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2021 Vol. 51, No. 3
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2021, 51(3): 1-7.
doi: 10.13204/j.gyjzG20050501
Abstract:
The paper demonstrated the connotation and method of elastic regeneration of the industrial heritage landscape from the perspective of its duality of aesthetic and functional elasticity. A analytical framework of two-dimensional matrices was constructed from the proposal of linkage analysis on the industrial heritage landscape, and the design strategy of aesthetic and functional duality was obtained. In terms of aesthetic dimensions, three characteristics had been obtained, i.e. the beauty of empty spaces, the beauty of ruins, and the beauty of mash-up. From the perspective of the functional dimension, the elasticity of ecosystem could be enhanced by restoring the environment and adapting to the local ecosystem. The derivative group of linkage was formed. Hence, the economic elasticity was improved and cultural elasticity was enhanced through activated culture innovation.
The paper demonstrated the connotation and method of elastic regeneration of the industrial heritage landscape from the perspective of its duality of aesthetic and functional elasticity. A analytical framework of two-dimensional matrices was constructed from the proposal of linkage analysis on the industrial heritage landscape, and the design strategy of aesthetic and functional duality was obtained. In terms of aesthetic dimensions, three characteristics had been obtained, i.e. the beauty of empty spaces, the beauty of ruins, and the beauty of mash-up. From the perspective of the functional dimension, the elasticity of ecosystem could be enhanced by restoring the environment and adapting to the local ecosystem. The derivative group of linkage was formed. Hence, the economic elasticity was improved and cultural elasticity was enhanced through activated culture innovation.
2021, 51(3): 8-14.
doi: 10.13204/j.gyjzG20041714
Abstract:
Taking the industrial heritage that transformed into culture buildings as examples, the impacts of sharing strategies on industrial heritage reform were studied. By analyzing three cases near the Huangpu River in Shanghai, from the two levels of design and operation, the paper summarized the influences of sharing concepts on project reconstruction. It was found that sharing strategies positively enhanced the efficiency of cultural ecosystem service for the industrial landscape through the design of access, boundaries and places in the outdoor environment. The design indexes related to the outdoor environment were sorted out, and the ways to improve the sustainable performances of the industrial landscape from three aspects of the environment, society and economy were summarized by AHP.
Taking the industrial heritage that transformed into culture buildings as examples, the impacts of sharing strategies on industrial heritage reform were studied. By analyzing three cases near the Huangpu River in Shanghai, from the two levels of design and operation, the paper summarized the influences of sharing concepts on project reconstruction. It was found that sharing strategies positively enhanced the efficiency of cultural ecosystem service for the industrial landscape through the design of access, boundaries and places in the outdoor environment. The design indexes related to the outdoor environment were sorted out, and the ways to improve the sustainable performances of the industrial landscape from three aspects of the environment, society and economy were summarized by AHP.
2021, 51(3): 22-29,109.
doi: 10.13204/j.gyjzG20052806
Abstract:
In the context of the protection and space construction of ancient tomb sites, the research paths of the urban public space and public building landscape were explored, and a reasonable protection model for ancient tomb sites was established. The park landscape was constructed based on smart city concepts and applied by the guidance systems of open space, photovoltaic power generation systems, LED night lighting, and three-dimensional greening. In concept, the protection design of ancient tomb site and landscape reconstruction centered on the unique value of the ancient tomb and combined with the current situation of the site and the technology means a design path was established. including site protection, landscape regeneration and space construction. In practice, the protection of the ancient tomb site should meet the requirements of urban ecologicalization and improve the utilization of space. Based on modem protection methods and the systemization and diversification of "joint intervention", a multi-level design system for site protection based on the unique culture value of the area was constructed.
In the context of the protection and space construction of ancient tomb sites, the research paths of the urban public space and public building landscape were explored, and a reasonable protection model for ancient tomb sites was established. The park landscape was constructed based on smart city concepts and applied by the guidance systems of open space, photovoltaic power generation systems, LED night lighting, and three-dimensional greening. In concept, the protection design of ancient tomb site and landscape reconstruction centered on the unique value of the ancient tomb and combined with the current situation of the site and the technology means a design path was established. including site protection, landscape regeneration and space construction. In practice, the protection of the ancient tomb site should meet the requirements of urban ecologicalization and improve the utilization of space. Based on modem protection methods and the systemization and diversification of "joint intervention", a multi-level design system for site protection based on the unique culture value of the area was constructed.
2021, 51(3): 30-34,90.
doi: 10.13204/j.gyjzG201905170006
Abstract:
The seismic reliability of resident buildings constructed by prefabricated high-rise shear walls is one of the important requirements for the achievement of construction industrialization in China. To deeply understand the mechanical properties of superposed RC coupling beams in prefabricated shear wall structures, the quasi-static loading experiment was conducted on a sub-structure model spatial prefabricated shear wall. By the experiment test, the crack development laws and failure modes of the model were observed, and the influence laws of superposed coupling beams on the seismic performances of the sub-structures for the prefabricated shear walls were analyzed. Finally, according to the observed and analyzed results, the suggestions for reasonable design of superposed coupling beams were proposed.
The seismic reliability of resident buildings constructed by prefabricated high-rise shear walls is one of the important requirements for the achievement of construction industrialization in China. To deeply understand the mechanical properties of superposed RC coupling beams in prefabricated shear wall structures, the quasi-static loading experiment was conducted on a sub-structure model spatial prefabricated shear wall. By the experiment test, the crack development laws and failure modes of the model were observed, and the influence laws of superposed coupling beams on the seismic performances of the sub-structures for the prefabricated shear walls were analyzed. Finally, according to the observed and analyzed results, the suggestions for reasonable design of superposed coupling beams were proposed.
2021, 51(3): 35-41.
doi: 10.13204/j.gyjzG20032209
Abstract:
In order to study the seismic performances of steel-concrete-composite-tube (SRCT) shear walls with horizontal connections, an experiment was conducted on two full-scaled models of SRCT shear walls and a cast-in-situ RC shear wall. The results revealed that the prefabricated SRCT shear walls with the horizontal connection whether in the middle or at the botlom of shear walls all had high bearing capacity, stiffness, ductility and energy dissipation capacity. It showed the reliability of the proposed horizontal connection. Mechanical performances such as bearing capacity, stiffness and energy dissipation capacity of SRCT the shear wall with the horizontal connection in the middle of the wall were basically the same as that of SRCT shear walls without horizontal connections, and the horizontal connection had little impact on the overall seismic performances of the shear wall. Square steel tubes with tie bars could effectively restrain the cracking and crack development of concrete in steel tubes, so that the damage degree of the bases for the wall limbs the SRCT shear walls was much lower than that of the RC shear wall. Meanwhile, the internal and external concrete effectively restrained the buckling of thin-walled steel tubes. SRCT shear walls had two types of failure modes, one kind of failure could effectively make full use of strength of the material and was ideal, the other had brittle failure characteristics and should be avoided.
In order to study the seismic performances of steel-concrete-composite-tube (SRCT) shear walls with horizontal connections, an experiment was conducted on two full-scaled models of SRCT shear walls and a cast-in-situ RC shear wall. The results revealed that the prefabricated SRCT shear walls with the horizontal connection whether in the middle or at the botlom of shear walls all had high bearing capacity, stiffness, ductility and energy dissipation capacity. It showed the reliability of the proposed horizontal connection. Mechanical performances such as bearing capacity, stiffness and energy dissipation capacity of SRCT the shear wall with the horizontal connection in the middle of the wall were basically the same as that of SRCT shear walls without horizontal connections, and the horizontal connection had little impact on the overall seismic performances of the shear wall. Square steel tubes with tie bars could effectively restrain the cracking and crack development of concrete in steel tubes, so that the damage degree of the bases for the wall limbs the SRCT shear walls was much lower than that of the RC shear wall. Meanwhile, the internal and external concrete effectively restrained the buckling of thin-walled steel tubes. SRCT shear walls had two types of failure modes, one kind of failure could effectively make full use of strength of the material and was ideal, the other had brittle failure characteristics and should be avoided.
2021, 51(3): 42-49,21.
doi: 10.13204/j.gyjzGYJZ201908190005
Abstract:
Based on the numerical analysis method, the calculation model of explosion resistance for load-bearing masonry walls was modelled by the software LS-DYNA. The validity of the model and the method of explosive load application were verified by relevant anti-explosion test literatures. The failure modes of walls under explosive loads with different distance proportions and the anti-explosive effect of structured columns with different spacing on walls were studied. The parameter of ratio for the opening width and wall width (θ) was put forward, which could reflect the influences of openings on walls. The dynamic responses of walls with different θ under explosive loads and the effect of setting structural columns as anti-explosion measures were analyzed. The results showed that the explosion resistance of load-bearing masonry walls could be effectively improved by setting structural columns. The spacing of structural columns should not be too large or too small, and the spacing of 3 m was the most reasonable. With the increase of θ, the damage degree of the walls increased. When θ was larger, the damage degree of walls with two small openings was more serious than that of with a large opening. For a wall with a larger θ, the explosion resistance of the wall was obviously enhanced by adding structural columns on both sides and at the opening, but the serious damage could still occur in the wall below the openings. The addition of lintels at the bottom of openings could efficiently control the cracking in walls with smaller openings, but in walls with larger opening, the damage still occured serisusly, the further reinforcing measure should be studied.
Based on the numerical analysis method, the calculation model of explosion resistance for load-bearing masonry walls was modelled by the software LS-DYNA. The validity of the model and the method of explosive load application were verified by relevant anti-explosion test literatures. The failure modes of walls under explosive loads with different distance proportions and the anti-explosive effect of structured columns with different spacing on walls were studied. The parameter of ratio for the opening width and wall width (θ) was put forward, which could reflect the influences of openings on walls. The dynamic responses of walls with different θ under explosive loads and the effect of setting structural columns as anti-explosion measures were analyzed. The results showed that the explosion resistance of load-bearing masonry walls could be effectively improved by setting structural columns. The spacing of structural columns should not be too large or too small, and the spacing of 3 m was the most reasonable. With the increase of θ, the damage degree of the walls increased. When θ was larger, the damage degree of walls with two small openings was more serious than that of with a large opening. For a wall with a larger θ, the explosion resistance of the wall was obviously enhanced by adding structural columns on both sides and at the opening, but the serious damage could still occur in the wall below the openings. The addition of lintels at the bottom of openings could efficiently control the cracking in walls with smaller openings, but in walls with larger opening, the damage still occured serisusly, the further reinforcing measure should be studied.
2021, 51(3): 50-57.
doi: 10.13204/j.gyjzG20022204
Abstract:
The new prefabricated light-gauge steel-concrete composite external wall panel is a new structural thermal-insulated external wall system, with light-gauge steel keel frame as its framework and the external boards of high performance concrete boards connected with the steel keel frame with studs. Thermal-insulated materials and cement fiberboards as internal boards were filled in. The wall panel could be prefabricated in plants and installed in project sites, and played the role of enclosure walls for buildings. Compared the results of the four-point bending tests and finite element simulations, the influence laws of different structural types on flexural performances of wall panels were obtained. Results showed that the wall panels had good overall mechanical properties; the light-gauge steel keel frame could significantly improve the stiffness of the composite wall panels. Besides, the simulation results by FEM showed that the thickness of concrete boards could slightly improve the overall mechanical properties of wall panels, and the thickness of thermal-insulated layer in wall panels had great influence on the bearing capacity of wall panels.
The new prefabricated light-gauge steel-concrete composite external wall panel is a new structural thermal-insulated external wall system, with light-gauge steel keel frame as its framework and the external boards of high performance concrete boards connected with the steel keel frame with studs. Thermal-insulated materials and cement fiberboards as internal boards were filled in. The wall panel could be prefabricated in plants and installed in project sites, and played the role of enclosure walls for buildings. Compared the results of the four-point bending tests and finite element simulations, the influence laws of different structural types on flexural performances of wall panels were obtained. Results showed that the wall panels had good overall mechanical properties; the light-gauge steel keel frame could significantly improve the stiffness of the composite wall panels. Besides, the simulation results by FEM showed that the thickness of concrete boards could slightly improve the overall mechanical properties of wall panels, and the thickness of thermal-insulated layer in wall panels had great influence on the bearing capacity of wall panels.
RESEARCH ON SEISMIC PERFORMANCES OF HYBRID STRUCTURE HEAT ABSORPTION TOWERS BY SHAKING TABLE TESTING
2021, 51(3): 58-64.
doi: 10.13204/j.gyjz201909130001
Abstract:
As a structure with the first safety grade, heat absorption towers are characterized by high positions of cantroids, large loads and low damping. The equipment itself is prone to produce large additional bending moment and whipping effect under the action of earthquake. Therefore, it is very important to study the seismic performances of the structure. A 242.7 m high hybrid structure of heat absorption tower with the concrete bottom and steel top was taken as the research object. According to the results of simulations by SAP 2000, the simplified design scheme of the scale model was determined. The equivalent scale model was designed and processed according to the scale ratio of 1/20 and the shaking table test was conducted under the actions of three directional earthquakes. The dynamic characteristics of the model, the response of acceleration, displacement and strain of the structure under different intensity earthquakes were tested. The rationality of model design and fabrication was verified by finite element analysis, and the damage of the model as well as the regularity of seismic responses were analyzed. The results showed that under the action of frequent occured earthquakes, fortification and rare occured earthquakes, the maximum displacement angles of the structure were 1/516, 1/281 and 1/145 respectively, it showed the seismic performances of the structure generally met the relevant design requirements. The concrete bottom and variable sections in the middle of the tower were relatively weak, and the whipping effect was obvious in steel structure part, which needed to be paid attention to.
As a structure with the first safety grade, heat absorption towers are characterized by high positions of cantroids, large loads and low damping. The equipment itself is prone to produce large additional bending moment and whipping effect under the action of earthquake. Therefore, it is very important to study the seismic performances of the structure. A 242.7 m high hybrid structure of heat absorption tower with the concrete bottom and steel top was taken as the research object. According to the results of simulations by SAP 2000, the simplified design scheme of the scale model was determined. The equivalent scale model was designed and processed according to the scale ratio of 1/20 and the shaking table test was conducted under the actions of three directional earthquakes. The dynamic characteristics of the model, the response of acceleration, displacement and strain of the structure under different intensity earthquakes were tested. The rationality of model design and fabrication was verified by finite element analysis, and the damage of the model as well as the regularity of seismic responses were analyzed. The results showed that under the action of frequent occured earthquakes, fortification and rare occured earthquakes, the maximum displacement angles of the structure were 1/516, 1/281 and 1/145 respectively, it showed the seismic performances of the structure generally met the relevant design requirements. The concrete bottom and variable sections in the middle of the tower were relatively weak, and the whipping effect was obvious in steel structure part, which needed to be paid attention to.
2021, 51(3): 65-70,84.
doi: 10.13204/j.gyjzG20041317
Abstract:
A fall of transportation containers contained spent nuclear fuel would cause serious impact damage to the spent nuclear fuel receiving and storage facilities. To study the properties of impact resistance for different vibration-absorption facilities, the drop-hammer impact tester was used to perform impact tests on 10 different vibration-absorption facilities, in which time-history curves of impacts and impact depths on vibration-absorption facilities in different impact areas taking material strength, thickness of the vibration-absorption layers, material combination types and cross sections of hammers as variables. The test results showed that under the action of impact loads, the specimens exhibited an increase in impact reaction forces and a decrease in deformation of the vibration-absorption layer and impact contact time with the increase of material strength and cross sections of hammers. Laying XPS boards above and below the vibration damping blocks could effectively reduce the peak value of impact reaction, and the XPS board was laid under the block, the specimens exhibited an decrease in impact reaction force in the bottom and a promotion in vibration reduction effect; the dynamic amplification factor γ of the impact dynamic strength ranged from 0.83 to 1.19, and the depth correction factor α of the hammer head was between 0.61 and 0.98.To meet the needs of engineering design, a set of simplified design formulas for vibration reduction facilities was proposed based on the data analysis.
A fall of transportation containers contained spent nuclear fuel would cause serious impact damage to the spent nuclear fuel receiving and storage facilities. To study the properties of impact resistance for different vibration-absorption facilities, the drop-hammer impact tester was used to perform impact tests on 10 different vibration-absorption facilities, in which time-history curves of impacts and impact depths on vibration-absorption facilities in different impact areas taking material strength, thickness of the vibration-absorption layers, material combination types and cross sections of hammers as variables. The test results showed that under the action of impact loads, the specimens exhibited an increase in impact reaction forces and a decrease in deformation of the vibration-absorption layer and impact contact time with the increase of material strength and cross sections of hammers. Laying XPS boards above and below the vibration damping blocks could effectively reduce the peak value of impact reaction, and the XPS board was laid under the block, the specimens exhibited an decrease in impact reaction force in the bottom and a promotion in vibration reduction effect; the dynamic amplification factor γ of the impact dynamic strength ranged from 0.83 to 1.19, and the depth correction factor α of the hammer head was between 0.61 and 0.98.To meet the needs of engineering design, a set of simplified design formulas for vibration reduction facilities was proposed based on the data analysis.
2021, 51(3): 71-76.
doi: 10.13204/j.gyjzG19120303
Abstract:
A composite shear wall reinforced with steel tubes welded with square steel tubes and C type steel was a new type of composite double steel plate shear walls. In order to analyze the influence of welding residual stress on the seismic performances of the walls, a three-dimensional numerical simulation analysis on the new composite shear wall was conducted using the indirect coupling method based on ABAQUS, and the distribution rules and characteristics of welding thermal fields and residual stress fields were obtained. The results indicated the residual stress in the transverse and thickness directions of the walls were so small that it could be ignored during analysis. On the basis, the seismic performances of shear walls with and without longitudinal residual stress were compared, such as hysteresis curves, maximum bearing capacity, elastic stiffness, etc. It was found that due to the redistribution of stress, the welding residual stress had a little effect on the seismic performances of composite shear walls.
A composite shear wall reinforced with steel tubes welded with square steel tubes and C type steel was a new type of composite double steel plate shear walls. In order to analyze the influence of welding residual stress on the seismic performances of the walls, a three-dimensional numerical simulation analysis on the new composite shear wall was conducted using the indirect coupling method based on ABAQUS, and the distribution rules and characteristics of welding thermal fields and residual stress fields were obtained. The results indicated the residual stress in the transverse and thickness directions of the walls were so small that it could be ignored during analysis. On the basis, the seismic performances of shear walls with and without longitudinal residual stress were compared, such as hysteresis curves, maximum bearing capacity, elastic stiffness, etc. It was found that due to the redistribution of stress, the welding residual stress had a little effect on the seismic performances of composite shear walls.
2021, 51(3): 77-84.
doi: 10.13204/j.gyjzG20052008
Abstract:
In structure design of concrete-filled steel tube (CFST) structure of long-span transmission towers, the higher requirements were put forward for the interface bond performance. To study the interface bond performances between LSAW(longitudinally Submerged Arc Welding) steel pipes and concrete, push-out tests based on orthogonal test principles were conducted on nine CFST specimens. The bond mechanisms and distribution laws of bond stress between LSAW steel pipes and concrete were studied. The main and secondary relations and influencing laws of parameters on the bond strength were analyzed. The optimized empirical formulas of bond strength were proposed based on the analysis of orthogonal tests. Test results indicated that curves of bond stress and slip consisted of the adhesive stage, nonlinear initial sliding stage and sliding stage. All curves had a similar rising tendency at the adhesive stage and nonlinear initial sliding stage. And there were three kinds of tendencies at sliding stage, namely, type I-1, Ⅰ-2 and Ⅱ. The type I-1 curve firstly decreased and then kept it stable. The type Ⅰ-2 curve firstly decreased and then possessed a secondary rising branch. The type II curve continued to ascend slowly at the sliding stage. Three kinds of curve tendencies were mainly caused by macro-manufacturing deviations of the LSAW steel pipes. The factors that influenced adhesive strength and ultimate bond strength both were in order of diameter-thickness ratio of steel pipes, concrete strength and interface bond length in terms of importance. The adhesive strength and ultimate bond strength bothdecreased significantly with the increase of diameter-thickness ratios of steel pipes, but increased with the increase of concrete strength. The bond stress at two ends of specimens decreased with the increase of loads, which revealed the failure mechanism that interface peeled off from the both ends to the middle part. A comparison with other literatures verified that the optimized calculation formulas of bond strength had reliability.
In structure design of concrete-filled steel tube (CFST) structure of long-span transmission towers, the higher requirements were put forward for the interface bond performance. To study the interface bond performances between LSAW(longitudinally Submerged Arc Welding) steel pipes and concrete, push-out tests based on orthogonal test principles were conducted on nine CFST specimens. The bond mechanisms and distribution laws of bond stress between LSAW steel pipes and concrete were studied. The main and secondary relations and influencing laws of parameters on the bond strength were analyzed. The optimized empirical formulas of bond strength were proposed based on the analysis of orthogonal tests. Test results indicated that curves of bond stress and slip consisted of the adhesive stage, nonlinear initial sliding stage and sliding stage. All curves had a similar rising tendency at the adhesive stage and nonlinear initial sliding stage. And there were three kinds of tendencies at sliding stage, namely, type I-1, Ⅰ-2 and Ⅱ. The type I-1 curve firstly decreased and then kept it stable. The type Ⅰ-2 curve firstly decreased and then possessed a secondary rising branch. The type II curve continued to ascend slowly at the sliding stage. Three kinds of curve tendencies were mainly caused by macro-manufacturing deviations of the LSAW steel pipes. The factors that influenced adhesive strength and ultimate bond strength both were in order of diameter-thickness ratio of steel pipes, concrete strength and interface bond length in terms of importance. The adhesive strength and ultimate bond strength bothdecreased significantly with the increase of diameter-thickness ratios of steel pipes, but increased with the increase of concrete strength. The bond stress at two ends of specimens decreased with the increase of loads, which revealed the failure mechanism that interface peeled off from the both ends to the middle part. A comparison with other literatures verified that the optimized calculation formulas of bond strength had reliability.
2021, 51(3): 85-90.
doi: 10.13204/j.gyjzG20071204
Abstract:
The contribution of structural members in structural seismic resistance is different. Traditional structural seismic indicators of vulnerability evaluation cannot reflect that characteristics, nor can it accurately and reasonably evaluate the collapse resistance of structures under earthquake action. Under the action of an earthquake, each member of buckling-restrained braces (BRB) steel frames participates in earthquake resistance in different ways. Buckling-restrained braces dissipate seismic energy through axial deformation, beam ends dissipate seismic energy through bending deformation, and frame columns ensure that structures do not collapse through appropriate deformation. The evaluation index and method of vulnerability analysis based on structure member damage for the overall structure of buckling-restrained braced steel frame were proposed. The structural limit state was defined, and the results for seismic vulnerability analysis of buckling-restrained braced steel frame based on different evaluation indicators were compared. The results showed that although buckling-restrained braced steel frames had improved energy-dissipating capacity of structures due to superior deformation capacity of buckling-restrained braces, damaged still occured at beam ends.
The contribution of structural members in structural seismic resistance is different. Traditional structural seismic indicators of vulnerability evaluation cannot reflect that characteristics, nor can it accurately and reasonably evaluate the collapse resistance of structures under earthquake action. Under the action of an earthquake, each member of buckling-restrained braces (BRB) steel frames participates in earthquake resistance in different ways. Buckling-restrained braces dissipate seismic energy through axial deformation, beam ends dissipate seismic energy through bending deformation, and frame columns ensure that structures do not collapse through appropriate deformation. The evaluation index and method of vulnerability analysis based on structure member damage for the overall structure of buckling-restrained braced steel frame were proposed. The structural limit state was defined, and the results for seismic vulnerability analysis of buckling-restrained braced steel frame based on different evaluation indicators were compared. The results showed that although buckling-restrained braced steel frames had improved energy-dissipating capacity of structures due to superior deformation capacity of buckling-restrained braces, damaged still occured at beam ends.
2021, 51(3): 91-97.
doi: 10.13204/j.gyjzG20071608
Abstract:
To study the buckling mode of large-gauge single-angle columns,axial compression tests of 90 columns were conducted. Considering the effect of flexural stiffness and torsional stiffness of supports,the column's flexural slenderness ratios of the non-symmetry axis and torsional slenderness of the symmetry axis were corrected. The study showed that the buckling modes of large single-angle columns were in flexural buckling predominantly. And it's unnecessary for columns below 40 in slenderness ratio to calculate the flexural-torsional buckling capacity. It's safe for engineering projects to only consider the flexural buckling capacity of the columns' minor axis.
To study the buckling mode of large-gauge single-angle columns,axial compression tests of 90 columns were conducted. Considering the effect of flexural stiffness and torsional stiffness of supports,the column's flexural slenderness ratios of the non-symmetry axis and torsional slenderness of the symmetry axis were corrected. The study showed that the buckling modes of large single-angle columns were in flexural buckling predominantly. And it's unnecessary for columns below 40 in slenderness ratio to calculate the flexural-torsional buckling capacity. It's safe for engineering projects to only consider the flexural buckling capacity of the columns' minor axis.
2021, 51(3): 98-103.
doi: 10.13204/j.gyjzG20102707
Abstract:
In order to study the influence of corrosion on the flexural property of H-shaped steel beams, the standard tensile specimens and steel beams were cut off from H-shaped steel members corroded in the atmospheric environment for three years. The monotonic tensile test of corroded steel and bending test of corroded steel beams were conducted. The relations of yield strength, ultimate strength and ductility with section loss ratios of corroded H-shaped steel beams was discussed, and the change low of the yield load and ultimate load of corroded H-shape steel beams with loss rate of strong axis moment of inertia was revealed. The calculation method of flexural capacity of corroded steel beams was proposed. The results showed that with the increase of corrosion degree, the yield strength, ultimate strength, yield strength and ultimate strength of corroded H-shaped steel beams decreased gradually.
In order to study the influence of corrosion on the flexural property of H-shaped steel beams, the standard tensile specimens and steel beams were cut off from H-shaped steel members corroded in the atmospheric environment for three years. The monotonic tensile test of corroded steel and bending test of corroded steel beams were conducted. The relations of yield strength, ultimate strength and ductility with section loss ratios of corroded H-shaped steel beams was discussed, and the change low of the yield load and ultimate load of corroded H-shape steel beams with loss rate of strong axis moment of inertia was revealed. The calculation method of flexural capacity of corroded steel beams was proposed. The results showed that with the increase of corrosion degree, the yield strength, ultimate strength, yield strength and ultimate strength of corroded H-shaped steel beams decreased gradually.
2021, 51(3): 104-109.
doi: 10.13204/j.gyjzG20032501
Abstract:
Based on a scaled model test, the bearing capacity of the joint at the intersection of the tower and cross arm with or without stiffening rings was studied. Combined with finite element analysis (FEA), the contributions of stiffening rings was to joint bearing capacity were analyzed, at the same time, the corresponding mechanisms, effects and failure modes also were analyzed. The results showed that the stiffening rings could increase the compression yield bearing capacity (side pipe) of joints more than 30%, and it could also improve the stress distribution in the tubular walls of main tubes and joint plates. In addition, the FEA results agreed well with the test results, not only on the bearing capacity but also the failure mode, which was helpful for the design and optimization of steel tube transmission towers.
Based on a scaled model test, the bearing capacity of the joint at the intersection of the tower and cross arm with or without stiffening rings was studied. Combined with finite element analysis (FEA), the contributions of stiffening rings was to joint bearing capacity were analyzed, at the same time, the corresponding mechanisms, effects and failure modes also were analyzed. The results showed that the stiffening rings could increase the compression yield bearing capacity (side pipe) of joints more than 30%, and it could also improve the stress distribution in the tubular walls of main tubes and joint plates. In addition, the FEA results agreed well with the test results, not only on the bearing capacity but also the failure mode, which was helpful for the design and optimization of steel tube transmission towers.
2021, 51(3): 110-114.
doi: 10.13204/j.gyjzG19112010
Abstract:
The standing seam metal roof system has the advantages of light weight, large spans, high strength and good waterproof performances. Therefore, it was increasingly used in airports, train stations and stadiums. However, due to the lack of the corresponding design and construction specifications, the disadvantage of the insufficient wind uplift resistance was gradually reflected. Taking the repair and reinforcement project of metal roofs for terminal T2 at Changbei Airport as the research background, the wind uplift resistance of metal roof panels with standing seam systems was tested and evaluated by full-scale tests. The reasonable reinforcement measures of the metal roof with standing seam systems were determined by analyzing failure modes of wind uplift and variation rules of wind uplift resistance for the metal roof panels with standing seam systems in different reinforcement modes. The test results showed that the clamps could effectively improve the wind uplift resistance of HXY-400 standing seam metal roof panels, and its wind uplift resistence was 4.18 times higher than that of the roof panels without clamps. In addition, purlin spacing also had a direct impact on the wind uplift resistance of standing seam metal roof panels.
The standing seam metal roof system has the advantages of light weight, large spans, high strength and good waterproof performances. Therefore, it was increasingly used in airports, train stations and stadiums. However, due to the lack of the corresponding design and construction specifications, the disadvantage of the insufficient wind uplift resistance was gradually reflected. Taking the repair and reinforcement project of metal roofs for terminal T2 at Changbei Airport as the research background, the wind uplift resistance of metal roof panels with standing seam systems was tested and evaluated by full-scale tests. The reasonable reinforcement measures of the metal roof with standing seam systems were determined by analyzing failure modes of wind uplift and variation rules of wind uplift resistance for the metal roof panels with standing seam systems in different reinforcement modes. The test results showed that the clamps could effectively improve the wind uplift resistance of HXY-400 standing seam metal roof panels, and its wind uplift resistence was 4.18 times higher than that of the roof panels without clamps. In addition, purlin spacing also had a direct impact on the wind uplift resistance of standing seam metal roof panels.
2021, 51(3): 115-120.
doi: 10.13204/j.gyjzG20051508
Abstract:
The mechanical properties of T-shaped joints commonly used in steel greenhouses were studied. Firstly, the bearing mechanism of T-shaped joints connected with clamp was analyzed and the fixing device was designed and fabricated. Then, tensile and compressive tests for 6 T-joint specimens of 2 specifications were conducted, and the failure modes, load-displacement curves and ultimate bearing capacity were obtained. At the same time, the software ABAQUS was applied and the interfacial contact and slip phenomena were considered, finite element models of T-shaped joints connected with clamps were established, and the whole process of tension or compression was simulated and compared with the experimental results respectively. The results showed that under compression, the failure mode of the two types of joints were the same, and the bearing capacity of the joints was reduced due to flexural deformation of the transverse steel tube. And the 2 kinds of joints were destroyed in different modes. The bearing capacity of joints with ϕ32 steel tubes reduced with the increase of flexural deformation of the horizontal tube, while the joints with ϕ25 steel tubes reduced due to the tearing of clamps. The reinforcement of clamps could effectively improve the bearing capacity of joints with ϕ25 steel tubes under tension. A measure to increase clamp thickness for joints with ϕ25 steel tubes to 1.48 mm was suggested.
The mechanical properties of T-shaped joints commonly used in steel greenhouses were studied. Firstly, the bearing mechanism of T-shaped joints connected with clamp was analyzed and the fixing device was designed and fabricated. Then, tensile and compressive tests for 6 T-joint specimens of 2 specifications were conducted, and the failure modes, load-displacement curves and ultimate bearing capacity were obtained. At the same time, the software ABAQUS was applied and the interfacial contact and slip phenomena were considered, finite element models of T-shaped joints connected with clamps were established, and the whole process of tension or compression was simulated and compared with the experimental results respectively. The results showed that under compression, the failure mode of the two types of joints were the same, and the bearing capacity of the joints was reduced due to flexural deformation of the transverse steel tube. And the 2 kinds of joints were destroyed in different modes. The bearing capacity of joints with ϕ32 steel tubes reduced with the increase of flexural deformation of the horizontal tube, while the joints with ϕ25 steel tubes reduced due to the tearing of clamps. The reinforcement of clamps could effectively improve the bearing capacity of joints with ϕ25 steel tubes under tension. A measure to increase clamp thickness for joints with ϕ25 steel tubes to 1.48 mm was suggested.
2021, 51(3): 121-127.
doi: 10.13204/j.gyjzG20050604
Abstract:
There is extremely complex interaction between arbors planted on roofs of structures and the structures under wind loads. Base on the roof project of New Baiyun International Airport Traffic Center in Guangzhou, the dynamic characteristics of arbors were tested, a tree-structure interaction model was constructed, the dynamic responses of the structure under the excitation of wind action and arbor vibration were explored, and the parameter analysis of the model was conducted based on model optimization on the interface of arbor bases and plant pools. The analysis results showed that the diameters of arbors were sensitive to the wind-induced acceleration response on the top floor of the structure. Larger diameter arbors would cause the acceleration of structures greater than the limit for the human comfort degrees under the wind load. The problem of comfort degrees out of limits caused by the tree growth should be taken into account in the design of the roof engineering. Considering the SSI effect, the soil in plant pools could be taken as a spring damping system to simplify the complex interaction between trees and soil in the tree pool.The optimization method was verified to be reasonable and feasible.
There is extremely complex interaction between arbors planted on roofs of structures and the structures under wind loads. Base on the roof project of New Baiyun International Airport Traffic Center in Guangzhou, the dynamic characteristics of arbors were tested, a tree-structure interaction model was constructed, the dynamic responses of the structure under the excitation of wind action and arbor vibration were explored, and the parameter analysis of the model was conducted based on model optimization on the interface of arbor bases and plant pools. The analysis results showed that the diameters of arbors were sensitive to the wind-induced acceleration response on the top floor of the structure. Larger diameter arbors would cause the acceleration of structures greater than the limit for the human comfort degrees under the wind load. The problem of comfort degrees out of limits caused by the tree growth should be taken into account in the design of the roof engineering. Considering the SSI effect, the soil in plant pools could be taken as a spring damping system to simplify the complex interaction between trees and soil in the tree pool.The optimization method was verified to be reasonable and feasible.
2021, 51(3): 128-135.
doi: 10.13204/j.gyjz201906030005
Abstract:
In order to meet the isolation demand of large-scale building structures under different earthquake action and long-period ground motion in particular, a new bidirectional variable curvature-friction pendulum bearing (BD VCFPB) was proposed, and designed in detail according to the basic principle of friction-pendulum bearing. Then, the influence of friction coefficients, influence coefficients of curvature, isolation periods and the stress states of polytetrafluoroethylene (PTFE) plates on the properties of the bearings were further studied. Finally, a series of numerical simulations was conducted on the bearing by ABAQUS. The results showed that there was no separation between PTFE plates and sliding surfaces when the length of the contact area for sliders 2r was smaller; the PTFE plates were separated from the sliding surfaces when 2r was larger. The hysteretic curves of the bearings were a little different from the ones of the theoretical model at the design displacement. In the process of the slider sliding from the position of design displacement to the position of equilibrium, the hysteretic curves of the bearings on the convex arc segment were slightly different from the ones of the theoretical model, and the larger the 2r, the greater the difference. But as a whole, the hysteretic curves of the horizontal force and displacement for the bearings agreed well with the ones of the theoretical model.
In order to meet the isolation demand of large-scale building structures under different earthquake action and long-period ground motion in particular, a new bidirectional variable curvature-friction pendulum bearing (BD VCFPB) was proposed, and designed in detail according to the basic principle of friction-pendulum bearing. Then, the influence of friction coefficients, influence coefficients of curvature, isolation periods and the stress states of polytetrafluoroethylene (PTFE) plates on the properties of the bearings were further studied. Finally, a series of numerical simulations was conducted on the bearing by ABAQUS. The results showed that there was no separation between PTFE plates and sliding surfaces when the length of the contact area for sliders 2r was smaller; the PTFE plates were separated from the sliding surfaces when 2r was larger. The hysteretic curves of the bearings were a little different from the ones of the theoretical model at the design displacement. In the process of the slider sliding from the position of design displacement to the position of equilibrium, the hysteretic curves of the bearings on the convex arc segment were slightly different from the ones of the theoretical model, and the larger the 2r, the greater the difference. But as a whole, the hysteretic curves of the horizontal force and displacement for the bearings agreed well with the ones of the theoretical model.
2021, 51(3): 136-141.
doi: 10.13204/j.gyjzG20052107
Abstract:
Through model tests of interaction between lattice beams by prestressed anchorage with different cross sections and spacing of beams, the earth pressure, the strain of rebars in lattice the beams and the tension forces of the anchors were measured, and the influences of the stiffness and spacing on the bottom reaction of lattice beams, the internal forces of lattice beams and tension forces of anchors were analyzed. The results showed that when the stiffness of lattice beams was larger, the reaction on beams was more uniform, the tension forces of the anchors and the deformation of lattice beams were also more uniform, the strain of lattice beams was smaller, while the bending moment in the beams was larger. When the stiffness of lattice beams was the same, the larger the spacing, the greater the difference of tension forces in anchors, the smaller the base reaction, the worse the uniformity of the reaction, and the larger the bending moment of beams. When the amounts of spans were more, the bending moment was smaller.
Through model tests of interaction between lattice beams by prestressed anchorage with different cross sections and spacing of beams, the earth pressure, the strain of rebars in lattice the beams and the tension forces of the anchors were measured, and the influences of the stiffness and spacing on the bottom reaction of lattice beams, the internal forces of lattice beams and tension forces of anchors were analyzed. The results showed that when the stiffness of lattice beams was larger, the reaction on beams was more uniform, the tension forces of the anchors and the deformation of lattice beams were also more uniform, the strain of lattice beams was smaller, while the bending moment in the beams was larger. When the stiffness of lattice beams was the same, the larger the spacing, the greater the difference of tension forces in anchors, the smaller the base reaction, the worse the uniformity of the reaction, and the larger the bending moment of beams. When the amounts of spans were more, the bending moment was smaller.
2021, 51(3): 142-146,152.
doi: 10.13204/j.gyjzG20040811
Abstract:
A composite caisson is one of preferred foundations for transmission-line engineering in soft soil areas. However, the application of composite caissons in soft soil areas is restricted owing to lack of full understanding on bearing characteristics in soft foundation. In order to study the horizontal bearing characteristics of composite caissons in soft foundation, field tests of foundations subjected to horizontal forces at different heights and with different caisson lengths were conducted. The horizontal bearing characteristics, such as base displacement, rotation angles, locations of rotation centers, earth pressure on foundations, etc were analyzed. The main conclusions were concluded:to increase caisson lengths could reduce the maximum additional earth pressure on foundations, but barely improve the horizontal bearing capacity of foundations. The earth pressure on foundations was in a bilinear form, and the zero-pressure points were near geometric axes of foundations. The resultant forces of earth pressure on foundation bases were not zero, which could produce additional axial tensile forces on caisson foundations.
A composite caisson is one of preferred foundations for transmission-line engineering in soft soil areas. However, the application of composite caissons in soft soil areas is restricted owing to lack of full understanding on bearing characteristics in soft foundation. In order to study the horizontal bearing characteristics of composite caissons in soft foundation, field tests of foundations subjected to horizontal forces at different heights and with different caisson lengths were conducted. The horizontal bearing characteristics, such as base displacement, rotation angles, locations of rotation centers, earth pressure on foundations, etc were analyzed. The main conclusions were concluded:to increase caisson lengths could reduce the maximum additional earth pressure on foundations, but barely improve the horizontal bearing capacity of foundations. The earth pressure on foundations was in a bilinear form, and the zero-pressure points were near geometric axes of foundations. The resultant forces of earth pressure on foundation bases were not zero, which could produce additional axial tensile forces on caisson foundations.
2021, 51(3): 147-152.
doi: 10.13204/j.gyjzG20040901
Abstract:
Based on the finite difference software FLAC3D, the numerical simulations of tensile piles and bottom-uplifted piles were conducted. Load-displacement curves, transfer of axial forces characteristics and distribution characteristics of lateral friction for the two types of piles were studied and compared respectively. The results showed that the ultimate bearing capacity of tensile piles was smaller than that of bottom-uplifted piles, and subjected to the same loads, the displacement of tensile piles was larger than that of bottom-uplifted piles. Load-displacement curves were mainly composed of broken lines. In the ultimate state, tensile or bottom-uplifted piles all failed suddenly. The axial forces in bottom-uplifted piles were transferred from the bottom to the top, and the axial forces in tensile piles were from the top to the bottom. For the two types of piles, the forms of axial forces along the shafts were opposite. With the growth of depth, the axial forces of tensile piles decreased, while that of bottom-uplifted piles increased. The lateral friction of tensile piles was similar to that of bottom-uplifted piles, which was smaller on the upper part of piles and larger on the middle and lower part of piles. Subjected to lesser loads, the upper lateral friction on bottom-uplifted piles was larger than that on tensile piles. Subjected to larger loads, except near pile tips, the lateral friction on the whole bottom-uplifted piles was larger than that of tensile piles. The curves on lateral friction and relative displacement between piles and soil were hyperbolic.
Based on the finite difference software FLAC3D, the numerical simulations of tensile piles and bottom-uplifted piles were conducted. Load-displacement curves, transfer of axial forces characteristics and distribution characteristics of lateral friction for the two types of piles were studied and compared respectively. The results showed that the ultimate bearing capacity of tensile piles was smaller than that of bottom-uplifted piles, and subjected to the same loads, the displacement of tensile piles was larger than that of bottom-uplifted piles. Load-displacement curves were mainly composed of broken lines. In the ultimate state, tensile or bottom-uplifted piles all failed suddenly. The axial forces in bottom-uplifted piles were transferred from the bottom to the top, and the axial forces in tensile piles were from the top to the bottom. For the two types of piles, the forms of axial forces along the shafts were opposite. With the growth of depth, the axial forces of tensile piles decreased, while that of bottom-uplifted piles increased. The lateral friction of tensile piles was similar to that of bottom-uplifted piles, which was smaller on the upper part of piles and larger on the middle and lower part of piles. Subjected to lesser loads, the upper lateral friction on bottom-uplifted piles was larger than that on tensile piles. Subjected to larger loads, except near pile tips, the lateral friction on the whole bottom-uplifted piles was larger than that of tensile piles. The curves on lateral friction and relative displacement between piles and soil were hyperbolic.
2021, 51(3): 153-157,97.
doi: 10.13204/j.gyjzG20040904
Abstract:
The experimental analysis on shear and compressive mechanical properties of frozen silty clay in the seasonal frozen soil region of Daqing City was conducted. The variable rules of the cohesion, internal friction angles, shear strength, compressive strength and moisture content at low temperature and the influence of the optimum moisture content on shear strength and compressive strength were obtained, and the variable rules of initial elastic modulus were analyzed. The results showed that the cohesion and internal friction angle of the frozen silty clay presented a variable rule of first increase and then decrease with the increase of the moisture content; the shear strength increased first and then decreased with the increase of the moisture content, and finally tended to be stable; the shear strength was maximum at the optimum moisture content; the compressive strength increased first and then decreased with the increase of the moisture content, the compressive strength was maximum at the moisture content of 25%, and the compressive strength was unrelated to the optimal moisture content; the initial elastic modulus presented a variable rule of first increase and then decrease with the increase of the moisture content.
The experimental analysis on shear and compressive mechanical properties of frozen silty clay in the seasonal frozen soil region of Daqing City was conducted. The variable rules of the cohesion, internal friction angles, shear strength, compressive strength and moisture content at low temperature and the influence of the optimum moisture content on shear strength and compressive strength were obtained, and the variable rules of initial elastic modulus were analyzed. The results showed that the cohesion and internal friction angle of the frozen silty clay presented a variable rule of first increase and then decrease with the increase of the moisture content; the shear strength increased first and then decreased with the increase of the moisture content, and finally tended to be stable; the shear strength was maximum at the optimum moisture content; the compressive strength increased first and then decreased with the increase of the moisture content, the compressive strength was maximum at the moisture content of 25%, and the compressive strength was unrelated to the optimal moisture content; the initial elastic modulus presented a variable rule of first increase and then decrease with the increase of the moisture content.
2021, 51(3): 158-164.
doi: 10.13204/j.gyjzS20052504
Abstract:
Spinning steel pipe piles with enlarged ends, simply named as STG piles, is a new kind of spinning steel pipe piles developed in recent years. It inherits the advantages of traditional spinning steel pipe piles and improves the structure of the traditional pile ends. A new type structure of pile ends with cutting edges and corresponding spiral threads is proposed, which has become one of the most widely used spinning steel pipe piles all over the world. On the basis of summaries to the evolution of spinning steel pipe piles with enlarged ends in Japan, the new type of spinning steel pipe piles developed by Guangxi Shenghu Metal Products Ltd. Company was introduced including the characteristics, scope of application, structure type, design procedure, construction process and guarantee measures under construction. Finally, a practice application of STG piles was introduced briefly.
Spinning steel pipe piles with enlarged ends, simply named as STG piles, is a new kind of spinning steel pipe piles developed in recent years. It inherits the advantages of traditional spinning steel pipe piles and improves the structure of the traditional pile ends. A new type structure of pile ends with cutting edges and corresponding spiral threads is proposed, which has become one of the most widely used spinning steel pipe piles all over the world. On the basis of summaries to the evolution of spinning steel pipe piles with enlarged ends in Japan, the new type of spinning steel pipe piles developed by Guangxi Shenghu Metal Products Ltd. Company was introduced including the characteristics, scope of application, structure type, design procedure, construction process and guarantee measures under construction. Finally, a practice application of STG piles was introduced briefly.
2021, 51(3): 165-169,179.
doi: 10.13204/j.gyjzG20052522
Abstract:
The relation between contents of crystalline or amorphous phase and compressive strength were discussed to further understand the mechanisms of flyash matrix geopolymer. Firstly, a kind of high strength flyash matrix geopolymer was prepared based on parameter optimization for alkaline activators, and specimens of different strength cured in different temperatures and for ages were prepared. Then, the microstructure of the specimens was scanned with SEM; meanwhile, the mineral quantitative ingredients of the geopolymers were analyzed by XRD-Rietveld, and the contents of crystalline or amorphous phase in geopolymers were determined. Based on the XRD results, the correlations between contents of amorphous phase substracts and strength were analyzed. The results showed that the contents of amorphous phase substracts were in a positive correlation with the strength of geoploymers.
The relation between contents of crystalline or amorphous phase and compressive strength were discussed to further understand the mechanisms of flyash matrix geopolymer. Firstly, a kind of high strength flyash matrix geopolymer was prepared based on parameter optimization for alkaline activators, and specimens of different strength cured in different temperatures and for ages were prepared. Then, the microstructure of the specimens was scanned with SEM; meanwhile, the mineral quantitative ingredients of the geopolymers were analyzed by XRD-Rietveld, and the contents of crystalline or amorphous phase in geopolymers were determined. Based on the XRD results, the correlations between contents of amorphous phase substracts and strength were analyzed. The results showed that the contents of amorphous phase substracts were in a positive correlation with the strength of geoploymers.
2021, 51(3): 170-175.
doi: 10.13204/j.gyjzG19090505
Abstract:
Coal gangue sintered composite insulation blocks are new type of wall materials,which integrated the building enclosure and heat preservation. To grasp the mechanical properties of the blocks, tests were conducted, and the compressive strength and flexural strength on three different compression surfaces-the bearing surface, the front and surface of the joint tongue and groove were analyzed. The results showed that the compressive strength on different compression surfaces of composite insulation blocks was different obviously, the strength was the largest for the bearing surface, and the strength was the smallest for the surface of the joint tongue and groove. The flexural strength of composite insulation blocks was affected by its own cracks, and the ratios of bending-compressive strength were more dispersive. The compressive performances of the composite insulation blocks could meet the requirements for the strength grade of the blocks in the bricks & blocks composited insulation materials(GB/T 29060-2012) and the uniform technical code for wall materials used in buildings(GB 50574-2010).
Coal gangue sintered composite insulation blocks are new type of wall materials,which integrated the building enclosure and heat preservation. To grasp the mechanical properties of the blocks, tests were conducted, and the compressive strength and flexural strength on three different compression surfaces-the bearing surface, the front and surface of the joint tongue and groove were analyzed. The results showed that the compressive strength on different compression surfaces of composite insulation blocks was different obviously, the strength was the largest for the bearing surface, and the strength was the smallest for the surface of the joint tongue and groove. The flexural strength of composite insulation blocks was affected by its own cracks, and the ratios of bending-compressive strength were more dispersive. The compressive performances of the composite insulation blocks could meet the requirements for the strength grade of the blocks in the bricks & blocks composited insulation materials(GB/T 29060-2012) and the uniform technical code for wall materials used in buildings(GB 50574-2010).
EXPERIMENTAL RESEARCH ON POISSON'S RATIOS OF 460 MEGAPASCAL HEAT-RESISTING STEEL AT HIGH TEMPERATURE
2021, 51(3): 176-179.
doi: 10.13204/j.gyjzG20072607
Abstract:
In order to measure Poisson's ratios for 460 MPa heat-resisting steel at high temperature, tension and torsion tests for 460 MPa heat-resisting steel at room temperature and high temperatures of 100 to 600℃ were completed on the MTS809 material testing machine. The elastic modulus and shear modulus of the material at different temperatures were measured with using high temperature tension-torsion extensometers. According to the relations between Poisson's ratio and the elastic formation modulus Poisson's ratios of steel at high temperatures were calculated. Poisson's ratios of 460 MPa heat-resisting steel at room temperature were 0.322 measured with radial and axial extensometers, while Poisson's ratios at room temperature were 0.335 measured and calculated in tension and torsion tests,and the error was 4%, which verificed the feasibility of Poisson's ratios measured in tension and torsion tests at high temperature.
In order to measure Poisson's ratios for 460 MPa heat-resisting steel at high temperature, tension and torsion tests for 460 MPa heat-resisting steel at room temperature and high temperatures of 100 to 600℃ were completed on the MTS809 material testing machine. The elastic modulus and shear modulus of the material at different temperatures were measured with using high temperature tension-torsion extensometers. According to the relations between Poisson's ratio and the elastic formation modulus Poisson's ratios of steel at high temperatures were calculated. Poisson's ratios of 460 MPa heat-resisting steel at room temperature were 0.322 measured with radial and axial extensometers, while Poisson's ratios at room temperature were 0.335 measured and calculated in tension and torsion tests,and the error was 4%, which verificed the feasibility of Poisson's ratios measured in tension and torsion tests at high temperature.
2021, 51(3): 180-183,141.
doi: 10.13204/j.gyjzG20052604
Abstract:
To promote the application of corrosion resistant rebars of high performances and reveal the mechanical performances, based on the optimization of welding parameters, the welding process of indirect butt splices in single side welding applied widely in practices was adopted and the welded specimens for three specification rebars ϕ16, ϕ25 and ϕ32 of HRB500a and HRB500c were prepared. The microstructure, mechanical properties of splices of being welded were tested and measured.The test results showed that both steels of HRB500a and HRB500c had good welding performances in cases of reasonable welding rods and welding processes with indirect butt splices in single side welding.
To promote the application of corrosion resistant rebars of high performances and reveal the mechanical performances, based on the optimization of welding parameters, the welding process of indirect butt splices in single side welding applied widely in practices was adopted and the welded specimens for three specification rebars ϕ16, ϕ25 and ϕ32 of HRB500a and HRB500c were prepared. The microstructure, mechanical properties of splices of being welded were tested and measured.The test results showed that both steels of HRB500a and HRB500c had good welding performances in cases of reasonable welding rods and welding processes with indirect butt splices in single side welding.
2021, 51(3): 184-192.
doi: 10.13204/j.gyjzG20081017
Abstract:
To promote the transformation and upgrading of construction industry, it was a key to the introduction and popularization of the Digital Twin in intelligent construction. Firstly, the related connotation, characteristics, development procedures and main application of Digital Twin was introduced, and the five characteristics and development trends of Digital Twin were summarized. The related connotations of intelligent construction, the characteristics of Digital Twin and intelligent construction were analyzed, and the relation between them were summarized. On the basis, the four key problems to be solved in the process of application of Digital Twin in intelligent construction were analyzed. In view of these problems, the framework of Digital Twin applied in the construction stage of intelligent construction was constructed, and the application contents and value of Digital Twin in each stage of intelligent construction were summarized, which could provide theoretical reference to related research and application in the future.
To promote the transformation and upgrading of construction industry, it was a key to the introduction and popularization of the Digital Twin in intelligent construction. Firstly, the related connotation, characteristics, development procedures and main application of Digital Twin was introduced, and the five characteristics and development trends of Digital Twin were summarized. The related connotations of intelligent construction, the characteristics of Digital Twin and intelligent construction were analyzed, and the relation between them were summarized. On the basis, the four key problems to be solved in the process of application of Digital Twin in intelligent construction were analyzed. In view of these problems, the framework of Digital Twin applied in the construction stage of intelligent construction was constructed, and the application contents and value of Digital Twin in each stage of intelligent construction were summarized, which could provide theoretical reference to related research and application in the future.
2021, 51(3): 193-197,164.
doi: 10.13204/j.gyjzG19120107
Abstract:
The issue of crack resistance of dumbbell-shaped block concrete for caps of the newly built Xinhe Bridge in Wuhan was studied, the comprehensive measures were adopted such as techniques of temperature control casting concrete, temperature rise control for hydration heat and shrinkage compensation. The results showed that the key to reducing the temperature of casting concrete was the temperature control of mixing water and coarse aggregate; the temperature rise of concrete for hydration heat could be significantly reduced through circulating hydration heat regulating materials in cooling water pipes; the shrinkage of block concrete during the drop phase of temperature could be significantly compensated by the magnesian expansion agent, however, more stringent insulation measures should be taken to avoid the excessive surface strain difference between the interior and the surface resulting in increased risk of crack. Practice showed that good and precise control measures of temperature and effective compensation measures for concrete shrinkage were the key to crack resistance of block concrete.
The issue of crack resistance of dumbbell-shaped block concrete for caps of the newly built Xinhe Bridge in Wuhan was studied, the comprehensive measures were adopted such as techniques of temperature control casting concrete, temperature rise control for hydration heat and shrinkage compensation. The results showed that the key to reducing the temperature of casting concrete was the temperature control of mixing water and coarse aggregate; the temperature rise of concrete for hydration heat could be significantly reduced through circulating hydration heat regulating materials in cooling water pipes; the shrinkage of block concrete during the drop phase of temperature could be significantly compensated by the magnesian expansion agent, however, more stringent insulation measures should be taken to avoid the excessive surface strain difference between the interior and the surface resulting in increased risk of crack. Practice showed that good and precise control measures of temperature and effective compensation measures for concrete shrinkage were the key to crack resistance of block concrete.
