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The Top 20 Most-Cited Papers from 2022 to 2023
2023 Vol. 38, No. 3
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2023, 38(3): 1-12.
doi: 10.13206/j.gjgS23010301
Abstract
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Abstract:
The finite element numerical simulation of the inner sleeve connected joint between the modules of the fabricated modular steel frame was carried out. The influences of the gap between the inner sleeve and the column wall, the thickness and the length of the inner sleeve on the bearing capacity of the joint were studied. The forming mechanism and theoretical calculation formula of the contact force between the column wall and the inner sleeve were analyzed. The formula for calculating the contact force between the inner sleeve and the column wall was derived and compared with the finite element numerical results. The research showed that the reserved gap between the inner sleeve and the column wall had a significant impact on the bearing capacity, stress distribution and contact force of the joint. When there was no gap between the inner sleeve and the column wall, the stress distribution of the column wall in the joint area was more uniform. With the increase of the reserved installation gap, the contact stress between the inner sleeve and the column wall was uneven, and the bearing capacity of the joint decreased. It is recommended that the reserved gap between the inner sleeve and the column wall should not exceed 4 mm; When the inner sleeve thickness was greater than the column wall thickness, the joint stress distribution was more uniform, it is recommended that the inner sleeve thickness should be greater than the column wall thickness of 1 to 2 mm. Appropriately increasing the length of the inner sleeve is beneficial to the uniform distribution of joint stress and improve joint bearing capacity. It is suggested that the inner sleeve should extend the upper beam flange and the lower beam flange by 30 to 50 mm respectively. The error between the theoretical calculation formula and the numerical calculation result of the contact force between the column wall and the inner sleeve was about 10%, because the influence of axial bending deformation of the column was ignored in formula.
The finite element numerical simulation of the inner sleeve connected joint between the modules of the fabricated modular steel frame was carried out. The influences of the gap between the inner sleeve and the column wall, the thickness and the length of the inner sleeve on the bearing capacity of the joint were studied. The forming mechanism and theoretical calculation formula of the contact force between the column wall and the inner sleeve were analyzed. The formula for calculating the contact force between the inner sleeve and the column wall was derived and compared with the finite element numerical results. The research showed that the reserved gap between the inner sleeve and the column wall had a significant impact on the bearing capacity, stress distribution and contact force of the joint. When there was no gap between the inner sleeve and the column wall, the stress distribution of the column wall in the joint area was more uniform. With the increase of the reserved installation gap, the contact stress between the inner sleeve and the column wall was uneven, and the bearing capacity of the joint decreased. It is recommended that the reserved gap between the inner sleeve and the column wall should not exceed 4 mm; When the inner sleeve thickness was greater than the column wall thickness, the joint stress distribution was more uniform, it is recommended that the inner sleeve thickness should be greater than the column wall thickness of 1 to 2 mm. Appropriately increasing the length of the inner sleeve is beneficial to the uniform distribution of joint stress and improve joint bearing capacity. It is suggested that the inner sleeve should extend the upper beam flange and the lower beam flange by 30 to 50 mm respectively. The error between the theoretical calculation formula and the numerical calculation result of the contact force between the column wall and the inner sleeve was about 10%, because the influence of axial bending deformation of the column was ignored in formula.
2023, 38(3): 13-23.
doi: 10.13206/j.gjgS22110104
Abstract:
As a new type of steel, Q355 has been widely used in the field of construction due to its excellent mechanical properties. However, it has the fatal disadvantage of poor fire resistance, which is dangerous to steel structure buildings. Through the safety appraisal and bearing capacity evaluation of steel structure buildings after fire, the waste caused by demolition and reconstruction can be effectively avoided, and corresponding measures can be taken to repair or replace the components, which can greatly save economic costs. Therefore, it is necessary to study the residual mechanical properties of Q355 steel after fire. In order to simulate the situation of Q355 steel after fire and fire extinguishing, the conditions of 200 to 900℃, natural cooling and water cooling were set to simulate the fire, and the mechanical properties of Q355 steel after high temperature were tested. With the help of high temperature furnace, universal testing machine and electronic extensometer, the stress-strain curve and mechanical properties parameters (yield strength, tensile strength, ratio of yield strength to ultimate tensile strength, elastic modulus and elongation, etc) of Q355 steel after high temperature cooling were obtained. The influence of temperature and cooling method on the stress-strain curve and mechanical parameters was analyzed. The mechanical properties of Q355 steel and Q235, Q460 and Q690 steel after high temperature were compared and analyzed. The mathematical model of mechanical properties of Q355 steel under different cooling methods was fitted by ORIGIN data processing software. It was found that there were significant differences in the different apparent characteristics, failure modes and mechanical properties of Q355 steel for different temperatures and cooling methods. The surface carbonization degree of Q355 steel gradually deepened with the increase of temperature. When the exposure temperature exceeds 600℃, the carbonization phenomenon become more obvious, and even when immersed in water for cooling, the carbonization skin peeled off. When the temperature does not exceed 600℃, the apparent morphology change characteristics were small and the deformation degree of the tensile specimen was light, which was similar to the appearance and deformation of the specimen without high temperature. In addition, 600℃ was also the critical temperature for the change of residual mechanical properties of Q355 steel. When the temperature was lower than 600℃, the effect of temperatures and cooling methods on the mechanical properties of Q355 steel was negligible. However, when the temperature was higher than 600℃, temperatures and cooling methods exerted a distinct influence on the mechanical properties of Q355 steel. After air cooling, the yield strength, tensile strength, and elastic modulus of Q355 steel decreased with the increase in temperature, but the ultimate elongation increased with the increase in temperature. After water cooling, the yield strength and tensile strength of Q355 steel increased with the increase in temperature, while the elastic modulus and ultimate elongation decreased with the increase in temperature. Furthermore, the predictive equations were proposed to determine the post-fire material properties of Q355 steel for cooling in air and cooling in water.
As a new type of steel, Q355 has been widely used in the field of construction due to its excellent mechanical properties. However, it has the fatal disadvantage of poor fire resistance, which is dangerous to steel structure buildings. Through the safety appraisal and bearing capacity evaluation of steel structure buildings after fire, the waste caused by demolition and reconstruction can be effectively avoided, and corresponding measures can be taken to repair or replace the components, which can greatly save economic costs. Therefore, it is necessary to study the residual mechanical properties of Q355 steel after fire. In order to simulate the situation of Q355 steel after fire and fire extinguishing, the conditions of 200 to 900℃, natural cooling and water cooling were set to simulate the fire, and the mechanical properties of Q355 steel after high temperature were tested. With the help of high temperature furnace, universal testing machine and electronic extensometer, the stress-strain curve and mechanical properties parameters (yield strength, tensile strength, ratio of yield strength to ultimate tensile strength, elastic modulus and elongation, etc) of Q355 steel after high temperature cooling were obtained. The influence of temperature and cooling method on the stress-strain curve and mechanical parameters was analyzed. The mechanical properties of Q355 steel and Q235, Q460 and Q690 steel after high temperature were compared and analyzed. The mathematical model of mechanical properties of Q355 steel under different cooling methods was fitted by ORIGIN data processing software. It was found that there were significant differences in the different apparent characteristics, failure modes and mechanical properties of Q355 steel for different temperatures and cooling methods. The surface carbonization degree of Q355 steel gradually deepened with the increase of temperature. When the exposure temperature exceeds 600℃, the carbonization phenomenon become more obvious, and even when immersed in water for cooling, the carbonization skin peeled off. When the temperature does not exceed 600℃, the apparent morphology change characteristics were small and the deformation degree of the tensile specimen was light, which was similar to the appearance and deformation of the specimen without high temperature. In addition, 600℃ was also the critical temperature for the change of residual mechanical properties of Q355 steel. When the temperature was lower than 600℃, the effect of temperatures and cooling methods on the mechanical properties of Q355 steel was negligible. However, when the temperature was higher than 600℃, temperatures and cooling methods exerted a distinct influence on the mechanical properties of Q355 steel. After air cooling, the yield strength, tensile strength, and elastic modulus of Q355 steel decreased with the increase in temperature, but the ultimate elongation increased with the increase in temperature. After water cooling, the yield strength and tensile strength of Q355 steel increased with the increase in temperature, while the elastic modulus and ultimate elongation decreased with the increase in temperature. Furthermore, the predictive equations were proposed to determine the post-fire material properties of Q355 steel for cooling in air and cooling in water.
2023, 38(3): 24-33.
doi: 10.13206/j.gjgS22120501
Abstract:
To improve the efficiency of finite element numerical calculation of steel frame solid structure, the simplified theoretical model of joint was used to simplify the assembled embedded joint with cantilever beam, the assembled reinforced embedded joint with cantilever beam, the traditional beam-column connection joint with cantilever beam and the embedded bolt-welded hybrid joint with cantilever beam. The static analysis and pseudo-static analysis of four joint simplified models, one-story one-bay frame simplified model and frame solid model were carried out by ABAQUS finite element software, respectively. The calculation results of joint simplified model and joint solid model were compared and analyzed, and the calculation results of frame simplified model and frame solid model were compared and analyzed. The analysis results showed that:1) the difference of joint stiffness, yield load and ultimate load calculated by the simplified model and the solid model of the joint under unidirectional static load was small. The hysteretic curve, skeleton curve and stiffness degradation curve of the two models under cyclic loading were basically the same. The joint simplified model could reflect the mechanical properties of the joint solid model largely. 2) Under the action of unidirectional static load, the difference between the yield load and ultimate load of the structure calculated by the frame simplified model and the frame solid model was small. Under the action of reciprocating cyclic load, the bearing capacity, frame stiffness, hysteretic performance and energy dissipation capacity of the frame structure calculated by the two frame models were the same basically, and the calculation results were in good agreement. 3) The joint simplified model and the frame simplified model were used to calculate four kinds of joints and frames with cantilever beam. The calculation results had certain accuracy. Compared with the joint and frame solid model, the analysis efficiency of the joint simplified model and the frame simplified model was improved by more than 95%, and the calculation cost was greatly reduced.
To improve the efficiency of finite element numerical calculation of steel frame solid structure, the simplified theoretical model of joint was used to simplify the assembled embedded joint with cantilever beam, the assembled reinforced embedded joint with cantilever beam, the traditional beam-column connection joint with cantilever beam and the embedded bolt-welded hybrid joint with cantilever beam. The static analysis and pseudo-static analysis of four joint simplified models, one-story one-bay frame simplified model and frame solid model were carried out by ABAQUS finite element software, respectively. The calculation results of joint simplified model and joint solid model were compared and analyzed, and the calculation results of frame simplified model and frame solid model were compared and analyzed. The analysis results showed that:1) the difference of joint stiffness, yield load and ultimate load calculated by the simplified model and the solid model of the joint under unidirectional static load was small. The hysteretic curve, skeleton curve and stiffness degradation curve of the two models under cyclic loading were basically the same. The joint simplified model could reflect the mechanical properties of the joint solid model largely. 2) Under the action of unidirectional static load, the difference between the yield load and ultimate load of the structure calculated by the frame simplified model and the frame solid model was small. Under the action of reciprocating cyclic load, the bearing capacity, frame stiffness, hysteretic performance and energy dissipation capacity of the frame structure calculated by the two frame models were the same basically, and the calculation results were in good agreement. 3) The joint simplified model and the frame simplified model were used to calculate four kinds of joints and frames with cantilever beam. The calculation results had certain accuracy. Compared with the joint and frame solid model, the analysis efficiency of the joint simplified model and the frame simplified model was improved by more than 95%, and the calculation cost was greatly reduced.
2023, 38(3): 34-42.
doi: 10.13206/j.gjgS23010201
Abstract:
In order to further study the failure mode and mechanical characteristics of large diameter stud in ultra-high performance concrete (UHPC) and normal concrete (NC), the push-out tests of 7 groups of specimens were carried out. The influences of concrete strength, slab thickness, stud diameter, stud length-diameter ratio and concrete specimen size on the ultimate shear capacity of large diameter stud were analyzed in detail. The results showed that the failure mode of large diameter stud UHPC was stud shear. UHPC could effectively resist the splitting force generated by the stud and prevent the splitting failure of concrete slabs effectively. Compared with NC specimens, UHPC specimens had higher shear capacity and shear stiffness, but lower ductility. In UHPC specimens, the length-diameter ratio of large diameter stud, the thickness of concrete slab and the size of concrete slab had little influence on the shear capacity, shear stiffness and ultimate slip of the stud. Finally, according to the test results, the proposed formula for calculating loadslip curve and shear capacity of UHPC large diameter stud under shear failure mode were proposed, which could provide certain reference value for the engineering design of steel-UHPC composite structure.
In order to further study the failure mode and mechanical characteristics of large diameter stud in ultra-high performance concrete (UHPC) and normal concrete (NC), the push-out tests of 7 groups of specimens were carried out. The influences of concrete strength, slab thickness, stud diameter, stud length-diameter ratio and concrete specimen size on the ultimate shear capacity of large diameter stud were analyzed in detail. The results showed that the failure mode of large diameter stud UHPC was stud shear. UHPC could effectively resist the splitting force generated by the stud and prevent the splitting failure of concrete slabs effectively. Compared with NC specimens, UHPC specimens had higher shear capacity and shear stiffness, but lower ductility. In UHPC specimens, the length-diameter ratio of large diameter stud, the thickness of concrete slab and the size of concrete slab had little influence on the shear capacity, shear stiffness and ultimate slip of the stud. Finally, according to the test results, the proposed formula for calculating loadslip curve and shear capacity of UHPC large diameter stud under shear failure mode were proposed, which could provide certain reference value for the engineering design of steel-UHPC composite structure.
2023, 38(3): 43-50.
doi: 10.13206/j.gjgS23012101
Abstract:
The fully dry-connected prefabricated slab completely avoids wet work on the construction site, which can make full use of the advantages of short construction period and environmental protection of the steel structures. However, due to the feature of completely prefabrication of the slab, it requires high installation accuracy. Existing BIM technologies cannot consider the production and assembly errors of prefabricated components. In order to solve the problem of increased costs such as time, transportation and manpower when return to the factory for remanufacturing caused by the failure of on-site assembly due to insufficient production accuracy of the fully dry-connected prefabricated slab, a refined installation management method based on BIM+3D laser scanning technology was proposed for the fully dry-connected prefabricated slab, which could complete precision detection and virtual assembly in the storage stage of prefabricated components, effectively avoiding cost waste caused by insufficient accuracy. The refined installation management method established a spatial coordinate system using a total station in precast component factory, and determined the position coordinates of each component in space through target points, and then used a three-dimensional laser scanner to scan the cover and base slab unit of the fully dry-connected prefabricated slab to obtain the point cloud data of each component. The advanced data post-processing software MAGNET Collage was applied to achieve target splicing, point cloud data fitting, point cloud segmentation and extraction, noise reduction and coordinate system establishment so as to obtain the point cloud model of each component and its spatial position, namely, the real scene replication of the component and its spatial position in the geometry sense was realized, and the digital twin model of each component of the fully dry connected prefabricated slab with production and assembly errors was obtained. Comparing and analyzing the digital model and the ideal BIM model created according to the drawings by docking and matching the spatial coordinate systems could obtain the size and position of the corresponding errors of the prefabricated components. The assembly errors of each component in the actual installation could be obtained through the virtual preassembly between the digital models of the cover and base slab units, adjusted the coordinates of the reference points to correct the errors and output the final coordinate adjustment data to guide the on-site installation of the corresponding components. Based on the above technologies, the construction quality and safety management method of the slab were proposed, which coordinates and manages the process from factory prefabrication to on-site assembly of the fully dry-connected prefabricated slab through the five stages of production, warehousing, pre-assembly, transportation and construction. The results showed that the refined installation management method can quickly obtain the digital twin model of the fully dryconnected prefabricated slab, and analyze its production accuracy, the maximum relative error is 5%, which meets the accuracy requirements; the assemble problems that may occur in site construction due to accumulated errors can be predicted through virtual preassembly, improving the on-site installation efficiency of the fully dry-connected prefabricated slabs in steel structures, effectively avoiding cost waste caused by insufficient accuracy. The refined installation management method based on BIM+ 3D laser scanning technology can be extended to other prefabricated structures with high accuracy requirements.
The fully dry-connected prefabricated slab completely avoids wet work on the construction site, which can make full use of the advantages of short construction period and environmental protection of the steel structures. However, due to the feature of completely prefabrication of the slab, it requires high installation accuracy. Existing BIM technologies cannot consider the production and assembly errors of prefabricated components. In order to solve the problem of increased costs such as time, transportation and manpower when return to the factory for remanufacturing caused by the failure of on-site assembly due to insufficient production accuracy of the fully dry-connected prefabricated slab, a refined installation management method based on BIM+3D laser scanning technology was proposed for the fully dry-connected prefabricated slab, which could complete precision detection and virtual assembly in the storage stage of prefabricated components, effectively avoiding cost waste caused by insufficient accuracy. The refined installation management method established a spatial coordinate system using a total station in precast component factory, and determined the position coordinates of each component in space through target points, and then used a three-dimensional laser scanner to scan the cover and base slab unit of the fully dry-connected prefabricated slab to obtain the point cloud data of each component. The advanced data post-processing software MAGNET Collage was applied to achieve target splicing, point cloud data fitting, point cloud segmentation and extraction, noise reduction and coordinate system establishment so as to obtain the point cloud model of each component and its spatial position, namely, the real scene replication of the component and its spatial position in the geometry sense was realized, and the digital twin model of each component of the fully dry connected prefabricated slab with production and assembly errors was obtained. Comparing and analyzing the digital model and the ideal BIM model created according to the drawings by docking and matching the spatial coordinate systems could obtain the size and position of the corresponding errors of the prefabricated components. The assembly errors of each component in the actual installation could be obtained through the virtual preassembly between the digital models of the cover and base slab units, adjusted the coordinates of the reference points to correct the errors and output the final coordinate adjustment data to guide the on-site installation of the corresponding components. Based on the above technologies, the construction quality and safety management method of the slab were proposed, which coordinates and manages the process from factory prefabrication to on-site assembly of the fully dry-connected prefabricated slab through the five stages of production, warehousing, pre-assembly, transportation and construction. The results showed that the refined installation management method can quickly obtain the digital twin model of the fully dryconnected prefabricated slab, and analyze its production accuracy, the maximum relative error is 5%, which meets the accuracy requirements; the assemble problems that may occur in site construction due to accumulated errors can be predicted through virtual preassembly, improving the on-site installation efficiency of the fully dry-connected prefabricated slabs in steel structures, effectively avoiding cost waste caused by insufficient accuracy. The refined installation management method based on BIM+ 3D laser scanning technology can be extended to other prefabricated structures with high accuracy requirements.
2023, 38(3): 51-53.
doi: 10.13206/j.gjgS22102815
Abstract:
The relation between the applicable ductility factor with the factor of the second-order effect was presented, the seismic forces for three different fortification aims were presented. Considerations of the dynamic stability in seismic design in the codes of USA, Europe and New Zealand were briefly introduced. Formulas for the static and dynamic elastic-plastic second-order effects were presented and the amplification factors of seismic action due to the elastic-plastic dynamic second-order effect was presented.
The relation between the applicable ductility factor with the factor of the second-order effect was presented, the seismic forces for three different fortification aims were presented. Considerations of the dynamic stability in seismic design in the codes of USA, Europe and New Zealand were briefly introduced. Formulas for the static and dynamic elastic-plastic second-order effects were presented and the amplification factors of seismic action due to the elastic-plastic dynamic second-order effect was presented.
