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2023 Vol. 53, No. 12
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2023, 53(12): 1-10.
doi: 10.13204/j.gyjzG23083144
Abstract:
From an industrial pioneer to a beacon of art and fashion in the post-industrial era, the 798 Art District is not only a successful example of industrial heritage repurposing, but also a vivid microcosm of the times opportunities and the society progression. It has been called as "the fermenting multi-prism of group emotions" in Beijing. It greatly helps to understand the objective laws of the industrial heritage transformation and regeneration to study the history of the 798 Art District. The paper showed that the 798 Art District has gone through three stages:its establishment as an industrial base, its transformation into an art district, and its evolution into a center of leisure and consumption. The research showed that it is the transition in relationships among stakeholders that had driven the district's regeneration and transformation. Therefore, the study introduced a stakeholder perspective to analyze its transformation process from the unstable alliance to the broken alliance and then to a new alliance. It analyzed the reconstruction of relation during the two transformation phases of the 798 Art District and the resulting spatial changes, draws the interest network maps of stakeholders, and select appropriate indicators to characterize spatial features, aiming to lay a foundation for exploring the creation of a sustainable people-oriented mechanism for industrial heritage regeneration.
From an industrial pioneer to a beacon of art and fashion in the post-industrial era, the 798 Art District is not only a successful example of industrial heritage repurposing, but also a vivid microcosm of the times opportunities and the society progression. It has been called as "the fermenting multi-prism of group emotions" in Beijing. It greatly helps to understand the objective laws of the industrial heritage transformation and regeneration to study the history of the 798 Art District. The paper showed that the 798 Art District has gone through three stages:its establishment as an industrial base, its transformation into an art district, and its evolution into a center of leisure and consumption. The research showed that it is the transition in relationships among stakeholders that had driven the district's regeneration and transformation. Therefore, the study introduced a stakeholder perspective to analyze its transformation process from the unstable alliance to the broken alliance and then to a new alliance. It analyzed the reconstruction of relation during the two transformation phases of the 798 Art District and the resulting spatial changes, draws the interest network maps of stakeholders, and select appropriate indicators to characterize spatial features, aiming to lay a foundation for exploring the creation of a sustainable people-oriented mechanism for industrial heritage regeneration.
2023, 53(12): 11-18,10.
doi: 10.13204/j.gyjzG23081612
Abstract:
Workers' house is a representative form of residential buildings during the planned economy period of People's Republic of China, and it has also been an indispensable component of the country's rapid industrialization process since 1949 as well as an important material witness to the modernization of residential buildings in China. The development and evolution of workers' house are closely related to modern industrial construction, the development of building technology, and other aspects. It is of great theoretical significance to trace its development history and study its value. The paper attempted to deeply trace the historical development trajectory of workers' house in the early stages of planned economy from two dimensions of building standards and construction materials. Through the systematic analysis of formulation and adjustment of building standards and specifications, the application of building materials, and the innovation of construction mode, and combined with specific historical conditions such as social needs as well as material and technological conditions, the historical context of workers' house in the early stages of planned economy in China was condensed, as well as the architectural characteristics and heritage value, which could provide a theoretical basis and basis for the refinement and deepening of research on industrial heritage in China.
Workers' house is a representative form of residential buildings during the planned economy period of People's Republic of China, and it has also been an indispensable component of the country's rapid industrialization process since 1949 as well as an important material witness to the modernization of residential buildings in China. The development and evolution of workers' house are closely related to modern industrial construction, the development of building technology, and other aspects. It is of great theoretical significance to trace its development history and study its value. The paper attempted to deeply trace the historical development trajectory of workers' house in the early stages of planned economy from two dimensions of building standards and construction materials. Through the systematic analysis of formulation and adjustment of building standards and specifications, the application of building materials, and the innovation of construction mode, and combined with specific historical conditions such as social needs as well as material and technological conditions, the historical context of workers' house in the early stages of planned economy in China was condensed, as well as the architectural characteristics and heritage value, which could provide a theoretical basis and basis for the refinement and deepening of research on industrial heritage in China.
2023, 53(12): 19-28.
doi: 10.13204/j.gyjzG23083017
Abstract:
The heritage of the shipbuilding industry is a microcosm of modern industry, witnessing the transformation of modern Chinese society. In the context of traditional industrial model land concessions, production function transformation, and urban stock development, sorting out the current research content on the regeneration of shipbuilding industry heritage and deducing important future development directions can provide theoretical reference and future guidance for the protection and regeneration, good transformation, and cultural heritage inheritance of shipbuilding industry heritage. Through the review and analysis of research results related to the regeneration of shipbuilding industry heritage, it is found that:firstly, the research hotspots of shipbuilding industry heritage regeneration are landscape design, value evaluation, urban renewal, protection and regeneration, sustainable development, etc., and the disciplinary background presents interdisciplinary characteristics. Secondly, there are different research directions and trends in domestic and overseas development. Foreign research has developed faster than domestic research, with a prominent focus on ecological restoration, environmental governance, green sustainability, and circular design, providing guidance for China's future development. Thirdly, the research on the regeneration of shipbuilding industry heritage in the new era should further explore the direction of environmental quality improvement and sustainable development under the general trend of circular economy, and introduce new trends such as intelligent construction, carbon neutrality, and digital technology for research.
The heritage of the shipbuilding industry is a microcosm of modern industry, witnessing the transformation of modern Chinese society. In the context of traditional industrial model land concessions, production function transformation, and urban stock development, sorting out the current research content on the regeneration of shipbuilding industry heritage and deducing important future development directions can provide theoretical reference and future guidance for the protection and regeneration, good transformation, and cultural heritage inheritance of shipbuilding industry heritage. Through the review and analysis of research results related to the regeneration of shipbuilding industry heritage, it is found that:firstly, the research hotspots of shipbuilding industry heritage regeneration are landscape design, value evaluation, urban renewal, protection and regeneration, sustainable development, etc., and the disciplinary background presents interdisciplinary characteristics. Secondly, there are different research directions and trends in domestic and overseas development. Foreign research has developed faster than domestic research, with a prominent focus on ecological restoration, environmental governance, green sustainability, and circular design, providing guidance for China's future development. Thirdly, the research on the regeneration of shipbuilding industry heritage in the new era should further explore the direction of environmental quality improvement and sustainable development under the general trend of circular economy, and introduce new trends such as intelligent construction, carbon neutrality, and digital technology for research.
2023, 53(12): 29-36.
doi: 10.13204/j.gyjzG23072604
Abstract:
On the basis of preserving the material and non-material heritage, old factory buildings can be transformed to maximize the quality, minimize the cost of maintenance and operation, and benefit from it in a shorter period of time, which can really help the inefficient stock of land to realize a gorgeous transformation, and make more aspiring enterprises willing to invest in urban renewal for a long period of time. Due to the complexity of superior policy, land nature, property right issues and other reasons, successful transformation of old factory buildings not only depends on the design scheme of the transformed space, but also needs to meet more comprehensive requirements for the government's superior pre-planning, the construction side's operation capability, and the design side's full-cycle service, which is a new challenge to the cpacitity of each practitioner. Under the perspective of collaborative renewal, the protection and adaptive reuse of industrial heritage in Hechai·1972 Cultural and Creative Park has realized further effective exploration for the practice patterns of old factory buildings.
On the basis of preserving the material and non-material heritage, old factory buildings can be transformed to maximize the quality, minimize the cost of maintenance and operation, and benefit from it in a shorter period of time, which can really help the inefficient stock of land to realize a gorgeous transformation, and make more aspiring enterprises willing to invest in urban renewal for a long period of time. Due to the complexity of superior policy, land nature, property right issues and other reasons, successful transformation of old factory buildings not only depends on the design scheme of the transformed space, but also needs to meet more comprehensive requirements for the government's superior pre-planning, the construction side's operation capability, and the design side's full-cycle service, which is a new challenge to the cpacitity of each practitioner. Under the perspective of collaborative renewal, the protection and adaptive reuse of industrial heritage in Hechai·1972 Cultural and Creative Park has realized further effective exploration for the practice patterns of old factory buildings.
2023, 53(12): 37-44,181.
doi: 10.13204/j.gyjzG23080811
Abstract:
The renovation of industrial remains should not only realize its own transformation, but also catalyze a local sustainable regeneration. This study established an evaluation framework for catalytic effect based on spatiotemporal characteristics. Taking Yangpu District in Shanghai as an example, the spatiotemporal evolution of the renovated industrial remains and their surrounding areas were analyzed, and four types of catalytic effects were found:circle, aggregated, chain, and point. By summarizing three necessary premises of localized industries, sufficient spatial carriers, and continuous regeneration areas, as well as three supplementary premises of policy coherence, significance of industrial heritage, and high-quality public spaces for inducing the catalytic effect of the renovated industrial remains, the paper out that its internal mechanism lied on the spatiotemporal synergy between renovation of industrial remains and the development of innovative and creative industries, so as to provide a reference for renovation of old industrial towns in China.
2023, 53(12): 45-53.
doi: 10.13204/j.gyjzG23083006
Abstract:
As the process of urban renewal shifts from incremental to stock, the process of urban renewal is increasingly advancing, and the industrial relics in the city undergo diversified transformation. Based on the affordance theory, a theoretical model of affordance for the community-based renewal of industrial relics was constructed from the four dimensions of affordance of physical space, affordance of functional characteristics, affordance of place atmosphere and affordance of place activities; at the same time, it conducted a POI analysis of the surrounding environment of existing industrial relics in Wuhan City, and summarized the functional characteristics and vitality of the radius of influence of industrial relics in different modes of community-based renewal; the actual cases of community-based renewal of industrial relics in Wuhan City were analyzed through case studies and field research; so as to summarize their representations of affordance in terms of physical space, functional characteristics, place atmosphere and social activities, analyze the problems arising from the process of community-based renewal of industrial relics, and put forward the strategies of community-based renewal of industrial relics from four dimensions.
As the process of urban renewal shifts from incremental to stock, the process of urban renewal is increasingly advancing, and the industrial relics in the city undergo diversified transformation. Based on the affordance theory, a theoretical model of affordance for the community-based renewal of industrial relics was constructed from the four dimensions of affordance of physical space, affordance of functional characteristics, affordance of place atmosphere and affordance of place activities; at the same time, it conducted a POI analysis of the surrounding environment of existing industrial relics in Wuhan City, and summarized the functional characteristics and vitality of the radius of influence of industrial relics in different modes of community-based renewal; the actual cases of community-based renewal of industrial relics in Wuhan City were analyzed through case studies and field research; so as to summarize their representations of affordance in terms of physical space, functional characteristics, place atmosphere and social activities, analyze the problems arising from the process of community-based renewal of industrial relics, and put forward the strategies of community-based renewal of industrial relics from four dimensions.
2023, 53(12): 54-61.
doi: 10.13204/j.gyjzG23090709
Abstract:
On the basis of giving a brief summary of the development of Zhujiang Brewery and relying on literature organization and on-site research, the status quo and heritage value of the former site of Zhujiang Brewery were expounded. The countermeasures of the overall adaptive reuse for the plant zone were summarized. Next, taking the turbine workshop and its equipments as research objects, which were the core item in the industrial heritages of Zhujiang Brewery, the adaptive reuse design strategy was proposed in aspects of facade protection, architectural space and technique process display to achieve a win-win situation of context protection and economic benefits.
On the basis of giving a brief summary of the development of Zhujiang Brewery and relying on literature organization and on-site research, the status quo and heritage value of the former site of Zhujiang Brewery were expounded. The countermeasures of the overall adaptive reuse for the plant zone were summarized. Next, taking the turbine workshop and its equipments as research objects, which were the core item in the industrial heritages of Zhujiang Brewery, the adaptive reuse design strategy was proposed in aspects of facade protection, architectural space and technique process display to achieve a win-win situation of context protection and economic benefits.
2023, 53(12): 62-69.
doi: 10.13204/j.gyjzG23031707
Abstract:
Industrial heritage is an important part of industrial civilization and urban memory. The industrial space renewal guided by the recreation transformation of industrial heritage is an important way to inherit and revive the development of the region in industrial decline. Based on network text and picture data, this paper studied and analyzed the three-level experiential perception characteristics of cognitive experience, emotional experience, and overall spatial experience of the industrial heritage renovation project of Yangshuo Old Sugar Factory, drew conclusions from the three aspects of "authenticity", "design sense", and "integrity", and in the four aspects of spatial background, spatial memory, spatial function and spatial experience, it was proposed to renew and utilize the spatial texture, excavate the cultural connotation of inheritance, optimize and reshape the spatial structure, and stimulate and strengthen the spatial vitality, so as to provide a reference for the renewal and utilization of other small and medium-sized industrial heritage recreation.
Industrial heritage is an important part of industrial civilization and urban memory. The industrial space renewal guided by the recreation transformation of industrial heritage is an important way to inherit and revive the development of the region in industrial decline. Based on network text and picture data, this paper studied and analyzed the three-level experiential perception characteristics of cognitive experience, emotional experience, and overall spatial experience of the industrial heritage renovation project of Yangshuo Old Sugar Factory, drew conclusions from the three aspects of "authenticity", "design sense", and "integrity", and in the four aspects of spatial background, spatial memory, spatial function and spatial experience, it was proposed to renew and utilize the spatial texture, excavate the cultural connotation of inheritance, optimize and reshape the spatial structure, and stimulate and strengthen the spatial vitality, so as to provide a reference for the renewal and utilization of other small and medium-sized industrial heritage recreation.
2023, 53(12): 70-76.
doi: 10.13204/j.gyjzG23053008
Abstract:
Water tower is a large number of typical industrial relics in northeast China with outstanding architectural artistic value. Taking the winning works of the Second National Green Building Design Competition in 2022 as an example, the regional climate, site conditions and physical characteristics of the water tower were analyzed, the water tower was implanted with urban public service functions, and low-carbon technologies such as wood structure, double skin and solar chimney were introduced for integrated design. The material selection and technique integration of regeneration design highlighted the cultural value of water towers along the Chinese Eastern Railway, and the paper explored the application of wood structures in the organic renewal of industrial buildings, and provided a reference example for the sustainable regeneration of existing tall industrial towers in cities in cold regions.
Water tower is a large number of typical industrial relics in northeast China with outstanding architectural artistic value. Taking the winning works of the Second National Green Building Design Competition in 2022 as an example, the regional climate, site conditions and physical characteristics of the water tower were analyzed, the water tower was implanted with urban public service functions, and low-carbon technologies such as wood structure, double skin and solar chimney were introduced for integrated design. The material selection and technique integration of regeneration design highlighted the cultural value of water towers along the Chinese Eastern Railway, and the paper explored the application of wood structures in the organic renewal of industrial buildings, and provided a reference example for the sustainable regeneration of existing tall industrial towers in cities in cold regions.
2023, 53(12): 77-84,69.
doi: 10.13204/j.gyjzG23083136
Abstract:
Jiujiang City has been a historic industrial center in Jiangxi, boasting a lengthy and diverse industrial history that has progressed through various developmental stages. Its industrial evolution has become intertwined with China's overall industrial advancement. As the urban industrial structure undergoes adjustments and urban land undergoes renewal, the imperative need for preserving industrial heritage emerges. Through an exploration of the social, economic, and industrial development of Jiujiang in the modern and contemporary periods, the history, process, and local characteristics of modern and contemporary industrial development in Jiujiang were explored. The research indicated that Jiujiang's industrial heritage development predominantly revolves around industries such as shipbuilding, military manufacturing, and textiles. These industries are concentrated along the Yangtze River and major transportation routes, showcasing distinct local characteristics. Based on these local characteristics, some comprehensive strategies were proposed for demarcating the protection scope of Jiujiang industrial relics, clarifying the "local" protection and reuse strategy of Jiujiang industrial relics, and constructing a comprehensive planning framework for regional industrial and cultural tourism, which could provide a reference for the integrated preservation and reuse of Jiujiang City's industrial relics.
Jiujiang City has been a historic industrial center in Jiangxi, boasting a lengthy and diverse industrial history that has progressed through various developmental stages. Its industrial evolution has become intertwined with China's overall industrial advancement. As the urban industrial structure undergoes adjustments and urban land undergoes renewal, the imperative need for preserving industrial heritage emerges. Through an exploration of the social, economic, and industrial development of Jiujiang in the modern and contemporary periods, the history, process, and local characteristics of modern and contemporary industrial development in Jiujiang were explored. The research indicated that Jiujiang's industrial heritage development predominantly revolves around industries such as shipbuilding, military manufacturing, and textiles. These industries are concentrated along the Yangtze River and major transportation routes, showcasing distinct local characteristics. Based on these local characteristics, some comprehensive strategies were proposed for demarcating the protection scope of Jiujiang industrial relics, clarifying the "local" protection and reuse strategy of Jiujiang industrial relics, and constructing a comprehensive planning framework for regional industrial and cultural tourism, which could provide a reference for the integrated preservation and reuse of Jiujiang City's industrial relics.
2023, 53(12): 85-91,174.
doi: 10.13204/j.gyjzG23031704
Abstract:
In the context of stock development, industrial heritage has become an important historical and cultural resource for urban development, and the value evaluation and identification of industrial heritage is a fundamental part of industrial heritage protection and utilization. This study constructed the value evaluation system of industrial heritage from five aspects:historical value, social and cultural value, technical value, aesthetic value and economic value, and took Guangzhou as an example to quantitatively evaluate the value of potential industrial heritage through a combination of data analysis and field research, so as to provide a reference for the identification of industrial heritage.
In the context of stock development, industrial heritage has become an important historical and cultural resource for urban development, and the value evaluation and identification of industrial heritage is a fundamental part of industrial heritage protection and utilization. This study constructed the value evaluation system of industrial heritage from five aspects:historical value, social and cultural value, technical value, aesthetic value and economic value, and took Guangzhou as an example to quantitatively evaluate the value of potential industrial heritage through a combination of data analysis and field research, so as to provide a reference for the identification of industrial heritage.
2023, 53(12): 92-98.
doi: 10.13204/j.gyjzG23030118
Abstract:
The paper presented the Y(area ratio of sharing space)-L(the number of people served per unit area of sharing space) evaluation system, interpreting the innovation model of sharing living based on data. Through 10 cases, different values related to sharing space were extracted and analyzed, and thus, the design laws of sharing design were explored. Firstly, the paper summed up the organization types of sharing space. Secondly, the efficiency of space resources was analyzed from the two aspects of supply and use, and some suggestions were proposed on the design indexes of residential buildings based on the green building evaluation. Finally, the scoring way was proposed when the sharing indexes were was used in the green evaluation. The Y-L system can be used to assist the evaluation of green building performance, guiding the architectural innovation and green design.
The paper presented the Y(area ratio of sharing space)-L(the number of people served per unit area of sharing space) evaluation system, interpreting the innovation model of sharing living based on data. Through 10 cases, different values related to sharing space were extracted and analyzed, and thus, the design laws of sharing design were explored. Firstly, the paper summed up the organization types of sharing space. Secondly, the efficiency of space resources was analyzed from the two aspects of supply and use, and some suggestions were proposed on the design indexes of residential buildings based on the green building evaluation. Finally, the scoring way was proposed when the sharing indexes were was used in the green evaluation. The Y-L system can be used to assist the evaluation of green building performance, guiding the architectural innovation and green design.
2023, 53(12): 99-104,126.
doi: 10.13204/j.gyjzG23083113
Abstract:
China's early railway construction was carried out under the background of suffering from the invasion and oppression of the Western powers. Meanwhile, the participation of the powers also objectively brought modern techniques and concepts to promote the development of modern railways in China. Among them, the Qingdao-Jinan Railway and the northern section of the Tientsin-Pukow Railway were constructed by German funds and techniques, and still retain a lot of unique architectural heritage with significant value. The paper analyzed and studied the important architectural heritage along the two railway sections by means of literature review and field investigation, and extracted and summarized the value connotation of its historical value, scientific value and cultural value, and explained the important significance of its research and protection.
China's early railway construction was carried out under the background of suffering from the invasion and oppression of the Western powers. Meanwhile, the participation of the powers also objectively brought modern techniques and concepts to promote the development of modern railways in China. Among them, the Qingdao-Jinan Railway and the northern section of the Tientsin-Pukow Railway were constructed by German funds and techniques, and still retain a lot of unique architectural heritage with significant value. The paper analyzed and studied the important architectural heritage along the two railway sections by means of literature review and field investigation, and extracted and summarized the value connotation of its historical value, scientific value and cultural value, and explained the important significance of its research and protection.
2023, 53(12): 105-112,134.
doi: 10.13204/j.gyjzG23061302
Abstract:
In order to solve the shortage of traditional monocular vision displacement measurement methods that cannot obtain 3D motion information of structures, binocular stereo vision was applied to the 3D displacement monitoring of structures. Using Python language, the algorithm was compiled on Pycharm platform, and Shi-Tomasi corner point detection algorithm was combined with scale invariant feature transformation algorithm to achieve stereo matching of feature points of left and right images. Through image pre-processing, the coordinates of the matched target feature points were extracted, and then the three-dimensional displacement monitoring of the structure was realized, and the method was applied to the shaking table test of a five-story frame model to obtain the three-dimensional displacement time history of the structure under the action of ground shaking. The test results showed that the displacement time history curve measured by the method matched well with the data of the pull-wire displacement meter, and the maximum peak displacement in Z-direction differed by 1.29 mm with the absolute value of error within 8%, and also had a good performance in the frequency domain. Besides, the robustness of the method was verified by changing the baseline distance and the deflection angle of the camera, which showed the feasibility of the method used as the whole process monitoring of the 3D displacement of the structure.
In order to solve the shortage of traditional monocular vision displacement measurement methods that cannot obtain 3D motion information of structures, binocular stereo vision was applied to the 3D displacement monitoring of structures. Using Python language, the algorithm was compiled on Pycharm platform, and Shi-Tomasi corner point detection algorithm was combined with scale invariant feature transformation algorithm to achieve stereo matching of feature points of left and right images. Through image pre-processing, the coordinates of the matched target feature points were extracted, and then the three-dimensional displacement monitoring of the structure was realized, and the method was applied to the shaking table test of a five-story frame model to obtain the three-dimensional displacement time history of the structure under the action of ground shaking. The test results showed that the displacement time history curve measured by the method matched well with the data of the pull-wire displacement meter, and the maximum peak displacement in Z-direction differed by 1.29 mm with the absolute value of error within 8%, and also had a good performance in the frequency domain. Besides, the robustness of the method was verified by changing the baseline distance and the deflection angle of the camera, which showed the feasibility of the method used as the whole process monitoring of the 3D displacement of the structure.
2023, 53(12): 113-119,163.
doi: 10.13204/j.gyjzG23033010
Abstract:
In the design of complex transportation hub structures, due to the laying of pipeline routes, openings are required in the web of reinforced concrete (RC) beams. In order to study the fatigue performance of RC beams with double openings, six RC beams with double openings were designed using load level ratio, load acting hole location, and fatigue times as variable parameters, and fatigue tests were conducted on them under repeated loads. The stress states and failure modes in a RC beam with double openings during fatigue loading were studied, and the effects of various parameters on the fatigue performance of the beam were discussed. A deformation compatibility model was proposed. Based on the model, the damage evolution and failure mechanism of the RC beam with double openings under fatigue loading were revealed. The research showed that under cyclic loading, the fatigue failure modes of RC beams with double openings were diagonal cracks in the upper and lower beams of the openings and cracks in the corners of the openings. The specimen with an upper load limit of 0.7Pu and a load position acting on the middle of the opening underwent fatigue failure. The RC beam with double openings had a fatigue life of at least 410 000 times under a load level of 0.5Pu. After the fatigue test, the residual ultimate bearing capacity, flexural stiffness, and ductility deteriorated with the increase of the load level. When the load was located in the middle of the opening, the residual performance of the specimen after fatigue became worse. Increasing the fatigue cycle to 410 000 times had an impact on the residual ultimate bending moment of about 7%, and the residual bending stiffness and ductility degraded by about 25%. Based on the specifications, a fatigue deformation prediction method for RC beams with double openings was proposed, with an error of less than 7%.
In the design of complex transportation hub structures, due to the laying of pipeline routes, openings are required in the web of reinforced concrete (RC) beams. In order to study the fatigue performance of RC beams with double openings, six RC beams with double openings were designed using load level ratio, load acting hole location, and fatigue times as variable parameters, and fatigue tests were conducted on them under repeated loads. The stress states and failure modes in a RC beam with double openings during fatigue loading were studied, and the effects of various parameters on the fatigue performance of the beam were discussed. A deformation compatibility model was proposed. Based on the model, the damage evolution and failure mechanism of the RC beam with double openings under fatigue loading were revealed. The research showed that under cyclic loading, the fatigue failure modes of RC beams with double openings were diagonal cracks in the upper and lower beams of the openings and cracks in the corners of the openings. The specimen with an upper load limit of 0.7Pu and a load position acting on the middle of the opening underwent fatigue failure. The RC beam with double openings had a fatigue life of at least 410 000 times under a load level of 0.5Pu. After the fatigue test, the residual ultimate bearing capacity, flexural stiffness, and ductility deteriorated with the increase of the load level. When the load was located in the middle of the opening, the residual performance of the specimen after fatigue became worse. Increasing the fatigue cycle to 410 000 times had an impact on the residual ultimate bending moment of about 7%, and the residual bending stiffness and ductility degraded by about 25%. Based on the specifications, a fatigue deformation prediction method for RC beams with double openings was proposed, with an error of less than 7%.
2023, 53(12): 120-126.
doi: 10.13204/j.gyjzG23031903
Abstract:
In order to study the effect of the bond stress from the rebar in the straight anchor section on the local bearing capacity of concrete under anchoring plates, 30 pull-out tests of end-plate reinforced concrete were completed. The dimensions of the anchoing plate used in the test were 50 mm×50 mm×20 mm and 60 mm×60 mm×20 mm, the thickness of concrete protective layer c were 84 mm and 62.5 mm, the strength grade of concrete were C30, C40, and C50. The diameters of the reinforcement d were 25 mm and 32 mm and its embedded length lad was divided into 5 types in the test. The analysis results showed that the local bearing capacity of concrete Fl was related to axial compressive strength of concrete fc, the relative embedded length lad/d and the thickness of the concrete relative protective layer c/d; Fl increased approximately linearly with the increase of lad/d (about 69% from the initial value), increased linearly with fc (about 80% increase from initial value), decreased with an increase in c/d, the decreasing amplitude was up to 34%. Based on data fitting, the formula for calculating the local bearing capacity of concrete under anchoring plates with lad/d and c/d as independent variables was obtained.
In order to study the effect of the bond stress from the rebar in the straight anchor section on the local bearing capacity of concrete under anchoring plates, 30 pull-out tests of end-plate reinforced concrete were completed. The dimensions of the anchoing plate used in the test were 50 mm×50 mm×20 mm and 60 mm×60 mm×20 mm, the thickness of concrete protective layer c were 84 mm and 62.5 mm, the strength grade of concrete were C30, C40, and C50. The diameters of the reinforcement d were 25 mm and 32 mm and its embedded length lad was divided into 5 types in the test. The analysis results showed that the local bearing capacity of concrete Fl was related to axial compressive strength of concrete fc, the relative embedded length lad/d and the thickness of the concrete relative protective layer c/d; Fl increased approximately linearly with the increase of lad/d (about 69% from the initial value), increased linearly with fc (about 80% increase from initial value), decreased with an increase in c/d, the decreasing amplitude was up to 34%. Based on data fitting, the formula for calculating the local bearing capacity of concrete under anchoring plates with lad/d and c/d as independent variables was obtained.
2023, 53(12): 127-134.
doi: 10.13204/j.gyjzG22101921
Abstract:
In order to obtain the influence law of livestock farm environment on the flexural performance of concrete structures, the experimental study of flexural performance of reinforced concrete (RC) beams under the coupling effect of bending load and acid-alkali dry-wet cycles was carried out by simulating the real livestock farm environment with the type of corrosive environment, corrosion cycle time and initial crack width as variables. The test phenomena, crack distribution and load-midspan deflection curves were obtained by the four-point bending tests, and the influence laws of each test variable on the flexural performance were compared and analyzed. The results showed that:all specimens were ductile failure; acid dry-wet cycles could enhance the ultimate bearing capacity of the specimen but weaken its deformation capacity, alkaline dry-wet cycles had little effect on the flexural capacity of the specimen, acid-alkali dry-wet cycles slightly reduced the ultimate load of the specimen, while greatly reducing the deformation capacity; the presence of initial cracks reduced the yield and ultimate load of the specimen, had a certain effect on the deformation capacity of the specimen; the increase in acid-alkali wet-dry cycle time decreased the deformation capacity of the specimen and had a greater effect on the stiffness and deformation capacity of the specimen with 45 mm protective layer thickness.
In order to obtain the influence law of livestock farm environment on the flexural performance of concrete structures, the experimental study of flexural performance of reinforced concrete (RC) beams under the coupling effect of bending load and acid-alkali dry-wet cycles was carried out by simulating the real livestock farm environment with the type of corrosive environment, corrosion cycle time and initial crack width as variables. The test phenomena, crack distribution and load-midspan deflection curves were obtained by the four-point bending tests, and the influence laws of each test variable on the flexural performance were compared and analyzed. The results showed that:all specimens were ductile failure; acid dry-wet cycles could enhance the ultimate bearing capacity of the specimen but weaken its deformation capacity, alkaline dry-wet cycles had little effect on the flexural capacity of the specimen, acid-alkali dry-wet cycles slightly reduced the ultimate load of the specimen, while greatly reducing the deformation capacity; the presence of initial cracks reduced the yield and ultimate load of the specimen, had a certain effect on the deformation capacity of the specimen; the increase in acid-alkali wet-dry cycle time decreased the deformation capacity of the specimen and had a greater effect on the stiffness and deformation capacity of the specimen with 45 mm protective layer thickness.
2023, 53(12): 135-142,210.
doi: 10.13204/j.gyjzG22101829
Abstract:
To solve the problems of difficult installation and positioning, and slow construction speed of prefabricated shear walls, a new type of prefabricated shear wall structure combining alveolar and U-shaped ferrule connections was proposed. The corresponding shear bearing capacity calculation model was preliminarily proposed by analyzing the shear-resisting mechanism of the horizontal joint of the structure. Then, based on the verification of the effectiveness of the finite element modelling method, the shear properties of the new type of prefabricated shear wall were analyzed. The analysis results showed that the new prefabricated shear wall structure exhibited a good mechanical properties, and its shear capacity was slightly higher than that of cast-in-place shear wall. For the shear properties of the new type of prefabricated shear wall with alveolar-type connections, the alveolar and the hidden beam played a major role in shear resistance. With the increase of the strength of the cast-in-place concrete, its shear properties improved significantly. However, the change of the alveolar aspect ratio and the height of the concealed beam had little influence on it. Finally, the theoretically calculated and finite element analysis values of the shear capacity of the new type of prefabricated shear wall with alveolar-type connections were compared. It was found that they matched well, and the maximum relative error was less than 10%.
To solve the problems of difficult installation and positioning, and slow construction speed of prefabricated shear walls, a new type of prefabricated shear wall structure combining alveolar and U-shaped ferrule connections was proposed. The corresponding shear bearing capacity calculation model was preliminarily proposed by analyzing the shear-resisting mechanism of the horizontal joint of the structure. Then, based on the verification of the effectiveness of the finite element modelling method, the shear properties of the new type of prefabricated shear wall were analyzed. The analysis results showed that the new prefabricated shear wall structure exhibited a good mechanical properties, and its shear capacity was slightly higher than that of cast-in-place shear wall. For the shear properties of the new type of prefabricated shear wall with alveolar-type connections, the alveolar and the hidden beam played a major role in shear resistance. With the increase of the strength of the cast-in-place concrete, its shear properties improved significantly. However, the change of the alveolar aspect ratio and the height of the concealed beam had little influence on it. Finally, the theoretically calculated and finite element analysis values of the shear capacity of the new type of prefabricated shear wall with alveolar-type connections were compared. It was found that they matched well, and the maximum relative error was less than 10%.
2023, 53(12): 143-151.
doi: 10.13204/j.gyjzG21102408
Abstract:
The fatigue problem of the grid structure under the load of suspended cranes has attracted much attention in the industrial building field. In order to study the fatigue load characteristics of the grid structure under the action of suspension crane loads, the stress monitoring of the members in grid structure was conducted by using dynamic strain sensors, and the sample load data was obtained. Through data comparison, the web member with severe fatigue damage was selected as the research object, and the fatigue load spectrum of the grid structure was compiled by combining the data processing, rain-flow counting and mathematical statistics. Furthermore, according to the statistical results of the suspension crane loads and frequency, the log-normal probability distribution model of the lifting weights was established by fitting, and a simplified analysis method of fatigue stress frequency spectrum of the grid structure was proposed, the fatigue stress frequency spectrum of the grid structure under different load distribution parameters was obtained. These achievements will provide references for fatigue life study of the grid structure with suspended cranes.
The fatigue problem of the grid structure under the load of suspended cranes has attracted much attention in the industrial building field. In order to study the fatigue load characteristics of the grid structure under the action of suspension crane loads, the stress monitoring of the members in grid structure was conducted by using dynamic strain sensors, and the sample load data was obtained. Through data comparison, the web member with severe fatigue damage was selected as the research object, and the fatigue load spectrum of the grid structure was compiled by combining the data processing, rain-flow counting and mathematical statistics. Furthermore, according to the statistical results of the suspension crane loads and frequency, the log-normal probability distribution model of the lifting weights was established by fitting, and a simplified analysis method of fatigue stress frequency spectrum of the grid structure was proposed, the fatigue stress frequency spectrum of the grid structure under different load distribution parameters was obtained. These achievements will provide references for fatigue life study of the grid structure with suspended cranes.
2023, 53(12): 152-156.
doi: 10.13204/j.gyjzG22112104
Abstract:
Taking the metal roof of Hangzhou-Shaoxing-Taizhou Railway Station as the research object, through the wind resistance test, its failure mode and wind resistance were determined, and the effects of different parameters on the wind resistance of standing seam metal roof were discussed, the results showed that the main failure mode of the standing seam metal roof under wind suction was trip-out failure between the roof panel at seams and bearings. changing the bearing height, purlin spacing and arranging the anti-wind clip could improve the wind resistance of the metal roof with standing seams, and the effect of arranging the anti-wind clip was the most significant. The high-strength wind resistance clamp could change the failure mode of metal roofing system and greatly improve the wind bearing capacity of roof panel compared with the conventional wind clamp. Dynamic cyclic loading had an obvious influence on the ultimate bearing capacity of metal roof with standing seams. It is very necessary to carry out dynamic cyclic wind resistance test in practical engineering.
Taking the metal roof of Hangzhou-Shaoxing-Taizhou Railway Station as the research object, through the wind resistance test, its failure mode and wind resistance were determined, and the effects of different parameters on the wind resistance of standing seam metal roof were discussed, the results showed that the main failure mode of the standing seam metal roof under wind suction was trip-out failure between the roof panel at seams and bearings. changing the bearing height, purlin spacing and arranging the anti-wind clip could improve the wind resistance of the metal roof with standing seams, and the effect of arranging the anti-wind clip was the most significant. The high-strength wind resistance clamp could change the failure mode of metal roofing system and greatly improve the wind bearing capacity of roof panel compared with the conventional wind clamp. Dynamic cyclic loading had an obvious influence on the ultimate bearing capacity of metal roof with standing seams. It is very necessary to carry out dynamic cyclic wind resistance test in practical engineering.
2023, 53(12): 157-163.
doi: 10.13204/j.gyjzG22062711
Abstract:
In order to study the overall mechanical properties and failure forms of the prefabricated CFST column-RC beam frame with embedded steel, based on the actual engineering, a single-story two-span prefabricated frame structure was designed and fabricated for static load tests and numerical simulations, the test results showed that the structure exhibitsed typical three-stage failure characteristics, and the failure section appeared on the beams on both sides of the central column, which was a certain distance from the core area of the frame joint; it had a high safety reserve; the joints had good force transmission performance, each part of the components could be deformed in coordination, and the prefabricated frame had good integrity. After verifying the accuracy and reliability of the finite element model, the finite element method was used to carry out parametric expansion analysis, and the effects of beam concrete strength, beam width, longitudinal rebar strength, longitudinal rebar reinforcement ratio and steel-concrete joint section length on bearing capacity of the structure were studied respectively. The calculation results showed that:within the range of this parameter, increasing the beam concrete strength, beam width, longitudinal rebar strength, reinforcement ratio and length of the joint section could improve the bearing capacity of the structure; the improvement of the bearing capacity was obvious, but the increase became smaller when the value was larger; the embedded section steel could control the occurrence of critical cracks.
In order to study the overall mechanical properties and failure forms of the prefabricated CFST column-RC beam frame with embedded steel, based on the actual engineering, a single-story two-span prefabricated frame structure was designed and fabricated for static load tests and numerical simulations, the test results showed that the structure exhibitsed typical three-stage failure characteristics, and the failure section appeared on the beams on both sides of the central column, which was a certain distance from the core area of the frame joint; it had a high safety reserve; the joints had good force transmission performance, each part of the components could be deformed in coordination, and the prefabricated frame had good integrity. After verifying the accuracy and reliability of the finite element model, the finite element method was used to carry out parametric expansion analysis, and the effects of beam concrete strength, beam width, longitudinal rebar strength, longitudinal rebar reinforcement ratio and steel-concrete joint section length on bearing capacity of the structure were studied respectively. The calculation results showed that:within the range of this parameter, increasing the beam concrete strength, beam width, longitudinal rebar strength, reinforcement ratio and length of the joint section could improve the bearing capacity of the structure; the improvement of the bearing capacity was obvious, but the increase became smaller when the value was larger; the embedded section steel could control the occurrence of critical cracks.
2023, 53(12): 164-174.
doi: 10.13204/j.gyjzG23070905
Abstract:
In order to study the shear performance of grouped large headed stud connectors in prefabricated steel-thin UHPC composite girder, 19 push-out specimens were established by finite element software ABAQUS to study the influence of casting method, stud spacing, key group spacing, and key group number on the shear bearing capacity, shear stiffness, and load-slip curve of the specimens. The results showed that the failure mode of specimens was mainly the shear failure at the root of studs and the local crushing of concrete slabs. The shear bearing capacity of prefabricated specimens was reduced by 10% compared with the cast-in-place specimens. The shear bearing capacity of the specimens decreased significantly when the spacing of studs was less than 2.5 times the diameter of studs. The shear bearing capacity and shear stiffness of individual stud in the key group were reduced by the increase of the spacing and number of key groups. The theoretical model for predicting the load-slip relation of the prefabricated steel-thin UHPC grouped large headed stud connectors was proposed. Moreover, the results of the shear capacity from ABAQUS were compared with the calculated results from the code, and a design method for prefabricated steel-thin UHPC composite girder bridge grouped large headed stud connectors was obtained.
In order to study the shear performance of grouped large headed stud connectors in prefabricated steel-thin UHPC composite girder, 19 push-out specimens were established by finite element software ABAQUS to study the influence of casting method, stud spacing, key group spacing, and key group number on the shear bearing capacity, shear stiffness, and load-slip curve of the specimens. The results showed that the failure mode of specimens was mainly the shear failure at the root of studs and the local crushing of concrete slabs. The shear bearing capacity of prefabricated specimens was reduced by 10% compared with the cast-in-place specimens. The shear bearing capacity of the specimens decreased significantly when the spacing of studs was less than 2.5 times the diameter of studs. The shear bearing capacity and shear stiffness of individual stud in the key group were reduced by the increase of the spacing and number of key groups. The theoretical model for predicting the load-slip relation of the prefabricated steel-thin UHPC grouped large headed stud connectors was proposed. Moreover, the results of the shear capacity from ABAQUS were compared with the calculated results from the code, and a design method for prefabricated steel-thin UHPC composite girder bridge grouped large headed stud connectors was obtained.
2023, 53(12): 175-181.
doi: 10.13204/j.gyjzG22102513
Abstract:
The construction mode of substations is changing to modular design and assembly construction. As an important facility for distributing electrical energy, substations in settlement-sensitive areas generally adopt cast-in-place concrete overhead structures, and their indoor electrical equipment is installed on the cast-in-place concrete overhead structure. The cast-in-place concrete overhead structure can no longer meet the requirements of "standardized design, factory processing and assembly construction" of substations. The paper proposed a new composite overhead structure system that could be used as a foundation for indoor electrical equipment in substation distribution rooms. The structure system consists of modular longitudinal beams, cross beams, columns, panels, and other components, except for the cross beams which are made of steel, other components are made of molded and pultruded composite materials, which have the advantages of the short construction period, convenient hole opening and easy renewal and transformation. The overall scheme and design of the new structural system were systematically introduced in the paper, and the feasibility of the project under actual loading conditions was initially demonstrated.
The construction mode of substations is changing to modular design and assembly construction. As an important facility for distributing electrical energy, substations in settlement-sensitive areas generally adopt cast-in-place concrete overhead structures, and their indoor electrical equipment is installed on the cast-in-place concrete overhead structure. The cast-in-place concrete overhead structure can no longer meet the requirements of "standardized design, factory processing and assembly construction" of substations. The paper proposed a new composite overhead structure system that could be used as a foundation for indoor electrical equipment in substation distribution rooms. The structure system consists of modular longitudinal beams, cross beams, columns, panels, and other components, except for the cross beams which are made of steel, other components are made of molded and pultruded composite materials, which have the advantages of the short construction period, convenient hole opening and easy renewal and transformation. The overall scheme and design of the new structural system were systematically introduced in the paper, and the feasibility of the project under actual loading conditions was initially demonstrated.
2023, 53(12): 182-189,197.
doi: 10.13204/j.gyjzG22080108
Abstract:
The soil of subgrade slopes in areas with alternating cold and dry seasons throughout the year, where evaporation is much greater than precipitation, is in a unsaturated state with high suction most of the time. To study the influence of the silt content on soil-water characteristics and strength of unsaturated soil with high suction, the vapor equilibrium method of saturated salt solution was used to apply high suction to soil with different contents of silt, triaxial tests and splitting tensile tests were conducted on unsaturated soil. The test results indicated that:the silt content had a significant effect on the water intake value of unsaturated soil, there was a negative correlation between the two. The water-held capacity of the soil decreased with the increase of the silt content. Both the silt content and suction had a deteriorating effect on the tensile strength, and both factors simultaneously led to increase in the crack depth of soil. Suction had an inhibitory effect on the deformation of soil, the larger the suction was, the larger the cohesion provided by the suction was. The increase in the silt content had a significant effect on the degeneration of soil elastic moduli. The brittleness characteristics of unsaturated soil with high suction influenced by the silt content were evaluated by defining the brittleness index from a perspective of moduli. It was found that the brittleness of unsaturated soil with high suction was altered by the silt content mainly through the influence of the post-peak secant modulus.
The soil of subgrade slopes in areas with alternating cold and dry seasons throughout the year, where evaporation is much greater than precipitation, is in a unsaturated state with high suction most of the time. To study the influence of the silt content on soil-water characteristics and strength of unsaturated soil with high suction, the vapor equilibrium method of saturated salt solution was used to apply high suction to soil with different contents of silt, triaxial tests and splitting tensile tests were conducted on unsaturated soil. The test results indicated that:the silt content had a significant effect on the water intake value of unsaturated soil, there was a negative correlation between the two. The water-held capacity of the soil decreased with the increase of the silt content. Both the silt content and suction had a deteriorating effect on the tensile strength, and both factors simultaneously led to increase in the crack depth of soil. Suction had an inhibitory effect on the deformation of soil, the larger the suction was, the larger the cohesion provided by the suction was. The increase in the silt content had a significant effect on the degeneration of soil elastic moduli. The brittleness characteristics of unsaturated soil with high suction influenced by the silt content were evaluated by defining the brittleness index from a perspective of moduli. It was found that the brittleness of unsaturated soil with high suction was altered by the silt content mainly through the influence of the post-peak secant modulus.
2023, 53(12): 190-197.
doi: 10.13204/j.gyjzG22072006
Abstract:
To study the influence of sand on the strength and dry-wet cycle characteristics of cementedly coastal soft clay in South China, a series of cementedly coastal soft clay samples in South China with different contents and sizes of sand were prepared, and unconfined compression strength tests, dry-wet cycle tests, scanning electron microscopy tests and X-Ray diffraction tests were conducted in seawater and fresh water. The test results indicated that the unconfined compression strength of sand-mixed clay-cemented samples cured for 7, 14, and 28 days increased with the increase of the sand content, and the strength cured for 28 days increased with the decrease of the size of sand particles; the maximum loss ratio of mass for sand-mixed clay-cemented samples was up to 61%. The properties of strength deterioration subjected to dry-wet cycles improved with the increase of the sand content and the decrease of the size of sand particles. Moreover, the resistant capability for dry-wet cycling of samples in the fresh water was obviously better than that in the seawater. The results by SEM and XRD tests showed that the reinforced mechanisms of sand-mixed cemented soft clay in South China mainly reflected the following:1)the modulus replacement effect (replacement of low modulus soft clay with the high modulus sand);2)the interfacial effect between sand and clay-cemented matrixes;and 3) the blocking and isolating effect for crack.
To study the influence of sand on the strength and dry-wet cycle characteristics of cementedly coastal soft clay in South China, a series of cementedly coastal soft clay samples in South China with different contents and sizes of sand were prepared, and unconfined compression strength tests, dry-wet cycle tests, scanning electron microscopy tests and X-Ray diffraction tests were conducted in seawater and fresh water. The test results indicated that the unconfined compression strength of sand-mixed clay-cemented samples cured for 7, 14, and 28 days increased with the increase of the sand content, and the strength cured for 28 days increased with the decrease of the size of sand particles; the maximum loss ratio of mass for sand-mixed clay-cemented samples was up to 61%. The properties of strength deterioration subjected to dry-wet cycles improved with the increase of the sand content and the decrease of the size of sand particles. Moreover, the resistant capability for dry-wet cycling of samples in the fresh water was obviously better than that in the seawater. The results by SEM and XRD tests showed that the reinforced mechanisms of sand-mixed cemented soft clay in South China mainly reflected the following:1)the modulus replacement effect (replacement of low modulus soft clay with the high modulus sand);2)the interfacial effect between sand and clay-cemented matrixes;and 3) the blocking and isolating effect for crack.
2023, 53(12): 198-203,61.
doi: 10.13204/j.gyjzG22072408
Abstract:
The splitting grouting in sand is a dynamic coupling process between slurry and soil. The slurry diffusion has the characteristics of invisibility, complexity and randomness. The research on the splitting grouting mechanism still needs to be strengthened at present. Through confined compression tests, the macro and micro structure characteristics and stress transfer modes of sand were explored. It was found that the particle fragmentation and clay particle content were the main factors inflerencing the compaction effect of sand, the particle fragmentation was positively correlated with the compaction effect, and the clay particle content was negatively correlated with the compaction effect. When the content of clay particles exceed the critical value, the macro and micro structure of sand would change qualitatively, and the nonlinear compaction effect was conspicuously enhanced. The nonlinear compaction process of sand was described based on a quadratic function model, which was characterized by the initial compression modulus Et of sand and the ultimate strain εu under the final load, and the model was of a clear phyical concept and easliy measured parameters. The compaction effect of sand had a significant impact on slurry diffusion distance, splitting width and slurry pressure distribution. The splitting grouting analysis method considering the self-compaction characteristics of sand could further deepen the understanding of the mechanism for splitting grouting in sand.
The splitting grouting in sand is a dynamic coupling process between slurry and soil. The slurry diffusion has the characteristics of invisibility, complexity and randomness. The research on the splitting grouting mechanism still needs to be strengthened at present. Through confined compression tests, the macro and micro structure characteristics and stress transfer modes of sand were explored. It was found that the particle fragmentation and clay particle content were the main factors inflerencing the compaction effect of sand, the particle fragmentation was positively correlated with the compaction effect, and the clay particle content was negatively correlated with the compaction effect. When the content of clay particles exceed the critical value, the macro and micro structure of sand would change qualitatively, and the nonlinear compaction effect was conspicuously enhanced. The nonlinear compaction process of sand was described based on a quadratic function model, which was characterized by the initial compression modulus Et of sand and the ultimate strain εu under the final load, and the model was of a clear phyical concept and easliy measured parameters. The compaction effect of sand had a significant impact on slurry diffusion distance, splitting width and slurry pressure distribution. The splitting grouting analysis method considering the self-compaction characteristics of sand could further deepen the understanding of the mechanism for splitting grouting in sand.
2023, 53(12): 204-210.
doi: 10.13204/j.gyjzG22082002
Abstract:
Helical piles are widely used in foundations of towers, wind turbine generators and other structures under cyclic loads because of their larger uplift bearing capacities. In recent years, with the increase of extreme strong wind disasters, helical piles have been widely used as anchorage facilities for anti galloping cables of transimission wires in transmission lines. However, there are few studies on the bearing characteristics of helical piles under cyclic loading, and there is no introduction on the bearing capacity calculation method in the relevant regulations and codes. Thus, the monotonic and cyclic in-situ loading tests of helical piles in silt were conducted, the cyclic uplift mechanical characteristics of helical piles were explorated. The results showed that the cumulative displacement of the helical pile was no more than 25 mm when the soil deformation was stable under cyclic action of 50% of static ultimate bearing capacities. The cumulative displacement of helical piles with double helix plates under cyclic uplift loads was smallest, which was about half the cumulative displacement of other helical piles with a single helix plate. When the bearing capacity of helical piles was insufficient, the foundation deformation increased sharply, and a radial crack centered on helical piles appeared on the ground. In the whole test process, the load-displacement skeleton curves of helical piles under cyclic loads were always lower than that of helical piles under static loads. After the cycles, both the load-displacement curves basically coincided under static loads. The uplift bearing capacity of helical piles was mainly composed of side resistance of anchor rods and end resistance of helix plates. Under cyclic uplift loads, the cumulative shrinkage of soil in shear zones of anchor bolt interfaces led to reduction of normal stress, and the uplift bearing capacity of helical piles was provided by helix plates mainly.
Helical piles are widely used in foundations of towers, wind turbine generators and other structures under cyclic loads because of their larger uplift bearing capacities. In recent years, with the increase of extreme strong wind disasters, helical piles have been widely used as anchorage facilities for anti galloping cables of transimission wires in transmission lines. However, there are few studies on the bearing characteristics of helical piles under cyclic loading, and there is no introduction on the bearing capacity calculation method in the relevant regulations and codes. Thus, the monotonic and cyclic in-situ loading tests of helical piles in silt were conducted, the cyclic uplift mechanical characteristics of helical piles were explorated. The results showed that the cumulative displacement of the helical pile was no more than 25 mm when the soil deformation was stable under cyclic action of 50% of static ultimate bearing capacities. The cumulative displacement of helical piles with double helix plates under cyclic uplift loads was smallest, which was about half the cumulative displacement of other helical piles with a single helix plate. When the bearing capacity of helical piles was insufficient, the foundation deformation increased sharply, and a radial crack centered on helical piles appeared on the ground. In the whole test process, the load-displacement skeleton curves of helical piles under cyclic loads were always lower than that of helical piles under static loads. After the cycles, both the load-displacement curves basically coincided under static loads. The uplift bearing capacity of helical piles was mainly composed of side resistance of anchor rods and end resistance of helix plates. Under cyclic uplift loads, the cumulative shrinkage of soil in shear zones of anchor bolt interfaces led to reduction of normal stress, and the uplift bearing capacity of helical piles was provided by helix plates mainly.
2023, 53(12): 211-215.
doi: 10.13204/j.gyjzG22082308
Abstract:
Shenzhen-Zhongshan Link was a super infrastructure project in China, in which the deep cement-mixed piles (DCM piles) were first widely used to improved the foundation of the immersed tunnel. Due to a lack of knowledge about settlement laws of composite foundation composed of the gravel cushion, the block-stone-vibrated cushion and DCM plies, to study the effect of cushion on settlement of composite foundation of DCM plies, based on the static load test on site, the influence of thickness, moduli of the gravel cushion and the block-stone-vibrated thickness on the settlement of pile tops and the total settlement of composite foundation were analyzed by numerical simulations. The results indicated that the flexible cushion under the rigid foundation could make the foundation flexible from rigid, and the cushion could adjust the loads shared by piles and soil, so that loads shared by piles became smaller and loads borne by soil were larger, which leaded to the settlement of pile tops decreased and the total settlement of composite foundation increased. With the decrease of cushion stiffness (increasing thicknesses or decreasing moduli), the adjusting effect of loads shared by piles and soil would not maintain continuous growth. With the increase of total settlement, the bearing capacity of composite foundation almost remained stable. To improve the bearing capacity of composite foundation and control settlement, combined with the actual project, it was suggested that the thickness of the gravel cushion should range from 0.4 to 0.8 m, the modulus should range from 10 to 20 MPa, and the block-stone-vibrated thickness should range from 0.7 to 1.1 m.
Shenzhen-Zhongshan Link was a super infrastructure project in China, in which the deep cement-mixed piles (DCM piles) were first widely used to improved the foundation of the immersed tunnel. Due to a lack of knowledge about settlement laws of composite foundation composed of the gravel cushion, the block-stone-vibrated cushion and DCM plies, to study the effect of cushion on settlement of composite foundation of DCM plies, based on the static load test on site, the influence of thickness, moduli of the gravel cushion and the block-stone-vibrated thickness on the settlement of pile tops and the total settlement of composite foundation were analyzed by numerical simulations. The results indicated that the flexible cushion under the rigid foundation could make the foundation flexible from rigid, and the cushion could adjust the loads shared by piles and soil, so that loads shared by piles became smaller and loads borne by soil were larger, which leaded to the settlement of pile tops decreased and the total settlement of composite foundation increased. With the decrease of cushion stiffness (increasing thicknesses or decreasing moduli), the adjusting effect of loads shared by piles and soil would not maintain continuous growth. With the increase of total settlement, the bearing capacity of composite foundation almost remained stable. To improve the bearing capacity of composite foundation and control settlement, combined with the actual project, it was suggested that the thickness of the gravel cushion should range from 0.4 to 0.8 m, the modulus should range from 10 to 20 MPa, and the block-stone-vibrated thickness should range from 0.7 to 1.1 m.
2023, 53(12): 216-221.
doi: 10.13204/j.gyjzG23092609
Abstract:
In order to enhance the fracture properties of rubber concrete, a three-point bending fracture test was conducted to study the impact of steel fiber-glass fibers on the fracture properties of rubber concrete and its strengthening mechanism. The findings indicated that the addition of rubber powder to concrete might reduce its flexural performance, but it had a positive effect on enhancing the toughness and deformation resistance of concrete. The hybrid fiber composed of steel fibers and glass fibers had a substantial positive impact on the fracture properties of rubber concrete. When the total amount of hybrid fibers was 8% and the ratio of steel fiber to glass fiber was 3:1, the flexural strength of the rubber concrete containing hybrid fibers reached 7.87 MPa, with a fracture energy of 4 681.60 J/m2. Based on the analysis of the double-K fracture model, it was evident that the hybrid fibers greatly enhanced the fracture toughness of rubber concrete, with the most significant improvement observed when the total amount of hybrid fibers exceeded 6%. Additionally, the multi-scale synergy of hybrid fibers enhanced the stress-strain performance of rubber concrete, resulting in improved load resistance and toughness.
In order to enhance the fracture properties of rubber concrete, a three-point bending fracture test was conducted to study the impact of steel fiber-glass fibers on the fracture properties of rubber concrete and its strengthening mechanism. The findings indicated that the addition of rubber powder to concrete might reduce its flexural performance, but it had a positive effect on enhancing the toughness and deformation resistance of concrete. The hybrid fiber composed of steel fibers and glass fibers had a substantial positive impact on the fracture properties of rubber concrete. When the total amount of hybrid fibers was 8% and the ratio of steel fiber to glass fiber was 3:1, the flexural strength of the rubber concrete containing hybrid fibers reached 7.87 MPa, with a fracture energy of 4 681.60 J/m2. Based on the analysis of the double-K fracture model, it was evident that the hybrid fibers greatly enhanced the fracture toughness of rubber concrete, with the most significant improvement observed when the total amount of hybrid fibers exceeded 6%. Additionally, the multi-scale synergy of hybrid fibers enhanced the stress-strain performance of rubber concrete, resulting in improved load resistance and toughness.
