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2022 Vol. 52, No. 11
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2022, 52(11): 1-11,110.
doi: 10.13204/j.gyjzG22010302
Abstract:
Superimposed shear wall is a kind of semi-precast superimposed element composed of two precast concrete wall boards and the cast-in-place concrete in the cavity. It has the advantages of good integrity, high production efficiency and low cost, and thus has broad application prospects. Researchers at home and abroad have studied the seismic and mechanical properties of this kind of structure systematically. Some modifications have also been made, and a variety of superimposed shear walls with new construction manners, new materials and new connectors have been proposed and studied. Except for above-ground building structures, superimposed walls have also been applied in underground structures with high requirements for waterproof performance, such as basement exterior walls, underground comprehensive pipe galleries and subway stations, etc. The state of the art of research on the various superimposed walls in different application fields was reviewed.
Superimposed shear wall is a kind of semi-precast superimposed element composed of two precast concrete wall boards and the cast-in-place concrete in the cavity. It has the advantages of good integrity, high production efficiency and low cost, and thus has broad application prospects. Researchers at home and abroad have studied the seismic and mechanical properties of this kind of structure systematically. Some modifications have also been made, and a variety of superimposed shear walls with new construction manners, new materials and new connectors have been proposed and studied. Except for above-ground building structures, superimposed walls have also been applied in underground structures with high requirements for waterproof performance, such as basement exterior walls, underground comprehensive pipe galleries and subway stations, etc. The state of the art of research on the various superimposed walls in different application fields was reviewed.
2022, 52(11): 12-18,90.
doi: 10.13204/j.gyjzG21012705
Abstract:
To study the seismic performance of the precast shear wall with bolt connections at the horizontal joint, a quasi-static test of two shear wall specimens with a shear-span ratio of 2.2 was conducted. The test results showed that: both specimens suffered bending damage, and the shear capacity of the horizontal joint met the requirements; the damage of both specimens occurred near the horizontal joint and the lower section of the wall panel below the joint, while the upper wall panel basically remained elastic; due to the different forms of the bottom plate of the connection box, brittle damage occurred in specimen S-1 while plastic damage occurred in specimen S-2; the ductility coefficient of specimen S-2 was between 3.03 and 3.7, and the drift value could meet the requirements of Chinese Code for Seismic Design of Buildings(GB 50011—2010). Based on the experimental study, the unidirectional push over analysis based on FE software ABAQUS was conducted the analysis. The proposed FE model could well reproduce the skeleton curve and the failure mode of the specimens.
To study the seismic performance of the precast shear wall with bolt connections at the horizontal joint, a quasi-static test of two shear wall specimens with a shear-span ratio of 2.2 was conducted. The test results showed that: both specimens suffered bending damage, and the shear capacity of the horizontal joint met the requirements; the damage of both specimens occurred near the horizontal joint and the lower section of the wall panel below the joint, while the upper wall panel basically remained elastic; due to the different forms of the bottom plate of the connection box, brittle damage occurred in specimen S-1 while plastic damage occurred in specimen S-2; the ductility coefficient of specimen S-2 was between 3.03 and 3.7, and the drift value could meet the requirements of Chinese Code for Seismic Design of Buildings(GB 50011—2010). Based on the experimental study, the unidirectional push over analysis based on FE software ABAQUS was conducted the analysis. The proposed FE model could well reproduce the skeleton curve and the failure mode of the specimens.
2022, 52(11): 19-23,38.
doi: 10.13204/j.gyjzG22052204
Abstract:
Corrugated steel plate shear wall (CSPSW) is a novel lateral force resisting system which has been widely applied in high-rise buildings. An ABAQUS finite element (FE) model of CSPSW was established, and the accuracy of the FE method was verified according to existing test results. Based on the FE model, a parameter analysis was conducted and the effect of corrugation parameters on shear capacity of CSPSW was investigated, including the correlation between the wave length, wave height, wave angle and performance indexes, such as ultimate shear capacity, residual bearing capacity and post-buckling ductility of the wall. Based on the results of parametric analysis, a design method for shear capacity of CSPSW with different waveform parameters was proposed. The results showed that the increase of wave length, wave height and wave angle could improve the ultimate shear capacity, and the increase of wave height had the most significant effect. The change of wave length and wave height could had a certain effect on the ductility of wall, but the change of wave angle had negligible effect. The proposed design formula has certain reliability and can be used to safely calculate the ultimate shear bearing capacity of CSPSW.
Corrugated steel plate shear wall (CSPSW) is a novel lateral force resisting system which has been widely applied in high-rise buildings. An ABAQUS finite element (FE) model of CSPSW was established, and the accuracy of the FE method was verified according to existing test results. Based on the FE model, a parameter analysis was conducted and the effect of corrugation parameters on shear capacity of CSPSW was investigated, including the correlation between the wave length, wave height, wave angle and performance indexes, such as ultimate shear capacity, residual bearing capacity and post-buckling ductility of the wall. Based on the results of parametric analysis, a design method for shear capacity of CSPSW with different waveform parameters was proposed. The results showed that the increase of wave length, wave height and wave angle could improve the ultimate shear capacity, and the increase of wave height had the most significant effect. The change of wave length and wave height could had a certain effect on the ductility of wall, but the change of wave angle had negligible effect. The proposed design formula has certain reliability and can be used to safely calculate the ultimate shear bearing capacity of CSPSW.
2022, 52(11): 24-31,103.
doi: 10.13204/j.gyjzG21122105
Abstract:
Corrugated steel plate shear wall is a new type of steel plate shear wall. Its mechanical properties is better than ordinary steel plate wall and saves more steel. The existing research on the influence of the connection mode between corrugated steel plate wall and beam-column components on the hysteretic behavior of corrugated steel plate wall is not enough. In order to further analyze the factors affecting the hysteretic behavior of corrugated steel plate wall, the variable parameter analysis of corrugated steel plate shear wall with horizontal waveform and vertical waveform was carried out. The parameters such as connection mode with upper and lower beams, axial compression ratio and waveform shape were mainly changed. The quasi-static analysis of 13 examples of corrugated steel plate shear wall and flat steel plate shear wall with different parameters was carried out through ABAQUS finite element analysis software, and the failure mode and hysteretic performance of each steel plate shear wall were obtained. The results showed that the increase of axial compression ratio had an obvious adverse effect on the hysteretic behavior of corrugated steel plate wall with horizontal waveform, but had little effect on corrugated steel plate wall; The bearing capacity of corrugated steel plate wall increased obviously after increasing the wave amplitude. Reducing the wavelength or increasing the wave amplitude would cause different degrees of out-of-plane deformation of corrugated steel plate wall with horizontal waveform; after the wall panel was disconnected from the upper and lower beams, the bearing capacity of the corrugated steel plate wall with vertical waveform was seriously lost, while the energy consumption capacity of the corrugated steel plate wall with horizontal waveform was significantly improved.
Corrugated steel plate shear wall is a new type of steel plate shear wall. Its mechanical properties is better than ordinary steel plate wall and saves more steel. The existing research on the influence of the connection mode between corrugated steel plate wall and beam-column components on the hysteretic behavior of corrugated steel plate wall is not enough. In order to further analyze the factors affecting the hysteretic behavior of corrugated steel plate wall, the variable parameter analysis of corrugated steel plate shear wall with horizontal waveform and vertical waveform was carried out. The parameters such as connection mode with upper and lower beams, axial compression ratio and waveform shape were mainly changed. The quasi-static analysis of 13 examples of corrugated steel plate shear wall and flat steel plate shear wall with different parameters was carried out through ABAQUS finite element analysis software, and the failure mode and hysteretic performance of each steel plate shear wall were obtained. The results showed that the increase of axial compression ratio had an obvious adverse effect on the hysteretic behavior of corrugated steel plate wall with horizontal waveform, but had little effect on corrugated steel plate wall; The bearing capacity of corrugated steel plate wall increased obviously after increasing the wave amplitude. Reducing the wavelength or increasing the wave amplitude would cause different degrees of out-of-plane deformation of corrugated steel plate wall with horizontal waveform; after the wall panel was disconnected from the upper and lower beams, the bearing capacity of the corrugated steel plate wall with vertical waveform was seriously lost, while the energy consumption capacity of the corrugated steel plate wall with horizontal waveform was significantly improved.
2022, 52(11): 32-38.
doi: 10.13204/j.gyjzG21081212
Abstract:
In order to study the hysteretic perfomance of grid-tube double steel plate composite shear wall under strong earthquake, the ABAQUS finite element model considering plastic damage of concrete and ductile damage of steel plate in grid-tube double steel plate composite shear wall was established. And the hysteretic curves, skeleton curves and failure modes of the structure under horizontal reciprocating loads were studied. Firstly, the numerical model of grid-tube double-steel-plate composite shear wall considering damage accumulation was verified by prototype test, and the computational accuracy of the model was evaluated from hysteretic curves and skeleton curves. Then, the axial compression ratio and shear-span ratio were analyzed. It could provide a reference for the engineering application of grid-tube double steel plate composite shear walls.
In order to study the hysteretic perfomance of grid-tube double steel plate composite shear wall under strong earthquake, the ABAQUS finite element model considering plastic damage of concrete and ductile damage of steel plate in grid-tube double steel plate composite shear wall was established. And the hysteretic curves, skeleton curves and failure modes of the structure under horizontal reciprocating loads were studied. Firstly, the numerical model of grid-tube double-steel-plate composite shear wall considering damage accumulation was verified by prototype test, and the computational accuracy of the model was evaluated from hysteretic curves and skeleton curves. Then, the axial compression ratio and shear-span ratio were analyzed. It could provide a reference for the engineering application of grid-tube double steel plate composite shear walls.
2022, 52(11): 39-48.
doi: 10.13204/j.gyjzG22040401
Abstract:
Steel reinforced concrete shear wall has the advantages of good seismic performance and easy assembly. The seismic performance of the joint between the wall and steel coupling beam seriously affects the safety of the structural system. In order to investigate the seismic performance of different types of joints, ABAQUS finite element software was used to establish a refined model to analyze the seismic performance of shear plastic deformation dominated joints and bending plastic deformation dominated joints. Through quasi-static loading, the failure mode of the joint was observed, and the parameters such as hysteretic performance, skeleton curve, stiffness degradation curve, equivalent viscous damping coefficient and displacement ductility coefficient of the joint were analyzed. The influence of axillary beam, side rib plate, diagonal brace and flange weakening on the seismic performance of the joint was investigated. The research showed that increasing the axil beam or side rib plate could improve the initial stiffness and bearing capacity of the joint, move the plastic hinge outward, reduce the deformation of the side column, and realize the seismic demand of "strong joint", but increasing the side rib plate would reduce the ductility of the joint. The weakening of the flange would reduce the initial stiffness and bearing capacity of the joint, but had little effect on the stiffness degradation. The addition of axillary beam, side rib and diagonal brace at the joint had little effect on the hysteretic curve and skeleton curve after flange weakening.
Steel reinforced concrete shear wall has the advantages of good seismic performance and easy assembly. The seismic performance of the joint between the wall and steel coupling beam seriously affects the safety of the structural system. In order to investigate the seismic performance of different types of joints, ABAQUS finite element software was used to establish a refined model to analyze the seismic performance of shear plastic deformation dominated joints and bending plastic deformation dominated joints. Through quasi-static loading, the failure mode of the joint was observed, and the parameters such as hysteretic performance, skeleton curve, stiffness degradation curve, equivalent viscous damping coefficient and displacement ductility coefficient of the joint were analyzed. The influence of axillary beam, side rib plate, diagonal brace and flange weakening on the seismic performance of the joint was investigated. The research showed that increasing the axil beam or side rib plate could improve the initial stiffness and bearing capacity of the joint, move the plastic hinge outward, reduce the deformation of the side column, and realize the seismic demand of "strong joint", but increasing the side rib plate would reduce the ductility of the joint. The weakening of the flange would reduce the initial stiffness and bearing capacity of the joint, but had little effect on the stiffness degradation. The addition of axillary beam, side rib and diagonal brace at the joint had little effect on the hysteretic curve and skeleton curve after flange weakening.
2022, 52(11): 49-56.
doi: 10.13204/j.gyjzG22062012
Abstract:
To study the seismic performance of steel plate shear wall and the deformation capacity of the outer decorative layer in the steel structure residence, four test components of the full-scaled concrete-filled square steel tubular frame-steel plate shear walls with vertical stiffeners were tested under constant vertical load and cyclic lateral loads. Through quasi-static hysteresis loading of each specimen, the influence of the outer decorative layer and vertical stiffener arrangements on the seismic performance of the steel plate shear wall was discussed. High bearing capacity, favorable energy dissipation capacity and ductility of all specimens were found even under the combined action of vertical load and horizontal repeated load. The outer decorative layer could improve the initial lateral stiffness and the energy dissipation capacity during the early stage, but speed up the degradation of the capacity in the post-peak stage. No other significant difference was found between the specimens with or without the outer decorative layer. The peak loads of specimens with equidistant arrangement of vertical stiffeners were slightly higher than that with the uneven distant arrangements of stiffeners, and the other seismic behaviors of both were almost the same. On the basis of experiments and existing literature, the classification of harmful displacement angles for steel plate shear walls with outer decorative layer was proposed.
To study the seismic performance of steel plate shear wall and the deformation capacity of the outer decorative layer in the steel structure residence, four test components of the full-scaled concrete-filled square steel tubular frame-steel plate shear walls with vertical stiffeners were tested under constant vertical load and cyclic lateral loads. Through quasi-static hysteresis loading of each specimen, the influence of the outer decorative layer and vertical stiffener arrangements on the seismic performance of the steel plate shear wall was discussed. High bearing capacity, favorable energy dissipation capacity and ductility of all specimens were found even under the combined action of vertical load and horizontal repeated load. The outer decorative layer could improve the initial lateral stiffness and the energy dissipation capacity during the early stage, but speed up the degradation of the capacity in the post-peak stage. No other significant difference was found between the specimens with or without the outer decorative layer. The peak loads of specimens with equidistant arrangement of vertical stiffeners were slightly higher than that with the uneven distant arrangements of stiffeners, and the other seismic behaviors of both were almost the same. On the basis of experiments and existing literature, the classification of harmful displacement angles for steel plate shear walls with outer decorative layer was proposed.
2022, 52(11): 57-66.
doi: 10.13204/j.gyjzG22061503
Abstract:
Enzyme induced calcium carbonate precipitation (EICP) is a green and environment-friendly new soil improvement technology in geotechnical engineering. Compared with microbial induced calcium carbonate precipitation (MICP) which has been widely concerned at present, EICP is applicable to a wider range of sand particle sizes and does not need a complex sterile culture process, and the problem of microbial ecological safety is avoided in practical application. On the basis of literature induction and sorting, the research achievements on the cementitious mechanism of enzyme induced calcium carbonate precipitation and the influencing factors (enzyme properties, cementing fluid properties, curing methods, environmental factors) were systematically described. The existing problems and further research directions in development of the enzyme induced calcium carbonate precipitation technique were discussed.
Enzyme induced calcium carbonate precipitation (EICP) is a green and environment-friendly new soil improvement technology in geotechnical engineering. Compared with microbial induced calcium carbonate precipitation (MICP) which has been widely concerned at present, EICP is applicable to a wider range of sand particle sizes and does not need a complex sterile culture process, and the problem of microbial ecological safety is avoided in practical application. On the basis of literature induction and sorting, the research achievements on the cementitious mechanism of enzyme induced calcium carbonate precipitation and the influencing factors (enzyme properties, cementing fluid properties, curing methods, environmental factors) were systematically described. The existing problems and further research directions in development of the enzyme induced calcium carbonate precipitation technique were discussed.
2022, 52(11): 67-70,66.
doi: 10.13204/j.gyjzG20110216
Abstract:
In order to study the treatment effect of Enzyme Induced Calcium Carbonate Precipitation (EICP) on Zn2+ contaminated soil, abundant urease was extracted from soybean, mineralization of heavy metal Zn2+ with substrate induction was implemented. The different forms of Zn2+ in contaminated sand before and after remediation were extracted and detected by Tessier’s five-step continuous extraction method, and the mechanical properties of different remediation times were compared through unconfined compressive strength tests. Results showed that the extracted urease had a good activity and it could effectively catalyzed the hydrolysis of urea to form carbonate ions, which could form carbonate precipitation and mineralize Zn2+ in the induction of substrate. EICP technology could effectively reduce the content of Zn2+ in contaminated sand, and fix it in the form of carbonate, moreover, the unconfined compression strength of the repaired sand increased from 0 to 0.44 MPa after repaired 3 times. EICP technology provided a new choice for the remediation of heavy metal Zn2+ contaminated soil.
In order to study the treatment effect of Enzyme Induced Calcium Carbonate Precipitation (EICP) on Zn2+ contaminated soil, abundant urease was extracted from soybean, mineralization of heavy metal Zn2+ with substrate induction was implemented. The different forms of Zn2+ in contaminated sand before and after remediation were extracted and detected by Tessier’s five-step continuous extraction method, and the mechanical properties of different remediation times were compared through unconfined compressive strength tests. Results showed that the extracted urease had a good activity and it could effectively catalyzed the hydrolysis of urea to form carbonate ions, which could form carbonate precipitation and mineralize Zn2+ in the induction of substrate. EICP technology could effectively reduce the content of Zn2+ in contaminated sand, and fix it in the form of carbonate, moreover, the unconfined compression strength of the repaired sand increased from 0 to 0.44 MPa after repaired 3 times. EICP technology provided a new choice for the remediation of heavy metal Zn2+ contaminated soil.
2022, 52(11): 71-78.
doi: 10.13204/j.gyjzG22070609
Abstract:
In order to systematically study the effect of calcium sources, cementitious solution concentrations, bacteria liquid concentrations, temperatures and pH values of microbial cementitious liquids on the resistance capacity of fugitive dust and wind erosion of construction debris cemented by microbial induced calcite precipitation (MICP), single-factor orthogonal tests cemented construction debris by MICP and wind tunnel tests were conducted, assisted by SEM and XRD microscopic methods. The test results showed that using calcium chloride as a calcium source, the concentration of the cementitious solution was 0.5 mol/L, the concentration of the bacterial liquid (OD600) was 4.0, the temperature was 20 to 40 ℃, and the resistance effect of wind erosion for construction debris cemented by MICP in the neutral or weakly alkaline environment was better. The maximum increments of the soluble salt content and the pH value in construction debris cemented by MICP were 0.92% and 0.20 respectively,and the method to cement construction debris by MICP was of the advantage of environmental friendliness.
In order to systematically study the effect of calcium sources, cementitious solution concentrations, bacteria liquid concentrations, temperatures and pH values of microbial cementitious liquids on the resistance capacity of fugitive dust and wind erosion of construction debris cemented by microbial induced calcite precipitation (MICP), single-factor orthogonal tests cemented construction debris by MICP and wind tunnel tests were conducted, assisted by SEM and XRD microscopic methods. The test results showed that using calcium chloride as a calcium source, the concentration of the cementitious solution was 0.5 mol/L, the concentration of the bacterial liquid (OD600) was 4.0, the temperature was 20 to 40 ℃, and the resistance effect of wind erosion for construction debris cemented by MICP in the neutral or weakly alkaline environment was better. The maximum increments of the soluble salt content and the pH value in construction debris cemented by MICP were 0.92% and 0.20 respectively,and the method to cement construction debris by MICP was of the advantage of environmental friendliness.
2022, 52(11): 79-83.
doi: 10.13204/j.gyjzG21022609
Abstract:
Magnesium oxide combined with microorganism was used to cement tailing sand, and a comparison between cementation effect of maguesium oxide combined with microorganism and microbial induced carbonate precipitation (MICP) was conducted. The effects of the initial moisture content (in the range of 16% to 25%) of tailing sand and the magnesium oxide content (in the range of 6% to 15%), and the initial moisture content (in the range of 16% to 25%) of tailing sand during MICP on cementation were explored by unconfined compressive strength and SEM tests. The results showed that in the process of cementation with magnesium oxide combined with microorganism, the higher the initial moisture content was, the lower the unconfined compressive strength was; and the more the magnesium oxide content was, the higher the strength was; and in MICP, with the increase of the initial moisture content, the strength of specimens first decreased and then increased, and the lowest initial moisture content was 19%.
Magnesium oxide combined with microorganism was used to cement tailing sand, and a comparison between cementation effect of maguesium oxide combined with microorganism and microbial induced carbonate precipitation (MICP) was conducted. The effects of the initial moisture content (in the range of 16% to 25%) of tailing sand and the magnesium oxide content (in the range of 6% to 15%), and the initial moisture content (in the range of 16% to 25%) of tailing sand during MICP on cementation were explored by unconfined compressive strength and SEM tests. The results showed that in the process of cementation with magnesium oxide combined with microorganism, the higher the initial moisture content was, the lower the unconfined compressive strength was; and the more the magnesium oxide content was, the higher the strength was; and in MICP, with the increase of the initial moisture content, the strength of specimens first decreased and then increased, and the lowest initial moisture content was 19%.
2022, 52(11): 84-90.
doi: 10.13204/j.gyjzG21112407
Abstract:
Aiming at the crystallization effectiveness of the microbial self-healing technology for concrete cracks, and to improve the efficiency of microbial crystallization, a new material, namely calcareous sand of coral reefs, was used to immobilize microorganisms, and the superiority of calcareous sand of coral reefs to repair cracks in concrete and crystallization effect in the practice engineering was verified was verified by means of an impermeability test. The physical and mechanical properties of calcareous sand of coral reefs were analyzed, which had a water absorption ratio of 17%, a crushing value of 26%, and the calcium carbonate content more than 97%. The study showed that calcareous sand of coral reefs was of learger porosity and specific surface areas. It was good living space and an ideal immobilized material for microorganisms. Sporosarcina pasteurii were immobilized in calcareous sand of coral reefs, and the impermeability test for self-healing concrete cracks were subsequently implemented. The study results revealed that after immobilization and self-renovation, the gas penetration decreased by 10%, the permeability coefficient decreased by 2 orders of magnitude. In addition, calcite-type calcium carbonate crystal precipitates filling in cracks by SEM scanning were observed, and microbially generated calcite calcium carbonate crystal sediments were observed by the carbon-iostope ratio determination analysis in repaired cracks in practice engineering. The study showed that the immobilization of calcareous sand of coral reefs played a good role in protecting microorganisms, which improved the efficiency of microbial crystallization and effectively ameliorated the pore characteristics and structure of concrete cracks.
Aiming at the crystallization effectiveness of the microbial self-healing technology for concrete cracks, and to improve the efficiency of microbial crystallization, a new material, namely calcareous sand of coral reefs, was used to immobilize microorganisms, and the superiority of calcareous sand of coral reefs to repair cracks in concrete and crystallization effect in the practice engineering was verified was verified by means of an impermeability test. The physical and mechanical properties of calcareous sand of coral reefs were analyzed, which had a water absorption ratio of 17%, a crushing value of 26%, and the calcium carbonate content more than 97%. The study showed that calcareous sand of coral reefs was of learger porosity and specific surface areas. It was good living space and an ideal immobilized material for microorganisms. Sporosarcina pasteurii were immobilized in calcareous sand of coral reefs, and the impermeability test for self-healing concrete cracks were subsequently implemented. The study results revealed that after immobilization and self-renovation, the gas penetration decreased by 10%, the permeability coefficient decreased by 2 orders of magnitude. In addition, calcite-type calcium carbonate crystal precipitates filling in cracks by SEM scanning were observed, and microbially generated calcite calcium carbonate crystal sediments were observed by the carbon-iostope ratio determination analysis in repaired cracks in practice engineering. The study showed that the immobilization of calcareous sand of coral reefs played a good role in protecting microorganisms, which improved the efficiency of microbial crystallization and effectively ameliorated the pore characteristics and structure of concrete cracks.
2022, 52(11): 91-96.
doi: 10.13204/j.gyjzG22071415
Abstract:
To effectively improve the stability of steel slag and promote the utilization of steel slag resources, the changes in strength, microstructure and stability before and after microbial improved steel slag were studied. The results showed that: 1) when compressive strength of original steel slag was 1.1 MPa, and the compressive strength of improved steel slag mixed with saccharomycetes, pasteurella or the mixed bacteria of the above two was 1.2 MPa, 3.1 MPa and 4.5 MPa respectively. After improvement with the mixture of the two microbes, the steel slag was of the best stability in them, and the f-CaO content was 2.86%, which met the requirements not more than 3% of GB/T 20491-2017 Steel Slag Powder Used for Cement and Concrete, but other technical indexes didn’t meet the requirments of the specification. 2) The addition of the binary microorganisms could produce CO2 either in aerobic or anaerobic conditions, and CO2 dissolved in water in an alkaline environment would produce CO2-3, which made up the lack of the mineralization capacity in the condition of less oxygen of mono-bacteria, so the steel slag modified with binary microorganisms would produce a sharper C=O absorption band and a larger area of characteristic peaks of C-S-H gel, and the CaCO3 crystals and the C-S-H gel bodies closely coverd the surface of steel slag.
To effectively improve the stability of steel slag and promote the utilization of steel slag resources, the changes in strength, microstructure and stability before and after microbial improved steel slag were studied. The results showed that: 1) when compressive strength of original steel slag was 1.1 MPa, and the compressive strength of improved steel slag mixed with saccharomycetes, pasteurella or the mixed bacteria of the above two was 1.2 MPa, 3.1 MPa and 4.5 MPa respectively. After improvement with the mixture of the two microbes, the steel slag was of the best stability in them, and the f-CaO content was 2.86%, which met the requirements not more than 3% of GB/T 20491-2017 Steel Slag Powder Used for Cement and Concrete, but other technical indexes didn’t meet the requirments of the specification. 2) The addition of the binary microorganisms could produce CO2 either in aerobic or anaerobic conditions, and CO2 dissolved in water in an alkaline environment would produce CO2-3, which made up the lack of the mineralization capacity in the condition of less oxygen of mono-bacteria, so the steel slag modified with binary microorganisms would produce a sharper C=O absorption band and a larger area of characteristic peaks of C-S-H gel, and the CaCO3 crystals and the C-S-H gel bodies closely coverd the surface of steel slag.
2022, 52(11): 97-103.
doi: 10.13204/j.gyjzG22061309
Abstract:
Several varieties of bacteria were isolated and screened from the vicinity of the Salt Lake. The X-NM1 with the strongest capability to induce carbonate deposition was finally selected. It was identified as Staphylococcus epidermidis by 16S rDNA analysis. The induced calcium carbonate deposition was 16.8 g/L, the urease activity was 3.353 mM/min, and the mineralization product was spherical calcite crystals. The X-NM1 was further tested by sand cementation, considering the effect of grouting cycles on sand column solidification. The results showed that with the increase of grouting cycles, the permeability coefficient and porosity of sand columns decreased, while the dry density, pore filling ratio, uniaxial compressive strength and calcium carbonate content increased gradually. After three cycles of grouting, the appearance structure of sand columns was intact, the dry density, the permeability coefficient, the porosity, the pore filling ratio, the uniaxial compressive strength, and the CaCO3 content was 1.99 g/cm3, 1.51×10-3 cm/s, 26.35%, 15.42%, 2.52 MPa, and 24.5% respectively. The results showed that X-NM1 was of excellent capability to induce calcium carbonate deposition.
Several varieties of bacteria were isolated and screened from the vicinity of the Salt Lake. The X-NM1 with the strongest capability to induce carbonate deposition was finally selected. It was identified as Staphylococcus epidermidis by 16S rDNA analysis. The induced calcium carbonate deposition was 16.8 g/L, the urease activity was 3.353 mM/min, and the mineralization product was spherical calcite crystals. The X-NM1 was further tested by sand cementation, considering the effect of grouting cycles on sand column solidification. The results showed that with the increase of grouting cycles, the permeability coefficient and porosity of sand columns decreased, while the dry density, pore filling ratio, uniaxial compressive strength and calcium carbonate content increased gradually. After three cycles of grouting, the appearance structure of sand columns was intact, the dry density, the permeability coefficient, the porosity, the pore filling ratio, the uniaxial compressive strength, and the CaCO3 content was 1.99 g/cm3, 1.51×10-3 cm/s, 26.35%, 15.42%, 2.52 MPa, and 24.5% respectively. The results showed that X-NM1 was of excellent capability to induce calcium carbonate deposition.
2022, 52(11): 104-110.
doi: 10.13204/j.gyjzG21092613
Abstract:
Taking the traditional rural settlements in the Yiluo River basin as research objects, the characteristics adjacent to waters and pattern evolution of the settlements were explored. Aiming at the traditional rural settlement in the Yiluo River basin, the different characteristics of spatial patterns for traditional rural settlements in the Yiluo River basin were studied by the spatial analysis methods such as the nearest index of GIS, the core density analysis and the measurement methods of settlement patterns involving aspect ratios and shape indexes, and simultaneously, by means of space-time analysis. The results showed that traditionally rural settlements in the Yiluo River basin appeared the spatial distribution characteristics of "large concentration and small dispersion", and the traditionally rural settlements had obvious characteristics of tendency to waters; the pattern characteristics of rural settlements adjacent to waters were evident, and the spatial patterns experienced the evolution of different stages from "adjacent to waters-along rivers-crossing rivers". By quantitative analysis, the pattern characteristics of rural settlements could be effectively identified and settlements should give full play to their own characteristic advantages to promote their benign development.
Taking the traditional rural settlements in the Yiluo River basin as research objects, the characteristics adjacent to waters and pattern evolution of the settlements were explored. Aiming at the traditional rural settlement in the Yiluo River basin, the different characteristics of spatial patterns for traditional rural settlements in the Yiluo River basin were studied by the spatial analysis methods such as the nearest index of GIS, the core density analysis and the measurement methods of settlement patterns involving aspect ratios and shape indexes, and simultaneously, by means of space-time analysis. The results showed that traditionally rural settlements in the Yiluo River basin appeared the spatial distribution characteristics of "large concentration and small dispersion", and the traditionally rural settlements had obvious characteristics of tendency to waters; the pattern characteristics of rural settlements adjacent to waters were evident, and the spatial patterns experienced the evolution of different stages from "adjacent to waters-along rivers-crossing rivers". By quantitative analysis, the pattern characteristics of rural settlements could be effectively identified and settlements should give full play to their own characteristic advantages to promote their benign development.
2022, 52(11): 111-119,188.
doi: 10.13204/j.gyjzG21112101
Abstract:
Taking industrial relics in St. Petersburg, Russia as an example, this paper summarized the types and characteristics of modern transformation of industrial heritage. Industrial heritage is an important part of cultural heritage, based on the value of Russian historical cities protection principle and guide, the comprehensive benefits of urban industrial heritage history area update activation were analyzed, the sustainable development ideas for historical cities were developed, which could provide a reference for the protection and development experience of historical buildings in old industrial bases in our country.
Taking industrial relics in St. Petersburg, Russia as an example, this paper summarized the types and characteristics of modern transformation of industrial heritage. Industrial heritage is an important part of cultural heritage, based on the value of Russian historical cities protection principle and guide, the comprehensive benefits of urban industrial heritage history area update activation were analyzed, the sustainable development ideas for historical cities were developed, which could provide a reference for the protection and development experience of historical buildings in old industrial bases in our country.
2022, 52(11): 120-124,156.
doi: 10.13204/j.gyjzG21080104
Abstract:
The protection and utilization of industrial heritage has become an increasingly important issue for the government and society, and the formulation of laws, regulations and policy documents is a core content of management. Although the national laws and regulations on the protection of industrial heritage are still absent, some provinces and cities have made remarkable achievements in the legal construction of industrial heritage in recent years. By exploring the legalization process of local industrial heritage protection in China, the paper systematically combed the formulation process of laws, regulations and policy documents, compared the compilation contents of laws, regulations and policies for the protection and utilization of 31 local industrial heritage in China, point out the problems, and put forward suggestions for the construction of laws, regulations and legal management of industrial heritage in China.
The protection and utilization of industrial heritage has become an increasingly important issue for the government and society, and the formulation of laws, regulations and policy documents is a core content of management. Although the national laws and regulations on the protection of industrial heritage are still absent, some provinces and cities have made remarkable achievements in the legal construction of industrial heritage in recent years. By exploring the legalization process of local industrial heritage protection in China, the paper systematically combed the formulation process of laws, regulations and policy documents, compared the compilation contents of laws, regulations and policies for the protection and utilization of 31 local industrial heritage in China, point out the problems, and put forward suggestions for the construction of laws, regulations and legal management of industrial heritage in China.
2022, 52(11): 125-132,48.
doi: 10.13204/j.gyjzG21013004
Abstract:
Taking the traditional commercial blocks in south and west Anhui as research object, a linguistic method was used to analyze the form of semantic ontology in terms of building plane features, facade features, structural components, doors, windows and details of decoration and other components. Moreover, a sample database of the traditional commercial blocks in south and west Anhui was established to study the forms of regional commercial buildings, in order to provide a reference for the style and features of protection of traditional commercial blocks.
Taking the traditional commercial blocks in south and west Anhui as research object, a linguistic method was used to analyze the form of semantic ontology in terms of building plane features, facade features, structural components, doors, windows and details of decoration and other components. Moreover, a sample database of the traditional commercial blocks in south and west Anhui was established to study the forms of regional commercial buildings, in order to provide a reference for the style and features of protection of traditional commercial blocks.
2022, 52(11): 133-138.
doi: 10.13204/j.gyjzG22062009
Abstract:
To ensure the safe and reliable operation of nuclear power plants (NPPs) during their extended service lives, the performance of reinforced concrete structures in NPPs under long-term irradiation is quite important. A comprehensive framework of models was developed to predict the various properties and deformation of nuclear-irradiated concrete. The GSC model and the Mori-Tanaka model were used to characterize the mechanical and transport properties of concrete with multiple phases and multi-scale internal structures. The damage to the concrete’s mechanical properties resulting from irradiation and elevated temperature was estimated by using a composite damage mechanics approach. The transport properties in degraded concrete were calculated using multi-group diffusion equations, considering the temperature gradient and the damage induced by irradiation. Finally, all models were combined and implemented as a coupled radio-thermo-mechanical analysis to predict the long-term mechanical and transport responses of concrete. The work represents a comprehensive framework that can be used as user-defined material models combined with commercial finite element software products for future application of numerical analysis of concrete and reinforced concrete structures in nuclear power plants.
To ensure the safe and reliable operation of nuclear power plants (NPPs) during their extended service lives, the performance of reinforced concrete structures in NPPs under long-term irradiation is quite important. A comprehensive framework of models was developed to predict the various properties and deformation of nuclear-irradiated concrete. The GSC model and the Mori-Tanaka model were used to characterize the mechanical and transport properties of concrete with multiple phases and multi-scale internal structures. The damage to the concrete’s mechanical properties resulting from irradiation and elevated temperature was estimated by using a composite damage mechanics approach. The transport properties in degraded concrete were calculated using multi-group diffusion equations, considering the temperature gradient and the damage induced by irradiation. Finally, all models were combined and implemented as a coupled radio-thermo-mechanical analysis to predict the long-term mechanical and transport responses of concrete. The work represents a comprehensive framework that can be used as user-defined material models combined with commercial finite element software products for future application of numerical analysis of concrete and reinforced concrete structures in nuclear power plants.
2022, 52(11): 139-143,212.
doi: 10.13204/j.gyjzG21112513
Abstract:
In order to study deterioration laws of concrete under combined action of cyclic flexural loads and carbonation, the accelerated carbonation test for RC beams under cyclic flexural loads was conducted. Simultaneously, based on theoretical analysis and experiment results, a prediction model for carbonation depth was proposed, which could quantitatively analyze the influence of stress levels and loading cycles on carbonation depths of concrete. Finally, the model was verified by existing test results. The results showed that carbonation depths of concrete increased with increase of carbonation time, but the carbonation rate slowed down gradually; the higher the stress level and the more loading cycles, the more serious the fatigue damage of concrete, which would accelerate carbonation of concrete; the predicted values by the carbonation depth model were in good agreement with the experimental results, and the relative errors were less than 5%. The model could be used to predict the carbonation depth of concrete under repeated loading.
In order to study deterioration laws of concrete under combined action of cyclic flexural loads and carbonation, the accelerated carbonation test for RC beams under cyclic flexural loads was conducted. Simultaneously, based on theoretical analysis and experiment results, a prediction model for carbonation depth was proposed, which could quantitatively analyze the influence of stress levels and loading cycles on carbonation depths of concrete. Finally, the model was verified by existing test results. The results showed that carbonation depths of concrete increased with increase of carbonation time, but the carbonation rate slowed down gradually; the higher the stress level and the more loading cycles, the more serious the fatigue damage of concrete, which would accelerate carbonation of concrete; the predicted values by the carbonation depth model were in good agreement with the experimental results, and the relative errors were less than 5%. The model could be used to predict the carbonation depth of concrete under repeated loading.
2022, 52(11): 144-150,168.
doi: 10.13204/j.gyjzG22022709
Abstract:
It is of great significance to perform the mechanical properties of connections of pre-stressed concrete columns for promoting the development of pre-stressed concrete frame structure which is a typical kind of assembled structure with fully-dry connections. In this paper, the mechanical properties of three kinds of connections of pre-stressed concrete columns were studied through quasi-static connection of loading tests. The quasi-static tests on the connection of unbonded pre-stressed concrete column (UBPC), bonded pre-stressed concrete column (BPC), and the connection between longitudinal rebar and unbonded pre-stressed concrete column (RUBPC) were carried out under unidirectional eccentric compression. The experimental results demonstrated a better ductility for the three connections. When the deformation of the columns reached 1/50 which was the elastic-plastic inter-story drift of RC frame structure, the maximum bearing capacity was still more than 85% of the ultimate bearing capacity for each specimen. For UBPC and BPC, the damage of precast column was effectively reduced due to the opening of the bonding surface at column bottom, while their ultimate bearing capacity was 15%~20% lower than that of RUBPC. In addition, the energy dissipation of UBPC and BPC was less than that of RUBPC. When Compared with RUBPC, UBPC and BPC presented better re-centering capacity and smaller residual deformation. Moreover, the steel rods remained elastic during tests for all the specimens, and their initial tensile forces in RUBPC and UBPC were decreased by 12% when the specimens were destroyed. Compared with UBPC, the BPC presented a larger bearing force and a better energy dissipation.
It is of great significance to perform the mechanical properties of connections of pre-stressed concrete columns for promoting the development of pre-stressed concrete frame structure which is a typical kind of assembled structure with fully-dry connections. In this paper, the mechanical properties of three kinds of connections of pre-stressed concrete columns were studied through quasi-static connection of loading tests. The quasi-static tests on the connection of unbonded pre-stressed concrete column (UBPC), bonded pre-stressed concrete column (BPC), and the connection between longitudinal rebar and unbonded pre-stressed concrete column (RUBPC) were carried out under unidirectional eccentric compression. The experimental results demonstrated a better ductility for the three connections. When the deformation of the columns reached 1/50 which was the elastic-plastic inter-story drift of RC frame structure, the maximum bearing capacity was still more than 85% of the ultimate bearing capacity for each specimen. For UBPC and BPC, the damage of precast column was effectively reduced due to the opening of the bonding surface at column bottom, while their ultimate bearing capacity was 15%~20% lower than that of RUBPC. In addition, the energy dissipation of UBPC and BPC was less than that of RUBPC. When Compared with RUBPC, UBPC and BPC presented better re-centering capacity and smaller residual deformation. Moreover, the steel rods remained elastic during tests for all the specimens, and their initial tensile forces in RUBPC and UBPC were decreased by 12% when the specimens were destroyed. Compared with UBPC, the BPC presented a larger bearing force and a better energy dissipation.
2022, 52(11): 151-156.
doi: 10.13204/j.gyjzG21102601
Abstract:
Prestress detection is an important content of prestressed concrete structure detection, but there is no standardized method. The temperature shrinkage stress of super-long concrete structures after causes a large number of cracks which exceed the requirements of relevant specifications, but there is no effective method to detect the temperature shrinkage stress of concrete structures in situ. The finite element simulation of double groove stress release of concrete cover was carried out under four conditions of different sections and different stress states. Based on the analysis of the relations between strain release rate and groove depth, the 25 mm grooving method and the maximum release rate method of concrete cover were proposed. For concrete cover 25mm grooving method, the influence of temperature could be eliminated because of the grooving speed was fast. The data of maximum release rate method was stable and the predicted value was more accurate. The maneuverability and accuracy of the method were verified by field test of a certain project.
Prestress detection is an important content of prestressed concrete structure detection, but there is no standardized method. The temperature shrinkage stress of super-long concrete structures after causes a large number of cracks which exceed the requirements of relevant specifications, but there is no effective method to detect the temperature shrinkage stress of concrete structures in situ. The finite element simulation of double groove stress release of concrete cover was carried out under four conditions of different sections and different stress states. Based on the analysis of the relations between strain release rate and groove depth, the 25 mm grooving method and the maximum release rate method of concrete cover were proposed. For concrete cover 25mm grooving method, the influence of temperature could be eliminated because of the grooving speed was fast. The data of maximum release rate method was stable and the predicted value was more accurate. The maneuverability and accuracy of the method were verified by field test of a certain project.
2022, 52(11): 157-161,138.
doi: 10.13204/j.gyjzG21101311
Abstract:
In order to promote the application of recycled concrete in structural engineering, especially in industrial construction, a kind of steel fiber reinforced recycled concrete with prefabricated layer and cast-in-situ layer as bidirectional composite slab (semi-recycled-semi-ordinary concrete composite slab) was proposed. Based on the theory of elastic thin slab, a formula for calculating the deflection of elastic stage was established according to its orthotropic structural characteristics. The calculation method of elastic-plastic stage deflection considering precise bending moment was given. On this basis, the comparison between theoretical calculation and experimental results showed that the elastic and elastic-plastic stage deflection calculation presented in the paper was practical and effective.
In order to promote the application of recycled concrete in structural engineering, especially in industrial construction, a kind of steel fiber reinforced recycled concrete with prefabricated layer and cast-in-situ layer as bidirectional composite slab (semi-recycled-semi-ordinary concrete composite slab) was proposed. Based on the theory of elastic thin slab, a formula for calculating the deflection of elastic stage was established according to its orthotropic structural characteristics. The calculation method of elastic-plastic stage deflection considering precise bending moment was given. On this basis, the comparison between theoretical calculation and experimental results showed that the elastic and elastic-plastic stage deflection calculation presented in the paper was practical and effective.
2022, 52(11): 162-168.
doi: 10.13204/j.gyjzG20122906
Abstract:
In order to explore the influence of alkali excitation on the mechanical properties of aeolian sand concrete under normal temperature curing, this study selected the Kubuqi Desert aeolian sand instead of river sand (40%), and using NaOH as the activator to configure alkali-activated aeolian sand concrete. Through compressive strength test and nuclear magnetic resonance test, the compressive strength and pore change law of aeolian sand concrete under normal temperature curing were studied. By introducing grey entropy correlation degree, the compressive strength model of alkali activated aeolian sand concrete was established. The results showed that under normal temperature curing, with the increase of NaOH content, the compressive strength of aeolian sand concrete first increased and then decreased. The porosity first decreased and then increased. The average increase rate of compressive strength of aeolian sand concrete was the highest when 5% NaOH was added, up to 51.02 MPa at 28 d, the pore structure was the best. The 28 d compressive strength of aeolian sand concrete replaced by 40% fly ash which was activated by 5% NaOH was equivalent to that of ordinary 20% fly ash aeolian sand concrete, and its pore structure was better, so as to effectively improve the utilization rate of fly ash and reduce the amount of cement. Furthermore, a predictive model of compressive strength GM(1,2) was established based on the gray entropy correlation degree. The average relative errors between predicted values and test values were 1.96% and 1.34%, with high accuracy.
In order to explore the influence of alkali excitation on the mechanical properties of aeolian sand concrete under normal temperature curing, this study selected the Kubuqi Desert aeolian sand instead of river sand (40%), and using NaOH as the activator to configure alkali-activated aeolian sand concrete. Through compressive strength test and nuclear magnetic resonance test, the compressive strength and pore change law of aeolian sand concrete under normal temperature curing were studied. By introducing grey entropy correlation degree, the compressive strength model of alkali activated aeolian sand concrete was established. The results showed that under normal temperature curing, with the increase of NaOH content, the compressive strength of aeolian sand concrete first increased and then decreased. The porosity first decreased and then increased. The average increase rate of compressive strength of aeolian sand concrete was the highest when 5% NaOH was added, up to 51.02 MPa at 28 d, the pore structure was the best. The 28 d compressive strength of aeolian sand concrete replaced by 40% fly ash which was activated by 5% NaOH was equivalent to that of ordinary 20% fly ash aeolian sand concrete, and its pore structure was better, so as to effectively improve the utilization rate of fly ash and reduce the amount of cement. Furthermore, a predictive model of compressive strength GM(1,2) was established based on the gray entropy correlation degree. The average relative errors between predicted values and test values were 1.96% and 1.34%, with high accuracy.
2022, 52(11): 169-174.
doi: 10.13204/j.gyjzG22041802
Abstract:
The free-form curved roof of Changsha Live atrium is supported across the four structural monomers in the lower part, the middle part is an openable roof, and the secondary membrane structure is rooted on the main structure. The atrium roof adopts a long-span single-layer reticulated shell structure. The structural selection and the reasonable setting method of fixed hinge supports and sliding hinge supports were introduced. The wind load of the roof should be taken according to the local natural conditions and the wind tunnel test report. The finite element software MIDAS/Gen was used to analyze the static and overall stability of the reticulated shell structure, and the reticulated shell and the lower concrete structure were assembled to analyze the influence of the lower structure on the stress of the reticulated shell structure by comparing the natural vibration period, displacement and support reaction. The design bearing capacity and stiffness of the joint were analyzed by finite element model, all calculation results of reticulated could meet the requirements. In addition, deformation monitoring was carried out during construction, and the monitoring values were within the design calculation range.
The free-form curved roof of Changsha Live atrium is supported across the four structural monomers in the lower part, the middle part is an openable roof, and the secondary membrane structure is rooted on the main structure. The atrium roof adopts a long-span single-layer reticulated shell structure. The structural selection and the reasonable setting method of fixed hinge supports and sliding hinge supports were introduced. The wind load of the roof should be taken according to the local natural conditions and the wind tunnel test report. The finite element software MIDAS/Gen was used to analyze the static and overall stability of the reticulated shell structure, and the reticulated shell and the lower concrete structure were assembled to analyze the influence of the lower structure on the stress of the reticulated shell structure by comparing the natural vibration period, displacement and support reaction. The design bearing capacity and stiffness of the joint were analyzed by finite element model, all calculation results of reticulated could meet the requirements. In addition, deformation monitoring was carried out during construction, and the monitoring values were within the design calculation range.
2022, 52(11): 175-180,174.
doi: 10.13204/j.gyjzG21070506
Abstract:
In order to obtain the calculation formula of the ultimate bearing capacity of cold-formed thin-walled C-shaped steel double-limbed closed built-up columns, the line software CUFSM and the direct strength method DSM were used to calculate the ultimate bearing capacity of single-limbed cold-formed thin-walled C-shaped steel member. ABAQUS finite element analysis software was used to calculate the ultimate bearing capacity of cold-formed thin-walled C-shaped steel double-limbed closed built-up columns under axial compression. By comparing the ultimate bearing capacity of single-limb cold-formed thin-walled C-shaped steel members and cold-formed thin-walled C-shaped steel double-limbed closed built-up columns under different cross-sectional geometric parameters, the influence of each parameter on the combined effect coefficients of built-up columns was determined, as well as the relations between combined effect coefficients and two important parameters. The 1stopt fitting software was used to perform regression analysis on a large number of obtained combined effect values, and the combined effect coefficient simplified formula and ultimate bearing capacity calculation formula of cold-formed thin-walled C-shaped steel double-limbed closed built-up columns were established.
In order to obtain the calculation formula of the ultimate bearing capacity of cold-formed thin-walled C-shaped steel double-limbed closed built-up columns, the line software CUFSM and the direct strength method DSM were used to calculate the ultimate bearing capacity of single-limbed cold-formed thin-walled C-shaped steel member. ABAQUS finite element analysis software was used to calculate the ultimate bearing capacity of cold-formed thin-walled C-shaped steel double-limbed closed built-up columns under axial compression. By comparing the ultimate bearing capacity of single-limb cold-formed thin-walled C-shaped steel members and cold-formed thin-walled C-shaped steel double-limbed closed built-up columns under different cross-sectional geometric parameters, the influence of each parameter on the combined effect coefficients of built-up columns was determined, as well as the relations between combined effect coefficients and two important parameters. The 1stopt fitting software was used to perform regression analysis on a large number of obtained combined effect values, and the combined effect coefficient simplified formula and ultimate bearing capacity calculation formula of cold-formed thin-walled C-shaped steel double-limbed closed built-up columns were established.
2022, 52(11): 181-188.
doi: 10.13204/j.gyjzG21121006
Abstract:
In order to study the mechanical properties of CFRP confined concrete-filled square steel tubular under bending-torsion load, based on the experimental study of mechanical properties of nine CFRP confined concrete-filled square steel tubular under bending-torsion load, the T-θ curve and failure mode of CFRP confined concrete-filled square steel tubular were simulated by using the finite element software ABAQUS, and the simulation results were compared with the experimental results. The results showed that the simulation results were in good agreement with the experimental results. On the basis of verifying the reliability of the model, the whole stress process and parameter analysis of the component were studied. On the basis of finite element simulation and test, the calculation expression of bearing capacity of CFRP, confined concrete-filled square steel tubular under bending-torsion load was proposed. The research showed that the bearing capacity of member increased significantly with the increase of concrete strength, steel yield strength and steel ratio, increased slightly with the increase of CFRP layers, and decreased slightly with the increase of moment ratio. The bearing capacity of specimen predicted by the proposed calculation expression was basically consistent with the test results.
In order to study the mechanical properties of CFRP confined concrete-filled square steel tubular under bending-torsion load, based on the experimental study of mechanical properties of nine CFRP confined concrete-filled square steel tubular under bending-torsion load, the T-θ curve and failure mode of CFRP confined concrete-filled square steel tubular were simulated by using the finite element software ABAQUS, and the simulation results were compared with the experimental results. The results showed that the simulation results were in good agreement with the experimental results. On the basis of verifying the reliability of the model, the whole stress process and parameter analysis of the component were studied. On the basis of finite element simulation and test, the calculation expression of bearing capacity of CFRP, confined concrete-filled square steel tubular under bending-torsion load was proposed. The research showed that the bearing capacity of member increased significantly with the increase of concrete strength, steel yield strength and steel ratio, increased slightly with the increase of CFRP layers, and decreased slightly with the increase of moment ratio. The bearing capacity of specimen predicted by the proposed calculation expression was basically consistent with the test results.
2022, 52(11): 189-193.
doi: 10.13204/j.gyjzG21111515
Abstract:
Taking a practical super high-rise building as a case study, the improved viscous damping outrigger scheme which contains a lever mechanism installed at the end of the truss was proposed to amplify the deformation of the dampers in conventional viscous damping outrigger in earthquakes. The comparative analysis of damping effect of the two different damping schemes was carried out, and the main parameters (damper parameters and leverage ratio) affecting the energy dissipation efficiency of the newly-proposed viscous damping outrigger scheme were studied. The results indicated that the newly-proposed viscous damping outrigger scheme could amplify the deformation and velocity of dampers effectively, and the amplification factor was approximately equal to the leverage ratio of the T-shaped rigid arm; as the lever ratio increased, the optimal damping coefficient of the newly-proposed viscously damped outrigger decreased gradually. The product of the optimal damping coefficient and the leverage ratio in the newly-proposed viscous damping outrigger was approximately equal to the optimal damping coefficient of the conventional viscously damped outrigger.
Taking a practical super high-rise building as a case study, the improved viscous damping outrigger scheme which contains a lever mechanism installed at the end of the truss was proposed to amplify the deformation of the dampers in conventional viscous damping outrigger in earthquakes. The comparative analysis of damping effect of the two different damping schemes was carried out, and the main parameters (damper parameters and leverage ratio) affecting the energy dissipation efficiency of the newly-proposed viscous damping outrigger scheme were studied. The results indicated that the newly-proposed viscous damping outrigger scheme could amplify the deformation and velocity of dampers effectively, and the amplification factor was approximately equal to the leverage ratio of the T-shaped rigid arm; as the lever ratio increased, the optimal damping coefficient of the newly-proposed viscously damped outrigger decreased gradually. The product of the optimal damping coefficient and the leverage ratio in the newly-proposed viscous damping outrigger was approximately equal to the optimal damping coefficient of the conventional viscously damped outrigger.
2022, 52(11): 194-198,206.
doi: 10.13204/j.gyjzG22022206
Abstract:
In order to clarify the damage deterioration law of durability indexes such as apparent morphology, quality, water absorption and compressive strength of aeolian sand concrete under carbonization and dry-wet cycles, aeolian sand was completely replaced by ordinary river sand to prepare aeolian sand concrete, and its carbonization test (carbonization age was 0 d, 14 d and 28 d) was carried out, apparent morphology, compressive strength, quality, water absorption and other parameters were used to characterize the deterioration law of durability of aeolian sand concrete under carbonation and dry-wet cycles. The results showed that the morphology changed little in the early stage of carbonization and dry-wet cycles, and network cracks gradually appeared in the later stage; with the increase of dry-wet cycles, the compressive strength of aeolian sand concrete first increased and then decreased; the mass of non carbonated concrete increased the most in 25 seconds of dry-wet cycles, and the mass of carbonated concrete increased the least in 28 days of carbonation age; carbonation delayed the occurrence time of surface salt crystallization, improved the compressive strength of aeolian sand concrete, as well as the durability of aeolian sand concrete in dry and wet environment.
In order to clarify the damage deterioration law of durability indexes such as apparent morphology, quality, water absorption and compressive strength of aeolian sand concrete under carbonization and dry-wet cycles, aeolian sand was completely replaced by ordinary river sand to prepare aeolian sand concrete, and its carbonization test (carbonization age was 0 d, 14 d and 28 d) was carried out, apparent morphology, compressive strength, quality, water absorption and other parameters were used to characterize the deterioration law of durability of aeolian sand concrete under carbonation and dry-wet cycles. The results showed that the morphology changed little in the early stage of carbonization and dry-wet cycles, and network cracks gradually appeared in the later stage; with the increase of dry-wet cycles, the compressive strength of aeolian sand concrete first increased and then decreased; the mass of non carbonated concrete increased the most in 25 seconds of dry-wet cycles, and the mass of carbonated concrete increased the least in 28 days of carbonation age; carbonation delayed the occurrence time of surface salt crystallization, improved the compressive strength of aeolian sand concrete, as well as the durability of aeolian sand concrete in dry and wet environment.
2022, 52(11): 199-206.
doi: 10.13204/j.gyjzG22022406
Abstract:
For the waste fresh concrete that cannot be used due to too long storage time, the optimal storage time (120 min) was selected comprehensively by testing the effect of storage time on the performance of waste fresh concrete, and fresh concrete was replaced at 30% replacement rate to directly prepare recycled fresh concrete. At the same time, the influence of different nano-silica content on the mechanical properties and working properties of recycled fresh concrete was tested, and its microstructure and structure were analyzed. The results showed that when the nano-silica content was 3%, the 28 d compressive strength and splitting tensile strength of recycled fresh concrete were increased by 45.6% and 63.9%; XRD, SEM and EDS analysis showed that the precipitation of H2SiO3 acid in the nano-silica could be accelerated in an alkaline environment, and a large amount of C-S-H gel (type I) gel could be formed by reacting with Ca2+, they could promote the hydration reaction of clinker such as C3S and C2S, reduce Ca/Si and make cement paste and aggregate closely connected, C-S-H gel filled some pores and cracks, the interface transition zone was more compact, and the strength of recycled fresh concrete was significantly improved.
For the waste fresh concrete that cannot be used due to too long storage time, the optimal storage time (120 min) was selected comprehensively by testing the effect of storage time on the performance of waste fresh concrete, and fresh concrete was replaced at 30% replacement rate to directly prepare recycled fresh concrete. At the same time, the influence of different nano-silica content on the mechanical properties and working properties of recycled fresh concrete was tested, and its microstructure and structure were analyzed. The results showed that when the nano-silica content was 3%, the 28 d compressive strength and splitting tensile strength of recycled fresh concrete were increased by 45.6% and 63.9%; XRD, SEM and EDS analysis showed that the precipitation of H2SiO3 acid in the nano-silica could be accelerated in an alkaline environment, and a large amount of C-S-H gel (type I) gel could be formed by reacting with Ca2+, they could promote the hydration reaction of clinker such as C3S and C2S, reduce Ca/Si and make cement paste and aggregate closely connected, C-S-H gel filled some pores and cracks, the interface transition zone was more compact, and the strength of recycled fresh concrete was significantly improved.
2022, 52(11): 207-212.
doi: 10.13204/j.gyjzG22022812
Abstract:
The marine environment is harsh and complex, and coastal buildings are prone to deterioration under the combined action of physical and chemical destruction factors. In this paper, concrete with ordinary strength, high durability and underwater separation resistance was prepared based on the marine environment in Phase I project of Jingtang, Shougang in Caofeidian of Tangshan. The cementitious material system was optimized by adding ground slag and fly ash to improve the strength, compactness and durability of concrete. The mixture of anti-corrosion rust-resistance high-performance water-proof agent and appropriate amount of air entrainment agent improve the corrosion resistance and frost resistance of concrete, and improve the separation resistance of C35F300 underwater concrete. The results showed that the slump of concrete was 210 mm, the gas content was 5.4%, the compressive strength was 50.6 MPa, and the chloride ion erosion coefficient was 2.6×10-12 m2/s, fully met the requirements of C35F300 (300 freeze-thaw cydes and C35 strength grade). Through engineering practice, the working performance, mechanical properties, anti-separation performance and durability of concrete could meet the requirements of concrete of underwater structures.
The marine environment is harsh and complex, and coastal buildings are prone to deterioration under the combined action of physical and chemical destruction factors. In this paper, concrete with ordinary strength, high durability and underwater separation resistance was prepared based on the marine environment in Phase I project of Jingtang, Shougang in Caofeidian of Tangshan. The cementitious material system was optimized by adding ground slag and fly ash to improve the strength, compactness and durability of concrete. The mixture of anti-corrosion rust-resistance high-performance water-proof agent and appropriate amount of air entrainment agent improve the corrosion resistance and frost resistance of concrete, and improve the separation resistance of C35F300 underwater concrete. The results showed that the slump of concrete was 210 mm, the gas content was 5.4%, the compressive strength was 50.6 MPa, and the chloride ion erosion coefficient was 2.6×10-12 m2/s, fully met the requirements of C35F300 (300 freeze-thaw cydes and C35 strength grade). Through engineering practice, the working performance, mechanical properties, anti-separation performance and durability of concrete could meet the requirements of concrete of underwater structures.
