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2022 Vol. 52, No. 2
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2022, 52(2): 1-9.
doi: 10.13204/j.gyjzG20102205
Abstract:
Fracture parameters can be used to analyze the influence of fibers on fiber-reinforced concrete specimens at different loading stages, thus being helpful to evaluate the fracture property of fiber-reinforced concrete accurately. In the paper, the common fiber concrete fracture test methods and their characteristics were sorted out, the fracture parameters based on the test methods were introduced and classified, and the advantages and disadvantages of parameters in the same and different types were compared and discussed. According to the experimental results of the existing research, the main factors to influence the fracture parameters were found and the influence pattern was concluded. The results showed that three-point bending beams and four-point bending beams were the common testing specimens to determine the fracture parameters of fiber-reinforced concrete. The parameters obtained by those specimens indicated different fracture properties of fiber-reinforced concrete, and the equivalent flexural tensile strength was recommended to evaluate the fracture property of fiber-reinforced concrete at different loading stages. Furthermore, the prospect of the future research on fiber-reinforced concrete was proposed.
Fracture parameters can be used to analyze the influence of fibers on fiber-reinforced concrete specimens at different loading stages, thus being helpful to evaluate the fracture property of fiber-reinforced concrete accurately. In the paper, the common fiber concrete fracture test methods and their characteristics were sorted out, the fracture parameters based on the test methods were introduced and classified, and the advantages and disadvantages of parameters in the same and different types were compared and discussed. According to the experimental results of the existing research, the main factors to influence the fracture parameters were found and the influence pattern was concluded. The results showed that three-point bending beams and four-point bending beams were the common testing specimens to determine the fracture parameters of fiber-reinforced concrete. The parameters obtained by those specimens indicated different fracture properties of fiber-reinforced concrete, and the equivalent flexural tensile strength was recommended to evaluate the fracture property of fiber-reinforced concrete at different loading stages. Furthermore, the prospect of the future research on fiber-reinforced concrete was proposed.
2022, 52(2): 10-17,31.
doi: 10.13204/j.gyjzG20112711
Abstract:
The combined use of fibers and recycled concrete improves the defects of recycled concrete and strengthens its mechanical and durability properties. The paper introduced the research status of fibers-recycled concrete from the aspects of fiber types and modification effects through literature review. Comparison with common recycled concrete, the common steel fiber could increase the compressive, splitting and flexural strength of recycled concrete by 40.1%, 124.6% and 286.1% respectively with the volume content of could 2%, while improving the compactness of recycled concrete and its fatigue life. Similarly, the polypropylene fiber could effectively control the fracture development and improve the fracture performance of recycled concrete. With the 1.2% volume content of it, the fracture toughness and fracture energy could be increased by 71.13% and 330.77% respectively. In addition, the spalling of recycled concrete under high temperatures could be reduced by the fusion of polypropylene fibers. And also, the basalt fiber had a good effect on improving the chloride ion permeability of recycled concrete while optimizing its mechanical properties, the 3% volume content of it had the most significant improvement effect. Moreover, the recycled fiber could be made from discarded carpets and tires through manual cutting, pyrolysis, low-temperature reduction and other processes, and its performance could reach the level of general fibers. The compressive strength of the recycled concrete with the 0.12% volume content of recycled polypropylene steel fibers could be increased by 12.34% comparison with common recycled concrete. Furthermore, based on the discussion of appropriate modification properties for each fiber, the prospects of the recycled fiber and the hybrid application of fibers were presented, which would benefited further research and application of the fiber-recycled concrete.
The combined use of fibers and recycled concrete improves the defects of recycled concrete and strengthens its mechanical and durability properties. The paper introduced the research status of fibers-recycled concrete from the aspects of fiber types and modification effects through literature review. Comparison with common recycled concrete, the common steel fiber could increase the compressive, splitting and flexural strength of recycled concrete by 40.1%, 124.6% and 286.1% respectively with the volume content of could 2%, while improving the compactness of recycled concrete and its fatigue life. Similarly, the polypropylene fiber could effectively control the fracture development and improve the fracture performance of recycled concrete. With the 1.2% volume content of it, the fracture toughness and fracture energy could be increased by 71.13% and 330.77% respectively. In addition, the spalling of recycled concrete under high temperatures could be reduced by the fusion of polypropylene fibers. And also, the basalt fiber had a good effect on improving the chloride ion permeability of recycled concrete while optimizing its mechanical properties, the 3% volume content of it had the most significant improvement effect. Moreover, the recycled fiber could be made from discarded carpets and tires through manual cutting, pyrolysis, low-temperature reduction and other processes, and its performance could reach the level of general fibers. The compressive strength of the recycled concrete with the 0.12% volume content of recycled polypropylene steel fibers could be increased by 12.34% comparison with common recycled concrete. Furthermore, based on the discussion of appropriate modification properties for each fiber, the prospects of the recycled fiber and the hybrid application of fibers were presented, which would benefited further research and application of the fiber-recycled concrete.
2022, 52(2): 18-23,107.
doi: 10.13204/j.gyjzG20092909
Abstract:
The compressive, splitting tensile and flexural tests of plain concrete, nano-SiO2 concrete and basalt fiber nano-SiO2 concrete under high temperatures were carried out, and the prediction model of concrete strength that was established. According to the results, the compressive strength of each group reached a peak value at 400 ℃, at that time, each group of concrete at normal temperature increased by about 3.5% to 6.8%, and then decreased gradually, and the splitting tensile strength and flexural strength decreased gradually with the increase of temperature, at 800 ℃, the residual ratios of cracking and pulling strength and the residual ratios of flexural strength were 27.6% and 36.2%, respectively. Adding nano-SiO2 could improved the compressive, splitting tensile and flexural strength of plain concrete. The compressive strength, splitting tensile strength and flexural strength of nano-SiO2 concrete after being subjected to 800 ℃ high temperature were increased by 33.7%,15.6% and 17.2% respectively. The accuracy of concrete strength prediction after being subjected to high temperatures was high.
The compressive, splitting tensile and flexural tests of plain concrete, nano-SiO2 concrete and basalt fiber nano-SiO2 concrete under high temperatures were carried out, and the prediction model of concrete strength that was established. According to the results, the compressive strength of each group reached a peak value at 400 ℃, at that time, each group of concrete at normal temperature increased by about 3.5% to 6.8%, and then decreased gradually, and the splitting tensile strength and flexural strength decreased gradually with the increase of temperature, at 800 ℃, the residual ratios of cracking and pulling strength and the residual ratios of flexural strength were 27.6% and 36.2%, respectively. Adding nano-SiO2 could improved the compressive, splitting tensile and flexural strength of plain concrete. The compressive strength, splitting tensile strength and flexural strength of nano-SiO2 concrete after being subjected to 800 ℃ high temperature were increased by 33.7%,15.6% and 17.2% respectively. The accuracy of concrete strength prediction after being subjected to high temperatures was high.
2022, 52(2): 24-31.
doi: 10.13204/j.gyjzG21042606
Abstract:
The corrosion resistance experiments of concrete with basalt fiber proportion of 0%, 0.1%, 0.2% and 0.3% were conducted, in which the conorete specimens were soaked in compound salt solutions of MgSO4 mixed with Na2SO4 and NaCl, to explore the corrosion resistance of concrete specimens with different basalt fiber proportion. Based on the saline soil environment of the Southern Xinjiang area, the concrete of strength grade C35 commonly used in the existing structures in the area was adopted. The relative masses and relative of elastic moduli of specimens were selected as the main indexes for analysis and evaluation. The results showed that the fluctuation range of the relative masses and the relative elastic moduli of concrete specimens with the basalt fiber of 0.3% were lower than those of other specimens, which indicated that the resistance of concrete to erosion of compound salt solutions was improved. The analysis for microstructure of specimens showed that the main production composition in concrete immersed in compound salt solutions of MgSO4 mixed with Na2SO4 and NaCl were ettringite and gypsum. The adding of basalt fibers reduced the generation of corrosion products, which was consistent with the change of its macroscopic indicators.
The corrosion resistance experiments of concrete with basalt fiber proportion of 0%, 0.1%, 0.2% and 0.3% were conducted, in which the conorete specimens were soaked in compound salt solutions of MgSO4 mixed with Na2SO4 and NaCl, to explore the corrosion resistance of concrete specimens with different basalt fiber proportion. Based on the saline soil environment of the Southern Xinjiang area, the concrete of strength grade C35 commonly used in the existing structures in the area was adopted. The relative masses and relative of elastic moduli of specimens were selected as the main indexes for analysis and evaluation. The results showed that the fluctuation range of the relative masses and the relative elastic moduli of concrete specimens with the basalt fiber of 0.3% were lower than those of other specimens, which indicated that the resistance of concrete to erosion of compound salt solutions was improved. The analysis for microstructure of specimens showed that the main production composition in concrete immersed in compound salt solutions of MgSO4 mixed with Na2SO4 and NaCl were ettringite and gypsum. The adding of basalt fibers reduced the generation of corrosion products, which was consistent with the change of its macroscopic indicators.
2022, 52(2): 32-36,114.
doi: 10.13204/j.gyjzG21071801
Abstract:
In order to study the bond properties between ceramsite concrete roinforced with hybrid fibers of steel and polypropylene and threaded rebars, the cubic compressive strength and splitting tensile strength tests of 16 groups of ceramsite concrete with different hybrid fiber porportion were conducted. The variation of mechanical properties of concrete with hybrid fiber porportion was obtained. The ultimate bond strength, peak slip and failure mode of threaded rebars and concrete were obtained through the bond performance test of rebars and concrete. Based on the measured bond strength data, a formula for calculating the ultimate bond strength of ceramsite concrete with the hybrid fibers was established. The formula took into account the cubic compressive strength of ceramsite concrete without fibers, the characteristic parameters of steel and polypropylene fibers, the diameter of steel bars, the thickness of concrete covers and the bond length. Based on the measured bond strength and slip values, a three-stage (ascending, horizontal and descending) bond slip model was proposed to describe the bond property of ceramsite concrete with the hybrid fibers of steel and polypropylene and threaded rebars.
In order to study the bond properties between ceramsite concrete roinforced with hybrid fibers of steel and polypropylene and threaded rebars, the cubic compressive strength and splitting tensile strength tests of 16 groups of ceramsite concrete with different hybrid fiber porportion were conducted. The variation of mechanical properties of concrete with hybrid fiber porportion was obtained. The ultimate bond strength, peak slip and failure mode of threaded rebars and concrete were obtained through the bond performance test of rebars and concrete. Based on the measured bond strength data, a formula for calculating the ultimate bond strength of ceramsite concrete with the hybrid fibers was established. The formula took into account the cubic compressive strength of ceramsite concrete without fibers, the characteristic parameters of steel and polypropylene fibers, the diameter of steel bars, the thickness of concrete covers and the bond length. Based on the measured bond strength and slip values, a three-stage (ascending, horizontal and descending) bond slip model was proposed to describe the bond property of ceramsite concrete with the hybrid fibers of steel and polypropylene and threaded rebars.
2022, 52(2): 37-41,125.
doi: 10.13204/j.gyjzG20120206
Abstract:
In order to explore the failure mechanism and design method of GFRP-reinforced concrete stubs with hybrid fibers under axial compression, five GFRP-reinforced concrete stubs with bybrid fibers and an ordinary reinforced concrete stub were studied,the failure mode, longitudinal reinforcement strain, concrete compressive strain and ultimate load value of GFRP hybrid-reinforced concrete stubs under axial compression were analyzed. The results showed that the GFRP-reinforced concrete stubs with hybrid fibers had good crack-resistance performances and good integrity after failure; the GFRP-reinforced concrete stubs with hybrid fibers had an obvious plastic stage under axial compression, and the fibers could effectively restrain from propagation of microcracks and increase the ductility of concrete; the elastic modulus of concrete decreased with the increase of steel fibers, and increased with the increase of PVA fibers; the hybrid fibers could effectively improve the ultimate bearing capacity of GFRP-reinforced concrete stubs, and it was the best proportion that the PVA fiber content was 0.1% and the steel fiber content was 0.8%.
In order to explore the failure mechanism and design method of GFRP-reinforced concrete stubs with hybrid fibers under axial compression, five GFRP-reinforced concrete stubs with bybrid fibers and an ordinary reinforced concrete stub were studied,the failure mode, longitudinal reinforcement strain, concrete compressive strain and ultimate load value of GFRP hybrid-reinforced concrete stubs under axial compression were analyzed. The results showed that the GFRP-reinforced concrete stubs with hybrid fibers had good crack-resistance performances and good integrity after failure; the GFRP-reinforced concrete stubs with hybrid fibers had an obvious plastic stage under axial compression, and the fibers could effectively restrain from propagation of microcracks and increase the ductility of concrete; the elastic modulus of concrete decreased with the increase of steel fibers, and increased with the increase of PVA fibers; the hybrid fibers could effectively improve the ultimate bearing capacity of GFRP-reinforced concrete stubs, and it was the best proportion that the PVA fiber content was 0.1% and the steel fiber content was 0.8%.
2022, 52(2): 42-51.
doi: 10.13204/j.gyjzG21042306
Abstract:
Mountain scenic architecture reflect the harmonious architecture wisdom in ancient China based on the natural system. Taking Mount Song as the research object and against the time background of the Qing Dynasty, through the research methods of historical data collection and analysis, field research, terrain space modeling etc, the natural system was divided into five basic elements: terrain, hydrology, meteorology, soil and biology. 37 buildings in Mount Song in the Qing Dynasty were sorted out and divided into 4 types: ritual buildings, religious buildings, residential buildings and educational buildings. The overall spatial distribution characteristics of buildings under the influence of each natural element and the spatial distribution differences of each type were explored respectively, which could deepen the understanding to the development mode of traditional mountains, and provide theoretical support for the positioning of scenic spots and the localization coustruction of the national park system. It was found that the buildings in Mount Song adapted to and made good use of the natural system, which reflected the wisdom of construction that conformed to nature, made good use of the situation, chosen the site according to the spiritual pursuit, and finally achieved the balance state of harmony between nature and humanity.
Mountain scenic architecture reflect the harmonious architecture wisdom in ancient China based on the natural system. Taking Mount Song as the research object and against the time background of the Qing Dynasty, through the research methods of historical data collection and analysis, field research, terrain space modeling etc, the natural system was divided into five basic elements: terrain, hydrology, meteorology, soil and biology. 37 buildings in Mount Song in the Qing Dynasty were sorted out and divided into 4 types: ritual buildings, religious buildings, residential buildings and educational buildings. The overall spatial distribution characteristics of buildings under the influence of each natural element and the spatial distribution differences of each type were explored respectively, which could deepen the understanding to the development mode of traditional mountains, and provide theoretical support for the positioning of scenic spots and the localization coustruction of the national park system. It was found that the buildings in Mount Song adapted to and made good use of the natural system, which reflected the wisdom of construction that conformed to nature, made good use of the situation, chosen the site according to the spiritual pursuit, and finally achieved the balance state of harmony between nature and humanity.
2022, 52(2): 52-58,168.
doi: 10.13204/j.gyjzG21031704
Abstract:
Based on the distributed parameter system and the characteristics of the base-isolated frame structure,the construction and solution process of the shear cantilever beam model with distributed parameter of base-isolated considering non-proportional damping were introduced, and the dynamic characteristics of fixed bearing, proportional damping isolation and non-proportional damping isolation models through the model were also studied. The modal decomposition time history analysis method was used to compare the response of the model under partial design method, proportional damping isolation and non-proportional damping isolation. The results showed that the complex mode decomposition method and the real mode decomposition method had few differences in solving the dynamic characteristics of the isolated structures. The isolation layer had limited influence on the period of high-order vibration modes, but it could effectively reduce the modal participation coefficient of high-order vibration modes. The differences between floor shear distribution calculated by the division design method and non-proportional damping method were small. When the overall model with the seismic isolation layer was adopted to analyzed seismic responses,the decomposition method of complex vibration modes considering the non-proportional damping characteristics was recomnended first.
Based on the distributed parameter system and the characteristics of the base-isolated frame structure,the construction and solution process of the shear cantilever beam model with distributed parameter of base-isolated considering non-proportional damping were introduced, and the dynamic characteristics of fixed bearing, proportional damping isolation and non-proportional damping isolation models through the model were also studied. The modal decomposition time history analysis method was used to compare the response of the model under partial design method, proportional damping isolation and non-proportional damping isolation. The results showed that the complex mode decomposition method and the real mode decomposition method had few differences in solving the dynamic characteristics of the isolated structures. The isolation layer had limited influence on the period of high-order vibration modes, but it could effectively reduce the modal participation coefficient of high-order vibration modes. The differences between floor shear distribution calculated by the division design method and non-proportional damping method were small. When the overall model with the seismic isolation layer was adopted to analyzed seismic responses,the decomposition method of complex vibration modes considering the non-proportional damping characteristics was recomnended first.
2022, 52(2): 59-66,74.
doi: 10.13204/j.gyjzG20092305
Abstract:
Through the vertical axial load test of 5 full-scale prefabricated walls integrating thermal insulation and load-bearing, research on the influences of opening, height-to-thickness ratios and loading methods on failure modes, bearing capacity, crack development and other compression performances of the walls under axial compression was performed and the cooperative mechanical performances of aerated concrete blocks with autoclaved sand and concrete frames were analyzed. The research indicated that under concentrated loads, concrete rib columns partly occured in compression failure, and the concrete rib columns, concrete rib beams and blocks in walls were of better cooperative mechanical performances; under uniform loads, within the teet height-to-thickness ratio ranges, the lateral displacement of the walls was less than 6 mm, no instability failure occured. As the height-to-thickness ratios of the walls increased, the bearing capacity decreased and the opening could change the failure mode of the walls; the aerated concrete blocks with autoclaved sand and the concrete frames were mutually constrained to form a force-bearing whole, and the ribs bore the main loads; the calculation formula for the axial compressive bearing capacity of the prefabricated walls integrating thermal insulation and load-bearing was given, and its calculation results were in accordance with the experimental values.
Through the vertical axial load test of 5 full-scale prefabricated walls integrating thermal insulation and load-bearing, research on the influences of opening, height-to-thickness ratios and loading methods on failure modes, bearing capacity, crack development and other compression performances of the walls under axial compression was performed and the cooperative mechanical performances of aerated concrete blocks with autoclaved sand and concrete frames were analyzed. The research indicated that under concentrated loads, concrete rib columns partly occured in compression failure, and the concrete rib columns, concrete rib beams and blocks in walls were of better cooperative mechanical performances; under uniform loads, within the teet height-to-thickness ratio ranges, the lateral displacement of the walls was less than 6 mm, no instability failure occured. As the height-to-thickness ratios of the walls increased, the bearing capacity decreased and the opening could change the failure mode of the walls; the aerated concrete blocks with autoclaved sand and the concrete frames were mutually constrained to form a force-bearing whole, and the ribs bore the main loads; the calculation formula for the axial compressive bearing capacity of the prefabricated walls integrating thermal insulation and load-bearing was given, and its calculation results were in accordance with the experimental values.
2022, 52(2): 67-74.
doi: 10.13204/j.gyjzG21061614
Abstract:
With the development of steel-smelting technology, using fire-resistant and weathering steel and encased profiled steel sheets to promote the fire resistance of composite beams has become a new solution for steel structure fire design. Adopting appropriate thermo-mechanical material properties and calculating strategies, the accuracy and reliability of the numerical model were verified by comparing the results calculated in ABAQUS platform based on the experimental data from fire resistance tests of steel-concrete composite beams. Based on the proposed benchmark model, adopting different material thermal expansion coefficients, load ratios and steel beam sizes, conclusions were drawn that the thermal expansion coefficient, steel beam height, thickness of the composite slab and load ratio had a greater influence on the fire resistance of simply supported fire-resistant and weathering steel-concrete composite beams. By comparing the results calculated by the numerical model with those calculated by the bearing capacity method according to Code for fire safety of steel structures in buildings(GB 51249-2017), a modified bearing capacity method was proposed for the composite beams.
With the development of steel-smelting technology, using fire-resistant and weathering steel and encased profiled steel sheets to promote the fire resistance of composite beams has become a new solution for steel structure fire design. Adopting appropriate thermo-mechanical material properties and calculating strategies, the accuracy and reliability of the numerical model were verified by comparing the results calculated in ABAQUS platform based on the experimental data from fire resistance tests of steel-concrete composite beams. Based on the proposed benchmark model, adopting different material thermal expansion coefficients, load ratios and steel beam sizes, conclusions were drawn that the thermal expansion coefficient, steel beam height, thickness of the composite slab and load ratio had a greater influence on the fire resistance of simply supported fire-resistant and weathering steel-concrete composite beams. By comparing the results calculated by the numerical model with those calculated by the bearing capacity method according to Code for fire safety of steel structures in buildings(GB 51249-2017), a modified bearing capacity method was proposed for the composite beams.
2022, 52(2): 75-80.
doi: 10.13204/j.gyjzG201902180009
Abstract:
Based on a long-span and complex steel frames building with inclined pillars in a relic protection project, the finite element model was constructed to simulate the whole process of construction. Based on the actual situation of the site, considering the influence of the original soil piled up, the model was optimized and the construction process was adjusted, and the prestressed three-stage tensioning scheme was adjusted to a two-stage tensioning scheme; the stress in crucial sections of inclined pillar support system and the displacement of pillar tops were obtained during the construction process of the structure and compared with the measured data of the corresponding measuring point. The results showed that the theoretical values were in good agreement with the measured values. The crucial section stress and pile top displacement of each members were within the allowable range. The two-stage tensioning scheme was reasonable and could ensure the safety of the construction process of the structure. The simplified model of the piles could reflect the internal forces of the members of the inclined pillar support system and the displacement of the pile tops displacement to a certain extent, and had certain practicability.
Based on a long-span and complex steel frames building with inclined pillars in a relic protection project, the finite element model was constructed to simulate the whole process of construction. Based on the actual situation of the site, considering the influence of the original soil piled up, the model was optimized and the construction process was adjusted, and the prestressed three-stage tensioning scheme was adjusted to a two-stage tensioning scheme; the stress in crucial sections of inclined pillar support system and the displacement of pillar tops were obtained during the construction process of the structure and compared with the measured data of the corresponding measuring point. The results showed that the theoretical values were in good agreement with the measured values. The crucial section stress and pile top displacement of each members were within the allowable range. The two-stage tensioning scheme was reasonable and could ensure the safety of the construction process of the structure. The simplified model of the piles could reflect the internal forces of the members of the inclined pillar support system and the displacement of the pile tops displacement to a certain extent, and had certain practicability.
2022, 52(2): 81-89.
doi: 10.13204/j.gyjzG21053113
Abstract:
In traditional vertical industrial workshops that use reinforced concrete structures and steel structures, when the span is relatively large and the load is relatively heavy, the use of a steel-concrete composite structure system can bring better overall benefits. As a place where grain is stacked, the vertical granary workshop has the characteristic of bearing a relatively large load. In order to investigate the comprehensive benefits of different structural systems used in multi-story industrial workshops, a granary frame structure in Hainan Province was taken as an example. Based on the design software, the reinforced concrete structure, steel structure and steel-concrete composite structure were adopted for scheme design, and the economic indicators of the three structural systems were calculated. The static pushover analysis and dynamic elasto-plastic time history analysis of the structures were carried out by using the finite element analysis software. Performance indexes including the load-bearing capacity, lateral stiffness, story drift and distribution of plastic hinges of different structural systems were compared. The analysis results exhibit that the steel-concrete composite structure has broad application prospects in multi-story industrial plants due to its superior mechanical performance, convenient construction performance and extraordinary comprehensive benefits.
In traditional vertical industrial workshops that use reinforced concrete structures and steel structures, when the span is relatively large and the load is relatively heavy, the use of a steel-concrete composite structure system can bring better overall benefits. As a place where grain is stacked, the vertical granary workshop has the characteristic of bearing a relatively large load. In order to investigate the comprehensive benefits of different structural systems used in multi-story industrial workshops, a granary frame structure in Hainan Province was taken as an example. Based on the design software, the reinforced concrete structure, steel structure and steel-concrete composite structure were adopted for scheme design, and the economic indicators of the three structural systems were calculated. The static pushover analysis and dynamic elasto-plastic time history analysis of the structures were carried out by using the finite element analysis software. Performance indexes including the load-bearing capacity, lateral stiffness, story drift and distribution of plastic hinges of different structural systems were compared. The analysis results exhibit that the steel-concrete composite structure has broad application prospects in multi-story industrial plants due to its superior mechanical performance, convenient construction performance and extraordinary comprehensive benefits.
2022, 52(2): 90-95.
doi: 10.13204/j.gyjzG20123004
Abstract:
In order to quantitatively describe the spatial deformation characteristics of landslides, based on the survey of the topography, landform and geological structure of Yutaicun Village Landslide in Chongqing, advanced comprehensive monitoring technology including absolute surface-displacement monitoring by GPS, deep deformation monitoring by Fiber Bragg Grating and crack-deformation monitoring by automatic pull-lines were conducted. Combined with the characteristics of crack deformation of Yutaicun Village Landslide, the spatial deformation law and instability failure mechanism of the landslide were analyzed comprehensively. The results showed that: 1) The comprehensive monitoring methods were conducive to comprehensive analysis of the three-dimensional deformation characteristics of Yutaicun Village Landslide in terms of surface deformation, deep deformation and crack deformation. It was an efficient, economical, and complementary monitoring method. 2) The deformation monitoring data of Yutaicun Village Landslide showed the characteristics of phased deformation for deep sliding bodies. In the early stage of instability, the overall sliding rate of the rear part of the landslide was relatively faster, and the amount of deformation increased approximately linearly with time, and the fluctuation of the surface monitoring data had a strong response on rainfall. With the development of sliding, the crack deformation at the trailing edge gradually withdrew from the growth stage, and the crack deformation near the middle sliding body was still more active, and the difference in deformation was related to the steep terrain. 3) The unfavorable terrain and water catchment condition, continuous rainfall, water resistance of bedrock, front cut slope and back-slope stacking constitute the main controlling factors for landslide deformation.
In order to quantitatively describe the spatial deformation characteristics of landslides, based on the survey of the topography, landform and geological structure of Yutaicun Village Landslide in Chongqing, advanced comprehensive monitoring technology including absolute surface-displacement monitoring by GPS, deep deformation monitoring by Fiber Bragg Grating and crack-deformation monitoring by automatic pull-lines were conducted. Combined with the characteristics of crack deformation of Yutaicun Village Landslide, the spatial deformation law and instability failure mechanism of the landslide were analyzed comprehensively. The results showed that: 1) The comprehensive monitoring methods were conducive to comprehensive analysis of the three-dimensional deformation characteristics of Yutaicun Village Landslide in terms of surface deformation, deep deformation and crack deformation. It was an efficient, economical, and complementary monitoring method. 2) The deformation monitoring data of Yutaicun Village Landslide showed the characteristics of phased deformation for deep sliding bodies. In the early stage of instability, the overall sliding rate of the rear part of the landslide was relatively faster, and the amount of deformation increased approximately linearly with time, and the fluctuation of the surface monitoring data had a strong response on rainfall. With the development of sliding, the crack deformation at the trailing edge gradually withdrew from the growth stage, and the crack deformation near the middle sliding body was still more active, and the difference in deformation was related to the steep terrain. 3) The unfavorable terrain and water catchment condition, continuous rainfall, water resistance of bedrock, front cut slope and back-slope stacking constitute the main controlling factors for landslide deformation.
2022, 52(2): 96-100,150.
doi: 10.13204/j.gyjzG20121502
Abstract:
The variation curve of the deeply horizontal displacement of foundation excavation is influenced by many factors such as retaining forms, geological conditions and surrounding building loads. Therefore, the shape of the inclination measurement curve is different. In complex conditions, even the actual measured value exceeded the control value, the slopes of foundation still safe, namely, the maximum horizontal displacement was not the most dangerous point of the structure. Therefore, 105 inclination curves from 8 typical retaining projects of foundation excavation were statistically classified, and shapes of the curves and their force characteristics were correlated with each other;as well, a method for hazard judgment of piles by relative displacement was proposed. The results showed that the inclination curves could be roughly divided into five categories: the parabo type, the open type, the wave type, the inverse S type and the other according to the curve characteristics; the method for finding the dangerous points of the retaining structure by the relative displacement method was basically feasible. The stress of the retaining structure had a linear relation with the relative displacement, which increased with the increase of the relative displacement offset value.
The variation curve of the deeply horizontal displacement of foundation excavation is influenced by many factors such as retaining forms, geological conditions and surrounding building loads. Therefore, the shape of the inclination measurement curve is different. In complex conditions, even the actual measured value exceeded the control value, the slopes of foundation still safe, namely, the maximum horizontal displacement was not the most dangerous point of the structure. Therefore, 105 inclination curves from 8 typical retaining projects of foundation excavation were statistically classified, and shapes of the curves and their force characteristics were correlated with each other;as well, a method for hazard judgment of piles by relative displacement was proposed. The results showed that the inclination curves could be roughly divided into five categories: the parabo type, the open type, the wave type, the inverse S type and the other according to the curve characteristics; the method for finding the dangerous points of the retaining structure by the relative displacement method was basically feasible. The stress of the retaining structure had a linear relation with the relative displacement, which increased with the increase of the relative displacement offset value.
2022, 52(2): 101-107.
doi: 10.13204/j.gyjzG20120504
Abstract:
The stability for the trench of diaphragm walls is related to the safety and quality of trenching construction. To ensure the stability of trenches, the stress variation in the earth of trench walls was analyzed under trenching construction, the stability conditions and influencing factors of trench walls were discussed, the influence of space-time effect was discussed emphatically, and the influence of space-time effect was verified by the measured data. The results showed that: the time effect had a significant effect on the stability of the trench. Increasing the mass density of slurry and the level of mud and could improve the trench stability, and the latter was more effective. The shallow soil in the middle of the trench was more disturbed during construction of trenching, and the lateral displacement, the subsidence of the earths surface and the earth pressure appeared a certain spatial effect.
The stability for the trench of diaphragm walls is related to the safety and quality of trenching construction. To ensure the stability of trenches, the stress variation in the earth of trench walls was analyzed under trenching construction, the stability conditions and influencing factors of trench walls were discussed, the influence of space-time effect was discussed emphatically, and the influence of space-time effect was verified by the measured data. The results showed that: the time effect had a significant effect on the stability of the trench. Increasing the mass density of slurry and the level of mud and could improve the trench stability, and the latter was more effective. The shallow soil in the middle of the trench was more disturbed during construction of trenching, and the lateral displacement, the subsidence of the earths surface and the earth pressure appeared a certain spatial effect.
2022, 52(2): 108-114.
doi: 10.13204/j.gyjzG20120701
Abstract:
As wind turbines in mountain areas in outskirts of towns can avoid occupy a large amount of cultivated land for wind turbines on the plains and save a large number of high voltage transmission lines for wind turbines in the deserts, wind turbines in mountain areas in outskirts of towns have become effective ways to meet the electricity demand in urban energy-consumption. The cone-shaped foundation was an innovative type of the mountain wind turbine foundation, which outperformed the traditional wind turbine foundations in mountain areas in decreasing the usage of steel and concrete, in increasing the bearing capacity of foundations, and in reducing the excavation volumes of foundation and the bad effect of backfills on the environment. The calculation method of void areas between bottom surfaces of foundations and the rock masses was proposed. Combining numerical simulations with theoretical methods, the calculatioin method of void areas under bases was studied, and the influences of void ratios, mechanical indexes of weathered rock and geometric sizes of foundations on subgrade reaction, lateral displacement and the tilt rates of foundations were also disccused, respectively. Moreover, the effect of the rubber layer placed the sidewall of foundations on the rebound rates of unloaded foundations was analyzed. The stability of overturning resistance for the cone-shaped foundation was also constructed.
As wind turbines in mountain areas in outskirts of towns can avoid occupy a large amount of cultivated land for wind turbines on the plains and save a large number of high voltage transmission lines for wind turbines in the deserts, wind turbines in mountain areas in outskirts of towns have become effective ways to meet the electricity demand in urban energy-consumption. The cone-shaped foundation was an innovative type of the mountain wind turbine foundation, which outperformed the traditional wind turbine foundations in mountain areas in decreasing the usage of steel and concrete, in increasing the bearing capacity of foundations, and in reducing the excavation volumes of foundation and the bad effect of backfills on the environment. The calculation method of void areas between bottom surfaces of foundations and the rock masses was proposed. Combining numerical simulations with theoretical methods, the calculatioin method of void areas under bases was studied, and the influences of void ratios, mechanical indexes of weathered rock and geometric sizes of foundations on subgrade reaction, lateral displacement and the tilt rates of foundations were also disccused, respectively. Moreover, the effect of the rubber layer placed the sidewall of foundations on the rebound rates of unloaded foundations was analyzed. The stability of overturning resistance for the cone-shaped foundation was also constructed.
2022, 52(2): 115-119.
doi: 10.13204/j.gyjzG20122202
Abstract:
Based on the deformation coordination between the anchorage body and surrounding soil in the elastic-plastic state, a model for load transfer mechanism of anchor bars under the confining pressure was constructed, and the theoretical calculation formulas among external loads, the plastic radius of soil strata embedded in anchor rods and ultimate pull-out forces of anchor rods were deduced. The influence of the coarse particle content, stress state of anchorage bodies and water content of soil on the ultimate drawing forces of anchorage rods in soil strata was analyzed by pull-out tests. The results showed that to improve the stress state of soil strata where anchor rods were embedded in a certain range was beneficial to prevent anchor rods from being pulled out of the soil. When the coarse particle content of the soil was 60%, the soil was relatively denser, the stress in the soil particles was relatively more uniform during being pulled out of anchor rods, and the bearing capacity of the anchor rods was relatively higher. Under the same confining pressure, the ultimate drawing forces of anchor bolts in soil increased first and then decreased with the increase of the water content. In addition, the theoretical calculation values of ultimate drawing forces were in good agreement with the test results, the validity of the theoretical model was verified.
Based on the deformation coordination between the anchorage body and surrounding soil in the elastic-plastic state, a model for load transfer mechanism of anchor bars under the confining pressure was constructed, and the theoretical calculation formulas among external loads, the plastic radius of soil strata embedded in anchor rods and ultimate pull-out forces of anchor rods were deduced. The influence of the coarse particle content, stress state of anchorage bodies and water content of soil on the ultimate drawing forces of anchorage rods in soil strata was analyzed by pull-out tests. The results showed that to improve the stress state of soil strata where anchor rods were embedded in a certain range was beneficial to prevent anchor rods from being pulled out of the soil. When the coarse particle content of the soil was 60%, the soil was relatively denser, the stress in the soil particles was relatively more uniform during being pulled out of anchor rods, and the bearing capacity of the anchor rods was relatively higher. Under the same confining pressure, the ultimate drawing forces of anchor bolts in soil increased first and then decreased with the increase of the water content. In addition, the theoretical calculation values of ultimate drawing forces were in good agreement with the test results, the validity of the theoretical model was verified.
2022, 52(2): 120-125.
doi: 10.13204/j.gyjzG21051810
Abstract:
Through experiments of the concrete with different initial preloading stress levels (IPSLS) that experienced different low temperatures (-40 ℃, -80 ℃, -120 ℃ and -160 ℃), the effect of IPSL on the compressive deformation performances of concrete exposed to ultralow temperatures was discussed. The test results showed that the compressive deformation of concrete with different IPSL increased continually with the decrease in temperature during each temperature ranged from room temperature to given ultralow temperature. Similarly, the compressive deformations of concrete at the cooling target point and the temperature uniformity target point showed an increase trend with the decrease in temperature for these temperature ranges. But there existed difference among the changing rates of the compressive deformation for concrete with different IPSL. The compressive deformations of concrete with lower and higher IPSL were larger than that of concrete with a medium IPSL from beginning to end. The results could provide reference to the design and safety evaluation of prestressed concrete structures as LNG storage tanks.
Through experiments of the concrete with different initial preloading stress levels (IPSLS) that experienced different low temperatures (-40 ℃, -80 ℃, -120 ℃ and -160 ℃), the effect of IPSL on the compressive deformation performances of concrete exposed to ultralow temperatures was discussed. The test results showed that the compressive deformation of concrete with different IPSL increased continually with the decrease in temperature during each temperature ranged from room temperature to given ultralow temperature. Similarly, the compressive deformations of concrete at the cooling target point and the temperature uniformity target point showed an increase trend with the decrease in temperature for these temperature ranges. But there existed difference among the changing rates of the compressive deformation for concrete with different IPSL. The compressive deformations of concrete with lower and higher IPSL were larger than that of concrete with a medium IPSL from beginning to end. The results could provide reference to the design and safety evaluation of prestressed concrete structures as LNG storage tanks.
2022, 52(2): 126-132.
doi: 10.13204/j.gyjzG21032609
Abstract:
The influence of Nano-SiO2 (instead of cement) and rubber powder (instead of natural river sand) on compressive strength and slump of recycled concrete cured for 7 and 28 days was studied by the mass substitution method. Through the test results, it was found that the slump of recycled concrete increased with the increase of rubber powder proportion, and the slump of recycled concrete reached the maximum when the rubber powder proportion reached 5%. When adding nano-SiO2, the slump of recycled concrete decreased with the increase of the Nano-SiO2 content. When the proportion was 3%, the slump of recycled concrete was the smallest. When adding rubber powder, the 7th day compressive strength of recycled concrete decreased with the increase of rubber proportion, and the 28th day compressive strength increased when the rubber powder proportion was less than 5%. When nano-SiO2 was added alone, the 7th day compressive strength of recycled concrete increased with the increase of Nano-SiO2 proportion; when both of rubber powder and nano-SiO2 were added together, it could not only make up for the decrease of rubber strength, but also restrain the slump deterioration after mixing with nano-SiO2, offset the loss of strength by adding rubber powder, then, achieve a complementary effect. The microstructure, transition zone and hydration products of concrete were analyzed by scanning electron microscope.
The influence of Nano-SiO2 (instead of cement) and rubber powder (instead of natural river sand) on compressive strength and slump of recycled concrete cured for 7 and 28 days was studied by the mass substitution method. Through the test results, it was found that the slump of recycled concrete increased with the increase of rubber powder proportion, and the slump of recycled concrete reached the maximum when the rubber powder proportion reached 5%. When adding nano-SiO2, the slump of recycled concrete decreased with the increase of the Nano-SiO2 content. When the proportion was 3%, the slump of recycled concrete was the smallest. When adding rubber powder, the 7th day compressive strength of recycled concrete decreased with the increase of rubber proportion, and the 28th day compressive strength increased when the rubber powder proportion was less than 5%. When nano-SiO2 was added alone, the 7th day compressive strength of recycled concrete increased with the increase of Nano-SiO2 proportion; when both of rubber powder and nano-SiO2 were added together, it could not only make up for the decrease of rubber strength, but also restrain the slump deterioration after mixing with nano-SiO2, offset the loss of strength by adding rubber powder, then, achieve a complementary effect. The microstructure, transition zone and hydration products of concrete were analyzed by scanning electron microscope.
2022, 52(2): 133-138,157.
doi: 10.13204/j.gyjzG21062503
Abstract:
To improve the utilization rate of steel slag powder (SSP) as mineral admixture in cement-based materials, and to enhance the mechanical properties of recycled aggregate concrete (RAC), the influences of SSP and MK on the mechanical properties and microstructure of RAC were studied. The mechanical test results showed that the compressive strength of the mineral admixture at 28 d and 90 d was respectively increased by 13.3% and 18% as the mass fraction of MK in mineral admixture was 30%, compared with that of the reference group, and the changing trend of elastic modulus was similar to that of the compressive strength. Microstructural tests indicated that SSP and MK mixed with Ca(OH)2 decreased the peak strength, generated additional C-S-H gel and increased the percentage of high density C-S-H, which significantly improved the microstructure and interfacial transition zone of RAC in the later stage. These were attributed to the better volcanic ash activity and micro-aggregate filling effect of SSP and MK mixed mixture.
To improve the utilization rate of steel slag powder (SSP) as mineral admixture in cement-based materials, and to enhance the mechanical properties of recycled aggregate concrete (RAC), the influences of SSP and MK on the mechanical properties and microstructure of RAC were studied. The mechanical test results showed that the compressive strength of the mineral admixture at 28 d and 90 d was respectively increased by 13.3% and 18% as the mass fraction of MK in mineral admixture was 30%, compared with that of the reference group, and the changing trend of elastic modulus was similar to that of the compressive strength. Microstructural tests indicated that SSP and MK mixed with Ca(OH)2 decreased the peak strength, generated additional C-S-H gel and increased the percentage of high density C-S-H, which significantly improved the microstructure and interfacial transition zone of RAC in the later stage. These were attributed to the better volcanic ash activity and micro-aggregate filling effect of SSP and MK mixed mixture.
2022, 52(2): 139-143.
doi: 10.13204/j.gyjzG20090301
Abstract:
Through the high temperature test of the concrete after carbonization, the change rules of carbonization depth, mass loss, compressive strength and flexural strength were studied; the degradation mechanism of the mechanical properties of concrete after high-temperature carbonization was analyzed; the calculation formulas of compressive strength and flexural strength based on the mass loss ratios of concrete at high temperatures after carbonization were established. The results showed that with the continuons carbonization of concrete, the carbonization depth and mass loss increased; when the carbonization age was 7 d, 14 d, 28 d, the compressive strength of concrete decreased first, then increased and then decreased with the increase of temperature; the peak vale of the compressive strength of concrete with carbonization age of 14 d or 28 d appeared at 400 ℃; the general trend of the flexural strength of concrete decreased with the increasing temperature, but when the carbonization age was 14 d or 28 d and the temperature was 200 ℃, its flexural strength would increase slightly; the calculation fomulas of the compressive strength and flexural strength based on the mass loss ratios of concrete could be used to predict the compressive strength and flexural strength of concrete at different carbonization ages and different temperatures.
Through the high temperature test of the concrete after carbonization, the change rules of carbonization depth, mass loss, compressive strength and flexural strength were studied; the degradation mechanism of the mechanical properties of concrete after high-temperature carbonization was analyzed; the calculation formulas of compressive strength and flexural strength based on the mass loss ratios of concrete at high temperatures after carbonization were established. The results showed that with the continuons carbonization of concrete, the carbonization depth and mass loss increased; when the carbonization age was 7 d, 14 d, 28 d, the compressive strength of concrete decreased first, then increased and then decreased with the increase of temperature; the peak vale of the compressive strength of concrete with carbonization age of 14 d or 28 d appeared at 400 ℃; the general trend of the flexural strength of concrete decreased with the increasing temperature, but when the carbonization age was 14 d or 28 d and the temperature was 200 ℃, its flexural strength would increase slightly; the calculation fomulas of the compressive strength and flexural strength based on the mass loss ratios of concrete could be used to predict the compressive strength and flexural strength of concrete at different carbonization ages and different temperatures.
2022, 52(2): 144-150.
doi: 10.13204/j.gyjzG21101408
Abstract:
The track of National Sliding Centre is a long linear space hyperbolic panel shell structure, which cannot be realized by conventional concrete construction techniques, so shotcrete is used for the track structure. As the domestic existing shotcrete adopted the mixing accelerator injection method and the setting time was short, it might cause track roughness to not meet the planeness requirements of millimeter-grade on the track surface. Based on a large number of tests, an accelerator system of high compactness, good pumping performances, cohesive performances for shotcrete was obtained, which was applied in the construction of the tracts for the National Sliding Centre. The application practice proved that the structure of shotcrete system could well meet the construction requirements of millimeter-grade track surface modification.
The track of National Sliding Centre is a long linear space hyperbolic panel shell structure, which cannot be realized by conventional concrete construction techniques, so shotcrete is used for the track structure. As the domestic existing shotcrete adopted the mixing accelerator injection method and the setting time was short, it might cause track roughness to not meet the planeness requirements of millimeter-grade on the track surface. Based on a large number of tests, an accelerator system of high compactness, good pumping performances, cohesive performances for shotcrete was obtained, which was applied in the construction of the tracts for the National Sliding Centre. The application practice proved that the structure of shotcrete system could well meet the construction requirements of millimeter-grade track surface modification.
2022, 52(2): 151-157.
doi: 10.13204/j.gyjzG21042809
Abstract:
A new type of high-strength high-ductility corrosion-resistant rebars—Negative Poisson Ratio(NPR) has been developed independently in China. The bond properties of concrete with NPR rebars were studied by central pull-out tests. The failure modes of the specimens were observed, and the effects of rebar types (NPR rebars, ordinary rebars), rebar diameters (8, 18 mm) and bond lengths (5 or 7 times the diameter of rebars) on the bond strength and bond slip curves were analyzed. The test results showed that the rebar type had no obvious effect on the failure mode, but it had obvious effect on the bond-slip curve. When other conditions were the same, the bond strength of NPR rebars was lower than that of ordinary rebars, and the influence laws of rebar diameters and bond length on the bond strength of two kinds of rebars were similar.
A new type of high-strength high-ductility corrosion-resistant rebars—Negative Poisson Ratio(NPR) has been developed independently in China. The bond properties of concrete with NPR rebars were studied by central pull-out tests. The failure modes of the specimens were observed, and the effects of rebar types (NPR rebars, ordinary rebars), rebar diameters (8, 18 mm) and bond lengths (5 or 7 times the diameter of rebars) on the bond strength and bond slip curves were analyzed. The test results showed that the rebar type had no obvious effect on the failure mode, but it had obvious effect on the bond-slip curve. When other conditions were the same, the bond strength of NPR rebars was lower than that of ordinary rebars, and the influence laws of rebar diameters and bond length on the bond strength of two kinds of rebars were similar.
2022, 52(2): 158-168.
doi: 10.13204/j.gyjzG21121405
Abstract:
In recent years, China has vigorously promoted prefabricated structures, and prefabricated concrete frame structures are currently one of the most researched and applied structural systems at home and abroad. The core of the research is the form and performance of the beam-column connection joint. The traditional prefabricated dry connection joint has the advantages of good performance and reduced on-site wet construction; while the self-centering structure can not only achieve basically no residual deformation after the earthquake, but also achieve the advantages of rapid recovery after the earthquake and put into normal use. Therefore, the form of prefabricated connection joints and the construction method of a bolted connection with beam shoes were introduced; and the research status of the self-centering structures at home and abroad were sumnarized from three aspects: self-centering concrete structures, self-centering steel structures and displacement-based design methods.
In recent years, China has vigorously promoted prefabricated structures, and prefabricated concrete frame structures are currently one of the most researched and applied structural systems at home and abroad. The core of the research is the form and performance of the beam-column connection joint. The traditional prefabricated dry connection joint has the advantages of good performance and reduced on-site wet construction; while the self-centering structure can not only achieve basically no residual deformation after the earthquake, but also achieve the advantages of rapid recovery after the earthquake and put into normal use. Therefore, the form of prefabricated connection joints and the construction method of a bolted connection with beam shoes were introduced; and the research status of the self-centering structures at home and abroad were sumnarized from three aspects: self-centering concrete structures, self-centering steel structures and displacement-based design methods.
2022, 52(2): 169-174,185.
doi: 10.13204/j.gyjzG20121405
Abstract:
As an indispensable storage structure for renewable energy, the safety of hot water storage tank is of great significance. In order to test the rationality of the tank design and the safety of the tank during operation, the field strain and temperature are collected. The design scheme of health monitoring is particularly important in the whole monitoring process. Based on the Tongliao hot water storage engery tank project, combined with the actual situation of the project, a reasonable monitoring scheme was designed, according to the data processing results, the stress distribution and temperature change of the tank wall along the height direction could be obtained, and the influence of temperature on the strain at the measuring point could be obtained. By comparing the measured stress values with the finite element simulation results, the correctness of the theoretical analysis and the rationality of the monitoring scheme were verified, and suggestions were put forward for the establishment of the numerical model of the non-anchored vertical storage tank.
As an indispensable storage structure for renewable energy, the safety of hot water storage tank is of great significance. In order to test the rationality of the tank design and the safety of the tank during operation, the field strain and temperature are collected. The design scheme of health monitoring is particularly important in the whole monitoring process. Based on the Tongliao hot water storage engery tank project, combined with the actual situation of the project, a reasonable monitoring scheme was designed, according to the data processing results, the stress distribution and temperature change of the tank wall along the height direction could be obtained, and the influence of temperature on the strain at the measuring point could be obtained. By comparing the measured stress values with the finite element simulation results, the correctness of the theoretical analysis and the rationality of the monitoring scheme were verified, and suggestions were put forward for the establishment of the numerical model of the non-anchored vertical storage tank.
2022, 52(2): 175-179,195.
doi: 10.13204/j.gyjzG21042001
Abstract:
Aiming at the low efficiency of manual batch inspection for high-strength bolts steel bridge and the high cost of contact sensing equipment, a detection method for the loosening of high strength bolts based on image recognition was proposed. Through the recognition algorithm for the position of bolt corner, the bolt pattern samples were processed by constructing white mask, removing small noise and segmenting ROI of the region of interest to determine the position coordinates of bolt corner. The bolt loosening angle was calculated by using the camera imaging similarity mapping principle, and the preload loss was evaluated according to the relation between the loosening angle and the preload. Then specimens were collected by rotating 10°, 20°, and 30°of different types of bolts at different horizontal viewing angles, and inputed them into the algorithm for experimental verification.The results showed that the accuracy of bolt looseness detection based on the method was over 90%, which could meet the requirements of engineering inspection and effectively evaluate the loss of preload of high-strength bolts.
Aiming at the low efficiency of manual batch inspection for high-strength bolts steel bridge and the high cost of contact sensing equipment, a detection method for the loosening of high strength bolts based on image recognition was proposed. Through the recognition algorithm for the position of bolt corner, the bolt pattern samples were processed by constructing white mask, removing small noise and segmenting ROI of the region of interest to determine the position coordinates of bolt corner. The bolt loosening angle was calculated by using the camera imaging similarity mapping principle, and the preload loss was evaluated according to the relation between the loosening angle and the preload. Then specimens were collected by rotating 10°, 20°, and 30°of different types of bolts at different horizontal viewing angles, and inputed them into the algorithm for experimental verification.The results showed that the accuracy of bolt looseness detection based on the method was over 90%, which could meet the requirements of engineering inspection and effectively evaluate the loss of preload of high-strength bolts.
2022, 52(2): 180-185.
doi: 10.13204/j.gyjzG21041612
Abstract:
Bridge informatization methods based on BIM have been more and more widely used in the process of bridge construction and operation management. In order to solve the problems of unintuitive and unjustified disease analysis caused by the deficiency in disease location, type, and information data collected during the detection process, and to provide new innovative ideas for bridge detection technology, a rigid frame bridge was taken as an example, a method was proposed to achieve disease severity classification analysis and disease management based on BIM technology. A model considering the structural ontology model and the rehabilitation model was established, the automatic generation of cracks and disease information and the addition of attribute information could be realized, so as to achieve further analysis of crack direction, the time distribution of diseases, and the crack distribution along the longitudinal bridge segments direction, and output tables and charts to visually express the statistical analysis results. The BIM model data of the concerned part was extracted and imported into ABAQUS for solid finite element analysis. The calculation results were consistent with the preliminary analysis conclusions. At the same time, the calculated results were correlated with the BIM model in the form of parameters, table mapping, and hyperlinks to realize the integration of multi-source data.
Bridge informatization methods based on BIM have been more and more widely used in the process of bridge construction and operation management. In order to solve the problems of unintuitive and unjustified disease analysis caused by the deficiency in disease location, type, and information data collected during the detection process, and to provide new innovative ideas for bridge detection technology, a rigid frame bridge was taken as an example, a method was proposed to achieve disease severity classification analysis and disease management based on BIM technology. A model considering the structural ontology model and the rehabilitation model was established, the automatic generation of cracks and disease information and the addition of attribute information could be realized, so as to achieve further analysis of crack direction, the time distribution of diseases, and the crack distribution along the longitudinal bridge segments direction, and output tables and charts to visually express the statistical analysis results. The BIM model data of the concerned part was extracted and imported into ABAQUS for solid finite element analysis. The calculation results were consistent with the preliminary analysis conclusions. At the same time, the calculated results were correlated with the BIM model in the form of parameters, table mapping, and hyperlinks to realize the integration of multi-source data.
2022, 52(2): 196-205.
doi: 10.13204/j.gyjzG20102903
Abstract:
This article took prefabricated construction as the research object, through the analysis of the relationship between the various factors, the corresponding system dynamics model was established, and took the example of Jinan city. And then, dynamic simulation of prefabricated construction development and the energy-conservation and emission-reduction(ECER) benefits under different policy scenarios was carried out. Then, the influence of changes in policy types and implementation intensity on its development trend was analyzed. The results show that, on the one hand, the efficiency of energy conservation and emission reduction of prefabricated buildings has not been fully brought into play, and strengthening policy implementation is conducive to further expanding its social and economic benefits. On the other hand, different policies have different effects on the development of prefabricated buildings and their energy conservation and emission reduction benefits. Among them, technology policy has the most significant effect. The demand policy, construction policy and fiscal policy also have obvious effects. By contrast, the role of the finance policy, tax policy and other supportive policies’ effects are relatively weak.
This article took prefabricated construction as the research object, through the analysis of the relationship between the various factors, the corresponding system dynamics model was established, and took the example of Jinan city. And then, dynamic simulation of prefabricated construction development and the energy-conservation and emission-reduction(ECER) benefits under different policy scenarios was carried out. Then, the influence of changes in policy types and implementation intensity on its development trend was analyzed. The results show that, on the one hand, the efficiency of energy conservation and emission reduction of prefabricated buildings has not been fully brought into play, and strengthening policy implementation is conducive to further expanding its social and economic benefits. On the other hand, different policies have different effects on the development of prefabricated buildings and their energy conservation and emission reduction benefits. Among them, technology policy has the most significant effect. The demand policy, construction policy and fiscal policy also have obvious effects. By contrast, the role of the finance policy, tax policy and other supportive policies’ effects are relatively weak.
2022, 52(2): 206-208.
Abstract:
