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2022 Vol. 52, No. 10
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2022, 52(10): 1-8,70.
doi: 10.13204/j.gyjzG22082202
Abstract:
Concrete structures in corrosive environment often suffer from reinforcement corrosion, which leads to durability degradation and shortens the service life of these structures. The safe and durable operation and maintenance of concrete structures are based on durability diagnosis, accurate prediction of the residue life, and scientific evaluation of the service capabilities. On the basis of the performance degradation process during the whole lifetime of the structure, the complexity of the service environment of the structure and the effects of reinforcement corrosion on structure performance were fully considered, and the durability limit states of concrete structures based on reinforcement corrosion were presented. The durability grades of concrete structures were defined according to the probability analysis of the reinforcement corrosion of field structures, and the scientific evaluation of the durability of concrete structures by referring to the reinforcement corrosion process was achieved. The study provides a reference for the durability evaluation of concrete structures with reinforcement corrosion as the main degradation form in normal atmospheric environment and chloride environment, and it is of guiding significance for later operation and maintenance of such structures.
Concrete structures in corrosive environment often suffer from reinforcement corrosion, which leads to durability degradation and shortens the service life of these structures. The safe and durable operation and maintenance of concrete structures are based on durability diagnosis, accurate prediction of the residue life, and scientific evaluation of the service capabilities. On the basis of the performance degradation process during the whole lifetime of the structure, the complexity of the service environment of the structure and the effects of reinforcement corrosion on structure performance were fully considered, and the durability limit states of concrete structures based on reinforcement corrosion were presented. The durability grades of concrete structures were defined according to the probability analysis of the reinforcement corrosion of field structures, and the scientific evaluation of the durability of concrete structures by referring to the reinforcement corrosion process was achieved. The study provides a reference for the durability evaluation of concrete structures with reinforcement corrosion as the main degradation form in normal atmospheric environment and chloride environment, and it is of guiding significance for later operation and maintenance of such structures.
2022, 52(10): 9-15.
doi: 10.13204/j.gyjzG22072513
Abstract:
Although glass curtain walls are widely used in large-scale and high-rise buildings in China, relevant safety issues are becoming increasingly prominent. This paper used the accident cases in recent years to analyze the main safety hazard types and main reasons for the falling of existing glass curtain walls. Then, the paper put forward the challenges faced by the inspection techniques of glass curtain walls and summarized the new techniques and methods in this regard all around the world. The study can provide a reference and suggestions for the development of inspection techniques for existing glass curtain walls.
Although glass curtain walls are widely used in large-scale and high-rise buildings in China, relevant safety issues are becoming increasingly prominent. This paper used the accident cases in recent years to analyze the main safety hazard types and main reasons for the falling of existing glass curtain walls. Then, the paper put forward the challenges faced by the inspection techniques of glass curtain walls and summarized the new techniques and methods in this regard all around the world. The study can provide a reference and suggestions for the development of inspection techniques for existing glass curtain walls.
2022, 52(10): 16-21,15.
doi: 10.13204/j.gyjzG22061712
Abstract:
Durability deterioration of marine structures in nuclear power plants causes the reinforcement corrosion and may lead to concrete cracking, delamination, and spalling, which poses a great threat to the safety and durability of structures. The consideration of anti-corrosion importance and necessity of concrete are seriously inadequate in the design, construction, and operation of existing nuclear power plants. The anti-corrosion countermeasures are not controlled in a sufficiently strict manner, and the durability problem is severe, especially the corrosion durability of chlorides. If reliable monitoring sensors could be embedded or installed in the structure, the structural damage data can be uploaded, analyzed, and processed in real time to achieve early warnings and life prediction, which is of great significance to ensure the normal operation of the aging management and life extension period of the nuclear power plants. This paper summarized the typical durability problems of marine structures in nuclear power plants and the common durability monitoring methods for the most serious chloride corrosion in marine structures for an accurate grasp of the current research status of the durability problems and monitoring of marine structures in nuclear power plants. It may provide some reference for research on durability warning and diagnosis.
Durability deterioration of marine structures in nuclear power plants causes the reinforcement corrosion and may lead to concrete cracking, delamination, and spalling, which poses a great threat to the safety and durability of structures. The consideration of anti-corrosion importance and necessity of concrete are seriously inadequate in the design, construction, and operation of existing nuclear power plants. The anti-corrosion countermeasures are not controlled in a sufficiently strict manner, and the durability problem is severe, especially the corrosion durability of chlorides. If reliable monitoring sensors could be embedded or installed in the structure, the structural damage data can be uploaded, analyzed, and processed in real time to achieve early warnings and life prediction, which is of great significance to ensure the normal operation of the aging management and life extension period of the nuclear power plants. This paper summarized the typical durability problems of marine structures in nuclear power plants and the common durability monitoring methods for the most serious chloride corrosion in marine structures for an accurate grasp of the current research status of the durability problems and monitoring of marine structures in nuclear power plants. It may provide some reference for research on durability warning and diagnosis.
2022, 52(10): 22-27.
doi: 10.13204/j.gyjzG22071401
Abstract:
Steel structures suffer from surface damage all the time due to their material properties and insufficient daily management. With the development of digital information technology, computer vision techniques have become key means in damage identification and health monitoring of steel structures. This paper presented the advances of computer vision techniques in damage and health monitoring of steel structures and discussed the identification techniques for surface corrosion damage, weld joint damage, and bolt connection damage of steel structures and their health monitoring. Moreover, it also predicted the development trends of damage identification and health monitoring techniques based on computer vision for steel structures.
Steel structures suffer from surface damage all the time due to their material properties and insufficient daily management. With the development of digital information technology, computer vision techniques have become key means in damage identification and health monitoring of steel structures. This paper presented the advances of computer vision techniques in damage and health monitoring of steel structures and discussed the identification techniques for surface corrosion damage, weld joint damage, and bolt connection damage of steel structures and their health monitoring. Moreover, it also predicted the development trends of damage identification and health monitoring techniques based on computer vision for steel structures.
2022, 52(10): 28-38,45.
doi: 10.13204/j.gyjzG22041612
Abstract:
Existing codes and standards adopt qualitative and quantitative methods to assess the safety of concrete frame structures, which can hardly judge the relative safety of structures at the same safety level. According to the stress characteristics of concrete frame structures, this paper built a hierarchical safety assessment model, combined the existing codes and standards in structural design, testing, and identification to construct a safety grade evaluation index system for component inspection items, and established comprehensive evaluation matrices for inspection items on the basis of membership function theory. Moreover, it developed a three-level fuzzy comprehensive evaluation method for the safety of concrete frame structures. The engineering cases with the safety of the main design structure rated as A, B, C, and D according to the current identification standards were designed, and the structural safety was evaluated by the proposed method in this paper, the maximum membership degree method, and the weighted rank average method for comparative analysis. The research results show that the structural safety evaluation model based on the analytic hierarchy process (AHP) can reflect the stress characteristics of concrete frame structures. Using the Delphi method to determine the fuzzy sets of the importance of the factors can give full play to the collective wisdom of experts in the evaluation and can better reflect the fairness of empowerment. The fuzzy comprehensive evaluation method based on the AHP model, fuzzy sets of factor importance, and comprehensive evaluation matrices of component inspection items can quantitatively evaluate the safety of concrete frame structures. Moreover, its results can achieve the highest degree of coincidence with the safety grade evaluation results of current specifications, and the average consistency rates of the component layer, sub-unit layer, and appraisal unit layer are 71.9%, 91.7%, and 100%, respectively.
Existing codes and standards adopt qualitative and quantitative methods to assess the safety of concrete frame structures, which can hardly judge the relative safety of structures at the same safety level. According to the stress characteristics of concrete frame structures, this paper built a hierarchical safety assessment model, combined the existing codes and standards in structural design, testing, and identification to construct a safety grade evaluation index system for component inspection items, and established comprehensive evaluation matrices for inspection items on the basis of membership function theory. Moreover, it developed a three-level fuzzy comprehensive evaluation method for the safety of concrete frame structures. The engineering cases with the safety of the main design structure rated as A, B, C, and D according to the current identification standards were designed, and the structural safety was evaluated by the proposed method in this paper, the maximum membership degree method, and the weighted rank average method for comparative analysis. The research results show that the structural safety evaluation model based on the analytic hierarchy process (AHP) can reflect the stress characteristics of concrete frame structures. Using the Delphi method to determine the fuzzy sets of the importance of the factors can give full play to the collective wisdom of experts in the evaluation and can better reflect the fairness of empowerment. The fuzzy comprehensive evaluation method based on the AHP model, fuzzy sets of factor importance, and comprehensive evaluation matrices of component inspection items can quantitatively evaluate the safety of concrete frame structures. Moreover, its results can achieve the highest degree of coincidence with the safety grade evaluation results of current specifications, and the average consistency rates of the component layer, sub-unit layer, and appraisal unit layer are 71.9%, 91.7%, and 100%, respectively.
2022, 52(10): 39-45.
doi: 10.13204/j.gyjzG22060906
Abstract:
Shrinkage and creep of concrete, and relaxation of prestressed tendons will cause loss of prestress, and which then affect long-term performances of prestressed concrete structures. The calculated values of long-term prestress loss obtained according to existing specifications are quite different from actual measured values, therefore, a inversion and prediction method for parameters of long-term prestress loss based on the multi-population genetic algorithm was proposed. The method was used to analyze parameter sensitivity to influence calculation results of long-term prestress loss by methods of specificetions of JTG 3362-2018 and ACI 209-1992. A loss curve in good agreement with measureng values of long-term prestress loss was obtained through inversion analysis for sensitive parameters by the muti-population genetic algorithan, which verified the feasibility and accuracy of the method. Simul taneously, the long-term prestress loss subjected to tensioning for 30 years calculated by the above two specifications was predicted respectiverly, which were 9.5% and 9.2%.
Shrinkage and creep of concrete, and relaxation of prestressed tendons will cause loss of prestress, and which then affect long-term performances of prestressed concrete structures. The calculated values of long-term prestress loss obtained according to existing specifications are quite different from actual measured values, therefore, a inversion and prediction method for parameters of long-term prestress loss based on the multi-population genetic algorithm was proposed. The method was used to analyze parameter sensitivity to influence calculation results of long-term prestress loss by methods of specificetions of JTG 3362-2018 and ACI 209-1992. A loss curve in good agreement with measureng values of long-term prestress loss was obtained through inversion analysis for sensitive parameters by the muti-population genetic algorithan, which verified the feasibility and accuracy of the method. Simul taneously, the long-term prestress loss subjected to tensioning for 30 years calculated by the above two specifications was predicted respectiverly, which were 9.5% and 9.2%.
2022, 52(10): 46-52.
doi: 10.13204/j.gyjzG22012407
Abstract:
For the ultra-long and complex isolation structures, the isolation supports engendered a large lateral displacement phenomenon easily during construction stages. Real-time and accurate deformation monitoring for isolation supports is an effective basis for guiding construction in progress and judging actual stress of structures. The traditional measurement method of contact displacement is restricted by dimensions, accuracy, complicated operation, and installation, etc. The use of the non-contact measurement method based on computer vision can effectively overcome shortcomings of the traditional method. A displacement monitoring system based on computer vision was proposed. Network cameras were used as acquisition devices, and the color matching technique was used to realize displacement measurement of targets. The system was applied in a large terminal building in the west of China, and used for displacement monitoring of isolation supports in the building, and the monitoring data of deformation and temperature of isolation supports were analyzed. The results showed that the monitoring system based on computer vision could accurately measure deformation of isolation supports, and serve as an automatic and economical intelligent system for the structure for a long time. The deformation law changed with temperature for isolation supports of the ultra-long isolation structure was given.
For the ultra-long and complex isolation structures, the isolation supports engendered a large lateral displacement phenomenon easily during construction stages. Real-time and accurate deformation monitoring for isolation supports is an effective basis for guiding construction in progress and judging actual stress of structures. The traditional measurement method of contact displacement is restricted by dimensions, accuracy, complicated operation, and installation, etc. The use of the non-contact measurement method based on computer vision can effectively overcome shortcomings of the traditional method. A displacement monitoring system based on computer vision was proposed. Network cameras were used as acquisition devices, and the color matching technique was used to realize displacement measurement of targets. The system was applied in a large terminal building in the west of China, and used for displacement monitoring of isolation supports in the building, and the monitoring data of deformation and temperature of isolation supports were analyzed. The results showed that the monitoring system based on computer vision could accurately measure deformation of isolation supports, and serve as an automatic and economical intelligent system for the structure for a long time. The deformation law changed with temperature for isolation supports of the ultra-long isolation structure was given.
2022, 52(10): 53-60.
doi: 10.13204/j.gyjzG22070112
Abstract:
Based on computer vision, the procedure of recognizing wide-range cracks on the surface of concrete members was presented by obtaining the wide-range crack images through image stitching, and identifying cracks by the threshold segmentation. Adopting the procedure, crack monitoring was conducted on a reinforced concrete (RC) column under cyclic loading to study crack development on the surface during loading and unloading processes. The results showed that wide-range concrete surfaces with cracks could be photographed in a sub-regional way with consumer-grade mobile phones. By further stitching the photos together, the cracks were finely recognized. The proposed procedure could be well used to recognize wide-range cracks on the surface of RC columns with relatively higher identification accuracy regarding crack width, length and inclined angles. In addition, with the increase of displacement amplifude, the width, length and areas of cracks on the surface of the RC column increased, the inclined angles decreased, and then the damage increased.
Based on computer vision, the procedure of recognizing wide-range cracks on the surface of concrete members was presented by obtaining the wide-range crack images through image stitching, and identifying cracks by the threshold segmentation. Adopting the procedure, crack monitoring was conducted on a reinforced concrete (RC) column under cyclic loading to study crack development on the surface during loading and unloading processes. The results showed that wide-range concrete surfaces with cracks could be photographed in a sub-regional way with consumer-grade mobile phones. By further stitching the photos together, the cracks were finely recognized. The proposed procedure could be well used to recognize wide-range cracks on the surface of RC columns with relatively higher identification accuracy regarding crack width, length and inclined angles. In addition, with the increase of displacement amplifude, the width, length and areas of cracks on the surface of the RC column increased, the inclined angles decreased, and then the damage increased.
2022, 52(10): 61-70.
doi: 10.13204/j.gyjzG22042522
Abstract:
The implicit dynamic analysis by finite-element (FE) software ABAQUS was utilized to conduct numerical simulations on the demolition and collapse process of three common plane truss structures, namely, orthogonal, orthogonal diagonal, and three-dimensional space trusses, and four pyramid space trusses, i.e., one-way folding line, square pyramid, diagonal square pyramid, and triangular pyramid space trusses. The collapse test of the plane truss structure and the actual demolition and collapse situation of the roof space truss of Shenzhen Gymnasium were compared with the numerical simulations, which verified the accuracy of the numerical simulation. The sensitivity analysis of elements was made to calculate the importance factor of elements and determine the important elements in the demolition of different space trusses, and corresponding demolition plans were formulated. The research results show that after the fixed element group at the column ends of space truss structures is demolished, the compressive stress of the residual elements at the column ends is increased, and buckling instability caused by the compressive stress accounts for the large vertical deformation of the space truss. When the space truss falls down below the top of the column, the elements at the column ends are subjected to the tensile stress, and the catenary action in the truss provides an alternate way for the vertical load, which leads to the strength failure, the main reason for the overall collapse of the space truss.
The implicit dynamic analysis by finite-element (FE) software ABAQUS was utilized to conduct numerical simulations on the demolition and collapse process of three common plane truss structures, namely, orthogonal, orthogonal diagonal, and three-dimensional space trusses, and four pyramid space trusses, i.e., one-way folding line, square pyramid, diagonal square pyramid, and triangular pyramid space trusses. The collapse test of the plane truss structure and the actual demolition and collapse situation of the roof space truss of Shenzhen Gymnasium were compared with the numerical simulations, which verified the accuracy of the numerical simulation. The sensitivity analysis of elements was made to calculate the importance factor of elements and determine the important elements in the demolition of different space trusses, and corresponding demolition plans were formulated. The research results show that after the fixed element group at the column ends of space truss structures is demolished, the compressive stress of the residual elements at the column ends is increased, and buckling instability caused by the compressive stress accounts for the large vertical deformation of the space truss. When the space truss falls down below the top of the column, the elements at the column ends are subjected to the tensile stress, and the catenary action in the truss provides an alternate way for the vertical load, which leads to the strength failure, the main reason for the overall collapse of the space truss.
2022, 52(10): 71-77.
doi: 10.13204/j.gyjzG22062310
Abstract:
So far, damage identification of string structures based on dynamic detection can be only qualitatively estimated. Aiming at the subsistent problem, a method which could quantitatively identify curvature model parameters was proposed. The improved absolute difference indexes and variation ratio indexes of curvature modals were used to diagnose structural damage. Structural damage locations and damage degrees were determined by the above damage identification indexes. Taking a stadium with long-span beam-string structure as a research object, the ANSYS finite element model was constructed. In order to verify the availability of damage identification indexes, a variety of damage cases were simulated by reducing elastic moduli of structural elements. The results showed that structural damage locations of the upper chord member could be precisely judged by the improved absolute difference indexes of curvature modals, and structural damage degrees of the upper chord member and the lower chord cable could be accurately identified by the variation ratio indexes of curvature modals through lower-order modal data. The method was simple and low-cost.
So far, damage identification of string structures based on dynamic detection can be only qualitatively estimated. Aiming at the subsistent problem, a method which could quantitatively identify curvature model parameters was proposed. The improved absolute difference indexes and variation ratio indexes of curvature modals were used to diagnose structural damage. Structural damage locations and damage degrees were determined by the above damage identification indexes. Taking a stadium with long-span beam-string structure as a research object, the ANSYS finite element model was constructed. In order to verify the availability of damage identification indexes, a variety of damage cases were simulated by reducing elastic moduli of structural elements. The results showed that structural damage locations of the upper chord member could be precisely judged by the improved absolute difference indexes of curvature modals, and structural damage degrees of the upper chord member and the lower chord cable could be accurately identified by the variation ratio indexes of curvature modals through lower-order modal data. The method was simple and low-cost.
2022, 52(10): 78-83.
doi: 10.13204/j.gyjzG21112501
Abstract:
The effectiveness of the wavelet packet energy curvature difference for damage identification has been verified by numerical simulations, laboratory tests, and engineering projects, but the quantitative analysis of structural damage is lacking. Taking the three-layer space frame structure as the research object, this study used the finite element software Abaqus for numerical simulation and dynamic time history analysis. Moreover, it introduced the virtual impulse response function to investigate the effects of the external structural excitation, damage degree, damage location, and elastic modulus on its recognition effect and study the quantitative estimation of the degree of structural damage by the wavelet packet energy curvature difference. The results indicate that the introduction of the virtual impulse response function does not affect the damage-location recognition effect of the wavelet packet energy curvature difference and can effectively reduce the influence of external excitation. The structural damage degree and damage location, however, have an impact on it, and when the elastic modulus is equal to or greater than 3.0×1010 Pa, it exerts no influence. The numerical fitting formula can effectively identify the degree of structural damage in a quantitative manner.
The effectiveness of the wavelet packet energy curvature difference for damage identification has been verified by numerical simulations, laboratory tests, and engineering projects, but the quantitative analysis of structural damage is lacking. Taking the three-layer space frame structure as the research object, this study used the finite element software Abaqus for numerical simulation and dynamic time history analysis. Moreover, it introduced the virtual impulse response function to investigate the effects of the external structural excitation, damage degree, damage location, and elastic modulus on its recognition effect and study the quantitative estimation of the degree of structural damage by the wavelet packet energy curvature difference. The results indicate that the introduction of the virtual impulse response function does not affect the damage-location recognition effect of the wavelet packet energy curvature difference and can effectively reduce the influence of external excitation. The structural damage degree and damage location, however, have an impact on it, and when the elastic modulus is equal to or greater than 3.0×1010 Pa, it exerts no influence. The numerical fitting formula can effectively identify the degree of structural damage in a quantitative manner.
2022, 52(10): 84-88,77.
doi: 10.13204/j.gyjzG22070417
Abstract:
The nuclear power plant containment is an important physical barrier to ensure the safe operation of nuclear power units. The Containment Tightness Test (CTT) is an important means to verify the strength and tightness of the containment structure. Before the nuclear power plant is built and put into use, the CTT is used to verify whether the construction quality and structural performance of the containment meet the design requirements. Due to the complexity of the prestressed containment structure, it is difficult to accurately calculate and predict the structural response of the containment under the pressure test. Taking a third generation nuclear power plant as the research object, a refined three-dimensional finite element model of the containment was established based on ANSYS. The overall deformation and strain of the structure were continuously monitored during the prestressed tension and CTT of the containment. The initial analysis parameters of the finite element model were modified through the coincidence analysis of the measured and calculated values of concrete strain during batch tensioning of prestressed tendons. Based on the modified finite element model, the structural deformation of the containment under test pressure were calculated and predicted before the CTT. The monitoring measured data during the CTT showed that the structural performance of the containment under test pressure can be accurately calculated and predicted by the above finite element model modification method.
The nuclear power plant containment is an important physical barrier to ensure the safe operation of nuclear power units. The Containment Tightness Test (CTT) is an important means to verify the strength and tightness of the containment structure. Before the nuclear power plant is built and put into use, the CTT is used to verify whether the construction quality and structural performance of the containment meet the design requirements. Due to the complexity of the prestressed containment structure, it is difficult to accurately calculate and predict the structural response of the containment under the pressure test. Taking a third generation nuclear power plant as the research object, a refined three-dimensional finite element model of the containment was established based on ANSYS. The overall deformation and strain of the structure were continuously monitored during the prestressed tension and CTT of the containment. The initial analysis parameters of the finite element model were modified through the coincidence analysis of the measured and calculated values of concrete strain during batch tensioning of prestressed tendons. Based on the modified finite element model, the structural deformation of the containment under test pressure were calculated and predicted before the CTT. The monitoring measured data during the CTT showed that the structural performance of the containment under test pressure can be accurately calculated and predicted by the above finite element model modification method.
2022, 52(10): 89-93,105.
doi: 10.13204/j.gyjzG22072913
Abstract:
The fiber-Bragg-grating (FBG) self-sensing anchor cable was used to carry out an experimental monitoring application in the foundation pit support engineering of a stadium with a "double-row pile + anchor cable" in a muddy geological environment. The monitoring results show that as the FBG self-sensing anchor cable can efficiently monitor the cable force at each moment, it accurately obtains the cable force change during the construction process of prestressed tensioning. In addition, the monitoring range of the self-sensing anchor cable is its full length. Given the cable-force growth curve of each measuring point, the anchoring effect of the corresponding part of the anchor cable and the rock and soil mass can be inferred. The long-term monitoring results indicate that the self-sensing anchor cable synchronously responds to changes in the displacement and deformation of the supporting structure accurately. Therefore, it provides reliable data support for the quality and safety of anchor cable engineering.
The fiber-Bragg-grating (FBG) self-sensing anchor cable was used to carry out an experimental monitoring application in the foundation pit support engineering of a stadium with a "double-row pile + anchor cable" in a muddy geological environment. The monitoring results show that as the FBG self-sensing anchor cable can efficiently monitor the cable force at each moment, it accurately obtains the cable force change during the construction process of prestressed tensioning. In addition, the monitoring range of the self-sensing anchor cable is its full length. Given the cable-force growth curve of each measuring point, the anchoring effect of the corresponding part of the anchor cable and the rock and soil mass can be inferred. The long-term monitoring results indicate that the self-sensing anchor cable synchronously responds to changes in the displacement and deformation of the supporting structure accurately. Therefore, it provides reliable data support for the quality and safety of anchor cable engineering.
2022, 52(10): 94-99,110.
doi: 10.13204/j.gyjzG22073006
Abstract:
The ultra-long concrete structure produces internal force and deformation with temperature change and concrete shrinkage, which results in the cracking of horizontal structure specimens exceeding the tensile strength of the concrete. For an ultra-long round concrete stadium with a perimeter of about 670 m, the crack resistance of the main structure under different measures in construction was studied. Three-dimensional modeling was performed on the concrete structure of the first floor of the stadium by finite element software, and the construction process was realized through the birth and death element method. The contraction of the concrete in the main structure, as well as the expansion and the time-dependent elastic modulus of the concrete in the post-pouring belt were defined based on the subprogram. The simulation results show that when the east and west sides of the round structure are constructed from north to south in succession and finally integrated, concrete slabs at the northern corner of the early poured structure show the highest stress level because of temperature reduction and shrinkage. In addition, the expanded concrete in the post-pouring belt can effectively compensate for tensile stress and control cracks. The adjustment of structural integration time on days with low temperatures can greatly alleviate the influence of temperature on the structure. Furthermore, a rational construction sequence of the post-pouring belt can avoid the accumulation of plate stress along the structural length.
The ultra-long concrete structure produces internal force and deformation with temperature change and concrete shrinkage, which results in the cracking of horizontal structure specimens exceeding the tensile strength of the concrete. For an ultra-long round concrete stadium with a perimeter of about 670 m, the crack resistance of the main structure under different measures in construction was studied. Three-dimensional modeling was performed on the concrete structure of the first floor of the stadium by finite element software, and the construction process was realized through the birth and death element method. The contraction of the concrete in the main structure, as well as the expansion and the time-dependent elastic modulus of the concrete in the post-pouring belt were defined based on the subprogram. The simulation results show that when the east and west sides of the round structure are constructed from north to south in succession and finally integrated, concrete slabs at the northern corner of the early poured structure show the highest stress level because of temperature reduction and shrinkage. In addition, the expanded concrete in the post-pouring belt can effectively compensate for tensile stress and control cracks. The adjustment of structural integration time on days with low temperatures can greatly alleviate the influence of temperature on the structure. Furthermore, a rational construction sequence of the post-pouring belt can avoid the accumulation of plate stress along the structural length.
2022, 52(10): 100-105.
doi: 10.13204/j.gyjzG22042613
Abstract:
A concrete frame structure needs to be reconstructed due to functional updating. In order to meet the requirements of large space, massive columns, beams, and plates need to be demolished, which indicates a high safety risk. Therefore, finite element analysis was carried out to simulate structural state changes during the demolition and optimize reconstruction and monitoring schemes. During the reconstruction, automatic monitoring and manual inspection were adopted to monitor the inclination, settlement, deflection, and damage of the structure. It is shown that the measured values are in good agreement with the construction simulation and analysis results, and there is no alarm and no obvious structural damage during the monitoring period. The combination of construction simulation and monitoring can effectively reduce structural safety risks during the reconstruction.
A concrete frame structure needs to be reconstructed due to functional updating. In order to meet the requirements of large space, massive columns, beams, and plates need to be demolished, which indicates a high safety risk. Therefore, finite element analysis was carried out to simulate structural state changes during the demolition and optimize reconstruction and monitoring schemes. During the reconstruction, automatic monitoring and manual inspection were adopted to monitor the inclination, settlement, deflection, and damage of the structure. It is shown that the measured values are in good agreement with the construction simulation and analysis results, and there is no alarm and no obvious structural damage during the monitoring period. The combination of construction simulation and monitoring can effectively reduce structural safety risks during the reconstruction.
2022, 52(10): 106-110.
doi: 10.13204/j.gyjzG20110607
Abstract:
In order to realize the intelligent monitoring of the incremental launching construction of a precast frame bridge, this paper took the incremental launching construction of the frame bridge in Shanjuan road under Changde-Zhangjiajie expressway in Changde of Hunan Province as the engineering background and established an intelligent monitoring system for the incremental launching construction of the precast frame bridge based on BeiDou positioning technology. In addition, the paper monitored the displacement of the precast frame bridge and the settlement of the existing pavement during the incremental launching construction and analyzed the monitoring data. The research shows that the intelligent monitoring system for the incremental launching construction of the precast frame bridge based on BeiDou positioning technology realizes the real-time monitoring of data, and the system can perform automatic analysis and processing through programs. In addition, its analysis and feedback speeds are greatly improved, and the efficiency is high.
In order to realize the intelligent monitoring of the incremental launching construction of a precast frame bridge, this paper took the incremental launching construction of the frame bridge in Shanjuan road under Changde-Zhangjiajie expressway in Changde of Hunan Province as the engineering background and established an intelligent monitoring system for the incremental launching construction of the precast frame bridge based on BeiDou positioning technology. In addition, the paper monitored the displacement of the precast frame bridge and the settlement of the existing pavement during the incremental launching construction and analyzed the monitoring data. The research shows that the intelligent monitoring system for the incremental launching construction of the precast frame bridge based on BeiDou positioning technology realizes the real-time monitoring of data, and the system can perform automatic analysis and processing through programs. In addition, its analysis and feedback speeds are greatly improved, and the efficiency is high.
2022, 52(10): 111-114,188.
doi: 10.13204/j.gyjzG22041104
Abstract:
The quality deterioration degree of modern brick-wood houses in Shanghai is affected by various factors and involves a large amount of data. Since indicators are ordered categorical variables, and there is a correlation between them, the principal component analysis method and the weighting method of complex correlation coefficient in the big data analysis technology were applied to quantitatively evaluate the quality deterioration of the modern brick-wood houses in Shanghai, so as to improve the accuracy of evaluation results. Firstly, material strength and component damage were selected as the evaluation indicators of the quality deterioration of the houses. On this basis, the principal component analysis method and the weighting method of the complex correlation coefficient were used to analyze the data of evaluation indicators, and the final evaluation results were obtained. As a result, the quality deterioration of the modern brick-wood houses in Shanghai was evaluated. The evaluation results of an engineering example show that the evaluation values of the principal component analysis method and the weighting method of the complex correlation coefficient are relatively close, and they are consistent with the actual measured results, which confirms the feasibility of the two methods.
The quality deterioration degree of modern brick-wood houses in Shanghai is affected by various factors and involves a large amount of data. Since indicators are ordered categorical variables, and there is a correlation between them, the principal component analysis method and the weighting method of complex correlation coefficient in the big data analysis technology were applied to quantitatively evaluate the quality deterioration of the modern brick-wood houses in Shanghai, so as to improve the accuracy of evaluation results. Firstly, material strength and component damage were selected as the evaluation indicators of the quality deterioration of the houses. On this basis, the principal component analysis method and the weighting method of the complex correlation coefficient were used to analyze the data of evaluation indicators, and the final evaluation results were obtained. As a result, the quality deterioration of the modern brick-wood houses in Shanghai was evaluated. The evaluation results of an engineering example show that the evaluation values of the principal component analysis method and the weighting method of the complex correlation coefficient are relatively close, and they are consistent with the actual measured results, which confirms the feasibility of the two methods.
2022, 52(10): 115-121.
doi: 10.13204/j.gyjzG22071808
Abstract:
In order to regulate the early shrinkage and cracking of the concrete, the influence of combined expansive agent and internal curing water of super absorbent polymer (SAP) on the regulation laws of early shrinkage and mechanical strength of concrete were investigated in this study. Specifically, this study analyzed the concrete in which the expansive agent and internal curing water with a combined dosage accounting for 0%, 3%, 6%, and 9% of the total mass of the binding material are added. In addition, the study tested the early free deformation, compressive strength, splitting tensile strength, and drying-induced water loss rate. The results show that as the combined dosage of the expansive agent and internal curing water increases, the free deformation curve of concrete in the first three days gradually evolves from W-shaped to L-shaped, and the concrete autogenous and drying shrinkage decreases gradually in 28 days until an expansion up to 1 310×10-6 is noticed in the group with a combined dosage of 9% under sealed curing condition. However, the net drying shrinkage of all groups cannot be eliminated, and the mechanical strength of the concrete decreases gradually in 28 days. Furthermore, the drying-induced water loss rate is linearly correlated to the net drying shrinkage of concrete from three days to 28 days. According to experimental results, the group with a combined dosage of 6% is optimal in this study.
In order to regulate the early shrinkage and cracking of the concrete, the influence of combined expansive agent and internal curing water of super absorbent polymer (SAP) on the regulation laws of early shrinkage and mechanical strength of concrete were investigated in this study. Specifically, this study analyzed the concrete in which the expansive agent and internal curing water with a combined dosage accounting for 0%, 3%, 6%, and 9% of the total mass of the binding material are added. In addition, the study tested the early free deformation, compressive strength, splitting tensile strength, and drying-induced water loss rate. The results show that as the combined dosage of the expansive agent and internal curing water increases, the free deformation curve of concrete in the first three days gradually evolves from W-shaped to L-shaped, and the concrete autogenous and drying shrinkage decreases gradually in 28 days until an expansion up to 1 310×10-6 is noticed in the group with a combined dosage of 9% under sealed curing condition. However, the net drying shrinkage of all groups cannot be eliminated, and the mechanical strength of the concrete decreases gradually in 28 days. Furthermore, the drying-induced water loss rate is linearly correlated to the net drying shrinkage of concrete from three days to 28 days. According to experimental results, the group with a combined dosage of 6% is optimal in this study.
2022, 52(10): 122-130.
doi: 10.13204/j.gyjzG22072710
Abstract:
Deficient circular and square concrete-filled steel tube (CFST) columns can be reinforced with outer steel tubes effectively. In this paper, ABAQUS was utilized to establish finite element models for the circular and square CFST columns reinforced with outer steel tubes, respectively, and the models were validated through tests. Furthermore, the effects of the column end length, the thickness and strength of sandwich materials, the ratio of diameter and thickness and the yield strength of steel tubes, and the core concrete strength on the axial compression performance of the CFST columns reinforced with outer steel tubes were analyzed. The results show that no extra strengthening configuration is needed for the column with the diameter greater than 300 mm if the column end length is less than 60 mm. The low thickness and high strength of the sandwich materials can guarantee the reinforcement effect of the outer steel tubes. In addition, a small ratio of the diameter and thickness of the outer steel tubes, large ratio of the diameter and thickness of inner steel tubes, and low core concrete strength can improve the reinforcement effect of the outer steel tubes. According to the superposition method, methods for calculating the axial compression bearing capacity of the circular and square CFST columns reinforced with the outer steel tubes were proposed, and the prediction results are in good agreement with the test and finite element results.
Deficient circular and square concrete-filled steel tube (CFST) columns can be reinforced with outer steel tubes effectively. In this paper, ABAQUS was utilized to establish finite element models for the circular and square CFST columns reinforced with outer steel tubes, respectively, and the models were validated through tests. Furthermore, the effects of the column end length, the thickness and strength of sandwich materials, the ratio of diameter and thickness and the yield strength of steel tubes, and the core concrete strength on the axial compression performance of the CFST columns reinforced with outer steel tubes were analyzed. The results show that no extra strengthening configuration is needed for the column with the diameter greater than 300 mm if the column end length is less than 60 mm. The low thickness and high strength of the sandwich materials can guarantee the reinforcement effect of the outer steel tubes. In addition, a small ratio of the diameter and thickness of the outer steel tubes, large ratio of the diameter and thickness of inner steel tubes, and low core concrete strength can improve the reinforcement effect of the outer steel tubes. According to the superposition method, methods for calculating the axial compression bearing capacity of the circular and square CFST columns reinforced with the outer steel tubes were proposed, and the prediction results are in good agreement with the test and finite element results.
2022, 52(10): 131-138.
doi: 10.13204/j.gyjzG22073005
Abstract:
Concrete structures in coastal areas, salt lakes, and deicing salt areas are seriously eroded by chloride ions, which has caused great economic losses. Traditional chloride transport models based on Fick's second law fail to consider influencing factors comprehensively and cannot reflect the transport behavior of chloride ions in field engineering. In addition, the chloride transport model based on the Nernst-Plank equation takes into account the synergy of multiple factors, but its equation is difficult to be solved, which thus limits its application in engineering. According to the Nernst-Plank equation, this study analyzed the multi-ion transport model of cement-based materials under erosion and carried out an unsteady state electromigration test of the chlorine ions and a moisture transport test of the concrete. In addition, the study considered the composition of the concrete mixture, the physical and chemical properties of binding materials, and the service environment characteristics of the structure and simulated the chloride transport process in ordinary concrete and internal curing concrete by using the STADIUM® software. The results show that internal curing can improve the resistance of concrete to ion erosion and prolong the service life of the concrete structures, but the improvement is limited in the later stage. Furthermore, STADIUM® software can better simulate the transport behavior of chloride ions in concrete, which provides a convenient method for predicting the life of concrete structures.
Concrete structures in coastal areas, salt lakes, and deicing salt areas are seriously eroded by chloride ions, which has caused great economic losses. Traditional chloride transport models based on Fick's second law fail to consider influencing factors comprehensively and cannot reflect the transport behavior of chloride ions in field engineering. In addition, the chloride transport model based on the Nernst-Plank equation takes into account the synergy of multiple factors, but its equation is difficult to be solved, which thus limits its application in engineering. According to the Nernst-Plank equation, this study analyzed the multi-ion transport model of cement-based materials under erosion and carried out an unsteady state electromigration test of the chlorine ions and a moisture transport test of the concrete. In addition, the study considered the composition of the concrete mixture, the physical and chemical properties of binding materials, and the service environment characteristics of the structure and simulated the chloride transport process in ordinary concrete and internal curing concrete by using the STADIUM® software. The results show that internal curing can improve the resistance of concrete to ion erosion and prolong the service life of the concrete structures, but the improvement is limited in the later stage. Furthermore, STADIUM® software can better simulate the transport behavior of chloride ions in concrete, which provides a convenient method for predicting the life of concrete structures.
2022, 52(10): 139-145.
doi: 10.13204/j.gyjzG22042907
Abstract:
As China's urban regeneration continues, old industrial buildings are being renovated in full swing. At present, the renovation mainly focuses on function replacement, architecture form, and spatial layout, but it fails to consider the improvement of indoor physical environments, which thus leads to poor daylighting in buildings in use. In addition, related research in China does not analyze the indoor daylighting effect of renovated old industrial buildings or the optimization strategy for multi-factor variables. This paper took the dining hall in Sesame Street in Zhengzhou as the research object, found the problems through field investigation and measurement, and selected an appropriate optimization strategy. Furthermore, the paper carried out simulation analysis and verification through GBSWARE software simulation and orthogonal experiment and performed comprehensive evaluation in terms of daylighting factor, dynamic daylighting hours, and daylighting compliance rate in inner areas, so as to obtain an optimal factor combination under boundary conditions. The results show that the size of an atrium is a significant factor for indoor daylighting optimization of renovated old industrial buildings with large spans, and the atrium can effectively improve indoor natural daylighting.
As China's urban regeneration continues, old industrial buildings are being renovated in full swing. At present, the renovation mainly focuses on function replacement, architecture form, and spatial layout, but it fails to consider the improvement of indoor physical environments, which thus leads to poor daylighting in buildings in use. In addition, related research in China does not analyze the indoor daylighting effect of renovated old industrial buildings or the optimization strategy for multi-factor variables. This paper took the dining hall in Sesame Street in Zhengzhou as the research object, found the problems through field investigation and measurement, and selected an appropriate optimization strategy. Furthermore, the paper carried out simulation analysis and verification through GBSWARE software simulation and orthogonal experiment and performed comprehensive evaluation in terms of daylighting factor, dynamic daylighting hours, and daylighting compliance rate in inner areas, so as to obtain an optimal factor combination under boundary conditions. The results show that the size of an atrium is a significant factor for indoor daylighting optimization of renovated old industrial buildings with large spans, and the atrium can effectively improve indoor natural daylighting.
2022, 52(10): 146-155,138.
doi: 10.13204/j.gyjzG22071409
Abstract:
The composite shear wall of concrete filled steel tube (CFST) reinforced with corrugated steel plates is a new structural lateral force resistance system. It adopts a design featuring separate load-bearing and lateral force resistance and fully exerts the performance of materials, with a remarkable composite effect. Therefore, the composite shear wall can be used to strengthen the lateral force resistance stiffness of reinforced CFST structures and improve the anti-seismic performance of the structures. In order to study the anti-seismic performance of the composite shear wall, finite element (FE) numerical simulation parameters were first calibrated according to experimental phenomena. Then, in view of the FE simulation results of 12 specimens in three groups, anti-seismic performance parameters such as elastic-plastic force and deformation laws, failure modes, hysteresis characteristics, and energy dissipation capacity were studied when the composite shear wall was subjected to multilevel and horizontal reciprocating loads. Finally, the effect of different axial compression ratios, shear-to-span ratios, and corrugated steel plate thicknesses on the anti-seismic performance of the composite shear wall was analyzed. The results show that the lateral mechanical behavior of the composite shear wall shows a distinct two-stage characteristic. Specifically, it has a full hysteretic curve, slow strength degradation, positive energy dissipation capacity, and high ultimate displacement angle and displacement ductility. In addition, it is found that an increase in axial compression ratio can improve the ultimate bearing capacity, but this will lead to a rapid decrease in the bearing capacity in the second phase. Furthermore, the shear-to-span ratio mainly affects the failure mode of the composite shear wall, and the reasonable height-to-thickness ratio of the corrugated steel plate should vary from 500 to 800.
The composite shear wall of concrete filled steel tube (CFST) reinforced with corrugated steel plates is a new structural lateral force resistance system. It adopts a design featuring separate load-bearing and lateral force resistance and fully exerts the performance of materials, with a remarkable composite effect. Therefore, the composite shear wall can be used to strengthen the lateral force resistance stiffness of reinforced CFST structures and improve the anti-seismic performance of the structures. In order to study the anti-seismic performance of the composite shear wall, finite element (FE) numerical simulation parameters were first calibrated according to experimental phenomena. Then, in view of the FE simulation results of 12 specimens in three groups, anti-seismic performance parameters such as elastic-plastic force and deformation laws, failure modes, hysteresis characteristics, and energy dissipation capacity were studied when the composite shear wall was subjected to multilevel and horizontal reciprocating loads. Finally, the effect of different axial compression ratios, shear-to-span ratios, and corrugated steel plate thicknesses on the anti-seismic performance of the composite shear wall was analyzed. The results show that the lateral mechanical behavior of the composite shear wall shows a distinct two-stage characteristic. Specifically, it has a full hysteretic curve, slow strength degradation, positive energy dissipation capacity, and high ultimate displacement angle and displacement ductility. In addition, it is found that an increase in axial compression ratio can improve the ultimate bearing capacity, but this will lead to a rapid decrease in the bearing capacity in the second phase. Furthermore, the shear-to-span ratio mainly affects the failure mode of the composite shear wall, and the reasonable height-to-thickness ratio of the corrugated steel plate should vary from 500 to 800.
2022, 52(10): 156-160,203.
doi: 10.13204/j.gyjzG22072920
Abstract:
Timber-concrete composite structure can significantly improve the structural performance of timber buildings and can be widely mostly used in multi-story and high-rise timber buildings. However, due to the lack of research on the vibration performance of timber-concrete composite floor systems, effective design bases are still not available at present. Steel bar truss slabs have been widely used in prefabricated concrete structures. In this regard, the dynamic properties of timber-concrete composite beams using steel bar truss slabs were explored experimentally. Through the push-out test, the anti-shear performance of shear connectors was obtained, and the flexural rigidity of the composite beams was calculated. Furthermore, through dynamic tests, the dynamic properties such as natural vibration frequency and damping ratio of the composite beams were obtained. In addition, according to theoretical calculation, the effects of connector types and steel bar truss slabs on the dynamic properties of the composite beams were analyzed, and the comfortability of the composite beams and the accuracy of calculation models were evaluated based on existing standards.
Timber-concrete composite structure can significantly improve the structural performance of timber buildings and can be widely mostly used in multi-story and high-rise timber buildings. However, due to the lack of research on the vibration performance of timber-concrete composite floor systems, effective design bases are still not available at present. Steel bar truss slabs have been widely used in prefabricated concrete structures. In this regard, the dynamic properties of timber-concrete composite beams using steel bar truss slabs were explored experimentally. Through the push-out test, the anti-shear performance of shear connectors was obtained, and the flexural rigidity of the composite beams was calculated. Furthermore, through dynamic tests, the dynamic properties such as natural vibration frequency and damping ratio of the composite beams were obtained. In addition, according to theoretical calculation, the effects of connector types and steel bar truss slabs on the dynamic properties of the composite beams were analyzed, and the comfortability of the composite beams and the accuracy of calculation models were evaluated based on existing standards.
2022, 52(10): 161-167,228.
doi: 10.13204/j.gyjzG22030414
Abstract:
High ductile concrete (HDC) has positive ductility, bond property, and damage resistance feature. Therefore, it can be used to reinforce damaged concrete beams, which can not only improve the bearing capacity of the beams, but also prevent the further development of cracks. This paper used HDC for surface reinforcement, tested the flexural property of five earthquake-damaged concrete beams reinforced with HDC, and studied the bearing and deformation capacity of the earthquake-damaged concrete beams reinforced with HDC, as well as the internal damage of the concrete. The experimental results show that the bearing capacity and deformation capacity of the earthquake-damaged concrete beams reinforced with HDC are greatly improved. The bearing capacity of reinforced RCL1-RCL5 is increased by 86.1%, 75.7%, 56.0%, 84.4%, and 65.7%, respectively, and the corresponding load of the initial crack is increased by 36.4%, 86.6%, 64.3%, 28.9%, and 29.7%, respectively. By comparing the earthquake-damaged concrete beams reinforced with HDC before and after the failure, this paper finds that HDC has shown positive bond and damage resistance properties, and both the original concrete and HDC are subjected to forces and deform. According to the study on the flexural property of earthquake-damaged concrete beams reinforced with HDC, the calculation formula of the flexural capacity of the earthquake-damaged concrete beams reinforced with HDC is deduced, and the calculated results agree with the experimental ones.
High ductile concrete (HDC) has positive ductility, bond property, and damage resistance feature. Therefore, it can be used to reinforce damaged concrete beams, which can not only improve the bearing capacity of the beams, but also prevent the further development of cracks. This paper used HDC for surface reinforcement, tested the flexural property of five earthquake-damaged concrete beams reinforced with HDC, and studied the bearing and deformation capacity of the earthquake-damaged concrete beams reinforced with HDC, as well as the internal damage of the concrete. The experimental results show that the bearing capacity and deformation capacity of the earthquake-damaged concrete beams reinforced with HDC are greatly improved. The bearing capacity of reinforced RCL1-RCL5 is increased by 86.1%, 75.7%, 56.0%, 84.4%, and 65.7%, respectively, and the corresponding load of the initial crack is increased by 36.4%, 86.6%, 64.3%, 28.9%, and 29.7%, respectively. By comparing the earthquake-damaged concrete beams reinforced with HDC before and after the failure, this paper finds that HDC has shown positive bond and damage resistance properties, and both the original concrete and HDC are subjected to forces and deform. According to the study on the flexural property of earthquake-damaged concrete beams reinforced with HDC, the calculation formula of the flexural capacity of the earthquake-damaged concrete beams reinforced with HDC is deduced, and the calculated results agree with the experimental ones.
2022, 52(10): 168-175,145.
doi: 10.13204/j.gyjzG22052104
Abstract:
In order to scientifically and reasonably study the design optimization of RC simply-supported T-beams with external prestressing reinforcement, a design optimization method for external prestressing reinforcement based on the target reliability was proposed, which fully considered the uncertainty and variability of the geometric design values during the external prestressing deployment. In addition, finite element analysis software was used to calculate the structural reliability of the beams with external prestressing reinforcement based on the six sigma theory, and a response surface method was adopted to analyze the influence of random design variables (equivalent diameter of steel tendon, included angle of steel tendon, fillet radius of steel tendon, bend length of steel tendon, and tensile strength design value of steel strand) on the reliability of the simply-supported T-beams with external prestressing reinforcement. The results show that the reliability of the simply-supported T-beams with external prestressing reinforcement is highly related to the equivalent diameter of the steel tendon with external prestressing reinforcement. In addition, recommended design values for random variables with external prestressing reinforcement were given, which took into account the target reliability indicators for the first level of safety of concrete bridges in use and were verified by an on-site bridge reinforcement project. Furthermore, the span deflection and strain were well controlled in two static load tests, with minimum calibration factors of 0.72 and 0.73, respectively.
In order to scientifically and reasonably study the design optimization of RC simply-supported T-beams with external prestressing reinforcement, a design optimization method for external prestressing reinforcement based on the target reliability was proposed, which fully considered the uncertainty and variability of the geometric design values during the external prestressing deployment. In addition, finite element analysis software was used to calculate the structural reliability of the beams with external prestressing reinforcement based on the six sigma theory, and a response surface method was adopted to analyze the influence of random design variables (equivalent diameter of steel tendon, included angle of steel tendon, fillet radius of steel tendon, bend length of steel tendon, and tensile strength design value of steel strand) on the reliability of the simply-supported T-beams with external prestressing reinforcement. The results show that the reliability of the simply-supported T-beams with external prestressing reinforcement is highly related to the equivalent diameter of the steel tendon with external prestressing reinforcement. In addition, recommended design values for random variables with external prestressing reinforcement were given, which took into account the target reliability indicators for the first level of safety of concrete bridges in use and were verified by an on-site bridge reinforcement project. Furthermore, the span deflection and strain were well controlled in two static load tests, with minimum calibration factors of 0.72 and 0.73, respectively.
2022, 52(10): 176-181,194.
doi: 10.13204/j.gyjzG22050206
Abstract:
H-shaped steel bolted welded joints have excellent welding performance and are widely used in steel buildings. However, during the construction, the joints often show welding defects such as misalignment, air holes, and slag inclusion, which do not meet the requirements of acceptance specifications and seriously affect structural safety. In order to ensure the safe use of structures, it is necessary to study the method for accurately evaluating the bearing capacity and the reinforcement technology in a confined space of the defective H-shaped steel bolted welded joints. In this paper, defective welds were quantitatively classified into different levels, and a method for accurately evaluating the residual bearing capacity of joints by using the effective part of the defective welds, bolt friction, and compressive capacity of the defective welds was proposed. In addition, joints of five commonly used beams with different defective welds were evaluated, and the evaluation results of the bearing capacity of each joint were given. According to the evaluation results, a bending reinforcement method of H-shaped bolted welded joints was proposed, which changed H-shaped structures into III-shaped sections in a confined space. The research results can provide a reference for the identification and reinforcement of defective H-shaped steel bolted welded, as well as the revision of reinforcement codes of steel structure joints in China.
H-shaped steel bolted welded joints have excellent welding performance and are widely used in steel buildings. However, during the construction, the joints often show welding defects such as misalignment, air holes, and slag inclusion, which do not meet the requirements of acceptance specifications and seriously affect structural safety. In order to ensure the safe use of structures, it is necessary to study the method for accurately evaluating the bearing capacity and the reinforcement technology in a confined space of the defective H-shaped steel bolted welded joints. In this paper, defective welds were quantitatively classified into different levels, and a method for accurately evaluating the residual bearing capacity of joints by using the effective part of the defective welds, bolt friction, and compressive capacity of the defective welds was proposed. In addition, joints of five commonly used beams with different defective welds were evaluated, and the evaluation results of the bearing capacity of each joint were given. According to the evaluation results, a bending reinforcement method of H-shaped bolted welded joints was proposed, which changed H-shaped structures into III-shaped sections in a confined space. The research results can provide a reference for the identification and reinforcement of defective H-shaped steel bolted welded, as well as the revision of reinforcement codes of steel structure joints in China.
2022, 52(10): 182-188.
doi: 10.13204/j.gyjzG22062717
Abstract:
This paper analyzed the topographic and geological characteristics, deformation process and trend, landslide causes, stability, treatment plan, and monitoring data of the Zhengjiayuan tunnel-landslide oblique system. In addition, a comprehensive treatment plan was given, which could be described as unloading the landslide mass, ramming and grouting cracks, setting up anti-sliding piles and anchor-cable anti-sliding piles on the left and right sides of the tunnel crossing the sliding surface respectively, canceling the short subgrade before the tunnel to connect the bridge and tunnel, intercepting and draining away water in the surface and internal part of the landslide, and reinforcing local landslide protection. The tunnel-landslide oblique system is a typical three-dimensional structure. When the tunnel body is closer to the sliding surface, the stability of the landslide will be worse, and the damage caused by the landslide to the tunnel will be more serious. In terms of the influence of spatial location relationship on landslide stability, the traverse on the sliding surface is larger than that on the sliding bed. When the overlying soil layer of the tunnel-landslide oblique system is thick, and the sliding surface is steep, the vertical deformation of the tunnel is greater than the horizontal deformation. When the overlying soil layer is thin, and the sliding surface is gentle, the horizontal deformation is greater than the vertical deformation. When the tunnel passes through the landslide mass, especially the sliding surface, weak blasting and short footage construction should be adopted, and the support parameters should be strengthened. The time consumed by each construction process should be shortened, and the quick closure of the tunnel lining should be emphasized. Furthermore, the monitoring and measurement should be improved and encrypted. Zhengjiayuan tunnel-landslide has undergone heavy rains, and it is generally stable and shows a positive control effect. Therefore, it is necessary to combine automatic monitoring and manual inspection to complement each other and give full play to their advantages, so as to jointly ensure the safety of structures.
This paper analyzed the topographic and geological characteristics, deformation process and trend, landslide causes, stability, treatment plan, and monitoring data of the Zhengjiayuan tunnel-landslide oblique system. In addition, a comprehensive treatment plan was given, which could be described as unloading the landslide mass, ramming and grouting cracks, setting up anti-sliding piles and anchor-cable anti-sliding piles on the left and right sides of the tunnel crossing the sliding surface respectively, canceling the short subgrade before the tunnel to connect the bridge and tunnel, intercepting and draining away water in the surface and internal part of the landslide, and reinforcing local landslide protection. The tunnel-landslide oblique system is a typical three-dimensional structure. When the tunnel body is closer to the sliding surface, the stability of the landslide will be worse, and the damage caused by the landslide to the tunnel will be more serious. In terms of the influence of spatial location relationship on landslide stability, the traverse on the sliding surface is larger than that on the sliding bed. When the overlying soil layer of the tunnel-landslide oblique system is thick, and the sliding surface is steep, the vertical deformation of the tunnel is greater than the horizontal deformation. When the overlying soil layer is thin, and the sliding surface is gentle, the horizontal deformation is greater than the vertical deformation. When the tunnel passes through the landslide mass, especially the sliding surface, weak blasting and short footage construction should be adopted, and the support parameters should be strengthened. The time consumed by each construction process should be shortened, and the quick closure of the tunnel lining should be emphasized. Furthermore, the monitoring and measurement should be improved and encrypted. Zhengjiayuan tunnel-landslide has undergone heavy rains, and it is generally stable and shows a positive control effect. Therefore, it is necessary to combine automatic monitoring and manual inspection to complement each other and give full play to their advantages, so as to jointly ensure the safety of structures.
2022, 52(10): 189-194.
doi: 10.13204/j.gyjzG22073102
Abstract:
To improve the overall performance of the subway station, Shenzhen Huangmugang transportation hub project needs to comprehensively renovate a long wall of 456.7 m of the operating subway station on three floors of the basement. In order to ensure operational security, a three-dimensional incremental finite element method was applied to study the construction mechanical behavior of the large-scale comprehensive renovation of the operating subway station. The results show that:1) The excavation of adjacent foundation pits in the existing station leads to the increase in the mid-span moment of the roof and baseboard, the moment of the frame column, and the horizontal displacement of the station. Therefore, it's necessary to optimize the support scheme of adjacent foundation pits to control the internal force and deformation of the existing structure. 2) The precipitation in the existing station can decrease the increment of the mid-span moment of the baseboard and the axial force of temporary columns. 3) As the layer number and span in the comprehensive existing side wall opening increase, the internal force and deformation of the existing station significantly improve. In addition, the increase in moment and deformation of existing structural plates can be decreased effectively by setting up temporary columns for pre-support. 4) In order to control the stress and deformation of the existing station, the scheme featuring precipitation and the establishment of temporary columns for renovation is relatively optimal.
To improve the overall performance of the subway station, Shenzhen Huangmugang transportation hub project needs to comprehensively renovate a long wall of 456.7 m of the operating subway station on three floors of the basement. In order to ensure operational security, a three-dimensional incremental finite element method was applied to study the construction mechanical behavior of the large-scale comprehensive renovation of the operating subway station. The results show that:1) The excavation of adjacent foundation pits in the existing station leads to the increase in the mid-span moment of the roof and baseboard, the moment of the frame column, and the horizontal displacement of the station. Therefore, it's necessary to optimize the support scheme of adjacent foundation pits to control the internal force and deformation of the existing structure. 2) The precipitation in the existing station can decrease the increment of the mid-span moment of the baseboard and the axial force of temporary columns. 3) As the layer number and span in the comprehensive existing side wall opening increase, the internal force and deformation of the existing station significantly improve. In addition, the increase in moment and deformation of existing structural plates can be decreased effectively by setting up temporary columns for pre-support. 4) In order to control the stress and deformation of the existing station, the scheme featuring precipitation and the establishment of temporary columns for renovation is relatively optimal.
2022, 52(10): 195-203.
doi: 10.13204/j.gyjzG22073009
Abstract:
As the process of social informatization accelerates, information technologies have gradually become an important means for construction practitioners to improve the quality of engineering management. As a key component of the digital development of the construction industry, building information modeling (BIM) has been widely applied in engineering management. How to further develop information technologies for engineering management on the basis of existing theories and applications has thus become the focus of researchers' attention. This paper summarized BIM-related research from two aspects:the organization and processing of engineering data as well as the mining and analysis of such data. The research investigated involved the Industry Foundation Classes (IFC) standard, multi-scale information models, model lightweighting technology, and the key steps and typical methods of data mining in the engineering industry. On this basis, the bottleneck problems faced by BIM and information technologies for engineering were analyzed, and three main future development directions were then proposed and discussed:digital twins in the engineering industry, city information models, and knowledge graphs in the engineering industry. This paper is expected to provide a reference for further research and technology application.
As the process of social informatization accelerates, information technologies have gradually become an important means for construction practitioners to improve the quality of engineering management. As a key component of the digital development of the construction industry, building information modeling (BIM) has been widely applied in engineering management. How to further develop information technologies for engineering management on the basis of existing theories and applications has thus become the focus of researchers' attention. This paper summarized BIM-related research from two aspects:the organization and processing of engineering data as well as the mining and analysis of such data. The research investigated involved the Industry Foundation Classes (IFC) standard, multi-scale information models, model lightweighting technology, and the key steps and typical methods of data mining in the engineering industry. On this basis, the bottleneck problems faced by BIM and information technologies for engineering were analyzed, and three main future development directions were then proposed and discussed:digital twins in the engineering industry, city information models, and knowledge graphs in the engineering industry. This paper is expected to provide a reference for further research and technology application.
2022, 52(10): 204-210,235.
doi: 10.13204/j.gyjzG22073107
Abstract:
The process of mapping data from a building operation and maintenance system to building digital twins is exposed to various problems, such as discrete data, multi-source heterogeneous data, and poorly effective queries, and so on. To solve those problems, a new approach to fusion of building operation and maintenance data was designed and a data fusion system based on digital twins in the aspects of the preparation, access, transformation, integration, and visualization, and etc of building operation and maintenance data. The custom Source Function operator of Flink, data transformation and mapping configurations, and the self-developed stream processing engine and online analytical processing (OLAP) engine were employed to solve the above three issues of building operation and maintenance systems. Finally, a grade-A tertiary hospital in Qingdao was discussed as an example of practical application. The results supported the following conclusions:The proposed data fusion approach could fully meet the various data fusion requirements of the building operation and maintenance system; the proposed data fusion system was capable of successfully accessing, transforming, storing, and visualizing the hospital's over three billion pieces of data from various fields; the proposed data fusion approach also laid a foundation for research and application of digital twin technology.
The process of mapping data from a building operation and maintenance system to building digital twins is exposed to various problems, such as discrete data, multi-source heterogeneous data, and poorly effective queries, and so on. To solve those problems, a new approach to fusion of building operation and maintenance data was designed and a data fusion system based on digital twins in the aspects of the preparation, access, transformation, integration, and visualization, and etc of building operation and maintenance data. The custom Source Function operator of Flink, data transformation and mapping configurations, and the self-developed stream processing engine and online analytical processing (OLAP) engine were employed to solve the above three issues of building operation and maintenance systems. Finally, a grade-A tertiary hospital in Qingdao was discussed as an example of practical application. The results supported the following conclusions:The proposed data fusion approach could fully meet the various data fusion requirements of the building operation and maintenance system; the proposed data fusion system was capable of successfully accessing, transforming, storing, and visualizing the hospital's over three billion pieces of data from various fields; the proposed data fusion approach also laid a foundation for research and application of digital twin technology.
2022, 52(10): 211-218.
doi: 10.13204/j.gyjzG22071916
Abstract:
To discover the damages to load-bearing wall structures caused by property owners' unauthorized reconstruction in residential buildings in a timely manner, this paper proposed a health monitoring method based on wavelet packet transform for building structures. The finite-element software ANSYS was used to build a calculation model for frame shear wall structures. Various damage conditions were simulated, and the acceleration responses at the measuring points on the structure were calculated. Furthermore, the software MATLAB was employed for the wavelet packet transform of the response signals at the measuring points and the calculation of the wavelet packet energy. Finally, the damage index DDE (curvature of the standard deviation of wavelet packet energy) was used for damage identification. The results show that the damage identification method combining wavelet packet energy and transform with damage index DDE can effectively monitor the damages to frame shear wall structures. The method can obtain damage monitoring results timely when a load-bearing wall structure is damaged, and better prevention and control effects can be achieved when the method is supported by early warning and alarm equipment.
To discover the damages to load-bearing wall structures caused by property owners' unauthorized reconstruction in residential buildings in a timely manner, this paper proposed a health monitoring method based on wavelet packet transform for building structures. The finite-element software ANSYS was used to build a calculation model for frame shear wall structures. Various damage conditions were simulated, and the acceleration responses at the measuring points on the structure were calculated. Furthermore, the software MATLAB was employed for the wavelet packet transform of the response signals at the measuring points and the calculation of the wavelet packet energy. Finally, the damage index DDE (curvature of the standard deviation of wavelet packet energy) was used for damage identification. The results show that the damage identification method combining wavelet packet energy and transform with damage index DDE can effectively monitor the damages to frame shear wall structures. The method can obtain damage monitoring results timely when a load-bearing wall structure is damaged, and better prevention and control effects can be achieved when the method is supported by early warning and alarm equipment.
2022, 52(10): 219-223,218.
doi: 10.13204/j.gyjzG22073011
Abstract:
The traditional management system for building maintenance work orders is highly likely to ignore the analysis of the textual description part of a work order. Consequently, valuable information is submerged in a large amount of messy data, which makes it difficult to extract repeated and high-frequency work orders quickly and accurately. To solve the above problem, this paper adopted a Chinese word segmentation algorithm based on a keyword library to properly segment the long textual description of repair content in building maintenance work orders. Then, the density detection algorithm based on K-means was employed to introduce the weight of each attribute of the work order and further calculate the weighted Euclidean distance between any two work orders. The density of each work order was obtained, and candidate repeated work order sets were extracted. Finally, the density-based spatial clustering of applications with noise (DBSCAN) algorithm was utilized to determine the final repeated work order set, and the proposed method was applied in an actual project for verification. The results show that the proposed method can accurately and effectively extract repeated work orders from a large amount of data, thereby improving the efficiency of analyzing building maintenance work orders and ultimately ensuring the level of refined logistics management.
The traditional management system for building maintenance work orders is highly likely to ignore the analysis of the textual description part of a work order. Consequently, valuable information is submerged in a large amount of messy data, which makes it difficult to extract repeated and high-frequency work orders quickly and accurately. To solve the above problem, this paper adopted a Chinese word segmentation algorithm based on a keyword library to properly segment the long textual description of repair content in building maintenance work orders. Then, the density detection algorithm based on K-means was employed to introduce the weight of each attribute of the work order and further calculate the weighted Euclidean distance between any two work orders. The density of each work order was obtained, and candidate repeated work order sets were extracted. Finally, the density-based spatial clustering of applications with noise (DBSCAN) algorithm was utilized to determine the final repeated work order set, and the proposed method was applied in an actual project for verification. The results show that the proposed method can accurately and effectively extract repeated work orders from a large amount of data, thereby improving the efficiency of analyzing building maintenance work orders and ultimately ensuring the level of refined logistics management.
2022, 52(10): 224-228.
doi: 10.13204/j.gyjzG22060707
Abstract:
To grasp the health status of overage transmission tower structures in real time, this paper built a wireless sensor network-based structural health status monitoring system for the four transmission towers currently in operation in Linyi, Shandong Province. The control parts and damage-sensitive parts of the tower structures were determined by finite-element analysis. The working stress, deformation, and vibration of the structures, foundation displacement and settlement, and other information about the health status of the structures were thereby monitored online in real time. The results show that the proposed monitoring system operates well and the monitored data on the strain, vibration, and settlement fluctuate steadily. Moreover, the health status of the tower structures exhibits no abnormality. In this way, the proposed system effectively guarantees the safe and stable operation of the transmission towers.
To grasp the health status of overage transmission tower structures in real time, this paper built a wireless sensor network-based structural health status monitoring system for the four transmission towers currently in operation in Linyi, Shandong Province. The control parts and damage-sensitive parts of the tower structures were determined by finite-element analysis. The working stress, deformation, and vibration of the structures, foundation displacement and settlement, and other information about the health status of the structures were thereby monitored online in real time. The results show that the proposed monitoring system operates well and the monitored data on the strain, vibration, and settlement fluctuate steadily. Moreover, the health status of the tower structures exhibits no abnormality. In this way, the proposed system effectively guarantees the safe and stable operation of the transmission towers.
2022, 52(10): 229-235.
doi: 10.13204/j.gyjzG22072610
Abstract:
This study is designed to accurately assess the probability of impact damage to downstream structures caused by debris flows after the dam failure of tailings reservoirs and the severity of the damage. Specifically, an impact risk assessment system for bridge projects was constructed according to the characteristics of the dam failure disaster of tailings reservoirs, the rheological characteristics of the debris flow after dam failure, and simulation technology. On the basis of this system, the two-dimensional (2D) cloud model theory was employed to generate the probability cloud and the severity cloud. For this purpose, weights were obtained with information entropies. Then, the evaluation cloud map was generated by the backward cloud model, and the left and right half clouds were generated by the standard cloud model. Finally, the similarity between the evaluation cloud and the standard cloud was determined by cloud similarity, and the actual safety status of each tailings reservoir was obtained by investigating the weights. A bridge project under impact damage by the debris flow after dam failure was discussed as an example of empirical research. The results show that the proposed risk assessment index system is highly practical, and the improved 2D cloud model can correct the weakness of the traditional cloud model that it directly removes the data at the interval breakpoint and thereby enhance the accuracy of the evaluation results and the comprehensiveness of the risk assessment process.
This study is designed to accurately assess the probability of impact damage to downstream structures caused by debris flows after the dam failure of tailings reservoirs and the severity of the damage. Specifically, an impact risk assessment system for bridge projects was constructed according to the characteristics of the dam failure disaster of tailings reservoirs, the rheological characteristics of the debris flow after dam failure, and simulation technology. On the basis of this system, the two-dimensional (2D) cloud model theory was employed to generate the probability cloud and the severity cloud. For this purpose, weights were obtained with information entropies. Then, the evaluation cloud map was generated by the backward cloud model, and the left and right half clouds were generated by the standard cloud model. Finally, the similarity between the evaluation cloud and the standard cloud was determined by cloud similarity, and the actual safety status of each tailings reservoir was obtained by investigating the weights. A bridge project under impact damage by the debris flow after dam failure was discussed as an example of empirical research. The results show that the proposed risk assessment index system is highly practical, and the improved 2D cloud model can correct the weakness of the traditional cloud model that it directly removes the data at the interval breakpoint and thereby enhance the accuracy of the evaluation results and the comprehensiveness of the risk assessment process.
2022, 52(10): 236-241.
doi: 10.13204/j.gyjzG22072810
Abstract:
Municipal facilities are an important part of urban management. Traditional municipal facility management and maintenance, mainly passive operation and maintenance in the form of "problem discovery and problem solving", is a weak link in refined urban management. On the basis of analyzing the demand of municipal facilities for intelligent management and maintenance, this paper designed the architecture of a smart management and maintenance system. Subsequently, a geographic information system (GIS) map-equipped cockpit module was developed for municipal facilities. Then, data from the edge-side collection system, road operation data, daily maintenance and emergency maintenance data were fused for the real-time operation data access. Deep learning technology was used for the intelligent identification and early warning of typical diseases, such as road cracks, potholes, stagnant water, and ice. The application in actual projects shows that the proposed municipal facility management and maintenance system based on GIS and artificial intelligence (AI) technologies can efficiently assist road and bridge disease identification and analysis of spatiotemporal evolution and development trends and it thus plays an important role in the efficient, high-standard, and intelligent development of municipal maintenance.
Municipal facilities are an important part of urban management. Traditional municipal facility management and maintenance, mainly passive operation and maintenance in the form of "problem discovery and problem solving", is a weak link in refined urban management. On the basis of analyzing the demand of municipal facilities for intelligent management and maintenance, this paper designed the architecture of a smart management and maintenance system. Subsequently, a geographic information system (GIS) map-equipped cockpit module was developed for municipal facilities. Then, data from the edge-side collection system, road operation data, daily maintenance and emergency maintenance data were fused for the real-time operation data access. Deep learning technology was used for the intelligent identification and early warning of typical diseases, such as road cracks, potholes, stagnant water, and ice. The application in actual projects shows that the proposed municipal facility management and maintenance system based on GIS and artificial intelligence (AI) technologies can efficiently assist road and bridge disease identification and analysis of spatiotemporal evolution and development trends and it thus plays an important role in the efficient, high-standard, and intelligent development of municipal maintenance.
2022, 52(10): 242-245.
doi: 10.13204/j.gyjzG21121316
Abstract:
The finite element method was used to simulate diversion canal slopes. The calculated displacement values and soil material mechanical parameter values were substituted into the input layer and output layer of the RBF neural network for training. The nonlinear relation between material parameters of multi-layer soils and displacement was obtained, and an intelligent inversion model of material parameters was established. According to monitoring displacement values at different times, the corresponding soil mechanical parameters were obtained by inversion analysis, and the parameters were used for finite element analysis to verify the accuracy of the inversion model. Combined with the inversion results, the safety factor of stability for diversion canal slopes at any time was calculated by the strength reduction method of finite elements, and the dynamic change law of slope stability was studied.
The finite element method was used to simulate diversion canal slopes. The calculated displacement values and soil material mechanical parameter values were substituted into the input layer and output layer of the RBF neural network for training. The nonlinear relation between material parameters of multi-layer soils and displacement was obtained, and an intelligent inversion model of material parameters was established. According to monitoring displacement values at different times, the corresponding soil mechanical parameters were obtained by inversion analysis, and the parameters were used for finite element analysis to verify the accuracy of the inversion model. Combined with the inversion results, the safety factor of stability for diversion canal slopes at any time was calculated by the strength reduction method of finite elements, and the dynamic change law of slope stability was studied.
2022, 52(10): 246-252,241.
doi: 10.13204/j.gyjzG22072603
Abstract:
Taking a 220 kV double-circuit suspension tower as the research object, this study built a finite-element tower-line system model to parametrically analyze the deformations and stresses of the tower lines in the cases of settlement and slip of the foundation as well as uniform and non-uniform icing. A dataset was created by extracting the displacements of the pivot points on the tower and those of the hanging points of the conductors and ground wires, as well as the stresses of the members. With the pivot points on the tower and the hanging points as the monitoring points, a surrogate model for calculating the stress of the tower was built with the displacements of the monitoring points as the inputs by utilizing the dataset created and the back-propagation (BP) neural network algorithm. A method of predicting the structural strength of the tower in real time by rapidly outputting the stresses of all the members of the tower on the basis of the displacements of the monitoring points and the surrogate model was proposed to pave the way for real-time perception of the operation status of transmission lines and safety early warning technologies.
Taking a 220 kV double-circuit suspension tower as the research object, this study built a finite-element tower-line system model to parametrically analyze the deformations and stresses of the tower lines in the cases of settlement and slip of the foundation as well as uniform and non-uniform icing. A dataset was created by extracting the displacements of the pivot points on the tower and those of the hanging points of the conductors and ground wires, as well as the stresses of the members. With the pivot points on the tower and the hanging points as the monitoring points, a surrogate model for calculating the stress of the tower was built with the displacements of the monitoring points as the inputs by utilizing the dataset created and the back-propagation (BP) neural network algorithm. A method of predicting the structural strength of the tower in real time by rapidly outputting the stresses of all the members of the tower on the basis of the displacements of the monitoring points and the surrogate model was proposed to pave the way for real-time perception of the operation status of transmission lines and safety early warning technologies.
