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2024 Vol. 54, No. 7
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2024, 54(7): 1-12.
doi: 10.3724/j.gyjzG23071702
Abstract:
The mechanical properties of concrete-filled double-skin steel tubular columns stiffened with perforated steel plates was studied. The finite element model was established by ABAQUS software. On the basis of verifying the reliability of the model, the load-displacement curve, stress distribution, failure mode and parameter analysis of the members were carried out. Furthermore, the design method of bearing capacity of concrete-filled double-skin steel tubular columns stiffened by perforated steel plates under axial compression was proposed. The results showed that the perforated steel plate could enhance the joint force and restraint effect of steel tube and concrete. The recommended values of each parameter of the component should be: steel grade Q355, concrete strength grade C60, opening diameter 35 mm, opening spacing 15 mm, stiffened steel plate thickness 5 mm, and the number of stiffened steel plates should be 4, at this time, the bearing capacity could be increased by 9.6% compared with the concrete-filled double-skin steel tube column, and the bearing capacity is only reduced by 1.9% compared with the bearing capacity of the concrete-filled double-skin steel tube column stiffened with steel plates. Therefore, the opening could save steel and ensure a certain bearing capacity. By adding the contribution of the bearing capacity of the stiffened steel plate to the calculation formula in the specification, and considering the influence of the opening diameter on the bearing capacity and the effect of the steel plate on the improvement of the concrete strength, the proposed design method of axial bearing capacity could safely predict its axial bearing capacity.
The mechanical properties of concrete-filled double-skin steel tubular columns stiffened with perforated steel plates was studied. The finite element model was established by ABAQUS software. On the basis of verifying the reliability of the model, the load-displacement curve, stress distribution, failure mode and parameter analysis of the members were carried out. Furthermore, the design method of bearing capacity of concrete-filled double-skin steel tubular columns stiffened by perforated steel plates under axial compression was proposed. The results showed that the perforated steel plate could enhance the joint force and restraint effect of steel tube and concrete. The recommended values of each parameter of the component should be: steel grade Q355, concrete strength grade C60, opening diameter 35 mm, opening spacing 15 mm, stiffened steel plate thickness 5 mm, and the number of stiffened steel plates should be 4, at this time, the bearing capacity could be increased by 9.6% compared with the concrete-filled double-skin steel tube column, and the bearing capacity is only reduced by 1.9% compared with the bearing capacity of the concrete-filled double-skin steel tube column stiffened with steel plates. Therefore, the opening could save steel and ensure a certain bearing capacity. By adding the contribution of the bearing capacity of the stiffened steel plate to the calculation formula in the specification, and considering the influence of the opening diameter on the bearing capacity and the effect of the steel plate on the improvement of the concrete strength, the proposed design method of axial bearing capacity could safely predict its axial bearing capacity.
2024, 54(7): 13-22.
doi: 10.3724/j.gyjzG22102805
Abstract:
A connection method of lengthening the steel tube of concrete-filled double-skin circular steel tube by inner lining tube and threaded connection has been proposed. Taking the length, depth and position of the thread as the basic parameters, 12 concrete-filled double-skin circular steel tube connected by thread through inner lining tube were designed, and the axial compression tests were carried out. By comparing specimens connected by thread with the ordinary specimens and welded specimens, the axial compressive loading-longitudinal compressive displacement curves, axial compressive loading-strain of steel tube curves and failure mode of the specimens were analyzed, and the effects of different parameters on the axial compressive bearing capacity and stiffness of the specimens were studied. The results showed that the axial compressive loading-longitudinal compressive displacement curves of the specimen could be divided into linear elastic stage, elasto-plastic stage, yield-strengthening stage and descending stage within the range of parameters studied. The bearing capacity and stiffness of the specimens connected by thread through inner lining tube were no worse than those of the ordinary specimen or the welded specimens. The bearing capacity and stiffness of the specimens increased with the increase of thread length, and bearing capacity and stiffness of the specimens connected at end section by thread through inner lining tube were higher than those of the specimens connected at middle section by thread through inner lining tube. The calculation method of the axial compressive bearing capacity of concrete-filled double-skin circular steel tube connected by thread through inner lining tube were suggested.
A connection method of lengthening the steel tube of concrete-filled double-skin circular steel tube by inner lining tube and threaded connection has been proposed. Taking the length, depth and position of the thread as the basic parameters, 12 concrete-filled double-skin circular steel tube connected by thread through inner lining tube were designed, and the axial compression tests were carried out. By comparing specimens connected by thread with the ordinary specimens and welded specimens, the axial compressive loading-longitudinal compressive displacement curves, axial compressive loading-strain of steel tube curves and failure mode of the specimens were analyzed, and the effects of different parameters on the axial compressive bearing capacity and stiffness of the specimens were studied. The results showed that the axial compressive loading-longitudinal compressive displacement curves of the specimen could be divided into linear elastic stage, elasto-plastic stage, yield-strengthening stage and descending stage within the range of parameters studied. The bearing capacity and stiffness of the specimens connected by thread through inner lining tube were no worse than those of the ordinary specimen or the welded specimens. The bearing capacity and stiffness of the specimens increased with the increase of thread length, and bearing capacity and stiffness of the specimens connected at end section by thread through inner lining tube were higher than those of the specimens connected at middle section by thread through inner lining tube. The calculation method of the axial compressive bearing capacity of concrete-filled double-skin circular steel tube connected by thread through inner lining tube were suggested.
2024, 54(7): 23-38.
doi: 10.3724/j.gyjzG23072403
Abstract:
A connection joint of concrete-filled double-skin steel tube (CFDST) with through flange stiffeners has been proposed, which effectively reduces construction risks while ensuring the strength and stiffness of the joints. Full-scale specimens were subjected to pure bending tests to investigate their failure modes, bending capacity, and neutral axis position. The finite element software ABAQUS was employed for numerical simulation analysis of the specimens. Combining experimental and numerical simulation results, the stress development process in joints of CFDST with through flange and the load on the bolts were analyzed. The influence of flange thickness, the number of through-stiffeners, stiffener height, and bolt specifications on the bending performance of the joint was analyzed, and recommended ranges for each parameter were suggested. Finally, considering the bending mechanical characteristics of joints of CFDST with through flange stiffeners, a design method for joints was proposed.
A connection joint of concrete-filled double-skin steel tube (CFDST) with through flange stiffeners has been proposed, which effectively reduces construction risks while ensuring the strength and stiffness of the joints. Full-scale specimens were subjected to pure bending tests to investigate their failure modes, bending capacity, and neutral axis position. The finite element software ABAQUS was employed for numerical simulation analysis of the specimens. Combining experimental and numerical simulation results, the stress development process in joints of CFDST with through flange and the load on the bolts were analyzed. The influence of flange thickness, the number of through-stiffeners, stiffener height, and bolt specifications on the bending performance of the joint was analyzed, and recommended ranges for each parameter were suggested. Finally, considering the bending mechanical characteristics of joints of CFDST with through flange stiffeners, a design method for joints was proposed.
2024, 54(7): 39-49.
doi: 10.3724/j.gyjzG23042902
Abstract:
At present, the application of PEC columns in practical engineering is becoming more and more widespread. Compared with H-shaped steel PEC columns, the bearing capacity of Ya-shaped steel PEC columns is improved while combining the advantages of steel tube concrete columns. In order to study the seismic performance of Ya-shaped steel PEC columns, numerical simulations were conducted on 42 specimens under quasi-static loading by using ABAQUS software, with shear-span ratio, axial compression ratio, horizontal reciprocating loading direction, thicknesses of Ya-shaped steel web plates and flanges as parameters. The simulation results showed that the hysteretic performance of the Ya-shaped steel PEC column was good. The final failure mode of the column loaded in the weak axis direction with a strong axis and shear-span ratio of 1.875 or above was the crushing of concrete at the openings on both sides of the column bottom and the bending failure of the Ya-shaped steel buckling. However, the concrete at the middle of the strong axis column bottom without an opening was also severely damaged, and the weak axis column was not significantly damaged; The concrete at the opening of the weak axis column with a shear span ratio below 1.875 was crushed, and there were cross cracks in the concrete at the unopened position. The concrete at the top of the column was also partially damaged, and the steel section was not buckled, indicating shear failure. Through the analysis of the influence of parameters, it was found that increasing the shear span ratio, thicknesses of flanges and webs could improve the ductility, energy dissipation capacity, and reduce the rate of stiffness degradation of the component, but the peak load decreased with the increase of shear-span ratio; the peak load of strong axis columns decreased with increasing axial compression ratio, while the peak load of weak axis columns increased with increasing axial compression ratio when the axial compression ratio was less than 0.3. Finally, a formula for calculating the seismic bearing capacity of Ya-shaped PEC columns under certain conditions was proposed and modified based on the influencing parameters, verifying the reliability of the revised formula and providing a reference for the application of Ya-shaped steel PEC columns in engineering.
At present, the application of PEC columns in practical engineering is becoming more and more widespread. Compared with H-shaped steel PEC columns, the bearing capacity of Ya-shaped steel PEC columns is improved while combining the advantages of steel tube concrete columns. In order to study the seismic performance of Ya-shaped steel PEC columns, numerical simulations were conducted on 42 specimens under quasi-static loading by using ABAQUS software, with shear-span ratio, axial compression ratio, horizontal reciprocating loading direction, thicknesses of Ya-shaped steel web plates and flanges as parameters. The simulation results showed that the hysteretic performance of the Ya-shaped steel PEC column was good. The final failure mode of the column loaded in the weak axis direction with a strong axis and shear-span ratio of 1.875 or above was the crushing of concrete at the openings on both sides of the column bottom and the bending failure of the Ya-shaped steel buckling. However, the concrete at the middle of the strong axis column bottom without an opening was also severely damaged, and the weak axis column was not significantly damaged; The concrete at the opening of the weak axis column with a shear span ratio below 1.875 was crushed, and there were cross cracks in the concrete at the unopened position. The concrete at the top of the column was also partially damaged, and the steel section was not buckled, indicating shear failure. Through the analysis of the influence of parameters, it was found that increasing the shear span ratio, thicknesses of flanges and webs could improve the ductility, energy dissipation capacity, and reduce the rate of stiffness degradation of the component, but the peak load decreased with the increase of shear-span ratio; the peak load of strong axis columns decreased with increasing axial compression ratio, while the peak load of weak axis columns increased with increasing axial compression ratio when the axial compression ratio was less than 0.3. Finally, a formula for calculating the seismic bearing capacity of Ya-shaped PEC columns under certain conditions was proposed and modified based on the influencing parameters, verifying the reliability of the revised formula and providing a reference for the application of Ya-shaped steel PEC columns in engineering.
2024, 54(7): 50-61.
doi: 10.13204/j.gyjzG22101204
Abstract:
The seismic performence of ten reinforced self-stressing steel slag concrete columns confined with circular steel tubes and four reinforced steel slag concrete columns confined with circular tubes under quasi-static loading were tested. The effects of axial compression ratio, shear-span ratio, diameter-thickness ratio and expansion rate on the failure mode and hysteretic behavior were analyzed. The results showed that the flexural failure was observed in all specimens, and the damage was concentrated in the reserved gap. The fullness of the hysteretic curves increased as the decrease in the axial compression ratio, diameter-thickness ratio or the increase in the shear-span ratio and the expansion rate. The bearing capacity of the specimens increased with the increase of the axial compression ratio, diameter-thickness ratio and expansion rate, while the lateral deformation capacity decreased with the increase in axial compression ratio and diameter-thickness ratio. Subsequently, based on the experiment results, the simplified load-displacement skeleton curves were proposed considering the effects of axial compression ratio, shear-span ratio, diameter-thickness ratio and expansion rate. Moreover, according to the degraded tri-linear restoring force model, the hysteretic rules of the specimens were proposed, the restoring force model for reinforced self-stressing steel slag concrete columns confined with circular steel tubes was established, and the calculated results of the restoring force model were in good agreement with the experimental values.
The seismic performence of ten reinforced self-stressing steel slag concrete columns confined with circular steel tubes and four reinforced steel slag concrete columns confined with circular tubes under quasi-static loading were tested. The effects of axial compression ratio, shear-span ratio, diameter-thickness ratio and expansion rate on the failure mode and hysteretic behavior were analyzed. The results showed that the flexural failure was observed in all specimens, and the damage was concentrated in the reserved gap. The fullness of the hysteretic curves increased as the decrease in the axial compression ratio, diameter-thickness ratio or the increase in the shear-span ratio and the expansion rate. The bearing capacity of the specimens increased with the increase of the axial compression ratio, diameter-thickness ratio and expansion rate, while the lateral deformation capacity decreased with the increase in axial compression ratio and diameter-thickness ratio. Subsequently, based on the experiment results, the simplified load-displacement skeleton curves were proposed considering the effects of axial compression ratio, shear-span ratio, diameter-thickness ratio and expansion rate. Moreover, according to the degraded tri-linear restoring force model, the hysteretic rules of the specimens were proposed, the restoring force model for reinforced self-stressing steel slag concrete columns confined with circular steel tubes was established, and the calculated results of the restoring force model were in good agreement with the experimental values.
2024, 54(7): 62-68.
doi: 10.3724/j.gyjzG23010801
Abstract:
The bamboo winding composite pipe is a new type of environmentally-friendly material independently developed in China. In order to study the reinforced thin-walled circular steel tube composite structures, axial compression tests were conducted on the composite specimens, and the failure modes and bearing capacity of the composite specimens were studied. Trends of load versus displacement and strain were analyzed, and a theoretical calculation formula for the axial compression ultimate bearing capacity of the composite specimens was proposed. Finally, ABAQUS finite element software was used to analyze the parametric analysis of the composite specimen, as well as the influence of the thickness of bamboo winding composite pipe and other parameters on the axial compression performance. The experimental results showed that the failure mode of the composite specimens was lateral bending failure in the middle section of the specimen. Compared to pure bamboo winding composite pipes and steel tubes, the ultimate bearing capacity of the composite specimens had increased by 6.5 times and 1.5 times, respectively. The experimental results were in good agreement with the finite element simulation results, and the error between the theoretical calculation bearing capacity formula and the experimental results was 5.9%.
The bamboo winding composite pipe is a new type of environmentally-friendly material independently developed in China. In order to study the reinforced thin-walled circular steel tube composite structures, axial compression tests were conducted on the composite specimens, and the failure modes and bearing capacity of the composite specimens were studied. Trends of load versus displacement and strain were analyzed, and a theoretical calculation formula for the axial compression ultimate bearing capacity of the composite specimens was proposed. Finally, ABAQUS finite element software was used to analyze the parametric analysis of the composite specimen, as well as the influence of the thickness of bamboo winding composite pipe and other parameters on the axial compression performance. The experimental results showed that the failure mode of the composite specimens was lateral bending failure in the middle section of the specimen. Compared to pure bamboo winding composite pipes and steel tubes, the ultimate bearing capacity of the composite specimens had increased by 6.5 times and 1.5 times, respectively. The experimental results were in good agreement with the finite element simulation results, and the error between the theoretical calculation bearing capacity formula and the experimental results was 5.9%.
2024, 54(7): 69-77.
doi: 10.3724/j.gyjzG23112009
Abstract:
The steel-bamboo composite double-chamber box beam is a composite beam made of cold-formed thin-walled steel and restructured bamboo bonded through structural adhesive. The two materials jointly bear stress and coordinate deformation, and have excellent bending properties. Based on the experimental research, ABAQUS software was used to conduct three-dimensional modeling and finite element analysis, and the cohesion model was used to simulate the interaction of the material contact surface. The simulation results were compared with the test results to verify the reliability of the model, and the bending performance of the composite beam was analyzed. The results showed that the failure characteristics of the finite element simulation results were similar to the test results, the change pattern of the maximum deflection in the mid-span was similar, and the average error between the allowable deflection and the deflection under the test limit load was less than 5%; increase the flange thickness, flange width, web height, and the thickness of section steel of the composite beam could effectively improve the bending stiffness and bending load-bearing capacity; in addition, by increasing the web height within a certain range, the composite beam material utilization was higher, that is, for every 1 kg increased in usage, the allowable load and ultimate load would increase by 6.20 kN and 9.34 kN, respectively.
The steel-bamboo composite double-chamber box beam is a composite beam made of cold-formed thin-walled steel and restructured bamboo bonded through structural adhesive. The two materials jointly bear stress and coordinate deformation, and have excellent bending properties. Based on the experimental research, ABAQUS software was used to conduct three-dimensional modeling and finite element analysis, and the cohesion model was used to simulate the interaction of the material contact surface. The simulation results were compared with the test results to verify the reliability of the model, and the bending performance of the composite beam was analyzed. The results showed that the failure characteristics of the finite element simulation results were similar to the test results, the change pattern of the maximum deflection in the mid-span was similar, and the average error between the allowable deflection and the deflection under the test limit load was less than 5%; increase the flange thickness, flange width, web height, and the thickness of section steel of the composite beam could effectively improve the bending stiffness and bending load-bearing capacity; in addition, by increasing the web height within a certain range, the composite beam material utilization was higher, that is, for every 1 kg increased in usage, the allowable load and ultimate load would increase by 6.20 kN and 9.34 kN, respectively.
2024, 54(7): 78-84.
doi: 10.3724/j.gyjzG23031806
Abstract:
In order to study the seismic performance of PC beam-column joints connected with section steel, the general finite element analysis software was used to analyze the seismic performance indexes such as hysteretic curves and skeleton curves of PC beam-column joints connected with section steel. Through comparative analysis and changes of joint parameters, the influence of axial compression ratio of column top and steel strength on seismic performance of joints was discussed. By using the superposition method and curve fitting method, a simplified formula for calculating the total energy consumption of PC beam-column joints connected with section steel was proposed, and the reliability of the formula was verified by calculating with the results of several literature. The research results showed that the seismic performance of PC beam-column joints connected with section steel was good, the concrete strength, steel strength, section steel thickness and beam column section height of the joints had obvious influence on the seismic performance of the joints, and the simplified calculation formula of the total energy consumption of the joints had high calculation accuracy, which can be used for the calculation and analysis of the total energy consumption of PC beam-column joints connected with section steel and cast-in-place reinforced concrete joints.
In order to study the seismic performance of PC beam-column joints connected with section steel, the general finite element analysis software was used to analyze the seismic performance indexes such as hysteretic curves and skeleton curves of PC beam-column joints connected with section steel. Through comparative analysis and changes of joint parameters, the influence of axial compression ratio of column top and steel strength on seismic performance of joints was discussed. By using the superposition method and curve fitting method, a simplified formula for calculating the total energy consumption of PC beam-column joints connected with section steel was proposed, and the reliability of the formula was verified by calculating with the results of several literature. The research results showed that the seismic performance of PC beam-column joints connected with section steel was good, the concrete strength, steel strength, section steel thickness and beam column section height of the joints had obvious influence on the seismic performance of the joints, and the simplified calculation formula of the total energy consumption of the joints had high calculation accuracy, which can be used for the calculation and analysis of the total energy consumption of PC beam-column joints connected with section steel and cast-in-place reinforced concrete joints.
2024, 54(7): 85-94.
doi: 10.13204/j.gyjzG23022602
Abstract:
To study the reliable connection between the steel beam and the composite floor in the prefabricated staggered truss structure system, the paper proposed a joint connection form in which the hollow composite floor and the steel beam formed a composite flat beam. Push-out tests were carried out on 4 groups of 8 steel-concrete composite specimens connected by high-strength bolts, T-shaped connectors, and through-bars, the effects of the diameter of rebars and the presence or absence of T-shaped connectors on the failure mode, load-slip characteristics, and shear capacity of the joints were mainly analyzed. ABAQUS finite element software was used to establish an accurate nonlinear finite element model for the specimens to analyze the transmission mechanism of internal shear force, and the numerical analysis results were compared with the experimental results. The research results showed that the new failure mode of the new type of joints was that the high-strength bolts were sheared at the interface between the T-shaped connector and the steel beam, and brittle failure occurred; the bearing capacity of the component could be significantly improved; the diameter of the through-bar could be increased to improve the shear bearing capacity and shear stiffness of the member. It is recommended to use a through-bar with a diameter of 20 mm.
To study the reliable connection between the steel beam and the composite floor in the prefabricated staggered truss structure system, the paper proposed a joint connection form in which the hollow composite floor and the steel beam formed a composite flat beam. Push-out tests were carried out on 4 groups of 8 steel-concrete composite specimens connected by high-strength bolts, T-shaped connectors, and through-bars, the effects of the diameter of rebars and the presence or absence of T-shaped connectors on the failure mode, load-slip characteristics, and shear capacity of the joints were mainly analyzed. ABAQUS finite element software was used to establish an accurate nonlinear finite element model for the specimens to analyze the transmission mechanism of internal shear force, and the numerical analysis results were compared with the experimental results. The research results showed that the new failure mode of the new type of joints was that the high-strength bolts were sheared at the interface between the T-shaped connector and the steel beam, and brittle failure occurred; the bearing capacity of the component could be significantly improved; the diameter of the through-bar could be increased to improve the shear bearing capacity and shear stiffness of the member. It is recommended to use a through-bar with a diameter of 20 mm.
2024, 54(7): 95-104.
doi: 10.3724/j.gyjzG22101505
Abstract:
Comparing the policy evolution, plot texture and utilization during regeneration of Yanaka in Tokyo and Wudaoying in Beijing, the similarities and differences of the two urban historic conservation neighborhoods were summarized, which could provide inspiration and reference to the analogous regenerative projects in China. In terms of actual measurement data in fields and studying and sorting of literature, the composition of the two urban historic conservation neighborhoods, commercial forms in core streets, the utilization of street space were comparative. The continuation of plot texture was an important condition in maintaining space scales of urban streets. The constitution of residential buildings mixed with commercial facilities was helpful to form a new social network exciting activity of neighborhoods. The way of independent renewal for the residents was conducive to flexibly utilize street space. Therefore, the regeneration of urban historic conservation neighborhoods should attach great importance to active action of participating subjects in shaping neighborhoods and be regulated and guided appropriately under the administrational framework of existing policies.
Comparing the policy evolution, plot texture and utilization during regeneration of Yanaka in Tokyo and Wudaoying in Beijing, the similarities and differences of the two urban historic conservation neighborhoods were summarized, which could provide inspiration and reference to the analogous regenerative projects in China. In terms of actual measurement data in fields and studying and sorting of literature, the composition of the two urban historic conservation neighborhoods, commercial forms in core streets, the utilization of street space were comparative. The continuation of plot texture was an important condition in maintaining space scales of urban streets. The constitution of residential buildings mixed with commercial facilities was helpful to form a new social network exciting activity of neighborhoods. The way of independent renewal for the residents was conducive to flexibly utilize street space. Therefore, the regeneration of urban historic conservation neighborhoods should attach great importance to active action of participating subjects in shaping neighborhoods and be regulated and guided appropriately under the administrational framework of existing policies.
2024, 54(7): 105-112.
doi: 10.3724/j.gyjzG23083025
Abstract:
Taking Chongqing Yidu Power Plant as an example, the paper studied the protection and renewal methods of hydropower industrial heritage from the perspective of scenario theory, and discussed the scenario-based protection and renewal strategy of hydropower industrial heritage from the perspective of scenario theory.In the scene construction, the internal cultural relics resources and available resources of the factory were actively integrated, and the construction process was divided into three steps: carrier optimization, behavior design and value guidance, so as to attract citizens to enhance their vitality and realize the transformation and upgrading of Yingdu Power Plant, aiming to provide a certain reference for the protection and renewal of hydropower industrial heritage.
Taking Chongqing Yidu Power Plant as an example, the paper studied the protection and renewal methods of hydropower industrial heritage from the perspective of scenario theory, and discussed the scenario-based protection and renewal strategy of hydropower industrial heritage from the perspective of scenario theory.In the scene construction, the internal cultural relics resources and available resources of the factory were actively integrated, and the construction process was divided into three steps: carrier optimization, behavior design and value guidance, so as to attract citizens to enhance their vitality and realize the transformation and upgrading of Yingdu Power Plant, aiming to provide a certain reference for the protection and renewal of hydropower industrial heritage.
2024, 54(7): 113-119.
doi: 10.3724/j.gyjzG22010422
Abstract:
As an environmental foundation for the formation and evolution of traditional villages,landscape space is an important place for its sustainable development,and it is also one of the important aspects to be considered in current protection planning and spatial development. Taking the traditional villages in the Xinyang area of Henan Province as the research object,through the analysis methods of nuclear density,elevation,and so on, the traditional villages in the Xinyang area were divided into three types: valley-basin type,hill-basin type and hill-flat type according to the relations between mountains and rivers. After obtaining satellite images through Google maps,field surveys and unmanned aerial vehicles,the plane morphological characteristics of traditional villages under different landform conditions were summarized. The spatial scope and spatial level were defined according to the distance between the village and the water. Finally,the spatial pattern based on the relations of "mountain,water,field and village" was expressed in a graphic method,so as to reveal the formation mechanism of the spatial pattern of different types of villages. The results showed that because of the flat terrain,villages on the plain of hills and often showed a cluster shape and a large number of ponds,forming a spatial pattern of the field-pond-village-pond-field. Hill-basin type villages are mostly located in shallow mountain areas with rich and diverse forms. They are built along the mountain,forming a spatial pattern of the mountain-village-pond-field-river. The valley-basin type villages are mostly developed into belts due to the terrain restriction forming a spatial pattern of the mountain-village-pond-field-river-mountain.
As an environmental foundation for the formation and evolution of traditional villages,landscape space is an important place for its sustainable development,and it is also one of the important aspects to be considered in current protection planning and spatial development. Taking the traditional villages in the Xinyang area of Henan Province as the research object,through the analysis methods of nuclear density,elevation,and so on, the traditional villages in the Xinyang area were divided into three types: valley-basin type,hill-basin type and hill-flat type according to the relations between mountains and rivers. After obtaining satellite images through Google maps,field surveys and unmanned aerial vehicles,the plane morphological characteristics of traditional villages under different landform conditions were summarized. The spatial scope and spatial level were defined according to the distance between the village and the water. Finally,the spatial pattern based on the relations of "mountain,water,field and village" was expressed in a graphic method,so as to reveal the formation mechanism of the spatial pattern of different types of villages. The results showed that because of the flat terrain,villages on the plain of hills and often showed a cluster shape and a large number of ponds,forming a spatial pattern of the field-pond-village-pond-field. Hill-basin type villages are mostly located in shallow mountain areas with rich and diverse forms. They are built along the mountain,forming a spatial pattern of the mountain-village-pond-field-river. The valley-basin type villages are mostly developed into belts due to the terrain restriction forming a spatial pattern of the mountain-village-pond-field-river-mountain.
2024, 54(7): 120-127.
doi: 10.3724/j.gyjzG23050607
Abstract:
Downbursts are extremely destructive weather events that can cause massive damage to buildings. In order to investigate the influence of downburst on the roof of long-span structures, CFD was used to conduct numerical simulations, and Jining North Railway Station was taken as the prototype to explore the influence of wind angle, radial distance, and moving speed of cloud layer on the roof wind pressure. The results showed that, the upper roof of Jining North Railway Station was under negative wind pressure affected by the action of downburst, and the maximum negative wind pressure occurred in the windward area of the roof. The maximum wind pressure appeared at the front edge of the roof when the wind angle was 0°, and its maximum negative wind pressure coefficient could reach about -2.5. The maximum negative wind pressure of the roof of Jining North Railway Station occurred near the radial distance of 1.25Djet, and the leeward area of the upper roof was less affected by the radial distance. The movement of the jet enhanced the negative wind pressure at the windward area of the roof.
Downbursts are extremely destructive weather events that can cause massive damage to buildings. In order to investigate the influence of downburst on the roof of long-span structures, CFD was used to conduct numerical simulations, and Jining North Railway Station was taken as the prototype to explore the influence of wind angle, radial distance, and moving speed of cloud layer on the roof wind pressure. The results showed that, the upper roof of Jining North Railway Station was under negative wind pressure affected by the action of downburst, and the maximum negative wind pressure occurred in the windward area of the roof. The maximum wind pressure appeared at the front edge of the roof when the wind angle was 0°, and its maximum negative wind pressure coefficient could reach about -2.5. The maximum negative wind pressure of the roof of Jining North Railway Station occurred near the radial distance of 1.25Djet, and the leeward area of the upper roof was less affected by the radial distance. The movement of the jet enhanced the negative wind pressure at the windward area of the roof.
2024, 54(7): 128-137.
doi: 10.3724/j.gyjzG21091704
Abstract:
In the high-strength steel frame with Y-shaped eccentrically braces, the energy-consuming beam, which called links, are arranged vertically, and the frame beams are two independent members, so the cross-sectional design is more flexible, and the plastic deformation has less impact on the frame beams and floor slabs, which is easy to repair after the earthquake. The energy-consuming beam sections were designed as ordinary steel with a yield point below 345 MPa to ensure good ductility and energy consumption of the overall structure, while the non-energy-consuming members such as frame beams and columns were designed as high-strength steels, such as Q460 or Q690, to reduce the cross-sectional size of the members ensuring the elastic stress state of the non-energy-consuming members. The length of the links and the number of storeys (height of the structure) were the main factors affecting the performance of the structure. Three sets of prototype structures of high-strength steel frames with Y-shaped eccentric braces with 8, 12 and 16 storeys were designed by the performance-based design method, with each set of link length varying from 700 mm, 900 mm and 1 100 mm, for a total of nine models. The effects of the length of the links and the number of storeys on the failure mode, stiffness, distribution of storey drift and link rotation were investigated by Pushover analysis and dynamic elastoplastic analysis. The results showed that the longer the links, the weaker the lateral stiffness of the structures; the storey drift and the link rotation showed similar distribution patterns for all structures.
In the high-strength steel frame with Y-shaped eccentrically braces, the energy-consuming beam, which called links, are arranged vertically, and the frame beams are two independent members, so the cross-sectional design is more flexible, and the plastic deformation has less impact on the frame beams and floor slabs, which is easy to repair after the earthquake. The energy-consuming beam sections were designed as ordinary steel with a yield point below 345 MPa to ensure good ductility and energy consumption of the overall structure, while the non-energy-consuming members such as frame beams and columns were designed as high-strength steels, such as Q460 or Q690, to reduce the cross-sectional size of the members ensuring the elastic stress state of the non-energy-consuming members. The length of the links and the number of storeys (height of the structure) were the main factors affecting the performance of the structure. Three sets of prototype structures of high-strength steel frames with Y-shaped eccentric braces with 8, 12 and 16 storeys were designed by the performance-based design method, with each set of link length varying from 700 mm, 900 mm and 1 100 mm, for a total of nine models. The effects of the length of the links and the number of storeys on the failure mode, stiffness, distribution of storey drift and link rotation were investigated by Pushover analysis and dynamic elastoplastic analysis. The results showed that the longer the links, the weaker the lateral stiffness of the structures; the storey drift and the link rotation showed similar distribution patterns for all structures.
2024, 54(7): 138-146.
doi: 10.3724/j.gyjzG21110115
Abstract:
In order to study the influence of weak angle steel on the seismic performance of beam-column joints with reinforced webs connected with fully bloted doble-angle steel and the post-earthquake repair level of such joints, two full-scale joint specimens and one repair specimen were designed. The deformation process and failure mode of the joints were studied by quasi-static test and numerical simulation analysis with low quasi-static load applied to the beam ends. The seismic performance indexes such as hysteresis curve, stiffness degradation curve, ductility and energy dissipation were analyzed. The results showed that the failure of joint specimens was mainly concentrated in the position of Angle steel and stiffening rib. The ductility coefficient of joint specimens was 6-9, which had a high ductility level. When the thickness of angle steel increased by 4 mm, the initial stiffness and bearing capacity of the specimen were increased by 73%. The energy dissipation capacity of the repaired joint could reach 80% of the original specimen.
In order to study the influence of weak angle steel on the seismic performance of beam-column joints with reinforced webs connected with fully bloted doble-angle steel and the post-earthquake repair level of such joints, two full-scale joint specimens and one repair specimen were designed. The deformation process and failure mode of the joints were studied by quasi-static test and numerical simulation analysis with low quasi-static load applied to the beam ends. The seismic performance indexes such as hysteresis curve, stiffness degradation curve, ductility and energy dissipation were analyzed. The results showed that the failure of joint specimens was mainly concentrated in the position of Angle steel and stiffening rib. The ductility coefficient of joint specimens was 6-9, which had a high ductility level. When the thickness of angle steel increased by 4 mm, the initial stiffness and bearing capacity of the specimen were increased by 73%. The energy dissipation capacity of the repaired joint could reach 80% of the original specimen.
2024, 54(7): 147-152.
doi: 10.3724/j.gyjzG22081013
Abstract:
Bolt-sphere joints have been widely used in space grid structures to connect members and transfer loads, because of the advantages of clear force and simple installation. However, corrosion is one of the important factors that affect the service life of grid structures. Cyclic spray simulation test was used to study the influence of chloride corrosion on the tensile bearing capacity, failure mode and corrosion mass loss rate of bolt-sphere joints. It was concluded that the tensile bearing capacity of bolt-sphere joints decreased gradually with the increase of corrosion time. In addition, the corrosion mass loss rate of specimens gradually increased with the increase of corrosion time, and as long as the corrosion time was the same, the corrosion mass loss rate of specimen with screw-in defects was not significantly different from that of specimen without screw-in defects. Finally, a model suitable for simulating the tensile bearing capacity of bolt-sphere joints was established by finite element analysis, and the simulated results were in good agreement with the experimental results.
Bolt-sphere joints have been widely used in space grid structures to connect members and transfer loads, because of the advantages of clear force and simple installation. However, corrosion is one of the important factors that affect the service life of grid structures. Cyclic spray simulation test was used to study the influence of chloride corrosion on the tensile bearing capacity, failure mode and corrosion mass loss rate of bolt-sphere joints. It was concluded that the tensile bearing capacity of bolt-sphere joints decreased gradually with the increase of corrosion time. In addition, the corrosion mass loss rate of specimens gradually increased with the increase of corrosion time, and as long as the corrosion time was the same, the corrosion mass loss rate of specimen with screw-in defects was not significantly different from that of specimen without screw-in defects. Finally, a model suitable for simulating the tensile bearing capacity of bolt-sphere joints was established by finite element analysis, and the simulated results were in good agreement with the experimental results.
2024, 54(7): 153-158.
doi: 10.3724/j.gyjzG21102208
Abstract:
The validity of the finite element model was verified by comparing the existing test data and finite element analysis results of T-stubs connected with high-strength bolts. According to the finite element analysis and theoretical analysis, the mechanical model of initial bending stiffness of T-stubs proposed in Eurocode 3 was simplified, and the expression for calculating the effective length of T-stubs in elastic stage was obtained, the calculation formula of initial bending stiffness of T-stubs was derived.Finally, 35 groups of T-stubs considering the changes of flange width, flange thickness, bolt diameter, bolt grade and bolt spacing were selected to carry out finite element parametric analysis. The theoretical calculation results of initial bending stiffness were compared with those of finite element analysis, and the errors were mostly within 15%, which verified the validity of theoretical calculation formula.
The validity of the finite element model was verified by comparing the existing test data and finite element analysis results of T-stubs connected with high-strength bolts. According to the finite element analysis and theoretical analysis, the mechanical model of initial bending stiffness of T-stubs proposed in Eurocode 3 was simplified, and the expression for calculating the effective length of T-stubs in elastic stage was obtained, the calculation formula of initial bending stiffness of T-stubs was derived.Finally, 35 groups of T-stubs considering the changes of flange width, flange thickness, bolt diameter, bolt grade and bolt spacing were selected to carry out finite element parametric analysis. The theoretical calculation results of initial bending stiffness were compared with those of finite element analysis, and the errors were mostly within 15%, which verified the validity of theoretical calculation formula.
2024, 54(7): 159-165.
doi: 10.3724/j.gyjzG21120714
Abstract:
In order to study the mechanical response of insulating laminated glass plates under single-curved cold bending, considering the effects of cold bending radius, glass plate thickness, insulating layer thickness and PVB interlayer thickness, circular arc single-curved cold bending tests were carried out on 12 designed insulating laminated glass plates. The stress distribution of the two tensile surfaces of the specimen and the variation characteristics of the relative slip values between the upper and the bottom glass plates were analyzed, and the effects of different designed factors on the test results were compared. The results showed that the maximum principal tensile stress of single-curved cold-bent insulating laminated glass plates was found at the midpoint of the long side of the outer convex surface, and the average difference of the maximum principal tensile stress between the two tensile surfaces was 15.5%; the interlaminar relative slip value increased nearly linearly with the increase of cold bending displacement; the principal tensile stress and interlaminar relative slip values were most affected by the cold bending radius. The maximum principal tensile stress increased by 101.5% and the interlaminar relative slip value increased by 54.0% as the cold bending radius decreased by 40%; with the increase of glass plate thickness or insulating layer thickness, the cold bending principal tensile stress and the interlaminar relative slip value would increase; the thickness of PVB interlayer had the least influence on the test results.
In order to study the mechanical response of insulating laminated glass plates under single-curved cold bending, considering the effects of cold bending radius, glass plate thickness, insulating layer thickness and PVB interlayer thickness, circular arc single-curved cold bending tests were carried out on 12 designed insulating laminated glass plates. The stress distribution of the two tensile surfaces of the specimen and the variation characteristics of the relative slip values between the upper and the bottom glass plates were analyzed, and the effects of different designed factors on the test results were compared. The results showed that the maximum principal tensile stress of single-curved cold-bent insulating laminated glass plates was found at the midpoint of the long side of the outer convex surface, and the average difference of the maximum principal tensile stress between the two tensile surfaces was 15.5%; the interlaminar relative slip value increased nearly linearly with the increase of cold bending displacement; the principal tensile stress and interlaminar relative slip values were most affected by the cold bending radius. The maximum principal tensile stress increased by 101.5% and the interlaminar relative slip value increased by 54.0% as the cold bending radius decreased by 40%; with the increase of glass plate thickness or insulating layer thickness, the cold bending principal tensile stress and the interlaminar relative slip value would increase; the thickness of PVB interlayer had the least influence on the test results.
2024, 54(7): 166-173.
doi: 10.3724/j.gyjzG23091308
Abstract:
To investigate the mechanical properties of reinforced gypsum beams and analyze the effects of reinforcement ratio and pattern, static loading tests were conducted on seven single-reinforced gypsum beams and five double-reinforced gypsum beams. The test results indicated that both the single-reinforced specimens B1-B5 and the double-reinforced specimens B8 and B9 exhibited bending failure at normal sections as proper reinforced concrete beams, while the single-reinforced specimens B6 and B7 demonstrated bending failure as over-reinforced concrete beams. Due to the low actual strength of gypsum, the shear bearing capacity of the section was relatively low. As a result, specimens B5, B6, and B10 experienced both bending failure and shear failure, and B11 and B12 underwent shear oblique compression failure. The peak bearing capacity of the proper reinforced specimens increased with the increase of the tensile reinforcement ratio, while the displacement ductility coefficient gradually decreased. When the tensile longitudinal reinforcement remained constant, the addition of compressive longitudinal reinforcement could effectively enhance the displacement ductility of the specimens. The reinforced gypsum beam basically conformed to the assumption of a plane section. The maximum crack width and deflection observed in each specimen under service load remained below the specified limit values, indicating that the reinforced gypsum beams satisfactorily met the requirements of the serviceability limit state in Design of Concrete Structures(GB 50010—2010).
To investigate the mechanical properties of reinforced gypsum beams and analyze the effects of reinforcement ratio and pattern, static loading tests were conducted on seven single-reinforced gypsum beams and five double-reinforced gypsum beams. The test results indicated that both the single-reinforced specimens B1-B5 and the double-reinforced specimens B8 and B9 exhibited bending failure at normal sections as proper reinforced concrete beams, while the single-reinforced specimens B6 and B7 demonstrated bending failure as over-reinforced concrete beams. Due to the low actual strength of gypsum, the shear bearing capacity of the section was relatively low. As a result, specimens B5, B6, and B10 experienced both bending failure and shear failure, and B11 and B12 underwent shear oblique compression failure. The peak bearing capacity of the proper reinforced specimens increased with the increase of the tensile reinforcement ratio, while the displacement ductility coefficient gradually decreased. When the tensile longitudinal reinforcement remained constant, the addition of compressive longitudinal reinforcement could effectively enhance the displacement ductility of the specimens. The reinforced gypsum beam basically conformed to the assumption of a plane section. The maximum crack width and deflection observed in each specimen under service load remained below the specified limit values, indicating that the reinforced gypsum beams satisfactorily met the requirements of the serviceability limit state in Design of Concrete Structures(GB 50010—2010).
2024, 54(7): 174-180.
doi: 10.3724/j.gyjzG24011609
Abstract:
A calculation method taking laterally loaded piles as beams on elastic foundation was established, which could consider degradation of bending stiffness of piles after flexural cracking and the non-linear relation between soil resistance and displacement simultaneously. Then, the solution was achieved by the finite difference method. Regardless of the impact of soil, a bending test of a PHC pile as a simple supported beam was simulated. The results indicated that it was reasonable and feasible to simulate nonlinear characteristics of concrete beams on elastic foundation adopting the stiffness degradation model suggested by GB 50010-2010 Code for Design of Concrete Structures (revised in 2015). Further,a laterally loading test of a PHC pile in soft clayey soil was analyzed. It is shown that the curve between horizontal loads at pile heads and displacements considering stiffness degradation of piles was closer to the test results compared with that one only considering the non-linear relation between soil resistance and displacement. The impact of stiffness degradation on laterally loaded reinforced concrete piles was more significant. Therefore, the analysis method was valuable for analyzing laterally loaded test of piles and designing deflection-controlled reinforced concrete piles.
A calculation method taking laterally loaded piles as beams on elastic foundation was established, which could consider degradation of bending stiffness of piles after flexural cracking and the non-linear relation between soil resistance and displacement simultaneously. Then, the solution was achieved by the finite difference method. Regardless of the impact of soil, a bending test of a PHC pile as a simple supported beam was simulated. The results indicated that it was reasonable and feasible to simulate nonlinear characteristics of concrete beams on elastic foundation adopting the stiffness degradation model suggested by GB 50010-2010 Code for Design of Concrete Structures (revised in 2015). Further,a laterally loading test of a PHC pile in soft clayey soil was analyzed. It is shown that the curve between horizontal loads at pile heads and displacements considering stiffness degradation of piles was closer to the test results compared with that one only considering the non-linear relation between soil resistance and displacement. The impact of stiffness degradation on laterally loaded reinforced concrete piles was more significant. Therefore, the analysis method was valuable for analyzing laterally loaded test of piles and designing deflection-controlled reinforced concrete piles.
2024, 54(7): 181-187.
doi: 10.3724/j.gyjzG22091705
Abstract:
The assumed composition of the ultimate compression and uplift bearing capacity of rock-socketed piles is essentially the same in current Chinese codes. In addition, the same method is adopted to calculate the ultimate shaft resistance and tip resistance of piles for rock-socketed sections by using the ultimate shaft resistance coefficient ξs and tip resistance coefficient ξb to multiply uniaxial compressive strength fucs of rock. However, the values of the aforementioned ξs and ξb in the criteria are quite different. Based on test data of rock-socketed piles under compression loads, influence laws of pile diameters, rock-socketed depths, ratios of rocketed depths to diameters, and uniaxial strength of rock on ultimate shaft resistance and shaft resistance coefficients as well as ultimate tip resistance and ultimate tip resistance coefficients of rock-socketed sections were analyzed. It was indicated that there was no significant correlation between pile diameters and ultimate shaft resistance coefficients as well as ultimate tip resistance coefficients of rock-socketed piles. With increase in rock-socketed depths and ratios of rocketed depths to diameters, the ultimate shaft resistance and ultimate tip resistance of rock-socketed piles generally decreased. There was an optimum rock-socketed depths and a ratio of rocketed depths to diameters, which could make the ultimate shaft resistance and tip resistance of rock-socketed sections played their roles most fully and coordinately. The ultimate shaft resistance and tip resistance increased but the ultimate shaft resistance coefficients and tip resistance coefficients decreased with increase in the uniaxial compressive strength of rock. The strength of rock was a significant factor to determine the coefficients of shaft resistance and tip resistance. There was a good statistical correlation between them, which could be respectively fitted as ξs=0.436 fucs-0.68 and ξb=4.183 fucs-0.79.
The assumed composition of the ultimate compression and uplift bearing capacity of rock-socketed piles is essentially the same in current Chinese codes. In addition, the same method is adopted to calculate the ultimate shaft resistance and tip resistance of piles for rock-socketed sections by using the ultimate shaft resistance coefficient ξs and tip resistance coefficient ξb to multiply uniaxial compressive strength fucs of rock. However, the values of the aforementioned ξs and ξb in the criteria are quite different. Based on test data of rock-socketed piles under compression loads, influence laws of pile diameters, rock-socketed depths, ratios of rocketed depths to diameters, and uniaxial strength of rock on ultimate shaft resistance and shaft resistance coefficients as well as ultimate tip resistance and ultimate tip resistance coefficients of rock-socketed sections were analyzed. It was indicated that there was no significant correlation between pile diameters and ultimate shaft resistance coefficients as well as ultimate tip resistance coefficients of rock-socketed piles. With increase in rock-socketed depths and ratios of rocketed depths to diameters, the ultimate shaft resistance and ultimate tip resistance of rock-socketed piles generally decreased. There was an optimum rock-socketed depths and a ratio of rocketed depths to diameters, which could make the ultimate shaft resistance and tip resistance of rock-socketed sections played their roles most fully and coordinately. The ultimate shaft resistance and tip resistance increased but the ultimate shaft resistance coefficients and tip resistance coefficients decreased with increase in the uniaxial compressive strength of rock. The strength of rock was a significant factor to determine the coefficients of shaft resistance and tip resistance. There was a good statistical correlation between them, which could be respectively fitted as ξs=0.436 fucs-0.68 and ξb=4.183 fucs-0.79.
2024, 54(7): 188-195.
doi: 10.3724/j.gyjzG23092004
Abstract:
To quantitatively predict the process of unloading for bored piles, combining the unified strength theory (UST) with the non-associated flow rule, the elastoplastic analytical solutions of large strain and small strain for borehole contraction of bored piles were derived. And the influence of intermediate principal stress, dilatancy angle and parameters of piles on analytical values in the borehole contraction process were analyzed. The result indicated that the larger the coefficients of intermediate principal stress b and the internal friction angle of soil φ were, the smaller the dilatancy angle ψ of soil was, and the better the stability of borehole walls of bored piles was. The solutions based on the Mohr-Coulomb yield criterion and the small strain theory in a plastic state of borehole wall soil were both conservative. The larger the coefficient of intermediate principal stress b was, the larger the radial stress and the maximum circumferential stress at the same position of cylindrical borehole wall were, and the smaller the radial displacement at the same position was. With the increase in the coefficients of intermediate principal stress b, the maximum circumferential stress gradually approached the borehole wall, simultaneously, the increment of the maximum circumferential stress decreased with the increase in the coefficient of intermediate principal stress b. Both solutions for soil stress and displacement fields around the cylindrical borehole in the process of borehole contraction due to unloading by large and small strain theories all meet the requirements. The findings could be applied to the quantitative analysis for the stability of borehole wall soil during boring and the bearing characteristics of bored piles.
To quantitatively predict the process of unloading for bored piles, combining the unified strength theory (UST) with the non-associated flow rule, the elastoplastic analytical solutions of large strain and small strain for borehole contraction of bored piles were derived. And the influence of intermediate principal stress, dilatancy angle and parameters of piles on analytical values in the borehole contraction process were analyzed. The result indicated that the larger the coefficients of intermediate principal stress b and the internal friction angle of soil φ were, the smaller the dilatancy angle ψ of soil was, and the better the stability of borehole walls of bored piles was. The solutions based on the Mohr-Coulomb yield criterion and the small strain theory in a plastic state of borehole wall soil were both conservative. The larger the coefficient of intermediate principal stress b was, the larger the radial stress and the maximum circumferential stress at the same position of cylindrical borehole wall were, and the smaller the radial displacement at the same position was. With the increase in the coefficients of intermediate principal stress b, the maximum circumferential stress gradually approached the borehole wall, simultaneously, the increment of the maximum circumferential stress decreased with the increase in the coefficient of intermediate principal stress b. Both solutions for soil stress and displacement fields around the cylindrical borehole in the process of borehole contraction due to unloading by large and small strain theories all meet the requirements. The findings could be applied to the quantitative analysis for the stability of borehole wall soil during boring and the bearing characteristics of bored piles.
2024, 54(7): 196-201.
doi: 10.3724/j.gyjzG22100101
Abstract:
An UDEC analysis model composed of triangular blocks for crack propagation was proposed. In the proposed model,a FEM mesh of triangular elements was generated in the interesting area by a finite element software first. Then the FEM mesh was converted into an UDEC mesh by a transformation program. The UDEC mesh was composed of triangular blocks and joints on the boundary of simulated blocks. The joints included virtual joints and real joints. These virtual joint interfaces provided paths along which cracks could generate and propagate. Its failure was controlled by the model of Joint model SS which was provide by UDEC. The proposed analysis model of UDEC was used for simulating the generation,propagation and coalescence of rock cracks. The transformation program of the proposed model was developed. To verify the correctness of the algorithm,three numerical examples of test samples with double parallel pre-existing cracks under uniaxial compression were computed. The simulated results were compared with the ones of existing tests. The simulated laws of crack propagation were in accordance with the phenomena observed in the tests. Those indicated that the proposed UDEC analysis model for cracks propagation was correct and effective.
An UDEC analysis model composed of triangular blocks for crack propagation was proposed. In the proposed model,a FEM mesh of triangular elements was generated in the interesting area by a finite element software first. Then the FEM mesh was converted into an UDEC mesh by a transformation program. The UDEC mesh was composed of triangular blocks and joints on the boundary of simulated blocks. The joints included virtual joints and real joints. These virtual joint interfaces provided paths along which cracks could generate and propagate. Its failure was controlled by the model of Joint model SS which was provide by UDEC. The proposed analysis model of UDEC was used for simulating the generation,propagation and coalescence of rock cracks. The transformation program of the proposed model was developed. To verify the correctness of the algorithm,three numerical examples of test samples with double parallel pre-existing cracks under uniaxial compression were computed. The simulated results were compared with the ones of existing tests. The simulated laws of crack propagation were in accordance with the phenomena observed in the tests. Those indicated that the proposed UDEC analysis model for cracks propagation was correct and effective.
2024, 54(7): 202-209.
doi: 10.3724/j.gyjzG23061309
Abstract:
Taking an interval of a utility tunnel over a ground fissure in Zhengzhou as the research object, numerical simulations were conducted to analyze the force and deformation of the ground and the utility tunnel in different settlements of the hangingwall of the ground crack. The analysis results showed that due to the large stiffness of the utility tunnel, when the settlement of the hangingwall was smaller, the ground over the utility tunnel heaved; with the increase in settlement, the heave of the ground dropped and the ground even settled, and the settlement and flexure of the utility tunnel increased. When the hangingwall settled, the tensile stress occurred in the top plate of the utility tunnel, and the maximum tensile stress generated at the center of the top plate of the utility tunnel. and the maximum value of tensile stress appears in the center of the top plate; simultaneously, the compressive stress generated in the bottom plate of the utility tunnel, and the maximum compressive stress appeared in the center of the bottom plate of the utility tunnel. With the increase in settlement of the hangingwall, both of the tensile and compressive stresses increased. When the hangingwall settled, the deformation in the direction of width of the utility tunnel was between 0.1 to 10 μm, which was tiny deformation. the deformation in the direction of axle of the utility tunnel was larger and the largest was in the direction of height, however, the deformation at each joint had not regularity.
Taking an interval of a utility tunnel over a ground fissure in Zhengzhou as the research object, numerical simulations were conducted to analyze the force and deformation of the ground and the utility tunnel in different settlements of the hangingwall of the ground crack. The analysis results showed that due to the large stiffness of the utility tunnel, when the settlement of the hangingwall was smaller, the ground over the utility tunnel heaved; with the increase in settlement, the heave of the ground dropped and the ground even settled, and the settlement and flexure of the utility tunnel increased. When the hangingwall settled, the tensile stress occurred in the top plate of the utility tunnel, and the maximum tensile stress generated at the center of the top plate of the utility tunnel. and the maximum value of tensile stress appears in the center of the top plate; simultaneously, the compressive stress generated in the bottom plate of the utility tunnel, and the maximum compressive stress appeared in the center of the bottom plate of the utility tunnel. With the increase in settlement of the hangingwall, both of the tensile and compressive stresses increased. When the hangingwall settled, the deformation in the direction of width of the utility tunnel was between 0.1 to 10 μm, which was tiny deformation. the deformation in the direction of axle of the utility tunnel was larger and the largest was in the direction of height, however, the deformation at each joint had not regularity.
2024, 54(7): 210-216.
doi: 10.3724/j.gyjzG23070508
Abstract:
The highly crystalline structure of barite aggregate makes it fragile, resulting in poor mechanical properties of barite radiation-proof concrete, which limits its application in buildings with severe radiation such as high-pressure and high-thermonuclear projects. To study the effect of polypropylene fiber incorporation on the mechanical properties of barite concrete, the effects of polypropylene fiber content (0, 3, 6, 9 kg/m3) on the mechanical properties of barite concrete with different strength grades were analyzed, and the size effect of barite concrete cube compressive strength was quantified. The meso-structure of polypropylene fiber barite concrete was studied via SEM test. The results showed that the surface of PR40 fiber was wrapped by a dense hardened cement matrix, which improved the structural strength of the polypropylene fiber-cement matrix, thus improving the splitting tensile strength and flexural strength of barite concrete. With the increase in fiber content, the 28 d compressive strength of the specimens increased by 4.3%-19.6%, and the 28 d flexural and splitting tensile strength increased by 1.8%-25.0% and 4.9%-27.7%, respectively. When the fiber content increased, the cement content could not meet the fiber wrapping, so the compressive strength of barite concrete increased first and then decreased with the increase of fiber contents. The size effect of the compressive strength of barite concrete cubes was gradually significant with the increase of fiber content. Compared with the specimens without fiber, the size effect coefficient η100 increased by 0.2%-5.9%, and the size effect coefficient η200 increased by 1.8%-5.9%.
The highly crystalline structure of barite aggregate makes it fragile, resulting in poor mechanical properties of barite radiation-proof concrete, which limits its application in buildings with severe radiation such as high-pressure and high-thermonuclear projects. To study the effect of polypropylene fiber incorporation on the mechanical properties of barite concrete, the effects of polypropylene fiber content (0, 3, 6, 9 kg/m3) on the mechanical properties of barite concrete with different strength grades were analyzed, and the size effect of barite concrete cube compressive strength was quantified. The meso-structure of polypropylene fiber barite concrete was studied via SEM test. The results showed that the surface of PR40 fiber was wrapped by a dense hardened cement matrix, which improved the structural strength of the polypropylene fiber-cement matrix, thus improving the splitting tensile strength and flexural strength of barite concrete. With the increase in fiber content, the 28 d compressive strength of the specimens increased by 4.3%-19.6%, and the 28 d flexural and splitting tensile strength increased by 1.8%-25.0% and 4.9%-27.7%, respectively. When the fiber content increased, the cement content could not meet the fiber wrapping, so the compressive strength of barite concrete increased first and then decreased with the increase of fiber contents. The size effect of the compressive strength of barite concrete cubes was gradually significant with the increase of fiber content. Compared with the specimens without fiber, the size effect coefficient η100 increased by 0.2%-5.9%, and the size effect coefficient η200 increased by 1.8%-5.9%.
2024, 54(7): 217-222.
doi: 10.3724/j.gyjzG23083020
Abstract:
The rapid carbonation experiment of 12 groups of marine concrete was carried out under different temperature and relative humidity conditions. The experimental results showed that temperature and relative humidity had a significant impact on carbonation resistance of marine concrete. With the increase of relative humidity, the carbonation depth of marine concrete was characterized by an initial increase and then decreased, showing a parabolic relation. Moreover, when the relative humidity was very low or very high, the carbonation rate of marine concrete was infinitely slow. While the carbonation rate of marine concrete was accelerated with the increase of temperature, the relation between carbonation depth and temperature was an exponential function. In addition, based on experimental and theoretical analysis, the temperature and humidity influence coefficients were introduced to improve the existing mathematical model of carbonation depth, and by using the Levenberg-Marquart algorithm to fit a nonlinear surface to the experimental data, a prediction model of the carbonation depth of marine concrete was constructed. This model could predict the carbonation depth of marine concrete under different temperature and humidity conditions.
The rapid carbonation experiment of 12 groups of marine concrete was carried out under different temperature and relative humidity conditions. The experimental results showed that temperature and relative humidity had a significant impact on carbonation resistance of marine concrete. With the increase of relative humidity, the carbonation depth of marine concrete was characterized by an initial increase and then decreased, showing a parabolic relation. Moreover, when the relative humidity was very low or very high, the carbonation rate of marine concrete was infinitely slow. While the carbonation rate of marine concrete was accelerated with the increase of temperature, the relation between carbonation depth and temperature was an exponential function. In addition, based on experimental and theoretical analysis, the temperature and humidity influence coefficients were introduced to improve the existing mathematical model of carbonation depth, and by using the Levenberg-Marquart algorithm to fit a nonlinear surface to the experimental data, a prediction model of the carbonation depth of marine concrete was constructed. This model could predict the carbonation depth of marine concrete under different temperature and humidity conditions.
2024, 54(7): 223-231.
doi: 10.3724/j.gyjzG23071013
Abstract:
Taking a subway station project in Shenzhen, Guangdong Province as the research object, temperature measurement test was carried out on the mass concrete of three side walls. The characteristics of concrete temperature changes under different ambient temperatures and different weather conditions were analyzed, ABAQUS finite element software was used to simulate the temperature rise process of concrete. The data obtained by the test were fitted by changing the ambient temperature conditions. The results showed that the ambient temperature had a great influence on the peak, heating rate and cooling rate of concrete temperature, and the radiant heat transfer coefficients of concrete surface would be greatly different between sunny and rainy days when performing finite element simulations, the study could provide technical support for pouring and crack control of mass concrete.
Taking a subway station project in Shenzhen, Guangdong Province as the research object, temperature measurement test was carried out on the mass concrete of three side walls. The characteristics of concrete temperature changes under different ambient temperatures and different weather conditions were analyzed, ABAQUS finite element software was used to simulate the temperature rise process of concrete. The data obtained by the test were fitted by changing the ambient temperature conditions. The results showed that the ambient temperature had a great influence on the peak, heating rate and cooling rate of concrete temperature, and the radiant heat transfer coefficients of concrete surface would be greatly different between sunny and rainy days when performing finite element simulations, the study could provide technical support for pouring and crack control of mass concrete.
2024, 54(7): 232-238.
doi: 10.3724/j.gyjzG23030607
Abstract:
Expanded Steel Mesh (ESM) can improve the mechanical properties of High-Performance Cement Composite Mortar (HPCCM). Through the tensile performance tests of ESM wire nets specimens, ESM three-net specimens and ESM-HPCCM dumbbell-shaped specimens, it was found that the ESM attached to HPCCM had an obvious force effect in the long pitch direction, while the force effect in the short pitch direction was less evident. After fitting, the tensile stress-strain constitutive model of ESM mesh was established. Based on the test, the bearing capacity of ESM-HPCCM was calculated and analyzed, and the calculation method of bearing capacity of ESM-HPCCM along the long pitch direction was proposed. The ESM-steel fiber HPCCM was regarded as a whole, and the constitutional model of ESM-HPCCM material was proposed by referring to the RILEM model of steel fiber reinforced concrete.
Expanded Steel Mesh (ESM) can improve the mechanical properties of High-Performance Cement Composite Mortar (HPCCM). Through the tensile performance tests of ESM wire nets specimens, ESM three-net specimens and ESM-HPCCM dumbbell-shaped specimens, it was found that the ESM attached to HPCCM had an obvious force effect in the long pitch direction, while the force effect in the short pitch direction was less evident. After fitting, the tensile stress-strain constitutive model of ESM mesh was established. Based on the test, the bearing capacity of ESM-HPCCM was calculated and analyzed, and the calculation method of bearing capacity of ESM-HPCCM along the long pitch direction was proposed. The ESM-steel fiber HPCCM was regarded as a whole, and the constitutional model of ESM-HPCCM material was proposed by referring to the RILEM model of steel fiber reinforced concrete.
2024, 54(7): 239-247.
doi: 10.3724/j.gyjzG23102708
Abstract:
Taking the Buddhist building—the Teaching Room for Nourishing Vital Spirits in the Garden of the Palace of Tranquil Longevity in the Forbidden City as a research object, combining investigation on current situations with studying of historic archival documents, the historic background, architectural characteristics and culture connotations were fully discussed. The discussion focused on the architectural layout, structural design and indoor space organization. Simultaneously, to reveal the unique symbolic meaning, the comparisons between the Teaching Room and other Buddhist buildings in the Forbidden City were conducted. Furthermore, the distinctive floor plan and roof shape and specificity of decoration with hanging lotus columns of the Teaching Room and the historic and cultural causes behind them were discussed.
Taking the Buddhist building—the Teaching Room for Nourishing Vital Spirits in the Garden of the Palace of Tranquil Longevity in the Forbidden City as a research object, combining investigation on current situations with studying of historic archival documents, the historic background, architectural characteristics and culture connotations were fully discussed. The discussion focused on the architectural layout, structural design and indoor space organization. Simultaneously, to reveal the unique symbolic meaning, the comparisons between the Teaching Room and other Buddhist buildings in the Forbidden City were conducted. Furthermore, the distinctive floor plan and roof shape and specificity of decoration with hanging lotus columns of the Teaching Room and the historic and cultural causes behind them were discussed.
2024, 54(7): 248-252.
doi: 10.3724/j.gyjzG22102107
Abstract:
To mitigate a series of issues accompanied by cement production such as high consumption of natural resources and energy and environmental pollution, calcium carbide residues (CCR) and ground granulated blast-furnace slag (GGBS) were designed to develop alkali-activated cementitious materials made from all solid wastes, which could totally replace cement. A test for waterproof curtains by the jet grouting method with the alkali-activated cementitious material made from all solid wastes was conducted. The workability, water permeability and strength characteristics of alkali-activated cementitious material made from all solid wastes with different proportions were studied. The test results indicated that compared with using cement, when alkali-activated cementitious materials made from all solid wastes were adopted, the nozzle diameter of jet grouting machines should be increased and the water content of undisturbed CCR should be maintained to keep the pipeline unblocked during construction. Excavation inspection after jet grouting found that there was no leakage on the curtain and the curtain met the design requirements, and the permeability coefficient of the waterproof curtain made from alkali-activated cementitious materials was slightly smaller than that made of cement. The strength of waterproof curtains jet grouted with the alkali-activated cementitious material made from calcium carbide residues and ground granulated blast-furnace slag in the mix proportion of 1∶2 was less than jet grouted with cement. However, when the calcium carbide residue and ground granulated blast-furnace slag in the mix proportion of 1∶1, the strength of curtains at early ages was slightly higher than that jet grouted with cement, the strength was significantly higher at later ages.
To mitigate a series of issues accompanied by cement production such as high consumption of natural resources and energy and environmental pollution, calcium carbide residues (CCR) and ground granulated blast-furnace slag (GGBS) were designed to develop alkali-activated cementitious materials made from all solid wastes, which could totally replace cement. A test for waterproof curtains by the jet grouting method with the alkali-activated cementitious material made from all solid wastes was conducted. The workability, water permeability and strength characteristics of alkali-activated cementitious material made from all solid wastes with different proportions were studied. The test results indicated that compared with using cement, when alkali-activated cementitious materials made from all solid wastes were adopted, the nozzle diameter of jet grouting machines should be increased and the water content of undisturbed CCR should be maintained to keep the pipeline unblocked during construction. Excavation inspection after jet grouting found that there was no leakage on the curtain and the curtain met the design requirements, and the permeability coefficient of the waterproof curtain made from alkali-activated cementitious materials was slightly smaller than that made of cement. The strength of waterproof curtains jet grouted with the alkali-activated cementitious material made from calcium carbide residues and ground granulated blast-furnace slag in the mix proportion of 1∶2 was less than jet grouted with cement. However, when the calcium carbide residue and ground granulated blast-furnace slag in the mix proportion of 1∶1, the strength of curtains at early ages was slightly higher than that jet grouted with cement, the strength was significantly higher at later ages.
