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2021 Vol. 51, No. 10
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2021, 51(10): 1-8.
doi: 10.13204/j.gyjzG21042502
Abstract:
Carbon fiber materials have the advantages of light weight, high strength, excellent corrosion resistance and good durability. The carbon fiber reinforced polymen (CFRP) cable dome structure can achieve a long span than the steel cable dome structures do. The prestress level of a cable dome has significant influences on the structural forces and stiffness, so it is necessary to ensure the effective prestress of the members after the tensioning is completed. In this paper, the tensioning influence coefficient of cable dome structures for calculating the tensioning value of active cables was proposed. Based on deformation coordination conditions and the principle of virtual work, the expression of the tensioning influence coefficient of the cable dome structures was derived, and the accuracy of the tensioning influence coefficient was verified by the model test of CFRP cable dome and finite element analysis. In addition, the development law of prestress and vertical displacement of connections under three tensioning schemes were analyzed and discussed, and the selection principle of active cables was proposed.
Carbon fiber materials have the advantages of light weight, high strength, excellent corrosion resistance and good durability. The carbon fiber reinforced polymen (CFRP) cable dome structure can achieve a long span than the steel cable dome structures do. The prestress level of a cable dome has significant influences on the structural forces and stiffness, so it is necessary to ensure the effective prestress of the members after the tensioning is completed. In this paper, the tensioning influence coefficient of cable dome structures for calculating the tensioning value of active cables was proposed. Based on deformation coordination conditions and the principle of virtual work, the expression of the tensioning influence coefficient of the cable dome structures was derived, and the accuracy of the tensioning influence coefficient was verified by the model test of CFRP cable dome and finite element analysis. In addition, the development law of prestress and vertical displacement of connections under three tensioning schemes were analyzed and discussed, and the selection principle of active cables was proposed.
2021, 51(10): 9-13.
doi: 10.13204/j.gyjzG21042510
Abstract:
Degradation of long-term bonding performance will cause uncontrollable slippage between FRP bars and concrete. The additional Al-ribs are effective ways to improve bonding performance. In order to study the effect of Al-ribs on restraining the long-term stiffness degradation of prestressed concrete beams reinforced with FRP bars, 6 specimens were designed and fabricated, and short-term and long-term loading tests were carried out in sequence. By comparing the specimens without Al-ribs at the beam ends, the influence of Al-ribs on long-term deflection, slippage of FRP bars and development of crack width was comprehensively studied. The results showed that the additional Al-ribs could significantly inhibit the development of long-term deflection of the members, so that the prestressed concrete beams reinforced with FRP bars maintained good long-term performance. The maximum slippage of the specimens with short Al-ribs(SA) and long Al-ribs(LA) was reduced by 81.3% and 86.7%, respectively, and the slippage of the ribs was significantly suppressed. The crack width near the fixed end of the specimens without Al-ribs was increased by 323.53%, which was much larger than that of the specimens with Al-ribs. The additional Al-ribs had a significant effect on restraining the development of concrete cracks in the shear span area.
Degradation of long-term bonding performance will cause uncontrollable slippage between FRP bars and concrete. The additional Al-ribs are effective ways to improve bonding performance. In order to study the effect of Al-ribs on restraining the long-term stiffness degradation of prestressed concrete beams reinforced with FRP bars, 6 specimens were designed and fabricated, and short-term and long-term loading tests were carried out in sequence. By comparing the specimens without Al-ribs at the beam ends, the influence of Al-ribs on long-term deflection, slippage of FRP bars and development of crack width was comprehensively studied. The results showed that the additional Al-ribs could significantly inhibit the development of long-term deflection of the members, so that the prestressed concrete beams reinforced with FRP bars maintained good long-term performance. The maximum slippage of the specimens with short Al-ribs(SA) and long Al-ribs(LA) was reduced by 81.3% and 86.7%, respectively, and the slippage of the ribs was significantly suppressed. The crack width near the fixed end of the specimens without Al-ribs was increased by 323.53%, which was much larger than that of the specimens with Al-ribs. The additional Al-ribs had a significant effect on restraining the development of concrete cracks in the shear span area.
2021, 51(10): 14-20.
doi: 10.13204/j.gyjzG21051308
Abstract:
In order to study the influence of prestress, shear-span ratio and vertical girder spacing on the shear properties of new type prestressed trussed steel-reinforced concrete beams, in this paper, five prestressed trussed steel reinforced concrete beams and one non-prestressed trussed steel reinforced concrete beam were designed and fabricated for the static shear test. The cracking load, ultimate load and deflection deformation of specimens were studied. The experimental results showed that the application of pre-stress and the reduction of the distance between vertical webs improved the shear capacity of members and effectively limited the generation and development of cracks, while the shear capacity of members decreased with the increase of the shear-span ratio. Based on the shear failure mechanism and experimental data, the shear bearing capacity formula of prestressed trussed steel-reinforced concrete beams was presented for engineering design reference.
In order to study the influence of prestress, shear-span ratio and vertical girder spacing on the shear properties of new type prestressed trussed steel-reinforced concrete beams, in this paper, five prestressed trussed steel reinforced concrete beams and one non-prestressed trussed steel reinforced concrete beam were designed and fabricated for the static shear test. The cracking load, ultimate load and deflection deformation of specimens were studied. The experimental results showed that the application of pre-stress and the reduction of the distance between vertical webs improved the shear capacity of members and effectively limited the generation and development of cracks, while the shear capacity of members decreased with the increase of the shear-span ratio. Based on the shear failure mechanism and experimental data, the shear bearing capacity formula of prestressed trussed steel-reinforced concrete beams was presented for engineering design reference.
2021, 51(10): 21-27,52.
doi: 10.13204/j.gyjzg21061511
Abstract:
In order to meet the application requirements of prestressed concrete double tees in long-span and heavy-load structures and make up for the lack of full-scale test and finite element simulation of this kind of specimens in China, four full-scale pretensioning specimens were subjected to bending load, with the spans of 12 m and 13.2 m. The whole process of the test was simulated by ABAQUS finite element analysis software, combined with the measured material characteristics. Based on the good simulation results, it was studied that the effects of concrete strength, the amount prestressed reinforcement, the amount of reinforcement in slabs and ribs, and effective prestress on the flexural properties. The results of test and finite element analysis showed that the double tees designed according to Code for Design of Prestressed Concrete Structures(JGJ 369-2016) had great safety, the actual bearing capacity of the specimen was 1.5 times higher than the design bearing capacity, and the calculated values using the measured material properties was 9.8% lower than the test values on average; the deviation of ultimate bearing capacity simulated by ABAQUS was less than 5%, and the change of reinforcement stress was consistent in the whole process; in the bending state, the effective prestress had the greatest impact on the cracking load, and the amount of prestressed reinforcement had the greatest impact on the flexural capacity. The double-layer reinforcement mesh would improve the flexural capacity by 11.3%.
In order to meet the application requirements of prestressed concrete double tees in long-span and heavy-load structures and make up for the lack of full-scale test and finite element simulation of this kind of specimens in China, four full-scale pretensioning specimens were subjected to bending load, with the spans of 12 m and 13.2 m. The whole process of the test was simulated by ABAQUS finite element analysis software, combined with the measured material characteristics. Based on the good simulation results, it was studied that the effects of concrete strength, the amount prestressed reinforcement, the amount of reinforcement in slabs and ribs, and effective prestress on the flexural properties. The results of test and finite element analysis showed that the double tees designed according to Code for Design of Prestressed Concrete Structures(JGJ 369-2016) had great safety, the actual bearing capacity of the specimen was 1.5 times higher than the design bearing capacity, and the calculated values using the measured material properties was 9.8% lower than the test values on average; the deviation of ultimate bearing capacity simulated by ABAQUS was less than 5%, and the change of reinforcement stress was consistent in the whole process; in the bending state, the effective prestress had the greatest impact on the cracking load, and the amount of prestressed reinforcement had the greatest impact on the flexural capacity. The double-layer reinforcement mesh would improve the flexural capacity by 11.3%.
2021, 51(10): 28-32,39.
doi: 10.13204/j.gyjzg21061507
Abstract:
From the standpoint of the structures' mechanical properties, the biggest difference between the retarded-bonded prestressed system and the bonded/unbonded prestressed system stems from the difference in the bond relationship between tendons and concrete. Limited by the observation methods, the bond-slip relationship curves are mainly used to judge the bond behavior in pull-out tests. Compared with the test method, the numerical simulation method can quantitatively observe and extract the damage and fracture of the material during the bonding process. In this paper, the modified CZM model was used to simulate the bonding process between the retard-bonded prestressed tendons and concrete at meso-scale. The macro mechanical response and failure modes of simulation results could achieve good agreements with those of experimental results. Based on the extracted damage and crack propagation data during the bonding process, the nonlinear bonding behavior caused by the damage evolution and crack propagation was discussed.
From the standpoint of the structures' mechanical properties, the biggest difference between the retarded-bonded prestressed system and the bonded/unbonded prestressed system stems from the difference in the bond relationship between tendons and concrete. Limited by the observation methods, the bond-slip relationship curves are mainly used to judge the bond behavior in pull-out tests. Compared with the test method, the numerical simulation method can quantitatively observe and extract the damage and fracture of the material during the bonding process. In this paper, the modified CZM model was used to simulate the bonding process between the retard-bonded prestressed tendons and concrete at meso-scale. The macro mechanical response and failure modes of simulation results could achieve good agreements with those of experimental results. Based on the extracted damage and crack propagation data during the bonding process, the nonlinear bonding behavior caused by the damage evolution and crack propagation was discussed.
2021, 51(10): 33-39.
doi: 10.13204/j.gyjzG21081711
Abstract:
Under the condition of large-tonnage prestressing, the large-diameter prestressed steel strands has obvious advantages compared with the ordinary diameter prestressed steel strands (1×7 structure, nominal diameter 15.2 mm). At present, many types of large-diameter prestressed steel strands have been used in engineering in China, but its bond performance in concrete (pretensioning method) or in cement paste (post tensioning method) is not very clear. The bond performance is very important to the crack and stiffness control of prestressed members. To this end, the large-diameter prestressed steel strands with a 1×19 structure and a nominal diameter of 21.8 mm was taken as the object, and a static pull-out test was conducted on 30 specimens. Through the analysis of the test results, the bond failure modes were obtained,and the influence of the diameter, bonding length and bonding method of the steel strands on the bonding performance of the steel strands was investigated, and the bonding stress-slip curve and the relative bonding characteristic coefficient of the steel strands were obtained. Combined with the experimental results of the flexural crack of the relevant concrete members, it was believed that the post-tensioned large-diameter prestressed steel strands had a lower bonding performance than the that of ordinary prestressed steel strands, but it had little effect on the normal performance of the members.
Under the condition of large-tonnage prestressing, the large-diameter prestressed steel strands has obvious advantages compared with the ordinary diameter prestressed steel strands (1×7 structure, nominal diameter 15.2 mm). At present, many types of large-diameter prestressed steel strands have been used in engineering in China, but its bond performance in concrete (pretensioning method) or in cement paste (post tensioning method) is not very clear. The bond performance is very important to the crack and stiffness control of prestressed members. To this end, the large-diameter prestressed steel strands with a 1×19 structure and a nominal diameter of 21.8 mm was taken as the object, and a static pull-out test was conducted on 30 specimens. Through the analysis of the test results, the bond failure modes were obtained,and the influence of the diameter, bonding length and bonding method of the steel strands on the bonding performance of the steel strands was investigated, and the bonding stress-slip curve and the relative bonding characteristic coefficient of the steel strands were obtained. Combined with the experimental results of the flexural crack of the relevant concrete members, it was believed that the post-tensioned large-diameter prestressed steel strands had a lower bonding performance than the that of ordinary prestressed steel strands, but it had little effect on the normal performance of the members.
2021, 51(10): 40-46,61.
doi: 10.13204/j.gyjzG21042509
Abstract:
Low-cycle repeated loading tests were carried out on the single-story single-span CLB rocking wall which is equipped with CFD, hysteretic curves and skeleton curves were drawn, and the problem of stiffness degradation was investigated. Based on the test results, the main body of rocking wall equipped with CFD was not damaged significantly, and the damage mode of the specimen was mainly the fracture of the bamboo material at the upper joint and the pre-stressed reinforcement anchor plate. The delayed hysteresis curve of the specimen without setting the damper was approximately bilinear, and the hysteresis curve after setting the damper was "flag shaped". Moreover, with the reduction of the moment contribution ratio, the hysteresis curve became more and more full, and the specimen still had a good strength after undergoing secondary loading. Moreover, when the specimen was subjected to secondary loading without repair, the stiffness will decreased.
Low-cycle repeated loading tests were carried out on the single-story single-span CLB rocking wall which is equipped with CFD, hysteretic curves and skeleton curves were drawn, and the problem of stiffness degradation was investigated. Based on the test results, the main body of rocking wall equipped with CFD was not damaged significantly, and the damage mode of the specimen was mainly the fracture of the bamboo material at the upper joint and the pre-stressed reinforcement anchor plate. The delayed hysteresis curve of the specimen without setting the damper was approximately bilinear, and the hysteresis curve after setting the damper was "flag shaped". Moreover, with the reduction of the moment contribution ratio, the hysteresis curve became more and more full, and the specimen still had a good strength after undergoing secondary loading. Moreover, when the specimen was subjected to secondary loading without repair, the stiffness will decreased.
2021, 51(10): 47-52.
doi: 10.13204/j.gyjzg21042504
Abstract:
The prestressed space cable-stayed suspension structure is a special structural form in the long-span space structure. It is mainly composed of diagonal load-bearing cables, central steel structure and lower stabilizer cables. The cable-stayed houseboat structure of the comprehensive building of Ocean University of China is a typical application of this structure. It mainly includes roof grid, houseboat steel members, load-bearing cables and stabilizer cables. Based on this engineering example, the paper proposed the construction method of the cable-stayed suspension structure. Firstly, the central steel structure was lifted to the height by diagonally pulling the load-bearing cable. Then the counterweight tooling cable was installed and tensioned. Then the daylighting roof and the stabilizer cable were installed in sequence and the counterweight tooling cable was removed. In the process, it was one of the keys to keep the central steel structure at the design elevation by adjusting the cable force of the counterweight tooling. According to the structural characteristics and construction methods, the force-finding analysis of the load-bearing cables and counterweight tooling cables in key construction conditions and the analysis of typical conditions in the construction process were conducted. The change laws of structural response changes were revealed and the predetermined goals of the key conditions were reached.
The prestressed space cable-stayed suspension structure is a special structural form in the long-span space structure. It is mainly composed of diagonal load-bearing cables, central steel structure and lower stabilizer cables. The cable-stayed houseboat structure of the comprehensive building of Ocean University of China is a typical application of this structure. It mainly includes roof grid, houseboat steel members, load-bearing cables and stabilizer cables. Based on this engineering example, the paper proposed the construction method of the cable-stayed suspension structure. Firstly, the central steel structure was lifted to the height by diagonally pulling the load-bearing cable. Then the counterweight tooling cable was installed and tensioned. Then the daylighting roof and the stabilizer cable were installed in sequence and the counterweight tooling cable was removed. In the process, it was one of the keys to keep the central steel structure at the design elevation by adjusting the cable force of the counterweight tooling. According to the structural characteristics and construction methods, the force-finding analysis of the load-bearing cables and counterweight tooling cables in key construction conditions and the analysis of typical conditions in the construction process were conducted. The change laws of structural response changes were revealed and the predetermined goals of the key conditions were reached.
2021, 51(10): 53-61.
doi: 10.13204/j.gyjzG20082401
Abstract:
Spatial vitality is an important factor influencing urban development. Based on POI data, relying on the ArcGIS platform, the distribution of urban vitality spaces in the main urban areas of Chengdu was studied from the perspectives of mathematical spaces and phenomenon data by using the analytic hierarchy process, coefficients of variation, nearest neighbor coefficients, kernel density analysis, spatial autocorrelation analysis and other methods. The distribution characteristics of urban vitality spaces were summarized, and the influencing factors on urban vitality were discussed. The conclusions were as follows:1) the spatial distribution of facilities of interest points in the main urban area of Chengdu was of obvious centripetallity; 2) there were some differences in spatial distribution patterns and agglomeration centers of various facilities; 3) the distribution of Chengdu's spatial vitality was of "three-circle mode"; 4) the vitality space had a strong spatial positive correlation with the population distribution and road-network density.
Spatial vitality is an important factor influencing urban development. Based on POI data, relying on the ArcGIS platform, the distribution of urban vitality spaces in the main urban areas of Chengdu was studied from the perspectives of mathematical spaces and phenomenon data by using the analytic hierarchy process, coefficients of variation, nearest neighbor coefficients, kernel density analysis, spatial autocorrelation analysis and other methods. The distribution characteristics of urban vitality spaces were summarized, and the influencing factors on urban vitality were discussed. The conclusions were as follows:1) the spatial distribution of facilities of interest points in the main urban area of Chengdu was of obvious centripetallity; 2) there were some differences in spatial distribution patterns and agglomeration centers of various facilities; 3) the distribution of Chengdu's spatial vitality was of "three-circle mode"; 4) the vitality space had a strong spatial positive correlation with the population distribution and road-network density.
2021, 51(10): 62-65.
doi: 10.13204/j.gyjzG21033103
Abstract:
In recent years, scenic byway has developed vigorously in China.However, there is a lack of rational analysis and cognition for the use of landscape resources along the scenic byway.Taking Chongli Winter Olympic scenic bayway as an example, the paper analyzed the landscape resources around the byway based on GIS, evaluated and classified the landscape resources elements by using the analytic hierarchy process, and obtained the weight factors.The planning zoning of scenic road was scientifically obtained based on the result of weight overlapping, the route selection of bicycle lane was determined, and the best locations of wetland post stations and forest post stations were selected.
In recent years, scenic byway has developed vigorously in China.However, there is a lack of rational analysis and cognition for the use of landscape resources along the scenic byway.Taking Chongli Winter Olympic scenic bayway as an example, the paper analyzed the landscape resources around the byway based on GIS, evaluated and classified the landscape resources elements by using the analytic hierarchy process, and obtained the weight factors.The planning zoning of scenic road was scientifically obtained based on the result of weight overlapping, the route selection of bicycle lane was determined, and the best locations of wetland post stations and forest post stations were selected.
2021, 51(10): 74-80.
doi: 10.13204/j.gyjzg21022003
Abstract:
Chinese village museums originated from the ecological museums that were born at the end of the 20th century, and gradually developed in the direction of small-scale, service-oriented functions, and modern facilities. At present, the village museum has shifted from focusing on the overall protection of the regional ecological environment and cultural heritage to playing an active role for the locals in strengthening cultural self-identity, enriching spiritual life, and displaying regional culture. With the popularity of the rural tourism industry, village museums have developed rapidly but are also facing some difficulties. Taking Hunan Tianhan Cultural Park as a research case, the paper attempted to analyze the setting-style space experience from the perspective of the dramatic situational space,so as to provide new explorations and attempts in addition to the prevailing design phenomena such as symbolization, imagery, and collage.
Chinese village museums originated from the ecological museums that were born at the end of the 20th century, and gradually developed in the direction of small-scale, service-oriented functions, and modern facilities. At present, the village museum has shifted from focusing on the overall protection of the regional ecological environment and cultural heritage to playing an active role for the locals in strengthening cultural self-identity, enriching spiritual life, and displaying regional culture. With the popularity of the rural tourism industry, village museums have developed rapidly but are also facing some difficulties. Taking Hunan Tianhan Cultural Park as a research case, the paper attempted to analyze the setting-style space experience from the perspective of the dramatic situational space,so as to provide new explorations and attempts in addition to the prevailing design phenomena such as symbolization, imagery, and collage.
2021, 51(10): 81-86.
doi: 10.13204/j.gyjzG21060909
Abstract:
At present, the passive ultra-low energy consumption building standard is suitable for post-design evaluation, and it lacks the energy consumption target value for the form generation stage in the early stage of design. Taking typical residential buildings in cold zone as the research object, the passive ultra-low building energy consumption target in the form generation stage was studied. Through on-the-spot investigation and data analysis, the typical model of passive ultra-low energy consumption residential buildings in cold zone was established, and the value range of influencing energy consumption variables was determined. The heating demand target value of residential buildings in the shape generation stage was deduced by combining orthogonal design and energy consumption simulation. The proposed calculation method of energy consumption target value could effectively control passive building energy consumption, assist ultra-low energy consumption building design, and provide theoretical support and design reference for ultra-low energy consumption building design concepts in other regions and other building types.
At present, the passive ultra-low energy consumption building standard is suitable for post-design evaluation, and it lacks the energy consumption target value for the form generation stage in the early stage of design. Taking typical residential buildings in cold zone as the research object, the passive ultra-low building energy consumption target in the form generation stage was studied. Through on-the-spot investigation and data analysis, the typical model of passive ultra-low energy consumption residential buildings in cold zone was established, and the value range of influencing energy consumption variables was determined. The heating demand target value of residential buildings in the shape generation stage was deduced by combining orthogonal design and energy consumption simulation. The proposed calculation method of energy consumption target value could effectively control passive building energy consumption, assist ultra-low energy consumption building design, and provide theoretical support and design reference for ultra-low energy consumption building design concepts in other regions and other building types.
2021, 51(10): 87-93,65.
doi: 10.13204/j.gyjzG20092309
Abstract:
In order to study the seismic performance of joints and integral components of T-shaped prefabricated shear walls with enengy-dissipating vertical joints, quasi-static tests were carried out on two T-shaped shear wall specimens with enengy-dissipating vertical joints until the specimens were damaged. The damaged specimens were reinforced with carbon fiber sheets and subjected to secondary loading. The main change parameter of the shear wall was the axial compression ratio (0.1, 0.3). The bearing capacity, hysteretic performance, energy dissipation performance and stiffness degradation of the shear walls before and after reinforcement were compared and analyzed. The research results showed that:T-shaped shear wall with enengy-dissipating vertical joint showed good working performance, and the CFRP reinforced structure could quickly restore the building's function. The displacement ductility coefficients before and after reinforcement were close to or higher than 3, which reflected the good deformability of the specimen. The damper had good connection and working performance, and the specimen as a whole showed good enengy-dissipating capacity.
In order to study the seismic performance of joints and integral components of T-shaped prefabricated shear walls with enengy-dissipating vertical joints, quasi-static tests were carried out on two T-shaped shear wall specimens with enengy-dissipating vertical joints until the specimens were damaged. The damaged specimens were reinforced with carbon fiber sheets and subjected to secondary loading. The main change parameter of the shear wall was the axial compression ratio (0.1, 0.3). The bearing capacity, hysteretic performance, energy dissipation performance and stiffness degradation of the shear walls before and after reinforcement were compared and analyzed. The research results showed that:T-shaped shear wall with enengy-dissipating vertical joint showed good working performance, and the CFRP reinforced structure could quickly restore the building's function. The displacement ductility coefficients before and after reinforcement were close to or higher than 3, which reflected the good deformability of the specimen. The damper had good connection and working performance, and the specimen as a whole showed good enengy-dissipating capacity.
2021, 51(10): 94-100.
doi: 10.13204/j.gyjzG21060604
Abstract:
In order to meet the requirements of high stiffness and high bearing capacity of special low-rise light-weight building structure,a kind of cold-formed thin-walled steel double-limb battened-plate lattice column was proposed to study the axial bearing capacity.The influence mechanism of the edge stiffener length,web thickness and the number of batten plates on the bearing capacity of thin-walled steel lattice columns under axial compression was analyzed by using ABAQUS finite element software.The load-displacement curve,stress development trend and failure mode of the grid columns under various working conditions were obtained.The results showed that the bearing capacity of cold-formed thin-walled steel lattice columns with the same section decreased with the increase of the length of the columns,and the failure mode of the members changed from strength failure to overall instability failure,and the local buckling and distortion buckling were accompanied.The increase of plate thickness had a great influence on the axial compression capacity of cold-formed thin-walled steel lattice columns,while the influence of the edge stiffener length and the number of batten plates on the bearing capacity of the thin-steel lattice column under axial compression was not positive.Through comparative analysis,the thin-walled steel double-limb battened-plate lattice columns had high bearing capacity and good lateral stiffness under axial compression. Within the range of section size parameters of lattice columns,it was suggested that the thickness of thin-walled steel of lattice columns should be 1.0-1.5 mm,the spacing of batten plates should be 300 mm,and the length of edge stiffeners should be 1/3 of the section height,so as to provide a reference for the design of members.
In order to meet the requirements of high stiffness and high bearing capacity of special low-rise light-weight building structure,a kind of cold-formed thin-walled steel double-limb battened-plate lattice column was proposed to study the axial bearing capacity.The influence mechanism of the edge stiffener length,web thickness and the number of batten plates on the bearing capacity of thin-walled steel lattice columns under axial compression was analyzed by using ABAQUS finite element software.The load-displacement curve,stress development trend and failure mode of the grid columns under various working conditions were obtained.The results showed that the bearing capacity of cold-formed thin-walled steel lattice columns with the same section decreased with the increase of the length of the columns,and the failure mode of the members changed from strength failure to overall instability failure,and the local buckling and distortion buckling were accompanied.The increase of plate thickness had a great influence on the axial compression capacity of cold-formed thin-walled steel lattice columns,while the influence of the edge stiffener length and the number of batten plates on the bearing capacity of the thin-steel lattice column under axial compression was not positive.Through comparative analysis,the thin-walled steel double-limb battened-plate lattice columns had high bearing capacity and good lateral stiffness under axial compression. Within the range of section size parameters of lattice columns,it was suggested that the thickness of thin-walled steel of lattice columns should be 1.0-1.5 mm,the spacing of batten plates should be 300 mm,and the length of edge stiffeners should be 1/3 of the section height,so as to provide a reference for the design of members.
ANALYSIS ON OVERALL BUCKLING OF COLD-FORMED THIN-WALLED STEEL LIPPED CHANNEL BEAMS WITH WEB OPENINGS
2021, 51(10): 101-108,100.
doi: 10.13204/j.gyjzg21081302
Abstract:
The finite element software ABAQUS was used to analyze the influence of web openings on the overall buckling coefficient cold-formed thin-walled steel lipped channel beams with web openings considering the type, size and position of openings. The analysis results showed that the size of the opening had a greater influence on the overall buckling coefficient for bending members. The overall buckling coefficients φb of bending members decreased with the increase of diameter of the circular opening or length and width of rectangular opening. The opening spacing had a slight effect on the overall buckling coefficient when it met a limit value. Then the calculation method of overall buckling coefficient of cold-formed thin-walled lipped channel steel bending members with circle or rectangular openings in the web was presented based on the finite element parameters analysis. Finally, the comparison on the overall buckling coefficient between predictions with proposed method and finite element results and results by using AISI showed a great accuracy and feasibility. The proposed method could be used to predict the overall buckling coefficient of cold-formed thin-walled lipped channel steel members with circle or rectangular openings in the web.
The finite element software ABAQUS was used to analyze the influence of web openings on the overall buckling coefficient cold-formed thin-walled steel lipped channel beams with web openings considering the type, size and position of openings. The analysis results showed that the size of the opening had a greater influence on the overall buckling coefficient for bending members. The overall buckling coefficients φb of bending members decreased with the increase of diameter of the circular opening or length and width of rectangular opening. The opening spacing had a slight effect on the overall buckling coefficient when it met a limit value. Then the calculation method of overall buckling coefficient of cold-formed thin-walled lipped channel steel bending members with circle or rectangular openings in the web was presented based on the finite element parameters analysis. Finally, the comparison on the overall buckling coefficient between predictions with proposed method and finite element results and results by using AISI showed a great accuracy and feasibility. The proposed method could be used to predict the overall buckling coefficient of cold-formed thin-walled lipped channel steel members with circle or rectangular openings in the web.
2021, 51(10): 109-115,121.
doi: 10.13204/j.gyjzG21053120
Abstract:
For the failure of lightning rod in transmission tower, an innovation connection between the lighting rod and the transmission tower was proposed based on the concept of reducing the stress amplitude of high-strength bolts and realizing double protection, namely steel strand reinforced flange joint. The finite element model was established by using the finite element software WORKBENCH. The stress and displacement were studied on two kinds of joints for lightning rods at different wind speeds and steel strand pretensions of 20 kN. The stress nephogram, streamline vector diagram,stress and displacement response of the lightning rod structure caused by fluid were expressed under the wind velocity of 5 m/s,15 m/s,30 m/s, and 50 m/s. The contrastive analysis was carried on the stress and displacement response of the lightning rod with the measured values under different loading conditions. The analysis results showed that the lightning rod was subjected to the same fluid pressure under the same load. The stress was the largest at the connection between the lightning rod and the herringbone column. The research results showed that the new lightning rod could significantly reduce the peak values compared with the conventional lightning rod. It was more effectively in reducing the stress peak values on the connecting bolts so as to ensure the safe use of the lightning rod. The higher the wind speed, the more obvious the effect.
For the failure of lightning rod in transmission tower, an innovation connection between the lighting rod and the transmission tower was proposed based on the concept of reducing the stress amplitude of high-strength bolts and realizing double protection, namely steel strand reinforced flange joint. The finite element model was established by using the finite element software WORKBENCH. The stress and displacement were studied on two kinds of joints for lightning rods at different wind speeds and steel strand pretensions of 20 kN. The stress nephogram, streamline vector diagram,stress and displacement response of the lightning rod structure caused by fluid were expressed under the wind velocity of 5 m/s,15 m/s,30 m/s, and 50 m/s. The contrastive analysis was carried on the stress and displacement response of the lightning rod with the measured values under different loading conditions. The analysis results showed that the lightning rod was subjected to the same fluid pressure under the same load. The stress was the largest at the connection between the lightning rod and the herringbone column. The research results showed that the new lightning rod could significantly reduce the peak values compared with the conventional lightning rod. It was more effectively in reducing the stress peak values on the connecting bolts so as to ensure the safe use of the lightning rod. The higher the wind speed, the more obvious the effect.
2021, 51(10): 116-121.
doi: 10.13204/j.gyjzG20111805
Abstract:
Aiming at the difficulty in weighing and counterweighting of super-tonnage asymmetric bridges with horizontal rotation construction, a new system for horizontal rotation of bridges has been developed. The system adopts load-bearing supports to bear the unbalanced moment of the upper part, which can save construction procedures and costs such as the weighing and counterweight. A finite element model of the new system was established by using the software ABAQUS, and it was used to analyze the spherical hinge and the concrete-filled steel tubular footing under the action of vertical load and unbalanced moment. The load distribution between the support footing and the spherical hinge was basically consistent with the theoretical results. The friction moment of the spherical hinge could counterbalance part of the unbalanced moment. When the friction coefficient increased from 0.03 to 0.1, the friction moment increased, and the vertical force of the spherical hinge and support footing increased by 2.4% and -19.1%, respectively. Thus the friction coefficient had slight effect on the vertical force of the load-bearing support footing. The friction coefficient of the spherical hinge should be minimized in order to minimize the traction force. The proposed formula could be used to calculate the vertical load borne by the concrete-filled steel tube support footing.
Aiming at the difficulty in weighing and counterweighting of super-tonnage asymmetric bridges with horizontal rotation construction, a new system for horizontal rotation of bridges has been developed. The system adopts load-bearing supports to bear the unbalanced moment of the upper part, which can save construction procedures and costs such as the weighing and counterweight. A finite element model of the new system was established by using the software ABAQUS, and it was used to analyze the spherical hinge and the concrete-filled steel tubular footing under the action of vertical load and unbalanced moment. The load distribution between the support footing and the spherical hinge was basically consistent with the theoretical results. The friction moment of the spherical hinge could counterbalance part of the unbalanced moment. When the friction coefficient increased from 0.03 to 0.1, the friction moment increased, and the vertical force of the spherical hinge and support footing increased by 2.4% and -19.1%, respectively. Thus the friction coefficient had slight effect on the vertical force of the load-bearing support footing. The friction coefficient of the spherical hinge should be minimized in order to minimize the traction force. The proposed formula could be used to calculate the vertical load borne by the concrete-filled steel tube support footing.
2021, 51(10): 122-126.
doi: 10.13204/j.gyjzG20051211
Abstract:
By using the theory of element-free Galerkin method based on orthogonal basis function, a program for solving the coupled thermo-elastic-plastic discrete equation of transient temperature field and elastic-plastic stress field was compiled by MATLAB, and it was applied to the nonlinear analysis of fire test of columns in steel frame.The temperature change process at the temperature measurement points and the changing trend of rotation angle with temperature were analyzed. By comparing the analytical results with the numerical analysis results and the field measured data, the applicability and superiority of this method were verified, which could provide a new reference for the research of steel frames at high temperatures.
By using the theory of element-free Galerkin method based on orthogonal basis function, a program for solving the coupled thermo-elastic-plastic discrete equation of transient temperature field and elastic-plastic stress field was compiled by MATLAB, and it was applied to the nonlinear analysis of fire test of columns in steel frame.The temperature change process at the temperature measurement points and the changing trend of rotation angle with temperature were analyzed. By comparing the analytical results with the numerical analysis results and the field measured data, the applicability and superiority of this method were verified, which could provide a new reference for the research of steel frames at high temperatures.
2021, 51(10): 127-133.
doi: 10.13204/j.gyjzg20100907
Abstract:
In order to study the effect of the clustering degree of shear connector (defined as the ratio of the number of shear connectors in the reserved holes of a single section to the total number of shear connectors in the whole beam) on the stiffness of the prefabricated composite beam when the shear connectors are arranged in clusters, the static loading experiments of one cast-in-place composite beam and 2 pieces of assembled composite beams with different bundling degrees were carried out to test the section strain distribution, interface slippage and mid-span deflection, and the change laws of the section stiffness and deflection were also analyzed. Based on continuous gradient assumed that the stifiness of the section without shear connection and the principle of equal area of the section without shear connection before and after equivalence, the stiffness equivalent simplified method was proposed, the principle of equivalent flexural stiffness of the section without shear connection was derived. Combining with the elastic theory, the formula of elastic bending stiffness reduction factor η of prefabricated composite beams was built.By considering the effects of clustering degree, the calculation method for the η of prefabricated composite beams was obtained and applied to the mid-span deflection equation of prefabricated composite beam with different loads. The calculated values of the formula were in good agreement with the actual test values. The minimum deviation was 0.4%, and the maximum deviation was 14.8%. It showed that the calculation formula in this paper had good accuracy and it couls be used to analyze the effects of clustering degree on the stiffness of prefabricated composite beam with this type of cluster key group.
In order to study the effect of the clustering degree of shear connector (defined as the ratio of the number of shear connectors in the reserved holes of a single section to the total number of shear connectors in the whole beam) on the stiffness of the prefabricated composite beam when the shear connectors are arranged in clusters, the static loading experiments of one cast-in-place composite beam and 2 pieces of assembled composite beams with different bundling degrees were carried out to test the section strain distribution, interface slippage and mid-span deflection, and the change laws of the section stiffness and deflection were also analyzed. Based on continuous gradient assumed that the stifiness of the section without shear connection and the principle of equal area of the section without shear connection before and after equivalence, the stiffness equivalent simplified method was proposed, the principle of equivalent flexural stiffness of the section without shear connection was derived. Combining with the elastic theory, the formula of elastic bending stiffness reduction factor η of prefabricated composite beams was built.By considering the effects of clustering degree, the calculation method for the η of prefabricated composite beams was obtained and applied to the mid-span deflection equation of prefabricated composite beam with different loads. The calculated values of the formula were in good agreement with the actual test values. The minimum deviation was 0.4%, and the maximum deviation was 14.8%. It showed that the calculation formula in this paper had good accuracy and it couls be used to analyze the effects of clustering degree on the stiffness of prefabricated composite beam with this type of cluster key group.
2021, 51(10): 134-140.
doi: 10.13204/j.gyjzG21020108
Abstract:
In combination with the actual project, the design schemes of large-scale prefabricated concrete composite beams were compared and analyzed by using hollow partially precast steel reinforced concrete beams (HPSRC beams). Based on the experimental research, the method of rational selection of the cross section and calculation method for HPSRC beam was proposed. The calculation results showed that the HPSRC beam could effectively reduce the height of the prestressed reinforced concrete beam, reduce the structural weight and simplify the on-site construction process. Furthermore, the finite element analysis model was selected to simulate the two-stage construction process of HPSRC beam,and the stress and deflection of the two-stage construction can both meet the requirement of current standards.
In combination with the actual project, the design schemes of large-scale prefabricated concrete composite beams were compared and analyzed by using hollow partially precast steel reinforced concrete beams (HPSRC beams). Based on the experimental research, the method of rational selection of the cross section and calculation method for HPSRC beam was proposed. The calculation results showed that the HPSRC beam could effectively reduce the height of the prestressed reinforced concrete beam, reduce the structural weight and simplify the on-site construction process. Furthermore, the finite element analysis model was selected to simulate the two-stage construction process of HPSRC beam,and the stress and deflection of the two-stage construction can both meet the requirement of current standards.
2021, 51(10): 141-146.
doi: 10.13204/j.gyjzg21041903
Abstract:
The mechanical operation of industrial steel-making plant has the characteristics of high strength, obvious vibration and high risk, which has a certain influence on the structural safety of the plant and the working comfort of the staff in the park. If the vibration of the plant does not meet the requirements, it is necessary to carry out modification or take vibration isolation measures to improve the safety and comfort of the plant. Taking the slag treatment workshop of Zhanjiang Baogang plant in Guangdong as the research object, field vibration test was carried out, the impact of the drop hammer treatment process on the vibration of the structure and the surrounding environment was analyzed, the vibration reduction measures were put forward, and the finite element model was established to analyze the vibration reduction effect. The results showed that the ground vibration response caused by falling hammers was large. In some areas, the ground vibration acceleration and the weight acceleration level of the vibration meter exceed the allowable limit value of the specification, which had a significant impact on comfort; the isolation effect of the building structure on vibration was not obvious, and the surrounding environment vibration was large; the vibration reduction effect was obvious by adding soft soil layer; when the thickness of soft soil was 0.3 m, the vibration amplitude decreased to 10% of the original value.
The mechanical operation of industrial steel-making plant has the characteristics of high strength, obvious vibration and high risk, which has a certain influence on the structural safety of the plant and the working comfort of the staff in the park. If the vibration of the plant does not meet the requirements, it is necessary to carry out modification or take vibration isolation measures to improve the safety and comfort of the plant. Taking the slag treatment workshop of Zhanjiang Baogang plant in Guangdong as the research object, field vibration test was carried out, the impact of the drop hammer treatment process on the vibration of the structure and the surrounding environment was analyzed, the vibration reduction measures were put forward, and the finite element model was established to analyze the vibration reduction effect. The results showed that the ground vibration response caused by falling hammers was large. In some areas, the ground vibration acceleration and the weight acceleration level of the vibration meter exceed the allowable limit value of the specification, which had a significant impact on comfort; the isolation effect of the building structure on vibration was not obvious, and the surrounding environment vibration was large; the vibration reduction effect was obvious by adding soft soil layer; when the thickness of soft soil was 0.3 m, the vibration amplitude decreased to 10% of the original value.
2021, 51(10): 147-156,140.
doi: 10.13204/j.gyjzg20122215
Abstract:
Fiber-reinforced sandy soil is a multi-phase and multi-scale geo-material, and its strength is determined by properties of the heterogeneous materials of soil and their coupling interaction mechanical responses. On the basis of the microscopic slip effect between sand grains and between sand grains and fibers,a soil cell-element that could describe the internal material information and fiber characteristics of fiber-reinforced sandy soil was constructed by dividing fiber-reinforced sandy soil into different phases of materials to study the influence of the geometrical and mechanical characteristics of fibers on the shear strength of fiber-reinforced sandy soil. According to the compatible geometry deformation between fibers and soil on the microscale,the notion of strain gradient that could effectively describe the interface discontinuity of mechanical response was introduced,and a theoretical model of fiber-reinforced sandy soil based on mesophysical mechanisms was proposed. Moreover,the results from consolidated-undrained triaxial tests conducted by Michalowski and Cermak were used to validate the proposed model. Meanwhile,the theoretical parameters of the model were quantitatively studied. The results showed the addition of fibers caused plastic rotation gradient and interface slip of sand particles adjacent to fibers which was the mesoscopic physical mechanism for the fiber-strengthened effect of fiber-reinforced soil.
Fiber-reinforced sandy soil is a multi-phase and multi-scale geo-material, and its strength is determined by properties of the heterogeneous materials of soil and their coupling interaction mechanical responses. On the basis of the microscopic slip effect between sand grains and between sand grains and fibers,a soil cell-element that could describe the internal material information and fiber characteristics of fiber-reinforced sandy soil was constructed by dividing fiber-reinforced sandy soil into different phases of materials to study the influence of the geometrical and mechanical characteristics of fibers on the shear strength of fiber-reinforced sandy soil. According to the compatible geometry deformation between fibers and soil on the microscale,the notion of strain gradient that could effectively describe the interface discontinuity of mechanical response was introduced,and a theoretical model of fiber-reinforced sandy soil based on mesophysical mechanisms was proposed. Moreover,the results from consolidated-undrained triaxial tests conducted by Michalowski and Cermak were used to validate the proposed model. Meanwhile,the theoretical parameters of the model were quantitatively studied. The results showed the addition of fibers caused plastic rotation gradient and interface slip of sand particles adjacent to fibers which was the mesoscopic physical mechanism for the fiber-strengthened effect of fiber-reinforced soil.
2021, 51(10): 163-169.
doi: 10.13204/j.gyjzG20092205
Abstract:
Existing bearing-capacity design methods of piles based on the cone penetration test (CPT) indices are mostly suitable for the situation of steel pipe piles in sandy soil. On the basis of existing research, a CPT-based design method for the bearing capacity of steel pipe piles in clayey soil was proposed. A index of final-plug length ratios (FLR) was introduced to consider the effect of soil plugging. Furthermore, optimization was conducted on some key issues such as stress reduction, soil-squeezed effect, deterioration of lateral resistance and influence zones at pile tips. The prediction accuracy of the recommended method was in comparison with a full-scale pile in-situ and it showed that the method was more accurate than those of existing methods. By combining the method with existing ones suitable for sandy soil, engineering calculations for the bearing capacity of steel pipe piles in natural stratified soils could be realized.
Existing bearing-capacity design methods of piles based on the cone penetration test (CPT) indices are mostly suitable for the situation of steel pipe piles in sandy soil. On the basis of existing research, a CPT-based design method for the bearing capacity of steel pipe piles in clayey soil was proposed. A index of final-plug length ratios (FLR) was introduced to consider the effect of soil plugging. Furthermore, optimization was conducted on some key issues such as stress reduction, soil-squeezed effect, deterioration of lateral resistance and influence zones at pile tips. The prediction accuracy of the recommended method was in comparison with a full-scale pile in-situ and it showed that the method was more accurate than those of existing methods. By combining the method with existing ones suitable for sandy soil, engineering calculations for the bearing capacity of steel pipe piles in natural stratified soils could be realized.
2021, 51(10): 170-176.
doi: 10.13204/j.gyjzG21021601
Abstract:
The stress-strain constitutive relation of FRP-confined concrete can be divided into two categories of constraint models under axial load:work hardening and softening. The intrinsic axial compressive stress and strain in the ultimate state constitute the parameter basis of their constitutions. Calculating these constitutive parameters accurately can provide a discrimination criteria for evaluating the performance of FRP-confined concrete structures. The performance of the existing empirical models about compressive strength and ultimate compressive strain of rectangular concrete confined with FRP was evaluated comprehensively, and the results showed that the existing empirical models generally showed poor universality, low prediction accuracy and high dispersion. Aiming at the limitation of traditional prediction models, the prediction models of compressive strength and ultimate compressive strain for both hardening and softening types of rectangular concrete confined with FRP were constructed respectively based on back-propagation artificial neural network. The research results indicated that the neural network models could not only reflect the influence of various control parameters on the axial compressive stress and strain, but also the calculated values based on the neural network models were in better agreement with the experimental values when compared with the existing empirical models; moreover, the deviation and randomness were significantly decreased,so as to ensure the accuracy and stability of prediction results.
The stress-strain constitutive relation of FRP-confined concrete can be divided into two categories of constraint models under axial load:work hardening and softening. The intrinsic axial compressive stress and strain in the ultimate state constitute the parameter basis of their constitutions. Calculating these constitutive parameters accurately can provide a discrimination criteria for evaluating the performance of FRP-confined concrete structures. The performance of the existing empirical models about compressive strength and ultimate compressive strain of rectangular concrete confined with FRP was evaluated comprehensively, and the results showed that the existing empirical models generally showed poor universality, low prediction accuracy and high dispersion. Aiming at the limitation of traditional prediction models, the prediction models of compressive strength and ultimate compressive strain for both hardening and softening types of rectangular concrete confined with FRP were constructed respectively based on back-propagation artificial neural network. The research results indicated that the neural network models could not only reflect the influence of various control parameters on the axial compressive stress and strain, but also the calculated values based on the neural network models were in better agreement with the experimental values when compared with the existing empirical models; moreover, the deviation and randomness were significantly decreased,so as to ensure the accuracy and stability of prediction results.
2021, 51(10): 177-183.
doi: 10.13204/j.gyjzg20103011
Abstract:
It is of great significance to use vibration response for intelligent detection and diagnosis of structural damage. However, the traditional deep convolution neural network model has some problems in processing structural vibration signal, such as large model parameters, loss of signal detail information and poor generalization performance. Therefore, a structural damage detection method based on one-dimensional dilated convolution neural network was proposed. The neural network model used in this method used dilated convolution to replace the traditional combination layer of convolution and pooling, and increased the receptive field while keeping the number of parameters unchanged; global pooling layer was used to replace the traditional full connection layer to reduce the model parameters and prevent the occurrence of over fitting, and then according to the phenomenon of class imbalance in the actual vibration signal data set, the cost sensitive classifier was trained by setting penalty weights for different types of signals, which could effectively improve the structural damage detection accuracy under unbalanced samples. The verification and application analysis of the damage experiment on the grandstand scale model of the University of Qatar showed that the method proposed in the paper could automatically extract the optimal features from the original acceleration signals and classify them without losing the detailed information of the signals, thus achieving high recognition accuracy and classification success ratio, which could be used for real-time damage detection.
It is of great significance to use vibration response for intelligent detection and diagnosis of structural damage. However, the traditional deep convolution neural network model has some problems in processing structural vibration signal, such as large model parameters, loss of signal detail information and poor generalization performance. Therefore, a structural damage detection method based on one-dimensional dilated convolution neural network was proposed. The neural network model used in this method used dilated convolution to replace the traditional combination layer of convolution and pooling, and increased the receptive field while keeping the number of parameters unchanged; global pooling layer was used to replace the traditional full connection layer to reduce the model parameters and prevent the occurrence of over fitting, and then according to the phenomenon of class imbalance in the actual vibration signal data set, the cost sensitive classifier was trained by setting penalty weights for different types of signals, which could effectively improve the structural damage detection accuracy under unbalanced samples. The verification and application analysis of the damage experiment on the grandstand scale model of the University of Qatar showed that the method proposed in the paper could automatically extract the optimal features from the original acceleration signals and classify them without losing the detailed information of the signals, thus achieving high recognition accuracy and classification success ratio, which could be used for real-time damage detection.
2021, 51(10): 184-188,133.
doi: 10.13204/j.gyjzG20081201
Abstract:
To solve the problems of too many parameters, difficult to obtain and longer time-consuming in numerical simulations of ultimate displacement in the process of tunnelling, the Gaussian process algorithm (GP) combined with the differential evolutionary algorithm (DE) was adopted. The selection of GP hyperparameters in the training process was realized by the DE instead of the conjugated gradient method, which solved the problem that the conjugated gradient method was too dependent on the initial values and easy to fall into local optimal, and improved generalization performances of the GP. A DE-GP method for predicting ultimate displacement during tunnelling was proposed, which simplified the calculation process of ultimate displacement. The ultimate displacement of a highway tunnel during tunnelling was predicted and analyzed. The results showed that the DE-GP coupled model had a better generalization performances than the GP and the LS-SVM algorithm; the forecasting results of ultimate displacement agreed well with the numerical calculations, and the computational efficiency had obviously improved; the method provided a new way to calculate the ultimate displacement.
To solve the problems of too many parameters, difficult to obtain and longer time-consuming in numerical simulations of ultimate displacement in the process of tunnelling, the Gaussian process algorithm (GP) combined with the differential evolutionary algorithm (DE) was adopted. The selection of GP hyperparameters in the training process was realized by the DE instead of the conjugated gradient method, which solved the problem that the conjugated gradient method was too dependent on the initial values and easy to fall into local optimal, and improved generalization performances of the GP. A DE-GP method for predicting ultimate displacement during tunnelling was proposed, which simplified the calculation process of ultimate displacement. The ultimate displacement of a highway tunnel during tunnelling was predicted and analyzed. The results showed that the DE-GP coupled model had a better generalization performances than the GP and the LS-SVM algorithm; the forecasting results of ultimate displacement agreed well with the numerical calculations, and the computational efficiency had obviously improved; the method provided a new way to calculate the ultimate displacement.
2021, 51(10): 189-200.
doi: 10.13204/j.gyjzG21020313
Abstract:
In order to study the effectiveness of ultrasonic tomography in nondestructive testing of the compactness of concrete-filled steel tubes, the location and size of concrete defects in the pipe were qualitatively analyzed and quantitatively judged from three aspects of theoretical research, finite element simulation and test. The results showed that:when the concrete in the pipe had defects, the acoustic propagation path would be changed. The quantitative calculation method was given which was lower than the percentage of the average value of the sound velocity of the section. ABAQUS could directly reflect the propagation direction of the sound waves. It was concluded that sound waves traveled along the shortest path, which was consistent with the theoretical results. In the test, the ultrasonic tomography could be used to identify the preset defects. The results of stheoretical calculation, finite element simulation and test showed that the average value of section sound velocity decreased with the increase of defect body, and the minimum value of sound velocity of the section decreased with the increase of defect body.
In order to study the effectiveness of ultrasonic tomography in nondestructive testing of the compactness of concrete-filled steel tubes, the location and size of concrete defects in the pipe were qualitatively analyzed and quantitatively judged from three aspects of theoretical research, finite element simulation and test. The results showed that:when the concrete in the pipe had defects, the acoustic propagation path would be changed. The quantitative calculation method was given which was lower than the percentage of the average value of the sound velocity of the section. ABAQUS could directly reflect the propagation direction of the sound waves. It was concluded that sound waves traveled along the shortest path, which was consistent with the theoretical results. In the test, the ultrasonic tomography could be used to identify the preset defects. The results of stheoretical calculation, finite element simulation and test showed that the average value of section sound velocity decreased with the increase of defect body, and the minimum value of sound velocity of the section decreased with the increase of defect body.
2021, 51(10): 201-210,8.
doi: 10.13204/j.gyjzg20111504
Abstract:
Different kinds of real-time monitoring and regular "physical examination" for buildings of different ages and types can help to find hidden safety hazards, avoid accidents, achieve the purpose of early warning and timely maintenance, improve the durability of buildings, facilitate green development, and protect the safety of people's lives and property. This paper put forward the whole life cycle management mode of the house, discussed the frame, operation mode and service content of the building safety operation and maintenance service system based on the Internet of Things, defined the subsystems and corresponding functions of the building safety operation and maintenance service system based on the Internet of Things, and developed the WeChat service account "Building Safety Guard", the big data acquisition and monitoring platform based on the Internet of Things, building safety assessment system/safety early warning and auxiliary decision-making system, this paper briefly introduced the application of Bayesian network, deep neural network and other advanced algorithms in building safety assessment, as well as the key techniques of automatic health monitoring platform based on Internet of Things, so that the system could provide all kinds of real-time services and professional services for all kinds of users to complete the goal of construction safety operation and maintenance services, to promote the establishment of building security management system, to help the construction of smart towns, and to form a full cycle closed loop of urban development based on effective monitoring and evaluation and safety maintenance management.
Different kinds of real-time monitoring and regular "physical examination" for buildings of different ages and types can help to find hidden safety hazards, avoid accidents, achieve the purpose of early warning and timely maintenance, improve the durability of buildings, facilitate green development, and protect the safety of people's lives and property. This paper put forward the whole life cycle management mode of the house, discussed the frame, operation mode and service content of the building safety operation and maintenance service system based on the Internet of Things, defined the subsystems and corresponding functions of the building safety operation and maintenance service system based on the Internet of Things, and developed the WeChat service account "Building Safety Guard", the big data acquisition and monitoring platform based on the Internet of Things, building safety assessment system/safety early warning and auxiliary decision-making system, this paper briefly introduced the application of Bayesian network, deep neural network and other advanced algorithms in building safety assessment, as well as the key techniques of automatic health monitoring platform based on Internet of Things, so that the system could provide all kinds of real-time services and professional services for all kinds of users to complete the goal of construction safety operation and maintenance services, to promote the establishment of building security management system, to help the construction of smart towns, and to form a full cycle closed loop of urban development based on effective monitoring and evaluation and safety maintenance management.
2021, 51(10): 211-216,162.
doi: 10.13204/j.gyjzg20111403
Abstract:
The urban underground pipe gallery often produces adverse effects on the deformation and uneven settlement of upper ground building after construction. Under the horizontal earthquake action after the construction of the underground pipe gallery, the adverse effects will be magnified, even beyond the normal use scope of the upper structure. Based on a practical project, the seismic response of the building structure before and after the construction of the underground pipe gallery was analyzed by the finite element method based on the nonlinear time history analysis proposed by Standard for Seismic Design of Underground Structures (GB/T 51336-2018). The seismic response difference of the structure before and after the construction of the pipe gallery was obtained, and the reasons for the difference were analyzed by using the calculation results. By simulating the design and construction measures of grouting reinforcement around the pipe gallery and adjusting the structural stiffness of the pipe gallery, the seismic response of the superstructure was obtained, and the effective control measures for improving the construction of the pipe gallery under the existing high-rise building were obtained. After the completion of the actual project, the soil samples before and after grouting reinforcement were extracted for indoor dynamic triaxial test. The test results could further support the improvement effect of grouting on the dynamic characteristics of foundation soil and the control effect on the seismic response of upper structure.
The urban underground pipe gallery often produces adverse effects on the deformation and uneven settlement of upper ground building after construction. Under the horizontal earthquake action after the construction of the underground pipe gallery, the adverse effects will be magnified, even beyond the normal use scope of the upper structure. Based on a practical project, the seismic response of the building structure before and after the construction of the underground pipe gallery was analyzed by the finite element method based on the nonlinear time history analysis proposed by Standard for Seismic Design of Underground Structures (GB/T 51336-2018). The seismic response difference of the structure before and after the construction of the pipe gallery was obtained, and the reasons for the difference were analyzed by using the calculation results. By simulating the design and construction measures of grouting reinforcement around the pipe gallery and adjusting the structural stiffness of the pipe gallery, the seismic response of the superstructure was obtained, and the effective control measures for improving the construction of the pipe gallery under the existing high-rise building were obtained. After the completion of the actual project, the soil samples before and after grouting reinforcement were extracted for indoor dynamic triaxial test. The test results could further support the improvement effect of grouting on the dynamic characteristics of foundation soil and the control effect on the seismic response of upper structure.
2021, 51(10): 217-224.
doi: 10.13204/j.gyjzG20083002
Abstract:
As one of the most successful regional tourism routes of industrial heritage in the world, the European Route of Industrial Heritage (ERIH) model has important reference significance for the development of industrial heritage tourism in Beijing-Tianjin-Hebei region. This paper analyzed the feasibility and significance of the model in the Beijing-Tianjin-Hebei region by sorting out the main components of the European industrial heritage road and summarizing its successful experience. Combined with the model and the specific situation of industrial heritage tourism in Beijing-Tianjin-Hebei region, the paper put forward some specific ideas and suggestions for the construction of industrial heritage road in Beijing-Tianjin-Hebei region.
As one of the most successful regional tourism routes of industrial heritage in the world, the European Route of Industrial Heritage (ERIH) model has important reference significance for the development of industrial heritage tourism in Beijing-Tianjin-Hebei region. This paper analyzed the feasibility and significance of the model in the Beijing-Tianjin-Hebei region by sorting out the main components of the European industrial heritage road and summarizing its successful experience. Combined with the model and the specific situation of industrial heritage tourism in Beijing-Tianjin-Hebei region, the paper put forward some specific ideas and suggestions for the construction of industrial heritage road in Beijing-Tianjin-Hebei region.
2021, 51(10): 225-227.
Abstract:
