limit the value of energy-saving design parameters to achieve the goal of near-zero energy consumption. However, office buildings have diverse demands for energy consumption and complex structure of energy consumption, so it is necessary to comprehensively optimize the energy-saving design parameters to achieve the design goal of energy consumption minimization. Based on this, the paper firstly constructed the base model of energy consumption composition and building information for the office buildings in cold regions through investigation, and constructed a parameterized integrated platform with model construction, energy consumption simulation and automatic optimization through grasshopper; secondly, a comparative study of office buildings with different thermal design parameters of building envelopes was conducted, and the importance of lighting energy consumption and the influence law of total energy consumption by multi-parameter interaction with this platform was determined; then, on this basis, the paper optimized the energy consumption-oriented design parameters by genetic algorithm, and the optimal results were obtained; thirdly, with the Comprehensive Lab Building of Shandong Jianzhu University as an example, the paper verified the reliability and accuracy of the research results by comparing the measured data with the simulation data; finally, a correlation analysis of design parameters and energy consumption results was conducted by data statistics software, and a machine learning model was established by training data sets in MATLAB, thus verifying the accuracy of the model.
At present, the nearly zero energy consumption building is showing the trend of scale promotion in China, and the design and evaluation standards from the national to the local have been gradually improving, and most of the standards limit the value of energy-saving design parameters to achieve the goal of near-zero energy consumption. However, office buildings have diverse demands for energy consumption and complex structure of energy consumption, so it is necessary to comprehensively optimize the energy-saving design parameters to achieve the design goal of energy consumption minimization. Based on this, the paper firstly constructed the base model of energy consumption composition and building information for the office buildings in cold regions through investigation, and constructed a parameterized integrated platform with model construction, energy consumption simulation and automatic optimization through grasshopper; secondly, a comparative study of office buildings with different thermal design parameters of building envelopes was conducted, and the importance of lighting energy consumption and the influence law of total energy consumption by multi-parameter interaction with this platform was determined; then, on this basis, the paper optimized the energy consumption-oriented design parameters by genetic algorithm, and the optimal results were obtained; thirdly, with the Comprehensive Lab Building of Shandong Jianzhu University as an example, the paper verified the reliability and accuracy of the research results by comparing the measured data with the simulation data; finally, a correlation analysis of design parameters and energy consumption results was conducted by data statistics software, and a machine learning model was established by training data sets in MATLAB, thus verifying the accuracy of the model.
2023, 53(7): 25-31.
doi: 10.13204/j.gyjzG21081814
Abstract:
Integrated design is a design strategy based on the relevance between space and functions, which can fully stimulate the new needs and development of buildings. Taking Hohhot Dayao Headquarters Base as an example, the application of integrated strategies in the green design of the reception center was studied and analyzed, from the aspects of functional integration, spatial integration and green technology to explore the contribution of integrated strategies to green building design. The concept of integration could effectively improve the green performance of buildings and create architectural forms that conformed to regional characteristics and met the requirements of the times, so as to achieve higher green building design goals.
Integrated design is a design strategy based on the relevance between space and functions, which can fully stimulate the new needs and development of buildings. Taking Hohhot Dayao Headquarters Base as an example, the application of integrated strategies in the green design of the reception center was studied and analyzed, from the aspects of functional integration, spatial integration and green technology to explore the contribution of integrated strategies to green building design. The concept of integration could effectively improve the green performance of buildings and create architectural forms that conformed to regional characteristics and met the requirements of the times, so as to achieve higher green building design goals.
2023, 53(7): 32-42,101.
doi: 10.13204/j.gyjzG22050606
Abstract:
The influence of minimalist art on the design field is profound. Element restoration is one of its main means. Through substantive evideuce analysis and philosophically and logically mental analysis, three kinds of element restoration phenomena in contemporary architecture design and urban planning were analyzed deeply, which were aesthetic styles, operational strategies and urban management modes. And its internal mechanisms and common features were deeply anatomized and refined, it could be summarized into four aspects, that was purified structure, self-disciplined space, integrated technology and intuitive conception. Based on that opinion, a restoration methodology of essentialization and materialization was discussed, which would be a framework design program, spatial system and formal language of openness and generation oriented towards possibilities, with basic relation construction as the core. Finally, combined with local practices, the theory be verified. The exploration aimed to return to its roots, improved and expanded the core and boundaries of the planning and design disciplines.
The influence of minimalist art on the design field is profound. Element restoration is one of its main means. Through substantive evideuce analysis and philosophically and logically mental analysis, three kinds of element restoration phenomena in contemporary architecture design and urban planning were analyzed deeply, which were aesthetic styles, operational strategies and urban management modes. And its internal mechanisms and common features were deeply anatomized and refined, it could be summarized into four aspects, that was purified structure, self-disciplined space, integrated technology and intuitive conception. Based on that opinion, a restoration methodology of essentialization and materialization was discussed, which would be a framework design program, spatial system and formal language of openness and generation oriented towards possibilities, with basic relation construction as the core. Finally, combined with local practices, the theory be verified. The exploration aimed to return to its roots, improved and expanded the core and boundaries of the planning and design disciplines.
2023, 53(7): 43-51,63.
doi: 10.13204/j.gyjzG22092204
Abstract:
As China's urban construction gradually develops from incremental expansion to stock renewal, the renewal and reuse of existing industrial heritage areas has become an important topic of China's urban development. Taking the industrial heritage district of Zhengzhou No.2 Grinding Wheel Factory as the main research object, using the theory of space syntax, from the five aspects of integration degree, coordination, comprehensibility, connectivity value, and selectiveness, a quantification research on the space of Zhengzhou No.2 Grinding Wheel Factory at both macro and mioro scale was conducted combined with heat maps; simultaneously, the vitality degrees of the space before and after the renovation were compared. It was found that there were some problems such as remote geographical location, lack of internal commercial system and low accessibility of internal roads in the Industrial Cultural and Creative Park, and corresponding spatial renewal strategies were put forward, which could provide a reference for the space protection and redevelopment of Zhengzhou No.2 Granding Wheel Factory's industrial heritage areas and similar industrial heritage areas.
As China's urban construction gradually develops from incremental expansion to stock renewal, the renewal and reuse of existing industrial heritage areas has become an important topic of China's urban development. Taking the industrial heritage district of Zhengzhou No.2 Grinding Wheel Factory as the main research object, using the theory of space syntax, from the five aspects of integration degree, coordination, comprehensibility, connectivity value, and selectiveness, a quantification research on the space of Zhengzhou No.2 Grinding Wheel Factory at both macro and mioro scale was conducted combined with heat maps; simultaneously, the vitality degrees of the space before and after the renovation were compared. It was found that there were some problems such as remote geographical location, lack of internal commercial system and low accessibility of internal roads in the Industrial Cultural and Creative Park, and corresponding spatial renewal strategies were put forward, which could provide a reference for the space protection and redevelopment of Zhengzhou No.2 Granding Wheel Factory's industrial heritage areas and similar industrial heritage areas.
2023, 53(7): 52-63.
doi: 10.13204/j.gyjzG22062901
Abstract:
During the 14th Five-Year Plan of China, the transformation of the prefabricated construction mode of smart primary and secondary schools is driven by double carbon strategy, the prefabricated classroom design modulus is the core issues of industrialization and smartization. By analyzing the teaching and spatial mode of the teaching unit of smart schools, the functional modules of the smart classroom that meet the variability of the information teaching and teaching mode can be proposed. To meet the goal of the principle of prefabricated modulus coordination, through the establishment of models and data statistics, the most adaptable high-frequency size corresponding modulus were obtained, the workflow optimal modulus were established to promote the architect's subjective decision-making modulus, improve the standardization degree of prefabricated smart classrooms, and achieve the organic integration of standardization and personalization, a BIM department family library was established based on the optimized modulus, a new construction mode of building industrialization for smart primary and secondary school buildings was formed.
During the 14th Five-Year Plan of China, the transformation of the prefabricated construction mode of smart primary and secondary schools is driven by double carbon strategy, the prefabricated classroom design modulus is the core issues of industrialization and smartization. By analyzing the teaching and spatial mode of the teaching unit of smart schools, the functional modules of the smart classroom that meet the variability of the information teaching and teaching mode can be proposed. To meet the goal of the principle of prefabricated modulus coordination, through the establishment of models and data statistics, the most adaptable high-frequency size corresponding modulus were obtained, the workflow optimal modulus were established to promote the architect's subjective decision-making modulus, improve the standardization degree of prefabricated smart classrooms, and achieve the organic integration of standardization and personalization, a BIM department family library was established based on the optimized modulus, a new construction mode of building industrialization for smart primary and secondary school buildings was formed.
2023, 53(7): 64-73.
doi: 10.13204/j.gyjzG22060804
Abstract:
Taking Jinjiang Timber Cabin Village, a traditional village in cold regions of northern establish China, as the research object. The research method of pattern language was used to identify and deconstruct the traditional villages' public space elements, and the landscape language system of Jinjiang Timber Cabin Village. By studying the scale, order and semantics of public space, the paper summarized and extracted 35 kinds of "characters",16 kinds of "words" and 5 kinds of "phrases", which constituted landscape spatial schema, and constructed the local and adaptive landscape schema language system and schema prototype database of Jinjiang Timber Cabin Village. On this basis, from the aspects of multi-level landscape framework and pattern language application, design vocabularies were selected from the pattern language system, the basement environment and landscape functions were matched, so as to guide the planning and design and optimize the reconstruction of tradition village public space, and provide a reference for the protection and sustainable development of traditional villages in the northern cold regions.
Taking Jinjiang Timber Cabin Village, a traditional village in cold regions of northern establish China, as the research object. The research method of pattern language was used to identify and deconstruct the traditional villages' public space elements, and the landscape language system of Jinjiang Timber Cabin Village. By studying the scale, order and semantics of public space, the paper summarized and extracted 35 kinds of "characters",16 kinds of "words" and 5 kinds of "phrases", which constituted landscape spatial schema, and constructed the local and adaptive landscape schema language system and schema prototype database of Jinjiang Timber Cabin Village. On this basis, from the aspects of multi-level landscape framework and pattern language application, design vocabularies were selected from the pattern language system, the basement environment and landscape functions were matched, so as to guide the planning and design and optimize the reconstruction of tradition village public space, and provide a reference for the protection and sustainable development of traditional villages in the northern cold regions.
2023, 53(7): 74-78.
doi: 10.13204/j.gyjzG21011506
Abstract:
The flange joint connected by corrugated welding lines has been gradually applied in engineering because of its high bearing capacity and excellent mechanical properties. In order to analyze the bearing capacity mechanism of the flange joint connected by corrugated welding lines, firstly, thd paper analyzed the influence law of the effective length of weld on the bearing capacity of the joint by using the method of theoretical calculation, and a comparison analysis was conducted with the flat welded flange joint with neck. Then, the parametric modeling was carried out by means of finite element to find out the optimal waveform of the joint and calculate its bearing capacity. Finally, the axial compression and axial tension tests of four flange joints connected by corrugated welding lines and four flat welded flange joints with necks were carried out, and the influence of welding heat on the reduction of bearing capacity of joints in axial tension test was discussed. The results showed that the bearing capacity of the flange joint connected by corrugated welding lines could be improved by increasing the effective length of the weld compared with the flat welded flange joint with neck; corrugated welding lines could stagger weld defects and welding heat affected zone from the same section, reduce local stress concentration,so as to improve bearing capacity.
The flange joint connected by corrugated welding lines has been gradually applied in engineering because of its high bearing capacity and excellent mechanical properties. In order to analyze the bearing capacity mechanism of the flange joint connected by corrugated welding lines, firstly, thd paper analyzed the influence law of the effective length of weld on the bearing capacity of the joint by using the method of theoretical calculation, and a comparison analysis was conducted with the flat welded flange joint with neck. Then, the parametric modeling was carried out by means of finite element to find out the optimal waveform of the joint and calculate its bearing capacity. Finally, the axial compression and axial tension tests of four flange joints connected by corrugated welding lines and four flat welded flange joints with necks were carried out, and the influence of welding heat on the reduction of bearing capacity of joints in axial tension test was discussed. The results showed that the bearing capacity of the flange joint connected by corrugated welding lines could be improved by increasing the effective length of the weld compared with the flat welded flange joint with neck; corrugated welding lines could stagger weld defects and welding heat affected zone from the same section, reduce local stress concentration,so as to improve bearing capacity.
2023, 53(7): 79-83.
doi: 10.13204/j.gyjzG21062206
Abstract:
In order to study the effect of different arrangement and connection modes of vertical diagonal tie rods on the three-dimension warehouse shelf structures under static loads and earthquake action, three dimension element models vertical diagonal tie rods were established to study the variation laws of stress and displacement which arranged with double-row and single-layer diagonal rods, double-row and double-layer diagooal rods, and not arranged diagnoal rods, and different connection modes including rigidity and semi-rigidity connections. The calculation results showed that, under the action of earthquake, the arrangement of vertically diagnoal tie rods had a significant effect on the displacement and maximum stress of members. The comparison between static loads and earthquake action showed that the effect of the double-row and double-layer arrangement of vertical diagonal tie rods on the structural deformation was better than that of the double-row and single-layer arrangement. Compared with the rigid connection, the semi-rigid connection could obviously reduce the stress of members.
In order to study the effect of different arrangement and connection modes of vertical diagonal tie rods on the three-dimension warehouse shelf structures under static loads and earthquake action, three dimension element models vertical diagonal tie rods were established to study the variation laws of stress and displacement which arranged with double-row and single-layer diagonal rods, double-row and double-layer diagooal rods, and not arranged diagnoal rods, and different connection modes including rigidity and semi-rigidity connections. The calculation results showed that, under the action of earthquake, the arrangement of vertically diagnoal tie rods had a significant effect on the displacement and maximum stress of members. The comparison between static loads and earthquake action showed that the effect of the double-row and double-layer arrangement of vertical diagonal tie rods on the structural deformation was better than that of the double-row and single-layer arrangement. Compared with the rigid connection, the semi-rigid connection could obviously reduce the stress of members.
2023, 53(7): 84-92,108.
doi: 10.13204/j.gyjzG21010415
Abstract:
Heavy silo is one of the most common equipment in industrial structures. A structure of elevated steel silo was focused. Two numerical models were developed in which one simplified the silo equipment as loadings and the other one modelled the whole equipment-structure system. A total of 18 pairs of ground motions were selected. Linear and nonlinear response-history analysis as well as incremental dynamic analysis were performed. The dynamic responses of the two structural numerical models and the linear and nonlinear floor response spectrum were obtained accordingly. Subsequently, nonlinear floor response spectrum was used as input for response analysis of the heavy silo equipment. The seismic responses of the heavy silo equipment were compared between the results from the floor response spectrum analysis based on the single silo equipment model and the response-history analysis based on the equipment-structure model. The effectiveness of the nonlinear floor response spectrum method in the seismic design of the heavy silo equipment was examined. The results showed that the extent of the nonlinearity sustained by the structure would alter the shape of the floor response spectrum. The input seismic intensity was found to be influential to the interaction between equipment and structure. The seismic design of the heavy silo would be conservative if considering the floor response spectrum derived from the equipment-structure model.
Heavy silo is one of the most common equipment in industrial structures. A structure of elevated steel silo was focused. Two numerical models were developed in which one simplified the silo equipment as loadings and the other one modelled the whole equipment-structure system. A total of 18 pairs of ground motions were selected. Linear and nonlinear response-history analysis as well as incremental dynamic analysis were performed. The dynamic responses of the two structural numerical models and the linear and nonlinear floor response spectrum were obtained accordingly. Subsequently, nonlinear floor response spectrum was used as input for response analysis of the heavy silo equipment. The seismic responses of the heavy silo equipment were compared between the results from the floor response spectrum analysis based on the single silo equipment model and the response-history analysis based on the equipment-structure model. The effectiveness of the nonlinear floor response spectrum method in the seismic design of the heavy silo equipment was examined. The results showed that the extent of the nonlinearity sustained by the structure would alter the shape of the floor response spectrum. The input seismic intensity was found to be influential to the interaction between equipment and structure. The seismic design of the heavy silo would be conservative if considering the floor response spectrum derived from the equipment-structure model.
2023, 53(7): 93-101.
doi: 10.13204/j.gyjzG21022509
Abstract:
To research the seismic perfomance of concrete-filled thin-walled high-strength steel tubular (CFTHST) columns, a quasi-static test was conducted on concrete-filled thin-walled high-strength Q690 steel tubular columns with diameter-to-thickness (D/t) ratios exceeding regulation limitations. The detailed analysis was performed to examine the failure mode, load-displacement curves, hysteretic energy dissipation, and the degradation laws of stiffness and bearing capacity; subsequently, a finite element damage model of CFTHST column was established based on the dependent fracture criterion of steel stress triaxiality to reveal the damage evolution. The results indicated that:the tested HCFTST columns failed in a way of concrete crushing combined with the local buckling and fracture of high-strength (HS) steel tube; in the drift ratios of 1% to 6%, the load ratios maintained above 0.9 while the load degradation reached up 17.4% to 23.0% in the drift ratios of 7% to 8%; moreover, the tested columns behaved the plump hysteresis curves with the ductility coefficients in the range of 2.88 to 3.61, reflecting that those columns demonstrated a reasonable bearing capacity and plastic deformation; the concrete damage area appeared in V-shaped distribution and the HS steel tube experienced a deep yielding behavior; increasing the axial compression ratio and D/t ratio augmented the fracture damage of the CFTHST columns.
To research the seismic perfomance of concrete-filled thin-walled high-strength steel tubular (CFTHST) columns, a quasi-static test was conducted on concrete-filled thin-walled high-strength Q690 steel tubular columns with diameter-to-thickness (D/t) ratios exceeding regulation limitations. The detailed analysis was performed to examine the failure mode, load-displacement curves, hysteretic energy dissipation, and the degradation laws of stiffness and bearing capacity; subsequently, a finite element damage model of CFTHST column was established based on the dependent fracture criterion of steel stress triaxiality to reveal the damage evolution. The results indicated that:the tested HCFTST columns failed in a way of concrete crushing combined with the local buckling and fracture of high-strength (HS) steel tube; in the drift ratios of 1% to 6%, the load ratios maintained above 0.9 while the load degradation reached up 17.4% to 23.0% in the drift ratios of 7% to 8%; moreover, the tested columns behaved the plump hysteresis curves with the ductility coefficients in the range of 2.88 to 3.61, reflecting that those columns demonstrated a reasonable bearing capacity and plastic deformation; the concrete damage area appeared in V-shaped distribution and the HS steel tube experienced a deep yielding behavior; increasing the axial compression ratio and D/t ratio augmented the fracture damage of the CFTHST columns.
2023, 53(7): 102-108.
doi: 10.13204/j.gyjzG22032703
Abstract:
In order to improve the mechanical properties of cold-formed thin-walled steel (CFS) walls under axial compression, a new structural measure of infilling phosphogypsum in CFS walls was proposed. 4 full-scale test specimens were designed and fabricated with consideration of the phosphogypsum filled area and the measures with or without sheathings. Through axial loading tests, the failure process of the specimens was described, and the failure mode, axial force versus displacement curve, strain curve and bearing capacity of all specimens were analyzed. The test results indicated that the main failures of the specimens were the local crushing of the square steel tube wall studs, the tearing of the wall sheathings, the crushing of the infilled phosphogypsum, the distortion of the tracks, etc. Compared with the hollow section specimen, the bearing capacity of the specimen with phosphogypsum only filled in the steel tubes was increased by 37.4%. For the specimen with phosphogypsum filled in steel tubes and phosphogypsum filled in the area between studs, the bearing capacity was increased by 115.7%, indicating that the infilled phosphogypsum could effectively improve the axial load bearing capacity of the CFS wall. The comparison of specimens with and without sheathings showed that the wall sheathing had a slight influence on the axial load bearing capacity. In addition, formulas for calculating the axial load bearing capacity of the walls was also proposed in the paper. The verification results showed that the formulas had good calculation accuracy.
In order to improve the mechanical properties of cold-formed thin-walled steel (CFS) walls under axial compression, a new structural measure of infilling phosphogypsum in CFS walls was proposed. 4 full-scale test specimens were designed and fabricated with consideration of the phosphogypsum filled area and the measures with or without sheathings. Through axial loading tests, the failure process of the specimens was described, and the failure mode, axial force versus displacement curve, strain curve and bearing capacity of all specimens were analyzed. The test results indicated that the main failures of the specimens were the local crushing of the square steel tube wall studs, the tearing of the wall sheathings, the crushing of the infilled phosphogypsum, the distortion of the tracks, etc. Compared with the hollow section specimen, the bearing capacity of the specimen with phosphogypsum only filled in the steel tubes was increased by 37.4%. For the specimen with phosphogypsum filled in steel tubes and phosphogypsum filled in the area between studs, the bearing capacity was increased by 115.7%, indicating that the infilled phosphogypsum could effectively improve the axial load bearing capacity of the CFS wall. The comparison of specimens with and without sheathings showed that the wall sheathing had a slight influence on the axial load bearing capacity. In addition, formulas for calculating the axial load bearing capacity of the walls was also proposed in the paper. The verification results showed that the formulas had good calculation accuracy.
2023, 53(7): 109-115,230.
doi: 10.13204/j.gyjzG22040112
Abstract:
Tests of 10 concrete-filled thin-walled square steel tubular columns under axial compression were conducted, the influence of slenderness ratio, wall thickness and concrete strength on the failure pattern, load-displacement curve, ultimate bearing capacity and Poisson's ratio of the specimens were studied. The results showed that the loading process of concrete-filled thin-walled steel tubular column was similar to that of ordinary concrete-filled steel tubular cloumn. Generally, it could be divided into three stages:elastic stage, elastic-plastic stage and descending stage. The failure of the specimens in the test was that the core concrete was crushed and there was a circumferential buckling band outside the steel pipe. The finite element software was used to establish the model of concrete-filled thin-walled steel tubular column and verify its effectiveness and reliability. The analysis results showed that when the steel ratio of member section was certain, the influence of concrete strength on the combination effect of steel-concrete structure was very obvious. For thin-walled members with steel ratio of 0.02 to 0.06, the combination efficiency of steel-concrete structure could be improved by using concrete with strength grade of C20 to C50.For the stability bearing capacity, it was found that the stability coefficient under different variation parameters could be expressed by a single equation with the regular slenderness ratio as the independent variable. Finally, referring to Technical Code for Concrete Filled Steel Tubular Structures(GB 50936-2014), a simplified calculation formula for the axial compressive bearing capacity of concrete-filled thin-walled square steel tubular columns was proposed, and the calculated values were in good agreement with the measured values.
Tests of 10 concrete-filled thin-walled square steel tubular columns under axial compression were conducted, the influence of slenderness ratio, wall thickness and concrete strength on the failure pattern, load-displacement curve, ultimate bearing capacity and Poisson's ratio of the specimens were studied. The results showed that the loading process of concrete-filled thin-walled steel tubular column was similar to that of ordinary concrete-filled steel tubular cloumn. Generally, it could be divided into three stages:elastic stage, elastic-plastic stage and descending stage. The failure of the specimens in the test was that the core concrete was crushed and there was a circumferential buckling band outside the steel pipe. The finite element software was used to establish the model of concrete-filled thin-walled steel tubular column and verify its effectiveness and reliability. The analysis results showed that when the steel ratio of member section was certain, the influence of concrete strength on the combination effect of steel-concrete structure was very obvious. For thin-walled members with steel ratio of 0.02 to 0.06, the combination efficiency of steel-concrete structure could be improved by using concrete with strength grade of C20 to C50.For the stability bearing capacity, it was found that the stability coefficient under different variation parameters could be expressed by a single equation with the regular slenderness ratio as the independent variable. Finally, referring to Technical Code for Concrete Filled Steel Tubular Structures(GB 50936-2014), a simplified calculation formula for the axial compressive bearing capacity of concrete-filled thin-walled square steel tubular columns was proposed, and the calculated values were in good agreement with the measured values.
2023, 53(7): 116-123,179.
doi: 10.13204/j.gyjzG23030712
Abstract:
When L-shaped steel-reinforced concrete (SRC) rectangular columns are applied as corner columns in high-rise buildings, the problems of indirect force transmission and stress concentration caused by the discontinuity of T-shaped steel reinforced concrete columns can be avoided. In order to reveal the mechanical properties of L-shaped SRC columns under eccentric compression, five L-shaped SRC rectangular columns and one T-shaped SRC rectangular column with different load eccentricity, slenderness ratio and different steel distribution, respectively. All these specimens were tested under eccentric compression. The results showed that L-shaped steel developed crack asymmetrically under the non-uniform constraint of concrete; at the same cross-section height, the reinforcement and steel in the tension and compression zone of L-shaped steel SRC column did not yield concurrently. However, the steel asymmetry does not significantly reduce the bearing capacity and ductility of the specimens. Based on the experimental study, a finite element model was established to analyze the effects of eccentricity, slenderness ratio and web eccentricity on the mechanical properties of L-shaped steel SRC columns under eccentric compression. The model analysis showed that the boundary of the tension and compression zones of L-shaped steel SRC columns was an oblique line. However, because the slope was small and the bearing capacity of the specimen was not significantly different from that of T-shaped steel, the relative height of the compression zone could be simplified as a straight line in the design of the component section. Based on the analysis of finite element model under various working conditions, the paper suggested that the value of load eccentricity about 0.45 should be the preliminary criterion for the size bias in the design of component.
When L-shaped steel-reinforced concrete (SRC) rectangular columns are applied as corner columns in high-rise buildings, the problems of indirect force transmission and stress concentration caused by the discontinuity of T-shaped steel reinforced concrete columns can be avoided. In order to reveal the mechanical properties of L-shaped SRC columns under eccentric compression, five L-shaped SRC rectangular columns and one T-shaped SRC rectangular column with different load eccentricity, slenderness ratio and different steel distribution, respectively. All these specimens were tested under eccentric compression. The results showed that L-shaped steel developed crack asymmetrically under the non-uniform constraint of concrete; at the same cross-section height, the reinforcement and steel in the tension and compression zone of L-shaped steel SRC column did not yield concurrently. However, the steel asymmetry does not significantly reduce the bearing capacity and ductility of the specimens. Based on the experimental study, a finite element model was established to analyze the effects of eccentricity, slenderness ratio and web eccentricity on the mechanical properties of L-shaped steel SRC columns under eccentric compression. The model analysis showed that the boundary of the tension and compression zones of L-shaped steel SRC columns was an oblique line. However, because the slope was small and the bearing capacity of the specimen was not significantly different from that of T-shaped steel, the relative height of the compression zone could be simplified as a straight line in the design of the component section. Based on the analysis of finite element model under various working conditions, the paper suggested that the value of load eccentricity about 0.45 should be the preliminary criterion for the size bias in the design of component.
2023, 53(7): 124-129.
doi: 10.13204/j.gyjzG22072212
Abstract:
In order to strengthen the interfacial bonding effect of long-span steel-concrete composite beams, a cross-shaped perfobond strips (PBL) was proposed based on the actual engineering structure.The push-out tests of 1 set of stud strips and 3 sets of cross-shaped PBLs were conducted.The failure modes and load-displacement curves of strips were studied.The results showed that the shear strength of cross-shaped PBL with similar cross-section areas was much higher than that of stud strips.The cross-section width and concrete strength grade had the greatest influence on the shear performance of cross-shaped PBLs.The shear capacity of cross-shaped PBLs increased with the increase of the thickness of perfobond strips.The shear stiffness increased with the increase of strip height.
In order to strengthen the interfacial bonding effect of long-span steel-concrete composite beams, a cross-shaped perfobond strips (PBL) was proposed based on the actual engineering structure.The push-out tests of 1 set of stud strips and 3 sets of cross-shaped PBLs were conducted.The failure modes and load-displacement curves of strips were studied.The results showed that the shear strength of cross-shaped PBL with similar cross-section areas was much higher than that of stud strips.The cross-section width and concrete strength grade had the greatest influence on the shear performance of cross-shaped PBLs.The shear capacity of cross-shaped PBLs increased with the increase of the thickness of perfobond strips.The shear stiffness increased with the increase of strip height.
2023, 53(7): 130-138,146.
doi: 10.13204/j.gyjzG22080605
Abstract:
The number of asymmetrical joints in complex long-span buildings is gradually increasing. The asymmetry is mainly reflected in different component sizes and different steel ratios. Compared with conventional symmetrical joints, there are many differences in the force transmission mechanism, failure mode and bearing properties of asymmetrical joints, so the design cannot be completely based on the calculation method of the existing conventional joints. Based on this, taking the asymmetric joints of a project in China as an example, ABAQUS software was used to conduct three-dimensional modeling. The seismic performance characteristics of asymmetric joints were analyzed through the hysteresis curve, skeleton curve, stress and damage distribution of joints, and the peak load at this time was taken as the seismic performance standard for subsequent optimization. Using the artifical bee colony algorithm, with the interface size and profile steel size as the input conditions, the seismic performance as the boundary condition, and the economy as the objective function, the secondary development of ABAQUS based on the Python language was carried out, and the optimal interface size and content were automatically calculated. The combination of steel ratio realized the optimal design of asymmetric joints. The research results could improve the level of refinement and intelligence in architectural design.
The number of asymmetrical joints in complex long-span buildings is gradually increasing. The asymmetry is mainly reflected in different component sizes and different steel ratios. Compared with conventional symmetrical joints, there are many differences in the force transmission mechanism, failure mode and bearing properties of asymmetrical joints, so the design cannot be completely based on the calculation method of the existing conventional joints. Based on this, taking the asymmetric joints of a project in China as an example, ABAQUS software was used to conduct three-dimensional modeling. The seismic performance characteristics of asymmetric joints were analyzed through the hysteresis curve, skeleton curve, stress and damage distribution of joints, and the peak load at this time was taken as the seismic performance standard for subsequent optimization. Using the artifical bee colony algorithm, with the interface size and profile steel size as the input conditions, the seismic performance as the boundary condition, and the economy as the objective function, the secondary development of ABAQUS based on the Python language was carried out, and the optimal interface size and content were automatically calculated. The combination of steel ratio realized the optimal design of asymmetric joints. The research results could improve the level of refinement and intelligence in architectural design.
2023, 53(7): 139-146.
doi: 10.13204/j.gyjzG22090514
Abstract:
In order to investigate the seismic performance of the steel-concrete composite structure subway station, based on Daikai Station, which was seriously damaged in the Hanshin earthquake in 1995, the seismic damage response of the reinforced concrete subway station in the Hanshin earthquake was first simulated and analyzed by using the ABAQUS software, and then compared with the actual damage phenomenon of Daikai Station to verify the accuracy and reliability of the finite element model. Under the assumption that all other parameters remained constant, Daikai Station's central column, roof, and beam were substituted with steel-concrete composite members, and two distinct composite structure subway station finite element models were established. The inter-storey drift angle of the side wall and the horizontal displacement time-history curve of the central column and other indicators were compared with the seismic damage simulation findings of Daikai Station, and the seismic performance difference of the subway station under different structural forms was investigated. The results showed that the subway station construction with solely concrete-filled steel tubular columns had the best seismic performance, with the horizontal displacement of the central column being around 21% less than the other two structures; at the peak acceleration moment, the inter-story displacement angle of the side wall was about 25% to 28% smaller than that of the steel-concrete composite structure and approximately 12% to 13% smaller than that of Daikai Station's structure.
In order to investigate the seismic performance of the steel-concrete composite structure subway station, based on Daikai Station, which was seriously damaged in the Hanshin earthquake in 1995, the seismic damage response of the reinforced concrete subway station in the Hanshin earthquake was first simulated and analyzed by using the ABAQUS software, and then compared with the actual damage phenomenon of Daikai Station to verify the accuracy and reliability of the finite element model. Under the assumption that all other parameters remained constant, Daikai Station's central column, roof, and beam were substituted with steel-concrete composite members, and two distinct composite structure subway station finite element models were established. The inter-storey drift angle of the side wall and the horizontal displacement time-history curve of the central column and other indicators were compared with the seismic damage simulation findings of Daikai Station, and the seismic performance difference of the subway station under different structural forms was investigated. The results showed that the subway station construction with solely concrete-filled steel tubular columns had the best seismic performance, with the horizontal displacement of the central column being around 21% less than the other two structures; at the peak acceleration moment, the inter-story displacement angle of the side wall was about 25% to 28% smaller than that of the steel-concrete composite structure and approximately 12% to 13% smaller than that of Daikai Station's structure.
2023, 53(7): 147-156.
doi: 10.13204/j.gyjzG22032813
Abstract:
Hydraulic fracturing can cause instability and failure of rock masses, which is an important reason for inducing rock landslide. The failure process of rock masses caused by hydraulic fracturing was tested with cement mortar specimens and simulated by ABAQUS Software to reveal the hydraulic fracturing mechanism. Taking a rock slope in Letuan-Qingshiguan section of the national road G205 as an example, the landslide occurrence under high groundwater pressure was studied by numerical simulations, and the whole process of slope instability and failure reappeared. The results indicated that when the hydraulic fracturing occured, the water pressure on the fracture plane decreaseed rapidly but cracks were not through the plane, and there was still a little of residual strength for specimens. Combined with numerical simulations, it was confirmed that the hydraulic fracturing of rock masses was quasi-brittle failure, which included static stage, micro-crack propagation stage and macro-crack formation stage. There were three dangerous rock masses in the simulated rock slope, in which WYT3 was unstable in rainstorm and earthquake conditions. The crack developed in three stages under high water head pressure including slow developing, rapid developing, and propagating through stages. The slow development stage lasted longest, and the slope was unstable after the crack propagated through.
Hydraulic fracturing can cause instability and failure of rock masses, which is an important reason for inducing rock landslide. The failure process of rock masses caused by hydraulic fracturing was tested with cement mortar specimens and simulated by ABAQUS Software to reveal the hydraulic fracturing mechanism. Taking a rock slope in Letuan-Qingshiguan section of the national road G205 as an example, the landslide occurrence under high groundwater pressure was studied by numerical simulations, and the whole process of slope instability and failure reappeared. The results indicated that when the hydraulic fracturing occured, the water pressure on the fracture plane decreaseed rapidly but cracks were not through the plane, and there was still a little of residual strength for specimens. Combined with numerical simulations, it was confirmed that the hydraulic fracturing of rock masses was quasi-brittle failure, which included static stage, micro-crack propagation stage and macro-crack formation stage. There were three dangerous rock masses in the simulated rock slope, in which WYT3 was unstable in rainstorm and earthquake conditions. The crack developed in three stages under high water head pressure including slow developing, rapid developing, and propagating through stages. The slow development stage lasted longest, and the slope was unstable after the crack propagated through.
2023, 53(7): 157-161.
doi: 10.13204/j.gyjzG22051111
Abstract:
Based on the global method of stability analysis for stopes, a method to consider the effect of anchor reinforcement on slope stability was proposed, in which anchoring forces were assumed to be borne by the whole sliding body instead of individual slices as a concentrated force,the formula for safety factors of anchored slopes was deduced. As the equilibrium conditions were formulated in terms of the whole slip body instead of individual slices, the internal forces in slopes were more authentic. Simultaneously, three equilibrium equations for moment were formulated according to the global moment equilibrium conditions rather than the traditional equilibrium equations for forces in horizontal and vertical directions and one moment equilibrium equation. Therefore, the method was not only suitable for slopes with slide surfaces with different shapes,but also possessed more excellent numerical properties. Finally,three classical examples were given to prove the effectiveness of the method.
Based on the global method of stability analysis for stopes, a method to consider the effect of anchor reinforcement on slope stability was proposed, in which anchoring forces were assumed to be borne by the whole sliding body instead of individual slices as a concentrated force,the formula for safety factors of anchored slopes was deduced. As the equilibrium conditions were formulated in terms of the whole slip body instead of individual slices, the internal forces in slopes were more authentic. Simultaneously, three equilibrium equations for moment were formulated according to the global moment equilibrium conditions rather than the traditional equilibrium equations for forces in horizontal and vertical directions and one moment equilibrium equation. Therefore, the method was not only suitable for slopes with slide surfaces with different shapes,but also possessed more excellent numerical properties. Finally,three classical examples were given to prove the effectiveness of the method.
2023, 53(7): 162-170.
doi: 10.13204/j.gyjzG22052106
Abstract:
In view of the disadvantages of high construction costs and unfriendly ecology environment for beam-slab raft foundations of wind turbines used in a certain wind farm in Liaoning Province, a novel anchored inverted rib foundation of wind turbines was proposed. Simultaneously, optimized analysis on roofs, ribbed beams, anchor bolts and other members of the foundation was conducted to solve problems such as the local damage at the connection between anchor bolts and foundations. The finite element software ABAQUS was used to verify feasibility of anchored inverted rib foundations for wind turbines by comparing mechanical performances and economy between inverted rib foundations and beam-slab raft foundations. The stress in concrete and rebars, displacement and inclination ratios of inverted rib foundations in extreme load conditions were simulated to determine the optimal selection scheme of anchor inverted rib foundations. The results indicated that against the engineering background of the wind farm, the scheme for anchor inverted rib foundation of 2 MW wind turbines with roofs, 8 ribbed beams and 24 external inclined and internal straight bolts was the optimal scheme, which had a good application prospect.
In view of the disadvantages of high construction costs and unfriendly ecology environment for beam-slab raft foundations of wind turbines used in a certain wind farm in Liaoning Province, a novel anchored inverted rib foundation of wind turbines was proposed. Simultaneously, optimized analysis on roofs, ribbed beams, anchor bolts and other members of the foundation was conducted to solve problems such as the local damage at the connection between anchor bolts and foundations. The finite element software ABAQUS was used to verify feasibility of anchored inverted rib foundations for wind turbines by comparing mechanical performances and economy between inverted rib foundations and beam-slab raft foundations. The stress in concrete and rebars, displacement and inclination ratios of inverted rib foundations in extreme load conditions were simulated to determine the optimal selection scheme of anchor inverted rib foundations. The results indicated that against the engineering background of the wind farm, the scheme for anchor inverted rib foundation of 2 MW wind turbines with roofs, 8 ribbed beams and 24 external inclined and internal straight bolts was the optimal scheme, which had a good application prospect.
2023, 53(7): 171-179.
doi: 10.13204/j.gyjzG22051213
Abstract:
The deformation laws of soil caused by grouting and grouting efficiency with times and space were lack of systematic theoretical research, which hindered the application of grouting in accurate deformation control of proximity construction. Based on the field test, the variation laws of soil deformation and grouting efficiency with time and space were systematically studied by using the numerical simulation method of fluid-solid coupling. Simultaneously, the effects of grouting parameters such as grouting volume, grouting space and grouting depth on soil deformation and grouting efficiency were considered. And based on the study, some suggestions on grouting deformation control were put forward. The study indicated that when it was necessary to control subsidence of the ground or tunnels, it was suggested that the top of the grouted body should be flush with the target object. When it was necessary to control heave of the ground or tunnels, it was recommended that the bottom of the grouted body be flush with the target object. With the increase of grouting space, the horizontal and vertical displacement of soil and the grouting efficiency of horizontal displacement decreased rapidly. In order to ensure the deformation effect caused by grouting, the grouting distance should be not to long.
The deformation laws of soil caused by grouting and grouting efficiency with times and space were lack of systematic theoretical research, which hindered the application of grouting in accurate deformation control of proximity construction. Based on the field test, the variation laws of soil deformation and grouting efficiency with time and space were systematically studied by using the numerical simulation method of fluid-solid coupling. Simultaneously, the effects of grouting parameters such as grouting volume, grouting space and grouting depth on soil deformation and grouting efficiency were considered. And based on the study, some suggestions on grouting deformation control were put forward. The study indicated that when it was necessary to control subsidence of the ground or tunnels, it was suggested that the top of the grouted body should be flush with the target object. When it was necessary to control heave of the ground or tunnels, it was recommended that the bottom of the grouted body be flush with the target object. With the increase of grouting space, the horizontal and vertical displacement of soil and the grouting efficiency of horizontal displacement decreased rapidly. In order to ensure the deformation effect caused by grouting, the grouting distance should be not to long.
2023, 53(7): 180-188,170.
doi: 10.13204/j.gyjzG21112803
Abstract:
Against the background of prefabricated concrete linings of tunnels in a tram project, to study the influence of interfacial treatment ways on flexural performances of transverse connections of the tunnel, four-point loading flexural tests were conducted on three specimens treated with epoxy resin, non-shrinkage mortar and without any treatment respectively. The experimental results indicated that the opening at connections varied linearly along height of specimens, whether the interfaces be treated has little effect on the ultimate bearing capacity of specimens. In the standard combination, basic combination, frequent seismic combination, fortification seismic combination and rare seismic combination, the transverse connections of tunnels did not reach the cracking moment, and still had a large safety margin. The ductility of the specimen without any treatment was best. But after unloading, the residual deformation of the specimen treated with non-shrinkage mortar was smallest, and the restorability was best. The flexural stiffness of connections simulated by the three line-segment model could better fit the moment-rotation curve, but it could not reflect the nonlinear characteristics at the deformation development stage of specimens, the theoretical moment-angle curves were basically consistent with the experimental moment-rotation curves, and the flexural stiffness of specimens filled with non-shrinkage mortar was best. Comprehensively considering all factors, it was a better choice not to treat on interfaces of connections in practical engineering.
Against the background of prefabricated concrete linings of tunnels in a tram project, to study the influence of interfacial treatment ways on flexural performances of transverse connections of the tunnel, four-point loading flexural tests were conducted on three specimens treated with epoxy resin, non-shrinkage mortar and without any treatment respectively. The experimental results indicated that the opening at connections varied linearly along height of specimens, whether the interfaces be treated has little effect on the ultimate bearing capacity of specimens. In the standard combination, basic combination, frequent seismic combination, fortification seismic combination and rare seismic combination, the transverse connections of tunnels did not reach the cracking moment, and still had a large safety margin. The ductility of the specimen without any treatment was best. But after unloading, the residual deformation of the specimen treated with non-shrinkage mortar was smallest, and the restorability was best. The flexural stiffness of connections simulated by the three line-segment model could better fit the moment-rotation curve, but it could not reflect the nonlinear characteristics at the deformation development stage of specimens, the theoretical moment-angle curves were basically consistent with the experimental moment-rotation curves, and the flexural stiffness of specimens filled with non-shrinkage mortar was best. Comprehensively considering all factors, it was a better choice not to treat on interfaces of connections in practical engineering.
2023, 53(7): 189-198,6.
doi: 10.13204/j.gyjzG22111001
Abstract:
The effect of recycled coarse aggregate (RCA) replacement ratios, freeze-thaw environments and freeze-thaw cycles on the mechanical properties of self-compacting recycled coarse aggregate concrete (SCRCAC) were studied by rapid freeze-thaw cycle method. The results showed that when the RCA replacement ratios were the same, the compressive strength, splitting tensile strength and uniaxial compressive strength loss ratio of SCRCAC after being subjected to 125 freeze-thaw cycles were the smallest in the freeze-thaw environment of clear water, and the maximum in the 5% mass fraction MgSO4 solution freeze-thaw environment. Sulfate could inhibit freeze-thaw damage at the initial stage of freeze-thaw. At the late stage of freeze-thaw, the relation curves of compressive strength and freeze-thaw cycles of SCRCAC gradually spearated from that curves of ordinary concrete in different freeze-thaw environments and RCA replacement ratios. Based on that, a new relation between the splitting tensile force and the uniaxial compressive force was presented, better predicted the damage and deterioration law of SCRCAC after freeze-thawing of sulfate. The established strength prediction model showed that the model had high accuracy. Grey entropy correlation analysis showed that the effect of freeze-thaw cycles on compressive strength and splitting tensile strength was greater than that of RCA replacement ratios in the freeze-thaw environment of clear water, in the solution of 5% mass fraction of Na2SO4, and in the solution of 5% mass fraction of Na2SO4 and 5% mass fraction of MgSO4. However, contrary to the situation of the solution of 5% mass fraction of MgSO4. The effect of freeze-thaw cycles on the uniaxial compressive strength was larger than the RCA replacement ratio in clear water.
The effect of recycled coarse aggregate (RCA) replacement ratios, freeze-thaw environments and freeze-thaw cycles on the mechanical properties of self-compacting recycled coarse aggregate concrete (SCRCAC) were studied by rapid freeze-thaw cycle method. The results showed that when the RCA replacement ratios were the same, the compressive strength, splitting tensile strength and uniaxial compressive strength loss ratio of SCRCAC after being subjected to 125 freeze-thaw cycles were the smallest in the freeze-thaw environment of clear water, and the maximum in the 5% mass fraction MgSO4 solution freeze-thaw environment. Sulfate could inhibit freeze-thaw damage at the initial stage of freeze-thaw. At the late stage of freeze-thaw, the relation curves of compressive strength and freeze-thaw cycles of SCRCAC gradually spearated from that curves of ordinary concrete in different freeze-thaw environments and RCA replacement ratios. Based on that, a new relation between the splitting tensile force and the uniaxial compressive force was presented, better predicted the damage and deterioration law of SCRCAC after freeze-thawing of sulfate. The established strength prediction model showed that the model had high accuracy. Grey entropy correlation analysis showed that the effect of freeze-thaw cycles on compressive strength and splitting tensile strength was greater than that of RCA replacement ratios in the freeze-thaw environment of clear water, in the solution of 5% mass fraction of Na2SO4, and in the solution of 5% mass fraction of Na2SO4 and 5% mass fraction of MgSO4. However, contrary to the situation of the solution of 5% mass fraction of MgSO4. The effect of freeze-thaw cycles on the uniaxial compressive strength was larger than the RCA replacement ratio in clear water.
2023, 53(7): 199-208.
doi: 10.13204/j.gyjzG22052305
Abstract:
To study the mechanical properties of hybrid fiber-reinforced manufactured sand concrete, a tatal of 54 specimens were designed and fabricated for static compression tests taking manufactured sand substitution ratios (0%, 50%, 100%) and types of hybrid fibers (steel-basalt fibres, steel-polypropylene fibres) as variation parameters. The stress damage processes and patterns of the specimens were observed and the load-displacement curves were obtained. The cubic compressive, cylinder compressive, elastic modulus peak strain, uniaxial strain-stress curve and energy transformation relation of concrete were measured. The results showed that addition of fibers could change the failure mode of concrete from brittleness to ductility, while addition of manufactured sand had little effect on failure modes of concrete. Addition of fibers improved the mechanical properties of concrete. With the manufactured sand substitution ratios increased, the enhanced effect of fibers on compressive strength and elastic moduli of concrete decreased. The elastic energy release ratios and dissipation energy increase ratios of manufactured sand concrete were smaller than that of conventional concrete when crack propagated. Comparatively, the hybridization of steel fibers and basalt fibers was more conducive to improve compression property of concrete than the hybridization of steel and polypropylene fibers. Finally, the formulas for predicting the mechanical indices and constitutive model were proposed, and the calculated results were in good agreement with experimental results.
To study the mechanical properties of hybrid fiber-reinforced manufactured sand concrete, a tatal of 54 specimens were designed and fabricated for static compression tests taking manufactured sand substitution ratios (0%, 50%, 100%) and types of hybrid fibers (steel-basalt fibres, steel-polypropylene fibres) as variation parameters. The stress damage processes and patterns of the specimens were observed and the load-displacement curves were obtained. The cubic compressive, cylinder compressive, elastic modulus peak strain, uniaxial strain-stress curve and energy transformation relation of concrete were measured. The results showed that addition of fibers could change the failure mode of concrete from brittleness to ductility, while addition of manufactured sand had little effect on failure modes of concrete. Addition of fibers improved the mechanical properties of concrete. With the manufactured sand substitution ratios increased, the enhanced effect of fibers on compressive strength and elastic moduli of concrete decreased. The elastic energy release ratios and dissipation energy increase ratios of manufactured sand concrete were smaller than that of conventional concrete when crack propagated. Comparatively, the hybridization of steel fibers and basalt fibers was more conducive to improve compression property of concrete than the hybridization of steel and polypropylene fibers. Finally, the formulas for predicting the mechanical indices and constitutive model were proposed, and the calculated results were in good agreement with experimental results.
2023, 53(7): 209-216.
doi: 10.13204/j.gyjzG22041410
Abstract:
The National Speed Skating Oval is a large building. In order to implement the concept of sustainable development and economy in the Winter Olympics, the project of the National Speed Skating Oval has a good use of a large amount of demolished concrete of the pile head to produce recycled aggregate which is used in the precast stand-plates. In the light of the durability requirements of recycled aggregate concrete (RAC), recycled aggregate concrete and fair-faced normal aggregate concrete (NAC) with the same strength were designed according to a specific concrete ratio and were tested in the experiments of mechanics, carbonation and freeze-thaw cycles.In addition, the microscopic mechanism analysis was conducted based on CT scanning technology. The results showed that the failure modes of NAC specimens and RAC specimens were the same at the microscopic level, and the CT scanning showed that RAC specimens would lead to the increase of mass loss with the increase of the number of cycles,which fairly faster than NAC.
The National Speed Skating Oval is a large building. In order to implement the concept of sustainable development and economy in the Winter Olympics, the project of the National Speed Skating Oval has a good use of a large amount of demolished concrete of the pile head to produce recycled aggregate which is used in the precast stand-plates. In the light of the durability requirements of recycled aggregate concrete (RAC), recycled aggregate concrete and fair-faced normal aggregate concrete (NAC) with the same strength were designed according to a specific concrete ratio and were tested in the experiments of mechanics, carbonation and freeze-thaw cycles.In addition, the microscopic mechanism analysis was conducted based on CT scanning technology. The results showed that the failure modes of NAC specimens and RAC specimens were the same at the microscopic level, and the CT scanning showed that RAC specimens would lead to the increase of mass loss with the increase of the number of cycles,which fairly faster than NAC.
2023, 53(7): 217-222.
doi: 10.13204/j.gyjzG23032207
Abstract:
The application of bamboo and wood materials in construction and other fields are gradually increasing corresponding to the requirements of sustainable development. To explore the potentials of bamboo and timber for various application environments at low temperatures, the bending performance of thick-strip glubam and SPF (spruce-pine-fir) with two moisture contents (oven-dried and air-dried) at conditions of low temperature (-196 to 20℃) and freeze-thaw cycle were examined. The elastic modulus and strength of rupture of glubam and SPF were measured respectively through static bending tests. The results showed that the variation of mechanical properties of thick-strip glubam and SPF at low temperatures was complicated, but both showed good bending performance. The peak strength of thick-strip glubam appearred at -50℃, which was higher than that at room temperature. Compared with air-dried materials, the strength variation amplitude of oven-dried materials was smaller.
The application of bamboo and wood materials in construction and other fields are gradually increasing corresponding to the requirements of sustainable development. To explore the potentials of bamboo and timber for various application environments at low temperatures, the bending performance of thick-strip glubam and SPF (spruce-pine-fir) with two moisture contents (oven-dried and air-dried) at conditions of low temperature (-196 to 20℃) and freeze-thaw cycle were examined. The elastic modulus and strength of rupture of glubam and SPF were measured respectively through static bending tests. The results showed that the variation of mechanical properties of thick-strip glubam and SPF at low temperatures was complicated, but both showed good bending performance. The peak strength of thick-strip glubam appearred at -50℃, which was higher than that at room temperature. Compared with air-dried materials, the strength variation amplitude of oven-dried materials was smaller.
2023, 53(7): 223-230.
doi: 10.13204/j.gyjzG22110402
Abstract:
The long-term performance of GFRP-wound pipes is an important factor affecting the design and application of GFRP pipes in the marine environment. The durability of GFRP-wound pipes in the condition of seawater immersion, wet-dry condensation cycle and UV radiation with or without UV protective coating was researched. A total of 306 GFRP-wound pipes were experienced accelerated aging in the laboratory for 90 days. The spilt-disk test was conducted after laboratory aging treatment, the influence of different types of exposed environments on the performance of GFRP-wound pipe was obtained. The results showed that:1) in the seawater immersion environment, the circumferential tensile strength of GFRP-wound pipes with different thicknesses decreased to different degrees, but after a long time, the circumferential tensile strength retention ratios of GFRP-wound pipes with different thicknesses tended to be consistent; 2) in the ultraviolet irradiation environment, the circumferential tensile strength of GFRP-wound pipes with thinner thickness decreased significantly; 3) the UV protective coating could make the circumferential tensile strength degradation of GFRP-wound pipes in the ultraviolet irradiation environment slow down, and the protection effect of the thinner the tube was more obvious.
The long-term performance of GFRP-wound pipes is an important factor affecting the design and application of GFRP pipes in the marine environment. The durability of GFRP-wound pipes in the condition of seawater immersion, wet-dry condensation cycle and UV radiation with or without UV protective coating was researched. A total of 306 GFRP-wound pipes were experienced accelerated aging in the laboratory for 90 days. The spilt-disk test was conducted after laboratory aging treatment, the influence of different types of exposed environments on the performance of GFRP-wound pipe was obtained. The results showed that:1) in the seawater immersion environment, the circumferential tensile strength of GFRP-wound pipes with different thicknesses decreased to different degrees, but after a long time, the circumferential tensile strength retention ratios of GFRP-wound pipes with different thicknesses tended to be consistent; 2) in the ultraviolet irradiation environment, the circumferential tensile strength of GFRP-wound pipes with thinner thickness decreased significantly; 3) the UV protective coating could make the circumferential tensile strength degradation of GFRP-wound pipes in the ultraviolet irradiation environment slow down, and the protection effect of the thinner the tube was more obvious.
2023, 53(7): 231-236.
doi: 10.13204/j.gyjzG23021618
Abstract:
With the increase of service time of concrete structures, the generated cracks will continue to expand and may cause damage to the structure. Therefore, crack detection is of great significance for the health monitoring of concrete structures, but traditional ultrasonic and artificial vision-based detection methods can not quickly classify cracks. Based on MobileNetV2 lightweight convolutional network and TensorFlow deep learning framework, a prediction model for rapid identification and classification of concrete structure crack was established. Firstly, the data set was extracted and partitioned based on the pathlib method; secondly, data enhancement based on transfer learning expanded the data set; thirdly, based on the TensorFlow framework, Keras was used to build the pooling layer of the convolutional network; finally, a complete convolutional network architecture and obtained the results were obtained. The test results showed that the model converged, the prediction accuracy reached 0.997 5, and the training time was only 710 s. It could provide help for mobile equipment detection in the project site.
With the increase of service time of concrete structures, the generated cracks will continue to expand and may cause damage to the structure. Therefore, crack detection is of great significance for the health monitoring of concrete structures, but traditional ultrasonic and artificial vision-based detection methods can not quickly classify cracks. Based on MobileNetV2 lightweight convolutional network and TensorFlow deep learning framework, a prediction model for rapid identification and classification of concrete structure crack was established. Firstly, the data set was extracted and partitioned based on the pathlib method; secondly, data enhancement based on transfer learning expanded the data set; thirdly, based on the TensorFlow framework, Keras was used to build the pooling layer of the convolutional network; finally, a complete convolutional network architecture and obtained the results were obtained. The test results showed that the model converged, the prediction accuracy reached 0.997 5, and the training time was only 710 s. It could provide help for mobile equipment detection in the project site.
2023, 53(7): 237-242.
doi: 10.13204/j.gyjzG22052507
Abstract:
Through interpretation of local nostalgic cultural connotations,the local nostalgic expressions in design of architecture and landscape elements were studied, and the practical path of connotations endowed with regional culture and rustic sentiments was discussed. Then, the creative approach of rustic landscapes, which was integrated with local nostalgia, was expounded in the course of new urbanization construction. Taking the planning and design of architectural landscapes for Nanhu International Club in Jiaxing as an example, the relation between the architectural style and ideograph was explored; the specific techniques and approaches of ideographic application in architectural landscape design were discussed from the renovation of old buildings, perpetuation of new buildings, ideograph for culture of Jiangnan watery regions, which was expected to explore an architectural approach of ideograph in increasingly local nostalgic architectural design practice, which was integrated with rustic sentiments.
Through interpretation of local nostalgic cultural connotations,the local nostalgic expressions in design of architecture and landscape elements were studied, and the practical path of connotations endowed with regional culture and rustic sentiments was discussed. Then, the creative approach of rustic landscapes, which was integrated with local nostalgia, was expounded in the course of new urbanization construction. Taking the planning and design of architectural landscapes for Nanhu International Club in Jiaxing as an example, the relation between the architectural style and ideograph was explored; the specific techniques and approaches of ideographic application in architectural landscape design were discussed from the renovation of old buildings, perpetuation of new buildings, ideograph for culture of Jiangnan watery regions, which was expected to explore an architectural approach of ideograph in increasingly local nostalgic architectural design practice, which was integrated with rustic sentiments.
