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2020 Vol. 50, No. 4
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2020, 50(4): 10-18.
doi: 10.13204/j.gyjz202004003
Abstract:
Rebar truss composite floor has good mechanical properties, less formwork, and good overall performance and seismic performance, and was widely used in prefabricated steel structures. However, the beams, walls and floors were separately poured into concrete in concrete structure, and the top surface of beams or walls was not flat. The height and position of traditional composite floor were difficult to be adjusted to and reach the predetermined elevation, which affected the assembly effect and construction quality. Therefore, the height-adjustable prefabricated rebar truss composite floor was proposed. In order to study the mechanical properties of the composite floor, the accumulated strain of the reinforcement and deflection in the construction stage of two floors were measured and the static bearing capacity test in the use stage was carried out, and the crack distribution, rebar's strain and deflection of the two slabs were analyzed. The results showed that the longitudinal reinforced bars did not yield under design load, and the floor was in the stage of cracking elasticity and had a large strength surplus. From yield to failure, there was a certain safety reserve. After reaching the ultimate load, there was no brittle failure and it had good ductility. Through theoretical analysis and test results, the simplified formula of short-term stiffness of the composite floor in use stage was studied, and different calculation methods were compared.
Rebar truss composite floor has good mechanical properties, less formwork, and good overall performance and seismic performance, and was widely used in prefabricated steel structures. However, the beams, walls and floors were separately poured into concrete in concrete structure, and the top surface of beams or walls was not flat. The height and position of traditional composite floor were difficult to be adjusted to and reach the predetermined elevation, which affected the assembly effect and construction quality. Therefore, the height-adjustable prefabricated rebar truss composite floor was proposed. In order to study the mechanical properties of the composite floor, the accumulated strain of the reinforcement and deflection in the construction stage of two floors were measured and the static bearing capacity test in the use stage was carried out, and the crack distribution, rebar's strain and deflection of the two slabs were analyzed. The results showed that the longitudinal reinforced bars did not yield under design load, and the floor was in the stage of cracking elasticity and had a large strength surplus. From yield to failure, there was a certain safety reserve. After reaching the ultimate load, there was no brittle failure and it had good ductility. Through theoretical analysis and test results, the simplified formula of short-term stiffness of the composite floor in use stage was studied, and different calculation methods were compared.
2020, 50(4): 19-23.
doi: 10.13204/j.gyjz202004004
Abstract:
As a new bridge structure component, the GQFGJX improved modular expansion device has been widely used in the Liupanshui-Weining section of Duyun highway to Shangri-La. Three full-scale test models were established for the middle beam and cross beam of this new expansion device, and static load test was carried out in order to study whether the strength and stiffness of the middle beam and cross beam selected by the new expansion device under vehicle load could meet the requirements of General specifications for Design of Highway Bridges and Culverts(JTG D60-2015). The results showed that the external bending stiffness of the middle beam was generally less than the internal bending stiffness. The ultimate failure mode of the expansion device under vehicle load was the instable failure of the middle beam caused by the out-of-plane buckling in mid-span. When the beam spacing was not more than 1.8 m, the stiffness and strength of the middle beam and the cross beam could meet the requirements of JTG D60-2015. Reducing the cross beam spacing could significantly improve the bearing capacity of the expansion device.
As a new bridge structure component, the GQFGJX improved modular expansion device has been widely used in the Liupanshui-Weining section of Duyun highway to Shangri-La. Three full-scale test models were established for the middle beam and cross beam of this new expansion device, and static load test was carried out in order to study whether the strength and stiffness of the middle beam and cross beam selected by the new expansion device under vehicle load could meet the requirements of General specifications for Design of Highway Bridges and Culverts(JTG D60-2015). The results showed that the external bending stiffness of the middle beam was generally less than the internal bending stiffness. The ultimate failure mode of the expansion device under vehicle load was the instable failure of the middle beam caused by the out-of-plane buckling in mid-span. When the beam spacing was not more than 1.8 m, the stiffness and strength of the middle beam and the cross beam could meet the requirements of JTG D60-2015. Reducing the cross beam spacing could significantly improve the bearing capacity of the expansion device.
2020, 50(4): 24-29.
doi: 10.13204/j.gyjz202004005
Abstract:
Different from common seismic structures, due to the vertical deformation of the isolation bearing, certain rigid body rotation will occur in the base-isolated structure under the action of earthquake, thus affecting the lateral stiffness of the superstructure. Moreover,the rigid body rotation is particularly obvious in the shear wall structure. ABAQUS finite element analysis software was used to conduct the nonlinear finite element analysis of the coupled shear wall structure with base isolation. By changing the ratio of tensile and compressive stiffness of the isolation bearings, axial compression ratio and height-width ratio of the walls, thirty finite element models were established to analyze the influence of the rotation of the isolation layer caused by the vertical deformation of the isolation bearing on the seismic performance of the coupled shear wall isolation structure. The results showed that increasing the stiffness ratio and the axial compression ratio, decreasing the height-width ratio could reduce the rotation of the superstructure caused by the vertical deformation of the isolation bearing. Due to the influence of the rotation of the superstructure, the lateral stiffness of the isolated superstructure was obviously lower than seismic structure under the same condition, therefore attention should be paid in engineering design.
Different from common seismic structures, due to the vertical deformation of the isolation bearing, certain rigid body rotation will occur in the base-isolated structure under the action of earthquake, thus affecting the lateral stiffness of the superstructure. Moreover,the rigid body rotation is particularly obvious in the shear wall structure. ABAQUS finite element analysis software was used to conduct the nonlinear finite element analysis of the coupled shear wall structure with base isolation. By changing the ratio of tensile and compressive stiffness of the isolation bearings, axial compression ratio and height-width ratio of the walls, thirty finite element models were established to analyze the influence of the rotation of the isolation layer caused by the vertical deformation of the isolation bearing on the seismic performance of the coupled shear wall isolation structure. The results showed that increasing the stiffness ratio and the axial compression ratio, decreasing the height-width ratio could reduce the rotation of the superstructure caused by the vertical deformation of the isolation bearing. Due to the influence of the rotation of the superstructure, the lateral stiffness of the isolated superstructure was obviously lower than seismic structure under the same condition, therefore attention should be paid in engineering design.
2020, 50(4): 30-38.
doi: 10.13204/j.gyjz202004006
Abstract:
In order to verify the damping effect of the suspended coal bucket TMD on the structure of the thermal power plant, a structural finite element model was established to compare the damping effects of the one-way and two-way seismic action, and a structural test model with a scale ratio of 1:12 was fabricated. Two-way shaking table test of different seismic waves under three-level earthquake intensity was conducted, and a comparison test of a conventional scheme of fixing the coal bucket and the floor, and a scheme of the hanging coal bucket TMD scheme using elastic and damping elements connected to the floor was performed, in which multiple earthquakes occur. In addition, the comparison test of the damping effect of the suspension coal bucket TMD with or without damping was carried out. The results showed that the coupling effect of the X and Y directions of the hanging coal bucket TMD was small, and it could be independent of the X and Y directions of the structure based on the TMD theory. The parameter optimization was carried out, and the optimized suspension coal bucket TMD had a remarkable effect on the structural displacement control under different levels of action, and had good control effect on the acceleration under multiple earthquake levels, and the displacement and acceleration of the damped suspension coal bucket TMD structure were reduced. The seismic effect was better than that of the undamped suspension coal bucket TMD structure.
In order to verify the damping effect of the suspended coal bucket TMD on the structure of the thermal power plant, a structural finite element model was established to compare the damping effects of the one-way and two-way seismic action, and a structural test model with a scale ratio of 1:12 was fabricated. Two-way shaking table test of different seismic waves under three-level earthquake intensity was conducted, and a comparison test of a conventional scheme of fixing the coal bucket and the floor, and a scheme of the hanging coal bucket TMD scheme using elastic and damping elements connected to the floor was performed, in which multiple earthquakes occur. In addition, the comparison test of the damping effect of the suspension coal bucket TMD with or without damping was carried out. The results showed that the coupling effect of the X and Y directions of the hanging coal bucket TMD was small, and it could be independent of the X and Y directions of the structure based on the TMD theory. The parameter optimization was carried out, and the optimized suspension coal bucket TMD had a remarkable effect on the structural displacement control under different levels of action, and had good control effect on the acceleration under multiple earthquake levels, and the displacement and acceleration of the damped suspension coal bucket TMD structure were reduced. The seismic effect was better than that of the undamped suspension coal bucket TMD structure.
2020, 50(4): 39-43,38.
doi: 10.13204/j.gyjz202004007
Abstract:
The model of LNG (liquefied natural gas) storage tank was established by finite element method with the consideration of liquid-structure interaction. The column had the negative vertical displacement constrained by contact algorithm with upward uplift allowed. Then the dynamic analysis of the tank under horizontal unidirectional earthquake was presented. The results were compared with the one under horizontal and vertical earthquake by anchored tank and isolated tank with energy dissipated damper. The discussion was related to the structural displacement, the equivalent stress of tank walls, the internal stress of columns, the base shear force, the overturning moment, the liquid sloshing and the uplift movement. The result showed that uplifting effect of columns resulted in a great reduction of structural stress and vertical earthquake, vertical earthquake had a great impact on seismic responses of the uplift tank on rigid ground.
The model of LNG (liquefied natural gas) storage tank was established by finite element method with the consideration of liquid-structure interaction. The column had the negative vertical displacement constrained by contact algorithm with upward uplift allowed. Then the dynamic analysis of the tank under horizontal unidirectional earthquake was presented. The results were compared with the one under horizontal and vertical earthquake by anchored tank and isolated tank with energy dissipated damper. The discussion was related to the structural displacement, the equivalent stress of tank walls, the internal stress of columns, the base shear force, the overturning moment, the liquid sloshing and the uplift movement. The result showed that uplifting effect of columns resulted in a great reduction of structural stress and vertical earthquake, vertical earthquake had a great impact on seismic responses of the uplift tank on rigid ground.
2020, 50(4): 44-48,65.
doi: 10.13204/j.gyjz202004008
Abstract:
The mechanical properties of long rectangular section poplar columns strengthened with BFRP fiber cloth are different. By respectively pasting at intervals of 1 layer and 2 layers of BFRP on the poplar columns, the axial compression test was conducted, the failure mode, ultimate bearing capacity, load-strain curve, load-displacement curve, ductility and so on were analyzed.The test results showed that the failure mode of long poplar column was bending failure, compared with the long columns without reinforcement, the ultimate bearing capacity of poplar column was improved by 8.75% and 30%, respectively, transverse pasting BFRP fiber cloth could effectively constrain the lateral deformation of poplar column,improve the capacity of vertical deformation,and further improve the ductility.
The mechanical properties of long rectangular section poplar columns strengthened with BFRP fiber cloth are different. By respectively pasting at intervals of 1 layer and 2 layers of BFRP on the poplar columns, the axial compression test was conducted, the failure mode, ultimate bearing capacity, load-strain curve, load-displacement curve, ductility and so on were analyzed.The test results showed that the failure mode of long poplar column was bending failure, compared with the long columns without reinforcement, the ultimate bearing capacity of poplar column was improved by 8.75% and 30%, respectively, transverse pasting BFRP fiber cloth could effectively constrain the lateral deformation of poplar column,improve the capacity of vertical deformation,and further improve the ductility.
2020, 50(4): 49-53.
doi: 10.13204/j.gyjz202004009
Abstract:
In order to study the influence of different confining pressure and consolidation stress ratio on the dynamic strength of red sandstone weathered soil, a series of consolidated undrained triaxial tests were carried out by GDS dynamic triaxial test system under uniaxial loading. The results showed that:the deformation development law of red sandstone weathered soil under cyclic loading was quite different between different consolidation conditions. Under the condition of isotropic consolidation, the increase of confining pressure was helpful to the improvement of dynamic strength.Due to the disintegration and fracturing of red sandstone weathered soil and the shear action of consolidating deviatoric static stress, the dynamic strength of weathered soil under the condition of anisotropic consolidation was less than that under the condition of isotropic consolidation. The effect of different confining pressures on the dynamic stress ratio and vibration frequencies of red sandstone weathered soils were not significant, and the specimens were destroyed within 1 000 cycles. Finally, according to the selected failure criteria, the corresponding dynamic strength curve and dynamic shear strength index were obtained.
In order to study the influence of different confining pressure and consolidation stress ratio on the dynamic strength of red sandstone weathered soil, a series of consolidated undrained triaxial tests were carried out by GDS dynamic triaxial test system under uniaxial loading. The results showed that:the deformation development law of red sandstone weathered soil under cyclic loading was quite different between different consolidation conditions. Under the condition of isotropic consolidation, the increase of confining pressure was helpful to the improvement of dynamic strength.Due to the disintegration and fracturing of red sandstone weathered soil and the shear action of consolidating deviatoric static stress, the dynamic strength of weathered soil under the condition of anisotropic consolidation was less than that under the condition of isotropic consolidation. The effect of different confining pressures on the dynamic stress ratio and vibration frequencies of red sandstone weathered soils were not significant, and the specimens were destroyed within 1 000 cycles. Finally, according to the selected failure criteria, the corresponding dynamic strength curve and dynamic shear strength index were obtained.
2020, 50(4): 54-59,18.
doi: 10.13204/j.gyjz202004010
Abstract:
Prediction about settlement of concrete foundation for transmission line tower is an important basis for designing transmission line. Settlement monitoring of foundation is a common method to detect the inclination of transmission tower. The calculation method of foundation settlement commonly used in engineering is layer-wise summation method, and there are many curve fitting formulas for predicting future settlement based on the existing monitoring settlement. The practical creep settlement algorithm is one with few parameters and clear physical significance. In the paper, the layer-wise summation method, creep settlement practical algorithm, the three-point method and hyperbolic method were used to calculate and predicte the foundation settlement of the overhead transmission tower on the bauxite backfill site in Yangquan, Shanxi. The results showed that the practical creep settlement algorithm had good applicability. In order to solve the problem of credible prediction interval of curve fitting formula, the effective prediction interval principle was given by the practical creep settlement algorithm. At last, the effective prediction time of concrete foundation with given error limit was predicted.
Prediction about settlement of concrete foundation for transmission line tower is an important basis for designing transmission line. Settlement monitoring of foundation is a common method to detect the inclination of transmission tower. The calculation method of foundation settlement commonly used in engineering is layer-wise summation method, and there are many curve fitting formulas for predicting future settlement based on the existing monitoring settlement. The practical creep settlement algorithm is one with few parameters and clear physical significance. In the paper, the layer-wise summation method, creep settlement practical algorithm, the three-point method and hyperbolic method were used to calculate and predicte the foundation settlement of the overhead transmission tower on the bauxite backfill site in Yangquan, Shanxi. The results showed that the practical creep settlement algorithm had good applicability. In order to solve the problem of credible prediction interval of curve fitting formula, the effective prediction interval principle was given by the practical creep settlement algorithm. At last, the effective prediction time of concrete foundation with given error limit was predicted.
2020, 50(4): 60-65.
doi: 10.13204/j.gyjz202004011
Abstract:
Aiming at an actual substation engineering slope treatment, the model tests of the filled slope treated by different geotechnical reinforcement methods were conducted to investigate the vertical settlement and lateral displacement of the slope, and compare the deformation characteristics and stability with the plain slope, ordinary reinforcement slope and wrapped reinforcemant slope by geothextilo.On the basis, the finite element analysis was carried out, and it was found that the reinforcement effect was improved with the increase of loading. Both ordinary reinforcement and wrapped reinforcement could effectively reduce the lateral displacement and the vertical settlement. Reinforcement formed a partition effect on the plastic zone in the slope, and thus improved the stability of slope. The ultimate bearing capacity of the ordinary and wrapped reinforcement was 1.7 and 1.9 times larger than that without reinforcement, respectively, the ultimate bearing capacity of the wrapped was 1.12 times of that the with ordinary.
Aiming at an actual substation engineering slope treatment, the model tests of the filled slope treated by different geotechnical reinforcement methods were conducted to investigate the vertical settlement and lateral displacement of the slope, and compare the deformation characteristics and stability with the plain slope, ordinary reinforcement slope and wrapped reinforcemant slope by geothextilo.On the basis, the finite element analysis was carried out, and it was found that the reinforcement effect was improved with the increase of loading. Both ordinary reinforcement and wrapped reinforcement could effectively reduce the lateral displacement and the vertical settlement. Reinforcement formed a partition effect on the plastic zone in the slope, and thus improved the stability of slope. The ultimate bearing capacity of the ordinary and wrapped reinforcement was 1.7 and 1.9 times larger than that without reinforcement, respectively, the ultimate bearing capacity of the wrapped was 1.12 times of that the with ordinary.
2020, 50(4): 66-70.
doi: 10.13204/j.gyjz202004012
Abstract:
Based on the Guangzhou subway undercrossing structure, the structural deformation of the existing vehicular tunnel and the soil deformation were comprehensively analyzed, and an appropriate plan about the newly-built tunnel was proposed. The main contents of research are as follows:choosing the Guangzhou's 21th huangcun station-world grand station undercrossing the existing vehicular tunnel project used as a research object, a 3D finite element numerical model was established, and discrete element software was used for numerical calculation. The tunneling schemes for the new tunnel with different excavation stagger distance on the left and right lines were proposed, and its effect on the deformation of the tunnel undercrossing the existing vehicular tunnel was studied, so as to obtain an appropriate stagger distance range.
Based on the Guangzhou subway undercrossing structure, the structural deformation of the existing vehicular tunnel and the soil deformation were comprehensively analyzed, and an appropriate plan about the newly-built tunnel was proposed. The main contents of research are as follows:choosing the Guangzhou's 21th huangcun station-world grand station undercrossing the existing vehicular tunnel project used as a research object, a 3D finite element numerical model was established, and discrete element software was used for numerical calculation. The tunneling schemes for the new tunnel with different excavation stagger distance on the left and right lines were proposed, and its effect on the deformation of the tunnel undercrossing the existing vehicular tunnel was studied, so as to obtain an appropriate stagger distance range.
2020, 50(4): 71-75.
doi: 10.13204/j.gyjz202004013
Abstract:
Moso bamboo, reputed as "green steel", has the advantages of light weight, high strength, and being environmental friendly. Moreover, Moso bamboo with high efficiency of carbon sequestration, grows fast can be decomposed and recycled, making it particularly competitive for utilization in developing green energy-saving buildings. However, as a biomass material, the mechanical properties of Moso bamboo has the disadvantage of high discreteness, which has prevented it from being widely used. Non-destructive prediction was conducted on the bamboo specimens from Xianning, Hubei Province. The main variables include internode length, outer perimeter, cross section area, wall thickness, vascular bundles area ratio, and moisture content, etc. Based on the macro and meso characteristies analysis and axial compressive tests, a mathematical model for the bearing capasity of Moso bamboo was developed. The current research work could provide theoretical reference for the application of bamboo in engineering.
Moso bamboo, reputed as "green steel", has the advantages of light weight, high strength, and being environmental friendly. Moreover, Moso bamboo with high efficiency of carbon sequestration, grows fast can be decomposed and recycled, making it particularly competitive for utilization in developing green energy-saving buildings. However, as a biomass material, the mechanical properties of Moso bamboo has the disadvantage of high discreteness, which has prevented it from being widely used. Non-destructive prediction was conducted on the bamboo specimens from Xianning, Hubei Province. The main variables include internode length, outer perimeter, cross section area, wall thickness, vascular bundles area ratio, and moisture content, etc. Based on the macro and meso characteristies analysis and axial compressive tests, a mathematical model for the bearing capasity of Moso bamboo was developed. The current research work could provide theoretical reference for the application of bamboo in engineering.
2020, 50(4): 76-81.
doi: 10.13204/j.gyjz202004014
Abstract:
Geopolymer concrete was prepared with a mixture of high-activity metakaolin excited by fly ash with sodium waterglass (Na2O·mSiO2). The damage degree of geopolymer concrete immersed in the saline solution (3.5% NaCl solution, 3.5% Na2SO4 solution, 3.5% Na2SO4 +3.5% NaCl solution and tap water) after being subjected to freeze-thaw cycles was studied. The changes in the apparent morphology, mass loss rate and relative dynamic elastic modulus of the specimens in each freezing-thawing cycle were analyzed. The results showed that, under the action of salt erosion, with the increase of freezing-thawing times, the phenomenon of slurry spalling on the surface of specimen became more and more obvious, and the loss of mass and relative dynamic elastic modulus was more serious. According to the curve of mass loss rate and relative dynamic modulus of elasticity, it could be seen that the freeze-thaw damage of geopolymer concrete under the same freeze-thaw times in the four kinds of solutions from strong to weak was as follows:compound salt freeze, chloride freeze, water freeze and sulfate freeze. It was indicated that the composite salt environment was the most unfavorable to the frost resistance of geopolymer concrete. The research results can provide some theoretical references for the design of geopolymer concrete structures in saltwater and freeze-thaw environment.
Geopolymer concrete was prepared with a mixture of high-activity metakaolin excited by fly ash with sodium waterglass (Na2O·mSiO2). The damage degree of geopolymer concrete immersed in the saline solution (3.5% NaCl solution, 3.5% Na2SO4 solution, 3.5% Na2SO4 +3.5% NaCl solution and tap water) after being subjected to freeze-thaw cycles was studied. The changes in the apparent morphology, mass loss rate and relative dynamic elastic modulus of the specimens in each freezing-thawing cycle were analyzed. The results showed that, under the action of salt erosion, with the increase of freezing-thawing times, the phenomenon of slurry spalling on the surface of specimen became more and more obvious, and the loss of mass and relative dynamic elastic modulus was more serious. According to the curve of mass loss rate and relative dynamic modulus of elasticity, it could be seen that the freeze-thaw damage of geopolymer concrete under the same freeze-thaw times in the four kinds of solutions from strong to weak was as follows:compound salt freeze, chloride freeze, water freeze and sulfate freeze. It was indicated that the composite salt environment was the most unfavorable to the frost resistance of geopolymer concrete. The research results can provide some theoretical references for the design of geopolymer concrete structures in saltwater and freeze-thaw environment.
2020, 50(4): 82-87.
doi: 10.13204/j.gyjz202004015
Abstract:
In order to solve the problem of premature destruction of concrete drains during sewage treatment, the idea of using ultra high performance concrete (UHPC) instead of ordinary concrete was put forward. For study the feasibility, simulated industrial wastewater solution, inorganic acid solution and organic acid solution were used to simulate sewage condition, the sewage corrosion resistance of UHPC and ordinary concrete were compared. Study result shows UHPC is corrode also, however performs apparently better than ordinary concrete in sewage corrosion resistance. Under organic acid solution that was proved the strongest corrosion solution condition, after 6 months soaking, UHPC still has nearly 70% compressive strength of the pure water condition, while ordinary concrete almost breaking up. The outstanding corrosion resistance against sewage of UHPC due to its dense internal structures and low porosity which could limit the occurrence of corrosion only at the surface. The conclusion was using UHPC instead of ordinary concrete could solve the problem of premature destruction of concrete drains during sewage treatment. Despite UHPC is expensive, the comprehensive cost of UHPC drain pipe in life circle is lower than that made by ordinary concrete due to UHPC drain pipe's thin wall, light weight, longer life and much more lower maintenance frequency.
In order to solve the problem of premature destruction of concrete drains during sewage treatment, the idea of using ultra high performance concrete (UHPC) instead of ordinary concrete was put forward. For study the feasibility, simulated industrial wastewater solution, inorganic acid solution and organic acid solution were used to simulate sewage condition, the sewage corrosion resistance of UHPC and ordinary concrete were compared. Study result shows UHPC is corrode also, however performs apparently better than ordinary concrete in sewage corrosion resistance. Under organic acid solution that was proved the strongest corrosion solution condition, after 6 months soaking, UHPC still has nearly 70% compressive strength of the pure water condition, while ordinary concrete almost breaking up. The outstanding corrosion resistance against sewage of UHPC due to its dense internal structures and low porosity which could limit the occurrence of corrosion only at the surface. The conclusion was using UHPC instead of ordinary concrete could solve the problem of premature destruction of concrete drains during sewage treatment. Despite UHPC is expensive, the comprehensive cost of UHPC drain pipe in life circle is lower than that made by ordinary concrete due to UHPC drain pipe's thin wall, light weight, longer life and much more lower maintenance frequency.
2020, 50(4): 88-92.
doi: 10.13204/j.gyjz202004016
Abstract:
Shotcrete has the advantages of short setting time, high bond strength and good supporting effect. However, there are many disadvantages in the engineering application of shotcrete, such as high rebound ratio and unqualified sprayed quality. This paper took the initial supporting shotcrete of Chongqing Hongyan Village tunnel project as the engineering background. The experimental and numerical simulation methods were used to study the optimum content of fiber in PVA chopped fiber shotcrete and its influence on the shotcrete rebound ratio, the stability of tunnel cavity and the deformation of surrounding rock. The results showed that a certain amount of PVA chopped fibers could reduce the rebound ratio of shotcrete, and the optimum amount of fiber was about 0.132%. Compared with ordinary shotcrete, the PVA chopped fiber shotcrete could reduce the vertical and horizontal displacements when the cavity was unstable, and the maximum reduction could reach 2.0% and 4.3%. The maximum stress of the fiber shotcrete layer could be increased by 14.3% compared with that of ordinary shotcrete.
Shotcrete has the advantages of short setting time, high bond strength and good supporting effect. However, there are many disadvantages in the engineering application of shotcrete, such as high rebound ratio and unqualified sprayed quality. This paper took the initial supporting shotcrete of Chongqing Hongyan Village tunnel project as the engineering background. The experimental and numerical simulation methods were used to study the optimum content of fiber in PVA chopped fiber shotcrete and its influence on the shotcrete rebound ratio, the stability of tunnel cavity and the deformation of surrounding rock. The results showed that a certain amount of PVA chopped fibers could reduce the rebound ratio of shotcrete, and the optimum amount of fiber was about 0.132%. Compared with ordinary shotcrete, the PVA chopped fiber shotcrete could reduce the vertical and horizontal displacements when the cavity was unstable, and the maximum reduction could reach 2.0% and 4.3%. The maximum stress of the fiber shotcrete layer could be increased by 14.3% compared with that of ordinary shotcrete.
2020, 50(4): 93-96.
doi: 10.13204/j.gyjz202004017
Abstract:
In the reconstruction tall-rotating process of the old urban area, it is often necessary to clear the natural or artificial structures that affect the proposed project. How to protect key structures in the process of obstacle clearance has become the focus of attention of structural engineers. Based on the cases of pile pulling construction in soft soil layer of Shanghai with tall-skave drill, the paper discussed the influence of the construction process and accidents on the settlement of the adjacent structures by analyzing the measured data. The analysis results showed that it was necessary to arrange the pile pulling construction process reasonably and deal with the accidents occurred in time in order to control the settlement of adjacent structures.
In the reconstruction tall-rotating process of the old urban area, it is often necessary to clear the natural or artificial structures that affect the proposed project. How to protect key structures in the process of obstacle clearance has become the focus of attention of structural engineers. Based on the cases of pile pulling construction in soft soil layer of Shanghai with tall-skave drill, the paper discussed the influence of the construction process and accidents on the settlement of the adjacent structures by analyzing the measured data. The analysis results showed that it was necessary to arrange the pile pulling construction process reasonably and deal with the accidents occurred in time in order to control the settlement of adjacent structures.
2020, 50(4): 97-102,92.
doi: 10.13204/j.gyjz202004018
Abstract:
Considering the effect of covering membrane based on the cable-supported structure without inner hoop, the collaborative form-finding analysis of the whole model was carried out, and the steps of collaborative form-finding were given. The rationality of the results of the form-finding was demonstrated. Finally, static analysis, parametric analysis and dynamic analysis of the structure were carried out. The results showed that cable-supported membrane roof could resist external loads, but considering the drainage of membrane, folds and the area of single membrane, the structure was more suitable for small and medium span structures. Membrane self-weight, Poisson's ratio and prestress of side cables had little influence on cable-supported membrane roof, but elastic modulus and initial prestress of membrane had great effects on membrane roof. The vibration modes of the structure were mainly upward and downward vibration accompanied by local torsion of planar cable-truss frame, so there were no adverse effect on the force of integral structure.
Considering the effect of covering membrane based on the cable-supported structure without inner hoop, the collaborative form-finding analysis of the whole model was carried out, and the steps of collaborative form-finding were given. The rationality of the results of the form-finding was demonstrated. Finally, static analysis, parametric analysis and dynamic analysis of the structure were carried out. The results showed that cable-supported membrane roof could resist external loads, but considering the drainage of membrane, folds and the area of single membrane, the structure was more suitable for small and medium span structures. Membrane self-weight, Poisson's ratio and prestress of side cables had little influence on cable-supported membrane roof, but elastic modulus and initial prestress of membrane had great effects on membrane roof. The vibration modes of the structure were mainly upward and downward vibration accompanied by local torsion of planar cable-truss frame, so there were no adverse effect on the force of integral structure.
2020, 50(4): 103-110.
doi: 10.13204/j.gyjz202004019
Abstract:
The composite structure which is composed of cable-supported arch truss and single-layer cylindrical reticulated shell structure combines the advantages of cable-supported arch truss structure and single-layer reticulated shell structure, both the horizontal thrust to the supporting and the longitudinal span of the single-layer reticulated shell can be reduced, and the stability of the structure can be improved, resulting in longer span of the structure. Based on a long-span coal shed steel structure roof with a 198 m span, which needs to be supported on 15 m high single-row concrete columns, the design and analysis of the long-span cable-supported arch truss and single-layer cylindrical reticulated shell structure was carried out.After optimizing the prestress of the structure, the static and dynamic characteristics of the structure were analyzed in detail, the feasibility of the structure spanning nearly 200 m span was demonstrated then, and the internal force and deformation distribution of the structure under various possible load conditions were revealed. The ANSYS finite element analysis software was used to calculate both the linear elastic buckling characteristic value of the structure and the ultimate bearing capacity considering the double nonlinearity of material and geometry.
The composite structure which is composed of cable-supported arch truss and single-layer cylindrical reticulated shell structure combines the advantages of cable-supported arch truss structure and single-layer reticulated shell structure, both the horizontal thrust to the supporting and the longitudinal span of the single-layer reticulated shell can be reduced, and the stability of the structure can be improved, resulting in longer span of the structure. Based on a long-span coal shed steel structure roof with a 198 m span, which needs to be supported on 15 m high single-row concrete columns, the design and analysis of the long-span cable-supported arch truss and single-layer cylindrical reticulated shell structure was carried out.After optimizing the prestress of the structure, the static and dynamic characteristics of the structure were analyzed in detail, the feasibility of the structure spanning nearly 200 m span was demonstrated then, and the internal force and deformation distribution of the structure under various possible load conditions were revealed. The ANSYS finite element analysis software was used to calculate both the linear elastic buckling characteristic value of the structure and the ultimate bearing capacity considering the double nonlinearity of material and geometry.
2020, 50(4): 111-117,87.
doi: 10.13204/j.gyjz202004020
Abstract:
In order to study the influence of the stiffness matching relationship between the embedded steel plate and the replaceable toe damper of the steel plate shear wall on its seismic performance, a steel plate shear wall specimen with damper was designed, and the quasi-static load test of the specimen before and after the replacement of the damper was conducted twice. The test results showed that the thickness of the damper web was too large, which caused the embedded steel plate to deform before the damper web, which led to the insufficient energy consumption of the specimen. The thickness of the damper web was reduced,which could improve the energy consumption of the shear wall,but the bearing capacity decreased. It could be proved that the stiffness matching relationship between the embedded steel plate and the damper has a critical impact on the seismic performance of the shear wall, such as bearing capacity, energy consumption and ductility. In order to clarify the reasonable matching relationship, 32 models were established by ABAQUS finite element software for numerical simulation. The stiffness of the damper and the embedded steel plate were changed by changing the thickness of the damper web, the direction of the corrugated rib of the embedded steel plate and the thickness of the steel plate,comparing numerical analysis results and test results showed that the finite element analysis results were in good agreement with the test results, the corrugated ribs in the horizontal direction reduced the bearing capacity of the specimens, when the corrugated ribs were in the vertical direction, the thickness of the embedded steel plate and the damper web was 5 mm and 6 mm respectively, the bearing capacity, the ductility and the seismic behavior of the specimen were better.
In order to study the influence of the stiffness matching relationship between the embedded steel plate and the replaceable toe damper of the steel plate shear wall on its seismic performance, a steel plate shear wall specimen with damper was designed, and the quasi-static load test of the specimen before and after the replacement of the damper was conducted twice. The test results showed that the thickness of the damper web was too large, which caused the embedded steel plate to deform before the damper web, which led to the insufficient energy consumption of the specimen. The thickness of the damper web was reduced,which could improve the energy consumption of the shear wall,but the bearing capacity decreased. It could be proved that the stiffness matching relationship between the embedded steel plate and the damper has a critical impact on the seismic performance of the shear wall, such as bearing capacity, energy consumption and ductility. In order to clarify the reasonable matching relationship, 32 models were established by ABAQUS finite element software for numerical simulation. The stiffness of the damper and the embedded steel plate were changed by changing the thickness of the damper web, the direction of the corrugated rib of the embedded steel plate and the thickness of the steel plate,comparing numerical analysis results and test results showed that the finite element analysis results were in good agreement with the test results, the corrugated ribs in the horizontal direction reduced the bearing capacity of the specimens, when the corrugated ribs were in the vertical direction, the thickness of the embedded steel plate and the damper web was 5 mm and 6 mm respectively, the bearing capacity, the ductility and the seismic behavior of the specimen were better.
2020, 50(4): 118-124.
doi: 10.13204/j.gyjz202004021
Abstract:
The paper presented a new structural form of the floor, M-shaped steel truss floor, to improve the thermal insulation and mechanical properties of the floor. Two M-shaped steel truss floors with different steel thicknesses were designed and static test was carried out. Based on the characteristics of M-shaped steel and combined with the existing theory, the equivalent calculation formula of M-shaped steel truss floor and the calculation formula of the cracking load and bearing capacity of the corresponding floor were proposed. The test results and theoretical calculation results showed that the overall stiffness and bearing capacity of the floor were large enough, and when the uniformly distributed load reached the designed of load value, the mid-span deformation of the floor was so far less than the requirements of Code for Design of Concrete Structures(GB 50010-2010) that it had a large safety reserve; the floor section conforms to the assumption of plane section; the error between theoretical calculation results of peak load and test results was small. The equivalent calculation formula and bearing capacity calculation formula of steel were reasonable and effective.
The paper presented a new structural form of the floor, M-shaped steel truss floor, to improve the thermal insulation and mechanical properties of the floor. Two M-shaped steel truss floors with different steel thicknesses were designed and static test was carried out. Based on the characteristics of M-shaped steel and combined with the existing theory, the equivalent calculation formula of M-shaped steel truss floor and the calculation formula of the cracking load and bearing capacity of the corresponding floor were proposed. The test results and theoretical calculation results showed that the overall stiffness and bearing capacity of the floor were large enough, and when the uniformly distributed load reached the designed of load value, the mid-span deformation of the floor was so far less than the requirements of Code for Design of Concrete Structures(GB 50010-2010) that it had a large safety reserve; the floor section conforms to the assumption of plane section; the error between theoretical calculation results of peak load and test results was small. The equivalent calculation formula and bearing capacity calculation formula of steel were reasonable and effective.
2020, 50(4): 125-131,144.
doi: 10.13204/j.gyjz202004022
Abstract:
In order to study the static bearing capacity of stainless steel bolted T-stub connections, the finite element models were developed to take into account the nonlinear material properties, contact conditions and prying forces. Parametric analyses were carried out to obtain the influence of key parameters on the ultimate resistance of the stainless steel T-stubs. It was revealed that the failure mode of T-stubs changed from the mode of complete yielding of the flange (mode 1) to bolt failure (mode 3) along with the increase of flange thickness. The bearing capacity of T-stub with failure mode 1 or the mode of bolt failure with yielding of the flange (mode 2) were reduced by the increase of the distance from the bolt hole to the web's edge and the decrease of nominal yield strength of the flange material. Moreover, higher value of the bolt diameter resulted in increase of the bearing capacity. Combined with parametric studies, the proposed calculation methods were developed. In view of the considerable strain hardening capacity of stainless steel alloys, the plastic moment of T-stub flange was modified to establish revised design formula.
In order to study the static bearing capacity of stainless steel bolted T-stub connections, the finite element models were developed to take into account the nonlinear material properties, contact conditions and prying forces. Parametric analyses were carried out to obtain the influence of key parameters on the ultimate resistance of the stainless steel T-stubs. It was revealed that the failure mode of T-stubs changed from the mode of complete yielding of the flange (mode 1) to bolt failure (mode 3) along with the increase of flange thickness. The bearing capacity of T-stub with failure mode 1 or the mode of bolt failure with yielding of the flange (mode 2) were reduced by the increase of the distance from the bolt hole to the web's edge and the decrease of nominal yield strength of the flange material. Moreover, higher value of the bolt diameter resulted in increase of the bearing capacity. Combined with parametric studies, the proposed calculation methods were developed. In view of the considerable strain hardening capacity of stainless steel alloys, the plastic moment of T-stub flange was modified to establish revised design formula.
2020, 50(4): 132-137.
doi: 10.13204/j.gyjz202004023
Abstract:
In order to evaluate the influences of time-dependent properties of concrete to composite beams, a finite element numerical analysis was carried out to simulate the long-term performance of steel-concrete composite beams. The long-term properties of concrete was simulated by 3 methods:defining the creep behavior of concrete; effective modulus method; adjusting the shear resistance of interface. Based on the results of test and simulation, a simplified calculation method for the long-term deflection of composite beam was introduced. The results showed that the integral long-term performance of composite beam could be well simulated by all the methods. The method of simply adjusting the shear resistance of interface could not be used for analyzing the distribution of local stress. With comparison to several long-term composite beam experiments, it indicated that the calculating results could agree well with the experimental results.
In order to evaluate the influences of time-dependent properties of concrete to composite beams, a finite element numerical analysis was carried out to simulate the long-term performance of steel-concrete composite beams. The long-term properties of concrete was simulated by 3 methods:defining the creep behavior of concrete; effective modulus method; adjusting the shear resistance of interface. Based on the results of test and simulation, a simplified calculation method for the long-term deflection of composite beam was introduced. The results showed that the integral long-term performance of composite beam could be well simulated by all the methods. The method of simply adjusting the shear resistance of interface could not be used for analyzing the distribution of local stress. With comparison to several long-term composite beam experiments, it indicated that the calculating results could agree well with the experimental results.
2020, 50(4): 138-144.
doi: 10.13204/j.gyjz202004024
Abstract:
Relying on long-span bridges to build tourist platforms and enhance tourist attractions is an important measure to develop tourism resources and jointly seek economic and social utilization. In order to build a sightseeing platform on the top of the pylon of a long-span suspension bridge, elevator wells should be laid on the existing pylons. The layout of elevator shaft will change the shape of tower column and significantly increase the cross section size under wind load, which may affect the safety and serviceability of bridge. In the paper, a two-dimensional RANS equation based on the SST k-ω turbulence model was used to model the flow around the tower shaft (Reynolds number Re=7.7×106) with attached under multi-conditions, and the transverse drag coefficient of the new tower under multi-conditions was obtained. The results showed that the addition of elevators and stairwells led to a significant increase wind load on bridge towers; hollowing out of the connection between elevators and stairwells and original bridge towers and fillet treatment of plane edges and corners could significantly reduce the transverse drag coefficient of bridge towers; the increase of column cross section led to an increase in aerodynamic interference effect between upstream and downstream towers, but this interference effect varied with wind direction angle. In the Wind-Resistent Design Specification for Highway Bridges(JTG/T 3360-01-2018), the recommended values of transverse resistance coefficient based on single bridge tower might be unsafe and could not reflect the interference effect between towers and columns. The significant increase of wind load on bridge towers might lead to insufficient shear bearing capacity of bridge towers and beams. When constructing such sightseeing structures on bridges, attention should be paid to the shear design of cross beams.
Relying on long-span bridges to build tourist platforms and enhance tourist attractions is an important measure to develop tourism resources and jointly seek economic and social utilization. In order to build a sightseeing platform on the top of the pylon of a long-span suspension bridge, elevator wells should be laid on the existing pylons. The layout of elevator shaft will change the shape of tower column and significantly increase the cross section size under wind load, which may affect the safety and serviceability of bridge. In the paper, a two-dimensional RANS equation based on the SST k-ω turbulence model was used to model the flow around the tower shaft (Reynolds number Re=7.7×106) with attached under multi-conditions, and the transverse drag coefficient of the new tower under multi-conditions was obtained. The results showed that the addition of elevators and stairwells led to a significant increase wind load on bridge towers; hollowing out of the connection between elevators and stairwells and original bridge towers and fillet treatment of plane edges and corners could significantly reduce the transverse drag coefficient of bridge towers; the increase of column cross section led to an increase in aerodynamic interference effect between upstream and downstream towers, but this interference effect varied with wind direction angle. In the Wind-Resistent Design Specification for Highway Bridges(JTG/T 3360-01-2018), the recommended values of transverse resistance coefficient based on single bridge tower might be unsafe and could not reflect the interference effect between towers and columns. The significant increase of wind load on bridge towers might lead to insufficient shear bearing capacity of bridge towers and beams. When constructing such sightseeing structures on bridges, attention should be paid to the shear design of cross beams.
2020, 50(4): 145-150.
doi: 10.13204/j.gyjz202004025
Abstract:
In Eurocode 4, adverse effects of creep are expressed as the reduction factor of concrete elastic modulus, which is the function of time including a constant creep multiplier and creep coefficient. However, the constant creep multiplier can not reflect important factors such as the beam height, it is necessary to derive analytical formula as a supplement. Based on Dischinger creep differential constitutive equation, formulas of axial creep multiplier and bending creep multiplier were derived after a reasonable simplification, which could be used to transform the area and moment of inertia of concrete into those of the equivalent steel respectively. Through the computer solution of differential equations, the two formulas were verified. Parameter analysis was carried out on the beam height, the results showed that reduction factor in Eurocode 4 was recommended for the conformity with the time-dependent law of composite beams, but it underestimated the adverse impact and the errors increased with the increased of steel beam height.
In Eurocode 4, adverse effects of creep are expressed as the reduction factor of concrete elastic modulus, which is the function of time including a constant creep multiplier and creep coefficient. However, the constant creep multiplier can not reflect important factors such as the beam height, it is necessary to derive analytical formula as a supplement. Based on Dischinger creep differential constitutive equation, formulas of axial creep multiplier and bending creep multiplier were derived after a reasonable simplification, which could be used to transform the area and moment of inertia of concrete into those of the equivalent steel respectively. Through the computer solution of differential equations, the two formulas were verified. Parameter analysis was carried out on the beam height, the results showed that reduction factor in Eurocode 4 was recommended for the conformity with the time-dependent law of composite beams, but it underestimated the adverse impact and the errors increased with the increased of steel beam height.
2020, 50(4): 151-155.
doi: 10.13204/j.gyjz202004026
Abstract:
With the consideration of tension stiffness between FRP bars and concrete, a finite strip analysis procedure for FRP bar concrete beams was established and the bending behavior of FRP bar concrete beam was simulated. Based on the numerical results, a simplified trilinear model for moment-curvature of FRP bar concrete beam was proposed and verified. After verification of the calculated results with experimental results, a parametric analysis was conducted.
With the consideration of tension stiffness between FRP bars and concrete, a finite strip analysis procedure for FRP bar concrete beams was established and the bending behavior of FRP bar concrete beam was simulated. Based on the numerical results, a simplified trilinear model for moment-curvature of FRP bar concrete beam was proposed and verified. After verification of the calculated results with experimental results, a parametric analysis was conducted.
2020, 50(4): 156-161,137.
doi: 10.13204/j.gyjz202004027
Abstract:
Through the experimental research on the shear resistance of BFRP (Basalt Fiber-Reinforced Polylmer) reinforced concrete beams considering recycled aggregate replacement ratio, shear span ratio and reinforcement ratio, the effects of crack propagation, failure mode, replacement ratio of recycled coarse aggregate, shear span ratio and reinforcement ratio of BFRP bars on the shear capacity of the beams were analyzed, and the test results were compared with the four national codes of China, America, Japan and Canda. The results showed that there were two kinds of shear failure of recycled concrete beams reinforced with BFRP bars. Nine test beams were shear-compression damage and two test beams were cable-stayed damage; the deflection of BFRP reinforced concrete beams decreased with the increase of BFRP reinforcement ratio and shear span ratio. When the replacement ratio of recycled coarse aggregate was 30% and 60%, the deflection of BFRP reinforced recycled concrete beams was not significantly different from that of BFRP reinforced ordinary concrete beams. The shear capacity of recycled concrete beams reinforced with BFRP bars was lower than that of ordinary concrete beams reinforced with BFRP bars;at present, the calculation value of ACI 440.1R-15 was the most conservative, and GB 50608-2010 and JSCE 1997 took the second place, while CSA.S 806-12 had better consistency and safety in calculating the shear bearing capacity of recycled concrete beams reinforced with BFRP bars.
Through the experimental research on the shear resistance of BFRP (Basalt Fiber-Reinforced Polylmer) reinforced concrete beams considering recycled aggregate replacement ratio, shear span ratio and reinforcement ratio, the effects of crack propagation, failure mode, replacement ratio of recycled coarse aggregate, shear span ratio and reinforcement ratio of BFRP bars on the shear capacity of the beams were analyzed, and the test results were compared with the four national codes of China, America, Japan and Canda. The results showed that there were two kinds of shear failure of recycled concrete beams reinforced with BFRP bars. Nine test beams were shear-compression damage and two test beams were cable-stayed damage; the deflection of BFRP reinforced concrete beams decreased with the increase of BFRP reinforcement ratio and shear span ratio. When the replacement ratio of recycled coarse aggregate was 30% and 60%, the deflection of BFRP reinforced recycled concrete beams was not significantly different from that of BFRP reinforced ordinary concrete beams. The shear capacity of recycled concrete beams reinforced with BFRP bars was lower than that of ordinary concrete beams reinforced with BFRP bars;at present, the calculation value of ACI 440.1R-15 was the most conservative, and GB 50608-2010 and JSCE 1997 took the second place, while CSA.S 806-12 had better consistency and safety in calculating the shear bearing capacity of recycled concrete beams reinforced with BFRP bars.
2020, 50(4): 162-167,150.
doi: 10.13204/j.gyjz202004028
Abstract:
The mechanical properties of composite cross arms made of glass fiber reinforced polymer for 500 kV and 220 kV transmission line were studied. Static test and numerical analysis of two types of composite cross arms under different load conditions were conducted. The bearing capacity and deformation performance of the test models were investigated. The ultimate bearing capacity of composite cross arms was also analyzed. It was revealed that the composite cross arms were globally stable and connections were safe under all experimental load conditions. The numerically and experimentally obtained strain and deformation curves were in good agreement with each other. Meanwhile, the residual strain or deformation of each measured point was negligible after unloading. It was also shown that the composite cross arms were in the elastic working stage and exhibited a satisfactory safety reserve. The ultimate bearing capacity of composite cross arms for 500 kV and 220 kV transmission line were 2.9 times and 1.7 times of design load under the least favorable load condition respectively.
The mechanical properties of composite cross arms made of glass fiber reinforced polymer for 500 kV and 220 kV transmission line were studied. Static test and numerical analysis of two types of composite cross arms under different load conditions were conducted. The bearing capacity and deformation performance of the test models were investigated. The ultimate bearing capacity of composite cross arms was also analyzed. It was revealed that the composite cross arms were globally stable and connections were safe under all experimental load conditions. The numerically and experimentally obtained strain and deformation curves were in good agreement with each other. Meanwhile, the residual strain or deformation of each measured point was negligible after unloading. It was also shown that the composite cross arms were in the elastic working stage and exhibited a satisfactory safety reserve. The ultimate bearing capacity of composite cross arms for 500 kV and 220 kV transmission line were 2.9 times and 1.7 times of design load under the least favorable load condition respectively.
2020, 50(4): 168-174,155.
doi: 10.13204/j.gyjz202004029
Abstract:
In the Forbidden City, the last process of roof construction of an ancient building is that a ceremony named "Helong" is held. In the ceremony, a worker buries a costful box in the middle of the ridge. The box is filled with "Zhenwu", which means goods for exorcism or blessing. To effectively protect Chinese ancient buildings, the costful box, Zhenwu and ceremony of Helong are studied based on engineering practice and historical literature. Results show that material and size of costful box are different for different buildings; the middle of ridge location relates closely to Chinese ancient ideologies of "harmony between nature and human being" and "middle location for winner"; the number of each kind of Zhenwu is usually five, reflecting that "five" meant large amount for ancient Chinese people; the Helong ceremony belongs to Chinese ancient sacrifice culture, the selection of unmarried male worker relates closely to Chinese ancient ideologies such as "education under god", "expelling evil by Yangqi" and so on.
In the Forbidden City, the last process of roof construction of an ancient building is that a ceremony named "Helong" is held. In the ceremony, a worker buries a costful box in the middle of the ridge. The box is filled with "Zhenwu", which means goods for exorcism or blessing. To effectively protect Chinese ancient buildings, the costful box, Zhenwu and ceremony of Helong are studied based on engineering practice and historical literature. Results show that material and size of costful box are different for different buildings; the middle of ridge location relates closely to Chinese ancient ideologies of "harmony between nature and human being" and "middle location for winner"; the number of each kind of Zhenwu is usually five, reflecting that "five" meant large amount for ancient Chinese people; the Helong ceremony belongs to Chinese ancient sacrifice culture, the selection of unmarried male worker relates closely to Chinese ancient ideologies such as "education under god", "expelling evil by Yangqi" and so on.
2020, 50(4): 175-179.
doi: 10.13204/j.gyjz202004030
Abstract:
With the improvement of infrastructure construction, the more complicated infrastructure construction is, the more corresponding risk factors are. In order to create a safe and good construction environment, reduce occurrence of the risks, and enhance the risk management and control awareness of infrastructure staff, the risk control for infrastructure based on the internet of things technology was studied, the risk factors of key construction parts such as high formwork, deep foundation excavation,ect were analyzed, and most of the risks in the construction process were excluded. The intelligent monitoring system introduced in the paper could provide early warning in time before the occurrence of danger, provide early risk warning for the field staff, and also assist the management staff in risk management and control. The automation and real-time characteristics of the internet of things technology improved the frequency of on-site safety monitoring, greatly shorten the time of abnormal response, improved the level of safety monitoring and early warning at construction sites, and formed the overall solution of real-time perception, timely transmission, intelligent identification and analysis of early warning for the risk operation surface of temporary support monitoring in infrastructure construction, which effectively promoted the integration of the internet of things for ubiquitous electric system power and infrastructure work of power transmission and transformation projects.
With the improvement of infrastructure construction, the more complicated infrastructure construction is, the more corresponding risk factors are. In order to create a safe and good construction environment, reduce occurrence of the risks, and enhance the risk management and control awareness of infrastructure staff, the risk control for infrastructure based on the internet of things technology was studied, the risk factors of key construction parts such as high formwork, deep foundation excavation,ect were analyzed, and most of the risks in the construction process were excluded. The intelligent monitoring system introduced in the paper could provide early warning in time before the occurrence of danger, provide early risk warning for the field staff, and also assist the management staff in risk management and control. The automation and real-time characteristics of the internet of things technology improved the frequency of on-site safety monitoring, greatly shorten the time of abnormal response, improved the level of safety monitoring and early warning at construction sites, and formed the overall solution of real-time perception, timely transmission, intelligent identification and analysis of early warning for the risk operation surface of temporary support monitoring in infrastructure construction, which effectively promoted the integration of the internet of things for ubiquitous electric system power and infrastructure work of power transmission and transformation projects.
2020, 50(4): 180-185.
doi: 10.13204/j.gyjz202004031
Abstract:
As a heritage country, Britain has a unique advantage in the quantity and the protection situation of heritage according to the world cultural heritage list. Due to the long process of heritage protection, Britain has its own protection concepts and methods, and has accumulated rich experience in the heritage protection under the cultural dimension. This paper studied the two cultural heritage protection situations of the ancient cities of York and Bath, through the comparative analysis of the buildings, streets and the surrounding environment, and walls, the British cultural heritage protection and inheritance experience was studied from the perspective of historical and cultural, and then the experience enlightenment on cultural heritage protection in our country was also discussed.
As a heritage country, Britain has a unique advantage in the quantity and the protection situation of heritage according to the world cultural heritage list. Due to the long process of heritage protection, Britain has its own protection concepts and methods, and has accumulated rich experience in the heritage protection under the cultural dimension. This paper studied the two cultural heritage protection situations of the ancient cities of York and Bath, through the comparative analysis of the buildings, streets and the surrounding environment, and walls, the British cultural heritage protection and inheritance experience was studied from the perspective of historical and cultural, and then the experience enlightenment on cultural heritage protection in our country was also discussed.
