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2021 Vol. 51, No. 2
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2021, 51(2): 1-6,75.
doi: 10.13204/j.gyjzG20080605
Abstract:
At present, the high-density degree of urban space is getting higher and higher, while the comprehensive quality of urban environment is gradually reduced. The application of the theory of sky-view factor is of great value to optimize the urban visual environment and improve the local climate. Based on the research results at home and abroad, this paper optimized the calculation model of urban space sky-view factor based on the functions of 3D spatial modeling and intervisibility analysis of GIS software. Then based on the urban morphology and architectural design principles, the important indicators of residential space form were selected and quantified. Through the software simulation and analysis of high-density urban residential areas, the paper explored the quantitative relationship between the sky-view factor of high-density residential areas and the spatial form of residential areas, provided a reasonable quantitative analysis method for urban spatial environment evaluation.
At present, the high-density degree of urban space is getting higher and higher, while the comprehensive quality of urban environment is gradually reduced. The application of the theory of sky-view factor is of great value to optimize the urban visual environment and improve the local climate. Based on the research results at home and abroad, this paper optimized the calculation model of urban space sky-view factor based on the functions of 3D spatial modeling and intervisibility analysis of GIS software. Then based on the urban morphology and architectural design principles, the important indicators of residential space form were selected and quantified. Through the software simulation and analysis of high-density urban residential areas, the paper explored the quantitative relationship between the sky-view factor of high-density residential areas and the spatial form of residential areas, provided a reasonable quantitative analysis method for urban spatial environment evaluation.
2021, 51(2): 7-11.
doi: 10.13204/j.gyjzG20072903
Abstract:
A practical and refined structural system is a key factor in shaping the internal spaces and external forms of buildings, and it also is a rational construction basis for the expression of architectural aesthetics. The traditional use of arch structure has been developed to all aspects of buildings. For large numbers of public building spaces, the contemporary arch structure has broken through the traditional paradigm and template, created distinctive spaces and atmospheres for museums, libraries and other public buildings by spatial structure forms, expressing clear technical aesthetic characteristics.
A practical and refined structural system is a key factor in shaping the internal spaces and external forms of buildings, and it also is a rational construction basis for the expression of architectural aesthetics. The traditional use of arch structure has been developed to all aspects of buildings. For large numbers of public building spaces, the contemporary arch structure has broken through the traditional paradigm and template, created distinctive spaces and atmospheres for museums, libraries and other public buildings by spatial structure forms, expressing clear technical aesthetic characteristics.
2021, 51(2): 12-17.
doi: 10.13204/j.gyjzG20062304
Abstract:
The house-style Diaolou dwellings in southern Sichuan are an important part of Chinese Diaolou dwellings. Their architectural features are different from the tower-style stone Diaolou buildings in Tibetan areas, and also different from the brick and stone Diaolou buildings which combining Chinese and Westem cultures in the southeast coastal area. They are views in Sichuan dwellings. On the basis of extensive investigation of Naxi, Hejiang and Xuyong areas on the south bank of the Yangtze River in Luzhou, the typical representative rural Diaolou dwellings in Lizhai town of Naxida town were selected as the research object of surveying and mapping, the spatial layout, building structure, eaves corner structure and Diaolou structure were analyzed, its architectural morphological characteristics were revealed, and the construction technology of such local dwellings was summarized. In particular, the comparative analysis of the roof construction of Xieshan Diaolou showed that it was a kind of integrated construction method, which indirectly proved that the local traditional architectural culture was a kind of integrated architectural culture. Finally, the paper provided some suggestions for the improvement of the main problems of residential buildings and made some design demonstration, in order to provide reference for the repair and protection of dwellings in this area.
The house-style Diaolou dwellings in southern Sichuan are an important part of Chinese Diaolou dwellings. Their architectural features are different from the tower-style stone Diaolou buildings in Tibetan areas, and also different from the brick and stone Diaolou buildings which combining Chinese and Westem cultures in the southeast coastal area. They are views in Sichuan dwellings. On the basis of extensive investigation of Naxi, Hejiang and Xuyong areas on the south bank of the Yangtze River in Luzhou, the typical representative rural Diaolou dwellings in Lizhai town of Naxida town were selected as the research object of surveying and mapping, the spatial layout, building structure, eaves corner structure and Diaolou structure were analyzed, its architectural morphological characteristics were revealed, and the construction technology of such local dwellings was summarized. In particular, the comparative analysis of the roof construction of Xieshan Diaolou showed that it was a kind of integrated construction method, which indirectly proved that the local traditional architectural culture was a kind of integrated architectural culture. Finally, the paper provided some suggestions for the improvement of the main problems of residential buildings and made some design demonstration, in order to provide reference for the repair and protection of dwellings in this area.
2021, 51(2): 18-25,82.
doi: 10.13204/j.gyjzG20061704
Abstract:
Xi'an, as the starting point of the Silk Road, has been communicating with the Western Regions since ancient times. With the connection of Longhai Railway in modern times, it is also influenced by westem culture. Architectural culture is also effected by both of them. Based on the survey and drawing of the existing traditional public and residential buildings in Xi'an, and the cultural influence on account of the spread of western culture influenced to the east, the paper divided them into three types, i.e. native traditional building, syncretic building influenced by Islamic culture, and eclectic buildings influenced by westem culture. The paper foused on the distribution area, architectural form, construction technology, decorative symbols to put forward the different typological characteristics of the latter two types, which was effected by different cultures.
Xi'an, as the starting point of the Silk Road, has been communicating with the Western Regions since ancient times. With the connection of Longhai Railway in modern times, it is also influenced by westem culture. Architectural culture is also effected by both of them. Based on the survey and drawing of the existing traditional public and residential buildings in Xi'an, and the cultural influence on account of the spread of western culture influenced to the east, the paper divided them into three types, i.e. native traditional building, syncretic building influenced by Islamic culture, and eclectic buildings influenced by westem culture. The paper foused on the distribution area, architectural form, construction technology, decorative symbols to put forward the different typological characteristics of the latter two types, which was effected by different cultures.
2021, 51(2): 26-31.
doi: 10.13204/j.gyjzG19111803
Abstract:
To study the calculation method of axial compressive bearing capacity for ultra-high performance concrete (UHPC) square short columns confined by high-strength stirrups. 9 UHPC square short columns confined by stirrups were tested under axial compression, and combined with the collected relevant literature data, the formula for calculating the peak stress of confined UHPC was given on the basis of Richart's failure criterion. And further suggested a calculation formula of axial compression bearing capacity, which was applicable to the high-strength stirrup confined UHPC square short columns with strength of UHPC ranging from 130 MPa to 180 MPa, steel fiber content ranging from 1.5% to 2% and volume stirrup ratio ranging from 1.5% to 5.5%; the suggested formula was compared with the standard formula of China and America. The results showed that the bearing capacity of UHPC predicted by GB 50010-2010 was more conservative than that of ACI 318-2014. The bearing capacity formula considered the effects of steel fiber bridge and stirrup restraint, and the calculated values were in good agreement with the test values. It was suggested to use high-strength stirrup above 600 MPa to restrain UHPC. The upper limit of the stirrup spacing for UHPC square short column confined by non-helical stirrups could be calculated according to GB 50010-2010.
To study the calculation method of axial compressive bearing capacity for ultra-high performance concrete (UHPC) square short columns confined by high-strength stirrups. 9 UHPC square short columns confined by stirrups were tested under axial compression, and combined with the collected relevant literature data, the formula for calculating the peak stress of confined UHPC was given on the basis of Richart's failure criterion. And further suggested a calculation formula of axial compression bearing capacity, which was applicable to the high-strength stirrup confined UHPC square short columns with strength of UHPC ranging from 130 MPa to 180 MPa, steel fiber content ranging from 1.5% to 2% and volume stirrup ratio ranging from 1.5% to 5.5%; the suggested formula was compared with the standard formula of China and America. The results showed that the bearing capacity of UHPC predicted by GB 50010-2010 was more conservative than that of ACI 318-2014. The bearing capacity formula considered the effects of steel fiber bridge and stirrup restraint, and the calculated values were in good agreement with the test values. It was suggested to use high-strength stirrup above 600 MPa to restrain UHPC. The upper limit of the stirrup spacing for UHPC square short column confined by non-helical stirrups could be calculated according to GB 50010-2010.
2021, 51(2): 32-39,31.
doi: 10.13204/j.gyjzG20011704
Abstract:
A novel concrete composite slab was put forward by means of adding steel trusses and applying bilateral prestresses. The four specimens were tested to investigate the flexural behaviors of slabs influenced by the types of trusses. The failure modes, cracking loadings, loading deflection relationships and strain distributions, etc. were obtained by contrast experiments. The test results showed that the bilateral prestressed concrete precast panels present obviously bidirectional bending characteristics, and the bending stiffness, the cracking resistance, the bearing capacity and the ductile failure of precast panels were significantly improved due to adding steel trusses. In addition, precast panels with steel plate trusses, steel tube trusses and steel bar trusses all could meet the requirements of no supporting. By finite element parameter analysis, it was concluded that the height of trusses and the thickness of concrete had significant influence on the bending stiffness and the cracking resistance of precast panels. Meanwhile, the number of prestressing tendons had great effects on the cracking resistance but little influence on the bending stiffness.
A novel concrete composite slab was put forward by means of adding steel trusses and applying bilateral prestresses. The four specimens were tested to investigate the flexural behaviors of slabs influenced by the types of trusses. The failure modes, cracking loadings, loading deflection relationships and strain distributions, etc. were obtained by contrast experiments. The test results showed that the bilateral prestressed concrete precast panels present obviously bidirectional bending characteristics, and the bending stiffness, the cracking resistance, the bearing capacity and the ductile failure of precast panels were significantly improved due to adding steel trusses. In addition, precast panels with steel plate trusses, steel tube trusses and steel bar trusses all could meet the requirements of no supporting. By finite element parameter analysis, it was concluded that the height of trusses and the thickness of concrete had significant influence on the bending stiffness and the cracking resistance of precast panels. Meanwhile, the number of prestressing tendons had great effects on the cracking resistance but little influence on the bending stiffness.
2021, 51(2): 40-46.
doi: 10.13204/j.gyjzG20032702
Abstract:
In the prefabricated bridge structure, the existing socket connection between the prefabricated pier and the bearing platform has no reinforcement passing through the joint interface, which has the problem of insufficient bond performance. In the paper, a new type of interface connection was proposed, namely the interface embedded distributed steel fiber connection technique. In order to study the influence of this new type of joint on the bond performance of new and old concrete interface, double-sided shear test and axial tensile test were designed respectively, and six test conditions were formulated, including integral pouring of plain concrete, integral pouring of reinforced concrete, chiseled connection of C40-C40 interface, chiseled connection of UHPC-C40 interface, embedded wave-shaped/end-hook-shaped steel fiber connection of UHPC-C40 interface, and the shear and tensile capacity of the interface were tested. The results showed that the shear bearing capacity of the steel fiber connection specimen was significantly higher than that of the chiseling treatment and the whole pouring of plain concrete, which is up to 86.5% of the whole pouring of reinforced concrete; the tensile bearing capacity of the steel fiber connection specimen was also significantly improved, and the UHPC-C40 interface was not cracked when the specimen was broken. In this paper, the feasibility of embedded distributed steel fiber technique for UHPC-NC new and old interface was preliminarily verified, and the shear strength and tensile strength of the joint could be effectively improved.
In the prefabricated bridge structure, the existing socket connection between the prefabricated pier and the bearing platform has no reinforcement passing through the joint interface, which has the problem of insufficient bond performance. In the paper, a new type of interface connection was proposed, namely the interface embedded distributed steel fiber connection technique. In order to study the influence of this new type of joint on the bond performance of new and old concrete interface, double-sided shear test and axial tensile test were designed respectively, and six test conditions were formulated, including integral pouring of plain concrete, integral pouring of reinforced concrete, chiseled connection of C40-C40 interface, chiseled connection of UHPC-C40 interface, embedded wave-shaped/end-hook-shaped steel fiber connection of UHPC-C40 interface, and the shear and tensile capacity of the interface were tested. The results showed that the shear bearing capacity of the steel fiber connection specimen was significantly higher than that of the chiseling treatment and the whole pouring of plain concrete, which is up to 86.5% of the whole pouring of reinforced concrete; the tensile bearing capacity of the steel fiber connection specimen was also significantly improved, and the UHPC-C40 interface was not cracked when the specimen was broken. In this paper, the feasibility of embedded distributed steel fiber technique for UHPC-NC new and old interface was preliminarily verified, and the shear strength and tensile strength of the joint could be effectively improved.
2021, 51(2): 47-58,139.
doi: 10.13204/j.gyjzG20091702
Abstract:
Being aimed at a requirement to construct a large steel water tank containing 22 500 tons above ground, Sereral schemes were proposed. Through the analysis and comparisons of multiple schemes, the steel structure scheme of the tank was determined:the main structure was composed of trapezoidal cross section truss columns, multiple horizontal waist trusses and multiple capping trusses. The wall of the tank was made of continuous supporting arc-shaped steel plate to form a tension structure, which could effectively resist the effect of hydrostatic pressure and reduce the thickness of the steel plate. During the construction process, the trapezoidal cross section truss columns were first installed, then pre-tension was applied on the top of the truss columns and the cables were temporarily anchored, after that the horizontal waist trusses and capping trusses were installed, and finally the cables were removed and the curved wall plates were installed. This cable-free prestress scheme could make the internal force of the truss columns after the structure installed and the bending moment generated by the hydrostatic pressure cancel each other out, greatly reducing the stress level of the steel structure in normal use. On this basis, the dynamic characteristics of the overall steel structure tank and the main process load effects (wave-making, high-speed entry), etc. were studied. Based on a fluid-structure coupling analysis model of the tank, the time-history response of the seismic motion was studied. Finally, the hole opening scheme for the wall plate and numerical analysis results, as well as the design scheme of the foundation were given.
Being aimed at a requirement to construct a large steel water tank containing 22 500 tons above ground, Sereral schemes were proposed. Through the analysis and comparisons of multiple schemes, the steel structure scheme of the tank was determined:the main structure was composed of trapezoidal cross section truss columns, multiple horizontal waist trusses and multiple capping trusses. The wall of the tank was made of continuous supporting arc-shaped steel plate to form a tension structure, which could effectively resist the effect of hydrostatic pressure and reduce the thickness of the steel plate. During the construction process, the trapezoidal cross section truss columns were first installed, then pre-tension was applied on the top of the truss columns and the cables were temporarily anchored, after that the horizontal waist trusses and capping trusses were installed, and finally the cables were removed and the curved wall plates were installed. This cable-free prestress scheme could make the internal force of the truss columns after the structure installed and the bending moment generated by the hydrostatic pressure cancel each other out, greatly reducing the stress level of the steel structure in normal use. On this basis, the dynamic characteristics of the overall steel structure tank and the main process load effects (wave-making, high-speed entry), etc. were studied. Based on a fluid-structure coupling analysis model of the tank, the time-history response of the seismic motion was studied. Finally, the hole opening scheme for the wall plate and numerical analysis results, as well as the design scheme of the foundation were given.
2021, 51(2): 59-65,89.
doi: 10.13204/j.gyjzG21012710
Abstract:
A kind of Z-shaped all-bolted beam-to-column joint with double connection plates was proposed. The two specimens were designed by rigid connection philosophy in the paper. The quasi-static tests and finite element analysis were conducted for comparative study between the novel joint and conventional joint. The failure modes, hysteretic curves, skeleton curves, ductility factors, energy-dissipating capacities and anti-seismic performances were obtained. The results showed that the failure mode of Z-shaped beam-to-column bolted joint was the fracture on cantilever-beam flange connected to the column, and the web of the beam; the joints were rigidly and steadily connected, and there were no obvious sliding between the cover plates and the beam flanges; the dissipate energy mainly of specimens depended on the yield deformation; compared with the conventional joint, the Z-shaped joint possessed more stable hysteretic performance and larger displacement angle of failure; the bearing capacity of the novel joint was similar to the conventional joint, and its stiffness degradation trend was more low; the novel joint had a larger plastic development area, which could effectively improve the energy-dissipation performance, ductility and other seismic behaviors.
A kind of Z-shaped all-bolted beam-to-column joint with double connection plates was proposed. The two specimens were designed by rigid connection philosophy in the paper. The quasi-static tests and finite element analysis were conducted for comparative study between the novel joint and conventional joint. The failure modes, hysteretic curves, skeleton curves, ductility factors, energy-dissipating capacities and anti-seismic performances were obtained. The results showed that the failure mode of Z-shaped beam-to-column bolted joint was the fracture on cantilever-beam flange connected to the column, and the web of the beam; the joints were rigidly and steadily connected, and there were no obvious sliding between the cover plates and the beam flanges; the dissipate energy mainly of specimens depended on the yield deformation; compared with the conventional joint, the Z-shaped joint possessed more stable hysteretic performance and larger displacement angle of failure; the bearing capacity of the novel joint was similar to the conventional joint, and its stiffness degradation trend was more low; the novel joint had a larger plastic development area, which could effectively improve the energy-dissipation performance, ductility and other seismic behaviors.
2021, 51(2): 66-70,105.
doi: 10.13204/j.gyjzG201909100004
Abstract:
The assembled buckling-restrained brace, which resists axial loads by an inner plate brace while using outer assembled parts to provide the plate brace with lateral restraint, can be used in concentrically braced steel frames. Buckling analysis on the buckling-restrained brace in axial compression revealed that the effective length factors of brace could be obtain by considering critical load, length of brace, flexural rigidity of the restraining parts, etc. Nonlinear analysis revealed that the overall buckling of an assembled buckling-restrained brace had a peak load on the load-deformation curves, and the peak load was close to the load corresponding to the edge yielding of steel tube in outer assembled parts. Therefore, the overall buckling of brace under axial compression could be well evaluated by the edge yielding of restraining parts, and a correlation formula, which took into account initial crookedness, overstrength of the plate brace, flexural rigidity and strength of the restraining parts and clearance,could be provided to check the overall stability of brace.
The assembled buckling-restrained brace, which resists axial loads by an inner plate brace while using outer assembled parts to provide the plate brace with lateral restraint, can be used in concentrically braced steel frames. Buckling analysis on the buckling-restrained brace in axial compression revealed that the effective length factors of brace could be obtain by considering critical load, length of brace, flexural rigidity of the restraining parts, etc. Nonlinear analysis revealed that the overall buckling of an assembled buckling-restrained brace had a peak load on the load-deformation curves, and the peak load was close to the load corresponding to the edge yielding of steel tube in outer assembled parts. Therefore, the overall buckling of brace under axial compression could be well evaluated by the edge yielding of restraining parts, and a correlation formula, which took into account initial crookedness, overstrength of the plate brace, flexural rigidity and strength of the restraining parts and clearance,could be provided to check the overall stability of brace.
2021, 51(2): 71-75.
doi: 10.13204/j.gyjzG20021601
Abstract:
The finite element method was used to calibrate the release coefficient A and B of the hole-drilling method, and the results were compared with the test results under axial tension load. The results showed that it was feasible to use hole-drilling method to detect the working stress of axial tension member. The release coefficient A and B obtained by finite element calibration were in good agreement with the measured value under low stress state. The error caused by the plastic strain on the hole edge under high stress state could be modified according to the relationship between the distortion-energy parameter S and the release coefficient A and B. The cutting strain produced by drilling under loading state could be modified according to the measured relationship between the cutting strain and the released strain.
The finite element method was used to calibrate the release coefficient A and B of the hole-drilling method, and the results were compared with the test results under axial tension load. The results showed that it was feasible to use hole-drilling method to detect the working stress of axial tension member. The release coefficient A and B obtained by finite element calibration were in good agreement with the measured value under low stress state. The error caused by the plastic strain on the hole edge under high stress state could be modified according to the relationship between the distortion-energy parameter S and the release coefficient A and B. The cutting strain produced by drilling under loading state could be modified according to the measured relationship between the cutting strain and the released strain.
2021, 51(2): 76-82.
doi: 10.13204/j.gyjzG19102701
Abstract:
Due to the different material characteristics of steel and concrete with time, there will be vertical deformation difference between the outer steel frame column and the inner concrete core tube in the construction process of hybrid structure combined with diagrid steel frame and concrete core tube, and excessive deformation difference will affect the construction quality and structural safety. Considering the time-varying effect of the construction process, the finite element analysis model was established by the method of variable stiffness stage by stage to simulate the whole construction process. The analysis results showed that with the construction process, the vertical deformation value and vertical deformation difference of the diagrid column, frame and concrete core tube increased, and the deformation growth rate was slow first, then fast and then slow. According to the numerical simulation results of the whole model and the deformation diagram of the diagrad column, the processing control compensation of the component was obtained. The leveling quantity of concrete core tube was proposed by piecewise accumulation leveling method.
Due to the different material characteristics of steel and concrete with time, there will be vertical deformation difference between the outer steel frame column and the inner concrete core tube in the construction process of hybrid structure combined with diagrid steel frame and concrete core tube, and excessive deformation difference will affect the construction quality and structural safety. Considering the time-varying effect of the construction process, the finite element analysis model was established by the method of variable stiffness stage by stage to simulate the whole construction process. The analysis results showed that with the construction process, the vertical deformation value and vertical deformation difference of the diagrid column, frame and concrete core tube increased, and the deformation growth rate was slow first, then fast and then slow. According to the numerical simulation results of the whole model and the deformation diagram of the diagrad column, the processing control compensation of the component was obtained. The leveling quantity of concrete core tube was proposed by piecewise accumulation leveling method.
2021, 51(2): 83-89.
doi: 10.13204/j.gyjzG201907090002
Abstract:
In order to study the influencing factors of the external prestressing incremental change of the composite box girder with corrugated steel webs during bending failure process, the destructive model test of the bending capacity was carried out, and the finite element model was established. Based on the comparisons of experimental data and finite element theoretical values, the validity of the numerical model was verified. The influence of various parameters on the external prestress increment was carried out according to the numerical model. The research showed that the effects of concrete strength on the stress increment of external prestressed tendons was positively correlated; the effects of reinforcement ratio and strength of the normal steel bar, initial effective stress, external prestressing tendon area and shear-span ratio in the tension zone on the stsress increment of external prestressed tendons was negatively correlated; the thickness of the corrugated steel web and the yield strength, and the closest distance from the loading point to the support had little effect on the stress increment of the external prestressed tendons.
In order to study the influencing factors of the external prestressing incremental change of the composite box girder with corrugated steel webs during bending failure process, the destructive model test of the bending capacity was carried out, and the finite element model was established. Based on the comparisons of experimental data and finite element theoretical values, the validity of the numerical model was verified. The influence of various parameters on the external prestress increment was carried out according to the numerical model. The research showed that the effects of concrete strength on the stress increment of external prestressed tendons was positively correlated; the effects of reinforcement ratio and strength of the normal steel bar, initial effective stress, external prestressing tendon area and shear-span ratio in the tension zone on the stsress increment of external prestressed tendons was negatively correlated; the thickness of the corrugated steel web and the yield strength, and the closest distance from the loading point to the support had little effect on the stress increment of the external prestressed tendons.
2021, 51(2): 90-97.
doi: 10.13204/j.gyjzG20020102
Abstract:
In order to study the mechanic properties of steel reinforced concrete beams under flexural-torsional condition, the monotonic loading tests of 12 steel reinforced concrete beams and 1 reinforced concrete beam were conducted. The failure patterns and torque-torsion ratio curves were studied and damage evolution was analyzed under bending and torsion. The results showed that the entire process of load-bearing in all specimens under bending and torsion could be divided into three stages which were elastic, elasto-plastic and failure stages. The smaller torsion-bending ratio were, the earlier the cracks appeared in the solid-web steel reinforced concrete beams. Stirrup ratio had no significant effect on the increase of cracking torque. The failure patterns of angle steel truss reinforced concrete beams had two types:failure with flexural feature and failure with torsional feature. Before cracking, the torsional resistance performance of the specimens under bending and torsion depended not only on the tensile strength of the concrete, but also on the torsional rigidity of the steel. The damage degree of specimens also presented three stage features, and the damage degree of reinforced concrete beams was larger than that of steel reinforced concrete beams. The influence of concrete strength on the later damage of the specimen was very small. With the increase of the Ι-steel model, the constraint on the surrounding concrete became smaller and more unfavorable to torsion.
In order to study the mechanic properties of steel reinforced concrete beams under flexural-torsional condition, the monotonic loading tests of 12 steel reinforced concrete beams and 1 reinforced concrete beam were conducted. The failure patterns and torque-torsion ratio curves were studied and damage evolution was analyzed under bending and torsion. The results showed that the entire process of load-bearing in all specimens under bending and torsion could be divided into three stages which were elastic, elasto-plastic and failure stages. The smaller torsion-bending ratio were, the earlier the cracks appeared in the solid-web steel reinforced concrete beams. Stirrup ratio had no significant effect on the increase of cracking torque. The failure patterns of angle steel truss reinforced concrete beams had two types:failure with flexural feature and failure with torsional feature. Before cracking, the torsional resistance performance of the specimens under bending and torsion depended not only on the tensile strength of the concrete, but also on the torsional rigidity of the steel. The damage degree of specimens also presented three stage features, and the damage degree of reinforced concrete beams was larger than that of steel reinforced concrete beams. The influence of concrete strength on the later damage of the specimen was very small. With the increase of the Ι-steel model, the constraint on the surrounding concrete became smaller and more unfavorable to torsion.
2021, 51(2): 98-105.
doi: 10.13204/j.gyjzG201904040008
Abstract:
Public transit-oriented developement is a hot spot in urban construction. The commercial complex over the subway station is one of the key in frastructures, and the design of SRC abnormal joints for the structure cannot be directly guided by JGJ 138-2016. In order to study the failure mode of the SRC abnormal joints and the influence of the variation of beam-column section on its shear capacity, based on the SRC abnormal joints in the conversion layer of a subway vehicle base, a 1/4 scaled abnormal joint was designed and fabricated according to the principle of "strong component, weak joint", and quasi-static loading test was carried out on it. At the same time, taking the relative size of beam-column section as the research parameter, the finite element model of 7 groups of abnormal joints was established and analyzed by ABAQUS program to study the shear mechanism of the core region. The formulae of the shear capacity were proposed and the variation trend of shear capacity of joint core region was explored. The results showed that within the range of SRC beam-column size, increasing the section width of the RC beam and the section height of the RC column were beneficial to the shear performance of the joint core area. When the section width ratio of RC beam to SRC beam was increased from 0.6 to 1.0, the shear capacity of the core area increased by 12%. When the height ratio of the RC column to the SRC column section was increased from 0.5 to 1.0, the shear capacity of the core area increased by 10%. However, increasing the height of the RC beam would cause the concrete strut in the core area to be too steep, which was not conducive to its shear resistance. When the height ratio of RC beam to SRC beam section increased from 0.75 to 1.0, the shear capacity of the core area decreased by 5%.
Public transit-oriented developement is a hot spot in urban construction. The commercial complex over the subway station is one of the key in frastructures, and the design of SRC abnormal joints for the structure cannot be directly guided by JGJ 138-2016. In order to study the failure mode of the SRC abnormal joints and the influence of the variation of beam-column section on its shear capacity, based on the SRC abnormal joints in the conversion layer of a subway vehicle base, a 1/4 scaled abnormal joint was designed and fabricated according to the principle of "strong component, weak joint", and quasi-static loading test was carried out on it. At the same time, taking the relative size of beam-column section as the research parameter, the finite element model of 7 groups of abnormal joints was established and analyzed by ABAQUS program to study the shear mechanism of the core region. The formulae of the shear capacity were proposed and the variation trend of shear capacity of joint core region was explored. The results showed that within the range of SRC beam-column size, increasing the section width of the RC beam and the section height of the RC column were beneficial to the shear performance of the joint core area. When the section width ratio of RC beam to SRC beam was increased from 0.6 to 1.0, the shear capacity of the core area increased by 12%. When the height ratio of the RC column to the SRC column section was increased from 0.5 to 1.0, the shear capacity of the core area increased by 10%. However, increasing the height of the RC beam would cause the concrete strut in the core area to be too steep, which was not conducive to its shear resistance. When the height ratio of RC beam to SRC beam section increased from 0.75 to 1.0, the shear capacity of the core area decreased by 5%.
2021, 51(2): 106-112,129.
doi: 10.13204/j.gyjzG20032605
Abstract:
The early dismantling of temporary supports is a key step in the construction process of most space steel structures. To ensure the smooth progress of the unloading process, it is necessary to conduct a theoretical analysis of the dismantling plan and real-time monitoring of stress and deformation during the dismantling process. The space curved steel structure of the National Cyber Security Talent and Innovation Base Exhibition Center was taken as an example. For this structure with peculiar shapes and the first in China, three dismantling for temporary supports early schemes were proposed for simulation analysis, including one-way successive dismantling, the order of dismantling from the outside to the inside and dismantling from the inside to the outside was simulated and calculated in sequence. The results showed that the structure had the best overall performance when dismantling from the inside to the outside. The stress and deformation data monitored during the actual dismantling process were compared with comparative analysis of theoretical values. The results of stress and deformation changed during actual dismantling were close to the theoretical analysis results. This dismantling scheme was safe and reliable, and could provide a reference for dismantling the temporary supports of similar space steel structures.
The early dismantling of temporary supports is a key step in the construction process of most space steel structures. To ensure the smooth progress of the unloading process, it is necessary to conduct a theoretical analysis of the dismantling plan and real-time monitoring of stress and deformation during the dismantling process. The space curved steel structure of the National Cyber Security Talent and Innovation Base Exhibition Center was taken as an example. For this structure with peculiar shapes and the first in China, three dismantling for temporary supports early schemes were proposed for simulation analysis, including one-way successive dismantling, the order of dismantling from the outside to the inside and dismantling from the inside to the outside was simulated and calculated in sequence. The results showed that the structure had the best overall performance when dismantling from the inside to the outside. The stress and deformation data monitored during the actual dismantling process were compared with comparative analysis of theoretical values. The results of stress and deformation changed during actual dismantling were close to the theoretical analysis results. This dismantling scheme was safe and reliable, and could provide a reference for dismantling the temporary supports of similar space steel structures.
2021, 51(2): 113-120.
doi: 10.13204/j.gyjzG19112110
Abstract:
As one of the evaluation indexes of structural seismic performance level, displacement angle has been widely applied in specifications at home and abroad. In order to study the relationship between maximum displacement angle and the seismic performance level about wooden frame with partition board, three groups of 1:2 scale models were fabricated according to "Engineering Practice Rule" by the Ministry of Work in the Qing dynasty,and quasi-static tests were carried out. The failure characteristics and mechanical properties of wooden frame with partition board under horizontal reciprocating load were obtained. According to the data obtained by ABAQUS finite element simulation, based on the analysis of the composition of the partition board and its value occurrence form, the seismic performance level of the non-structural member was combined. Considering the influence of cultural relic value and component damage degree on the seismic performance of the partition board, the displacement angle reference limit of the wooden frame with partition at different seismic performance levels was given.
As one of the evaluation indexes of structural seismic performance level, displacement angle has been widely applied in specifications at home and abroad. In order to study the relationship between maximum displacement angle and the seismic performance level about wooden frame with partition board, three groups of 1:2 scale models were fabricated according to "Engineering Practice Rule" by the Ministry of Work in the Qing dynasty,and quasi-static tests were carried out. The failure characteristics and mechanical properties of wooden frame with partition board under horizontal reciprocating load were obtained. According to the data obtained by ABAQUS finite element simulation, based on the analysis of the composition of the partition board and its value occurrence form, the seismic performance level of the non-structural member was combined. Considering the influence of cultural relic value and component damage degree on the seismic performance of the partition board, the displacement angle reference limit of the wooden frame with partition at different seismic performance levels was given.
2021, 51(2): 121-129.
doi: 10.13204/j.gyjzG20052007
Abstract:
Based on the dynamic governing equations of unsaturated soil, the horizontal transient response of a single pile in unsaturated soil was analyzed. By using the Laplace Transform and method of normalization, the horizontal wave equations of transform domains in unsaturated soil were established. By the method of separation variables and the operator-decomposition theory, the displacement solutions of unsaturated soil in the Laplace Transform Domain were obtained. To solve the soil-pile coupling system, the horizontal vibration equations of pile foundations and the continuity conditions were both adopted, and then the Laplace Transform's expressions of the displacement and internal forces of piles were obtained. By numerical calculation of Laplace's inverse transforms, the effects of the degrees of saturation, pile-soil modulus ratios and load duration on dynamic responses of piles were studied. The results showed that:the degrees of saturation influenced the displacement and internal forces of piles to some extents. The larger pile-soil modulus ratios, the influence of degrees of saturation on piles more significant. The longer the duration of impact loads, the greater the pile displacement, and the more the lag of the peak displacement.
Based on the dynamic governing equations of unsaturated soil, the horizontal transient response of a single pile in unsaturated soil was analyzed. By using the Laplace Transform and method of normalization, the horizontal wave equations of transform domains in unsaturated soil were established. By the method of separation variables and the operator-decomposition theory, the displacement solutions of unsaturated soil in the Laplace Transform Domain were obtained. To solve the soil-pile coupling system, the horizontal vibration equations of pile foundations and the continuity conditions were both adopted, and then the Laplace Transform's expressions of the displacement and internal forces of piles were obtained. By numerical calculation of Laplace's inverse transforms, the effects of the degrees of saturation, pile-soil modulus ratios and load duration on dynamic responses of piles were studied. The results showed that:the degrees of saturation influenced the displacement and internal forces of piles to some extents. The larger pile-soil modulus ratios, the influence of degrees of saturation on piles more significant. The longer the duration of impact loads, the greater the pile displacement, and the more the lag of the peak displacement.
2021, 51(2): 130-134.
doi: 10.13204/j.gyjzG19121006
Abstract:
Taking geocell-reinforced saturated sand as research objects, the change laws of dynamic moduli of deformation, damping ratios of geocell-reinforced saturated sand with different reinforcement layers, geocell height, confining pressure and dynamic strain were studied. It was shown that the dynamic strain increased with the increase of dynamic stress in the same working condition, the increase of reinforcement contents could most obviously restrain the increase of dynamic strain. With the dynamic strain increase, the dynamic moduli of deformation decreased in the same working condition subjected to different confining pressure, the dynamic moduli of deformation under high confining pressure was larger. The damping ratios under the same working condition had no obvious rule with the increase of dynamic strain. The damping ratios under different working conditions decreased with the increase of dynamic strain subjected to confining pressure of 50 kPa and it tended to be contant after the dynamic strain exceeded a certain value.
Taking geocell-reinforced saturated sand as research objects, the change laws of dynamic moduli of deformation, damping ratios of geocell-reinforced saturated sand with different reinforcement layers, geocell height, confining pressure and dynamic strain were studied. It was shown that the dynamic strain increased with the increase of dynamic stress in the same working condition, the increase of reinforcement contents could most obviously restrain the increase of dynamic strain. With the dynamic strain increase, the dynamic moduli of deformation decreased in the same working condition subjected to different confining pressure, the dynamic moduli of deformation under high confining pressure was larger. The damping ratios under the same working condition had no obvious rule with the increase of dynamic strain. The damping ratios under different working conditions decreased with the increase of dynamic strain subjected to confining pressure of 50 kPa and it tended to be contant after the dynamic strain exceeded a certain value.
2021, 51(2): 135-139.
doi: 10.13204/j.gyjzG19041801
Abstract:
The determination on laying parameters of geotextile is one of the key contents in design of reinforced soil walls. In order to make full use of the reinforcement performances, based on the variable coefficient method of earth pressure and the 0.3H(H represents the height of the retaining wall) potential failure mode, the relations between reinforcement spacings and reinforcement length were analyzed, the calculation method of reinforcement lengths with a certain reinforcement spacing or reinforcement spacings with a constant reinforcement length was established, the reinforcement consumption was analyzed through a calculation example in which the reinforced soil wall was designed by different reinforced methods. The results showed that:when reinforcement spacing was invariable, the anchorage length of reinforcement was proportional to the coefficient of the earth pressure at the depth of the reinforcement; when the reinforcement anchorage length was constant, the reinforcement spacing was inversely proportional to the coefficient of the earth pressure at the depth of the reinforcement; compared with the traditional equal length method, the two methods proposed in the paper were of obvious economic advantages, and the higher the retaining wall, the greater the saving of reinforcement.
The determination on laying parameters of geotextile is one of the key contents in design of reinforced soil walls. In order to make full use of the reinforcement performances, based on the variable coefficient method of earth pressure and the 0.3H(H represents the height of the retaining wall) potential failure mode, the relations between reinforcement spacings and reinforcement length were analyzed, the calculation method of reinforcement lengths with a certain reinforcement spacing or reinforcement spacings with a constant reinforcement length was established, the reinforcement consumption was analyzed through a calculation example in which the reinforced soil wall was designed by different reinforced methods. The results showed that:when reinforcement spacing was invariable, the anchorage length of reinforcement was proportional to the coefficient of the earth pressure at the depth of the reinforcement; when the reinforcement anchorage length was constant, the reinforcement spacing was inversely proportional to the coefficient of the earth pressure at the depth of the reinforcement; compared with the traditional equal length method, the two methods proposed in the paper were of obvious economic advantages, and the higher the retaining wall, the greater the saving of reinforcement.
2021, 51(2): 140-145,205.
doi: 10.13204/j.gyjzG20031408
Abstract:
In order to achieve feedback optimization of parameters under tunnel construction in rich water zones, a feedback analysis method for tunnel parameters in fluid-solid coupling conditions was established based on the machine learning and intelligent optimization algorithm. Firstly, the numerical calculation model was modelled and solved by the fluid-solid coupling model. The displacement of adjoining rock and the distribution of pore water pressure in different combination of rock parameters were obtained by orthogonal design analysis, and the learning samples for machine learning were established, in which the input group was consisted of a set of rock parameters and the output group was consisted of adjoining rock displacement and pore water pressure. Then, Gaussian Regression Process was used to obtain the non-linear mapping relation contained the learning samples, and differential evolution algorithm was used to optimize the key parameters involved in the process. Furthermore, according to the established regression model and the measured displacement and pore water pressure in the target zone, the differential evolution algorithm was used to optimize the rock parameters and the parameter feedback analysis results were obtained. Finally, the inverse values were compared with the actual measured values, and the reliability of the adjoining rock parameters obtained from the feedback analysis was verified.
In order to achieve feedback optimization of parameters under tunnel construction in rich water zones, a feedback analysis method for tunnel parameters in fluid-solid coupling conditions was established based on the machine learning and intelligent optimization algorithm. Firstly, the numerical calculation model was modelled and solved by the fluid-solid coupling model. The displacement of adjoining rock and the distribution of pore water pressure in different combination of rock parameters were obtained by orthogonal design analysis, and the learning samples for machine learning were established, in which the input group was consisted of a set of rock parameters and the output group was consisted of adjoining rock displacement and pore water pressure. Then, Gaussian Regression Process was used to obtain the non-linear mapping relation contained the learning samples, and differential evolution algorithm was used to optimize the key parameters involved in the process. Furthermore, according to the established regression model and the measured displacement and pore water pressure in the target zone, the differential evolution algorithm was used to optimize the rock parameters and the parameter feedback analysis results were obtained. Finally, the inverse values were compared with the actual measured values, and the reliability of the adjoining rock parameters obtained from the feedback analysis was verified.
2021, 51(2): 146-152.
doi: 10.13204/j.gyjzG20090711
Abstract:
A method for identifying ice front in seasonally frozen soils based on parallel plate capacitors was proposed to realize non-contact identification of the ice front structure based on analysis of variable structure laws and physico-mechanical properties of seasonally frozen soils. Particularly, a mathematical model was proposed for the relations of the capacitance and temperature of frozen soils based on the Boltzmann function, in which temperature variations of seasonally frozen soils were simulated to obtain capacitance responses in seasonally frozen soils at different temperatures. The results indicated that capacitance was gradually increased with temperatures and approached a constant value at a certain temperature. It was found that capacitance varied rapidly in the range of -4 to 4℃ and when temperatures of seasonally frozen soils were out of that range,it basically remained constant. The experiment showed that the developed method could efficiently determine ice front structure and obtain the variation trends of seasonally frozen soils within errors of 10% in the frozen, ice front and melted zones.
A method for identifying ice front in seasonally frozen soils based on parallel plate capacitors was proposed to realize non-contact identification of the ice front structure based on analysis of variable structure laws and physico-mechanical properties of seasonally frozen soils. Particularly, a mathematical model was proposed for the relations of the capacitance and temperature of frozen soils based on the Boltzmann function, in which temperature variations of seasonally frozen soils were simulated to obtain capacitance responses in seasonally frozen soils at different temperatures. The results indicated that capacitance was gradually increased with temperatures and approached a constant value at a certain temperature. It was found that capacitance varied rapidly in the range of -4 to 4℃ and when temperatures of seasonally frozen soils were out of that range,it basically remained constant. The experiment showed that the developed method could efficiently determine ice front structure and obtain the variation trends of seasonally frozen soils within errors of 10% in the frozen, ice front and melted zones.
2021, 51(2): 153-157.
doi: 10.13204/j.gyjzG20042010
Abstract:
Graphene oxide nanosheets (GONPs) have unique physical properties, making them effective reinforcing materials. The effects of different amounts of GONPs on the mechanical properties, pore size distribution and microstructure characteristics of cement-based composites were studied in this paper. GONPs prepared cement-based composites at 0%, 0.01%, 0.02%, 0.03%, 0.04%, and 0.05% of the cement mass fraction. The compressive strength and indirect tensile strength of the samples were measured at the 28-day age, as well as thermogravimetric analysis (TGA) and X-ray diffraction analysis; nitrogen adsorption technique was used to study the pore size distribution of the fracture surface of the sample and the microstructure was observed by scanning electron microscopy (SEM). The results showed that by incorporating GONPs into cement-based composites, the maximum compressive strength and indirect tensile strength could be increased by 13% and 41%, respectively. The combination of GONPs and ordinary Portland cement (OPC) significantly reduced the pore size of cement mortar, significantly improved its microstructure, and improved the mechanical properties of cement-based composites.
Graphene oxide nanosheets (GONPs) have unique physical properties, making them effective reinforcing materials. The effects of different amounts of GONPs on the mechanical properties, pore size distribution and microstructure characteristics of cement-based composites were studied in this paper. GONPs prepared cement-based composites at 0%, 0.01%, 0.02%, 0.03%, 0.04%, and 0.05% of the cement mass fraction. The compressive strength and indirect tensile strength of the samples were measured at the 28-day age, as well as thermogravimetric analysis (TGA) and X-ray diffraction analysis; nitrogen adsorption technique was used to study the pore size distribution of the fracture surface of the sample and the microstructure was observed by scanning electron microscopy (SEM). The results showed that by incorporating GONPs into cement-based composites, the maximum compressive strength and indirect tensile strength could be increased by 13% and 41%, respectively. The combination of GONPs and ordinary Portland cement (OPC) significantly reduced the pore size of cement mortar, significantly improved its microstructure, and improved the mechanical properties of cement-based composites.
2021, 51(2): 158-165.
doi: 10.13204/j.gyjzG20032908
Abstract:
Ceramic powder is used as an admixture to replace cement, and then mixed with mineral powder to prepare concrete. The mass, compressive strength and dynamic elastic modulus of concrete were determined to analyze the frost resistance after 25 freeze-thaw cycles. The freeze-thaw damage model was established to forecast durability life. Nuclear magnetic resonance (NMR) test was carried out to analyze the microporosity characteristics of concrete after freeze-thaw cycles. The grey entropy analysis was introduced to link micro-pore structure with concrete durability, and the main factors affecting the frost resistance of the concrete mixed with ceramic powder were obtained pore structure to frost resistance. On this basis, the prediction model of compressive strength after freeze-thaw cycles was established.The results showed that the loss of mass, compressive strength and dynamic elasticity modulus of concrete mixed with ceramic powder was less at the later stage of freeze-thaw cycles. The maximum durability frost-resistant life could reach 32 years. T2 spectrum area, porosity, free fluid saturation and larger size pore ratio increased with freeze-thaw cycles.The addition of ceramic powder could reduce the deterioration of pore structure.The pore characteristic parameters that mainly affected the frost resistance of ceramic powder concrete were porosity, bound fluid saturation and the pore size of 0.05 to 0.2 μm, and the average relative error of the GM model was 4.43%.
Ceramic powder is used as an admixture to replace cement, and then mixed with mineral powder to prepare concrete. The mass, compressive strength and dynamic elastic modulus of concrete were determined to analyze the frost resistance after 25 freeze-thaw cycles. The freeze-thaw damage model was established to forecast durability life. Nuclear magnetic resonance (NMR) test was carried out to analyze the microporosity characteristics of concrete after freeze-thaw cycles. The grey entropy analysis was introduced to link micro-pore structure with concrete durability, and the main factors affecting the frost resistance of the concrete mixed with ceramic powder were obtained pore structure to frost resistance. On this basis, the prediction model of compressive strength after freeze-thaw cycles was established.The results showed that the loss of mass, compressive strength and dynamic elasticity modulus of concrete mixed with ceramic powder was less at the later stage of freeze-thaw cycles. The maximum durability frost-resistant life could reach 32 years. T2 spectrum area, porosity, free fluid saturation and larger size pore ratio increased with freeze-thaw cycles.The addition of ceramic powder could reduce the deterioration of pore structure.The pore characteristic parameters that mainly affected the frost resistance of ceramic powder concrete were porosity, bound fluid saturation and the pore size of 0.05 to 0.2 μm, and the average relative error of the GM model was 4.43%.
2021, 51(2): 166-170.
doi: 10.13204/j.gyjzG201906200004
Abstract:
In order to explore the multiaxial high-cycle fatigue performances of welded members of steel pipe, the uniaxial tensile and torsional high-cycle fatigue tests of welded members of steel pipe were designed to obtain the stress-life curve (S-N curve) and fatigue parameters of welded members of steel pipe. On this basis, the modified Wöhler curve method(MWCM) based on critical surface theory was adopted to analyze the multiaxial high-cycle fatigue performances of welded members.The results showed that the uniaxial high-cycle fatigue performances of welded members of steel pipe was much lower than that of base metal with the same strength. With the increase of the ratio of normal stress amplitude to shear stress amplitude on fatigue critical plane, the fatigue life curve kept moving downward and the fatigue strength decreased. When the ratio of normal stress amplitude to shear stress amplitude on the critical plane remained constant, the multiaxial fatigue life decreased with the increase of shear stress amplitude on the critical plane. When the shear stress amplitude on the critical plane remained unchanged, the multiaxial fatigue life decreased with the increase of the normal stress amplitude on the critical plane.
In order to explore the multiaxial high-cycle fatigue performances of welded members of steel pipe, the uniaxial tensile and torsional high-cycle fatigue tests of welded members of steel pipe were designed to obtain the stress-life curve (S-N curve) and fatigue parameters of welded members of steel pipe. On this basis, the modified Wöhler curve method(MWCM) based on critical surface theory was adopted to analyze the multiaxial high-cycle fatigue performances of welded members.The results showed that the uniaxial high-cycle fatigue performances of welded members of steel pipe was much lower than that of base metal with the same strength. With the increase of the ratio of normal stress amplitude to shear stress amplitude on fatigue critical plane, the fatigue life curve kept moving downward and the fatigue strength decreased. When the ratio of normal stress amplitude to shear stress amplitude on the critical plane remained constant, the multiaxial fatigue life decreased with the increase of shear stress amplitude on the critical plane. When the shear stress amplitude on the critical plane remained unchanged, the multiaxial fatigue life decreased with the increase of the normal stress amplitude on the critical plane.
2021, 51(2): 171-185,152.
doi: 10.13204/j.gyjzG20040805
Abstract:
Prefabricated concrete frame structures have been widely used and received a lot of attention from home and aboard scholars. Seismic damage investigations show that the seismic performance of prefabricated frame structures depends on the connection joints. The paper reviewed the research progress on the seismic performance of the connection joints of prefabricated concrete frame structures at home and aboard. The common used connection types, configurations and seismic test results of the connection joints were reviewed. A brief review on the seismic performance of beam-beam joints, column-column joints and beam-slab joints was proposed. The advantages, disadvantages and improving method of several configurations of the beam-column joints were pointed out. Finally, the further issues of the connection joints of the prefabricated concrete frame structures were discussed.
Prefabricated concrete frame structures have been widely used and received a lot of attention from home and aboard scholars. Seismic damage investigations show that the seismic performance of prefabricated frame structures depends on the connection joints. The paper reviewed the research progress on the seismic performance of the connection joints of prefabricated concrete frame structures at home and aboard. The common used connection types, configurations and seismic test results of the connection joints were reviewed. A brief review on the seismic performance of beam-beam joints, column-column joints and beam-slab joints was proposed. The advantages, disadvantages and improving method of several configurations of the beam-column joints were pointed out. Finally, the further issues of the connection joints of the prefabricated concrete frame structures were discussed.
2021, 51(2): 186-192,120.
doi: 10.13204/j.gyjzG20042507
Abstract:
Seawater-coral aggregate concrete has become a new type of building material for constructions in islands and reefs,supporting the development of ocean exploration in China. Based on the stage divisions of whole life cycle of seawater-coral aggregate concrete structures,the influences of salinity in seawater on early-age hydration of cement were summarized. A concept of two-level transmission routes through coral aggregate and cement matrix respectively was proposed. The main mechanism of mineral corrosion and the damage and destruction process under mitigation were reviewed. Main gaps and suggested key issues were expected to be valuable for future researches on the durability problem of seawater-coral aggregate concrete.
Seawater-coral aggregate concrete has become a new type of building material for constructions in islands and reefs,supporting the development of ocean exploration in China. Based on the stage divisions of whole life cycle of seawater-coral aggregate concrete structures,the influences of salinity in seawater on early-age hydration of cement were summarized. A concept of two-level transmission routes through coral aggregate and cement matrix respectively was proposed. The main mechanism of mineral corrosion and the damage and destruction process under mitigation were reviewed. Main gaps and suggested key issues were expected to be valuable for future researches on the durability problem of seawater-coral aggregate concrete.
2021, 51(2): 193-198.
doi: 10.13204/j.gyjzG20010706
Abstract:
Through the axial compression test of one RC square-section short column and four RC square-section short columns strengthened with composite reinforcement, the axial compression performance of the damaged RC square-section short column strengthened with GFRP sleeve and steel fiber mortar was studied. The restraint effect of GFRP strips on RC columns strengthened with steel fiber mortar was analyzed; under different damage conditions, the bearing capacity, stiffness and ductility of RC columns strengthened with GFRP strips and steel fiber mortar were analyzed. The test results showed that GFRP strip could significantly improve the bearing capacity and ductility of RC columns strengthened with steel fiber mortar; the bearing capacity of damaged RC columns was significantly improved after GFRP strip and steel fiber mortar composite reinforcement, under the same conditions, the improvement rate of the bearing capacity of the composite reinforced column decreaseed with the increase of the degree of damaged RC columns, and the reinforcement effect was obvious in a certain degree, the reinforcement effect was weakened beyond this degree of damage. The axial compression stiffness of the specimen decreased with the increase of damage degree.On the basis of experimental study, the calculation formula of axial bearing capacity of composite reinforced RC short column with square-section was established,and the results were in good agreement with the experimental data.
Through the axial compression test of one RC square-section short column and four RC square-section short columns strengthened with composite reinforcement, the axial compression performance of the damaged RC square-section short column strengthened with GFRP sleeve and steel fiber mortar was studied. The restraint effect of GFRP strips on RC columns strengthened with steel fiber mortar was analyzed; under different damage conditions, the bearing capacity, stiffness and ductility of RC columns strengthened with GFRP strips and steel fiber mortar were analyzed. The test results showed that GFRP strip could significantly improve the bearing capacity and ductility of RC columns strengthened with steel fiber mortar; the bearing capacity of damaged RC columns was significantly improved after GFRP strip and steel fiber mortar composite reinforcement, under the same conditions, the improvement rate of the bearing capacity of the composite reinforced column decreaseed with the increase of the degree of damaged RC columns, and the reinforcement effect was obvious in a certain degree, the reinforcement effect was weakened beyond this degree of damage. The axial compression stiffness of the specimen decreased with the increase of damage degree.On the basis of experimental study, the calculation formula of axial bearing capacity of composite reinforced RC short column with square-section was established,and the results were in good agreement with the experimental data.
ECCENTRIC COMPRESSION TESTS AND CALCULATION METHODS OF RC STUB COLUMNS STRENGTHENED WITH STEEL TUBES
2021, 51(2): 199-205.
doi: 10.13204/j.gyjzG19120703
Abstract:
In order to revealed the performances and mechanical mechanism of the RC stub columns strengthened with steel tubes (RCSST) under eccentric compression, a series of tests including ten eccentrically loaded RC stub columns strengthened with steel tubes was conducted. The effects of parameters such as eccentricity along the long and short axis, the core concrete area ratios on the performances were analyzed. The change laws of the experimental phenomena, the failure modes, the ultimate strength, the displacement ductility coefficients and the strength enhancement indexes were respectively studied. Moreover, the mechanical mechanism of the eccentrically loaded RCSST stub columns were revealed through the analysis of the relationships between the vertical force and axial displacement, and the vertical force and strain. The design formulae for predicting the eccentric compressive strength of the RC stub columns strengthened with steel tube was proposed. The experimental results showed that the failure modes of the columns mainly included the local buckling of the steel tube, the fracture of the weld, the crushing of the grouting material and the buckling of the longitudinal rebar. The eccentric compressive strength of the column was enhanced with the decrease of eccentricity and the area ratio of core concrete, and the ductility was significant improved with the increase of eccentricity and the area ratio of core concrete.
In order to revealed the performances and mechanical mechanism of the RC stub columns strengthened with steel tubes (RCSST) under eccentric compression, a series of tests including ten eccentrically loaded RC stub columns strengthened with steel tubes was conducted. The effects of parameters such as eccentricity along the long and short axis, the core concrete area ratios on the performances were analyzed. The change laws of the experimental phenomena, the failure modes, the ultimate strength, the displacement ductility coefficients and the strength enhancement indexes were respectively studied. Moreover, the mechanical mechanism of the eccentrically loaded RCSST stub columns were revealed through the analysis of the relationships between the vertical force and axial displacement, and the vertical force and strain. The design formulae for predicting the eccentric compressive strength of the RC stub columns strengthened with steel tube was proposed. The experimental results showed that the failure modes of the columns mainly included the local buckling of the steel tube, the fracture of the weld, the crushing of the grouting material and the buckling of the longitudinal rebar. The eccentric compressive strength of the column was enhanced with the decrease of eccentricity and the area ratio of core concrete, and the ductility was significant improved with the increase of eccentricity and the area ratio of core concrete.
2021, 51(2): 206-210,198.
doi: 10.13204/j.gyjzG20092701
Abstract:
The soil between tunnelled spaces and bridge abutments was supported and reinforced by grouted with composite bolt piles to ensure security and stability of a long-span cable-stayed bridge before tunnelling a underground light rail station along sides of pile founndations of the bridge with pile-beam-arch (PBA) method. The settlement of piles and the structural internal forces of the bridge before and after grouted reinforcement were studied by FEA. The results showed that the maximum settlement of piles occurred at the end of tunnelling the upper soil strata of the station. After grouted reinforcement, the loose range and plastic range around the tunnelled surface were reduced. The settlement of piles was reduced by 28. 7% compared with that of the unreinforced state. The calculation results showed that the bridge structure could meet the specification requirements in the ultimate bearing capacity and normal service state considering displacement of bearings.
The soil between tunnelled spaces and bridge abutments was supported and reinforced by grouted with composite bolt piles to ensure security and stability of a long-span cable-stayed bridge before tunnelling a underground light rail station along sides of pile founndations of the bridge with pile-beam-arch (PBA) method. The settlement of piles and the structural internal forces of the bridge before and after grouted reinforcement were studied by FEA. The results showed that the maximum settlement of piles occurred at the end of tunnelling the upper soil strata of the station. After grouted reinforcement, the loose range and plastic range around the tunnelled surface were reduced. The settlement of piles was reduced by 28. 7% compared with that of the unreinforced state. The calculation results showed that the bridge structure could meet the specification requirements in the ultimate bearing capacity and normal service state considering displacement of bearings.
