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2023 Vol. 53, No. 1
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2023, 53(1): 1-8.
doi: 10.13204/j.gyjzG20042003
Abstract:
Prefabricated box-plate composite walls have good seismic performances. In order that the box-plate composite walls might applied to practices meet the requirements of fire endurance in specifications, the fire-resistant structural measures were designed and the fire-resistant limit analysis model was constructed. The parameters of the fire-resistant structural measures for the walls were analyzed, which included rock wool thickness, keel spacing and number of rows of openings, gypsum board layer and thickness, cladding sheet types, depth-thickness ratio, and axial compression ratio. The results showed that after the thickness of rock wool exceeded 100 mm, increasing its thickness could significantly improve the fire resistance limit of the walls; raising the thickness and layers of the cladding panels covering fire surface could also improve the fire resistance greatly; the axial compression ratio had a notable impact on the fire endurance; the distance between keels and the number of rows of openings had low impact. According to the above analytic results, the fire-resistant limit optimization design method was proposed, which could provide support for fire prevention design of prefabricated box-plate steel structures.
Prefabricated box-plate composite walls have good seismic performances. In order that the box-plate composite walls might applied to practices meet the requirements of fire endurance in specifications, the fire-resistant structural measures were designed and the fire-resistant limit analysis model was constructed. The parameters of the fire-resistant structural measures for the walls were analyzed, which included rock wool thickness, keel spacing and number of rows of openings, gypsum board layer and thickness, cladding sheet types, depth-thickness ratio, and axial compression ratio. The results showed that after the thickness of rock wool exceeded 100 mm, increasing its thickness could significantly improve the fire resistance limit of the walls; raising the thickness and layers of the cladding panels covering fire surface could also improve the fire resistance greatly; the axial compression ratio had a notable impact on the fire endurance; the distance between keels and the number of rows of openings had low impact. According to the above analytic results, the fire-resistant limit optimization design method was proposed, which could provide support for fire prevention design of prefabricated box-plate steel structures.
2023, 53(1): 9-19.
doi: 10.13204/j.gyjzG22041415
Abstract:
The fire dynamics models and the fire transient thermal analysis models of a single-story box-plate structure composed of one module unit and a three-story box-plate structure composed of three module units under seven different fire scenes were established. By comparing and analyzing, the distribution of temperature fields in indoor air and the law of heat transfer of box-plate steel structures were obtained. The results showed that: when the fire source was located in different locations, time-temperature varied greatly in different parts of the structure. Compared with the traditional calculation method of unified heating curve, the calculation method of space partition was more factual. The temperature field of the structures was similar to the air temperature field, which meant the temperature increased with the height at the floor of fire source, and because of the closed room and the upward flow of hot air, the temperature-time curves were gentler at the higher floor, while the temperature was low and distributed evenly at the lower floor which reflected the air temperature fields had distinguishing feature of stratification and regionality.
The fire dynamics models and the fire transient thermal analysis models of a single-story box-plate structure composed of one module unit and a three-story box-plate structure composed of three module units under seven different fire scenes were established. By comparing and analyzing, the distribution of temperature fields in indoor air and the law of heat transfer of box-plate steel structures were obtained. The results showed that: when the fire source was located in different locations, time-temperature varied greatly in different parts of the structure. Compared with the traditional calculation method of unified heating curve, the calculation method of space partition was more factual. The temperature field of the structures was similar to the air temperature field, which meant the temperature increased with the height at the floor of fire source, and because of the closed room and the upward flow of hot air, the temperature-time curves were gentler at the higher floor, while the temperature was low and distributed evenly at the lower floor which reflected the air temperature fields had distinguishing feature of stratification and regionality.
2023, 53(1): 20-29.
doi: 10.13204/j.gyjzG22041413
Abstract:
By calculating the thermo-mechanical coupling analysis model of prefabricated box-plate steel structures, the thermodynamic response was obtained, and the mechanical response analysis of key members and key measuring points was carried out. Combined with the structural characteristics of the prefabricated box-plate steel structure, the failure mode of the structure under fire was proved, and the fire resistance limit of seven fire scenarios was obtained. The results showed that, in single-story structure, the location of fire sources had a great impact on the fire resistance endurance, and when the fire source was in the center, the film stress produced after the middle surface yield of the plate could provide the post buckling strength, which effectively improved the fire resistance time. When the fire source was near the wall, the structure was under uneven and redistributed stress, and the wall bore too much stress, which caused a great reduction of fire resistance time. For a three-story structure, the fire resistance time would be shortened when the fire source was at the bottom, which would achieve earlier when the fire source located in the center position. The fire resistance time of each working condition had reached more than 1 000 s, and there was no obvious mutation at the maximum displacement in each direction. The prefabricated box-plate steel structure showed great stiffness, excellent fire resistance and superior overall performances.
By calculating the thermo-mechanical coupling analysis model of prefabricated box-plate steel structures, the thermodynamic response was obtained, and the mechanical response analysis of key members and key measuring points was carried out. Combined with the structural characteristics of the prefabricated box-plate steel structure, the failure mode of the structure under fire was proved, and the fire resistance limit of seven fire scenarios was obtained. The results showed that, in single-story structure, the location of fire sources had a great impact on the fire resistance endurance, and when the fire source was in the center, the film stress produced after the middle surface yield of the plate could provide the post buckling strength, which effectively improved the fire resistance time. When the fire source was near the wall, the structure was under uneven and redistributed stress, and the wall bore too much stress, which caused a great reduction of fire resistance time. For a three-story structure, the fire resistance time would be shortened when the fire source was at the bottom, which would achieve earlier when the fire source located in the center position. The fire resistance time of each working condition had reached more than 1 000 s, and there was no obvious mutation at the maximum displacement in each direction. The prefabricated box-plate steel structure showed great stiffness, excellent fire resistance and superior overall performances.
2023, 53(1): 30-40.
doi: 10.13204/j.gyjzG20042005
Abstract:
After determining the thermal parameters, the boundary conditions of the fired surface, the backfire surface, and the contact conditions, the temperature field analysis model of the prefabricated box-plate composite wall was constructed by the FEM software ABAQUS. And the validity of the model was verified by relevant test results. On the basis, the temperature fields of the composite wall as well as its key measurement points were obtained, and the parameters of each component were also be analyzed. The results showed that the thickness of rock wool, the type and the thickness of cladding sheet, the numbers of layers had obvious influence on the temperature fields inside the composite wall, and the others factors had little effect. According to the analysis results, the fire-resistant design idea of composite walls and the temperature prediction formula of key temperature control points were proposed.
After determining the thermal parameters, the boundary conditions of the fired surface, the backfire surface, and the contact conditions, the temperature field analysis model of the prefabricated box-plate composite wall was constructed by the FEM software ABAQUS. And the validity of the model was verified by relevant test results. On the basis, the temperature fields of the composite wall as well as its key measurement points were obtained, and the parameters of each component were also be analyzed. The results showed that the thickness of rock wool, the type and the thickness of cladding sheet, the numbers of layers had obvious influence on the temperature fields inside the composite wall, and the others factors had little effect. According to the analysis results, the fire-resistant design idea of composite walls and the temperature prediction formula of key temperature control points were proposed.
2023, 53(1): 41-49,134.
doi: 10.13204/j.gyjzG22041412
Abstract:
The welding simulations of Q235B and Q345B steel plates was conducted by ABAQUS associated DFLUX heat source subroutine, and the welding residual stress test of steel sheets was conducted by ultrasonic detection method. It was found that tensile stress was the main longitudinal residual stress in the heat-affected zone of the weld, and there was tensile stress and compressive stress in the transverse residual stress in the whole welding specimens. The test results were basically consistent with the simulation results, which verified the reliability of simulating welding of steel sheets. Using the same simulation method, the welding process of stiffened steel wallboards was simulated, and the residual stress, welding deformation, and shear capacity were analyzed. The results showed that the welding residual stress and welding deformation of the stiffened steel wallboard mainly occurred at the welding seam between the stiffening rib and the wallboard, and the residual stress along the welding seam direction was small at the upper and lower ends and large in the middle. The influence of discontinuous welding on high residual stress and overall residual deformation of stiffened steel wallboards was obviously lower than that of continuous welding. In all welding conditions, the minimum ultimate shear capacity decreased by 6.8% compared with the maximum ultimate shear capacity. After comparing all working conditions, it was found that the welding condition with a larger discontinuity distance had a better effect.
The welding simulations of Q235B and Q345B steel plates was conducted by ABAQUS associated DFLUX heat source subroutine, and the welding residual stress test of steel sheets was conducted by ultrasonic detection method. It was found that tensile stress was the main longitudinal residual stress in the heat-affected zone of the weld, and there was tensile stress and compressive stress in the transverse residual stress in the whole welding specimens. The test results were basically consistent with the simulation results, which verified the reliability of simulating welding of steel sheets. Using the same simulation method, the welding process of stiffened steel wallboards was simulated, and the residual stress, welding deformation, and shear capacity were analyzed. The results showed that the welding residual stress and welding deformation of the stiffened steel wallboard mainly occurred at the welding seam between the stiffening rib and the wallboard, and the residual stress along the welding seam direction was small at the upper and lower ends and large in the middle. The influence of discontinuous welding on high residual stress and overall residual deformation of stiffened steel wallboards was obviously lower than that of continuous welding. In all welding conditions, the minimum ultimate shear capacity decreased by 6.8% compared with the maximum ultimate shear capacity. After comparing all working conditions, it was found that the welding condition with a larger discontinuity distance had a better effect.
2023, 53(1): 50-56.
doi: 10.13204/j.gyjzG22041411
Abstract:
Prefabricated box-plate steel structure floors are a new type of prefabricated structures welded by steel sheets and stiffeners. Through construction of a number of finite element models of box-plate steel structure floors, the aspect ratio, thickness of steel sheet, stiffener spacing, and the influence of installed tuned mass dampers (TMD) on floors of comfortable levels were studied. The results showed that: the aspect ratio increased from 6∶6 to 10∶6, which could reduce vertical fundamental frequencies by up to 29.6% and reduce the vertical peak acceleration excited by pedestrains. Thicknesses of steel sheets increased from 6 mm to 10 mm, which had a little of effect on vertical fundamental frequencies of floors, but significant influence on the vertical peak acceleration by up to 68.8%; That T-stiffener spacing increased from 1.5 m to 3.0 m could reduce the vertical fundamental frequencies by up to 33.8%, simultaneouly, the vertical peak acceleration increased to 0.1 m/s2. When the thicknesses of steel sheets were smaller and stiffener spacing was larger, it was easy to cause locad vibration for floors and larger peak acceleration locally. The tuned mass dampers (TMD) could effectively improve masses of floors in vibration as well as floor comfortable levels which could meet the specification requirements.
Prefabricated box-plate steel structure floors are a new type of prefabricated structures welded by steel sheets and stiffeners. Through construction of a number of finite element models of box-plate steel structure floors, the aspect ratio, thickness of steel sheet, stiffener spacing, and the influence of installed tuned mass dampers (TMD) on floors of comfortable levels were studied. The results showed that: the aspect ratio increased from 6∶6 to 10∶6, which could reduce vertical fundamental frequencies by up to 29.6% and reduce the vertical peak acceleration excited by pedestrains. Thicknesses of steel sheets increased from 6 mm to 10 mm, which had a little of effect on vertical fundamental frequencies of floors, but significant influence on the vertical peak acceleration by up to 68.8%; That T-stiffener spacing increased from 1.5 m to 3.0 m could reduce the vertical fundamental frequencies by up to 33.8%, simultaneouly, the vertical peak acceleration increased to 0.1 m/s2. When the thicknesses of steel sheets were smaller and stiffener spacing was larger, it was easy to cause locad vibration for floors and larger peak acceleration locally. The tuned mass dampers (TMD) could effectively improve masses of floors in vibration as well as floor comfortable levels which could meet the specification requirements.
2023, 53(1): 57-62.
doi: 10.13204/j.gyjzG21090504
Abstract:
As an important contemporary architectural phenomenon, complexity architecture shows a strong tendency of scientism. Based on reviews of the development process for complexity architecture movement from deconstruction to complexity, the evolution of the theory and practice was clarified. The gradually increasing scientism tendency of complex architecture movement was revealed, which indicated the architecture tendency from axiology to the scientific theory, highlighting complexity objectives, implementing devaluation and desubjectification to conform to the scientific paradigm, and forming a new geometric design strategy highly dependent on mathematics and taking algorithms and virtual reality as the core. The conclusion that the scientism tendency of the complexity architecture movement promoted the expansion of architectural capability was obtained, but there were still many problems caused by departing from the inherent social and humanistic attributes of architecture.
As an important contemporary architectural phenomenon, complexity architecture shows a strong tendency of scientism. Based on reviews of the development process for complexity architecture movement from deconstruction to complexity, the evolution of the theory and practice was clarified. The gradually increasing scientism tendency of complex architecture movement was revealed, which indicated the architecture tendency from axiology to the scientific theory, highlighting complexity objectives, implementing devaluation and desubjectification to conform to the scientific paradigm, and forming a new geometric design strategy highly dependent on mathematics and taking algorithms and virtual reality as the core. The conclusion that the scientism tendency of the complexity architecture movement promoted the expansion of architectural capability was obtained, but there were still many problems caused by departing from the inherent social and humanistic attributes of architecture.
2023, 53(1): 63-71,129.
doi: 10.13204/j.gyjzG20210522
Abstract:
Based on emotional demand orientation, investigation and research related to nursing institutions in the Gusu area of Suzhou was conducted. Taking the case of Xiyuan Nursing Care Home to conduct a speculative discussion, based on the cultural and architectural characteristics of the old city,the needs, behavior characteristics,and so on of the elderly were summarized, the advices of improving space adaptability for the elderly were proposed. Finally,according to the common and existing problems of nursing institutions, such as closed management, single levels of space, insufficient privacy and lack of "social sense of life", and aging of facilities and equiments,ect., the five corresponding improvement advices for elderly-oriented design were presented to provide more reasonable and comfortable spatial arrangement methods and design concepts to nursing space institutions and to meet the demands of the elderly for high quality life.
Based on emotional demand orientation, investigation and research related to nursing institutions in the Gusu area of Suzhou was conducted. Taking the case of Xiyuan Nursing Care Home to conduct a speculative discussion, based on the cultural and architectural characteristics of the old city,the needs, behavior characteristics,and so on of the elderly were summarized, the advices of improving space adaptability for the elderly were proposed. Finally,according to the common and existing problems of nursing institutions, such as closed management, single levels of space, insufficient privacy and lack of "social sense of life", and aging of facilities and equiments,ect., the five corresponding improvement advices for elderly-oriented design were presented to provide more reasonable and comfortable spatial arrangement methods and design concepts to nursing space institutions and to meet the demands of the elderly for high quality life.
2023, 53(1): 72-81.
doi: 10.13204/j.gyjzG21012706
Abstract:
Industrial heritage community is the historical carrier of the exploration of the standardization mode of workers’ residential area in the First Five Year Plan period, and it is an important historical witness of urban development. As an important modern industrial city, Shenyang has many industrial heritage community resources. In recent years, the city has entered the stage of stock development, and the industrial heritage community lands have superior urban renewal conditions, accompanied by land renewal, the phenomenon of above ground heritage damage is widespread. Based on the background of community protection and renewal of industrial heritage, guided by the theory of micro renewal and community co-governance, establishing a renewal technical method of "optimizing community co-governance technique, strengthening community co-governance system and improving community long-term service mechanism", taking Santaizi Worker’s Community in Shenyang as an example, the current conditions of the history, land, space, architecture and etc. were studied, the values of history and construction processes were estimated, fin the key protection areas and construction requirements were put forward. Based on topological data analysis, the protection and renewal strategies were put forward, such as "protecting the features of the historical block, creating a community co-governance system, building public service facilities, reviving the regional neighborhood space, and improving the system and mechanism" to build an organic renewal path for industrial heritage communities to achieve the multiple and compound goals of optimizing the living environment, upgrading the stock, and inheriting regional culture.
Industrial heritage community is the historical carrier of the exploration of the standardization mode of workers’ residential area in the First Five Year Plan period, and it is an important historical witness of urban development. As an important modern industrial city, Shenyang has many industrial heritage community resources. In recent years, the city has entered the stage of stock development, and the industrial heritage community lands have superior urban renewal conditions, accompanied by land renewal, the phenomenon of above ground heritage damage is widespread. Based on the background of community protection and renewal of industrial heritage, guided by the theory of micro renewal and community co-governance, establishing a renewal technical method of "optimizing community co-governance technique, strengthening community co-governance system and improving community long-term service mechanism", taking Santaizi Worker’s Community in Shenyang as an example, the current conditions of the history, land, space, architecture and etc. were studied, the values of history and construction processes were estimated, fin the key protection areas and construction requirements were put forward. Based on topological data analysis, the protection and renewal strategies were put forward, such as "protecting the features of the historical block, creating a community co-governance system, building public service facilities, reviving the regional neighborhood space, and improving the system and mechanism" to build an organic renewal path for industrial heritage communities to achieve the multiple and compound goals of optimizing the living environment, upgrading the stock, and inheriting regional culture.
2023, 53(1): 82-90.
doi: 10.13204/j.gyjzG22031304
Abstract:
Focusing on the dual-carbon strategy proposed again by NPC and CPPCC in 2022 and the requirements for steadily advancing urban renewal, based on the new demands for the spatial renewal design of industrial heritage in the post-epidemic era, combined with domestic and foreign research and development trends in this field, and based on the five goals of "intensive land use, energy conservation and environmental protection, industrial coordination, culture inheriting and economical applicability", the innovative industrual heritage renewal design principle of "Double Improving and Double Declining" was proposed. Taking Changchun Tractor Plant as an example, the different space renewal design methods and effects of the foundry (Building 3) and the processing workshop (Building 2) were compared and explored.
Focusing on the dual-carbon strategy proposed again by NPC and CPPCC in 2022 and the requirements for steadily advancing urban renewal, based on the new demands for the spatial renewal design of industrial heritage in the post-epidemic era, combined with domestic and foreign research and development trends in this field, and based on the five goals of "intensive land use, energy conservation and environmental protection, industrial coordination, culture inheriting and economical applicability", the innovative industrual heritage renewal design principle of "Double Improving and Double Declining" was proposed. Taking Changchun Tractor Plant as an example, the different space renewal design methods and effects of the foundry (Building 3) and the processing workshop (Building 2) were compared and explored.
2023, 53(1): 91-99.
doi: 10.13204/j.gyjzG22040221
Abstract:
Taking Harbin, a representative severe-cold-region city, as the research object, starting from clarifying the research scope of urban block morphology and building energy consumption, and based on the identification of block morphology scale affecting building energy consumption in severe cold regions, this paper identified the block morphology indexes affecting building energy consumption and analyzed the influence degree and mechanism of each index on building energy consumption with statistical analysis methods. The results showed that the scale of block morphology with the geometric center of the building plane as the center and a 100 m radius as the radius had the most significant impact on building energy consumption; building site cover ratio, floor area ratio, average building height, road height-width ratio, green space ratio and total surface area of surrounding buildings had different degrees of influence on building energy consumption. Furthermore, the application of the research conclusions in building energy-saving oriented block morphology design and building energy-saving suitability evaluation of block morphology was discussed.
Taking Harbin, a representative severe-cold-region city, as the research object, starting from clarifying the research scope of urban block morphology and building energy consumption, and based on the identification of block morphology scale affecting building energy consumption in severe cold regions, this paper identified the block morphology indexes affecting building energy consumption and analyzed the influence degree and mechanism of each index on building energy consumption with statistical analysis methods. The results showed that the scale of block morphology with the geometric center of the building plane as the center and a 100 m radius as the radius had the most significant impact on building energy consumption; building site cover ratio, floor area ratio, average building height, road height-width ratio, green space ratio and total surface area of surrounding buildings had different degrees of influence on building energy consumption. Furthermore, the application of the research conclusions in building energy-saving oriented block morphology design and building energy-saving suitability evaluation of block morphology was discussed.
2023, 53(1): 100-107,120.
doi: 10.13204/j.gyjzG22011201
Abstract:
Considering the complexity and the lack of systematic research for existing dry-connection beam-column joints, a prefabricated beam-column joint with butterfly-shaped energy consumpution connectors was proposed. Firstly, based on the structural form of the proposed joint, relying on the existing test data of cast-in-place reinforced concrete beam-column joints and steel structure joints connected by bolts, the corresponding numerical models were constructed by ABAQUS. The numerical calculation method and model parameters were verified by comparative analysis. On the basis, the model of the prefabricated beam-column joints with butterfly-shaped energy consumpution connectors was constructed, and quasi-static loading was applied to the joint. The seismic performance and main influencing factors of the new joint were studied by comparing with cast-in-place joints. Finally, the joint was optimized. The overall frame structure model with the joints was constructed, and its seismic performance was evaluated. The results indicated that the overall shape of hysteresis curves for the prefabricated beam-column joint with butterfly-shaped energy consumpution connectors was full and the energy dissipation performance was good. The mechanical properties of the prefabricated beam-column joint with butterfly-shaped energy consuming connectors would vary significantly due to high-strength bolt pretension and friction coefficients of splice steel plates. The seismic displacement response of the overall structure model constructed by the optimized joint was slightly larger than that of the cast-in-place frame structure system, but the overall seismic performance could meet the requirements of earthquake fortification.
Considering the complexity and the lack of systematic research for existing dry-connection beam-column joints, a prefabricated beam-column joint with butterfly-shaped energy consumpution connectors was proposed. Firstly, based on the structural form of the proposed joint, relying on the existing test data of cast-in-place reinforced concrete beam-column joints and steel structure joints connected by bolts, the corresponding numerical models were constructed by ABAQUS. The numerical calculation method and model parameters were verified by comparative analysis. On the basis, the model of the prefabricated beam-column joints with butterfly-shaped energy consumpution connectors was constructed, and quasi-static loading was applied to the joint. The seismic performance and main influencing factors of the new joint were studied by comparing with cast-in-place joints. Finally, the joint was optimized. The overall frame structure model with the joints was constructed, and its seismic performance was evaluated. The results indicated that the overall shape of hysteresis curves for the prefabricated beam-column joint with butterfly-shaped energy consumpution connectors was full and the energy dissipation performance was good. The mechanical properties of the prefabricated beam-column joint with butterfly-shaped energy consuming connectors would vary significantly due to high-strength bolt pretension and friction coefficients of splice steel plates. The seismic displacement response of the overall structure model constructed by the optimized joint was slightly larger than that of the cast-in-place frame structure system, but the overall seismic performance could meet the requirements of earthquake fortification.
2023, 53(1): 108-120.
doi: 10.13204/j.gyjzG22022114
Abstract:
In order to study seismic performance of prefabricated concrete shear walls with prefabricated concrete infill walls, a model of 1∶3 scale with two-story prefabricated concrete shear walls and prefabricated concrete infill walls was designed and fabricated. Considering the models with prefabricated concrete infill walls along the two principal axis directions of the structural plane respectively, three sets of seismic waves and eight seismic acceleration peak levels, the dynamic characteristics, damage modes, acceleration responses, displacement responses and strain responses of models excited by different levels of seismic waves were obtained by shaking table tests. The results showed that: 1) excited by fortification earthquakes and rare earthquakes of 8 degrees, the model was severely damaged, and the final failure mode of the model was that concrete at the bottom of the first-floor shear wall peeled off and formed many horizontal through cracks. 2) The model was basically in the elastic state excited by 6-degree earthquakes and fortification earthquakes of 7 degrees. The existence of the prefabricated concrete infill walls increased the lateral stiffness of shear walls and reduced seismic acceleration responses of shear walls. Subjected to the frequent earthquakes of 8 degrees and the rare earquakes of 7 degrees, the elastic-plastic deformation occurred in models gradually, and the effect of prefabricated concrete infill wall gradually decayed. 3) under rare earthquakes below 8 degrees, prefabricated concrete infill walls were of a significant effect increasing lateral stiffness of shear walls; under rare earthquakes of 8 degrees,the model damaged severely, and prefabricated concrete infill walls did not play a basic role.
In order to study seismic performance of prefabricated concrete shear walls with prefabricated concrete infill walls, a model of 1∶3 scale with two-story prefabricated concrete shear walls and prefabricated concrete infill walls was designed and fabricated. Considering the models with prefabricated concrete infill walls along the two principal axis directions of the structural plane respectively, three sets of seismic waves and eight seismic acceleration peak levels, the dynamic characteristics, damage modes, acceleration responses, displacement responses and strain responses of models excited by different levels of seismic waves were obtained by shaking table tests. The results showed that: 1) excited by fortification earthquakes and rare earthquakes of 8 degrees, the model was severely damaged, and the final failure mode of the model was that concrete at the bottom of the first-floor shear wall peeled off and formed many horizontal through cracks. 2) The model was basically in the elastic state excited by 6-degree earthquakes and fortification earthquakes of 7 degrees. The existence of the prefabricated concrete infill walls increased the lateral stiffness of shear walls and reduced seismic acceleration responses of shear walls. Subjected to the frequent earthquakes of 8 degrees and the rare earquakes of 7 degrees, the elastic-plastic deformation occurred in models gradually, and the effect of prefabricated concrete infill wall gradually decayed. 3) under rare earthquakes below 8 degrees, prefabricated concrete infill walls were of a significant effect increasing lateral stiffness of shear walls; under rare earthquakes of 8 degrees,the model damaged severely, and prefabricated concrete infill walls did not play a basic role.
2023, 53(1): 121-129.
doi: 10.13204/j.gyjzG22011107
Abstract:
In order to study the seismic performance of a museum adopting a measure of seismic isolation and shock absorption, a 1/30 scale model of the structure with rubber isolation bearings beneathe column bottoms of ground floors and buckling-restrainted braces in the upper structure was conducted on a shaking table for earthquake simulation tests. Experimental research showed that subjected to various levels of earthquakes, the combined seismic isolation and shock absorption structure was only slightly damaged, the first of translation natural vibration frequency in the Y-direction was reduced by 9.1% subjected to the fortification earthquake, and the first torsional frequency reduced by 6.1% subjected to the rare earthquake. The acceleration amplification factor was 0.45 in the isolation storey, and the upper structure was also less than 1.0. The energy consumption performance of isolation bearings became better and better with the increase of earthquake intensities. From the energy consumption of only about 4 kN·mm under frequent earthquakes to the maximum energy consumption of about 426 kN·mm under rare earthquake, the combined measure for the structure achieved the expected shock absorption goal well.
In order to study the seismic performance of a museum adopting a measure of seismic isolation and shock absorption, a 1/30 scale model of the structure with rubber isolation bearings beneathe column bottoms of ground floors and buckling-restrainted braces in the upper structure was conducted on a shaking table for earthquake simulation tests. Experimental research showed that subjected to various levels of earthquakes, the combined seismic isolation and shock absorption structure was only slightly damaged, the first of translation natural vibration frequency in the Y-direction was reduced by 9.1% subjected to the fortification earthquake, and the first torsional frequency reduced by 6.1% subjected to the rare earthquake. The acceleration amplification factor was 0.45 in the isolation storey, and the upper structure was also less than 1.0. The energy consumption performance of isolation bearings became better and better with the increase of earthquake intensities. From the energy consumption of only about 4 kN·mm under frequent earthquakes to the maximum energy consumption of about 426 kN·mm under rare earthquake, the combined measure for the structure achieved the expected shock absorption goal well.
2023, 53(1): 130-134.
doi: 10.13204/j.gyjzG22012002
Abstract:
Numerical simulation analysis was conducted for a tensioning schemes of super-long prestressed frame structure, simultaneously, the internal force distribution and deformation law of the structure in integral pouring with synchronous tensioning and segmental pouring with segmental tensioning were analyzed and compared; four tensioning schemes were proposed and calculated respectively. The analysis results showed that compared with the overall tensioning scheme, the scheme of batched pouring and segmental tensioning could improve the internal force distribution of side columns, the maximum bending moment of side columns was significantly reduced, and the tensile stress distribution of concrete at the column ends was also improved. Additionally, it was beneficial to the overall performance of the structure by closing the post-cast strips and tensioning the prestressed reinforcement of the span where the post-cast strips were located for many times, and the beneficial effect was more obvious with the increase of batches. In the actual projects, the scheme of batched tensioning for the reserved post cast-strips should be adopted if conditions permitted.
Numerical simulation analysis was conducted for a tensioning schemes of super-long prestressed frame structure, simultaneously, the internal force distribution and deformation law of the structure in integral pouring with synchronous tensioning and segmental pouring with segmental tensioning were analyzed and compared; four tensioning schemes were proposed and calculated respectively. The analysis results showed that compared with the overall tensioning scheme, the scheme of batched pouring and segmental tensioning could improve the internal force distribution of side columns, the maximum bending moment of side columns was significantly reduced, and the tensile stress distribution of concrete at the column ends was also improved. Additionally, it was beneficial to the overall performance of the structure by closing the post-cast strips and tensioning the prestressed reinforcement of the span where the post-cast strips were located for many times, and the beneficial effect was more obvious with the increase of batches. In the actual projects, the scheme of batched tensioning for the reserved post cast-strips should be adopted if conditions permitted.
2023, 53(1): 135-143,200.
doi: 10.13204/j.gyjzG22032903
Abstract:
To improve seismic performances of cold-formed steel framed shear walls, a self-centering energy-dissipation brace was proposed, and its configuration and working principle were presented. A finite element analysis model was constructed to study the mechanical properties,a simplified simulation method of self-centering energy-dissipation braces was proposed. The hysteresis curves of cold-formed steel shear walls with or without braces were compared,the variable parameter analysis of self-centering energy dissipation braces was conducted to analyze the effects of preloading, disc spring stiffness and friction on the seismic performance of the wall. The research results showed that adding self-centering energy-dissipation braces could improve the bearing capacity of the wall, enhance the energy dissipation capacity and ductility of the wall, reduce the residual deformation of the structure and improve the seismic performances of the wall;the residual deformation of the wall decreased with increasing disc spring stiffness, and preloading and increased with increasing friction.
To improve seismic performances of cold-formed steel framed shear walls, a self-centering energy-dissipation brace was proposed, and its configuration and working principle were presented. A finite element analysis model was constructed to study the mechanical properties,a simplified simulation method of self-centering energy-dissipation braces was proposed. The hysteresis curves of cold-formed steel shear walls with or without braces were compared,the variable parameter analysis of self-centering energy dissipation braces was conducted to analyze the effects of preloading, disc spring stiffness and friction on the seismic performance of the wall. The research results showed that adding self-centering energy-dissipation braces could improve the bearing capacity of the wall, enhance the energy dissipation capacity and ductility of the wall, reduce the residual deformation of the structure and improve the seismic performances of the wall;the residual deformation of the wall decreased with increasing disc spring stiffness, and preloading and increased with increasing friction.
2023, 53(1): 144-150,8.
doi: 10.13204/j.gyjzG22051025
Abstract:
To investigate the hysteretic properties of the partially encased steel-concrete composite beams (PEC beams), combined with test data of previous studies,two PEC beams with different section heights under cyclic bending-shear loading were conducted. The results showed that under cyclic bending-shear loading, the failure mode of the PEC beams was tensile fracture at the steel flange of beam ends after elastic-plastic buckling, and the tensile fracture of the steel web accompanied by compressive collapse of concrete. The test values of the flexural capacity of PEC beams were about 10% to 30% larger than the corresponding values calculated by the full-section plastic method recommended by code T/CECS 719-2020, and the actual shear capacity of PEC beams was significantly higher than the theoretical calculation value. Concrete and links had good buckling-restrainted effect on flanges and webs of the main steel members. When the width-thickness ratios of the flanges and the spacing between the links obviously exceeded the limit range specified in code T/CECS 719-2020, the main steel member still achieved full-section plasticity, and the high strength advantage of steel was fully utilized. As for the two PEC beams, the hysteresis curves were full, the ductility coefficients were 4 and 6.8 (larger value for the beam with the higher section), and the average energy dissipation coefficients of the two specimens after yielding were about 2.2, indicating that the seismic performances of PEC beams were good.
To investigate the hysteretic properties of the partially encased steel-concrete composite beams (PEC beams), combined with test data of previous studies,two PEC beams with different section heights under cyclic bending-shear loading were conducted. The results showed that under cyclic bending-shear loading, the failure mode of the PEC beams was tensile fracture at the steel flange of beam ends after elastic-plastic buckling, and the tensile fracture of the steel web accompanied by compressive collapse of concrete. The test values of the flexural capacity of PEC beams were about 10% to 30% larger than the corresponding values calculated by the full-section plastic method recommended by code T/CECS 719-2020, and the actual shear capacity of PEC beams was significantly higher than the theoretical calculation value. Concrete and links had good buckling-restrainted effect on flanges and webs of the main steel members. When the width-thickness ratios of the flanges and the spacing between the links obviously exceeded the limit range specified in code T/CECS 719-2020, the main steel member still achieved full-section plasticity, and the high strength advantage of steel was fully utilized. As for the two PEC beams, the hysteresis curves were full, the ductility coefficients were 4 and 6.8 (larger value for the beam with the higher section), and the average energy dissipation coefficients of the two specimens after yielding were about 2.2, indicating that the seismic performances of PEC beams were good.
2023, 53(1): 151-159,19.
doi: 10.13204/j.gyjzG21120112
Abstract:
12 steel-tube-confined concrete-filled steel tube columns(TCFST), 6 tubed reinforced concrete columns (TRC) and 9 tubed steel reinforced concrete columns(TSRC) were designed to study the effect of long-term loading on the deformation and bearing capacity. Among them,8 TCFST, 6 TSRC and 4 TRC short columns were loaded for a total of 760 days. Then the axial compression tests were conducted on all the above columns. The main concerned parameters were concrete strength grade (C50 and C70), and core concrete ages at the time of loading application (7 d, 14 d and 28 d). The long-term deformation properties of the columns and the influence of 760-day sustained loading on their mechanical properties were compared and analyzed. The results showed that: 1) the long-term deformation of the three types of short columns occurred mainly in the early stage of the loading, showing a rapid increase in the early stage and a gradual slowdown in the later stage. The long-term deformation of the TCFST columns was the smallest comparing with the other two; 2) the low-stress long-term loading, long-term deformation of core concrete, as well as interlayer concrete had almost no effect on the bearing capacity of the columns under axial compression; the type of specimens, loading age and concrete strength grade had little effect on the bearing capacity; 3) the column failure modes were not influenced by the existence of long-term loading. TSRC columns and TRC columns showed an obvious shear failure, while the TCFST columns with loading in early age or moderate concrete strength grade occurred ductile squash failure.
12 steel-tube-confined concrete-filled steel tube columns(TCFST), 6 tubed reinforced concrete columns (TRC) and 9 tubed steel reinforced concrete columns(TSRC) were designed to study the effect of long-term loading on the deformation and bearing capacity. Among them,8 TCFST, 6 TSRC and 4 TRC short columns were loaded for a total of 760 days. Then the axial compression tests were conducted on all the above columns. The main concerned parameters were concrete strength grade (C50 and C70), and core concrete ages at the time of loading application (7 d, 14 d and 28 d). The long-term deformation properties of the columns and the influence of 760-day sustained loading on their mechanical properties were compared and analyzed. The results showed that: 1) the long-term deformation of the three types of short columns occurred mainly in the early stage of the loading, showing a rapid increase in the early stage and a gradual slowdown in the later stage. The long-term deformation of the TCFST columns was the smallest comparing with the other two; 2) the low-stress long-term loading, long-term deformation of core concrete, as well as interlayer concrete had almost no effect on the bearing capacity of the columns under axial compression; the type of specimens, loading age and concrete strength grade had little effect on the bearing capacity; 3) the column failure modes were not influenced by the existence of long-term loading. TSRC columns and TRC columns showed an obvious shear failure, while the TCFST columns with loading in early age or moderate concrete strength grade occurred ductile squash failure.
2023, 53(1): 160-168,188.
doi: 10.13204/j.gyjzG22012912
Abstract:
Accroding to the seismic performance experiments of 10 self-stressing steel-slag-concrete-filled steel tube columns and 4 steel-slag-concrete-filled steel tube columns, the moment-curvature relations of specimens under quasi-static loading were studied, and the influence of different parameters were analyzed, including diameter-thickness ratios, axial compression ratios, ratios of shear spans to effective depths and expansivity of steel slag concrete. The results indicated that all specimens failed under bending, the moment-curvature skeleton curves of specimens were divided into rising stage and stable stage. As the axial compression ratio and expansivity of steel slag concrete increased, the slope of moment-curvature skeleton curves and the flexural capacity of specimens increased in both rising and stable stages. The decrease of diameter-thickness ratios led to the increase of the slope of curves and the flexural capacity of specimens in the rising stage, while the effect of diameter-thickness ratios was not obvious in the stable stage. The slope of skeleton curve increased with the increase of ratios of shear spans to effective depths in each stage, while the flexural capacity did not change obviously. Based on the experimental results, the constitutive relation models of steel tube and self-stressing steel slag concrete were selected, the whole process analysis was compiled by MATLAB, and the influence laws of each parameter on bending moment-curvature skeleton curves were analyzed by the program.
Accroding to the seismic performance experiments of 10 self-stressing steel-slag-concrete-filled steel tube columns and 4 steel-slag-concrete-filled steel tube columns, the moment-curvature relations of specimens under quasi-static loading were studied, and the influence of different parameters were analyzed, including diameter-thickness ratios, axial compression ratios, ratios of shear spans to effective depths and expansivity of steel slag concrete. The results indicated that all specimens failed under bending, the moment-curvature skeleton curves of specimens were divided into rising stage and stable stage. As the axial compression ratio and expansivity of steel slag concrete increased, the slope of moment-curvature skeleton curves and the flexural capacity of specimens increased in both rising and stable stages. The decrease of diameter-thickness ratios led to the increase of the slope of curves and the flexural capacity of specimens in the rising stage, while the effect of diameter-thickness ratios was not obvious in the stable stage. The slope of skeleton curve increased with the increase of ratios of shear spans to effective depths in each stage, while the flexural capacity did not change obviously. Based on the experimental results, the constitutive relation models of steel tube and self-stressing steel slag concrete were selected, the whole process analysis was compiled by MATLAB, and the influence laws of each parameter on bending moment-curvature skeleton curves were analyzed by the program.
2023, 53(1): 169-174,239.
doi: 10.13204/j.gyjzG22052717
Abstract:
The joints of concrete-filled steel tube columns with steel beams have been widely used in engineering, which meet the development requirements of prefabricated structures. However, it has been found that welding seams between steel beams and column walls were easy to fracture in earthquakes resulting in structural damage. Therefore, combined outer rib ring plates with the through-diaphragm connections, a new kind of bolt-welding hybrid joints for connecting concrete-filled square steel tube columns and steel beams, with upper ring plates and lower through-diaphragms was proposed. The failure modes, hysteretic performances, ductility and energy dissipation capacity of the five joint specimens with different connection types, column forms and vertical rib sizes were analyzed through quasi-static loading tests. The results showed that the proposed new joints had good seismic performances and could meet the design criteria requirement of "strong columns and weak beams". The equivalent viscous damping coefficient of the joints was more than 30% higher than that of full-bolted joints. Compared with the ring plate joints, the upper ring plate and lower through-diaphragm joints had better ductility, and the concrete-filled steel tube columns could effectively improve the bearing capacity and stiffness of the joints. Changing the thickness of the vertical rib plate and using full-bolted connections had a significant influence on the failure mode of the joints.
The joints of concrete-filled steel tube columns with steel beams have been widely used in engineering, which meet the development requirements of prefabricated structures. However, it has been found that welding seams between steel beams and column walls were easy to fracture in earthquakes resulting in structural damage. Therefore, combined outer rib ring plates with the through-diaphragm connections, a new kind of bolt-welding hybrid joints for connecting concrete-filled square steel tube columns and steel beams, with upper ring plates and lower through-diaphragms was proposed. The failure modes, hysteretic performances, ductility and energy dissipation capacity of the five joint specimens with different connection types, column forms and vertical rib sizes were analyzed through quasi-static loading tests. The results showed that the proposed new joints had good seismic performances and could meet the design criteria requirement of "strong columns and weak beams". The equivalent viscous damping coefficient of the joints was more than 30% higher than that of full-bolted joints. Compared with the ring plate joints, the upper ring plate and lower through-diaphragm joints had better ductility, and the concrete-filled steel tube columns could effectively improve the bearing capacity and stiffness of the joints. Changing the thickness of the vertical rib plate and using full-bolted connections had a significant influence on the failure mode of the joints.
2023, 53(1): 175-181,90.
doi: 10.13204/j.gyjzG20122911
Abstract:
The joints between steel-reinforced concrete (SRC) columns and steel beams considering the effect of floor slabs in a shear failure mode were studied. A total of 6 joints with different axial compression ratios and floor thicknesses were designed to analyze the structure in quasi-static tests. By comparing and analyzing the laws of the experimental skeleton curves of joints between SRC columns and steel beams with and without floor slabs in a shear failure mode, a trilinear model was selected to establish the dimensionless skeleton curve for joints between SRC columns and steel beams in a shear failure mode considering floor slab effects, and the equation expression was obtained by linear fitting through the ORIGIN software. Then the stiffness degradation laws of the six joints at different stages during the loading process were analyzed, and a model of its resilience was constructed. The stiffness of the same stage in the test was non-linear regression by ORIGIN, and the stiffness degradation curve equations of each stage were obtained, and the calculation was conducted according to the resilience model of joints between SRC columns and steel beams considering the effect of floor slabs in the proposed shear failure mode, the test results and the simulation results were in good agreement, indicating that the restoring model was effective
The joints between steel-reinforced concrete (SRC) columns and steel beams considering the effect of floor slabs in a shear failure mode were studied. A total of 6 joints with different axial compression ratios and floor thicknesses were designed to analyze the structure in quasi-static tests. By comparing and analyzing the laws of the experimental skeleton curves of joints between SRC columns and steel beams with and without floor slabs in a shear failure mode, a trilinear model was selected to establish the dimensionless skeleton curve for joints between SRC columns and steel beams in a shear failure mode considering floor slab effects, and the equation expression was obtained by linear fitting through the ORIGIN software. Then the stiffness degradation laws of the six joints at different stages during the loading process were analyzed, and a model of its resilience was constructed. The stiffness of the same stage in the test was non-linear regression by ORIGIN, and the stiffness degradation curve equations of each stage were obtained, and the calculation was conducted according to the resilience model of joints between SRC columns and steel beams considering the effect of floor slabs in the proposed shear failure mode, the test results and the simulation results were in good agreement, indicating that the restoring model was effective
2023, 53(1): 182-188.
doi: 10.13204/j.gyjzG21092318
Abstract:
To study evolution processes of the soil arching effect and the stress transfer law of soil arching, according to equilibrium conditions of piles and soil and the shear strength criterion, a stress transfer model of soil arching was constructed. The numerical model was built based on the engineering background, and the pattern differences of soil arching in the three stress contours were compared by controlling the equal stress difference method, besides, in conformity to the stress transfer model of soil arching, the transfer law of loads behind piles was analyzed. The analytical solution showed that the normal stress of vertical soil arching between piles and horizontal soil arching behind piles decayed in the law of the exponential function. According to the evolution process of soil arching effect with depth, it could be divided into four zones to be analyzed. The horizontal soil arching effect decayed with depth, and the stress in the soil arching and pile tip increased with depth and was gradually an approximation to the stress behind piles. The load transfer coefficients of soil arching behind piles decreased with depth, and the load transfer coefficients of soil arching between piles increased with depth.
To study evolution processes of the soil arching effect and the stress transfer law of soil arching, according to equilibrium conditions of piles and soil and the shear strength criterion, a stress transfer model of soil arching was constructed. The numerical model was built based on the engineering background, and the pattern differences of soil arching in the three stress contours were compared by controlling the equal stress difference method, besides, in conformity to the stress transfer model of soil arching, the transfer law of loads behind piles was analyzed. The analytical solution showed that the normal stress of vertical soil arching between piles and horizontal soil arching behind piles decayed in the law of the exponential function. According to the evolution process of soil arching effect with depth, it could be divided into four zones to be analyzed. The horizontal soil arching effect decayed with depth, and the stress in the soil arching and pile tip increased with depth and was gradually an approximation to the stress behind piles. The load transfer coefficients of soil arching behind piles decreased with depth, and the load transfer coefficients of soil arching between piles increased with depth.
2023, 53(1): 189-193.
doi: 10.13204/j.gyjzG21112907
Abstract:
To study the fracture toughness of rocks at low temperature is of great significances for evaluating the stability of underground chamber storage structures for liquefied natural gas (LNG). The effects of real-time low temperatures (-60, -40, -20, 0 and 25 ℃) on the fracture toughness of granite mode I in dry and saturated state were researched by the semi-circular bending (SCB) method, and the microcracks of specimens were analyzed by scanning electron microscopy (SEM). The results showed that the fracture toughness of both dry and saturated granite increased with decrease of temperatures. Below 0 ℃, the fracture toughness of the saturated state was significantly greater than that in the dry state. The initial compaction stage of dry specimens decreased with decrease of temperatures, while the peak displacement was almost unchanged. Both the initial compaction stage and the peak displacements of saturated specimens increased with decrease of temperatures. At -60 ℃, the microcracks inside the granite increased significantly resulting in a slower growth of fracture toughness.
To study the fracture toughness of rocks at low temperature is of great significances for evaluating the stability of underground chamber storage structures for liquefied natural gas (LNG). The effects of real-time low temperatures (-60, -40, -20, 0 and 25 ℃) on the fracture toughness of granite mode I in dry and saturated state were researched by the semi-circular bending (SCB) method, and the microcracks of specimens were analyzed by scanning electron microscopy (SEM). The results showed that the fracture toughness of both dry and saturated granite increased with decrease of temperatures. Below 0 ℃, the fracture toughness of the saturated state was significantly greater than that in the dry state. The initial compaction stage of dry specimens decreased with decrease of temperatures, while the peak displacement was almost unchanged. Both the initial compaction stage and the peak displacements of saturated specimens increased with decrease of temperatures. At -60 ℃, the microcracks inside the granite increased significantly resulting in a slower growth of fracture toughness.
2023, 53(1): 194-200.
doi: 10.13204/j.gyjzG22060607
Abstract:
In order to study effect factors and characteristics of shear properties for interfaces between basalt and concrete, a test device for testing properties was designed. Using basalt and C20 and C30 concrete from the same site, 30 indoor specimens for shear tests of rock-concrete interface were conducted. According to the load-displacement curve obtained by the test, the ultimate shear bearing capacity was determined, and the mean value of the interface shear strength was calculated. After normalizing the test results, the effects of interface scales, strength grades and curing ages of concrete, and rock integrity on shear properties of interfaces were studied. The test results showed that the device could effectively simulate and measure the shear properties of interfaces between rock and concrete; the shear capacity of specimens was strongly positive correlative with contact areas, but was not obvious correlative with height or diameter of shear planes. The statistical coefficient of variation for measured strength values increased with the decrease in height of the rock specimens; after the curing age for 7 days,the design strength grade of concrete had an inapparent effect on the interface shear strength under 90% confidence probability; when the curing age of concrete was more than 7 days, the increase in curing age had a positive effect on the interface strength,the longer the curing age of concrete was, the smaller the displacement at the shear strength was. The more intact the rock was, the higher the shear strength of interfaces between rock and concrete was.
In order to study effect factors and characteristics of shear properties for interfaces between basalt and concrete, a test device for testing properties was designed. Using basalt and C20 and C30 concrete from the same site, 30 indoor specimens for shear tests of rock-concrete interface were conducted. According to the load-displacement curve obtained by the test, the ultimate shear bearing capacity was determined, and the mean value of the interface shear strength was calculated. After normalizing the test results, the effects of interface scales, strength grades and curing ages of concrete, and rock integrity on shear properties of interfaces were studied. The test results showed that the device could effectively simulate and measure the shear properties of interfaces between rock and concrete; the shear capacity of specimens was strongly positive correlative with contact areas, but was not obvious correlative with height or diameter of shear planes. The statistical coefficient of variation for measured strength values increased with the decrease in height of the rock specimens; after the curing age for 7 days,the design strength grade of concrete had an inapparent effect on the interface shear strength under 90% confidence probability; when the curing age of concrete was more than 7 days, the increase in curing age had a positive effect on the interface strength,the longer the curing age of concrete was, the smaller the displacement at the shear strength was. The more intact the rock was, the higher the shear strength of interfaces between rock and concrete was.
2023, 53(1): 201-206.
doi: 10.13204/j.gyjzG21100401
Abstract:
A new type of prefabricated concrete-filled steel box composite caisson structure was proposed. In order to study mechanical properties of the caisson structure under the water and soil pressure, a full-scale test structure was designed based on the Dayang Parking underground garage project. A static loading test for the structure was conducted to analyze deformation and stress characteristics of the caisson structure under horizontal loads when it was sunk to the design elevation and the baseplate was not sealed, and then the bearing capacity and safety of the caisson structure was evaluated. The results showed that under the 1.1 times horizontal design load, the maximum deformation of the shaft wall for the caisson structure was about 1/1 000 length of the shaft wall, and the stress at each point was less than the yield strength of the material. The caisson structure had great rigidity and the high bearing capacity. The braces and walings of the caisson could effectively improve the stress in the shaft wall and enhance the overall mechanical performances of the caisson structure. The caisson structure was a reasonable structure which could meet the requirements of safety and use.
A new type of prefabricated concrete-filled steel box composite caisson structure was proposed. In order to study mechanical properties of the caisson structure under the water and soil pressure, a full-scale test structure was designed based on the Dayang Parking underground garage project. A static loading test for the structure was conducted to analyze deformation and stress characteristics of the caisson structure under horizontal loads when it was sunk to the design elevation and the baseplate was not sealed, and then the bearing capacity and safety of the caisson structure was evaluated. The results showed that under the 1.1 times horizontal design load, the maximum deformation of the shaft wall for the caisson structure was about 1/1 000 length of the shaft wall, and the stress at each point was less than the yield strength of the material. The caisson structure had great rigidity and the high bearing capacity. The braces and walings of the caisson could effectively improve the stress in the shaft wall and enhance the overall mechanical performances of the caisson structure. The caisson structure was a reasonable structure which could meet the requirements of safety and use.
2023, 53(1): 207-211,222.
doi: 10.13204/j.gyjzG21090606
Abstract:
In order to solve the problem that prefabricated vertical drains (PVDs) are prone to be silted and lead to poor soil reinforcement effect and non-uniform consolidation in the process of treating soft soil by vacuum preloading with prefabricated vertical drains, a comparative model test between vacuum preloading on twice setting of prefabricated vertical drains and two-stage zonal vacuum preloading on prefabricated vertical drains was conducted. By comparing the indexes of site soil involving subsidence, cross-plate vane shear strength and the water content treated by the above two methods, the improvement effect of the two methods was explored. The test results showed that the maximum subsidence of vacuum preloading on twice setting of prefabricated vertical drains and two-stage zonal vacuum preloading on prefabricated vertical drains was 208 mm and 170 mm respectively; the average cross-plate vane shear strength of soil improved by the two methods were 29.5 kPa and 24.75 kPa respectively. It showed that the improvement effect of vacuum preloading by twice setting of prefabricated vertical drains on ultrasoft soil was better than that by two-stage zonal vacuum preloading on prefabricated vertical drains.
In order to solve the problem that prefabricated vertical drains (PVDs) are prone to be silted and lead to poor soil reinforcement effect and non-uniform consolidation in the process of treating soft soil by vacuum preloading with prefabricated vertical drains, a comparative model test between vacuum preloading on twice setting of prefabricated vertical drains and two-stage zonal vacuum preloading on prefabricated vertical drains was conducted. By comparing the indexes of site soil involving subsidence, cross-plate vane shear strength and the water content treated by the above two methods, the improvement effect of the two methods was explored. The test results showed that the maximum subsidence of vacuum preloading on twice setting of prefabricated vertical drains and two-stage zonal vacuum preloading on prefabricated vertical drains was 208 mm and 170 mm respectively; the average cross-plate vane shear strength of soil improved by the two methods were 29.5 kPa and 24.75 kPa respectively. It showed that the improvement effect of vacuum preloading by twice setting of prefabricated vertical drains on ultrasoft soil was better than that by two-stage zonal vacuum preloading on prefabricated vertical drains.
Reviews of Research on Mechanical Properties and Durability of Coal Gangue Coarse Aggregate Concrete
2023, 53(1): 212-222.
doi: 10.13204/j.gyjzG22040503
Abstract:
Coal gangue is one of the solid wastes with the largest emission in China. The application of coal gangue as a coarse aggregate in concrete conforms to the concept of green environmental protection, energy saving and emission reduction, and has received extensive attention from the construction industry and researchers. On the basis of sammarizing research progress of coal gangue coarse aggregate concrete, the chemical composition and physical properties of coal gangue in different zones of China were introduced, and the influence of the coal gangue coarse aggregate content on the slump, mechanical properties, durability and microstructure of concrete were summarized.Through the analysis of the existing research results of coal gangue coarse aggregate concrete, the future research directions of coal gangue coarse aggregate concrete were prospected.
Coal gangue is one of the solid wastes with the largest emission in China. The application of coal gangue as a coarse aggregate in concrete conforms to the concept of green environmental protection, energy saving and emission reduction, and has received extensive attention from the construction industry and researchers. On the basis of sammarizing research progress of coal gangue coarse aggregate concrete, the chemical composition and physical properties of coal gangue in different zones of China were introduced, and the influence of the coal gangue coarse aggregate content on the slump, mechanical properties, durability and microstructure of concrete were summarized.Through the analysis of the existing research results of coal gangue coarse aggregate concrete, the future research directions of coal gangue coarse aggregate concrete were prospected.
2023, 53(1): 223-232,56.
doi: 10.13204/j.gyjzG22072409
Abstract:
Due to the excellent mechanical properties of fiber-reinforced polymers (FRP) for improving the mechanical properties of wood and strengthening and repairing timber structures, it has become the focus of research on new composite materials. FRP-wood bonding reinforcement is affected by the synergistic effect of multiple factors such as FRP materials, wood matrices and adhesives, and the bonding state of its interface is particularly momentous, which determines the performance and life of the composite structure. Therefore, combined the biological properties of wood and the unique structural characteristics of wood structure, the five aspects were systematically combed, that was material changes, pretreatment, FRP formation, adhesive properties, and environmental condition. And the latest domestic and foreign research results of FRP-wood interface bonding properties were summarized to clarify the coupling factors that affect the bonding performance of FRP-wood interfaces. In addition, the deficiencies in research were analyzed of existing FRP-wood bonding and reinforcement, and the new trends, new developments and new directions for future research were imagined, which might provide important reference to the future expansion of FRP high-quality and high-efficiency application, especially the protection of ancient architectural wood structures.
Due to the excellent mechanical properties of fiber-reinforced polymers (FRP) for improving the mechanical properties of wood and strengthening and repairing timber structures, it has become the focus of research on new composite materials. FRP-wood bonding reinforcement is affected by the synergistic effect of multiple factors such as FRP materials, wood matrices and adhesives, and the bonding state of its interface is particularly momentous, which determines the performance and life of the composite structure. Therefore, combined the biological properties of wood and the unique structural characteristics of wood structure, the five aspects were systematically combed, that was material changes, pretreatment, FRP formation, adhesive properties, and environmental condition. And the latest domestic and foreign research results of FRP-wood interface bonding properties were summarized to clarify the coupling factors that affect the bonding performance of FRP-wood interfaces. In addition, the deficiencies in research were analyzed of existing FRP-wood bonding and reinforcement, and the new trends, new developments and new directions for future research were imagined, which might provide important reference to the future expansion of FRP high-quality and high-efficiency application, especially the protection of ancient architectural wood structures.
2023, 53(1): 233-239.
doi: 10.13204/j.gyjzG22102605
Abstract:
Taking the typical ZT-type old welded tower as an example, based on the uncertainty in service and potential safety risk caused by the missing design data, changes in design specifications and damages in service, a inspection method in service was proposed. The influence of the change of constraint conditions and different corrosion ratios in steels on the failure mode of ZT-type old welded towers was discussed. The results showed that according to the new design code, the rods of main members did not meet the requiments under a gale, in the 90° direction and the uneven icing. The post-constructed concrete platform changed the stress of the tower, the failure zone developed from the lower part of the tower towards the middle. Due to the changes of constraint conditions and deficiency of rods, the main members in segment No.2 and No.4 of the tower would fail under a gale of 18 m/s in the 90° direction.
Taking the typical ZT-type old welded tower as an example, based on the uncertainty in service and potential safety risk caused by the missing design data, changes in design specifications and damages in service, a inspection method in service was proposed. The influence of the change of constraint conditions and different corrosion ratios in steels on the failure mode of ZT-type old welded towers was discussed. The results showed that according to the new design code, the rods of main members did not meet the requiments under a gale, in the 90° direction and the uneven icing. The post-constructed concrete platform changed the stress of the tower, the failure zone developed from the lower part of the tower towards the middle. Due to the changes of constraint conditions and deficiency of rods, the main members in segment No.2 and No.4 of the tower would fail under a gale of 18 m/s in the 90° direction.
