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2023 Vol. 53, No. 8
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2023, 53(8): 1-9.
doi: 10.13204/j.gyjzG23010901
Abstract:
In the 1950s, the Danwei housing system represented by industrial residences was the starting point of modern urban housings in China. The production of living space and the shaping of daily norms still largely influence today's city construction and urban life. On the other hand, industrial residences, as supporting facilities for industrial production in New China, are not only important material evidence of socialist construction, but also have extremely high social value in the collective memory and place spirit, and together constitute the integrity of socialist industrial heritage. Through literature review and case analysis, the process of construction and evolution of industrial residences in this period, as well as the mechanism and driving factors affecting the changes were retrieved. Based on the investigation of residential layout and housing design, combined with the political-economic background and iconic cases, four stages of the development of industrial residences in the 1950s were sorted out:inheriting and transition, standardization, localization, and practicing thrift. Based on the understanding of the characteristics of industrial housings in each stage, the research vision was extended to the Soviet prototype, so as to comprehensively grasp the external influencing factors of the evolution of Chinese industrial housings in the 1950s.
In the 1950s, the Danwei housing system represented by industrial residences was the starting point of modern urban housings in China. The production of living space and the shaping of daily norms still largely influence today's city construction and urban life. On the other hand, industrial residences, as supporting facilities for industrial production in New China, are not only important material evidence of socialist construction, but also have extremely high social value in the collective memory and place spirit, and together constitute the integrity of socialist industrial heritage. Through literature review and case analysis, the process of construction and evolution of industrial residences in this period, as well as the mechanism and driving factors affecting the changes were retrieved. Based on the investigation of residential layout and housing design, combined with the political-economic background and iconic cases, four stages of the development of industrial residences in the 1950s were sorted out:inheriting and transition, standardization, localization, and practicing thrift. Based on the understanding of the characteristics of industrial housings in each stage, the research vision was extended to the Soviet prototype, so as to comprehensively grasp the external influencing factors of the evolution of Chinese industrial housings in the 1950s.
2023, 53(8): 10-16.
doi: 10.13204/j.gyjzG22123005
Abstract:
With the acceleration of urbanization, the emphasis in the development of cities is shifted from creating to preserving. The renovation of old-school industrial construction has gained more and more attention because of its special historic value, pragmatic value and landscape value. Among various industrial constructions, silo space is easy to distinguishes from others by its unique industrial features. The paper focused on the researches on the different kinds of silo space renovation and accordingly categorize silo space into mono-cylinder silo warehouse and multi-cylinder silo warehouse. By combining domestic and foreign cases and analyzing the design schemes of different types of silo warehouses, the strategies of silo warehouse renovation were extracted from the perspectives of space, function, structure, circulation and elevation.
With the acceleration of urbanization, the emphasis in the development of cities is shifted from creating to preserving. The renovation of old-school industrial construction has gained more and more attention because of its special historic value, pragmatic value and landscape value. Among various industrial constructions, silo space is easy to distinguishes from others by its unique industrial features. The paper focused on the researches on the different kinds of silo space renovation and accordingly categorize silo space into mono-cylinder silo warehouse and multi-cylinder silo warehouse. By combining domestic and foreign cases and analyzing the design schemes of different types of silo warehouses, the strategies of silo warehouse renovation were extracted from the perspectives of space, function, structure, circulation and elevation.
2023, 53(8): 17-24,30.
doi: 10.13204/j.gyjzG22052310
Abstract:
The construction of streets and alleys in old cities corresponds to the behavior of folks living there, and the spatial scales arised from their construction rules generates the perception object of built environments in old cities, for example, the spatial scales of Beijing's hutongs constitute the core of perceiving the history and culture of the old city. With the improvement of preservation of Beijing's old city streets and alleys, to highlight and perpetuat the unique history and culture of the old city, the static maintenance to existing physical forms of the old city has been transfoomed to the dynamic renewal of street space, the control of spatial scales has thus become the basis for continuous dynamic renewal. Unlike directly quantifiable spatial dimensions, spatial scales which contain construction rules, are reflected in folk's subjective perception and have close relations with the speed of the perceiving subject's behavior; sinultaneously, spatial scales also have their constituent elements and rules. The leading part of the construction rules of spatial scales was focused, i.e., the measurement of the subjective perception for spatial scales was studied, and the perceived scales were restricted in the pedestrian environment of street construction. Based on that, two representative residential hutongs in the old city of Beijing were selected as research objects, and virtual reality experiments combined with psychological cognition were conducted on the platform of quantitative modeling through spatial data scanning and element extraction, in order to obtain the measurement for construction rules of spatial scales at walking speed.
The construction of streets and alleys in old cities corresponds to the behavior of folks living there, and the spatial scales arised from their construction rules generates the perception object of built environments in old cities, for example, the spatial scales of Beijing's hutongs constitute the core of perceiving the history and culture of the old city. With the improvement of preservation of Beijing's old city streets and alleys, to highlight and perpetuat the unique history and culture of the old city, the static maintenance to existing physical forms of the old city has been transfoomed to the dynamic renewal of street space, the control of spatial scales has thus become the basis for continuous dynamic renewal. Unlike directly quantifiable spatial dimensions, spatial scales which contain construction rules, are reflected in folk's subjective perception and have close relations with the speed of the perceiving subject's behavior; sinultaneously, spatial scales also have their constituent elements and rules. The leading part of the construction rules of spatial scales was focused, i.e., the measurement of the subjective perception for spatial scales was studied, and the perceived scales were restricted in the pedestrian environment of street construction. Based on that, two representative residential hutongs in the old city of Beijing were selected as research objects, and virtual reality experiments combined with psychological cognition were conducted on the platform of quantitative modeling through spatial data scanning and element extraction, in order to obtain the measurement for construction rules of spatial scales at walking speed.
2023, 53(8): 25-30.
doi: 10.13204/j.gyjzG22062511
Abstract:
In view of the landscape characteristics and natural environment advantages of mountain hotels, from the perspective of interdisciplinary and relevant theories of visual perception, inproving the landscape space quality of mountain hotels through the effective management and guidance of visual perception has gradually become a new content of contemporary mountain hotel design in China. Shiqian Foding Mountain Hot Spring Hotel is not only a work intergrating visual art, landscape design and architecture, but also an exploration of constructing the landscape space characteristics of mountain hotels based on visual perception.Combined with the project practice, starting from the analysis of the categories and characteristics of visual perception, the relation between visual perception and mountain landscape space was explored, and the research perspective to mountain hotel landscape space design was expected to expand from the aspects of sight guidance, control and landscape sequence organization. Eventually, the design methods and strategies of mountain hotel landscape space based on visual perception were discussed, so as to provide valuable reference to the current landscape creation of mountain hotels.
In view of the landscape characteristics and natural environment advantages of mountain hotels, from the perspective of interdisciplinary and relevant theories of visual perception, inproving the landscape space quality of mountain hotels through the effective management and guidance of visual perception has gradually become a new content of contemporary mountain hotel design in China. Shiqian Foding Mountain Hot Spring Hotel is not only a work intergrating visual art, landscape design and architecture, but also an exploration of constructing the landscape space characteristics of mountain hotels based on visual perception.Combined with the project practice, starting from the analysis of the categories and characteristics of visual perception, the relation between visual perception and mountain landscape space was explored, and the research perspective to mountain hotel landscape space design was expected to expand from the aspects of sight guidance, control and landscape sequence organization. Eventually, the design methods and strategies of mountain hotel landscape space based on visual perception were discussed, so as to provide valuable reference to the current landscape creation of mountain hotels.
2023, 53(8): 31-37,95.
doi: 10.13204/j.gyjzG22080212
Abstract:
In-plane seismic performance of the reinforced reinforced concrete (RC) frame-cladding panel structural system after the earthquake was experimentally assessed herein. Two full-scale two-story seismic-damaged RC frames with different cladding panels were repaired by carbon fiber reinforced plastics (CFRP) sheets and steel plates. Quasi-static loading was imposed on the test specimens so as to comprehensively evaluate the bearing capacity, stiffness degradation, energy consumption capacity and failure patterns. Compared with the original structure, the horizontal shear forces of the two repaired structures were increased by 21.8% and 11.2%, respectively, when the inter-story drift ratios were 2.0%. The inter-story drift ratios were increased to 3.3% and 2.5%, respectively. The results showed that the repaired and reinforced cladding panel continued to provide support for the damaged RC frame under the rarely occurred earthquake as the second line of defence, and could improve the seismic performance of the strucatre. The enclosure wall could provide additional stiffness to the main structure under the rarely earthquake and slow down the stiffness degradation of the structure, which made the structure had better anti-collapse redundancy. Compared with concrete cladding panels, the connections of light steel-framed cladding panels were less damaged, which indicated that cladding panels with light weight could alleviate the seismic damage, improve the deformation capacity of the whole structure, and was easier to repair after the earthquake. The research results could provide scientific basis for the seismic performance of reinforced RC frame-cladding panel structural system after the earthquake.
In-plane seismic performance of the reinforced reinforced concrete (RC) frame-cladding panel structural system after the earthquake was experimentally assessed herein. Two full-scale two-story seismic-damaged RC frames with different cladding panels were repaired by carbon fiber reinforced plastics (CFRP) sheets and steel plates. Quasi-static loading was imposed on the test specimens so as to comprehensively evaluate the bearing capacity, stiffness degradation, energy consumption capacity and failure patterns. Compared with the original structure, the horizontal shear forces of the two repaired structures were increased by 21.8% and 11.2%, respectively, when the inter-story drift ratios were 2.0%. The inter-story drift ratios were increased to 3.3% and 2.5%, respectively. The results showed that the repaired and reinforced cladding panel continued to provide support for the damaged RC frame under the rarely occurred earthquake as the second line of defence, and could improve the seismic performance of the strucatre. The enclosure wall could provide additional stiffness to the main structure under the rarely earthquake and slow down the stiffness degradation of the structure, which made the structure had better anti-collapse redundancy. Compared with concrete cladding panels, the connections of light steel-framed cladding panels were less damaged, which indicated that cladding panels with light weight could alleviate the seismic damage, improve the deformation capacity of the whole structure, and was easier to repair after the earthquake. The research results could provide scientific basis for the seismic performance of reinforced RC frame-cladding panel structural system after the earthquake.
2023, 53(8): 38-42.
doi: 10.13204/j.gyjzG22031303
Abstract:
The pull-out resistance of stainless steel connectors of precast concrete sandwich walls was studied in the paper. Four kinds of connectors with different end anchoring structures were designed, and the pull-out resistance, failure mode and load-displacement curve were studied. The results showed that the failure modes of the specimens were mainly concrete cone pulled out. The pull-out resistance of the specimens was more than 20 kN. Based on the existing theoretical model, the pull-out resistance of the stainless steel connectors was calculated and compared with the test results. The test value was 1.6 times more than the design value, four kinds of stainless steel connectors all showed good safety reserves.
The pull-out resistance of stainless steel connectors of precast concrete sandwich walls was studied in the paper. Four kinds of connectors with different end anchoring structures were designed, and the pull-out resistance, failure mode and load-displacement curve were studied. The results showed that the failure modes of the specimens were mainly concrete cone pulled out. The pull-out resistance of the specimens was more than 20 kN. Based on the existing theoretical model, the pull-out resistance of the stainless steel connectors was calculated and compared with the test results. The test value was 1.6 times more than the design value, four kinds of stainless steel connectors all showed good safety reserves.
2023, 53(8): 43-51.
doi: 10.13204/j.gyjzG22042807
Abstract:
A novel type of joint between steel beam and reinforced concrete column was proposed. The joint connected steel beam with prefabricated concrete column through the joint ring composed of square steel tube and ribbed plates. The inner ribbed plates of joint can be integral and separated. The static and seismic ferformance of joint with through-type ribbed plates and joint with separated-type ribbed plates were studied by monotonic and cyclic loading tests on full-scale specimens, and the corresponding ABAQUS finite element simulation was carried out. It was shown that under the monotonic loading, the failure mode of joint with through-type ribbed plates is the tension cracks at the welds of the tension flange of steel beam and square steel tube, and the joint with separated-type ribbed plates was local bucking appeared in the compression flange of steel beam and the plastic hinge formed. Compared with the joint with though-type ribbed plates, the displacement ductility ratio and bearing capacity of the joint with separated-type ribbed plates were increased by 38.24% and 22.33%, the ductility and bearing capacity were better. The failure modes of two joints under the cyclic loading both were the failure of the concrete crushed in the interior part of joint. The stiffness degradation of the joints was stable. The displacement ductility ratio and the energy dissipation coefficient of the joint with separated-type ribbed plates were increased by 21.76% and 35.05%, the ductility and energy dissipating capacity were better. The finite element models could accurately simulate the static behavior of joint under monotonic load, as well as the seismic performance under cyclic load.
A novel type of joint between steel beam and reinforced concrete column was proposed. The joint connected steel beam with prefabricated concrete column through the joint ring composed of square steel tube and ribbed plates. The inner ribbed plates of joint can be integral and separated. The static and seismic ferformance of joint with through-type ribbed plates and joint with separated-type ribbed plates were studied by monotonic and cyclic loading tests on full-scale specimens, and the corresponding ABAQUS finite element simulation was carried out. It was shown that under the monotonic loading, the failure mode of joint with through-type ribbed plates is the tension cracks at the welds of the tension flange of steel beam and square steel tube, and the joint with separated-type ribbed plates was local bucking appeared in the compression flange of steel beam and the plastic hinge formed. Compared with the joint with though-type ribbed plates, the displacement ductility ratio and bearing capacity of the joint with separated-type ribbed plates were increased by 38.24% and 22.33%, the ductility and bearing capacity were better. The failure modes of two joints under the cyclic loading both were the failure of the concrete crushed in the interior part of joint. The stiffness degradation of the joints was stable. The displacement ductility ratio and the energy dissipation coefficient of the joint with separated-type ribbed plates were increased by 21.76% and 35.05%, the ductility and energy dissipating capacity were better. The finite element models could accurately simulate the static behavior of joint under monotonic load, as well as the seismic performance under cyclic load.
2023, 53(8): 52-57.
doi: 10.13204/j.gyjzG20062103
Abstract:
60 sets of 180 specimens were designed and manufactured to verify the reliability of the splice in which the rebars lapped in spiral stirrups confined grout-gilled corrugated pipes. The specimen parameters include longitudinal reinforcement diameter, concrete strength, and spiral rebar diameter and screw pitch. The monotonic tension loading test results indicated that the ultimate tensile strength of specimens all exceeded the 150 percent of the specified yielding strength and 110 percent of specified tensile strength of the lapped rebars. For the splice specimens with lapped rebar diameters of 10 mm and 12 mm, the effect of the spiral stirrups on the tensile strength of the splice specimens was not obvious. For the specimens with a rebar diameter of 14 mm, larger volume ratio and smaller screw pitch of the spiral stirrups could result in less damage of the concrete block under tension load. For a similar reinforcement ratio, it was recommended to use a smaller rebar diameter and screw pitch. When the spiral configuration was d4@50 and the nominal diameter of the longitudinal reinforcement was not more than 14 mm, the lap length could be taken as the basic anchorage length of rebar.
60 sets of 180 specimens were designed and manufactured to verify the reliability of the splice in which the rebars lapped in spiral stirrups confined grout-gilled corrugated pipes. The specimen parameters include longitudinal reinforcement diameter, concrete strength, and spiral rebar diameter and screw pitch. The monotonic tension loading test results indicated that the ultimate tensile strength of specimens all exceeded the 150 percent of the specified yielding strength and 110 percent of specified tensile strength of the lapped rebars. For the splice specimens with lapped rebar diameters of 10 mm and 12 mm, the effect of the spiral stirrups on the tensile strength of the splice specimens was not obvious. For the specimens with a rebar diameter of 14 mm, larger volume ratio and smaller screw pitch of the spiral stirrups could result in less damage of the concrete block under tension load. For a similar reinforcement ratio, it was recommended to use a smaller rebar diameter and screw pitch. When the spiral configuration was d4@50 and the nominal diameter of the longitudinal reinforcement was not more than 14 mm, the lap length could be taken as the basic anchorage length of rebar.
2023, 53(8): 58-64,205.
doi: 10.13204/j.gyjzG21020703
Abstract:
In order to understand the seismic performance and failure mechanism of the prefabricated eccentrically braced steel frame under earthquake action, a quasi-static test was conducted on a one-storey single-span prefabricated eccentrically braced steel frame. The effect of the connection structure of energy dissipating beam section on the seismic performance of prefabricated eccentrically braced steel frames was studied. The failure characteristics of the steel frame under quasi-static load were observed, and combined the test results to deeply analyze the seismic performance indicators such as hysteresis curve, skeleton curve, stiffness degradation, energy dissipation performance, ductility coefficient of this type of structure. The test results showed that this type of prefabricated eccentrically braced steel frame had good seismic performance, and the connection structure of the energy dissipating beam section had an important influence on the prefabricated eccentrically braced steel frame. When the main frame connection form remained unchanged, the frame energy dissipating beam sections connected by extended end plates, the bearing capacity and energy dissipation capacity of the specimen connected by extended end plate were higher than the specimen connected by flush end plates; the failure of the two frames appearred in the energy dissipating beam section, and there was no obvious deformation on the main frame which could meet the seismic fortification requirements of buildings.
In order to understand the seismic performance and failure mechanism of the prefabricated eccentrically braced steel frame under earthquake action, a quasi-static test was conducted on a one-storey single-span prefabricated eccentrically braced steel frame. The effect of the connection structure of energy dissipating beam section on the seismic performance of prefabricated eccentrically braced steel frames was studied. The failure characteristics of the steel frame under quasi-static load were observed, and combined the test results to deeply analyze the seismic performance indicators such as hysteresis curve, skeleton curve, stiffness degradation, energy dissipation performance, ductility coefficient of this type of structure. The test results showed that this type of prefabricated eccentrically braced steel frame had good seismic performance, and the connection structure of the energy dissipating beam section had an important influence on the prefabricated eccentrically braced steel frame. When the main frame connection form remained unchanged, the frame energy dissipating beam sections connected by extended end plates, the bearing capacity and energy dissipation capacity of the specimen connected by extended end plate were higher than the specimen connected by flush end plates; the failure of the two frames appearred in the energy dissipating beam section, and there was no obvious deformation on the main frame which could meet the seismic fortification requirements of buildings.
2023, 53(8): 65-73.
doi: 10.13204/j.gyjzG21051009
Abstract:
In order to study the overall response and damage form of a cold-formed thin-walled steel housing structure under earthquake, the pseudo-dynamic test was carried out on a full-scale model with a height of 3m, analyzing the displacement response, hysteretic performance, stiffness degradation and the failure form of wall skeleton under earthquake action, and the evaluation method of the damage degree of the skeleton was introduced, which could provide a reference for the evaluation of the damage degree of the cold-formed steel buildings. The research showed that the failure mode of joints of in-plane wall parallel to the loading direction were mostly bending and torsion failure, and the arrangement mode of diagonal braces had a great influence on the distribution of internal forces of the structure, which should be considered in the design. The middle row of joints in the walls parallel to the loading direction and the entrance of doors and windows were the most vulnerable positions of the structure, and it was suggested to improve the bearing capacity of the joint by adding the reinforcer to improve the integrity of the flange of the transverse bar at the opening of joint or changing the arrangement of diagonal braces. Under the El Centro wave and Northridge wave, the failure state of the vertical members of the structure was divided according to the reference control value of the maximum inter-storey displacement angle given in the current Code for Seismic Design of Buildings (GB 50011-2010), which could be also applicable to the cold-formed thin-walled steel structure system. The maximum inter-storey displacement angle of the structure under the action of each seismic wave did not exceed the limit value specified in the code, meeting the design goal of "small earthquake is not bad, middle earthquake can repair, big earthquake does not fall".
In order to study the overall response and damage form of a cold-formed thin-walled steel housing structure under earthquake, the pseudo-dynamic test was carried out on a full-scale model with a height of 3m, analyzing the displacement response, hysteretic performance, stiffness degradation and the failure form of wall skeleton under earthquake action, and the evaluation method of the damage degree of the skeleton was introduced, which could provide a reference for the evaluation of the damage degree of the cold-formed steel buildings. The research showed that the failure mode of joints of in-plane wall parallel to the loading direction were mostly bending and torsion failure, and the arrangement mode of diagonal braces had a great influence on the distribution of internal forces of the structure, which should be considered in the design. The middle row of joints in the walls parallel to the loading direction and the entrance of doors and windows were the most vulnerable positions of the structure, and it was suggested to improve the bearing capacity of the joint by adding the reinforcer to improve the integrity of the flange of the transverse bar at the opening of joint or changing the arrangement of diagonal braces. Under the El Centro wave and Northridge wave, the failure state of the vertical members of the structure was divided according to the reference control value of the maximum inter-storey displacement angle given in the current Code for Seismic Design of Buildings (GB 50011-2010), which could be also applicable to the cold-formed thin-walled steel structure system. The maximum inter-storey displacement angle of the structure under the action of each seismic wave did not exceed the limit value specified in the code, meeting the design goal of "small earthquake is not bad, middle earthquake can repair, big earthquake does not fall".
2023, 53(8): 74-81,160.
doi: 10.13204/j.gyjzG21032303
Abstract:
Because of the multiaxial high-cycle fatigue characteristics of welded spherical joints under wind load, it is necessary to do some research on the wind-induced multiaxial high-cycle fatigue of the joints in order to ensure the wind safety of spatial grid structure. A multiaxial high-cycle fatigue analysis methodology was proposed. Firstly, the high-cycle fatigue tests of weldments under uniaxial and multiaxial loading were carried out, and obtained the multiaxial high-cycle fatigue damage life model of weldments based on two-parameter critical surface method. Secondly, based on the wind tunnel test data,the wind-induced response of the grid structure was analyzed, meanwhile, the refined finite element model of the welded joints was established by using the substructure analysis method, so as to obtain the stress time-history and equivalent stress time-history of the dangerous points of each welded joint. The rainfall counts were then performed to determine the starting and ending points of each cycle and its original stress time-history, accordingly identify the critical surfaces in each cycle by using the search method. Finally, based on the multiaxial high-cycle fatigue damage life model obtained in the test, and the cumulative fatigue damage values of all the cycles were calculated according to Miner's linear accumulation criterion, on the basis of which the starting life of the joint was predicted when fatigue damage occurred. The wind-induced fatigue analysis was carried out on the joints of the roof grid structure of Wuhan Natatorium at different locations. The results indicated that the fatigue damage starting life of the windward joints, leeward joints and intermediate joints was far less than the service life of the structure. Therefore, wind-induced fatigue damage might occur on the welded joints within the service life of structure, which should be concerned in the engineering field.
Because of the multiaxial high-cycle fatigue characteristics of welded spherical joints under wind load, it is necessary to do some research on the wind-induced multiaxial high-cycle fatigue of the joints in order to ensure the wind safety of spatial grid structure. A multiaxial high-cycle fatigue analysis methodology was proposed. Firstly, the high-cycle fatigue tests of weldments under uniaxial and multiaxial loading were carried out, and obtained the multiaxial high-cycle fatigue damage life model of weldments based on two-parameter critical surface method. Secondly, based on the wind tunnel test data,the wind-induced response of the grid structure was analyzed, meanwhile, the refined finite element model of the welded joints was established by using the substructure analysis method, so as to obtain the stress time-history and equivalent stress time-history of the dangerous points of each welded joint. The rainfall counts were then performed to determine the starting and ending points of each cycle and its original stress time-history, accordingly identify the critical surfaces in each cycle by using the search method. Finally, based on the multiaxial high-cycle fatigue damage life model obtained in the test, and the cumulative fatigue damage values of all the cycles were calculated according to Miner's linear accumulation criterion, on the basis of which the starting life of the joint was predicted when fatigue damage occurred. The wind-induced fatigue analysis was carried out on the joints of the roof grid structure of Wuhan Natatorium at different locations. The results indicated that the fatigue damage starting life of the windward joints, leeward joints and intermediate joints was far less than the service life of the structure. Therefore, wind-induced fatigue damage might occur on the welded joints within the service life of structure, which should be concerned in the engineering field.
2023, 53(8): 82-88,227.
doi: 10.13204/j.gyjzG23052207
Abstract:
In order to study the effect of building decorative strips on the wind load characteristics of long-span roofs, the differences of average wind pressure, pulsating wind pressure, non-Gaussian characteristics of wind pressure and extreme wind pressure under two working conditions were compared based on the results of rigid wind tunnel pressure testing with and without building decorative strips on the surface of long-span roofs. The results showed that the effect of decorative building decorative strips on wind load was related to the wind angle, and the direction perpendicular to the building decorative strips would increase the average wind pressure and pulsating wind pressure coefficients, where the flow separation of the roof occurred. It would change the Gaussian characteristics of some measurement points, so that about 10% of Gaussian measurement points were converted into non-Gaussian measurement points. The direction parallel to the building decorative strips would increase the extreme negative pressure at the edge of the side roof and the middle of the roof. In general, the building decorative strips did not change the wind load mechanism of the roof mainly by negative pressure, but they increased the most unfavorable extreme negative pressure, especially at some edges by 42%, which was extremely unfavorable to the wind resistance design of the enclosure.
In order to study the effect of building decorative strips on the wind load characteristics of long-span roofs, the differences of average wind pressure, pulsating wind pressure, non-Gaussian characteristics of wind pressure and extreme wind pressure under two working conditions were compared based on the results of rigid wind tunnel pressure testing with and without building decorative strips on the surface of long-span roofs. The results showed that the effect of decorative building decorative strips on wind load was related to the wind angle, and the direction perpendicular to the building decorative strips would increase the average wind pressure and pulsating wind pressure coefficients, where the flow separation of the roof occurred. It would change the Gaussian characteristics of some measurement points, so that about 10% of Gaussian measurement points were converted into non-Gaussian measurement points. The direction parallel to the building decorative strips would increase the extreme negative pressure at the edge of the side roof and the middle of the roof. In general, the building decorative strips did not change the wind load mechanism of the roof mainly by negative pressure, but they increased the most unfavorable extreme negative pressure, especially at some edges by 42%, which was extremely unfavorable to the wind resistance design of the enclosure.
2023, 53(8): 89-95.
doi: 10.13204/j.gyjzG21100706
Abstract:
In order to study the welding residual stress level and distribution law of joints between 6061-T6 aluminum alloy box-columns and H-shaped beams, the finite element software was used to establish the models of beam-column joints reinforced with cover plates, ordinary beam-column joints with column diaphragms, and ordinary beam-column joints without column diaphragms. The indirect thermo-mechanical coupling method was used to carry out the numerical simulation of T-shaped fully penetrated weld welding of the joints, and the finite element model was verified. The results showed that the middle part of longitudinal welding residual stress of the beam flange butt weld and the web butt weld of each joint was about 250 MPa, and the welding residual stress at both ends of the weld tended to 0 MPa. The transverse residual stress of each joint weld was tensile in the middle and was compressed at both ends. The transverse residual stress of the strengthened joint butt weld along the beam-column flange tended to 0 MPa, but the peak value of the ordinary joint was about 240 MPa. The residual stresses at the fillet weld of the cover plate of reinforced joint were tensile stresses, and the overall welding residual stresses were low. The overall results showed that the welding residual stress generated at the weld was large, and the welding residual stress at the butt weld of the web butt weld and the beam-column flange butt weld had reached the yield strength of 6061-T6 aluminum alloy. At the same time, the residual deformation of the upper and lower flanges of the beam concave in the direction of the web of the beam occurred at each joint.
In order to study the welding residual stress level and distribution law of joints between 6061-T6 aluminum alloy box-columns and H-shaped beams, the finite element software was used to establish the models of beam-column joints reinforced with cover plates, ordinary beam-column joints with column diaphragms, and ordinary beam-column joints without column diaphragms. The indirect thermo-mechanical coupling method was used to carry out the numerical simulation of T-shaped fully penetrated weld welding of the joints, and the finite element model was verified. The results showed that the middle part of longitudinal welding residual stress of the beam flange butt weld and the web butt weld of each joint was about 250 MPa, and the welding residual stress at both ends of the weld tended to 0 MPa. The transverse residual stress of each joint weld was tensile in the middle and was compressed at both ends. The transverse residual stress of the strengthened joint butt weld along the beam-column flange tended to 0 MPa, but the peak value of the ordinary joint was about 240 MPa. The residual stresses at the fillet weld of the cover plate of reinforced joint were tensile stresses, and the overall welding residual stresses were low. The overall results showed that the welding residual stress generated at the weld was large, and the welding residual stress at the butt weld of the web butt weld and the beam-column flange butt weld had reached the yield strength of 6061-T6 aluminum alloy. At the same time, the residual deformation of the upper and lower flanges of the beam concave in the direction of the web of the beam occurred at each joint.
2023, 53(8): 96-101,57.
doi: 10.13204/j.gyjzG22102505
Abstract:
In order to study the influence of high temperature environment on the lifting process of complex long-span space structures, the connecting steel roof of Minqin County Sports Center was used as the engineering background. The whole process of lifting construction of a double-layer reticulated shell was simulated and monitored. The influence of temperature on the stress and deformation of the structure during lifting and supporting of the frame was discussed. The comparison between the calculated values and the monitored values verified the rationality of the numerical simulation method considering the influence of temperature. At the same time, based on the method of increasing the load effect and considering the effect of increased measured stress on local members, the values of the increase coefficient of the load effect in numerical simulation with and without considering temperature effect were presented.
In order to study the influence of high temperature environment on the lifting process of complex long-span space structures, the connecting steel roof of Minqin County Sports Center was used as the engineering background. The whole process of lifting construction of a double-layer reticulated shell was simulated and monitored. The influence of temperature on the stress and deformation of the structure during lifting and supporting of the frame was discussed. The comparison between the calculated values and the monitored values verified the rationality of the numerical simulation method considering the influence of temperature. At the same time, based on the method of increasing the load effect and considering the effect of increased measured stress on local members, the values of the increase coefficient of the load effect in numerical simulation with and without considering temperature effect were presented.
2023, 53(8): 102-106.
doi: 10.13204/j.gyjzG21030817
Abstract:
The coating of steel bridge has a significant impact and interference on fatigue crack detection. In order to improve the detection efficiency and evaluation accuracy of fatigue cracks, the experimental research on Alternating Current Field Measurement (ACFM) technique was carried out to realize the rapid scanning and quantitative evaluation of fatigue cracks without removing the coating. Firstly, aiming at the coating interference on fatigue crack detection, the influence of typical coating systems on identification and evaluation of steel bridge fatigue crack was explored. Secondly, considering the shielding effect of existing coating on fatigue cracks, the sensitivity of ACFM to the detection of hidden fatigue cracks was verified. Finally, detection and evaluation accuracy of ACFM were analyzed through the test for comparative specimens and painted specimens. The results showed that ACFM could accurately identify and quantitatively evaluate fatigue cracks under the coating. The crack detection ratio reached 100%, and the quantitative evaluation accuracy of crack length reached more than 95%. The influence of coating system type and coating shadowing effect on ACFM detection for fatigue cracks was not obvious. ACFM technology showed a good detection capacity for fatigue cracks with different lengths, and could realize effective detection and accurate evaluation of fatigue cracks in different states during fatigue crack propagation.
The coating of steel bridge has a significant impact and interference on fatigue crack detection. In order to improve the detection efficiency and evaluation accuracy of fatigue cracks, the experimental research on Alternating Current Field Measurement (ACFM) technique was carried out to realize the rapid scanning and quantitative evaluation of fatigue cracks without removing the coating. Firstly, aiming at the coating interference on fatigue crack detection, the influence of typical coating systems on identification and evaluation of steel bridge fatigue crack was explored. Secondly, considering the shielding effect of existing coating on fatigue cracks, the sensitivity of ACFM to the detection of hidden fatigue cracks was verified. Finally, detection and evaluation accuracy of ACFM were analyzed through the test for comparative specimens and painted specimens. The results showed that ACFM could accurately identify and quantitatively evaluate fatigue cracks under the coating. The crack detection ratio reached 100%, and the quantitative evaluation accuracy of crack length reached more than 95%. The influence of coating system type and coating shadowing effect on ACFM detection for fatigue cracks was not obvious. ACFM technology showed a good detection capacity for fatigue cracks with different lengths, and could realize effective detection and accurate evaluation of fatigue cracks in different states during fatigue crack propagation.
2023, 53(8): 107-117.
doi: 10.13204/j.gyjzG23030119
Abstract:
Owing to its high stiffness, good stability, relatively fast construction and low maintenance cost, steel-concrete composite structure is often used in the tower support structure of wind turbines. Steel-concrete tower barrel is usually produced and transported in vertical segments. During construction, the vertical grouting joint is formed by secondary pouring of high-strength grouting material. The shear performance of the joint directly affects the overall performance of the tower barrel. Through the static test of four vertical grouting joint specimens of concrete tower barrel under direct shear load, the failure mode and load-slip curve were analyzed, and ABAQUS was used to establish the refined finite element model of vertical grouting joint under pure shear load. The accuracy and applicability of the model were verified by comparing with the test results, which not only verified the influence of ratio of U-shaped shear bars and longitudinal reinforcement on bearing capacity but also laid a foundation for parameter analysis and calculation formula of bearing capacity.
Owing to its high stiffness, good stability, relatively fast construction and low maintenance cost, steel-concrete composite structure is often used in the tower support structure of wind turbines. Steel-concrete tower barrel is usually produced and transported in vertical segments. During construction, the vertical grouting joint is formed by secondary pouring of high-strength grouting material. The shear performance of the joint directly affects the overall performance of the tower barrel. Through the static test of four vertical grouting joint specimens of concrete tower barrel under direct shear load, the failure mode and load-slip curve were analyzed, and ABAQUS was used to establish the refined finite element model of vertical grouting joint under pure shear load. The accuracy and applicability of the model were verified by comparing with the test results, which not only verified the influence of ratio of U-shaped shear bars and longitudinal reinforcement on bearing capacity but also laid a foundation for parameter analysis and calculation formula of bearing capacity.
2023, 53(8): 118-126.
doi: 10.13204/j.gyjzG22100701
Abstract:
A total of 5 specimens, including 3 curved concrete-filled stainless steel tubes (CCFSST), one straight concrete filled stainless steel tube (CFSST) and one curved hollow stainless steel tube (CHSST) were tested to study the effects of initial curvature ratio and infilled concrete on the mechanical poperties of CCFSST under bending. The test results showed that with the increase of initial curvature ratio of specimens, the flexural stiffness and flexural bearing capacity of specimens increased compared with the corresponding hollow stainless steel tubular specimen, the concrete filling in the tube could significantly improve the flexural stiffness and flexural bearing capacity of specimens. The finite element software ABAQUS was used to analyze the mechanical characteristics and load versus midspan deflection curves of CCFSST under bending, and compared with plain carbon steel members. The results of the finite element analysis were in good agreement with the test results in general. Based on the elastic stiffness model, the influence formula of initial curvature ratio on the elastic bending stiffness of CCFSST members was deduced, and the calculated results of the formula were in good agreement with the experimental results. Based on parametric analysis, compared with plain carbon steel members, the bearing capacity of CCFSST members was increased by 10% and the bending stiffness was reduced by 15%, respectively. Using the existing codes for straight concrete-filled steel tubes to calculate the ultimate flexural capacity of CCFSST members, and the modified flexural stiffness formula can be more accurately applied to the design of CFSST.
A total of 5 specimens, including 3 curved concrete-filled stainless steel tubes (CCFSST), one straight concrete filled stainless steel tube (CFSST) and one curved hollow stainless steel tube (CHSST) were tested to study the effects of initial curvature ratio and infilled concrete on the mechanical poperties of CCFSST under bending. The test results showed that with the increase of initial curvature ratio of specimens, the flexural stiffness and flexural bearing capacity of specimens increased compared with the corresponding hollow stainless steel tubular specimen, the concrete filling in the tube could significantly improve the flexural stiffness and flexural bearing capacity of specimens. The finite element software ABAQUS was used to analyze the mechanical characteristics and load versus midspan deflection curves of CCFSST under bending, and compared with plain carbon steel members. The results of the finite element analysis were in good agreement with the test results in general. Based on the elastic stiffness model, the influence formula of initial curvature ratio on the elastic bending stiffness of CCFSST members was deduced, and the calculated results of the formula were in good agreement with the experimental results. Based on parametric analysis, compared with plain carbon steel members, the bearing capacity of CCFSST members was increased by 10% and the bending stiffness was reduced by 15%, respectively. Using the existing codes for straight concrete-filled steel tubes to calculate the ultimate flexural capacity of CCFSST members, and the modified flexural stiffness formula can be more accurately applied to the design of CFSST.
2023, 53(8): 127-134,211.
doi: 10.13204/j.gyjzG22110502
Abstract:
The mechanical properties of bolts and hollow rivet connectors in engineering bamboo structures were studied to provide theoretical and technical support for applying the above connectors in glubam designs. The nominal yield strength and a plastic bending moment of grade 4.8 and 8.8 bolts, hollow rivets of different diameters were tested by using the three-point bending method. The semi-hole method tested the embedment strength of different types of bamboo in the main-fiber and the less-fiber directions. Monotonic and hysteretic tests tested the bearing capacity, stiffness, and ductility of the bamboo-steel-bamboo connections. The bearing capacity values measured by the test were compared with the bearing capacity estimation values through corresponding failure modes, and the appropriate estimation formula was determined. The experimental results showed that bamboo was a brittle engineering material with pronounced anisotropy. The yield failure of steel and the shear failure of bamboo were the main failure modes of bamboo-steel-bamboo connections studied herein. Through proper connector design and cross-laminated strips, the above connectors could form a ductile failure mode dominated by steel yielding. Through the corresponding yield model, the bearing capacity of the bamboo-steel-bamboo connection could be estimated.
The mechanical properties of bolts and hollow rivet connectors in engineering bamboo structures were studied to provide theoretical and technical support for applying the above connectors in glubam designs. The nominal yield strength and a plastic bending moment of grade 4.8 and 8.8 bolts, hollow rivets of different diameters were tested by using the three-point bending method. The semi-hole method tested the embedment strength of different types of bamboo in the main-fiber and the less-fiber directions. Monotonic and hysteretic tests tested the bearing capacity, stiffness, and ductility of the bamboo-steel-bamboo connections. The bearing capacity values measured by the test were compared with the bearing capacity estimation values through corresponding failure modes, and the appropriate estimation formula was determined. The experimental results showed that bamboo was a brittle engineering material with pronounced anisotropy. The yield failure of steel and the shear failure of bamboo were the main failure modes of bamboo-steel-bamboo connections studied herein. Through proper connector design and cross-laminated strips, the above connectors could form a ductile failure mode dominated by steel yielding. Through the corresponding yield model, the bearing capacity of the bamboo-steel-bamboo connection could be estimated.
2023, 53(8): 135-144,117.
doi: 10.13204/j.gyjzG22090806
Abstract:
Small-section wooden frame shear wall is composed of small-section frame columns (end columns), studs and cladding panels. There are few researches on the influence of beam-column connection mode and shear modulus of cladding panel on the lateral resistance of shear wall. The shear modulus characteristic values of different types of cladding panels were obtained through shear modulus test.On this basis, the quasi-static loading test and numerical simulation test were carried out on three walls with metal tenon, inclined nail connection and straight tenon-metal connection, two coniferous plywood walls with different thickness and two OSB board walls with different thickness, the failure mode, average stiffness, average strength, ductility coefficient and stiffness degradation law of the wall were obtained. The results showed that the average stiffness and average bearing capacity of walls with three connections were not significantly different, but the push-pull bidirectional performance of the wall with metal tenon connections was more stable. The characteristic value of the shear modulus of the coniferous plywood was 291.67 MPa, and that of the OSB board was 389.17 MPa; the stiffness and bearing capacity of 12 mm thickness plywood wall were 2.95% and 39.5% higher than those of OSB wall with the same thickness, and the stiffness and bearing capacity of 24 mm thickness plywood wall were 16.39% and 25.1% higher than those of OSB wall with the same thickness, respectively. The results further clarified the main influencing factors for the ateral performance of small-section wood frame shear wall, which could provide important guiding significance for the application and promotion of the system.
Small-section wooden frame shear wall is composed of small-section frame columns (end columns), studs and cladding panels. There are few researches on the influence of beam-column connection mode and shear modulus of cladding panel on the lateral resistance of shear wall. The shear modulus characteristic values of different types of cladding panels were obtained through shear modulus test.On this basis, the quasi-static loading test and numerical simulation test were carried out on three walls with metal tenon, inclined nail connection and straight tenon-metal connection, two coniferous plywood walls with different thickness and two OSB board walls with different thickness, the failure mode, average stiffness, average strength, ductility coefficient and stiffness degradation law of the wall were obtained. The results showed that the average stiffness and average bearing capacity of walls with three connections were not significantly different, but the push-pull bidirectional performance of the wall with metal tenon connections was more stable. The characteristic value of the shear modulus of the coniferous plywood was 291.67 MPa, and that of the OSB board was 389.17 MPa; the stiffness and bearing capacity of 12 mm thickness plywood wall were 2.95% and 39.5% higher than those of OSB wall with the same thickness, and the stiffness and bearing capacity of 24 mm thickness plywood wall were 16.39% and 25.1% higher than those of OSB wall with the same thickness, respectively. The results further clarified the main influencing factors for the ateral performance of small-section wood frame shear wall, which could provide important guiding significance for the application and promotion of the system.
2023, 53(8): 145-153.
doi: 10.13204/j.gyjzG22090117
Abstract:
Stone statues have lasted for a long time and have high cultural value. However, there are few researches on damage characteristics and vibration threshold of such cultural relics under construction disturbance. Based on the reconstruction and expansion project of a museum, and the finite element model was established according to the 1:1 stone statues in the museum. A variety of on-site mechanical construction disturbances were used as vibration excitation to conduct on-site vibration testing, and the incremental dynamic time-history analysis was conducted to study the dynamic response characteristics of stone Buddha statues under different construction disturbances, the damage degree was analyzed, and the vulnerable parts in various ways were determined. The results showed that:the natural vibration frequency of stone statues was close to the high frequency characteristics of construction disturbance, which was easy to be affected by construction disturbance; the excitation intensity was positively correlated with the strain, the maximum tensile stress and the maximum shear stress of the stone statue; the foot and neck of the stone statue were vulnerable parts, which were affected by the excitation much more than the other parts; the permissible particle vibration velocity of 1 mm/s in Blasting Safety Regulations for ancient buildings and historic sites was taken as the upper limit of strength to analyze the time history of stone statues even though the strain, shear stress and tensile stress did not exceed the mechanical properties of the rock material, there was still a risk of cracking of hydraulic lime, a commonly used repair material for stone statues.
Stone statues have lasted for a long time and have high cultural value. However, there are few researches on damage characteristics and vibration threshold of such cultural relics under construction disturbance. Based on the reconstruction and expansion project of a museum, and the finite element model was established according to the 1:1 stone statues in the museum. A variety of on-site mechanical construction disturbances were used as vibration excitation to conduct on-site vibration testing, and the incremental dynamic time-history analysis was conducted to study the dynamic response characteristics of stone Buddha statues under different construction disturbances, the damage degree was analyzed, and the vulnerable parts in various ways were determined. The results showed that:the natural vibration frequency of stone statues was close to the high frequency characteristics of construction disturbance, which was easy to be affected by construction disturbance; the excitation intensity was positively correlated with the strain, the maximum tensile stress and the maximum shear stress of the stone statue; the foot and neck of the stone statue were vulnerable parts, which were affected by the excitation much more than the other parts; the permissible particle vibration velocity of 1 mm/s in Blasting Safety Regulations for ancient buildings and historic sites was taken as the upper limit of strength to analyze the time history of stone statues even though the strain, shear stress and tensile stress did not exceed the mechanical properties of the rock material, there was still a risk of cracking of hydraulic lime, a commonly used repair material for stone statues.
2023, 53(8): 154-160.
doi: 10.13204/j.gyjzG21060304
Abstract:
Taking the structural response of frame structures under earthquake as a constraint, the seismic performance of frame structures with friction dampers was optimized by computer-aided integration technology. Using ABAQUS software, a finite element analysis of frame structures with or without friction dampers was carried out to obtain the displacement and acceleration responses of each layer of the structure. ISIGHT software was integrated with ABAQUS to optimize the mechanical parameters of friction dampers, to obtain the optimal damping design scheme under the condition of deploying the same number of dampers. The results showed that the parameter design method of friction dampers based on an optimization algorithm could effectively optimize the seismic design of the structure, and the application of the process could greatly improve the operability of the automatic optimization design of damper parameters in engineering applications. Univariate optimization and multivariate optimization methods were used respectively, and the optimization results showed that the displacement and acceleration responses of the top layer of the structure were significantly reduced compared with those before optimization.
Taking the structural response of frame structures under earthquake as a constraint, the seismic performance of frame structures with friction dampers was optimized by computer-aided integration technology. Using ABAQUS software, a finite element analysis of frame structures with or without friction dampers was carried out to obtain the displacement and acceleration responses of each layer of the structure. ISIGHT software was integrated with ABAQUS to optimize the mechanical parameters of friction dampers, to obtain the optimal damping design scheme under the condition of deploying the same number of dampers. The results showed that the parameter design method of friction dampers based on an optimization algorithm could effectively optimize the seismic design of the structure, and the application of the process could greatly improve the operability of the automatic optimization design of damper parameters in engineering applications. Univariate optimization and multivariate optimization methods were used respectively, and the optimization results showed that the displacement and acceleration responses of the top layer of the structure were significantly reduced compared with those before optimization.
2023, 53(8): 161-167.
doi: 10.13204/j.gyjzG22061306
Abstract:
Determining the current state of long-span bridges and clarifying the force characteristics of key parts are the prerequisites for evaluating their performance degradation and remaining life. A multi-scale surrogate model for long-span bridges was established by using the Kriging metamodel, and a large-span bridge model update method was developed by using a multi-objective evolutionary algorithm and an evolutionary control algorithm. Taking a typical long-span cable-stayed bridge as an example, a multi-scale finite element model of the long-span cable-stayed bridge was established. The overall structure of the global model adopted beam elements and local shell elements, and the boundary conditions were satisfied by using the multi-point constraint method (MPC). Based on the measured data of the health monitoring system, the natural vibration frequency, displacement response and stress response of the model were corrected, and the corrected influence line was obtained. The results showed that the global and local index correction results obtained by the multi-objective evolutionary algorithm were in good agreement with the measured data. Compared with the initial finite element calculation values, the average relative error of the natural frequency was reduced by 3.38%, and the average relative error of the displacement response was relatively high. The error was reduced by 10% and the average relative error of the stress response was reduced by 5%. In general, the Kriging metamodel and the multi-objective evolutionary algorithm could be used to correct and update the multi-scale model of long-span bridges.
Determining the current state of long-span bridges and clarifying the force characteristics of key parts are the prerequisites for evaluating their performance degradation and remaining life. A multi-scale surrogate model for long-span bridges was established by using the Kriging metamodel, and a large-span bridge model update method was developed by using a multi-objective evolutionary algorithm and an evolutionary control algorithm. Taking a typical long-span cable-stayed bridge as an example, a multi-scale finite element model of the long-span cable-stayed bridge was established. The overall structure of the global model adopted beam elements and local shell elements, and the boundary conditions were satisfied by using the multi-point constraint method (MPC). Based on the measured data of the health monitoring system, the natural vibration frequency, displacement response and stress response of the model were corrected, and the corrected influence line was obtained. The results showed that the global and local index correction results obtained by the multi-objective evolutionary algorithm were in good agreement with the measured data. Compared with the initial finite element calculation values, the average relative error of the natural frequency was reduced by 3.38%, and the average relative error of the displacement response was relatively high. The error was reduced by 10% and the average relative error of the stress response was reduced by 5%. In general, the Kriging metamodel and the multi-objective evolutionary algorithm could be used to correct and update the multi-scale model of long-span bridges.
2023, 53(8): 168-175.
doi: 10.13204/j.gyjzG22052107
Abstract:
Based on gravity anchorage foundations of Ganjiang Highway Bridge situated on weakly weathered argillaceous siltstone, large-scale shear tests on the site were conducted to study shear mechanisms, failure modes, deformation characteristics and shear strength parameters of cemented interfaces, aimed at cemented interfaces with different roughnesses between anchorage foundation concrete and bedrock. Simultaneously, to effectively estimate the effect of cemented surface roughness on shear strength, characteristic parameters of random distribution were firstly introduced to quantify the cemented interface roughness, and the Monte-Carlo method was simulated the undulating pattern of cemented interfaces. Then, numerical simulation analysis on shear tests was implemented to study shear strength with different cemented interface roughnesses. Eventually, a new evaluation method for cemented interface shear strength was proposed based on numerical simulations with random contact interfaces. In addition, the results from numerical simulations were compared with the data by direct shear tests on the site, and the comparison results indicated they were highly consistent.
Based on gravity anchorage foundations of Ganjiang Highway Bridge situated on weakly weathered argillaceous siltstone, large-scale shear tests on the site were conducted to study shear mechanisms, failure modes, deformation characteristics and shear strength parameters of cemented interfaces, aimed at cemented interfaces with different roughnesses between anchorage foundation concrete and bedrock. Simultaneously, to effectively estimate the effect of cemented surface roughness on shear strength, characteristic parameters of random distribution were firstly introduced to quantify the cemented interface roughness, and the Monte-Carlo method was simulated the undulating pattern of cemented interfaces. Then, numerical simulation analysis on shear tests was implemented to study shear strength with different cemented interface roughnesses. Eventually, a new evaluation method for cemented interface shear strength was proposed based on numerical simulations with random contact interfaces. In addition, the results from numerical simulations were compared with the data by direct shear tests on the site, and the comparison results indicated they were highly consistent.
2023, 53(8): 176-183.
doi: 10.13204/j.gyjzG22062201
Abstract:
To study the influence of fillers on the mechanical properties and fracture characteristics of rock specimens with double inclined cavities, the numerical simulation of uniaxial compression was performed by discrete element software PFC2D on rock specimens with double circular cavities filled with different strength fillers at different inclinations. The results indicated that the strength and inclination of fillers had different effects on the strength and deformation characteristics of rock. With the increase of the strength of fillers, the influence of inclinations was gradually weakened. When the filling coefficient λ was 0.6, the reinforcement effect for specimens with inclined cavities was best. When the filling coefficient was greater than 0.6, the strengths of all specimens with indined cavities were almost constant, and all the specimens did not present crack aggregation phenomena between cavities. The failure process of spcimens could be characterized by acoustic emission counting, cumulative acoustic emission counting and location maps. The final failure modes of specimens with different filler strengths could be divided into tensile-shear mixed failure and shear failure. The crack aggregation modes between defects could be divided into non-aggregation, shear aggregation and tensile-shear mixed aggregation.
To study the influence of fillers on the mechanical properties and fracture characteristics of rock specimens with double inclined cavities, the numerical simulation of uniaxial compression was performed by discrete element software PFC2D on rock specimens with double circular cavities filled with different strength fillers at different inclinations. The results indicated that the strength and inclination of fillers had different effects on the strength and deformation characteristics of rock. With the increase of the strength of fillers, the influence of inclinations was gradually weakened. When the filling coefficient λ was 0.6, the reinforcement effect for specimens with inclined cavities was best. When the filling coefficient was greater than 0.6, the strengths of all specimens with indined cavities were almost constant, and all the specimens did not present crack aggregation phenomena between cavities. The failure process of spcimens could be characterized by acoustic emission counting, cumulative acoustic emission counting and location maps. The final failure modes of specimens with different filler strengths could be divided into tensile-shear mixed failure and shear failure. The crack aggregation modes between defects could be divided into non-aggregation, shear aggregation and tensile-shear mixed aggregation.
2023, 53(8): 184-190,153.
doi: 10.13204/j.gyjzG22070204
Abstract:
In view of a new type of anti-slide retaining structure-three rows of stepped anti-sliding piles,based on a certain actual filling slope,the mechanical characteristics, supporting effects, and influence of geotechnical parameters on mechanical characteristics of three rows of stepped anti-slide piles were discussed by the finite difference software FLAC3D. The analysis results indicated that the members of stepped anti-slide piles were of the collaborative work, coordinated deformation, large lateral stiffness,strong resistance to lateral deformation and convenient construction during filling of slopes, which could better constrain the deformation of slopes. the tensile stress concentration was easy to occur at connections between piles and beams; the tension in the back of rear piles was largest and took the second place in intermediate piles, the tension in the front pile was smallest. The lower beam was prone to shear stress concentration, and the lower beam was sheared stronger than the upper beam; as the internal friction angle of the backfill decreased, the internal forces in each member of the anti-slide piles increased,and the growth rates were increasing. With the increase of the internal friction angle of fillers, the deformation of anti-slide piles gradually decreased, and the growth rates were decreasing.
In view of a new type of anti-slide retaining structure-three rows of stepped anti-sliding piles,based on a certain actual filling slope,the mechanical characteristics, supporting effects, and influence of geotechnical parameters on mechanical characteristics of three rows of stepped anti-slide piles were discussed by the finite difference software FLAC3D. The analysis results indicated that the members of stepped anti-slide piles were of the collaborative work, coordinated deformation, large lateral stiffness,strong resistance to lateral deformation and convenient construction during filling of slopes, which could better constrain the deformation of slopes. the tensile stress concentration was easy to occur at connections between piles and beams; the tension in the back of rear piles was largest and took the second place in intermediate piles, the tension in the front pile was smallest. The lower beam was prone to shear stress concentration, and the lower beam was sheared stronger than the upper beam; as the internal friction angle of the backfill decreased, the internal forces in each member of the anti-slide piles increased,and the growth rates were increasing. With the increase of the internal friction angle of fillers, the deformation of anti-slide piles gradually decreased, and the growth rates were decreasing.
2023, 53(8): 191-198.
doi: 10.13204/j.gyjzG22060608
Abstract:
To study the uplift bearing mechanisms and failure modes of anchor bolt foundations in rock, considering the influence of buried depths and diameters of anchor bolts, and concrete curing ages, 24 anchor bolt loading tests in the field were conducted on hard granite sites. By distributed optical fiber sensing technology, strain tests were performed on 7 anchor bolts of those specimens, the load transfer mechanisms, load-bearing performance influencing factors, and failure modes and characteristics of the anchor bolts were analyzed. To anchor bolts with large diameters and deep embedded depths in rock foundation, the curves between uplift forces and displacements appeared a hardening trend, the failure mode was mainly the yielding of anchor bars. To anchor bolts with small diameters and shallow embedded depths in rock foundation, the curves between uplift forces and displacements of anchor bolts were a softening type, and the failure mainly occurred in interfaces between anchor bars and concrete, between anchor bolts and the rock masses and in shallow bedrock, they were mainly shear composite failure. To anchor bolts in rock, whose the effective anchor depth was less than 1.6 m, the mean bond strength between anchor bars and fine aggregate concrete was 2.82 MPa, and the shear strength of the interface between concrete and hard granite was not less than 1.89 MPa, the ultimate uplift bearing capacity was significantly influenced by the critical depth-to-diameter ratio, however the concrete cured more than 5 days had a little influence on the ultimate uplift bearing capacity.
To study the uplift bearing mechanisms and failure modes of anchor bolt foundations in rock, considering the influence of buried depths and diameters of anchor bolts, and concrete curing ages, 24 anchor bolt loading tests in the field were conducted on hard granite sites. By distributed optical fiber sensing technology, strain tests were performed on 7 anchor bolts of those specimens, the load transfer mechanisms, load-bearing performance influencing factors, and failure modes and characteristics of the anchor bolts were analyzed. To anchor bolts with large diameters and deep embedded depths in rock foundation, the curves between uplift forces and displacements appeared a hardening trend, the failure mode was mainly the yielding of anchor bars. To anchor bolts with small diameters and shallow embedded depths in rock foundation, the curves between uplift forces and displacements of anchor bolts were a softening type, and the failure mainly occurred in interfaces between anchor bars and concrete, between anchor bolts and the rock masses and in shallow bedrock, they were mainly shear composite failure. To anchor bolts in rock, whose the effective anchor depth was less than 1.6 m, the mean bond strength between anchor bars and fine aggregate concrete was 2.82 MPa, and the shear strength of the interface between concrete and hard granite was not less than 1.89 MPa, the ultimate uplift bearing capacity was significantly influenced by the critical depth-to-diameter ratio, however the concrete cured more than 5 days had a little influence on the ultimate uplift bearing capacity.
2023, 53(8): 199-205.
doi: 10.13204/j.gyjzG23031306
Abstract:
Based on the connection design of the prestressed system for the prefabricated piers of Xiangan Bridge in Xiamen City, the mechanical properties of cold-rolled threaded prestressed rebars in the prestressed connection system were studied. The cross-sectional organization analysis, uniaxial tensile test, and fatigue performance test of 75 mm diameter cold-rolled threaded prestressed rebars were carried out. The results showed that there was some inhomogeneity in the cross-sectional organization of 75 mm diameter cold-rolled threaded prestressed rebars, and the heat treatment process still could be improved; the uniaxial stress-strain curve of cold-rolled threaded prestressed rebars had no yield platform; considering the efficiency and accuracy of calculation, it was suggested that the multi-fold model should be adopted to calculate the cold-rolled threaded prestressed rebars in the structural calculation model at the design stage. Under normal use conditions or frequently encountered loads, the design requirements for the upper limit of rebars should be lower than the yield point σ0.2; improving the heat treatment parameters could effectively improve the fatigue performance of cold-rolled threaded prestressed rebars.
Based on the connection design of the prestressed system for the prefabricated piers of Xiangan Bridge in Xiamen City, the mechanical properties of cold-rolled threaded prestressed rebars in the prestressed connection system were studied. The cross-sectional organization analysis, uniaxial tensile test, and fatigue performance test of 75 mm diameter cold-rolled threaded prestressed rebars were carried out. The results showed that there was some inhomogeneity in the cross-sectional organization of 75 mm diameter cold-rolled threaded prestressed rebars, and the heat treatment process still could be improved; the uniaxial stress-strain curve of cold-rolled threaded prestressed rebars had no yield platform; considering the efficiency and accuracy of calculation, it was suggested that the multi-fold model should be adopted to calculate the cold-rolled threaded prestressed rebars in the structural calculation model at the design stage. Under normal use conditions or frequently encountered loads, the design requirements for the upper limit of rebars should be lower than the yield point σ0.2; improving the heat treatment parameters could effectively improve the fatigue performance of cold-rolled threaded prestressed rebars.
2023, 53(8): 206-211.
doi: 10.13204/j.gyjzG22112414
Abstract:
Recycled concrete powder, as a kind of silicoaluminate waste, has certain cementitious activity under alkali excitation. Therefore, slag and recycled concrete powder were used as precursors of alkali activated cementitious materials, and sodium hydroxide and sodium silicate were used as alkaline composite activators to prepare alkali activated geopolymer. The effects of content and fineness of recycled concrete powder on the fluidity, setting time, compressive strength and flexural strength of alkali activated slag geopolymer were studied. The test results showed that recycled concrete powder was beneficial to improving the fluidity of alkali activated slag geopolymer and prolonging the setting time, of which the particle size was less than 75 μm recycled concrete powder had a slight reduction in the fluidity of alkali activated geopolymer paste, but a significant reduction in the extension of setting time. Recycled concrete powder was conducive to improving the compressive strength and flexural strength of alkali activated slag geopolymer. The increase of mixed recycled concrete powder was conducive to the improvement of early compressive strength and flexural strength of alkali activated slag geopolymer, but not conducive to the development of late strength. In addition, when the content of recycled concrete fine powder with particle size is less than 75 μm was 50%, the compressive strengths of alkali-activated slag geopolymer at 3 d, 14 d, and 28 d increased of by 45.3%, 28.3%, and 29.4%, respectively, and its flexural strengths at 3 d, 14 d, and 28 d increased by 28.5%, 50.9%, and 39.7%, respectively, and its fluidity was 210 mm, and the initial setting time was 80 min.
Recycled concrete powder, as a kind of silicoaluminate waste, has certain cementitious activity under alkali excitation. Therefore, slag and recycled concrete powder were used as precursors of alkali activated cementitious materials, and sodium hydroxide and sodium silicate were used as alkaline composite activators to prepare alkali activated geopolymer. The effects of content and fineness of recycled concrete powder on the fluidity, setting time, compressive strength and flexural strength of alkali activated slag geopolymer were studied. The test results showed that recycled concrete powder was beneficial to improving the fluidity of alkali activated slag geopolymer and prolonging the setting time, of which the particle size was less than 75 μm recycled concrete powder had a slight reduction in the fluidity of alkali activated geopolymer paste, but a significant reduction in the extension of setting time. Recycled concrete powder was conducive to improving the compressive strength and flexural strength of alkali activated slag geopolymer. The increase of mixed recycled concrete powder was conducive to the improvement of early compressive strength and flexural strength of alkali activated slag geopolymer, but not conducive to the development of late strength. In addition, when the content of recycled concrete fine powder with particle size is less than 75 μm was 50%, the compressive strengths of alkali-activated slag geopolymer at 3 d, 14 d, and 28 d increased of by 45.3%, 28.3%, and 29.4%, respectively, and its flexural strengths at 3 d, 14 d, and 28 d increased by 28.5%, 50.9%, and 39.7%, respectively, and its fluidity was 210 mm, and the initial setting time was 80 min.
Review, Thinking and Enlightenment of “Big Dig” in the Context of Urban Renewal in the United States
2023, 53(8): 212-216,183.
doi: 10.13204/j.gyjzG21062516
Abstract:
The renewal and construction of major transportation facilities can reshape the new development pattern of the city and have a multi-dimensional impact on the city. In the era of comprehensive quality improvement, the renewal and construction of large-scale city area should be people-oriented, accurately positioned, and based on the long-term plan. The typical case of "Big Dig" in Boston was selected to systematically analyze its macro research background, and analyze the renewal process of the project during the period of "fragmentation, stitching and rebirth" and its impact on the urban development of Boston in detail, so as to construct the connection between its urban renewal value orientation, design strategy, renewal mechanism and the context of urban renewal in the United States, and bring certain enlightenment.
The renewal and construction of major transportation facilities can reshape the new development pattern of the city and have a multi-dimensional impact on the city. In the era of comprehensive quality improvement, the renewal and construction of large-scale city area should be people-oriented, accurately positioned, and based on the long-term plan. The typical case of "Big Dig" in Boston was selected to systematically analyze its macro research background, and analyze the renewal process of the project during the period of "fragmentation, stitching and rebirth" and its impact on the urban development of Boston in detail, so as to construct the connection between its urban renewal value orientation, design strategy, renewal mechanism and the context of urban renewal in the United States, and bring certain enlightenment.
2023, 53(8): 217-221,167.
doi: 10.13204/j.gyjzG22082914
Abstract:
To master stress variations in the prestressed tendons of retard-bonded prestressed concrete beams in the Desheng Sports Center of Foshan, Guangdong, retard-bonded prestressed intelligent tendons made of intelligent steel strands with Fiber Bragg Gratings wrapped with steel strands were applied into the engineering monitoring. The results indicated the retard-bonded prestressed intelligent tendons could ensure convenience of construction and measure stress of tendons at any time, accurately grasp actual prestress loss degrees in prestress tensioning construction. It was of high monitoring accuracy and could accurately reflect the changes in stress of the tendons in the structure with the construction processes, the external environment, and the solidification of adhesives. It provided reliable data support for the design and construction quality of retard-bonded prestressed concrete projects.
To master stress variations in the prestressed tendons of retard-bonded prestressed concrete beams in the Desheng Sports Center of Foshan, Guangdong, retard-bonded prestressed intelligent tendons made of intelligent steel strands with Fiber Bragg Gratings wrapped with steel strands were applied into the engineering monitoring. The results indicated the retard-bonded prestressed intelligent tendons could ensure convenience of construction and measure stress of tendons at any time, accurately grasp actual prestress loss degrees in prestress tensioning construction. It was of high monitoring accuracy and could accurately reflect the changes in stress of the tendons in the structure with the construction processes, the external environment, and the solidification of adhesives. It provided reliable data support for the design and construction quality of retard-bonded prestressed concrete projects.
2023, 53(8): 222-227.
doi: 10.13204/j.gyjzG23060103
Abstract:
Seismic design of bridges across active fault zones is a complex and systematic problem. Yingpan Bridge was taken as a research subject, which crossed the Longshu-Houzipo breakage of Ludian earthquake fault zone in Yunnan Province. A comprehensive study of domestic and international codes and research results was investigated based on the analysis of the seismic structural characteristics of the bridge location and bridge the requirements for seismic resistance. The seismic design of the bridge in the high seismic intensity zone was carried out with the consideration of the influence of the fracture dislocations generated by the active fault zone on the structure. According to the design concept and principle of "multiple lines of defense and graded energy consumption", design strategies and concrete anti-seismic measures of Yingpan Bridge were put forward from aspects of seismic conceptual design of bridge,seismic isolation design and anti-falling beam system, which could providea reference for the seismic design of samilar structures.
Seismic design of bridges across active fault zones is a complex and systematic problem. Yingpan Bridge was taken as a research subject, which crossed the Longshu-Houzipo breakage of Ludian earthquake fault zone in Yunnan Province. A comprehensive study of domestic and international codes and research results was investigated based on the analysis of the seismic structural characteristics of the bridge location and bridge the requirements for seismic resistance. The seismic design of the bridge in the high seismic intensity zone was carried out with the consideration of the influence of the fracture dislocations generated by the active fault zone on the structure. According to the design concept and principle of "multiple lines of defense and graded energy consumption", design strategies and concrete anti-seismic measures of Yingpan Bridge were put forward from aspects of seismic conceptual design of bridge,seismic isolation design and anti-falling beam system, which could providea reference for the seismic design of samilar structures.
