The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield...The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.展开更多
The construction of the new tunnel under the existing railway will break the original stress balance in the engineering area, resulting in the secondary redistribution of surrounding rock stress. The large amount of e...The construction of the new tunnel under the existing railway will break the original stress balance in the engineering area, resulting in the secondary redistribution of surrounding rock stress. The large amount of excavation unloading of the soil below is also easy to induce the uneven settlement deformation of the existing structure above, affecting the safety of driving. Based on the shield tunnel project between Caoqiao Station and Lize Business District Station of Beijing Metro, this paper restores the construction site by constructing the finite element numerical model of the project area, calculates and analyzes the deformation and stress of the existing railway structure before and after the construction of the tunnel, and determines the safety impact of the new structure on the existing railway. The results show that the shield tunnel undercrossing construction will cause the “concave” settlement of the railway subgrade above. Under the condition of grouting reinforcement, the “concave” settlement curve is slower and the distribution range is wider. With the advancement of the construction step, the settlement deformation of the subgrade gradually increases. When the tunnel approaches and passes directly below the subgrade, the settlement deformation curve of the subgrade changes from slow to steep. After the tunnel passes away, the curve changes from steep to slow, and the deformation of the subgrade reaches the maximum after the tunnel is connected. Under the grouting condition, the maximum settlement deformation of the subgrade is 2.08 mm, which is about 45% of the settlement deformation of the subgrade under the non-grouting condition. The ground grouting reinforcement can effectively control the subgrade settlement, and the field monitoring verifies the rationality of the calculation results. After the tunnel passes underneath, the most unfavorable section of the existing railway frame bridge is located at the top plate of the structure, and the maximum crack width is 0.178 mm. After grouting reinforcement, the stress environment of the structure is improved, the crack width generated by the structure is smaller, the reinforcement area required for calculation is less, and the structural safety meets the requirements.展开更多
The energy retrofit of public buildings is an effective strategy to achieve carbon neutrality goals,with educational buildings representing a significant proportion of this sector.This paper presents an in-depth analy...The energy retrofit of public buildings is an effective strategy to achieve carbon neutrality goals,with educational buildings representing a significant proportion of this sector.This paper presents an in-depth analysis of energy retrofitting policies for educational buildings and examines the design case of the“Plus Energy School”demonstration project in Rostock,Germany.The study reveals innovative approaches in several key areas:overall layout optimization,creation of climate buffer zones,enhancement of building envelope performance,ventilation and heating system design,integration of diverse renewable energy sources,and formulation of energy balance schemes with corresponding calculations.The holistic theory and methodology of this energy strategy synergy offer valuable insights for the retrofitting of existing educational buildings in China.The project successfully transformed two aging school buildings into a single“plus energy”facility through coordinated architectural and technological interventions.Notable features include the compact redesign reducing the form factor from 0.38 to 0.21,the implementation of climate buffer zones maintaining 15℃without active heating,and the integration of photovoltaic panels and wind turbines.The combination of district heating with an Organic Rankine Cycle(ORC)system further optimized energy utilization.Post-retrofit calculations demonstrate a two-thirds reduction in annual unit energy consumption,with the building generating an energy surplus.This case study provides a comprehensive framework for achieving high energy performance in educational building retrofits,offering valuable lessons for similar initiatives in China and globally.The paper concludes by discussing the potential for widespread application of these strategies in China’s existing educational buildings,considering the country’s vast building stock and increasing energy efficiency requirements.展开更多
The green retrofit of existing public buildings is a necessary choice to promote energy conservation,emission reduction,and sustainable development goals in the construction industry,and to advance the implementation ...The green retrofit of existing public buildings is a necessary choice to promote energy conservation,emission reduction,and sustainable development goals in the construction industry,and to advance the implementation of the national"carbon peaking and carbon neutrality"strategy.The effective governance of green retrofit projects for existing public buildings essentially involves a dynamic process of repeated strategic interactions among key stakeholders.From the perspective of project governance,this study clarifies the game-theoretic relationship between ESCO and owners under government guidance,and constructs an evolutionary game model involving the government,ESCO,and owners.The study explores the strategic choices of the core stakeholders in the green retrofit projects of existing public buildings.The aim is to lay a foundation for research on the decision-making coordination and implementation mechanisms between ESCO and owners,thus promoting the efficient and healthy development of green retrofit projects for existing public buildings.展开更多
The aging of existing building curtain walls over time,including cracking,leakage,and material weathering,is analyzed from the perspectives of materials and structure.This article elaborates on the principles of modul...The aging of existing building curtain walls over time,including cracking,leakage,and material weathering,is analyzed from the perspectives of materials and structure.This article elaborates on the principles of modular curtain wall renovation,introduces key technological innovations such as connection technology and structural testing,and also discusses the practical effects of intelligent upgrading of on-site management and modular installation technology.It points out future research directions.展开更多
Purpose – This study aims to analyze the factors, evaluation techniques of the durability of existing railwayengineering.Design/methodology/approach – China has built a railway network of over 150,000 km. Ensuring t...Purpose – This study aims to analyze the factors, evaluation techniques of the durability of existing railwayengineering.Design/methodology/approach – China has built a railway network of over 150,000 km. Ensuring thesafety of the existing railway engineering is of great significance for maintaining normal railway operationorder. However, railway engineering is a strip structure that crosses multiple complex environments. Andrailway engineering will withstand high-frequency impact loads from trains. The above factors have led todifferences in the deterioration characteristics and maintenance strategies of railway engineering compared toconventional concrete structures. Therefore, it is very important to analyze the key factors that affect thedurability of railway structures and propose technologies for durability evaluation.Findings – The factors that affect the durability and reliability of railway engineering are mainly divided intothree categories: material factors, environmental factors and load factors. Among them, material factors alsoinclude influencing factors, such as raw materials, mix proportions and so on. Environmental factors varydepending on the service environment of railway engineering, and the durability and deterioration of concretehave different failure mechanisms. Load factors include static load and train dynamic load. The on-site rapiddetection methods for five common diseases in railway engineering are also proposed in this paper. Thesemethods can quickly evaluate the durability of existing railway engineering concrete.Originality/value – The research can provide some new evaluation techniques and methods for thedurability of existing railway engineering.展开更多
Burial depth is a crucial factor affecting the forces and deformation of tunnels during earthquakes.One key issue is a lack of understanding of the effect of a change in the buried depth of a single-side tunnel on the...Burial depth is a crucial factor affecting the forces and deformation of tunnels during earthquakes.One key issue is a lack of understanding of the effect of a change in the buried depth of a single-side tunnel on the seismic response of a double-tunnel system.In this study,shaking table tests were designed and performed based on a tunnel under construction in Dalian,China.Numerical models were established using the equivalent linear method combined with ABAQUS finite element software to analyze the seismic response of the interacting system.The results showed that the amplification coefficient of the soil acceleration did not change evidently with the burial depth of the new tunnel but decreased as the seismic amplitude increased.In addition,the existing tunnel acceleration,earth pressure,and internal force were hardly affected by the change in the burial depth;for the new tunnel,the acceleration and internal force decreased as the burial depth increased,while the earth pressure increased.This shows that the earth pressure distribution in a double-tunnel system is relatively complex and mainly concentrated on the arch spandrel and arch springing of the relative area.Overall,when the horizontal clearance between the center of the two tunnels was more than twice the sum of the radius of the outer edges of the two tunnels,the change in the burial depth of the new tunnel had little effect on the existing one,and the tunnel structure was deemed safe.These results provide a preliminary understanding and reference for the seismic performance of a double-tunnel system.展开更多
The key to the healthy development of the market for green renovation of existing settlements lies in effectively playing the role of market resource allocation,and scientific evaluation of the current market operatio...The key to the healthy development of the market for green renovation of existing settlements lies in effectively playing the role of market resource allocation,and scientific evaluation of the current market operation efficiency is a prerequisite for the optimization and adjustment of market operation.Based on the perspective of market operation effectiveness,we start from the connotation and significance of the evaluation of the operation efficiency of the market of green renovation of existing settlements,construct the evaluation index system of the operation efficiency of the market of green renovation of existing settlements,use the hierarchical analysis method(AHP)and fuzzy comprehensive evaluation method(Fuzzy),establish the fuzzy comprehensive evaluation model,and finally,based on the operation process reengineering,financing model innovation,service platform expansion and market environment improvement,it structures the operation improvement path of the green renovation market of existing settlements and promotes the orderly operation of the green renovation market of existing settlements.展开更多
The energy-saving renovation of existing residential buildings is a crucial measure to achieve the strategic goal of energy conservation and emission reduction in China and build ecologically livable cities.This artic...The energy-saving renovation of existing residential buildings is a crucial measure to achieve the strategic goal of energy conservation and emission reduction in China and build ecologically livable cities.This article focuses on the perspective of subject behavior,starting from analyzing the current situation and difficulties of the operation of the energy-saving renovation market for existing residential buildings in China,drawing on the practical experience of the operation of the existing residential building energy-saving renovation market abroad.Based on principles such as systematicity,humanization,feasibility,and sustainability,the article constructs an operation optimization system of the existing residential building energy-saving renovation market from the perspective of subject behavior.In order to provide a reference for the healthy and orderly operation of the existing residential building energy-saving renovation market,this paper proposes implementation strategies for optimizing the operation of the existing residential building energy-saving renovation market.Suggestions are proposed from four aspects:optimizing the market environment,innovating the financing model,building the information sharing platform,and utilizing the synergies of the main subjects.展开更多
Combined with current specifications and stress characteristics of concrete filled steel tubular （CFST） arch bridges, the determination principle of safe-middle-failure threestage mode is given. Accordingly, damage ...Combined with current specifications and stress characteristics of concrete filled steel tubular （CFST） arch bridges, the determination principle of safe-middle-failure threestage mode is given. Accordingly, damage probability and failure probability and the corresponding reliability indices are calculated; a direct relationship between reliability indices and three-stage working status is made. Based on the three-stage working mode, a combined FNM （finite element-neural network- Monte-Carlo simulation） method is put forward to estimate the reliability of existing bridges. According to time-dependent reliability theory, subsequent service time is divided into several stages; minimum samples required by the Monte-Carlo method are generated by random sampling; training samples are calculated by the finite element method, and the training samples are extended by the neural network; failure probability and damage probability are calculated by the Monte-Carlo method. Thus, time dependent reliability indices are obtained, and the working status is judged. A case study is investigated to estimate the reliability of an actual bridge by the FNM method. The bridge is a CFST arch bridge with an 83.6 m span and it has been in operation for 10 years. According to analysis results, in the tenth year, the example bridge is still in safe status. This conclusion is consistent with the facts, which proves the feasibility of the FNM method for estimating the reliability of existing bridges.展开更多
The existing state and partitioning of rare earth （RE） on weathered ores in Longnan County（LN）, Xingfeng County（XF） and Ninghua County（NH） were characterized systematically by standard geological analytical me...The existing state and partitioning of rare earth （RE） on weathered ores in Longnan County（LN）, Xingfeng County（XF） and Ninghua County（NH） were characterized systematically by standard geological analytical methods. It is found that RE in the weathered rare earth ores exist as four phases： （a） water soluble, （b） ion-exchangeable, （c） colloidal sediment （oxides）, （d） minerals, in which mainly as ion exchangeable phase, accounting for nearly 80% of total RE, with about 20% in the form of colloid sediment phase and mineral phase, but very little as aqueous soluble phase. These rare earth partitioning were mainly chosen mid-heavy RE elements, occupying above 60%, but not equal in the four phases. The mid-heavy RE elements were primarily enriched in the ion exchangeable phase up to 40%, while the containment of cerium dioxide is below 2 %. The cerium deficiency occurs in the ion exchangeable phase in weathered ore. It results from that the Ce^3＋ is oxidized into Ce^4＋ and changes into CeO2. For LN ore, the containment of Y is high in weathered ore because Y-minerals are abundant in original rock.展开更多
Rare earth element(REE) is widely used in various fields of geology.Study of the existing forms of REE in geological objects is a necessity for us to solve geological problems related with REE.This paper tried to make...Rare earth element(REE) is widely used in various fields of geology.Study of the existing forms of REE in geological objects is a necessity for us to solve geological problems related with REE.This paper tried to make it clear the existing forms of REE in gold-bearing pyrite in Jinshan gold deposit by stepwise dissolution test with ICP-MS analysis.Results showed that content of REE in fluid-inclusions of gold-bearing pyrite was very low,which only took about 0.07%–0.70% of the ΣREE,and that of pyrite phase ...展开更多
The improvement of the seismic resilience of existing reinforced-concrete(RC) frame buildings, which is essential for the seismic resilience of a city, has become a critical issue. Although seismic isolation is an eff...The improvement of the seismic resilience of existing reinforced-concrete(RC) frame buildings, which is essential for the seismic resilience of a city, has become a critical issue. Although seismic isolation is an effective method for improving the resilient performance of such buildings, target-oriented quantitative improvements of the resilient performance of these buildings have been reported rarely. To address this gap, the seismic resilience of two existing RC frame buildings located in a high seismic intensity region of China were assessed based on the Chinese Standard for Seismic Resilience Assessment of Buildings. The critical engineering demand parameters(EDPs) affecting the seismic resilience of such buildings were identified. Subsequently, the seismic resilience of buildings retrofitted with different isolation schemes(i.e., yield ratios) were evaluated and compared, with emphasis on the relationships among yield ratios, EDPs, and levels of seismic resilience. Accordingly, to achieve the highest level of seismic resilience with respect to the Chinese standard, a yield ratio of 3% was recommended and successfully applied to the target-oriented design for the seismic-resilience improvement of an existing RC frame building. The research outcome can provide an important reference for the resilience-based retrofitting of existing RC frame buildings using seismic isolation in urban cities.展开更多
To relieve the increasing traffic load, many early built highways need to be widened or reconstructed. The rapid performance detection to existing subgrades is important to their reasonable evaluation and maximized ut...To relieve the increasing traffic load, many early built highways need to be widened or reconstructed. The rapid performance detection to existing subgrades is important to their reasonable evaluation and maximized utilization. Based on five kinds of soils taken from an existing highway in southern China, three commonly detecting methods were used to determine their moisture contents, compaction degrees and resilient moduli. The results showed that the measured moisture contents were greater than the design value, and the compaction degrees decreased sharply compared to the original ones. The moisture and heat exchange produced a decrease in the resilient modulus of plate loading test(PLT) from the standard 60 MPa down to 40 MPa. Afterwards, the portable falling weight deflectometer(PFWD) and dynamic cone penetrometer(DCP) were used to evaluate the subgrade performances. The measured PFWD moduli and the DCP penetration rates were correlated with the resilient moduli of PLT, deflections of the Beckman beam test, compaction degrees and moisture contents. The correlation analysis indicates that both of two methods are suitable in rapid detecting subgrade performances, but PFWD method is more recommended for it has higher accuracy and efficiency.展开更多
In order to investigate the existing form and action mechanism of minor scandium （Sc） and zirconium （Zr） in AI-Cu-Mg alloy, microstructures of Al-4Cu-1Mg-Sc-Zr alloy under different conditions, including states of...In order to investigate the existing form and action mechanism of minor scandium （Sc） and zirconium （Zr） in AI-Cu-Mg alloy, microstructures of Al-4Cu-1Mg-Sc-Zr alloy under different conditions, including states of as-cast, homogenized, hot-rolled, as-solution and natural aged, were observed by scanning electron microscopy （SEM）, X-ray diffractometry （XRD） and transmission electron microscopy （TEM）. It is revealed that Sc and Zr are completely dissolved into the supersaturated solid solution in as-cast ingot, but grain refinement is not observed. Coffee-bean-like AI3（Sc, Zr） particles deposit during homogenization of ingot induce an increase in hardness. Al3（Sc, Zr） particles are slightly coarsened in as-solution samples, but they still maintain coherent to matrix, which indicates a high thermal stability of these particles. Good coherency ofAl3（Sc, Zr） particles makes some benefits for inhibiting recrystallization and reserving work-hardening.展开更多
Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other a...Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other aggressive environments. A study of reinforced concrete structures located at the Fangcheng dock in the Beibu Gulf port, China, was present. The result from field survey indicates that the concrete cover depth and chloride diffusion coefficient fit best normal distribution and lognormal distribution, respectively. The service life of structure is about 55 a, while initiation time is 45 a. Sensitivity analysis indicates that the most influential factor of the structure service life prediction is concrete cover, followed by diffusion coefficient, diffusion decay index, critical chloride concentration, surface chloride concentration, current density and localized pitting corrosion. Finally, the effects of diffusion decay index and critical chloride concentration on structure service life prediction are discussed.展开更多
The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Lon...The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Long-term safety primarily includes the analysis of all hazards affecting the project; that is, hazards from the natural environment, hazards from the man-made environment, and project-specific and site-specific hazards. The special features of the seismic safety of dams are discussed. Large dams were the first structures to be systematically designed against earthquakes, starting in the 1930s. How- ever, the seismic safety of older dams is unknown, as most were designed using seismic design criteria and methods of dynamic analysis that are considered obsolete today. Therefore, we need to reevaluate the seismic safety of existing dams based on current state-of-the-art practices and rehabilitate deficient dams. For large dams, a site-specific seismic hazard analysis is usually recommended. Today, large dams and the safety-relevant elements used for controlling the reservoir after a strong earthquake must be able to withstand the ground motions of a safety evaluation earthquake. The ground motion parameters can be determined either by a probabilistic or a deterministic seismic hazard analysis. During strong earthquakes, inelastic deformations may occur in a dam; therefore, the seismic analysis has to be car- ried out in the time domain. Furthermore, earthquakes create multiple seismic hazards for dams such as ground shaking, fault movements, mass movements, and others. The ground motions needed by the dam engineer are not real earthquake ground motions but models of the ground motion, which allow the safe design of dams. It must also be kept in mind that darn safety evaluations must be carried out several times during the long life of large storage dams. These features are discussed in this paper.展开更多
Based on the engineering background of the contact channel between Shangyang and Gushan of Fuzhou Metro Line 2 undercrossing the existing tunnel line,the freezing temperature field of the contact channel,the displacem...Based on the engineering background of the contact channel between Shangyang and Gushan of Fuzhou Metro Line 2 undercrossing the existing tunnel line,the freezing temperature field of the contact channel,the displacement field of the existing tunnel line and the contact channel with different net distances and horizontal angles are analyzed by ANSYS finite element software and field measurement method.The obtained results indicate that during the freezing period,the temperature drops at different measuring holes are almost the same.The temperature near the bottom freezing tube drops faster than that far from the tube.It is found that the bilateral freezing technique improves the formation of the freezing wall in the intersection area.In this case,the intersection time of the cross-section is 7 days faster than that of the adjacent ordinary section.The change curve of the displacement of the surface uplift in different freezing periods with the distance from the center of the channel is“M”shaped.The maximum uplift displacement at 12 m from channel center is 25 mm.The vertical displacement of the measuring point located above the central axis of the connecting channel is large.The farther the point from the central axis,the smaller the corresponding vertical displacement.When the horizontal angle between the existing tunnel and the connecting channel is less than 60,the existing vertical displacement of the tunnel changes rapidly with the horizontal angle,reaching 0.17 mm/.Meanwhile,when the net distance is less than 6.1 m,the change rate of the vertical displacement of the tunnel is up to 2.4 mm/m.展开更多
Seismic hazard levels lower than those for design of new buildings have been permitted for seismic evaluation and retrofi t of existing buildings due to the relatively short remaining lifespans. The seismic hazard red...Seismic hazard levels lower than those for design of new buildings have been permitted for seismic evaluation and retrofi t of existing buildings due to the relatively short remaining lifespans. The seismic hazard reduction enables costeff ective seismic evaluation and retrofi t of existing buildings with limited structural capacity. The current study proposes seismic hazard reduction factors for Korea, one of low to moderate seismicity regions. The seismic hazard reduction factors are based on equal probabilities of non-exceedance within diff erent remaining building lifespans. A validation procedure is proposed to investigate equality of seismic risk in terms of ductility-based limit states using seismic fragility assessment of nonlinear SDOF systems, of which retrofi t demands are determined by the displacement coeffi cient method of ASCE 41-13 for diff erent target remaining building lifespans and corresponding reduced design earthquakes. Validation result shows that the use of seismic hazard reduction factors can be permitted in conjunction with appropriate lower bounds of the remaining building lifespans.展开更多
Water distribution network(WDN)leakage management has received increased attention in recent years.One of the most successful leakage-control strategies is to divide the network into District Metered Areas(DMAs).As a ...Water distribution network(WDN)leakage management has received increased attention in recent years.One of the most successful leakage-control strategies is to divide the network into District Metered Areas(DMAs).As a multi-staged technique,the generation of DMAs is a difficult task in design and implementation(i.e.,clustering,sectorization,and performance evaluation).Previous studies on DMAs implementation did not consider the potential use of existing valves in achieving the objective.In this work,a methodology is proposed for detecting clusters and reducing the cost of additional valves and DMA sectorization by considering existing valves as much as possible.The procedure of DMAs identification has been divided into three stages,i.e.,a)clusters identification;b)sectorization or boundaries optimization and c)performance evaluation of the partitioned network.The proposed methodology is evaluated on a simple network and a real-world water network with the findings provided and compared to the DMAs,established for a raw water network with no existing valves.It is found that there is an adequate difference in cost of strategy implementation in both the cases for the network under consideration and the existing valve system achieved better network performance in terms of resilience index.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.52078334)the National Key Research and Development Program of China(Grant No.2017YFC0805402)the Tianjin Research Innovation Project for Postgraduate Students(Grant No.2021YJSB141).
文摘The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.
文摘The construction of the new tunnel under the existing railway will break the original stress balance in the engineering area, resulting in the secondary redistribution of surrounding rock stress. The large amount of excavation unloading of the soil below is also easy to induce the uneven settlement deformation of the existing structure above, affecting the safety of driving. Based on the shield tunnel project between Caoqiao Station and Lize Business District Station of Beijing Metro, this paper restores the construction site by constructing the finite element numerical model of the project area, calculates and analyzes the deformation and stress of the existing railway structure before and after the construction of the tunnel, and determines the safety impact of the new structure on the existing railway. The results show that the shield tunnel undercrossing construction will cause the “concave” settlement of the railway subgrade above. Under the condition of grouting reinforcement, the “concave” settlement curve is slower and the distribution range is wider. With the advancement of the construction step, the settlement deformation of the subgrade gradually increases. When the tunnel approaches and passes directly below the subgrade, the settlement deformation curve of the subgrade changes from slow to steep. After the tunnel passes away, the curve changes from steep to slow, and the deformation of the subgrade reaches the maximum after the tunnel is connected. Under the grouting condition, the maximum settlement deformation of the subgrade is 2.08 mm, which is about 45% of the settlement deformation of the subgrade under the non-grouting condition. The ground grouting reinforcement can effectively control the subgrade settlement, and the field monitoring verifies the rationality of the calculation results. After the tunnel passes underneath, the most unfavorable section of the existing railway frame bridge is located at the top plate of the structure, and the maximum crack width is 0.178 mm. After grouting reinforcement, the stress environment of the structure is improved, the crack width generated by the structure is smaller, the reinforcement area required for calculation is less, and the structural safety meets the requirements.
文摘The energy retrofit of public buildings is an effective strategy to achieve carbon neutrality goals,with educational buildings representing a significant proportion of this sector.This paper presents an in-depth analysis of energy retrofitting policies for educational buildings and examines the design case of the“Plus Energy School”demonstration project in Rostock,Germany.The study reveals innovative approaches in several key areas:overall layout optimization,creation of climate buffer zones,enhancement of building envelope performance,ventilation and heating system design,integration of diverse renewable energy sources,and formulation of energy balance schemes with corresponding calculations.The holistic theory and methodology of this energy strategy synergy offer valuable insights for the retrofitting of existing educational buildings in China.The project successfully transformed two aging school buildings into a single“plus energy”facility through coordinated architectural and technological interventions.Notable features include the compact redesign reducing the form factor from 0.38 to 0.21,the implementation of climate buffer zones maintaining 15℃without active heating,and the integration of photovoltaic panels and wind turbines.The combination of district heating with an Organic Rankine Cycle(ORC)system further optimized energy utilization.Post-retrofit calculations demonstrate a two-thirds reduction in annual unit energy consumption,with the building generating an energy surplus.This case study provides a comprehensive framework for achieving high energy performance in educational building retrofits,offering valuable lessons for similar initiatives in China and globally.The paper concludes by discussing the potential for widespread application of these strategies in China’s existing educational buildings,considering the country’s vast building stock and increasing energy efficiency requirements.
基金supported by the National Natural Science Foundation of China(Grant No.71872122)the Late-stage Subsidy Project of Humanities and Social Sciences of the Education Department of China(Grant No.20JHQ095).
文摘The green retrofit of existing public buildings is a necessary choice to promote energy conservation,emission reduction,and sustainable development goals in the construction industry,and to advance the implementation of the national"carbon peaking and carbon neutrality"strategy.The effective governance of green retrofit projects for existing public buildings essentially involves a dynamic process of repeated strategic interactions among key stakeholders.From the perspective of project governance,this study clarifies the game-theoretic relationship between ESCO and owners under government guidance,and constructs an evolutionary game model involving the government,ESCO,and owners.The study explores the strategic choices of the core stakeholders in the green retrofit projects of existing public buildings.The aim is to lay a foundation for research on the decision-making coordination and implementation mechanisms between ESCO and owners,thus promoting the efficient and healthy development of green retrofit projects for existing public buildings.
文摘The aging of existing building curtain walls over time,including cracking,leakage,and material weathering,is analyzed from the perspectives of materials and structure.This article elaborates on the principles of modular curtain wall renovation,introduces key technological innovations such as connection technology and structural testing,and also discusses the practical effects of intelligent upgrading of on-site management and modular installation technology.It points out future research directions.
基金funded by the National Key Research and Development Program of China(No:2020YFC1909900)the National Natural Science Foundation of China(No:51908550)the Scientific Research Project of China Academy of Railway Sciences Group Corporation Limited(No:2021YJ173).
文摘Purpose – This study aims to analyze the factors, evaluation techniques of the durability of existing railwayengineering.Design/methodology/approach – China has built a railway network of over 150,000 km. Ensuring thesafety of the existing railway engineering is of great significance for maintaining normal railway operationorder. However, railway engineering is a strip structure that crosses multiple complex environments. Andrailway engineering will withstand high-frequency impact loads from trains. The above factors have led todifferences in the deterioration characteristics and maintenance strategies of railway engineering compared toconventional concrete structures. Therefore, it is very important to analyze the key factors that affect thedurability of railway structures and propose technologies for durability evaluation.Findings – The factors that affect the durability and reliability of railway engineering are mainly divided intothree categories: material factors, environmental factors and load factors. Among them, material factors alsoinclude influencing factors, such as raw materials, mix proportions and so on. Environmental factors varydepending on the service environment of railway engineering, and the durability and deterioration of concretehave different failure mechanisms. Load factors include static load and train dynamic load. The on-site rapiddetection methods for five common diseases in railway engineering are also proposed in this paper. Thesemethods can quickly evaluate the durability of existing railway engineering concrete.Originality/value – The research can provide some new evaluation techniques and methods for thedurability of existing railway engineering.
基金Scientific Research Fund of Liaoning Provincial Education Department under Grant No.LJKZ0336。
文摘Burial depth is a crucial factor affecting the forces and deformation of tunnels during earthquakes.One key issue is a lack of understanding of the effect of a change in the buried depth of a single-side tunnel on the seismic response of a double-tunnel system.In this study,shaking table tests were designed and performed based on a tunnel under construction in Dalian,China.Numerical models were established using the equivalent linear method combined with ABAQUS finite element software to analyze the seismic response of the interacting system.The results showed that the amplification coefficient of the soil acceleration did not change evidently with the burial depth of the new tunnel but decreased as the seismic amplitude increased.In addition,the existing tunnel acceleration,earth pressure,and internal force were hardly affected by the change in the burial depth;for the new tunnel,the acceleration and internal force decreased as the burial depth increased,while the earth pressure increased.This shows that the earth pressure distribution in a double-tunnel system is relatively complex and mainly concentrated on the arch spandrel and arch springing of the relative area.Overall,when the horizontal clearance between the center of the two tunnels was more than twice the sum of the radius of the outer edges of the two tunnels,the change in the burial depth of the new tunnel had little effect on the existing one,and the tunnel structure was deemed safe.These results provide a preliminary understanding and reference for the seismic performance of a double-tunnel system.
基金supported by the National Natural Science Foundation of China(Grant No.71872122)the Late-stage Subsidy Project of Humanities and Social Sciences of the Education Department of China(Grant No.20JHQ095).
文摘The key to the healthy development of the market for green renovation of existing settlements lies in effectively playing the role of market resource allocation,and scientific evaluation of the current market operation efficiency is a prerequisite for the optimization and adjustment of market operation.Based on the perspective of market operation effectiveness,we start from the connotation and significance of the evaluation of the operation efficiency of the market of green renovation of existing settlements,construct the evaluation index system of the operation efficiency of the market of green renovation of existing settlements,use the hierarchical analysis method(AHP)and fuzzy comprehensive evaluation method(Fuzzy),establish the fuzzy comprehensive evaluation model,and finally,based on the operation process reengineering,financing model innovation,service platform expansion and market environment improvement,it structures the operation improvement path of the green renovation market of existing settlements and promotes the orderly operation of the green renovation market of existing settlements.
基金supported by the National Natural Science Foundation of China(Grant No.71872122)Late-stage Subsidy Project of Humanities and Social Sciences of the Education Department of China(Grant No.20JHQ095).
文摘The energy-saving renovation of existing residential buildings is a crucial measure to achieve the strategic goal of energy conservation and emission reduction in China and build ecologically livable cities.This article focuses on the perspective of subject behavior,starting from analyzing the current situation and difficulties of the operation of the energy-saving renovation market for existing residential buildings in China,drawing on the practical experience of the operation of the existing residential building energy-saving renovation market abroad.Based on principles such as systematicity,humanization,feasibility,and sustainability,the article constructs an operation optimization system of the existing residential building energy-saving renovation market from the perspective of subject behavior.In order to provide a reference for the healthy and orderly operation of the existing residential building energy-saving renovation market,this paper proposes implementation strategies for optimizing the operation of the existing residential building energy-saving renovation market.Suggestions are proposed from four aspects:optimizing the market environment,innovating the financing model,building the information sharing platform,and utilizing the synergies of the main subjects.
基金The National Natural Science Foundation of China(No.10672060)
文摘Combined with current specifications and stress characteristics of concrete filled steel tubular （CFST） arch bridges, the determination principle of safe-middle-failure threestage mode is given. Accordingly, damage probability and failure probability and the corresponding reliability indices are calculated; a direct relationship between reliability indices and three-stage working status is made. Based on the three-stage working mode, a combined FNM （finite element-neural network- Monte-Carlo simulation） method is put forward to estimate the reliability of existing bridges. According to time-dependent reliability theory, subsequent service time is divided into several stages; minimum samples required by the Monte-Carlo method are generated by random sampling; training samples are calculated by the finite element method, and the training samples are extended by the neural network; failure probability and damage probability are calculated by the Monte-Carlo method. Thus, time dependent reliability indices are obtained, and the working status is judged. A case study is investigated to estimate the reliability of an actual bridge by the FNM method. The bridge is a CFST arch bridge with an 83.6 m span and it has been in operation for 10 years. According to analysis results, in the tenth year, the example bridge is still in safe status. This conclusion is consistent with the facts, which proves the feasibility of the FNM method for estimating the reliability of existing bridges.
文摘The existing state and partitioning of rare earth （RE） on weathered ores in Longnan County（LN）, Xingfeng County（XF） and Ninghua County（NH） were characterized systematically by standard geological analytical methods. It is found that RE in the weathered rare earth ores exist as four phases： （a） water soluble, （b） ion-exchangeable, （c） colloidal sediment （oxides）, （d） minerals, in which mainly as ion exchangeable phase, accounting for nearly 80% of total RE, with about 20% in the form of colloid sediment phase and mineral phase, but very little as aqueous soluble phase. These rare earth partitioning were mainly chosen mid-heavy RE elements, occupying above 60%, but not equal in the four phases. The mid-heavy RE elements were primarily enriched in the ion exchangeable phase up to 40%, while the containment of cerium dioxide is below 2 %. The cerium deficiency occurs in the ion exchangeable phase in weathered ore. It results from that the Ce^3＋ is oxidized into Ce^4＋ and changes into CeO2. For LN ore, the containment of Y is high in weathered ore because Y-minerals are abundant in original rock.
基金supported by the National Natural Science Foundation of China (40373025)
文摘Rare earth element(REE) is widely used in various fields of geology.Study of the existing forms of REE in geological objects is a necessity for us to solve geological problems related with REE.This paper tried to make it clear the existing forms of REE in gold-bearing pyrite in Jinshan gold deposit by stepwise dissolution test with ICP-MS analysis.Results showed that content of REE in fluid-inclusions of gold-bearing pyrite was very low,which only took about 0.07%–0.70% of the ΣREE,and that of pyrite phase ...
基金Beijing Natural Science Foundation under Grant No. 8192008the Scientific Research Foundation of Graduate School of Southeast University under Grant No. YBPY2021+1 种基金the Science and Technology Project of Beijing Municipal Education Commission under Grant No. KM201910016014the Program for Changjiang Scholars and Innovative Research Team in University under Grant No. IRT_17R06。
文摘The improvement of the seismic resilience of existing reinforced-concrete(RC) frame buildings, which is essential for the seismic resilience of a city, has become a critical issue. Although seismic isolation is an effective method for improving the resilient performance of such buildings, target-oriented quantitative improvements of the resilient performance of these buildings have been reported rarely. To address this gap, the seismic resilience of two existing RC frame buildings located in a high seismic intensity region of China were assessed based on the Chinese Standard for Seismic Resilience Assessment of Buildings. The critical engineering demand parameters(EDPs) affecting the seismic resilience of such buildings were identified. Subsequently, the seismic resilience of buildings retrofitted with different isolation schemes(i.e., yield ratios) were evaluated and compared, with emphasis on the relationships among yield ratios, EDPs, and levels of seismic resilience. Accordingly, to achieve the highest level of seismic resilience with respect to the Chinese standard, a yield ratio of 3% was recommended and successfully applied to the target-oriented design for the seismic-resilience improvement of an existing RC frame building. The research outcome can provide an important reference for the resilience-based retrofitting of existing RC frame buildings using seismic isolation in urban cities.
基金Project(2017YFC0805307) supported by the National Key Research and Development Program of ChinaProjects(51878078, 51927814, 51911530215) supported by the National Natural Science Foundation of China+4 种基金Project(2018-025) supported by the Training Program for High-level Technical Personnel in Transportation Industry, ChinaProject (2018JJ1026) supported by the Excellent Youth Foundation of Natural Science Foundation of Hunan Province, ChinaProject(17A008) supported by the Key Project of Education Department of Hunan Province, ChinaProjects(kfj150103, kfj170104) supported by the Open Research Fund of State Engineering Laboratory of Highway Maintenance Technology, Changsha University of Science & Technology, ChinaProject(CX20190644) supported by the Postgraduate Scientific Research Innovation Project of Hunan Province, China。
文摘To relieve the increasing traffic load, many early built highways need to be widened or reconstructed. The rapid performance detection to existing subgrades is important to their reasonable evaluation and maximized utilization. Based on five kinds of soils taken from an existing highway in southern China, three commonly detecting methods were used to determine their moisture contents, compaction degrees and resilient moduli. The results showed that the measured moisture contents were greater than the design value, and the compaction degrees decreased sharply compared to the original ones. The moisture and heat exchange produced a decrease in the resilient modulus of plate loading test(PLT) from the standard 60 MPa down to 40 MPa. Afterwards, the portable falling weight deflectometer(PFWD) and dynamic cone penetrometer(DCP) were used to evaluate the subgrade performances. The measured PFWD moduli and the DCP penetration rates were correlated with the resilient moduli of PLT, deflections of the Beckman beam test, compaction degrees and moisture contents. The correlation analysis indicates that both of two methods are suitable in rapid detecting subgrade performances, but PFWD method is more recommended for it has higher accuracy and efficiency.
基金Project(2005DFA50550) supported by International Science and Technology Cooperation Program of ChinaProject(2005CB623705) supported by the National Basic Research Program of China
文摘In order to investigate the existing form and action mechanism of minor scandium （Sc） and zirconium （Zr） in AI-Cu-Mg alloy, microstructures of Al-4Cu-1Mg-Sc-Zr alloy under different conditions, including states of as-cast, homogenized, hot-rolled, as-solution and natural aged, were observed by scanning electron microscopy （SEM）, X-ray diffractometry （XRD） and transmission electron microscopy （TEM）. It is revealed that Sc and Zr are completely dissolved into the supersaturated solid solution in as-cast ingot, but grain refinement is not observed. Coffee-bean-like AI3（Sc, Zr） particles deposit during homogenization of ingot induce an increase in hardness. Al3（Sc, Zr） particles are slightly coarsened in as-solution samples, but they still maintain coherent to matrix, which indicates a high thermal stability of these particles. Good coherency ofAl3（Sc, Zr） particles makes some benefits for inhibiting recrystallization and reserving work-hardening.
基金Project(41274012) supported by the National Natural Science Foundation of China
文摘Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other aggressive environments. A study of reinforced concrete structures located at the Fangcheng dock in the Beibu Gulf port, China, was present. The result from field survey indicates that the concrete cover depth and chloride diffusion coefficient fit best normal distribution and lognormal distribution, respectively. The service life of structure is about 55 a, while initiation time is 45 a. Sensitivity analysis indicates that the most influential factor of the structure service life prediction is concrete cover, followed by diffusion coefficient, diffusion decay index, critical chloride concentration, surface chloride concentration, current density and localized pitting corrosion. Finally, the effects of diffusion decay index and critical chloride concentration on structure service life prediction are discussed.
文摘The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Long-term safety primarily includes the analysis of all hazards affecting the project; that is, hazards from the natural environment, hazards from the man-made environment, and project-specific and site-specific hazards. The special features of the seismic safety of dams are discussed. Large dams were the first structures to be systematically designed against earthquakes, starting in the 1930s. How- ever, the seismic safety of older dams is unknown, as most were designed using seismic design criteria and methods of dynamic analysis that are considered obsolete today. Therefore, we need to reevaluate the seismic safety of existing dams based on current state-of-the-art practices and rehabilitate deficient dams. For large dams, a site-specific seismic hazard analysis is usually recommended. Today, large dams and the safety-relevant elements used for controlling the reservoir after a strong earthquake must be able to withstand the ground motions of a safety evaluation earthquake. The ground motion parameters can be determined either by a probabilistic or a deterministic seismic hazard analysis. During strong earthquakes, inelastic deformations may occur in a dam; therefore, the seismic analysis has to be car- ried out in the time domain. Furthermore, earthquakes create multiple seismic hazards for dams such as ground shaking, fault movements, mass movements, and others. The ground motions needed by the dam engineer are not real earthquake ground motions but models of the ground motion, which allow the safe design of dams. It must also be kept in mind that darn safety evaluations must be carried out several times during the long life of large storage dams. These features are discussed in this paper.
基金This research was supported by the project of Natural Science Foundation of Fujian Province(No.2022J01925)supported by the project of the Fuzhou Science and Technology Plan Project(2021-P-047)supported by the Open Project Program Foundation of Engineering Research Center of underground mine construction,Ministry of Education(Anhui University of Science and Technology)(No.JYBGCZX2021104).
文摘Based on the engineering background of the contact channel between Shangyang and Gushan of Fuzhou Metro Line 2 undercrossing the existing tunnel line,the freezing temperature field of the contact channel,the displacement field of the existing tunnel line and the contact channel with different net distances and horizontal angles are analyzed by ANSYS finite element software and field measurement method.The obtained results indicate that during the freezing period,the temperature drops at different measuring holes are almost the same.The temperature near the bottom freezing tube drops faster than that far from the tube.It is found that the bilateral freezing technique improves the formation of the freezing wall in the intersection area.In this case,the intersection time of the cross-section is 7 days faster than that of the adjacent ordinary section.The change curve of the displacement of the surface uplift in different freezing periods with the distance from the center of the channel is“M”shaped.The maximum uplift displacement at 12 m from channel center is 25 mm.The vertical displacement of the measuring point located above the central axis of the connecting channel is large.The farther the point from the central axis,the smaller the corresponding vertical displacement.When the horizontal angle between the existing tunnel and the connecting channel is less than 60,the existing vertical displacement of the tunnel changes rapidly with the horizontal angle,reaching 0.17 mm/.Meanwhile,when the net distance is less than 6.1 m,the change rate of the vertical displacement of the tunnel is up to 2.4 mm/m.
基金supported by the Incheon National University Research Grant in 2015
文摘Seismic hazard levels lower than those for design of new buildings have been permitted for seismic evaluation and retrofi t of existing buildings due to the relatively short remaining lifespans. The seismic hazard reduction enables costeff ective seismic evaluation and retrofi t of existing buildings with limited structural capacity. The current study proposes seismic hazard reduction factors for Korea, one of low to moderate seismicity regions. The seismic hazard reduction factors are based on equal probabilities of non-exceedance within diff erent remaining building lifespans. A validation procedure is proposed to investigate equality of seismic risk in terms of ductility-based limit states using seismic fragility assessment of nonlinear SDOF systems, of which retrofi t demands are determined by the displacement coeffi cient method of ASCE 41-13 for diff erent target remaining building lifespans and corresponding reduced design earthquakes. Validation result shows that the use of seismic hazard reduction factors can be permitted in conjunction with appropriate lower bounds of the remaining building lifespans.
文摘Water distribution network(WDN)leakage management has received increased attention in recent years.One of the most successful leakage-control strategies is to divide the network into District Metered Areas(DMAs).As a multi-staged technique,the generation of DMAs is a difficult task in design and implementation(i.e.,clustering,sectorization,and performance evaluation).Previous studies on DMAs implementation did not consider the potential use of existing valves in achieving the objective.In this work,a methodology is proposed for detecting clusters and reducing the cost of additional valves and DMA sectorization by considering existing valves as much as possible.The procedure of DMAs identification has been divided into three stages,i.e.,a)clusters identification;b)sectorization or boundaries optimization and c)performance evaluation of the partitioned network.The proposed methodology is evaluated on a simple network and a real-world water network with the findings provided and compared to the DMAs,established for a raw water network with no existing valves.It is found that there is an adequate difference in cost of strategy implementation in both the cases for the network under consideration and the existing valve system achieved better network performance in terms of resilience index.
