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2024 Vol. 54, No. 8
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2024, 54(8): 1-8.
doi: 10.3724/j.gyjzG23051901
Abstract:
In order to put forward a performance evaluation method for existing prestressed concrete members considering the distribution of effective prestress, reveal the mapping relationship between the sampling test values of effective prestress and the characteristic parameters of the performance analysis of prestressed concrete structures, and verify the overall distribution law of effective prestress of prestressed concrete structures based on Gaussian mixture unified probability model, based on the sample data of the measured effective prestress values, the typical characteristics of the effective prestress distribution are extracted by the probabilistic and statistical methods such as feature weighting method and maximum expectation algorithm (EM) based on the unified probability model, and the characteristic value of the bearing capacity under the condition of 95% guarantee rate was introduced for quantitative calculation of the service performance of the structure. A method for predicting the performance of existing prestressed concrete members based on measured sample data was proposed. Taking an unbonded prestressed concrete structure as an engineering example, design review method and eigenvalue method were used to evaluate the service performance of the structure respectively. The results showed that compared with the existing evaluation methods, the eigenvalue method could better fit the actual situation and effectively ensure the safety and reliability of the structure, so as to provide a reference for the performance evaluation and reinforcement design of the existing prestressed concrete structures.
In order to put forward a performance evaluation method for existing prestressed concrete members considering the distribution of effective prestress, reveal the mapping relationship between the sampling test values of effective prestress and the characteristic parameters of the performance analysis of prestressed concrete structures, and verify the overall distribution law of effective prestress of prestressed concrete structures based on Gaussian mixture unified probability model, based on the sample data of the measured effective prestress values, the typical characteristics of the effective prestress distribution are extracted by the probabilistic and statistical methods such as feature weighting method and maximum expectation algorithm (EM) based on the unified probability model, and the characteristic value of the bearing capacity under the condition of 95% guarantee rate was introduced for quantitative calculation of the service performance of the structure. A method for predicting the performance of existing prestressed concrete members based on measured sample data was proposed. Taking an unbonded prestressed concrete structure as an engineering example, design review method and eigenvalue method were used to evaluate the service performance of the structure respectively. The results showed that compared with the existing evaluation methods, the eigenvalue method could better fit the actual situation and effectively ensure the safety and reliability of the structure, so as to provide a reference for the performance evaluation and reinforcement design of the existing prestressed concrete structures.
2024, 54(8): 9-18.
doi: 10.3724/j.gyjzG23082902
Abstract:
In order to solve the thorny problems of traditional exterior wall insulation, such as flammability and easy detachment, a type of joints for L-shaped ceramic concrete composite shear walls has been proposed, which can meet the requirement of integrated wall insulation and load-bearing. The hysteresis and skeleton curves, bearing capacity, ductility, energy dissipation and residual displacement were analyzed emphatically through the experiment and finite element study of three specimens. The results showed that the wall joints belonged to the category of bending shear failure. The damage of the web foot was serious and the damage of the core area was light, which met the design requirement of "strong joint and weak member". The ductility coefficient was 1.66 times of that of ordinary concrete composite shear wall, and the deformation capacity was good. The viscous damping coefficient and work ratio coefficient were 4.53 times and 1.87 times higher than those of similar wall panels, respectively, which had significant energy consumption advantages and were beneficial for the overall seismic resistance of the specimens. The comparative analysis between the calculation and experimental results showed a good agreement. Through simulation and expansion analysis, the influence of axial compression ratio and insulation board thickness on the working performance of shear wall joints was found. It was suggested that further research should appropriately improve the material strength, reinforcement, and structural form of the edges and foots of the shear wall joint’s web plate, so as to enhance or improve its working performance.
In order to solve the thorny problems of traditional exterior wall insulation, such as flammability and easy detachment, a type of joints for L-shaped ceramic concrete composite shear walls has been proposed, which can meet the requirement of integrated wall insulation and load-bearing. The hysteresis and skeleton curves, bearing capacity, ductility, energy dissipation and residual displacement were analyzed emphatically through the experiment and finite element study of three specimens. The results showed that the wall joints belonged to the category of bending shear failure. The damage of the web foot was serious and the damage of the core area was light, which met the design requirement of "strong joint and weak member". The ductility coefficient was 1.66 times of that of ordinary concrete composite shear wall, and the deformation capacity was good. The viscous damping coefficient and work ratio coefficient were 4.53 times and 1.87 times higher than those of similar wall panels, respectively, which had significant energy consumption advantages and were beneficial for the overall seismic resistance of the specimens. The comparative analysis between the calculation and experimental results showed a good agreement. Through simulation and expansion analysis, the influence of axial compression ratio and insulation board thickness on the working performance of shear wall joints was found. It was suggested that further research should appropriately improve the material strength, reinforcement, and structural form of the edges and foots of the shear wall joint’s web plate, so as to enhance or improve its working performance.
2024, 54(8): 19-27.
doi: 10.3724/j.gyjzG23110116
Abstract:
Half steel plate concrete composite (HSC) structures are a kind of structural form developed on the basis of steel structures and concrete structures. Compared with ordinary reinforced concrete structures, they have the characteristics of high bearing capacity, good tightness, good impact and explosion resistance, with great application prospects in the fields of nuclear power plant containment shells and roof panels. However, at present, the connection type of tie bars has not been clear, and the impact resistance of different types of tie bars have not been studied. In order to investigate the influence of different structural forms on the failure mechanism and impact resistance of tie bars in actual engineering, the HSC target panels with a scale ratio of 1∶20 and 1∶10 were designed respectively, with three types of tie bar connections. Dynamic impact tests were carried out, and the force mechanism as well as failure modes of different tie bar connections were revealed under dynamic impact load. The results showed that the failure modes of HSC target plates under local impact were mainly bulging and penetrative. The local failure phenomenon was more obvious with the increase of kinetic energy of projectile body. The main factor affecting the failure mode was the plate thickness, followed by the impact velocity. The application of end anchor structure is more beneficial to control the deformation in the impact area and the dynamic response peak near the impact area.
Half steel plate concrete composite (HSC) structures are a kind of structural form developed on the basis of steel structures and concrete structures. Compared with ordinary reinforced concrete structures, they have the characteristics of high bearing capacity, good tightness, good impact and explosion resistance, with great application prospects in the fields of nuclear power plant containment shells and roof panels. However, at present, the connection type of tie bars has not been clear, and the impact resistance of different types of tie bars have not been studied. In order to investigate the influence of different structural forms on the failure mechanism and impact resistance of tie bars in actual engineering, the HSC target panels with a scale ratio of 1∶20 and 1∶10 were designed respectively, with three types of tie bar connections. Dynamic impact tests were carried out, and the force mechanism as well as failure modes of different tie bar connections were revealed under dynamic impact load. The results showed that the failure modes of HSC target plates under local impact were mainly bulging and penetrative. The local failure phenomenon was more obvious with the increase of kinetic energy of projectile body. The main factor affecting the failure mode was the plate thickness, followed by the impact velocity. The application of end anchor structure is more beneficial to control the deformation in the impact area and the dynamic response peak near the impact area.
2024, 54(8): 28-43.
doi: 10.3724/j.gyjzG24032714
Abstract:
Through LS-DYNA finite element simulation software, the shock wave propagation law and structural damage of the blast-resistant chamber subjected to the explosions exceeding 100 kg TNT equivalent were studied. The air pressure distribution and peak overpressure variation across horizontal and vertical sections were analyzed, the propagation law of shock wave was discussed, and the influence of different parameters on the failure mode of blast-resistant chamber was studied. Three damage indexes based on the bearing angle were proposed: λ (the ratio of the upward bending chord length to the top cover length), η (the ratio of the spalling area of the wall panel to the surface area), μ (the ratio of the bending radius of the top cover to the half span) to evaluate the damage degree. The results showed that the peak overpressure near the rear wall area was significantly higher than that of the explosion venting surface. Increasing the thickness of wallboard and concrete strength could change the failure mode from shear failure to flexural failure, while variations in reinforcement ratio and steel yield strength had minimal impact on the failure mode but enhance shear and flexural capacity. Design recommendations include a minimum wall thickness of 300 mm, concrete strength ranging from C30 to C40, and steel yield strength between 235 MPa and 400 MPa. Based on the damage results, the location of the test stand within the chamber should meet the structural requirement of being positioned between the venting surface and the mid-plane of the chamber.
Through LS-DYNA finite element simulation software, the shock wave propagation law and structural damage of the blast-resistant chamber subjected to the explosions exceeding 100 kg TNT equivalent were studied. The air pressure distribution and peak overpressure variation across horizontal and vertical sections were analyzed, the propagation law of shock wave was discussed, and the influence of different parameters on the failure mode of blast-resistant chamber was studied. Three damage indexes based on the bearing angle were proposed: λ (the ratio of the upward bending chord length to the top cover length), η (the ratio of the spalling area of the wall panel to the surface area), μ (the ratio of the bending radius of the top cover to the half span) to evaluate the damage degree. The results showed that the peak overpressure near the rear wall area was significantly higher than that of the explosion venting surface. Increasing the thickness of wallboard and concrete strength could change the failure mode from shear failure to flexural failure, while variations in reinforcement ratio and steel yield strength had minimal impact on the failure mode but enhance shear and flexural capacity. Design recommendations include a minimum wall thickness of 300 mm, concrete strength ranging from C30 to C40, and steel yield strength between 235 MPa and 400 MPa. Based on the damage results, the location of the test stand within the chamber should meet the structural requirement of being positioned between the venting surface and the mid-plane of the chamber.
2024, 54(8): 44-53.
doi: 10.3724/j.gyjzG24022208
Abstract:
In order to promote the innovation and intelligent construction of fully-prefabricated long-span prestressed steel structures, a novel joint which named prestressed high-strength bolted (PHSB) joint was constructed. The influence of key parameters on the performance of PHSB joints was studied. The finite element (FE) model of PHSB joints was established by using ABAQUS FE software, and the accuracy and reliability of the joint model were verified by comparing the experimental results with the numerical simulation results. In the parametric, 54 FE models were established to study the effects of different parameters on tensile/compressive properties of PHSB joints. After that, the tension/compression design method of the joints was proposed. The results indicated that the tensile/compressive properties of the joints could significantly improve with the disc thickness increased; reducing the thickness of the perforated angle steel could appropriately increased the tensile yield load, but reduce its ultimate compressive load; the ultimate tensile/compressive load increased with the increase of perforated cross plate thickness; the change of the sleeve height had little effect on the tensile/compressive properties; moreover, increasing the initial prestress could increase the initial tensile stiffness, but reduce its initial compressive stiffness.
In order to promote the innovation and intelligent construction of fully-prefabricated long-span prestressed steel structures, a novel joint which named prestressed high-strength bolted (PHSB) joint was constructed. The influence of key parameters on the performance of PHSB joints was studied. The finite element (FE) model of PHSB joints was established by using ABAQUS FE software, and the accuracy and reliability of the joint model were verified by comparing the experimental results with the numerical simulation results. In the parametric, 54 FE models were established to study the effects of different parameters on tensile/compressive properties of PHSB joints. After that, the tension/compression design method of the joints was proposed. The results indicated that the tensile/compressive properties of the joints could significantly improve with the disc thickness increased; reducing the thickness of the perforated angle steel could appropriately increased the tensile yield load, but reduce its ultimate compressive load; the ultimate tensile/compressive load increased with the increase of perforated cross plate thickness; the change of the sleeve height had little effect on the tensile/compressive properties; moreover, increasing the initial prestress could increase the initial tensile stiffness, but reduce its initial compressive stiffness.
2024, 54(8): 54-61.
doi: 10.3724/j.gyjzG24031604
Abstract:
Modular assembled reticulated shell structures have the advantages of high construction efficiency and good join quality, and have a wide application prospect. Based on machine learning method, an intelligent prediction model for the bearing capacity of modular prefabricated reticulated shell structures was established. Firstly, 864 finite element models of modular assembled reticulated shells were analyzed for a series of parameters that affect the stable ultimate bearing capacity, thus generating the database required for the machine learning algorithm. Secondly, six machine learning algorithm models were established based on the open source platform Scikit-learn, and all algorithm models were trained and tested by using the generated database. In addition, the artificial neural network model (ANN), XGBoost and gradient enhancement algorithm models were overfitted, and the reliability of ANN model was tested. The results showed that the determination coefficients (R2) of ANN, XGBoost and gradient enhancement algorithm models in the test set were all greater than 0.95, and the prediction accuracy of bearing capacity was very high. The ANN model had the best robustness and accuracy in predicting the stable ultimate bearing capacity, with an average absolute percentage error (MAPE) of 7.1% and an R2 of 0.982. It showed high prediction accuracy and generalization capacity, and could well capture the complex mapping relations between the ultimate bearing capacity and input parameters.
Modular assembled reticulated shell structures have the advantages of high construction efficiency and good join quality, and have a wide application prospect. Based on machine learning method, an intelligent prediction model for the bearing capacity of modular prefabricated reticulated shell structures was established. Firstly, 864 finite element models of modular assembled reticulated shells were analyzed for a series of parameters that affect the stable ultimate bearing capacity, thus generating the database required for the machine learning algorithm. Secondly, six machine learning algorithm models were established based on the open source platform Scikit-learn, and all algorithm models were trained and tested by using the generated database. In addition, the artificial neural network model (ANN), XGBoost and gradient enhancement algorithm models were overfitted, and the reliability of ANN model was tested. The results showed that the determination coefficients (R2) of ANN, XGBoost and gradient enhancement algorithm models in the test set were all greater than 0.95, and the prediction accuracy of bearing capacity was very high. The ANN model had the best robustness and accuracy in predicting the stable ultimate bearing capacity, with an average absolute percentage error (MAPE) of 7.1% and an R2 of 0.982. It showed high prediction accuracy and generalization capacity, and could well capture the complex mapping relations between the ultimate bearing capacity and input parameters.
2024, 54(8): 62-69.
doi: 10.3724/j.gyjzG24022007
Abstract:
The experiments under monotonic and cyclic loading conditions and simulation were conducted to investigate the mechanical properties of prefabricated Z-shaped steel beam-to-column connections. The rotational stiffness, failure mode, bearing capacity, hysteretic performance, energy dissipation, and stiffness degradation of Z-shaped connections with different designed strengths were studied respectively. The results showed that the prefabricated Z-shaped steel beam-to-column connections showed good ductility and could achieve plastic hinge movement outside the panel zone. The designed strength showed a significant effect on the hysteretic performance and plastic bending resistance of Z-shaped connections. The small value of designed strength parameter (0.2-0.9) made that the failure mode of Z-shaped connections was premature damage of bolts. The anti-slip and ultimate bearing capacity of Z-shaped connections increased linearly with the increase of designed strength, and the rotational performance of Z-shaped connections was semi-rigid. In case of the large value of designed strength parameter (0.9-1.3), anti-slip and ultimate bearing capacity of Z-shaped connections were almost unchanged. The failure mode was changed to premature damage of connected members, and the rotational performance of Z-shaped connections was rigid. In addition, the number of bolts required by the proposed Z-shaped connections was relatively small, and the installation was efficient and economical, which could contribute to engineering application.
The experiments under monotonic and cyclic loading conditions and simulation were conducted to investigate the mechanical properties of prefabricated Z-shaped steel beam-to-column connections. The rotational stiffness, failure mode, bearing capacity, hysteretic performance, energy dissipation, and stiffness degradation of Z-shaped connections with different designed strengths were studied respectively. The results showed that the prefabricated Z-shaped steel beam-to-column connections showed good ductility and could achieve plastic hinge movement outside the panel zone. The designed strength showed a significant effect on the hysteretic performance and plastic bending resistance of Z-shaped connections. The small value of designed strength parameter (0.2-0.9) made that the failure mode of Z-shaped connections was premature damage of bolts. The anti-slip and ultimate bearing capacity of Z-shaped connections increased linearly with the increase of designed strength, and the rotational performance of Z-shaped connections was semi-rigid. In case of the large value of designed strength parameter (0.9-1.3), anti-slip and ultimate bearing capacity of Z-shaped connections were almost unchanged. The failure mode was changed to premature damage of connected members, and the rotational performance of Z-shaped connections was rigid. In addition, the number of bolts required by the proposed Z-shaped connections was relatively small, and the installation was efficient and economical, which could contribute to engineering application.
2024, 54(8): 70-77.
doi: 10.3724/j.gyjzG24050701
Abstract:
In order to solve the problem that traditional prefabricated steel frame structures have large residual deformation and cannot be effectively self-centering, a new steel frame structure with self-centering column base joints was proposed. The static analysis of 8 frame models was carried out by the finite element software ABAQUS. The influence of the thickness of the cover plate weakened by dog bone, the initial cable force and the axial compression ratio on the bearing performance of the new frame were systematically studied. The results showed that the bearing capacity of the new self-centering frame was less than 5% and the residual deformation was reduced by more than 50% compared with the traditional steel frame with rigid column base joints. The bearing capacity of the new steel frame was mainly affected by the thickness of the cover plate weakened by dog bone, the initial cable force, and the axial force at the top of the column. The frame could achieve the same bearing capacity and self-centering effect under different parameter combinations.
In order to solve the problem that traditional prefabricated steel frame structures have large residual deformation and cannot be effectively self-centering, a new steel frame structure with self-centering column base joints was proposed. The static analysis of 8 frame models was carried out by the finite element software ABAQUS. The influence of the thickness of the cover plate weakened by dog bone, the initial cable force and the axial compression ratio on the bearing performance of the new frame were systematically studied. The results showed that the bearing capacity of the new self-centering frame was less than 5% and the residual deformation was reduced by more than 50% compared with the traditional steel frame with rigid column base joints. The bearing capacity of the new steel frame was mainly affected by the thickness of the cover plate weakened by dog bone, the initial cable force, and the axial force at the top of the column. The frame could achieve the same bearing capacity and self-centering effect under different parameter combinations.
2024, 54(8): 78-86.
doi: 10.3724/j.gyjzG24033103
Abstract:
To investigate the mechanical properties of the circular main pipe intersecting with the inverted trapezoidal branch pipe at the station building of Shenzhen Universiade Comprehensive Transportation Hub, full-scale joint specimens were subjected to loading tests, and numerical simulations were conducted by using the ABAQUS finite element software. The experimental results agreed well with the numerical simulations, demonstrating elastic behavior under design loads but failure occurred at 2.3 times the design load. Utilizing validated finite element models, the study examined the influence of various parameters on the bearing capacity of joints. Increasing the ratio of the flange width of the branch pipe to the outer diameter of the main pipe, as well as the angle between the axes of the branch pipe and the main pipe, could enhance the bearing capacity of the joint. Furthermore, a formula for calculating the bearing capacity correction factor of inverted trapezoidal section intersecting joints was proposed, offering a foundation for engineering design considerations.
To investigate the mechanical properties of the circular main pipe intersecting with the inverted trapezoidal branch pipe at the station building of Shenzhen Universiade Comprehensive Transportation Hub, full-scale joint specimens were subjected to loading tests, and numerical simulations were conducted by using the ABAQUS finite element software. The experimental results agreed well with the numerical simulations, demonstrating elastic behavior under design loads but failure occurred at 2.3 times the design load. Utilizing validated finite element models, the study examined the influence of various parameters on the bearing capacity of joints. Increasing the ratio of the flange width of the branch pipe to the outer diameter of the main pipe, as well as the angle between the axes of the branch pipe and the main pipe, could enhance the bearing capacity of the joint. Furthermore, a formula for calculating the bearing capacity correction factor of inverted trapezoidal section intersecting joints was proposed, offering a foundation for engineering design considerations.
2024, 54(8): 87-95.
doi: 10.3724/j.gyjzG23110607
Abstract:
The mechanical properties of short composite columns composed of rolled-steel special-shaped profiles under various structural forms and subject to axial compression were investigated. Numerical simulations were conducted by using the ABAQUS finite element software, focusing on rolled-steel special-shaped short composite columns with and without concrete. The accuracy of the modeling approach was corroborated by comparing with existing experimental results, thus establishing the finite element models of the short composite columns. The analysis uncovered the load-bearing performance, failure mode, and force mechanism of the composite columns under axial compression. Furthermore, it explored the effects of different structural forms and the presence or absence of concrete on the axial compressive properties. Findings indicated that all composite columns underwent a complete compression failure, which was accompanied by local buckling failure of steel tubes. The inclusion of concrete clearly ameliorated the failure mode of composite columns and enhanced the bearing capacity. However, the bearing capacity of pure H-steel composite columns improved significantly upon the formation of a closed section by sealing plates. Existing standards and codes were employed to compute the bearing capacity of the short composite columns. The relative difference between the calculated and simulated values was less than 11%, indicating a good agreement. Therefore, these calculated methods can be reliably used to predict the bearing capacity of rolled-steel special-shaped short composite columns under axial compression.
The mechanical properties of short composite columns composed of rolled-steel special-shaped profiles under various structural forms and subject to axial compression were investigated. Numerical simulations were conducted by using the ABAQUS finite element software, focusing on rolled-steel special-shaped short composite columns with and without concrete. The accuracy of the modeling approach was corroborated by comparing with existing experimental results, thus establishing the finite element models of the short composite columns. The analysis uncovered the load-bearing performance, failure mode, and force mechanism of the composite columns under axial compression. Furthermore, it explored the effects of different structural forms and the presence or absence of concrete on the axial compressive properties. Findings indicated that all composite columns underwent a complete compression failure, which was accompanied by local buckling failure of steel tubes. The inclusion of concrete clearly ameliorated the failure mode of composite columns and enhanced the bearing capacity. However, the bearing capacity of pure H-steel composite columns improved significantly upon the formation of a closed section by sealing plates. Existing standards and codes were employed to compute the bearing capacity of the short composite columns. The relative difference between the calculated and simulated values was less than 11%, indicating a good agreement. Therefore, these calculated methods can be reliably used to predict the bearing capacity of rolled-steel special-shaped short composite columns under axial compression.
2024, 54(8): 96-103.
doi: 10.3724/j.gyjzG24021904
Abstract:
To investigate the stress-strain characteristics of concrete under industrial SO2 corrosion, and evaluate the mechanical characteristics of concrete, the concrete corrosion tests in industrial SO2 environment were conducted to analyze the effects of water-to-cement ratio (0.37, 0.47 and 0.57), fly ash content (0%, 10% and 20%), and SO2 cycling times on the danage thickness of damage layers, stress-strain curves, peak stress, peak strain, and elastic modulus. A constitutive model was formulated by using the principles of damage mechanics theory. The results indicated that the thickness of the damage layer rose as the quantity of SO2 cycles increased, with the change adhering to an exponential function correlation. The specimens experienced a decrease in peak stress, an increase in peak strain, and a decrease in elastic modulus after being corroded by SO2. The downward slope of the curve became steeper, significantly reducing the deformation capacity and ultimately exhibiting characteristics of a brittle failure. Adding fly ash could mitigate the corrosion rate of SO2 and enhance the concrete resistance against SO2 corrosion.
To investigate the stress-strain characteristics of concrete under industrial SO2 corrosion, and evaluate the mechanical characteristics of concrete, the concrete corrosion tests in industrial SO2 environment were conducted to analyze the effects of water-to-cement ratio (0.37, 0.47 and 0.57), fly ash content (0%, 10% and 20%), and SO2 cycling times on the danage thickness of damage layers, stress-strain curves, peak stress, peak strain, and elastic modulus. A constitutive model was formulated by using the principles of damage mechanics theory. The results indicated that the thickness of the damage layer rose as the quantity of SO2 cycles increased, with the change adhering to an exponential function correlation. The specimens experienced a decrease in peak stress, an increase in peak strain, and a decrease in elastic modulus after being corroded by SO2. The downward slope of the curve became steeper, significantly reducing the deformation capacity and ultimately exhibiting characteristics of a brittle failure. Adding fly ash could mitigate the corrosion rate of SO2 and enhance the concrete resistance against SO2 corrosion.
2024, 54(8): 104-113.
doi: 10.3724/j.gyjzG24042605
Abstract:
The application of recycled aggregate concrete (RAC) structures holds pivotal practical value in driving the green and high-quality development of the construction industry, attracting widespread attention from academic and engineering communities over the past few decades. This paper systematically reviewed the research progress in the fields of steel bar-RAC bond strength, flexural and shear performance of RAC beam components, and compressive and seismic performance of RAC column components. It also summarized the shortcomings in current scientific research and standard-setting processes. The analysis results revealed that, despite the slightly weaker short-term mechanical performance of RAC structural components compared to natural aggregate concrete (NAC) structural components, their performance could be optimized through measures such as mix proportion design and construction methods, approaching or even exceeding the performance of NAC structural components and basically meeting the requirements of design standards for concrete structures. However, current research on RAC structural components mainly focuses on recycled concrete aggregates made from pure waste concrete, with a slight lack of attention on the structural utilization of solid waste from demolished brick-concrete structures. In addition to short-term mechanical performance, the stability and reliability of the long-term service performance of RAC structural components cannot be overlooked and urgently demand in-depth investigation. Furthermore, the composite cementitious material (CCM) system has the potential to further improve the material performance, economy, and sustainability of RAC. However, most existing research is limited to the material level of CCMs-RAC, lacking systematic studies on the short-term mechanical performance and long-term service performance of CCMs-RAC structures. Therefore, future research should further expand the scope, and deepen the comprehensive performance assessment of RAC structures to promote their widespread applications in the construction industry.
The application of recycled aggregate concrete (RAC) structures holds pivotal practical value in driving the green and high-quality development of the construction industry, attracting widespread attention from academic and engineering communities over the past few decades. This paper systematically reviewed the research progress in the fields of steel bar-RAC bond strength, flexural and shear performance of RAC beam components, and compressive and seismic performance of RAC column components. It also summarized the shortcomings in current scientific research and standard-setting processes. The analysis results revealed that, despite the slightly weaker short-term mechanical performance of RAC structural components compared to natural aggregate concrete (NAC) structural components, their performance could be optimized through measures such as mix proportion design and construction methods, approaching or even exceeding the performance of NAC structural components and basically meeting the requirements of design standards for concrete structures. However, current research on RAC structural components mainly focuses on recycled concrete aggregates made from pure waste concrete, with a slight lack of attention on the structural utilization of solid waste from demolished brick-concrete structures. In addition to short-term mechanical performance, the stability and reliability of the long-term service performance of RAC structural components cannot be overlooked and urgently demand in-depth investigation. Furthermore, the composite cementitious material (CCM) system has the potential to further improve the material performance, economy, and sustainability of RAC. However, most existing research is limited to the material level of CCMs-RAC, lacking systematic studies on the short-term mechanical performance and long-term service performance of CCMs-RAC structures. Therefore, future research should further expand the scope, and deepen the comprehensive performance assessment of RAC structures to promote their widespread applications in the construction industry.
2024, 54(8): 114-125.
doi: 10.3724/j.gyjzG24042606
Abstract:
In addition to the short-term mechanical performance of recycled aggregate concrete (RAC) structures, the stability and reliability of long-term service performance are also worthy of special attention, which is directly associated with the long-term safety and stability of such structures. This paper systematically reviewed the research progress in the steel corrosion within RAC, corrosion-induced cracking of RAC, the bonding strength between corroded steel bars and RAC, as well as the long-term service performance of RAC beam and column components. It also pointed out the shortcomings in current scientific research and standard-setting processes. The analysis results indicated that although the short-term mechanical performance of RAC structural components were comparable to those of natural aggregate concrete (NAC) structural components through optimized mix proportion design and construction methods, the long-term service performance of the former was significantly weakened, especially under service conditions of combined chloride attack and loading damage. Furthermore, the influence of recycled aggregate (RA) replacement ratio on the long-term service performance of RAC structural components cannot be ignored, and special considerations are needed in the durability design of such structures. Therefore, it is necessary to carry out follow-up research on the long-term service performance of RAC structural components. Through delving into the deterioration mechanisms underlying their long-term service performance, more abundant data support and theoretical references are provided for the standard revision and application promotion of RAC structures to achieve low-carbon and sustainable development in the construction industry.
In addition to the short-term mechanical performance of recycled aggregate concrete (RAC) structures, the stability and reliability of long-term service performance are also worthy of special attention, which is directly associated with the long-term safety and stability of such structures. This paper systematically reviewed the research progress in the steel corrosion within RAC, corrosion-induced cracking of RAC, the bonding strength between corroded steel bars and RAC, as well as the long-term service performance of RAC beam and column components. It also pointed out the shortcomings in current scientific research and standard-setting processes. The analysis results indicated that although the short-term mechanical performance of RAC structural components were comparable to those of natural aggregate concrete (NAC) structural components through optimized mix proportion design and construction methods, the long-term service performance of the former was significantly weakened, especially under service conditions of combined chloride attack and loading damage. Furthermore, the influence of recycled aggregate (RA) replacement ratio on the long-term service performance of RAC structural components cannot be ignored, and special considerations are needed in the durability design of such structures. Therefore, it is necessary to carry out follow-up research on the long-term service performance of RAC structural components. Through delving into the deterioration mechanisms underlying their long-term service performance, more abundant data support and theoretical references are provided for the standard revision and application promotion of RAC structures to achieve low-carbon and sustainable development in the construction industry.
2024, 54(8): 126-132.
doi: 10.3724/j.gyjzG24061802
Abstract:
Cracks are a common form of surface damage in concrete structures and have significant implications for assessing structural performance. The use of computer vision techniques for crack recognition and quantification on the surface of concrete structures has been widely studied. However, deep learning-based crack recognition techniques rely on large-scale crack datasets for training. To address this issue, the paper proposed a data augmentation method based on style transfer networks. A large-scale, complex-background crack dataset was constructed by using a small amount of crack data and various background image data. The YoloV8 network model was trained to achieve crack recognition and segmentation. Based on the crack characteristics, isolated and tiny areas in the recognition results were filtered. Based on this, crack width quantification analysis was performed based on known reference markers, and the experimental results showed that the calculation error of crack widths was basically controlled within 20%.
Cracks are a common form of surface damage in concrete structures and have significant implications for assessing structural performance. The use of computer vision techniques for crack recognition and quantification on the surface of concrete structures has been widely studied. However, deep learning-based crack recognition techniques rely on large-scale crack datasets for training. To address this issue, the paper proposed a data augmentation method based on style transfer networks. A large-scale, complex-background crack dataset was constructed by using a small amount of crack data and various background image data. The YoloV8 network model was trained to achieve crack recognition and segmentation. Based on the crack characteristics, isolated and tiny areas in the recognition results were filtered. Based on this, crack width quantification analysis was performed based on known reference markers, and the experimental results showed that the calculation error of crack widths was basically controlled within 20%.
2024, 54(8): 133-139.
doi: 10.3724/j.gyjzG23062009
Abstract:
Traditional manual inspection methods for surface corrosion damage in steel structures are time-consuming, labor-intensive, and limited by the technical expertise of the inspection personnel. Computer vision technology provides a fast and accurate alternative method for detecting and classifying the surface corrosion on steel structures. Currently, commonly used methods for corrosion degree detection are based on convolutional neural network (CNN) structures. However, due to inherent flaws in the network structure, there is a problem of neglecting certain rust features in the image during corrosion degree classification, leading to incorrect detection results. A steel structure surface corrosion degree recognition method based on the Vision Transformer network structure was proposed. By introducing self-attention mechanisms (SA) during the feature extraction process, data integrity could be ensured. The proposed method was validated on a self-built dataset of rust severity images, achieving an accuracy ratio of 90% in corrosion degree classification. Furthermore, a steel structure surface corrosion degree detection method based on the sliding-window method was also proposed. This method involves segmenting the steel structure images to be inspected, utilizing a trained network structure for corrosion degree detection, and reassembling the detected images to achieve intelligent detection of corrosion degree on the surface of steel structures.
Traditional manual inspection methods for surface corrosion damage in steel structures are time-consuming, labor-intensive, and limited by the technical expertise of the inspection personnel. Computer vision technology provides a fast and accurate alternative method for detecting and classifying the surface corrosion on steel structures. Currently, commonly used methods for corrosion degree detection are based on convolutional neural network (CNN) structures. However, due to inherent flaws in the network structure, there is a problem of neglecting certain rust features in the image during corrosion degree classification, leading to incorrect detection results. A steel structure surface corrosion degree recognition method based on the Vision Transformer network structure was proposed. By introducing self-attention mechanisms (SA) during the feature extraction process, data integrity could be ensured. The proposed method was validated on a self-built dataset of rust severity images, achieving an accuracy ratio of 90% in corrosion degree classification. Furthermore, a steel structure surface corrosion degree detection method based on the sliding-window method was also proposed. This method involves segmenting the steel structure images to be inspected, utilizing a trained network structure for corrosion degree detection, and reassembling the detected images to achieve intelligent detection of corrosion degree on the surface of steel structures.
2024, 54(8): 140-148.
doi: 10.3724/j.gyjzG24042902
Abstract:
The building components of steel structures are prefabricated in factories. This stage is between the upstream crude steel production and downstream building on-site construction, and it lacks basic research on carbon emissions. Existing studies are mostly based on the input-output method to derive an average carbon emission factor for per ton of steel, which ignores the differences between different steel products and cannot reveal the sources of carbon emissions. This study was carried out at a steel fabrication plant in Tianjin with an annual capacity of 160 000 tons. Representative machines were selected for the main processes of steel components fabrication to test the amount of carbon emissions generated by each process. A linear function was used to fit the relation between the functional unit (FU) processing work and the corresponding carbon emissions. It showed that for the cutting, pre-assembly, assembly, and straightening processes, the coefficients of determination (R2) of the obtained fitting functions were all greater than 0.9 when the area of cut surface, length of component, quality of weld seam, and length of component were used as FU, respectively.
The building components of steel structures are prefabricated in factories. This stage is between the upstream crude steel production and downstream building on-site construction, and it lacks basic research on carbon emissions. Existing studies are mostly based on the input-output method to derive an average carbon emission factor for per ton of steel, which ignores the differences between different steel products and cannot reveal the sources of carbon emissions. This study was carried out at a steel fabrication plant in Tianjin with an annual capacity of 160 000 tons. Representative machines were selected for the main processes of steel components fabrication to test the amount of carbon emissions generated by each process. A linear function was used to fit the relation between the functional unit (FU) processing work and the corresponding carbon emissions. It showed that for the cutting, pre-assembly, assembly, and straightening processes, the coefficients of determination (R2) of the obtained fitting functions were all greater than 0.9 when the area of cut surface, length of component, quality of weld seam, and length of component were used as FU, respectively.
2024, 54(8): 149-156.
doi: 10.3724/j.gyjzG23051713
Abstract:
Taking the arch and corridor project of Xiangyu tourist and sightseeing place in Linyi, Shandong province as the background, the composite structure system of large rise-span ratio cross steel arch and hectometre corridor was analyzed and designed. The overview of the project was introduced, and the structural design features of the system were discussed. The core content of the design of corridor, arch and pedestrian bridge in the structural system was expounded. The structural form of cross steel arch support with large rise-span ratio was presented. The design characteristics of the corridor with weak connections was pointed out. It was defined that TMD device was used to control the vibration of the corridor and pedestrian bridge under the excitation of walking load. The ANSYS finite element software was used to analyze the mechanical characteristics of the composite structure. The results showed that the structural performance was safe and reliable, and the indexes conformed to the design specifications. The key technical issues needing further study were put forward.
Taking the arch and corridor project of Xiangyu tourist and sightseeing place in Linyi, Shandong province as the background, the composite structure system of large rise-span ratio cross steel arch and hectometre corridor was analyzed and designed. The overview of the project was introduced, and the structural design features of the system were discussed. The core content of the design of corridor, arch and pedestrian bridge in the structural system was expounded. The structural form of cross steel arch support with large rise-span ratio was presented. The design characteristics of the corridor with weak connections was pointed out. It was defined that TMD device was used to control the vibration of the corridor and pedestrian bridge under the excitation of walking load. The ANSYS finite element software was used to analyze the mechanical characteristics of the composite structure. The results showed that the structural performance was safe and reliable, and the indexes conformed to the design specifications. The key technical issues needing further study were put forward.
2024, 54(8): 157-162.
doi: 10.3724/j.gyjzG24040913
Abstract:
When a force is applied to a prestressed component, the tension T in the prestressed tendons varies due to their curved arrangement and the friction between them and the corrugated ducts. Additionally, the curvature of the prestressed tendons generates normal force P in the curve's normal direction, which in turn creates friction F. The tension T, normal force P, and friction F all induce internal stress within the concrete. For certain specialized structures, the internal stress is directly linked to the normal force P; thus, accurately calculating the structural stress requires first determining the normal force. Accurate algorithms for the tension T are available. The normal pressure P and friction F can be approximated through differential methods, though they are not feasible for practical engineering applications. To address the need for tension force calculations in prestress design, based on Newton's law of force balance, a rapid and precise method for calculating tension forces has been proposed by using a differential approach and iterative methods. A set of general differential equations for simultaneously calculating the tension force T, friction force F, and normal force P have been derived. The equations enable the computation of forces in various complex prestressed components, offering a robust computational tool for prestressed component design.
When a force is applied to a prestressed component, the tension T in the prestressed tendons varies due to their curved arrangement and the friction between them and the corrugated ducts. Additionally, the curvature of the prestressed tendons generates normal force P in the curve's normal direction, which in turn creates friction F. The tension T, normal force P, and friction F all induce internal stress within the concrete. For certain specialized structures, the internal stress is directly linked to the normal force P; thus, accurately calculating the structural stress requires first determining the normal force. Accurate algorithms for the tension T are available. The normal pressure P and friction F can be approximated through differential methods, though they are not feasible for practical engineering applications. To address the need for tension force calculations in prestress design, based on Newton's law of force balance, a rapid and precise method for calculating tension forces has been proposed by using a differential approach and iterative methods. A set of general differential equations for simultaneously calculating the tension force T, friction force F, and normal force P have been derived. The equations enable the computation of forces in various complex prestressed components, offering a robust computational tool for prestressed component design.
