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2024 Vol. 54, No. 5
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2024, 54(5): 1-8.
doi: 10.3724/j.gyjzG23111319
Abstract:
With the rapid development of economy and urbanization, the scale and number of super-large excavation pit projects have surged. However, the construction of super-large underground space structure is faced with challenges such as complex underground environment and many risk factors, and its safety problems are becoming more and more obvious. Aiming at the complex problems faced in the construction process of ultra-large underground space structure, the paper proposed an intelligent safety monitoring system suitable for the construction of ultra-large underground space structure by introducing the Internet of Things technology and the concept of digital twin, and explored the integration mechanism of Internet of Things and digital twin. BIM technology was applied in the twin to establish the corresponding physical construction model, and multi-source heterogeneous monitoring data was collected in real time through the Internet of Things technology to realize the information interaction between the virtual construction model and the physical construction model. The real-time safety analysis of multi-source heterogeneous data was carried out with the help of the twin system, and the safety status of the structure was obtained and fed back to the application service layer. The effectiveness and practicability of the twin system in the construction of super-large excavation pits were verified by an example project.
With the rapid development of economy and urbanization, the scale and number of super-large excavation pit projects have surged. However, the construction of super-large underground space structure is faced with challenges such as complex underground environment and many risk factors, and its safety problems are becoming more and more obvious. Aiming at the complex problems faced in the construction process of ultra-large underground space structure, the paper proposed an intelligent safety monitoring system suitable for the construction of ultra-large underground space structure by introducing the Internet of Things technology and the concept of digital twin, and explored the integration mechanism of Internet of Things and digital twin. BIM technology was applied in the twin to establish the corresponding physical construction model, and multi-source heterogeneous monitoring data was collected in real time through the Internet of Things technology to realize the information interaction between the virtual construction model and the physical construction model. The real-time safety analysis of multi-source heterogeneous data was carried out with the help of the twin system, and the safety status of the structure was obtained and fed back to the application service layer. The effectiveness and practicability of the twin system in the construction of super-large excavation pits were verified by an example project.
2024, 54(5): 9-15.
doi: 10.3724/j.gyjzG23111318
Abstract:
Since the 21st century, with the rapid development of economy in our country, the utilization of urban land resources tends to be saturated. The construction and development of large underground spaces has become a significant way to improve the land utilization rate. However, the development process of large underground spaces faces difficulties in terms of complex geological conditions, difficult construction, and multidisciplinary cross management. In order to realize the efficient management and construction of large underground spaces, this study established a framework of lean construction methodology for large underground spaces based on the lean construction concept by integrating BIM and ontology technology, which consists of data layer, knowledge layer, ontology layer and application layer. By effectively integrating various types of information and utilizing the query and semantic reasoning capability of ontology, the framework could provide a decision support platform based on knowledge base and rule system for the construction team and promote the sharing of knowledge for lean construction of large underground spaces. The method was also applied in the case of a large-scale underground space project with three major building shared supporting facilities, which verified the feasibility and effectiveness of the framework and is of great theoretical and practical significance for the efficient development and utilization of large underground spaces.
Since the 21st century, with the rapid development of economy in our country, the utilization of urban land resources tends to be saturated. The construction and development of large underground spaces has become a significant way to improve the land utilization rate. However, the development process of large underground spaces faces difficulties in terms of complex geological conditions, difficult construction, and multidisciplinary cross management. In order to realize the efficient management and construction of large underground spaces, this study established a framework of lean construction methodology for large underground spaces based on the lean construction concept by integrating BIM and ontology technology, which consists of data layer, knowledge layer, ontology layer and application layer. By effectively integrating various types of information and utilizing the query and semantic reasoning capability of ontology, the framework could provide a decision support platform based on knowledge base and rule system for the construction team and promote the sharing of knowledge for lean construction of large underground spaces. The method was also applied in the case of a large-scale underground space project with three major building shared supporting facilities, which verified the feasibility and effectiveness of the framework and is of great theoretical and practical significance for the efficient development and utilization of large underground spaces.
2024, 54(5): 16-24.
doi: 10.3724/j.gyjzG23111320
Abstract:
With the continuous improvement of the level of informationization, the drawbacks of the traditional as-built delivery mode are becoming more and more prominent. In order to solve the problems of low efficiency of traditional as-built delivery and poor availability of delivery data in large underground space scenarios, a digital delivery method that integrates multi-source and multi-dimensional data with database as the core was proposed. Firstly, the digital twin framework for large underground spaces was established, and the digital delivery process was proposed based on this framework, and the collection, transmission, storage and management methods of delivery data were also proposed; then, according to the multi-source and multi-dimensional characteristics of the delivery data of large underground space scenarios, the design principles of the delivery platform, the delivery content, the functional framework and the application scenarios were discussed in detail; finally, the digital delivery work was carried out by combining the engineering examples, and the results showed that the proposed digital delivery method could be utilized by the database as the core of the delivery data. Finally, the digital delivery work was carried out with engineering examples, and the results showed that the proposed delivery method could significantly improve the delivery efficiency and save the management cost, and at the same time formed data assets with certain economic and information value.
With the continuous improvement of the level of informationization, the drawbacks of the traditional as-built delivery mode are becoming more and more prominent. In order to solve the problems of low efficiency of traditional as-built delivery and poor availability of delivery data in large underground space scenarios, a digital delivery method that integrates multi-source and multi-dimensional data with database as the core was proposed. Firstly, the digital twin framework for large underground spaces was established, and the digital delivery process was proposed based on this framework, and the collection, transmission, storage and management methods of delivery data were also proposed; then, according to the multi-source and multi-dimensional characteristics of the delivery data of large underground space scenarios, the design principles of the delivery platform, the delivery content, the functional framework and the application scenarios were discussed in detail; finally, the digital delivery work was carried out by combining the engineering examples, and the results showed that the proposed digital delivery method could be utilized by the database as the core of the delivery data. Finally, the digital delivery work was carried out with engineering examples, and the results showed that the proposed delivery method could significantly improve the delivery efficiency and save the management cost, and at the same time formed data assets with certain economic and information value.
2024, 54(5): 25-32.
doi: 10.3724/j.gyjzG23111317
Abstract:
The construction of large underground spaces is an important field of transformation and upgrading of the construction industry. In the construction process of large underground spaces, how to obtain the optimal construction scheme and achieve the goal of green environmental protection is an urgent problem to be solved. Aiming at low carbon, the study proposed an intelligent optimization method for large underground space construction. According to the calculation method of carbon emissions, the construction scheme optimization framework was formed, and the key factors affecting the construction energy consumption were obtained. Based on the analysis of key factors, the influence mechanism of various components and construction paths on carbon emissions was clarified. Driven by the improved Dijkstra algorithm, an intelligent optimization method of construction path was formed. On this basis, the BP neural network optimized by genetic algorithm formed the coupling relationship between carbon emission and hoisting scheme. The optimal construction scheme was obtatined accurately under the low-carbon goal. Taking the construction site of the three major building shared facilities project of the city sub-center as an example, the case analysis was carried out to verify the feasibility of the proposed method. By analyzing the construction carbon emissions, the best construction path was formed.
The construction of large underground spaces is an important field of transformation and upgrading of the construction industry. In the construction process of large underground spaces, how to obtain the optimal construction scheme and achieve the goal of green environmental protection is an urgent problem to be solved. Aiming at low carbon, the study proposed an intelligent optimization method for large underground space construction. According to the calculation method of carbon emissions, the construction scheme optimization framework was formed, and the key factors affecting the construction energy consumption were obtained. Based on the analysis of key factors, the influence mechanism of various components and construction paths on carbon emissions was clarified. Driven by the improved Dijkstra algorithm, an intelligent optimization method of construction path was formed. On this basis, the BP neural network optimized by genetic algorithm formed the coupling relationship between carbon emission and hoisting scheme. The optimal construction scheme was obtatined accurately under the low-carbon goal. Taking the construction site of the three major building shared facilities project of the city sub-center as an example, the case analysis was carried out to verify the feasibility of the proposed method. By analyzing the construction carbon emissions, the best construction path was formed.
2024, 54(5): 33-42.
doi: 10.13204/j.gyjzG23010608
Abstract:
The containment is the last barrier to effectively prevent the leakage of radioactive materials after an accident in a nuclear power plant, and is one of the important facilities to ensure the safe and stable operation of a nuclear power plant, so its sealing performance is crucial. Nuclear power plant containment leakage testing is required during both commissioning and operation to test the containment sealing performance. The research progress was summarized from three perspectives: integrity leak rate testing, local leak rate testing, and other aspects involving containment leakage testing. The different methods of integrity leak rate testing and local leak rate testing were compared and the characteristics of the methods were summarized. In addition, a summary of component optimization, leak rate prediction and numerical simulation and software development related to containment sealing testing was presented. The shortcomings of the current containment leakage testing research were also analyzed, and the future directions of the containment leakage testing were discussed, which can provide relevant references for the containment sealing research and its development applications.
The containment is the last barrier to effectively prevent the leakage of radioactive materials after an accident in a nuclear power plant, and is one of the important facilities to ensure the safe and stable operation of a nuclear power plant, so its sealing performance is crucial. Nuclear power plant containment leakage testing is required during both commissioning and operation to test the containment sealing performance. The research progress was summarized from three perspectives: integrity leak rate testing, local leak rate testing, and other aspects involving containment leakage testing. The different methods of integrity leak rate testing and local leak rate testing were compared and the characteristics of the methods were summarized. In addition, a summary of component optimization, leak rate prediction and numerical simulation and software development related to containment sealing testing was presented. The shortcomings of the current containment leakage testing research were also analyzed, and the future directions of the containment leakage testing were discussed, which can provide relevant references for the containment sealing research and its development applications.
2024, 54(5): 43-50.
doi: 10.3724/j.gyjzG22122504
Abstract:
An algorithm, utilizing the Hilbert-Huang Transform (HHT) and the random decrement technique (RDT), was proposed to enhance the precision and automation of identifying the modal parameters of structures under operational conditions. The algorithm involves the use of Fourier transform, Butterworth filter, empirical mode decomposition (EMD), random decrement technique (RDT), and Hilbert transform. Fourier transform and Butterworth filter were applied to obtain the dynamic responses of the target frequency range (DRTFR). EMD was employed to decompose the DRTFR into multiple intrinsic mode functions (IMFs). RDT was utilized to derive the free decay response signal of each IMFs. By subjecting the free decay response signals to Hilbert transform, phase curves and amplitude curves were generated. The slops of the phase curves and the amplitude curves were the frequencies and damping, respectively. The results showed that the proposed algorithm was suitable for processing both stationary linear signals and non-stationary non-linear signals. This algorithm exhibited superior accuracy and robustness compared to the fast Fourier transform (FFT) and HHT. It is recommended to use the intercept threshold of 1.2σ and the free decay duration of 75 seconds for processing the non-stationary non-linear signals.
An algorithm, utilizing the Hilbert-Huang Transform (HHT) and the random decrement technique (RDT), was proposed to enhance the precision and automation of identifying the modal parameters of structures under operational conditions. The algorithm involves the use of Fourier transform, Butterworth filter, empirical mode decomposition (EMD), random decrement technique (RDT), and Hilbert transform. Fourier transform and Butterworth filter were applied to obtain the dynamic responses of the target frequency range (DRTFR). EMD was employed to decompose the DRTFR into multiple intrinsic mode functions (IMFs). RDT was utilized to derive the free decay response signal of each IMFs. By subjecting the free decay response signals to Hilbert transform, phase curves and amplitude curves were generated. The slops of the phase curves and the amplitude curves were the frequencies and damping, respectively. The results showed that the proposed algorithm was suitable for processing both stationary linear signals and non-stationary non-linear signals. This algorithm exhibited superior accuracy and robustness compared to the fast Fourier transform (FFT) and HHT. It is recommended to use the intercept threshold of 1.2σ and the free decay duration of 75 seconds for processing the non-stationary non-linear signals.
2024, 54(5): 51-59.
doi: 10.13204/j.gyjzG22112305
Abstract:
The detection of hollowing and missing of building exterior walls is crucial to ensure the public safety around aging buildings in cities. The traditional artificial in-situ detection methods are time- and labor-consuming with safety risks. In addition, the detection results will also be affected by subjective factors such as professional experience and working status. The method of image acquisition by UAV and detection of building exterior wall defects by artificial intelligence model has become popular. However, the current research on defect detection only focuses on visible images or infrared images of a single modality, and only detect a certain defect without considering the mutual conversion between defects. To address this issue, this research combined the visible and infrared images of the building exterior wall, considered the image information from two modalities, and compared the UNet and Res-UNet models of different depths to identify the building exterior wall defects in the fused images. The experimental results showed that the Res-UNet model with a depth of 4 performed excellent on the hollowing and missing of the building exterior wall.
The detection of hollowing and missing of building exterior walls is crucial to ensure the public safety around aging buildings in cities. The traditional artificial in-situ detection methods are time- and labor-consuming with safety risks. In addition, the detection results will also be affected by subjective factors such as professional experience and working status. The method of image acquisition by UAV and detection of building exterior wall defects by artificial intelligence model has become popular. However, the current research on defect detection only focuses on visible images or infrared images of a single modality, and only detect a certain defect without considering the mutual conversion between defects. To address this issue, this research combined the visible and infrared images of the building exterior wall, considered the image information from two modalities, and compared the UNet and Res-UNet models of different depths to identify the building exterior wall defects in the fused images. The experimental results showed that the Res-UNet model with a depth of 4 performed excellent on the hollowing and missing of the building exterior wall.
2024, 54(5): 60-67.
doi: 10.13204/j.gyjzG22102611
Abstract:
In view of the lack of integrated expression of crack region parameters in traditional digital image processing-based crack monitoring methods, the paper proposed a structural surface crack detection method based on three-dimensional reconstruction. This method not only improves the accuracy of crack edge recognition but also realizes the integration of crack regions and parameter calculation. The location of cracks can be determined by mapping two-dimensional cracks onto three-dimensional models. The main work includes: planning the photographic path, collecting image data, and constructing an image dataset targeting building cracks according to the facade height and structural characteristics of the building; establishing a three-dimensional model of the exterior facade area with cracks using Structure from Motion SfM reconstruction technology, and obtaining object distance information without the need for ranging equipment based on the distance from the camera center to the crack fitting plane; identifying and segmenting structural surface cracks using cascaded neural networks; calculating crack parameters using the pixel resolution obtained from the real-world 3D model. The experimental results demonstrated that the proposed method could accurately identify cracks in building facades while simultaneously calculating crack widths and lengths, ultimately achieving crack integration and localization. The relative error of crack width is less than 1.5%, indicating good practical value.
In view of the lack of integrated expression of crack region parameters in traditional digital image processing-based crack monitoring methods, the paper proposed a structural surface crack detection method based on three-dimensional reconstruction. This method not only improves the accuracy of crack edge recognition but also realizes the integration of crack regions and parameter calculation. The location of cracks can be determined by mapping two-dimensional cracks onto three-dimensional models. The main work includes: planning the photographic path, collecting image data, and constructing an image dataset targeting building cracks according to the facade height and structural characteristics of the building; establishing a three-dimensional model of the exterior facade area with cracks using Structure from Motion SfM reconstruction technology, and obtaining object distance information without the need for ranging equipment based on the distance from the camera center to the crack fitting plane; identifying and segmenting structural surface cracks using cascaded neural networks; calculating crack parameters using the pixel resolution obtained from the real-world 3D model. The experimental results demonstrated that the proposed method could accurately identify cracks in building facades while simultaneously calculating crack widths and lengths, ultimately achieving crack integration and localization. The relative error of crack width is less than 1.5%, indicating good practical value.
2024, 54(5): 68-74.
doi: 10.13204/j.gyjzG22091503
Abstract:
With the rapid development of the construction industry, 3D point cloud scanning technology and automatic registration of BIM model have become a hot research topic. Nowadays, the technological development of construction engineering has become an inevitable trend, and only by relying on modern science and technology can a higher level of construction work be achieved. Based on this, with the rapid development of BIM technology and the 3D display of 3D laser scanning technology, the 3D coordinate data of the target can be obtained at a non-contact speed and accurately, and the 3D digital model of the target building can be established through the processing of software in the industry. Point cloud data has the advantages of high accuracy of geometric information and true restoration of construction site, while BIM has rich geometric construction information. This paper proposed a rough registration method of 3D point cloud using BIM grid model, focusing on the plane as geometric feature, which is used to align 3D point cloud with BIM grid, so as to realize the monitoring of building construction progress, and provide the possibility for the construction industry to achieve intelligence and precision.
With the rapid development of the construction industry, 3D point cloud scanning technology and automatic registration of BIM model have become a hot research topic. Nowadays, the technological development of construction engineering has become an inevitable trend, and only by relying on modern science and technology can a higher level of construction work be achieved. Based on this, with the rapid development of BIM technology and the 3D display of 3D laser scanning technology, the 3D coordinate data of the target can be obtained at a non-contact speed and accurately, and the 3D digital model of the target building can be established through the processing of software in the industry. Point cloud data has the advantages of high accuracy of geometric information and true restoration of construction site, while BIM has rich geometric construction information. This paper proposed a rough registration method of 3D point cloud using BIM grid model, focusing on the plane as geometric feature, which is used to align 3D point cloud with BIM grid, so as to realize the monitoring of building construction progress, and provide the possibility for the construction industry to achieve intelligence and precision.
2024, 54(5): 75-85.
doi: 10.3724/j.gyjzG22083022
Abstract:
Based on unscrambling of historical records and investigation of existing remains, the evolution process of Japanese Duobao Pagodas and the architectural form and style of remains were sorted out. It was found that in the long-term development and practice, Japanese Duobao Pagodas had been integrated into the "national style culture" with Japanese local characteristics,which formed new construction ideas and plastic arts and created a new architectural form of two stories with a bottom square and a top circle and double eaves—a fixed architectural form with "a white bun-shaped kamebara (turtle belly)". From that clue, the architectural design thinking and method of Japanese Duobao Pagodas were further analyzed. The evolutional context of inherent architectural forms of Japanese Duobao Pagodas was traced back from the introduction and integration of Tantric thoughts, the influence of Chinese architectural forms, and the absorption and creation of localization. It was indicated that the evolution of the fixed form of Japanese Duobao Pagodas profoundly reflected that while absorbing Chinese architectural forms and architectural arts, Japanese monks and craftsmen creatively combined them with their own national culture and gradually formed a wood tower system with Japanese local styles.
Based on unscrambling of historical records and investigation of existing remains, the evolution process of Japanese Duobao Pagodas and the architectural form and style of remains were sorted out. It was found that in the long-term development and practice, Japanese Duobao Pagodas had been integrated into the "national style culture" with Japanese local characteristics,which formed new construction ideas and plastic arts and created a new architectural form of two stories with a bottom square and a top circle and double eaves—a fixed architectural form with "a white bun-shaped kamebara (turtle belly)". From that clue, the architectural design thinking and method of Japanese Duobao Pagodas were further analyzed. The evolutional context of inherent architectural forms of Japanese Duobao Pagodas was traced back from the introduction and integration of Tantric thoughts, the influence of Chinese architectural forms, and the absorption and creation of localization. It was indicated that the evolution of the fixed form of Japanese Duobao Pagodas profoundly reflected that while absorbing Chinese architectural forms and architectural arts, Japanese monks and craftsmen creatively combined them with their own national culture and gradually formed a wood tower system with Japanese local styles.
2024, 54(5): 86-94.
doi: 10.3724/j.gyjzG23060709
Abstract:
Under the general trend of stock renewal, the development bottleneck of the old city railway station area is becoming more and more prominent. How to promote the optimization and upgrading of the old city station area and revitalize the vitality of the area is an urgent problem to be solved in the current urban renewal. Taking Lanzhou Railway Station as an example, after defining the reasonable scope and combing the current situation of the area, the micro-renewal and optimization design of the railway station area was carried out through the concept of catalyst linkage. The station square was established as the point element, the road in front of the station and the commercial belt along the street as the line element, and the plot in front of the station as the surface element. The "multi-point aggregation, linear string point, point-line-surface linkage development" was taken as the renewal and optimization policy, and the current area optimization scheme was clarified to promote the renewal, optimization and upgrading of the old city area of Lanzhou Railway Station.
Under the general trend of stock renewal, the development bottleneck of the old city railway station area is becoming more and more prominent. How to promote the optimization and upgrading of the old city station area and revitalize the vitality of the area is an urgent problem to be solved in the current urban renewal. Taking Lanzhou Railway Station as an example, after defining the reasonable scope and combing the current situation of the area, the micro-renewal and optimization design of the railway station area was carried out through the concept of catalyst linkage. The station square was established as the point element, the road in front of the station and the commercial belt along the street as the line element, and the plot in front of the station as the surface element. The "multi-point aggregation, linear string point, point-line-surface linkage development" was taken as the renewal and optimization policy, and the current area optimization scheme was clarified to promote the renewal, optimization and upgrading of the old city area of Lanzhou Railway Station.
2024, 54(5): 95-106.
doi: 10.3724/j.gyjzG23091410
Abstract:
Under the background of national third line construction, Shanghai has built a total of 81 enterprises and institutions in the southern Anhui region since the 1960s, serving as the rear base of Shanghai, known as the small third front construction in southern Anhui. The small third front construction in southern Anhui is an important component of the national third line construction, and its spatial pattern has typical "mountain, scattered, and cave" characteristics, but it is also related to the mountainous water system pattern in southern Anhui; Its individual buildings and construction activities not only reflect the technology transfer from Shanghai to the mainland, but also reflect the independent innovation under the technological background at that time, while also reflecting local local construction characteristics. As the largest project of the small third front construction, the small third front construction in southern Anhui is not only a material witness to China’s industrialization process, but also a material monument to the spirit of independent innovation in a specific historical period. It has historical and commemorative value in areas such as building technology transfer, low machinery construction, and regional development.
Under the background of national third line construction, Shanghai has built a total of 81 enterprises and institutions in the southern Anhui region since the 1960s, serving as the rear base of Shanghai, known as the small third front construction in southern Anhui. The small third front construction in southern Anhui is an important component of the national third line construction, and its spatial pattern has typical "mountain, scattered, and cave" characteristics, but it is also related to the mountainous water system pattern in southern Anhui; Its individual buildings and construction activities not only reflect the technology transfer from Shanghai to the mainland, but also reflect the independent innovation under the technological background at that time, while also reflecting local local construction characteristics. As the largest project of the small third front construction, the small third front construction in southern Anhui is not only a material witness to China’s industrialization process, but also a material monument to the spirit of independent innovation in a specific historical period. It has historical and commemorative value in areas such as building technology transfer, low machinery construction, and regional development.
2024, 54(5): 107-116.
doi: 10.3724/j.gyjzG22071501
Abstract:
The ancestors of the Taihang Mountains perfectly integrated water collection, storage, water use, and drainage into the construction of the village space according to the local conditions, providing core support for the agricultural civilization to cope with the regional environment where droughts and floods coexist, reflecting rich ecological wisdom and humanistic connotation. The construction wisdom among them also has important reference significance for modern urban ecological construction. The paper took traditional villages in the Taihang Mountains as an example, by using the methods of induction and summary and typical example analysis. This paper abstracted five points of adaptive construction wisdom of village drought and flood disasters, include the overall ecological pattern of villages based on the consideration of "seek advantages and avoid disadvantages", the village water falling organization system integrating "water storage and drainage", the multi-functional composite space taking into account the situation of "drought and flood", the drought and flood self-balancing facilities integrating the needs of "production and life" and forming a non-institutional humanistic concept of regulating the "human-water" relation. Finally, the paper proposed enlightenment and reference for contemporary urban and rural construction from three aspects: systematic thinking, integration strategy and the construction theory.
The ancestors of the Taihang Mountains perfectly integrated water collection, storage, water use, and drainage into the construction of the village space according to the local conditions, providing core support for the agricultural civilization to cope with the regional environment where droughts and floods coexist, reflecting rich ecological wisdom and humanistic connotation. The construction wisdom among them also has important reference significance for modern urban ecological construction. The paper took traditional villages in the Taihang Mountains as an example, by using the methods of induction and summary and typical example analysis. This paper abstracted five points of adaptive construction wisdom of village drought and flood disasters, include the overall ecological pattern of villages based on the consideration of "seek advantages and avoid disadvantages", the village water falling organization system integrating "water storage and drainage", the multi-functional composite space taking into account the situation of "drought and flood", the drought and flood self-balancing facilities integrating the needs of "production and life" and forming a non-institutional humanistic concept of regulating the "human-water" relation. Finally, the paper proposed enlightenment and reference for contemporary urban and rural construction from three aspects: systematic thinking, integration strategy and the construction theory.
2024, 54(5): 117-125.
doi: 10.3724/j.gyjzG23072807
Abstract:
The weighting of indicators in the evaluation of historical building value is typically based on the relative importance of each indicator, often overlooking the influence of subjective scoring discrepancies on these weights. However, such differences in subjective scoring reflect the reliability of scoring data and the degree of emphasis placed on high-value indicators. Considering them as factors influencing indicator weighting can lead to more objective and accurate evaluation results. This study introduced the information content weighting method and the mandatory distribution method, building upon traditional weighting methods. On one hand, the information content weighting method assigned weights based on the consistency of expert scores for the same indicator, thus compensating for the oversight of considering discrepancies in expert scores for the same indicator in weighting. On the other hand, the mandatory distribution method optimized the weighting intervals based on the differences in scores between existing indicators, enhancing the rationality of determining interval boundary parameters. After simulating and validating the feasibility and superiority of these two methods, the study further demonstrated their practical significance using the examples of the Xucun Mansion Ancestral Hall in Shexian County and the Wu Family Branch Ancestral Hall, aiming to provide more reliable and effective guidance for the conservation of historical buildings through value assessment.
The weighting of indicators in the evaluation of historical building value is typically based on the relative importance of each indicator, often overlooking the influence of subjective scoring discrepancies on these weights. However, such differences in subjective scoring reflect the reliability of scoring data and the degree of emphasis placed on high-value indicators. Considering them as factors influencing indicator weighting can lead to more objective and accurate evaluation results. This study introduced the information content weighting method and the mandatory distribution method, building upon traditional weighting methods. On one hand, the information content weighting method assigned weights based on the consistency of expert scores for the same indicator, thus compensating for the oversight of considering discrepancies in expert scores for the same indicator in weighting. On the other hand, the mandatory distribution method optimized the weighting intervals based on the differences in scores between existing indicators, enhancing the rationality of determining interval boundary parameters. After simulating and validating the feasibility and superiority of these two methods, the study further demonstrated their practical significance using the examples of the Xucun Mansion Ancestral Hall in Shexian County and the Wu Family Branch Ancestral Hall, aiming to provide more reliable and effective guidance for the conservation of historical buildings through value assessment.
2024, 54(5): 126-134.
doi: 10.3724/j.gyjzG23090102
Abstract:
In the context of urban renewal, how the historical information and spatial culture of industrial heritage in transition are disseminated and perceived by the public needs to be emphasized. Urban imagery research based on big data has become an important trend, but due to the limitations of data and methodology, there is a relative lack of research on micro-scale such as industrial heritage sites. The paper took Shanghai International Fashion Center (SIFC) as the research object, classified 12 578 pictures related to the built environment collected on social media, and batch restored and tagged the photographer’s points based on 3D model combined with manual correction, and then analyzed the characteristics of imagery composition and their seasonal variations, spatial structural features and imagery in terms of public activities, public space, landmarks and natural landscape in the SIFC, and revealed the characteristics of spatial structure and imagery evolution of the SIFC. The study found that: 1) visitors’ perceptions of the renovated park are mainly reflected in the public space and public life, followed by the perception of the industrial heritage; 2) the main spatial structure of the original industrial heritage is basically retained after redevelopment, but some elements, such as the streets, have received insufficient attention; 3) the commercial art elements have weakened people’s perception of the industrial cultural elements, while giving the place vitality again. The paper revealed the bottom-up subjective perception characteristics, which can provide a reference for further understanding the value dissemination law of industrial heritage and the creation of regional characteristics.
In the context of urban renewal, how the historical information and spatial culture of industrial heritage in transition are disseminated and perceived by the public needs to be emphasized. Urban imagery research based on big data has become an important trend, but due to the limitations of data and methodology, there is a relative lack of research on micro-scale such as industrial heritage sites. The paper took Shanghai International Fashion Center (SIFC) as the research object, classified 12 578 pictures related to the built environment collected on social media, and batch restored and tagged the photographer’s points based on 3D model combined with manual correction, and then analyzed the characteristics of imagery composition and their seasonal variations, spatial structural features and imagery in terms of public activities, public space, landmarks and natural landscape in the SIFC, and revealed the characteristics of spatial structure and imagery evolution of the SIFC. The study found that: 1) visitors’ perceptions of the renovated park are mainly reflected in the public space and public life, followed by the perception of the industrial heritage; 2) the main spatial structure of the original industrial heritage is basically retained after redevelopment, but some elements, such as the streets, have received insufficient attention; 3) the commercial art elements have weakened people’s perception of the industrial cultural elements, while giving the place vitality again. The paper revealed the bottom-up subjective perception characteristics, which can provide a reference for further understanding the value dissemination law of industrial heritage and the creation of regional characteristics.
2024, 54(5): 135-140.
doi: 10.3724/j.gyjzG21092507
Abstract:
A comparative analysis was conducted on the direct shear bearing capacity of the joints of prestressed precast concrete segmental beams. By sorting out and summarizing the research on direct shear failure of joints, using 184 direct shear test data of joints in the literature, the accuracy of the existing bearing capacity prediction model was verified, and the shear strengths of different joints were compared. The results showed that the direct shear bearing capacity of multi-keyed joints was lower than that of single-keyed joints, the shear bearing capacity of epoxy single-keyed joints was the highest, the shear bearing capacity of dry multi-keyed joints was the lowest, and the shear bearing capacity epoxy plane joints was between the above two. The calculation formula of AASHTO specification was good for predicting the dry single-keyed joints, but the prediction results of dry multi-keyed joints were not safe. A calculation model for the bearing capacity of joints was proposed through comparisons. Based on the comparison between the direct shear bearing capacity of joints and the bearing capacity of minimum shear section in codes, the analysis results show that for the structure designed according to JTG 3362—2018, when the section height is less than 5 m, there will be no direct shear failure of epoxy keyed joints.
A comparative analysis was conducted on the direct shear bearing capacity of the joints of prestressed precast concrete segmental beams. By sorting out and summarizing the research on direct shear failure of joints, using 184 direct shear test data of joints in the literature, the accuracy of the existing bearing capacity prediction model was verified, and the shear strengths of different joints were compared. The results showed that the direct shear bearing capacity of multi-keyed joints was lower than that of single-keyed joints, the shear bearing capacity of epoxy single-keyed joints was the highest, the shear bearing capacity of dry multi-keyed joints was the lowest, and the shear bearing capacity epoxy plane joints was between the above two. The calculation formula of AASHTO specification was good for predicting the dry single-keyed joints, but the prediction results of dry multi-keyed joints were not safe. A calculation model for the bearing capacity of joints was proposed through comparisons. Based on the comparison between the direct shear bearing capacity of joints and the bearing capacity of minimum shear section in codes, the analysis results show that for the structure designed according to JTG 3362—2018, when the section height is less than 5 m, there will be no direct shear failure of epoxy keyed joints.
2024, 54(5): 141-149.
doi: 10.3724/j.gyjzG23032007
Abstract:
The system of full-frame-supported high-rise building structure with thick plate transfer has been gradually applied in the subway superstructure property development, in order to explore the influence of changes in the eccentricity of the center of mass caused by vertical retraction of upper multi-tower structure on the full-frame-supported structure with thick plate transfer, the paper designed a 1∶35 scale full-frame-supported multi-tower structure with thick plate transfer, the eccentvicity of the center of mass was calculated, the shaking table test was carried out, and seven finite element models were established to analyze the overall eccentricity parameters combined with ETABS. The results showed that the overall eccentricity of the structure would be changed due to the vertical retraction of the full-frame-supported structure with thick plate transfer, and the acceleration response of the structure increased with the increase of the eccentricity of the center of mass of the structure. At the same time, the experimental and numerical results showed that the torsion effect of the full-frame-supported structure with thick transfer increased with the increase of the overall eccentricity E, which effectively verified the experimental results.
The system of full-frame-supported high-rise building structure with thick plate transfer has been gradually applied in the subway superstructure property development, in order to explore the influence of changes in the eccentricity of the center of mass caused by vertical retraction of upper multi-tower structure on the full-frame-supported structure with thick plate transfer, the paper designed a 1∶35 scale full-frame-supported multi-tower structure with thick plate transfer, the eccentvicity of the center of mass was calculated, the shaking table test was carried out, and seven finite element models were established to analyze the overall eccentricity parameters combined with ETABS. The results showed that the overall eccentricity of the structure would be changed due to the vertical retraction of the full-frame-supported structure with thick plate transfer, and the acceleration response of the structure increased with the increase of the eccentricity of the center of mass of the structure. At the same time, the experimental and numerical results showed that the torsion effect of the full-frame-supported structure with thick transfer increased with the increase of the overall eccentricity E, which effectively verified the experimental results.
2024, 54(5): 150-158.
doi: 10.3724/j.gyjzG23051113
Abstract:
To study the seismic performance of reinforced Engineered Cementitious Composite (ECC) columns under the combination of compression, bending, shear and torsion, quasi-static tests were conducted on 11 reinforced ECC specimens and 1 reinforcement concrete (RC) specimen to investigate the effects of axial compression ratio, torsion bending ratio, shear-span ratio, longitudinal reinforcement ratio, stirrup ratio, fiber content, raw materials and other factors on seismic performance and damage degree. The research results indicated that compared to traditional reinforced concrete, ECC specimens showed better deformation resistance and significant improvements in seismic performance and composite torsional bearing capacity; after reaching the ultimate displacement, the torque of the ECC specimen decreased smoothly, and the damage process was also relatively slow; for ECC specimens, increasing the axial compression ratio, torsion-bending ratio, shear-span ratio, and fiber content appropriately could effectively suppress the damage of components under seismic action; the reinforcement ratio had little effect on the composite torsional bearing capacity of ECC specimens, but it was necessary to configure stirrups.
To study the seismic performance of reinforced Engineered Cementitious Composite (ECC) columns under the combination of compression, bending, shear and torsion, quasi-static tests were conducted on 11 reinforced ECC specimens and 1 reinforcement concrete (RC) specimen to investigate the effects of axial compression ratio, torsion bending ratio, shear-span ratio, longitudinal reinforcement ratio, stirrup ratio, fiber content, raw materials and other factors on seismic performance and damage degree. The research results indicated that compared to traditional reinforced concrete, ECC specimens showed better deformation resistance and significant improvements in seismic performance and composite torsional bearing capacity; after reaching the ultimate displacement, the torque of the ECC specimen decreased smoothly, and the damage process was also relatively slow; for ECC specimens, increasing the axial compression ratio, torsion-bending ratio, shear-span ratio, and fiber content appropriately could effectively suppress the damage of components under seismic action; the reinforcement ratio had little effect on the composite torsional bearing capacity of ECC specimens, but it was necessary to configure stirrups.
2024, 54(5): 159-169.
doi: 10.3724/j.gyjzG23052901
Abstract:
In order to study the seismic performance of a prefabricated RC (reinforced concrete) frame with embedded composite lightweight aggregate partition wall panels, quasi-static load tests were carried out on one trusses of prefabricated concrete empty frame, one trusses of aerated concrete block filled wall-prefabricated concrete frame and one trusses of composite lightweight aggregate wall-prefabricated concrete frame. The cooperative mechanical properties and working mechanism of wall panels and frame under earthquake were studied, and the failure characteristics, load-displacement curve, stiffness degradation, ductility and energy dissipation capacity of the structure were analyzed. The test results showed that the embedded connections of the composite lightweight aggregate partition wall panels were safe and reliable, which could effectively ensure the cooperative work of composite lightweight aggregate wall panels and frame under the action of earthquake. Compared with the aerated concrete filled wall, the ultimate horizontal bearing capacity and initial stiffness of the composite lightweight aggregate wall panels were significantly increased. The mean value of elastic displacement angle θy and the mean value of elastic-plastic limit displacement angle θu of composite lightweight aggregate wall-prefabricated concrete frame could meet the specification requirements. Based on the test results, the restoring force model of the structure was proposed, and the good coincidence of the model was verified, which provided a theoretical basis for the application of the embedded composite lightweight aggregate partition wall panels in prefabricated structures.
In order to study the seismic performance of a prefabricated RC (reinforced concrete) frame with embedded composite lightweight aggregate partition wall panels, quasi-static load tests were carried out on one trusses of prefabricated concrete empty frame, one trusses of aerated concrete block filled wall-prefabricated concrete frame and one trusses of composite lightweight aggregate wall-prefabricated concrete frame. The cooperative mechanical properties and working mechanism of wall panels and frame under earthquake were studied, and the failure characteristics, load-displacement curve, stiffness degradation, ductility and energy dissipation capacity of the structure were analyzed. The test results showed that the embedded connections of the composite lightweight aggregate partition wall panels were safe and reliable, which could effectively ensure the cooperative work of composite lightweight aggregate wall panels and frame under the action of earthquake. Compared with the aerated concrete filled wall, the ultimate horizontal bearing capacity and initial stiffness of the composite lightweight aggregate wall panels were significantly increased. The mean value of elastic displacement angle θy and the mean value of elastic-plastic limit displacement angle θu of composite lightweight aggregate wall-prefabricated concrete frame could meet the specification requirements. Based on the test results, the restoring force model of the structure was proposed, and the good coincidence of the model was verified, which provided a theoretical basis for the application of the embedded composite lightweight aggregate partition wall panels in prefabricated structures.
2024, 54(5): 170-178.
doi: 10.3724/j.gyjzG23111510
Abstract:
In order to study the hysteretic behavior of high strength steel circular hollow section (CHS) T-joints under axial loads, five high-strength steel CHS T-joints under brace axial reciprocating loads with different outer diameter ratios of brace to chord were investigated experimentally and numerically. The hysteretic curves, skeleton curves, energy consumption, ductility and failure modes were analyzed, focusing on the effects of geometric parameters. The results showed that the failure mode of the joints under brace axial reciprocating loads was that the chord wall cracked near the crown area at the intersection line of braces and chords before the cracks expanded along the main pipe cross section, which was different from that of joints made of ordinary strength steel. The hysteretic curve of each joint was full shuttle shape which reflected good seismic performance for the high-strength steel CHS T-joints. The research also showed that the specimens with the same chord section expressed similar shape of the hysteretic curve, and the chord section was one of the main factors affecting the hysteretic behavior of this type of joints. The failure modes, hysteretic curves and skeleton curves of the joints calculated by finite element analysis were in good agreement with the test results, the finite element models established in the paper could well simulate the axial hysteretic behavior of high-strength steel CHS T-joints.
In order to study the hysteretic behavior of high strength steel circular hollow section (CHS) T-joints under axial loads, five high-strength steel CHS T-joints under brace axial reciprocating loads with different outer diameter ratios of brace to chord were investigated experimentally and numerically. The hysteretic curves, skeleton curves, energy consumption, ductility and failure modes were analyzed, focusing on the effects of geometric parameters. The results showed that the failure mode of the joints under brace axial reciprocating loads was that the chord wall cracked near the crown area at the intersection line of braces and chords before the cracks expanded along the main pipe cross section, which was different from that of joints made of ordinary strength steel. The hysteretic curve of each joint was full shuttle shape which reflected good seismic performance for the high-strength steel CHS T-joints. The research also showed that the specimens with the same chord section expressed similar shape of the hysteretic curve, and the chord section was one of the main factors affecting the hysteretic behavior of this type of joints. The failure modes, hysteretic curves and skeleton curves of the joints calculated by finite element analysis were in good agreement with the test results, the finite element models established in the paper could well simulate the axial hysteretic behavior of high-strength steel CHS T-joints.
2024, 54(5): 179-183.
doi: 10.3724/j.gyjzG22042409
Abstract:
According to the capacity spectrum method, the general method for seismic performance-based design of the cast-steel joints is put forward, in which ductility is adopted as the performance index. The method includes three steps: 1) establishing the ductility capacity curve of the joint; 2) establishing the ductility demand curve of the joint; 3) calculating the performance points of the joint according to the capacity spectrum method. Taking the Y-type cast steel joint as an example in this study, the hysteretic curves of the joints with different design parameters were analyzed. Besides, the optimized design parameters for the joint under specific natural period were obtained. The results showed that: 1) Y-type cast steel joint showed a good ductility, as long as it could meet the requirements in Technical Specifiation for Application of Connections of Structural Steel Casting (CECS 235∶2008); 2) the optimal value of d/D was related to the basic natural vibration period of the structure, the d/D value specified in CECS 235∶2008 was not the optimal value for all structures; 3) after establishing ductility demand curves for structure systems with different damping ratios and site types, the numerical seismic performance design that based on the ductility could be carried out for regular cast steel joints by adopting capacity spectrum method.
According to the capacity spectrum method, the general method for seismic performance-based design of the cast-steel joints is put forward, in which ductility is adopted as the performance index. The method includes three steps: 1) establishing the ductility capacity curve of the joint; 2) establishing the ductility demand curve of the joint; 3) calculating the performance points of the joint according to the capacity spectrum method. Taking the Y-type cast steel joint as an example in this study, the hysteretic curves of the joints with different design parameters were analyzed. Besides, the optimized design parameters for the joint under specific natural period were obtained. The results showed that: 1) Y-type cast steel joint showed a good ductility, as long as it could meet the requirements in Technical Specifiation for Application of Connections of Structural Steel Casting (CECS 235∶2008); 2) the optimal value of d/D was related to the basic natural vibration period of the structure, the d/D value specified in CECS 235∶2008 was not the optimal value for all structures; 3) after establishing ductility demand curves for structure systems with different damping ratios and site types, the numerical seismic performance design that based on the ductility could be carried out for regular cast steel joints by adopting capacity spectrum method.
2024, 54(5): 184-191.
doi: 10.3724/j.gyjzG23091113
Abstract:
To study the influence of water pressure on outer surfaces of lining structure of inclined shaft tunnels in coal mines, taking an inclined shaft tunnel project across the rich water aquifer with a weak water yield property as the research object, the analytical formula for reduction factors of water pressure on outer surfaces of linings of tunnels was derived by analyzing water head reduction caused by hydromechanical characteristics and stratigraphic properties in processes of groundwater seepage. Simltaneoushy, based on the project, the rationality of the formula for reduction coefficients of water pressure was evaluated and verified by finite element simulations. On the basis, the influence of three engineering controllable factors including radii of grouting rings, permeability coefficients of grouting rings and radii of tunnels on reduction coefficients of water pressure on outer surfaces of linings of tunnels was studied. The results showed that the increase in the thickness of grouting rings would significantly reduce reduction coefficients of water pressure on outer surfaces of linings, while the increase in the permeability coefficients of grouting rings and radii of tunnels would increase the reduction coefficients of water pressure on outer surfaces of linings significantly.
To study the influence of water pressure on outer surfaces of lining structure of inclined shaft tunnels in coal mines, taking an inclined shaft tunnel project across the rich water aquifer with a weak water yield property as the research object, the analytical formula for reduction factors of water pressure on outer surfaces of linings of tunnels was derived by analyzing water head reduction caused by hydromechanical characteristics and stratigraphic properties in processes of groundwater seepage. Simltaneoushy, based on the project, the rationality of the formula for reduction coefficients of water pressure was evaluated and verified by finite element simulations. On the basis, the influence of three engineering controllable factors including radii of grouting rings, permeability coefficients of grouting rings and radii of tunnels on reduction coefficients of water pressure on outer surfaces of linings of tunnels was studied. The results showed that the increase in the thickness of grouting rings would significantly reduce reduction coefficients of water pressure on outer surfaces of linings, while the increase in the permeability coefficients of grouting rings and radii of tunnels would increase the reduction coefficients of water pressure on outer surfaces of linings significantly.
2024, 54(5): 192-197.
doi: 10.3724/j.gyjzG22092609
Abstract:
To explore a better anti-sliding structure between h-type anti-slide piles and cantilevered double-row anti-slide piles, the finite element software MIDAS/GTS was used and the three-dimensional finite element analysis models for h-type anti-slide piles and cantilevered double-row anti-slide piles were constructed. Then, the displacement, internal force of piles and slope support effect of the two anti-slide pile structures were compared and analyzed. The results showed that: 1) There were significant differences between the two types of anti-slide pile systems in terms of displacement and internal force of piles. Compared with cantilevered double-row anti-slide piles, h-type anti-slide piles were better to coordinate flexural moment and shear force of the front and rear piles, as well as displacement of piles. 2) Compared with cantilevered double-row anti-slide piles, the support effect of h-type anti-slide piles was more significant. The safety factor of slope stability increased by 21.8%, simultaneously, the maximum shear strain decreased by 63.6%. 3) Compared with the cantilevered double-row anti-slide piles, the theoretical calculations on internal force of the front and rear piles in the h-type anti-slide pile systems were more reasonable. It also showed the advantage of h-type anti-slide piles in coordination of the internal force.
To explore a better anti-sliding structure between h-type anti-slide piles and cantilevered double-row anti-slide piles, the finite element software MIDAS/GTS was used and the three-dimensional finite element analysis models for h-type anti-slide piles and cantilevered double-row anti-slide piles were constructed. Then, the displacement, internal force of piles and slope support effect of the two anti-slide pile structures were compared and analyzed. The results showed that: 1) There were significant differences between the two types of anti-slide pile systems in terms of displacement and internal force of piles. Compared with cantilevered double-row anti-slide piles, h-type anti-slide piles were better to coordinate flexural moment and shear force of the front and rear piles, as well as displacement of piles. 2) Compared with cantilevered double-row anti-slide piles, the support effect of h-type anti-slide piles was more significant. The safety factor of slope stability increased by 21.8%, simultaneously, the maximum shear strain decreased by 63.6%. 3) Compared with the cantilevered double-row anti-slide piles, the theoretical calculations on internal force of the front and rear piles in the h-type anti-slide pile systems were more reasonable. It also showed the advantage of h-type anti-slide piles in coordination of the internal force.
2024, 54(5): 198-204.
doi: 10.13204/j.gyjzG22091902
Abstract:
In view of the high requirement for smooth operation of high-speed railway in cold regions, two representative temperature difference environments in Hebei region were selected and the effects of filler types, temperature cycles and temperature difference intervals on thermal shrinkage strain characteristics of improved coarse-grained soil fillers were studied. The results indicated that the fillers improved with cement had larger thermal shrinkage strain and thermal shrinkage coefficients, and the mixing of fly ash reduced the maximum thermal shrinkage strain and average thermal shrinkage coefficients, but the mixing ratio of fly ash could not be too large, the maximum thermal shrinkage strain of the fillers increased first and leveled off after the third cycle. Comparisons of thermal shrinkage coefficients of improved fillers that had undergone temperature cycles in different temperature intervals, it was found that the sensitivity of improved fillers to temperature changes decreased after experiencing multiple temperature cycles. The ratios of strain loss and strain recovery were proposed. Furtherly, it was concluded that mixing a little amount of cement into the improved fillers could improve the strain recovery ratio, but the effect was not obvious in the environment of -20 ℃ to 30 ℃. It was suggested that in the construction of high-speed railway in Hebei province, the improved coarse-grained soil fillers with the cement mixing ratios of 3% to 5% and fly ash mixing ratios of 12% to 20% should be used.
In view of the high requirement for smooth operation of high-speed railway in cold regions, two representative temperature difference environments in Hebei region were selected and the effects of filler types, temperature cycles and temperature difference intervals on thermal shrinkage strain characteristics of improved coarse-grained soil fillers were studied. The results indicated that the fillers improved with cement had larger thermal shrinkage strain and thermal shrinkage coefficients, and the mixing of fly ash reduced the maximum thermal shrinkage strain and average thermal shrinkage coefficients, but the mixing ratio of fly ash could not be too large, the maximum thermal shrinkage strain of the fillers increased first and leveled off after the third cycle. Comparisons of thermal shrinkage coefficients of improved fillers that had undergone temperature cycles in different temperature intervals, it was found that the sensitivity of improved fillers to temperature changes decreased after experiencing multiple temperature cycles. The ratios of strain loss and strain recovery were proposed. Furtherly, it was concluded that mixing a little amount of cement into the improved fillers could improve the strain recovery ratio, but the effect was not obvious in the environment of -20 ℃ to 30 ℃. It was suggested that in the construction of high-speed railway in Hebei province, the improved coarse-grained soil fillers with the cement mixing ratios of 3% to 5% and fly ash mixing ratios of 12% to 20% should be used.
2024, 54(5): 205-211.
doi: 10.3724/j.gyjzG22092708
Abstract:
To improve the interfacal strength between ordinary plastic geogrids and fillers, a new type of three-dimensional reinforcement materials —plastic geogrids with vertical ribs of aluminum angles was constructed by fixing aluminum angles as vertical stiffener ribs on the top of the transverse ribs of plastic geogrids. The pullout resistance characteristics and their parameter features of plastic geogrids with vertical stiffener ribs of aluminum angles in sandy fillers were explored by indoor pullout tests in different combined working cases. The results indicated that:1) the pullout curves had an obvious peak value in the stage of lower normal compressive stress, which were characterized by strain softening within the observed range; 2) with the increase in normal compressive stress, the ultimate pullout resistance of plastic geogrids with vertical stiffener ribs of aluminum angles increased obviously. Under the same normal stress, the ultimate pullout resistance was approximately linearly and positively correlated with the height of the vertical stiffener ribs of aluminum angles. 3)The reinforcement effect coefficient, interface shear strength parameter, friction-like coefficient, and pullout coefficient of plastic geogrids with vertical ribs of aluminum angles increased with the increase in the height of the vertical stiffener ribs of aluminum angles, which indicated that three-dimensional reinforcement materials with vertical stiffener ribs of aluminum angles could effectively improve the pullout rasistance strength of the reinforced soil complex, and had positive significance for improving the stability of soil.
To improve the interfacal strength between ordinary plastic geogrids and fillers, a new type of three-dimensional reinforcement materials —plastic geogrids with vertical ribs of aluminum angles was constructed by fixing aluminum angles as vertical stiffener ribs on the top of the transverse ribs of plastic geogrids. The pullout resistance characteristics and their parameter features of plastic geogrids with vertical stiffener ribs of aluminum angles in sandy fillers were explored by indoor pullout tests in different combined working cases. The results indicated that:1) the pullout curves had an obvious peak value in the stage of lower normal compressive stress, which were characterized by strain softening within the observed range; 2) with the increase in normal compressive stress, the ultimate pullout resistance of plastic geogrids with vertical stiffener ribs of aluminum angles increased obviously. Under the same normal stress, the ultimate pullout resistance was approximately linearly and positively correlated with the height of the vertical stiffener ribs of aluminum angles. 3)The reinforcement effect coefficient, interface shear strength parameter, friction-like coefficient, and pullout coefficient of plastic geogrids with vertical ribs of aluminum angles increased with the increase in the height of the vertical stiffener ribs of aluminum angles, which indicated that three-dimensional reinforcement materials with vertical stiffener ribs of aluminum angles could effectively improve the pullout rasistance strength of the reinforced soil complex, and had positive significance for improving the stability of soil.
2024, 54(5): 212-219.
doi: 10.3724/j.gyjzG22091912
Abstract:
With the continuous development of construction scale and the offshore engineering, the loads on pile foundations have been becoming more and more complicated and the effect of lateral loads on pile foundations have been becoming more and more notable. The calculation method for the horizontal reaction coefficient of foundation of rock-socketed piles, which is suggested by Specifications for Design of Foundation of Highway Bridges and Culverts JTC 3363—2019, is too simple, and the size effect of large-diameter rock-socketed piles is not well considered. According to the mechanical characteristics of rigid rock-socketed piles, considering the effect of vertical skin friction, a calculation method to determine the response of rigid rock-socketed piles under lateral loads was proposed based on the assumption of a constant coefficient of horizontal reaction of foundation. The calculation results were more accurate compared with the results without considering vertical skin friction. Based on field test data, the numerical models of rigid rock-socketed piles were constructed by a finite difference software, and the parameter analysis on various factors influencing the rock-pile interaction including the mechanical and physical parameters of rock and piles was performed. Eventually, a fitting formula for the horizontal reaction coefficient based on the assumption of a constant coefficient of horizontal reaction of foundation was proposed.
With the continuous development of construction scale and the offshore engineering, the loads on pile foundations have been becoming more and more complicated and the effect of lateral loads on pile foundations have been becoming more and more notable. The calculation method for the horizontal reaction coefficient of foundation of rock-socketed piles, which is suggested by Specifications for Design of Foundation of Highway Bridges and Culverts JTC 3363—2019, is too simple, and the size effect of large-diameter rock-socketed piles is not well considered. According to the mechanical characteristics of rigid rock-socketed piles, considering the effect of vertical skin friction, a calculation method to determine the response of rigid rock-socketed piles under lateral loads was proposed based on the assumption of a constant coefficient of horizontal reaction of foundation. The calculation results were more accurate compared with the results without considering vertical skin friction. Based on field test data, the numerical models of rigid rock-socketed piles were constructed by a finite difference software, and the parameter analysis on various factors influencing the rock-pile interaction including the mechanical and physical parameters of rock and piles was performed. Eventually, a fitting formula for the horizontal reaction coefficient based on the assumption of a constant coefficient of horizontal reaction of foundation was proposed.
Research on Tensile Softening Constitutive Relation of Macro Polypropylene Fiber Reinforced Concrete
2024, 54(5): 220-225.
doi: 10.3724/j.gyjzG23091904
Abstract:
In order to reveal strengthening and toughening mechanisms of the macro polypropylene fiber reinforced concrete, the tensile softening constitutive relation of the macro polypropylene fiber reinforced concrete was investigated. Three fiber lengths, i.e. 20 mm, 30 mm and 40 mm, and three mass contents, i.e. 0.13%, 0.17% and 0.21%, were selected. Mechanical and fracture properties of the macro polypropylene fiber reinforced concrete, i.e. tensile strength, initial cracking load, and the maximum load, were studied by the splitting tensile test and the three-point bending fracture test, and the tensile softening constitutive relation was derived by the improved J-integral method. The results showed that the cohesive stress decreased rapidly with the increase of the crack opening displacement. Compared with the ordinary concrete, the stress free opening displacement of the macro polypropylene fiber reinforced concrete significantly increased and the fracture process zone length significantly increased, indicating that the brittleness degree significantly reduced. According to the simplified method recommended by Wittmann, a bilinear softening curve for the macro polypropylene fiber reinforced concrete was proposed, in which the cohesive stress at the turning point σs = 0.135ft, the crack opening displacement at the turning point ws = 0.054Gf/ft, and the stress free opening displacement w0 = 14.417Gf/ft. With the increase of fiber length and mass content, the stress free opening displacement w0 significantly increased, indicating that the brittleness degree significantly decreased.
In order to reveal strengthening and toughening mechanisms of the macro polypropylene fiber reinforced concrete, the tensile softening constitutive relation of the macro polypropylene fiber reinforced concrete was investigated. Three fiber lengths, i.e. 20 mm, 30 mm and 40 mm, and three mass contents, i.e. 0.13%, 0.17% and 0.21%, were selected. Mechanical and fracture properties of the macro polypropylene fiber reinforced concrete, i.e. tensile strength, initial cracking load, and the maximum load, were studied by the splitting tensile test and the three-point bending fracture test, and the tensile softening constitutive relation was derived by the improved J-integral method. The results showed that the cohesive stress decreased rapidly with the increase of the crack opening displacement. Compared with the ordinary concrete, the stress free opening displacement of the macro polypropylene fiber reinforced concrete significantly increased and the fracture process zone length significantly increased, indicating that the brittleness degree significantly reduced. According to the simplified method recommended by Wittmann, a bilinear softening curve for the macro polypropylene fiber reinforced concrete was proposed, in which the cohesive stress at the turning point σs = 0.135ft, the crack opening displacement at the turning point ws = 0.054Gf/ft, and the stress free opening displacement w0 = 14.417Gf/ft. With the increase of fiber length and mass content, the stress free opening displacement w0 significantly increased, indicating that the brittleness degree significantly decreased.
2024, 54(5): 226-237.
doi: 10.3724/j.gyjzG23071115
Abstract:
To study the preloading on the mechanical properties of hybrid fiber self-compacting concrete segments at high-temperatures, high-temperature tests were conducted on five segments to obtain the segment furnace temperature, concrete temperature, deformation, and failure mode. A calculation subroutine was developed based on ABAQUS software to establish a temperature field and mechanical analysis model for hybrid reinforced fiber self-compacting concrete segments. The appropriate constitutive relations during the different stages were selected, and the influence of explict or implicit transient thermal strain and preload on segment displacement and equivalent plastic tensile strain was analyzed. The results showed that as the preload increased, the number of cracks on the side of the segment increased and the length became smaller, the number of cracks on the outer arc surface decreased, the distribution of cracks on the inner arc surface became more uniform, and the addition of fibers was helpful to reduce the average crack spacing and the high temperature damage of concrete at the arch foot of segment. The transient thermal strain had an important influence on the equivalent plastic tensile strain distribution of the segment during the cooling stage. When the explicit transient thermal strain was used, the equivalent plastic tensile strain distribution of the segment was more consistent with the test crack area.
To study the preloading on the mechanical properties of hybrid fiber self-compacting concrete segments at high-temperatures, high-temperature tests were conducted on five segments to obtain the segment furnace temperature, concrete temperature, deformation, and failure mode. A calculation subroutine was developed based on ABAQUS software to establish a temperature field and mechanical analysis model for hybrid reinforced fiber self-compacting concrete segments. The appropriate constitutive relations during the different stages were selected, and the influence of explict or implicit transient thermal strain and preload on segment displacement and equivalent plastic tensile strain was analyzed. The results showed that as the preload increased, the number of cracks on the side of the segment increased and the length became smaller, the number of cracks on the outer arc surface decreased, the distribution of cracks on the inner arc surface became more uniform, and the addition of fibers was helpful to reduce the average crack spacing and the high temperature damage of concrete at the arch foot of segment. The transient thermal strain had an important influence on the equivalent plastic tensile strain distribution of the segment during the cooling stage. When the explicit transient thermal strain was used, the equivalent plastic tensile strain distribution of the segment was more consistent with the test crack area.
