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2023 Vol. 53, No. 5
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2023, 53(5): 1-6.
doi: 10.13204/j.gyjzG22031905
Abstract:
To study the axial compressive behaviour of the L-shaped column composed of recycled aggregate concrete-filled square steel tubes(L-RACFST), the numerical studies on the L-RACFST columns and verified the numerical model were performed based on the test result. The finite element analysis results showed that when the replacement ratio of recycled aggregate coarse (RAC) exceeded 40%, the elastic-plastic stage was not obvious, and the curve tended to directly enter the plastic stage. Parametric study was performed considering the effect of steel strength, the steel tube thickness, the width of square steel tube and the connecting plate, etc. With the increase in the replacement ratio of RAC, the bearing capacity, stiffness and ductility of the L-RACFST columns decreased. With the same replacement ratio of RAC, the peak bearing capacity of the L-RACFST columns increased gradually with the increase of steel strength, steel tube thickness and square steel tube width. The width of the connecting plate had little effect on the peak bearing capacity of the specimen.
To study the axial compressive behaviour of the L-shaped column composed of recycled aggregate concrete-filled square steel tubes(L-RACFST), the numerical studies on the L-RACFST columns and verified the numerical model were performed based on the test result. The finite element analysis results showed that when the replacement ratio of recycled aggregate coarse (RAC) exceeded 40%, the elastic-plastic stage was not obvious, and the curve tended to directly enter the plastic stage. Parametric study was performed considering the effect of steel strength, the steel tube thickness, the width of square steel tube and the connecting plate, etc. With the increase in the replacement ratio of RAC, the bearing capacity, stiffness and ductility of the L-RACFST columns decreased. With the same replacement ratio of RAC, the peak bearing capacity of the L-RACFST columns increased gradually with the increase of steel strength, steel tube thickness and square steel tube width. The width of the connecting plate had little effect on the peak bearing capacity of the specimen.
2023, 53(5): 7-16,173.
doi: 10.13204/j.gyjzG22042402
Abstract:
In order to study the seismic performance of the wide-flange L-shaped CFST composite column with built-in PBL (W-LCFST column), based on the existing test results, the numerical simulation of the L-shaped CFST composite column with built-in PBL was carried out, considering the ductile fracture failure of steel. The model results could well predict the location of the crack initiation point, the crack path and the load-displacement curve. Further comparison and analysis of parameters such as PBL separators quantity, PBL hole spacing, PBL hole size, side column size, axial compression ratio and steel pipe thickness were carried out. The results showed that when the number of PBL separators was increased from 2 to 6, the restraint effect on the core concrete was improved, and the displacement ductility coefficient was increased by 14.5%; the size of the PBL pore diameter and the spacing of the pores only affected the plastic stage. Before reaching the peak load, PBL partitions with a pore diameter of 51 mm were easily reduced in the unfavorable position and caused the W-LCFST pillar to be reduced. The concrete tenon in the PBL partition with a pore diameter of 17 mm was more likely to be cut and damaged, and the carrying capacity decreased rapidly; the axis pressure ratio was within the range of 0.25 to 0.55, and the bearing capacity of the W-LCFST column was increased first. The initial stiffness and the peak bearing capacity could be increased with the increase of the sizes of the edge column and the thickness of the steel pipe. When the sizes of the edge column increased from 100 mm×100 mm to 140 mm×100 mm, the initial stiffness increased by 13.7%. After the thickness of the steel pipe increased from 6 mm to 8 mm, the positive peak bearing capacity increased by 21.8%.
In order to study the seismic performance of the wide-flange L-shaped CFST composite column with built-in PBL (W-LCFST column), based on the existing test results, the numerical simulation of the L-shaped CFST composite column with built-in PBL was carried out, considering the ductile fracture failure of steel. The model results could well predict the location of the crack initiation point, the crack path and the load-displacement curve. Further comparison and analysis of parameters such as PBL separators quantity, PBL hole spacing, PBL hole size, side column size, axial compression ratio and steel pipe thickness were carried out. The results showed that when the number of PBL separators was increased from 2 to 6, the restraint effect on the core concrete was improved, and the displacement ductility coefficient was increased by 14.5%; the size of the PBL pore diameter and the spacing of the pores only affected the plastic stage. Before reaching the peak load, PBL partitions with a pore diameter of 51 mm were easily reduced in the unfavorable position and caused the W-LCFST pillar to be reduced. The concrete tenon in the PBL partition with a pore diameter of 17 mm was more likely to be cut and damaged, and the carrying capacity decreased rapidly; the axis pressure ratio was within the range of 0.25 to 0.55, and the bearing capacity of the W-LCFST column was increased first. The initial stiffness and the peak bearing capacity could be increased with the increase of the sizes of the edge column and the thickness of the steel pipe. When the sizes of the edge column increased from 100 mm×100 mm to 140 mm×100 mm, the initial stiffness increased by 13.7%. After the thickness of the steel pipe increased from 6 mm to 8 mm, the positive peak bearing capacity increased by 21.8%.
2023, 53(5): 17-27.
doi: 10.13204/j.gyjzG22072605
Abstract:
Concrete-filled stainless steel tubular columns show excellent prospects for application in corrosive environments such as harbor engineering and marine engineering. To further develop the performance of such structures, a composite structure, i. e. steel-reinforced ultra-high performance concrete-filled stainless steel tubular column was proposed in this paper. Meanwhile, six short and eight medium-length column specimens were designed and fabricated with the parameters of diameter to thickness ratio, length to diameter ratio, steel profile content ratios, etc. Axial compression experiments and finite element analysis were executed to investigate the failure mode and failure mechanism of the specimens, as well as the influence of relevant parameters on the mechanical performance of the specimens. The results showed that the bearing capacity and ductility of the specimens increased with the decreasing of the diameter to thickness ratios and length to diameter ratios, and increased with the increding of the steel profile content ratios and strength of the pre-embedded steel profile; the ductility of the specimen decreased with the increase in core concrete strength, but the bearing capacity was the opposite. Based on the experimental and finite element results, a prediction model for the bearing capacity of steel-reinforced ultra-high performance concrete-filled stainless steel tubular was proposed, providing a reference for the engineering application of such structures.
Concrete-filled stainless steel tubular columns show excellent prospects for application in corrosive environments such as harbor engineering and marine engineering. To further develop the performance of such structures, a composite structure, i. e. steel-reinforced ultra-high performance concrete-filled stainless steel tubular column was proposed in this paper. Meanwhile, six short and eight medium-length column specimens were designed and fabricated with the parameters of diameter to thickness ratio, length to diameter ratio, steel profile content ratios, etc. Axial compression experiments and finite element analysis were executed to investigate the failure mode and failure mechanism of the specimens, as well as the influence of relevant parameters on the mechanical performance of the specimens. The results showed that the bearing capacity and ductility of the specimens increased with the decreasing of the diameter to thickness ratios and length to diameter ratios, and increased with the increding of the steel profile content ratios and strength of the pre-embedded steel profile; the ductility of the specimen decreased with the increase in core concrete strength, but the bearing capacity was the opposite. Based on the experimental and finite element results, a prediction model for the bearing capacity of steel-reinforced ultra-high performance concrete-filled stainless steel tubular was proposed, providing a reference for the engineering application of such structures.
2023, 53(5): 28-34.
doi: 10.13204/j.gyjzG22012008
Abstract:
To investigate the improving effect of reinforcement on the loading performance of recycled concrete-filled circular steel tube (RACFST) columns with 100% replacement-ratio of recycled coarse aggregate, axial compression tests of reinforced RACFST (R-RACFST) with varying longitudinal reinforcement ratio were conducted. The comparative analysis results on key mechanical indices, such as failure mode, load-displacement curve, stiffness, yield-to-strength ratio and the composite effect, showed that the reinforcement could effectively mitigate the brittleness of recycled concrete core, and improved the peak load and the after-peak plastic deformation capacity, and relieved the degradation in stiffness; as far as the yield-to-strength ratio and composite effect are concerned, larger ratio of reinforcement not necessarily brought larger increase in performance, namely in a proper range of ratio, reinforcement would bring better composite effect, and could better utilize the reinforcement. As results, configuring a little amount of reinforcement would put the R-RACFST member with 100% replacement-ratio of recycled coarse aggregate into better mechanical performance, and hereby make it possible to use recycled coarse aggregate 100%; a proper range of reinforcement ratio was recommended as 0.84%-3.9%; the proposed equation for predicting the ultimate load bearing capacity of R-RACFST was stable and reliable.
To investigate the improving effect of reinforcement on the loading performance of recycled concrete-filled circular steel tube (RACFST) columns with 100% replacement-ratio of recycled coarse aggregate, axial compression tests of reinforced RACFST (R-RACFST) with varying longitudinal reinforcement ratio were conducted. The comparative analysis results on key mechanical indices, such as failure mode, load-displacement curve, stiffness, yield-to-strength ratio and the composite effect, showed that the reinforcement could effectively mitigate the brittleness of recycled concrete core, and improved the peak load and the after-peak plastic deformation capacity, and relieved the degradation in stiffness; as far as the yield-to-strength ratio and composite effect are concerned, larger ratio of reinforcement not necessarily brought larger increase in performance, namely in a proper range of ratio, reinforcement would bring better composite effect, and could better utilize the reinforcement. As results, configuring a little amount of reinforcement would put the R-RACFST member with 100% replacement-ratio of recycled coarse aggregate into better mechanical performance, and hereby make it possible to use recycled coarse aggregate 100%; a proper range of reinforcement ratio was recommended as 0.84%-3.9%; the proposed equation for predicting the ultimate load bearing capacity of R-RACFST was stable and reliable.
2023, 53(5): 35-40,117.
doi: 10.13204/j.gyjzG21022307
Abstract:
In order to study the bearing performance (axial compression, eccentric compression) and bearing capacity calculation method of composite cross shaped concrete-filled steel tubular column, the expansion analysis of 26 specimens was carried out by using the finite element software ABAQUS, combined with the measured data of 6 specimens, and taking the eccentricity, slenderness ratio, section steel ratio, concrete strength grade and steel yield strength as changing parameters. The influence of various influencing parameters on the bearing capacity of composite cross shaped concrete-filled steel tubular columns was discussed. The calculation methods of ultimate bearing capacity of axial compression columns and eccentric compression columns of composite cross shaped concrete-filled steel tubular columns were studied respectively, and practical design formulas were put forward. The results showed that the ultimate bearing capacity of composite cross shaped concrete-filled steel tubular columns decreased with the increase of eccentricity and slenderness ratio, and cncreased with the increase of steel ratio, concrete strength and steel yield strength. When the eccentricity and concrete strength were small, the bearing capacity degenerated rapidly, the bearing capacity increased nearly linearly with the increase of steel content, and the improvement of channel steel strength could improve the bearing capacity of the specimen. The calculation method of ultimate bearing capacity of composite cross shaped concrete-filled steel tubular (axial pressure and eccentric pressure) based on confined concrete theory had good applicability.
In order to study the bearing performance (axial compression, eccentric compression) and bearing capacity calculation method of composite cross shaped concrete-filled steel tubular column, the expansion analysis of 26 specimens was carried out by using the finite element software ABAQUS, combined with the measured data of 6 specimens, and taking the eccentricity, slenderness ratio, section steel ratio, concrete strength grade and steel yield strength as changing parameters. The influence of various influencing parameters on the bearing capacity of composite cross shaped concrete-filled steel tubular columns was discussed. The calculation methods of ultimate bearing capacity of axial compression columns and eccentric compression columns of composite cross shaped concrete-filled steel tubular columns were studied respectively, and practical design formulas were put forward. The results showed that the ultimate bearing capacity of composite cross shaped concrete-filled steel tubular columns decreased with the increase of eccentricity and slenderness ratio, and cncreased with the increase of steel ratio, concrete strength and steel yield strength. When the eccentricity and concrete strength were small, the bearing capacity degenerated rapidly, the bearing capacity increased nearly linearly with the increase of steel content, and the improvement of channel steel strength could improve the bearing capacity of the specimen. The calculation method of ultimate bearing capacity of composite cross shaped concrete-filled steel tubular (axial pressure and eccentric pressure) based on confined concrete theory had good applicability.
Experimental Study on Cyclic Loading of Asymmetric Friction Joints of Steel-Concrete Composite Beams
2023, 53(5): 41-47,6.
doi: 10.13204/j.gyjzG21043002
Abstract:
In order to study the seismic behavior of steel-concrete composite asymmetric friction connection (SCCAFC), cyclic loading tests of seven groups of SCCAFC were carried out considering bolt diameter, bolt preload, friction gasket material. The test results showed that the hysteresis curves of each group of specimens were full, the double slip platform was obvious, and the expected asymmetric friction energy dissipation characteristics were achieved. With the increase of bolt preload and bolt diameter, the bearing capacity, stiffness and energy consumption of the specimens would be significantly increased. The stiffness degradation of specimens was obvious in the early stage of loading and tends to be gentle in the later stage. The energy dissipation coefficients Ed of each group were distributed between 1.52 and 2.55. The equivalent viscous damping ratio he under peak load of members was between 0.242 and 0.406. Among them, the bearing capacity and energy dissipation capacity of PSC-6 were the best, the effect of PSC-7 was the worst, and the data obtained by PSC-2 and PSC-6 had little difference. Wear-resistant steel with low cost could be used in actual project.
In order to study the seismic behavior of steel-concrete composite asymmetric friction connection (SCCAFC), cyclic loading tests of seven groups of SCCAFC were carried out considering bolt diameter, bolt preload, friction gasket material. The test results showed that the hysteresis curves of each group of specimens were full, the double slip platform was obvious, and the expected asymmetric friction energy dissipation characteristics were achieved. With the increase of bolt preload and bolt diameter, the bearing capacity, stiffness and energy consumption of the specimens would be significantly increased. The stiffness degradation of specimens was obvious in the early stage of loading and tends to be gentle in the later stage. The energy dissipation coefficients Ed of each group were distributed between 1.52 and 2.55. The equivalent viscous damping ratio he under peak load of members was between 0.242 and 0.406. Among them, the bearing capacity and energy dissipation capacity of PSC-6 were the best, the effect of PSC-7 was the worst, and the data obtained by PSC-2 and PSC-6 had little difference. Wear-resistant steel with low cost could be used in actual project.
2023, 53(5): 48-56,143.
doi: 10.13204/j.gyjzG22082506
Abstract:
To improve the cracking problem in the negative bending moment zone of composite beams, a new structure of UHPC narrow steel box composite beams was proposed. Ultra high performance concrete material (UHPC) was used to partially replace ordinary concrete (NC) in the wing plate, and its mechanical performance was studied. Two UHPC narrow steel box composite beams with different reinforcement ratios and one NC narrow steel box composite beam specimen were designed, and the full process static loading test was conducted using reverse loading method. Research had shown that as the reinforcement ratio of the experimental beam increased, the cracking load, yield load, and stiffness of the composite beam all significantly increased; the relative slip between NC interfaces in the wing plate of ordinary concrete composite beams was more significant compared to the interface slip between NC UHPC layers in the wing plate of UHPC composite beams; the use of UHPC material in the wing plate could significantly increase the cracking load of the beam and effectively improve the cracking problem in the negative bending moment zone of the composite beam. A calculation method for bending moment and ultimate bearing capacity in the elastic stage was proposed, which was in good agreement with the experimental values; nonlinear simulation analysis was conducted on three experimental beams using ABAQUS software, and the simulated values were found to be in good agreement with the experimental values.
To improve the cracking problem in the negative bending moment zone of composite beams, a new structure of UHPC narrow steel box composite beams was proposed. Ultra high performance concrete material (UHPC) was used to partially replace ordinary concrete (NC) in the wing plate, and its mechanical performance was studied. Two UHPC narrow steel box composite beams with different reinforcement ratios and one NC narrow steel box composite beam specimen were designed, and the full process static loading test was conducted using reverse loading method. Research had shown that as the reinforcement ratio of the experimental beam increased, the cracking load, yield load, and stiffness of the composite beam all significantly increased; the relative slip between NC interfaces in the wing plate of ordinary concrete composite beams was more significant compared to the interface slip between NC UHPC layers in the wing plate of UHPC composite beams; the use of UHPC material in the wing plate could significantly increase the cracking load of the beam and effectively improve the cracking problem in the negative bending moment zone of the composite beam. A calculation method for bending moment and ultimate bearing capacity in the elastic stage was proposed, which was in good agreement with the experimental values; nonlinear simulation analysis was conducted on three experimental beams using ABAQUS software, and the simulated values were found to be in good agreement with the experimental values.
2023, 53(5): 57-64,157.
doi: 10.13204/j.gyjzG22112904
Abstract:
Aiming at improving the utilization effect and quality of radiant heat in residential buildings, applying orthogonal experiment and sensitivity analysis, the technical working idea of "performance feedback cycle" was adopted in the Designbuilder software model to refine and compare the energy consumption sensitive factors in design elements controllable by architects such as plane layout, facade window wall ratio and enclosure structure . Under the condition of abundant solar radiation resources, the performance-based design method of residential energy conservation convenient for architects was explored. the technical process of building energy conservation was transformed into a specific design method, and the mutual feed relationship between energy consumption simulation calculation and scheme design was established. The research showed that in solar energy rich areas, a reasonable combination of energy consumption sensitive factors could reduce residential energy consumption by more than 30%, which had good energy-saving potential.
Aiming at improving the utilization effect and quality of radiant heat in residential buildings, applying orthogonal experiment and sensitivity analysis, the technical working idea of "performance feedback cycle" was adopted in the Designbuilder software model to refine and compare the energy consumption sensitive factors in design elements controllable by architects such as plane layout, facade window wall ratio and enclosure structure . Under the condition of abundant solar radiation resources, the performance-based design method of residential energy conservation convenient for architects was explored. the technical process of building energy conservation was transformed into a specific design method, and the mutual feed relationship between energy consumption simulation calculation and scheme design was established. The research showed that in solar energy rich areas, a reasonable combination of energy consumption sensitive factors could reduce residential energy consumption by more than 30%, which had good energy-saving potential.
2023, 53(5): 65-72.
doi: 10.13204/j.gyjzG22013001
Abstract:
In the Ming and Qing Dynasties, the Xijiang river basin was far away from the political center of the central plains, but it had an important strategic position. Since the Ming Dynasty, a large number of military defensive settlements were built, which not only had the commonness in line with the defense principles, but also had characters of local settlements closely related to the water system in southwest China. The types of settlements were studied by the typology and comparative methods, and the two types of site-location directions of settlements, simultaneously the five aspects of settlement forms were discussed. Finally, the defensive strategies at five levels of military defensive settlements in the Xijiang river basin were summarized. Numerous military defensive settlements in the Xijiang river basin reflected a multi-level and multi-directional defensive strategy from the site selection to the settlement form. Each settlement guarding the key joints of amphibious network systems. According to differently congenital and acquired environments and conditions, using multi-level defensive strategies comprenensively and combining the pringiples of enclosures, mazes, agglomeration, and etc at the macro level with military derensive facilities at the micro level including city walls, city gates, moats, enclosures for defence outside a city gate, barbettes, blockhouse, lookouts, shooting holes, and etc, and a rich and colorful, distinctive settlement defense form was established, which had a stronger disaster-prevention capability.
In the Ming and Qing Dynasties, the Xijiang river basin was far away from the political center of the central plains, but it had an important strategic position. Since the Ming Dynasty, a large number of military defensive settlements were built, which not only had the commonness in line with the defense principles, but also had characters of local settlements closely related to the water system in southwest China. The types of settlements were studied by the typology and comparative methods, and the two types of site-location directions of settlements, simultaneously the five aspects of settlement forms were discussed. Finally, the defensive strategies at five levels of military defensive settlements in the Xijiang river basin were summarized. Numerous military defensive settlements in the Xijiang river basin reflected a multi-level and multi-directional defensive strategy from the site selection to the settlement form. Each settlement guarding the key joints of amphibious network systems. According to differently congenital and acquired environments and conditions, using multi-level defensive strategies comprenensively and combining the pringiples of enclosures, mazes, agglomeration, and etc at the macro level with military derensive facilities at the micro level including city walls, city gates, moats, enclosures for defence outside a city gate, barbettes, blockhouse, lookouts, shooting holes, and etc, and a rich and colorful, distinctive settlement defense form was established, which had a stronger disaster-prevention capability.
2023, 53(5): 73-79,87.
doi: 10.13204/j.gyjzG21110407
Abstract:
The research focuses on the 14 Tibetan settlements currently selected as famous historical and cultural villages and towns in China. The field survey and geographic information data are visually expressed, and the data is integrated and calculated through statistical tools in ArcGIS. Using quantitative methods based on fractal theory and domain segmentation theory, from the two levels of the individual and the whole of the plaque, the order and organization characteristics of the traditional Tibetan settlement architectural plaque are explored respectively, which has positive significance for promoting the new urbanization construction of Tibetan villages and towns and the healthy development of rural revitalization strategies in the future. On the scale of a single plaque, the smaller the settlement scale of the Tibetan historical and cultural villages and towns, the simpler the plane of the building plaque, and the pattern is mostly simple rectangle; on the contrary, the plane of the plaque is more diversified. On the overall level of plaque, the Tibetan settlement building plaque are distributed in clusters as a whole. On the whole, the smaller the average nearest neighbor distance, the more compact the cluster distribution structure, the higher the building plaque density index, and the higher the building plaque fragmentation. Religious culture in the region has a profound impact on both. The more declining settlements are affected by religious culture, the smaller the size of the settlements. The order of building plaque tends to weaken, the randomness of the plaque tends to be greater, and the shape characteristics of the plaque tend to be simpler. Based on the common religious beliefs and ethnic culture of the Tibetan community, Tibetan historical and cultural villages and towns have similar characteristics.
The research focuses on the 14 Tibetan settlements currently selected as famous historical and cultural villages and towns in China. The field survey and geographic information data are visually expressed, and the data is integrated and calculated through statistical tools in ArcGIS. Using quantitative methods based on fractal theory and domain segmentation theory, from the two levels of the individual and the whole of the plaque, the order and organization characteristics of the traditional Tibetan settlement architectural plaque are explored respectively, which has positive significance for promoting the new urbanization construction of Tibetan villages and towns and the healthy development of rural revitalization strategies in the future. On the scale of a single plaque, the smaller the settlement scale of the Tibetan historical and cultural villages and towns, the simpler the plane of the building plaque, and the pattern is mostly simple rectangle; on the contrary, the plane of the plaque is more diversified. On the overall level of plaque, the Tibetan settlement building plaque are distributed in clusters as a whole. On the whole, the smaller the average nearest neighbor distance, the more compact the cluster distribution structure, the higher the building plaque density index, and the higher the building plaque fragmentation. Religious culture in the region has a profound impact on both. The more declining settlements are affected by religious culture, the smaller the size of the settlements. The order of building plaque tends to weaken, the randomness of the plaque tends to be greater, and the shape characteristics of the plaque tend to be simpler. Based on the common religious beliefs and ethnic culture of the Tibetan community, Tibetan historical and cultural villages and towns have similar characteristics.
2023, 53(5): 80-87.
doi: 10.13204/j.gyjzG22070115
Abstract:
In order to improve the seismic performance of small span height ratio coupling beams, quasi-static tests were carried out on three hybrid fiber concrete coupling beams and one ordinary concrete coupling beam. The failure modes, hysteresic properties, shear capacity and ductility of the coupling beams were analyzed. The effects of the matrix material and section width of the coupling beams on the seismic performance and shear capacity of the coupling beams were studied. The test results showed that hybrid fiber concrete was beneficial to the development of multiple cracks of the coupling beams, and all the three hybrid fiber concrete coupling beams showed flexural shear failure. The shear capacity and displacement ductility of hybrid fiber reinforced concrete beams with the same span-height ratio and reinforcement are 53.66% and 29.31% higher than those of ordinary concrete beams, respectively. At the same time, the finite element analysis software ABAQUS was used to investigate the influence of span-height ratio and stirrup spacing on the shear capacity of hybrid fiber reinforced concrete beams. On this basis, based on the idea of sub-item superposition, a formula for calculating the shear capacity of hybrid fiber reinforced concrete beam was established, which also considered the contributions of concrete, longitudinal reinforcement, stirrup and fiber. The calculated results were in good agreement with the experimental results, which could provide a reference for the design of this kind of member and the research in related fields.
In order to improve the seismic performance of small span height ratio coupling beams, quasi-static tests were carried out on three hybrid fiber concrete coupling beams and one ordinary concrete coupling beam. The failure modes, hysteresic properties, shear capacity and ductility of the coupling beams were analyzed. The effects of the matrix material and section width of the coupling beams on the seismic performance and shear capacity of the coupling beams were studied. The test results showed that hybrid fiber concrete was beneficial to the development of multiple cracks of the coupling beams, and all the three hybrid fiber concrete coupling beams showed flexural shear failure. The shear capacity and displacement ductility of hybrid fiber reinforced concrete beams with the same span-height ratio and reinforcement are 53.66% and 29.31% higher than those of ordinary concrete beams, respectively. At the same time, the finite element analysis software ABAQUS was used to investigate the influence of span-height ratio and stirrup spacing on the shear capacity of hybrid fiber reinforced concrete beams. On this basis, based on the idea of sub-item superposition, a formula for calculating the shear capacity of hybrid fiber reinforced concrete beam was established, which also considered the contributions of concrete, longitudinal reinforcement, stirrup and fiber. The calculated results were in good agreement with the experimental results, which could provide a reference for the design of this kind of member and the research in related fields.
2023, 53(5): 88-94.
doi: 10.13204/j.gyjzG22081819
Abstract:
A novel spatial grid model with diagonal beam elements is proposed to analyze the spatial mechanical behaviors of concrete box-section girders at the elastic linear state. The establishment of the model is based on an optimization problem: the objective functions are the absolute relative differences between the deformations from the proposed model and the actual plate under three basic types of loads including in-plane axial compression, in-plane shear, and out-of-plane bending; the variable parameters of the functions are the properties of vertical and horizontal beam and diagonal beam elements in the proposed model; the objective for the optimization is to minimize the objective functions. By solving the optimization problem, the spatial grid model with diagonal beam elements based on the optimization of spatial mechanical behaviors is established. The validity of the proposed model is illustrated with a cantilever beam under a concentrated load and a simply supported box-section girder with uniform loads as case examples. The results show that the spatial grid model with diagonal beam elements is not limited by the plane section hypothesis and is capable of accurately predicting the bending stiffness and in-plane shear stiffness. The results also reveal that the proposed model can yield deformation results consistent with the solution based on the mechanics of materials considering shear deformations and with the results from solid element models.
A novel spatial grid model with diagonal beam elements is proposed to analyze the spatial mechanical behaviors of concrete box-section girders at the elastic linear state. The establishment of the model is based on an optimization problem: the objective functions are the absolute relative differences between the deformations from the proposed model and the actual plate under three basic types of loads including in-plane axial compression, in-plane shear, and out-of-plane bending; the variable parameters of the functions are the properties of vertical and horizontal beam and diagonal beam elements in the proposed model; the objective for the optimization is to minimize the objective functions. By solving the optimization problem, the spatial grid model with diagonal beam elements based on the optimization of spatial mechanical behaviors is established. The validity of the proposed model is illustrated with a cantilever beam under a concentrated load and a simply supported box-section girder with uniform loads as case examples. The results show that the spatial grid model with diagonal beam elements is not limited by the plane section hypothesis and is capable of accurately predicting the bending stiffness and in-plane shear stiffness. The results also reveal that the proposed model can yield deformation results consistent with the solution based on the mechanics of materials considering shear deformations and with the results from solid element models.
2023, 53(5): 95-100.
doi: 10.13204/j.gyjzG23022114
Abstract:
A prefabricated concrete grid composite wall structure has been developed to address the need for energy-efficient and easy-to-install construction methods for low-rise ultra-low-energy houses in villages and towns. The optimized hexagonal opening grid composite wall, strip sandwich insulation floor, bolted rabbet joints, and connection modes between components are proposed. Through numerical simulation of wall components, the force transfer characteristics and failure modes of the grid composite wall structure and connection joints are studied. In order to improve computational efficiency, a simplified model of the grid composite wall based on shell elements is proposed. In the model, the grid wall is simplified into a homogeneous shell element wall without openings, and the bolts are also simplified non substantively. Parameter analysis has shown that filling the hexagonal openings of the grid wall with thermal insulation materials can achieve the objectives of light weight, material efficiency, cost-effectiveness, and environmental friendliness, while also meeting the bearing capacity requirements of low-rise residential structures in villages and towns. The structural system provides a new option for constructing houses in rural areas.
A prefabricated concrete grid composite wall structure has been developed to address the need for energy-efficient and easy-to-install construction methods for low-rise ultra-low-energy houses in villages and towns. The optimized hexagonal opening grid composite wall, strip sandwich insulation floor, bolted rabbet joints, and connection modes between components are proposed. Through numerical simulation of wall components, the force transfer characteristics and failure modes of the grid composite wall structure and connection joints are studied. In order to improve computational efficiency, a simplified model of the grid composite wall based on shell elements is proposed. In the model, the grid wall is simplified into a homogeneous shell element wall without openings, and the bolts are also simplified non substantively. Parameter analysis has shown that filling the hexagonal openings of the grid wall with thermal insulation materials can achieve the objectives of light weight, material efficiency, cost-effectiveness, and environmental friendliness, while also meeting the bearing capacity requirements of low-rise residential structures in villages and towns. The structural system provides a new option for constructing houses in rural areas.
2023, 53(5): 101-108.
doi: 10.13204/j.gyjzG21122104
Abstract:
The steel frame structure with lateral resistance energy-consuming device (LRED-SF) is first introduced. The finite element model of the earthquake-resilient prefabricated column foot joints with lateral resistance energy-consuming device was established and its correctness was verified. And then the finite element model of LRED-SF was established. Based on the incremental dynamic analysis method (IDA), the seismic fragility analysis with 22 seismic waves was carried out on the rigid steel frame (RSF) and LRED-SF. The seismic fragility curves and the structural collapse margin ratio (CMR) of the two structures were compared. The influence of the width and thickness of the lateral resistance shear member (LRSM) and the stiffness ratio of the beam of LRSM on the seismic fragility of LRED-SF was analyzed. The result showes that the seismic performance of LRED-SF is better than RSF. The structural collapse resistance is positively related to the width of LRSM and the stiffness ratio of the beam of LRSM. However, when the width of LRSM increases to a certain extent, the collapse resistance of the structure will decrease.
The steel frame structure with lateral resistance energy-consuming device (LRED-SF) is first introduced. The finite element model of the earthquake-resilient prefabricated column foot joints with lateral resistance energy-consuming device was established and its correctness was verified. And then the finite element model of LRED-SF was established. Based on the incremental dynamic analysis method (IDA), the seismic fragility analysis with 22 seismic waves was carried out on the rigid steel frame (RSF) and LRED-SF. The seismic fragility curves and the structural collapse margin ratio (CMR) of the two structures were compared. The influence of the width and thickness of the lateral resistance shear member (LRSM) and the stiffness ratio of the beam of LRSM on the seismic fragility of LRED-SF was analyzed. The result showes that the seismic performance of LRED-SF is better than RSF. The structural collapse resistance is positively related to the width of LRSM and the stiffness ratio of the beam of LRSM. However, when the width of LRSM increases to a certain extent, the collapse resistance of the structure will decrease.
2023, 53(5): 109-117.
doi: 10.13204/j.gyjzG22011501
Abstract:
The effects of the aluminum friction plate opening form and bolt preload on the mechanical properties of the new friction energy dissipation connection joints were studied to provide reference for the design and engineering application of PC (precast concrete) external wall panel joints. To obtain the mechanical properties of the new friction energy dissipation connection joints between PC external wall panels and frames, four sets of typical test specimens were selected for the proposed static loading test; during the loading test, it was observed that the long round-hole aluminum friction plate slid with the increase of the horizontal displacement of the central steel plate. The friction plate slides with the increase of the horizontal displacement of the central steel plate, and no obvious sliding phenomenon for the round-hole aluminium friction plate; after the loading, obvious wear was observed on the surface of the aluminium friction plate, and the long round-hole aluminium friction plate was extruded by 4.5 mm relatively, while the relative position of the round-hole aluminium friction plate remains unchanged; for the joint with the round-hole aluminium friction plate, with the increase of the preload force, the critical friction coefficient, and the relative slip at the joint decreased. The new type of friction energy dissipation connection joint with the single round-hole aluminum friction plate had better comprehensive performance. Although the friction coefficient and the average friction coefficient were not constant during the loading process, the overall energy dissipation performance did not deteriorate, indicating that the type of friction dissipation joint has good energy dissipation performance.
The effects of the aluminum friction plate opening form and bolt preload on the mechanical properties of the new friction energy dissipation connection joints were studied to provide reference for the design and engineering application of PC (precast concrete) external wall panel joints. To obtain the mechanical properties of the new friction energy dissipation connection joints between PC external wall panels and frames, four sets of typical test specimens were selected for the proposed static loading test; during the loading test, it was observed that the long round-hole aluminum friction plate slid with the increase of the horizontal displacement of the central steel plate. The friction plate slides with the increase of the horizontal displacement of the central steel plate, and no obvious sliding phenomenon for the round-hole aluminium friction plate; after the loading, obvious wear was observed on the surface of the aluminium friction plate, and the long round-hole aluminium friction plate was extruded by 4.5 mm relatively, while the relative position of the round-hole aluminium friction plate remains unchanged; for the joint with the round-hole aluminium friction plate, with the increase of the preload force, the critical friction coefficient, and the relative slip at the joint decreased. The new type of friction energy dissipation connection joint with the single round-hole aluminum friction plate had better comprehensive performance. Although the friction coefficient and the average friction coefficient were not constant during the loading process, the overall energy dissipation performance did not deteriorate, indicating that the type of friction dissipation joint has good energy dissipation performance.
2023, 53(5): 118-123.
doi: 10.13204/j.gyjzG20060803
Abstract:
In order to improve the fatigue performance of rib-to-diaphragm joint, two types of novel rib-to-diaphragm joints in OSD were proposed. For the novel welded joints, the floor of rib and diaphragm are connected by welding to enhance the cooperative working performance. The rib-to-diaphragm joints were taken as the research object, and its fatigue performance were studied systematically. The results indicate that the predominant crack pattern of the conventional rib-to-diaphragm joint is cracking initiated from the rib toe that propagated through the web plane of rib, and the stress state of cracking pattern Ⅰ is mainly in the tensile state. The predominant crack pattern of the two novel welded joints are mainly in the compressive state, and the novel welded joint 1 is the most reasonable one among the three types of novel welded joints. The predominant crack pattern of the novel welded joint 1 is cracking initiated from the rib toe that propagated through the floor plane of rib. Compared with the conventional rib-to-diaphragm joint, the stress range of the novel welded joint 1 is reduced by 12.4%, and the fatigue performance is effectively improved.
In order to improve the fatigue performance of rib-to-diaphragm joint, two types of novel rib-to-diaphragm joints in OSD were proposed. For the novel welded joints, the floor of rib and diaphragm are connected by welding to enhance the cooperative working performance. The rib-to-diaphragm joints were taken as the research object, and its fatigue performance were studied systematically. The results indicate that the predominant crack pattern of the conventional rib-to-diaphragm joint is cracking initiated from the rib toe that propagated through the web plane of rib, and the stress state of cracking pattern Ⅰ is mainly in the tensile state. The predominant crack pattern of the two novel welded joints are mainly in the compressive state, and the novel welded joint 1 is the most reasonable one among the three types of novel welded joints. The predominant crack pattern of the novel welded joint 1 is cracking initiated from the rib toe that propagated through the floor plane of rib. Compared with the conventional rib-to-diaphragm joint, the stress range of the novel welded joint 1 is reduced by 12.4%, and the fatigue performance is effectively improved.
2023, 53(5): 124-131.
doi: 10.13204/j.gyjzG22070208
Abstract:
To study the influence of recycled coarse aggregate (RCA) on the long-term performance of two-span continuous steel-concrete composite beams, a nonlinear finite element model (FEM) was established based on ABAQUS software, considering the combined effects of concrete shrinkage and creep. The reliability of the simulation was verified by three group long-term test results of two-span continuous steel-concrete composite beams. Further, the parameters of two-span continuous steel-recycled concrete composite beams were analyzed, and the influence of each parameter on their long-term performance was quantified. The results showed that the maximum difference in the mid-span deflection of two-span composite beams between the FE results and the experimental results was 11.7%,and a 3.77% difference between the FE results of the negative bending moment of the middle bearing and the experimental results was obtained. The results show that when the RCA replacement ratio is 50% and 100%, the long-term deflection of the two-span continuous steel-concrete composite beam increases by 5.52%~9.72% and 12.98%~20.39%. When the specimens using reinforced concrete slab (under the influence of uniform shrinkage and creep) are replaced with open-end and closed-end composite slab (under the influence of non-uniform shrinkage and creep), the ratio of long-term deflection to instantaneous deflection is reduced by 8.04%~19.56%. Different shrinkage creep model should be selected for different floor slab types.
To study the influence of recycled coarse aggregate (RCA) on the long-term performance of two-span continuous steel-concrete composite beams, a nonlinear finite element model (FEM) was established based on ABAQUS software, considering the combined effects of concrete shrinkage and creep. The reliability of the simulation was verified by three group long-term test results of two-span continuous steel-concrete composite beams. Further, the parameters of two-span continuous steel-recycled concrete composite beams were analyzed, and the influence of each parameter on their long-term performance was quantified. The results showed that the maximum difference in the mid-span deflection of two-span composite beams between the FE results and the experimental results was 11.7%,and a 3.77% difference between the FE results of the negative bending moment of the middle bearing and the experimental results was obtained. The results show that when the RCA replacement ratio is 50% and 100%, the long-term deflection of the two-span continuous steel-concrete composite beam increases by 5.52%~9.72% and 12.98%~20.39%. When the specimens using reinforced concrete slab (under the influence of uniform shrinkage and creep) are replaced with open-end and closed-end composite slab (under the influence of non-uniform shrinkage and creep), the ratio of long-term deflection to instantaneous deflection is reduced by 8.04%~19.56%. Different shrinkage creep model should be selected for different floor slab types.
2023, 53(5): 137-143.
doi: 10.13204/j.gyjzG22032005
Abstract:
Granite laterite is a regional special soil which is widely distributed in South China. The content of iron oxide is an important factor influencing the cementation characteristics of granite laterite. The study on the infulence of free iron oxide content on the cementation strength is of great significance. Taking classic granite laterite in Guangzhou as a research object, the hydrochloric acid osmotic method was used to remove iron oxide from typical granite laterite. Shear tests and content analysis of soil specimens before and after leaching were conducted. On the basis, the rule of soil strength before and after leaching was discussed. The results indicated that the shear peak strength of soil decreased with the decrease of the iron oxide content. By regression analysis of cementation strength and the free iron oxide content, the relation exhited obvious binomial characteristics. The cementation strength was negatively correlated with the water content, and had positive correlation with the cementation content. Taking the water content and free iron oxide content as independent variables and the cementation strength as dependent variable, the formula of cementation strength was established through binary regression analysis, which could better reflected the level of the comentation strength of the soil and had a certain application value.
Granite laterite is a regional special soil which is widely distributed in South China. The content of iron oxide is an important factor influencing the cementation characteristics of granite laterite. The study on the infulence of free iron oxide content on the cementation strength is of great significance. Taking classic granite laterite in Guangzhou as a research object, the hydrochloric acid osmotic method was used to remove iron oxide from typical granite laterite. Shear tests and content analysis of soil specimens before and after leaching were conducted. On the basis, the rule of soil strength before and after leaching was discussed. The results indicated that the shear peak strength of soil decreased with the decrease of the iron oxide content. By regression analysis of cementation strength and the free iron oxide content, the relation exhited obvious binomial characteristics. The cementation strength was negatively correlated with the water content, and had positive correlation with the cementation content. Taking the water content and free iron oxide content as independent variables and the cementation strength as dependent variable, the formula of cementation strength was established through binary regression analysis, which could better reflected the level of the comentation strength of the soil and had a certain application value.
2023, 53(5): 144-149.
doi: 10.13204/j.gyjzG22011702
Abstract:
To study the influence of the montmorillonite content and soil state on the shrinkage characteristics of expansive soil, shrinkage characteristic tests were conducted on specimens which reflected soil state (in the slurry state, after consolidation, and in compaction state). The test results indicated as the montmorillonite content increased, the shrinkage deformation of the slurry specimens gradually increased, and as the montmorillonite content in pre-consolidated specimens was in a certain range, the differences of shrinkage deformation between specimens were not much, as the montmorillonite content increased to a certain amount, the pre-consolidated specimens would produce obvious shrinkage deformation. For slurry specimens and pre-consolidated specimens, when the montmorillonite content exceeded a specific value, the curvature in the residual shrinkage stage of soil shrinkage characteristic curves (SSCC) would constantly decrease. Comparing with the shrinkage limit obtained from the graphic method, the calculated values was closer to the actual value. When the SSCC was a broken line, the calculated shrinkage limit equaled to the value by the graphic method. The influence of the montmorillonite content on the shrinkage characteristics of expansive soil was greater than that of the soil state.
To study the influence of the montmorillonite content and soil state on the shrinkage characteristics of expansive soil, shrinkage characteristic tests were conducted on specimens which reflected soil state (in the slurry state, after consolidation, and in compaction state). The test results indicated as the montmorillonite content increased, the shrinkage deformation of the slurry specimens gradually increased, and as the montmorillonite content in pre-consolidated specimens was in a certain range, the differences of shrinkage deformation between specimens were not much, as the montmorillonite content increased to a certain amount, the pre-consolidated specimens would produce obvious shrinkage deformation. For slurry specimens and pre-consolidated specimens, when the montmorillonite content exceeded a specific value, the curvature in the residual shrinkage stage of soil shrinkage characteristic curves (SSCC) would constantly decrease. Comparing with the shrinkage limit obtained from the graphic method, the calculated values was closer to the actual value. When the SSCC was a broken line, the calculated shrinkage limit equaled to the value by the graphic method. The influence of the montmorillonite content on the shrinkage characteristics of expansive soil was greater than that of the soil state.
2023, 53(5): 150-157.
doi: 10.13204/j.gyjzG22042007
Abstract:
Based on the generalized SMP strength criterion theory, combined with the non-associated flow law, the boundary conditions between the elastic-plastic interface of soil and the conservation law of soil volumes, the analytical expressions of stress fields, strain fields and pore expansion pressure in the elastic-plastic zone of spherical cavity expansion in undrained conditions were derived and applied to stratum grouting. The grouting pressure expression of analytical solutions in splitting failure of soil during grouting was obtained. The solution was compared with the theoretical solution of spherical cavity expansions in the existing literatures,simultaneously, parameter analysis was performed. Finally, comparisons between the measured values of grouting pressure by a tunnel grouting model test and theoretical values were conducted. The results indicated that cohesive force, shear expansion angles and expansion radii had great influences on splitting grouting pressure values. The actual grouting pressures were consistent with theoretical calculation values of splitting grouting.
Based on the generalized SMP strength criterion theory, combined with the non-associated flow law, the boundary conditions between the elastic-plastic interface of soil and the conservation law of soil volumes, the analytical expressions of stress fields, strain fields and pore expansion pressure in the elastic-plastic zone of spherical cavity expansion in undrained conditions were derived and applied to stratum grouting. The grouting pressure expression of analytical solutions in splitting failure of soil during grouting was obtained. The solution was compared with the theoretical solution of spherical cavity expansions in the existing literatures,simultaneously, parameter analysis was performed. Finally, comparisons between the measured values of grouting pressure by a tunnel grouting model test and theoretical values were conducted. The results indicated that cohesive force, shear expansion angles and expansion radii had great influences on splitting grouting pressure values. The actual grouting pressures were consistent with theoretical calculation values of splitting grouting.
2023, 53(5): 158-164.
doi: 10.13204/j.gyjzG22010413
Abstract:
In order to study the shear bearing capacity of prefabricated UHPC utility tunnels under static loads, the shear resistance calculation method of existing box-shape concrete structures was analyzed, and the tensile effect of steel fibers on the structure was considered, and a shear bearing capacity calculation method of prefabricated UHPC utility tunnels was proposed. Combining with the static tests under bidirectional loads on prefabricated UHPC utility tunnels, the proposed calculation formula for the shear bearing capacity was analyzed, compared and verified. The results indicated that the theoretically calculated values of the shear bearing capacity of top plates and side walls for the utility tunnel structure in destruction under confining pressure, which was considered the contribution of steel fibers in UHPC to shear resistance of structures and was referred to the "internal force arch" calculation model of box-shaped structurs, were closer to the measured values in tests. The calculated results were more accurate, and the calculation errors were within 7%. Compared with the existing calculation methods, the proposed method was more accurate.
In order to study the shear bearing capacity of prefabricated UHPC utility tunnels under static loads, the shear resistance calculation method of existing box-shape concrete structures was analyzed, and the tensile effect of steel fibers on the structure was considered, and a shear bearing capacity calculation method of prefabricated UHPC utility tunnels was proposed. Combining with the static tests under bidirectional loads on prefabricated UHPC utility tunnels, the proposed calculation formula for the shear bearing capacity was analyzed, compared and verified. The results indicated that the theoretically calculated values of the shear bearing capacity of top plates and side walls for the utility tunnel structure in destruction under confining pressure, which was considered the contribution of steel fibers in UHPC to shear resistance of structures and was referred to the "internal force arch" calculation model of box-shaped structurs, were closer to the measured values in tests. The calculated results were more accurate, and the calculation errors were within 7%. Compared with the existing calculation methods, the proposed method was more accurate.
2023, 53(5): 165-173.
doi: 10.13204/j.gyjzG20090803
Abstract:
Probabilistic analysis on the durability of the concrete structure in the marine environment of Lianyungang Wharf was carried out. A time-varying probability analysis method for predicting the service life of concrete structures was adopted. A durability evaluation model of concrete structures considering the statistical characteristics of parameters was established. Combined with the long-term field inspection data of Lianyungang Wharf and domestic and foreign references, the statistical characteristics of the model parameters were analyzed in detail. Monte Carlo simulation method was used to calculate the failure probability and reliability index of concrete structure under different exposure time. A probability analysis method was proposed that comprehensively considers Standard for Design of Concrete Structure Durability (GB/T 50476-2019), optimal reliability, and the difference in reliability indicators. The influence of concrete protective layer thickness and chloride ion diffusion coefficient on the service life of concrete structures was studied. The research results show that the concrete protective layer thickness and the chloride diffusion coefficient have an important influence on the service life of the concrete structure. In contrast, the service life of the concrete structure is more sensitive to changes of the concrete protective layer thickness.
Probabilistic analysis on the durability of the concrete structure in the marine environment of Lianyungang Wharf was carried out. A time-varying probability analysis method for predicting the service life of concrete structures was adopted. A durability evaluation model of concrete structures considering the statistical characteristics of parameters was established. Combined with the long-term field inspection data of Lianyungang Wharf and domestic and foreign references, the statistical characteristics of the model parameters were analyzed in detail. Monte Carlo simulation method was used to calculate the failure probability and reliability index of concrete structure under different exposure time. A probability analysis method was proposed that comprehensively considers Standard for Design of Concrete Structure Durability (GB/T 50476-2019), optimal reliability, and the difference in reliability indicators. The influence of concrete protective layer thickness and chloride ion diffusion coefficient on the service life of concrete structures was studied. The research results show that the concrete protective layer thickness and the chloride diffusion coefficient have an important influence on the service life of the concrete structure. In contrast, the service life of the concrete structure is more sensitive to changes of the concrete protective layer thickness.
2023, 53(5): 174-178.
doi: 10.13204/j.gyjzG22112903
Abstract:
Graphene oxide (GO) has been shown to significantly improve the mechanical properties of cement composites, and the dispersity of GO is a key factor affecting the performance enhancement of composites. In this paper, gum arabic (GA) was used as dispersant, the dispersion stability of GO in different solutions was analyzed by optical microscope, ultraviolet spectrophotometer (UV-vis) and transmission electron microscope (TEM), and cement composites were prepared. The results showed that high alkalinity and calcium ions were key factors inducing the agglomeration of GO in cement. The addition of GA could ensure the stable dispersion of GO in the cement simulated pore solution. The 28 d flexural and compressive strengths of 0.03%GO cement composites doped with GA increase by 24.85% and 42.11%, respectively. The morphological analysis showed that GO treated with GA promoted the formation of rod-like crystals inside the cement and enhanced the structural compactness. Therefore, this dispersion route could be successfully used for the preparation of GO reinforced cement composites.
Graphene oxide (GO) has been shown to significantly improve the mechanical properties of cement composites, and the dispersity of GO is a key factor affecting the performance enhancement of composites. In this paper, gum arabic (GA) was used as dispersant, the dispersion stability of GO in different solutions was analyzed by optical microscope, ultraviolet spectrophotometer (UV-vis) and transmission electron microscope (TEM), and cement composites were prepared. The results showed that high alkalinity and calcium ions were key factors inducing the agglomeration of GO in cement. The addition of GA could ensure the stable dispersion of GO in the cement simulated pore solution. The 28 d flexural and compressive strengths of 0.03%GO cement composites doped with GA increase by 24.85% and 42.11%, respectively. The morphological analysis showed that GO treated with GA promoted the formation of rod-like crystals inside the cement and enhanced the structural compactness. Therefore, this dispersion route could be successfully used for the preparation of GO reinforced cement composites.
2023, 53(5): 179-186.
doi: 10.13204/j.gyjzG22112002
Abstract:
The stainless-clad bimetallic steel bar (SCBSB) is a new type of weather-resistant steel bar composed of carbon steel core bars and stainless-steel cladding. The metallurgical combination of the two is realized through hot rolling and other processes, so that it has both the strength of the core bar and the corrosion resistance of the cladding, which has broad prospects in practical engineering applications. Taking SCBSB which is consisted with the S304 stainless steel as the cladding and the HRB400 carbon steel bar as the substrate as the research object, according to the actual service state of reinforcement, three types of corrosion are designed, that’s, uniform corrosion, damaged cladding corrosion and non-uniform corrosion. Three types of corrosion forms of SCBSB samples were obtained by electrochemical accelerated corrosion test. Then the tensile test was performed on the above samples. The research had shown that the mechanical properties of SCBSB decreased linearly due to corrosion. The characteristic of stress-strain curve also changed after three forms of corrosion, of which the disappearance of the yield platform of the damaged cladding corrosion sample occurred first. The evolution law of mechanical properties and toughness of SCBSB with three corrosion forms was quantitatively described by prediction models, which could predict the mechanical properties and toughness of SCBSB with three corrosion forms at any degree of corrosion. Finally, according to the test results and the requirements of GB/T 1499.2—2018, the paper suggested that the corrosion degree of SCBSB should be controlled below 10.7% to ensure the service performance of the structure.
The stainless-clad bimetallic steel bar (SCBSB) is a new type of weather-resistant steel bar composed of carbon steel core bars and stainless-steel cladding. The metallurgical combination of the two is realized through hot rolling and other processes, so that it has both the strength of the core bar and the corrosion resistance of the cladding, which has broad prospects in practical engineering applications. Taking SCBSB which is consisted with the S304 stainless steel as the cladding and the HRB400 carbon steel bar as the substrate as the research object, according to the actual service state of reinforcement, three types of corrosion are designed, that’s, uniform corrosion, damaged cladding corrosion and non-uniform corrosion. Three types of corrosion forms of SCBSB samples were obtained by electrochemical accelerated corrosion test. Then the tensile test was performed on the above samples. The research had shown that the mechanical properties of SCBSB decreased linearly due to corrosion. The characteristic of stress-strain curve also changed after three forms of corrosion, of which the disappearance of the yield platform of the damaged cladding corrosion sample occurred first. The evolution law of mechanical properties and toughness of SCBSB with three corrosion forms was quantitatively described by prediction models, which could predict the mechanical properties and toughness of SCBSB with three corrosion forms at any degree of corrosion. Finally, according to the test results and the requirements of GB/T 1499.2—2018, the paper suggested that the corrosion degree of SCBSB should be controlled below 10.7% to ensure the service performance of the structure.
2023, 53(5): 187-195.
doi: 10.13204/j.gyjzG23012910
Abstract:
For the problem that it is difficult to completely determine the damage location distribution of the existing latticed shell, a practical residual force decomposition (RFD) method was proposed to identify significantly damaged members in the existing latticed shell. In the proposed RFD method, the significant damage can be recognized corresponding to the changes of the observed eigenvector based on the non-dimensional modal deformation parameters defined in the paper along the axial projection direction of members, which can be transformed into solving a set of multivariate linear equations. To deal with the possibility of infinite solutions in the equation system, the sensitivity analysis of Ritz vectors and the Modal Assurance Criterion (MAC) were employed to assess the importance of members in latticed shell structures. The members with minimal contribution to the structural stiffness under the current loading condition were selected and introduced as additional constraint conditions in the calculation equations, ensuring the uniqueness of the solution to the equation system. A latticed shell structural model was established for computational analysis, and the calculation process of the RFD method in the paper was described in detail and its effectiveness was verified.
For the problem that it is difficult to completely determine the damage location distribution of the existing latticed shell, a practical residual force decomposition (RFD) method was proposed to identify significantly damaged members in the existing latticed shell. In the proposed RFD method, the significant damage can be recognized corresponding to the changes of the observed eigenvector based on the non-dimensional modal deformation parameters defined in the paper along the axial projection direction of members, which can be transformed into solving a set of multivariate linear equations. To deal with the possibility of infinite solutions in the equation system, the sensitivity analysis of Ritz vectors and the Modal Assurance Criterion (MAC) were employed to assess the importance of members in latticed shell structures. The members with minimal contribution to the structural stiffness under the current loading condition were selected and introduced as additional constraint conditions in the calculation equations, ensuring the uniqueness of the solution to the equation system. A latticed shell structural model was established for computational analysis, and the calculation process of the RFD method in the paper was described in detail and its effectiveness was verified.
