A steel-concrete composite cable-stayed bridge features integrated steel girders and concrete decks linked by shear connectors to support loads,but stress concentration in wet joints can lead to cracking.In-situ tests...A steel-concrete composite cable-stayed bridge features integrated steel girders and concrete decks linked by shear connectors to support loads,but stress concentration in wet joints can lead to cracking.In-situ tests were conducted on key sections of steel-concrete composite cable-stayed bridges to analyze the stress-strain evolution of wet joints under environmental factors,constraints,and complex construction processes.The coordinated working performance of the bridge decks was also analyzed.The results indicate that temperature is the key factor affecting the stresses and strains in wet joint concrete.Approximately 7 days after casting the wet joint concrete,the strains at each measurement point of the wet joint are approximately negatively correlated with the temperature change at the measurement point.Different locations within the wet joints have respective impacts,presenting potential weak points.Construction conditions have a certain impact on the stress and strain of the wet joint.The top deck of the steel box girder is not fully bonded to the bottom surface of the wet joints,resulting in a certain strain difference after loading.To further analyze the cooperative working performance of steel box girders and concrete wet joint bridge deck systems,finite element analysis was conducted on composite girder structures.A stiffness calculation method for shear connectors based on numerical simulation was proposed.The results indicate that strain differences can cause interface slip in composite girders.This slip leads to increased deflection of the composite girders and increased tensile stress in the bottom plate of the steel box girders.This study clarifies the stress conditions and factors affecting wet joints during construction,preventing early cracking,and offers precise data for a full bridge finite element model.展开更多
The steel tube arch rib in a large-span concrete-filled steel tube arch bridge has a large span and diameter,which also leads to a larger weld seam scale.Large-scale welding seams will inevitably cause more obvious we...The steel tube arch rib in a large-span concrete-filled steel tube arch bridge has a large span and diameter,which also leads to a larger weld seam scale.Large-scale welding seams will inevitably cause more obvious welding residual stress(WRS).For the purpose of studying the influence of WRS from large-scale welding seam on the mechanical properties of steel tube arch rib during arch rib splicing,test research and numerical simulation analysis on the WRS in arch rib splicing based on the Guangxi Pingnan Third Bridge,which is the world’s largest span concrete-filled steel tube arch bridge,were conducted in this paper,and the distribution pattern of WRS at the arch rib splicing joint was obtained.Subsequently,the WRS was introduced into the mechanical performance analysis of joints and structures to analyze its effects.The findings reveal that the distribution of WRS in the arch rib is greatly influenced by the rib plate,and the axial WRS in the heat-affected zone are primarily tensile,while the circumferential WRS are distributed in an alternating pattern of tensile and compressive stresses along the circumferential direction of the main tube.Under the influence of WRS,the ultimate bearing capacity of the joint is reduced by 29.4%,the initial axial stiffness is reduced by 4.32%,and the vertical deformation of the arch rib structure is increased by 4.7%.展开更多
The surrounding rock is prone to large-scale loosening and failure after the excavation of shallow large-span caverns because of the thin overlying strata and large cross-section span.The rational design of bolt suppo...The surrounding rock is prone to large-scale loosening and failure after the excavation of shallow large-span caverns because of the thin overlying strata and large cross-section span.The rational design of bolt support is very important to the safety control of surrounding rock as a common support means.The control mechanism and design method of bolt support for shallow-buried large-span caverns is carried out.The calculation method of bolt prestress and length based on arched failure and collapsed failure mode is established.The influence mechanism of different influencing factors on the bolt prestress and length is clarified.At the same time,the constant resistance energy-absorbing bolt with high strength and high toughness is developed,and the comparative test of mechanical properties is carried out.On this basis,the design method of high prestressed bolt support for shallow-buried large-span caverns is put forward,and the field test is carried out in Qingdao metro station in China.The monitoring results show that the maximum roof settlement is 6.8 mm after the new design method is adopted,and the effective control of the shallow-buried large-span caverns is realized.The research results can provide theoretical and technical support for the safety control of shallow-buried large-span caverns.展开更多
Welded Turnout on Large-span Bridge(WTLB)is a complex multi-layer heterogeneous system and can significantly influence the service performance of High-Speed Railway(HSR).Understanding the coupling dynamic response of ...Welded Turnout on Large-span Bridge(WTLB)is a complex multi-layer heterogeneous system and can significantly influence the service performance of High-Speed Railway(HSR).Understanding the coupling dynamic response of the vehicle and WTLB is essential.Previous research did not consider the dynamic behavior of foundations,leading to an underestimation of the vehicle-turnout-foundation coupling dynamic response,particularly when turnouts were laid on large-span bridges.This study proposes a novel modeling method that includes the foundations,to overcome the previous shortcomings by applying a rigid-flexible coupling system.In this approach,the vehicle was modeled as a rigid body sub-model in a Multi-Body Software(MBS),while WTLB was modeled as a flexible bodies sub-model using Finite Element(FE)software.The modal information from the FE model was imported into the MBS software.The two sub-models were coupled by the wheel-rail contact in the MBS environment and then the Vehicle-turnout-bridge Rigid-flexible Coupling Dynamic(VRCD)calculation model was established and it was discovered that the calculation results showed good agreement with the field test data.Through the VRCD model,the safety of the structure,the stability of the vehicle and the comfort of passengers were investigated,as well as several important infrastructure factors.The results demonstrate that this novel method provides accurate calculations and highlights the complex and significant interactions in the vehicle-turnout-bridge system.展开更多
The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock.The development of a new type of foam concrete which has the property of high compressibility and lo...The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock.The development of a new type of foam concrete which has the property of high compressibility and low ductility was introduced.And it was made as filling material of reserved deformation layer between the first lining and the second lining used in large-span soft rock tunnel.The effect of the new type of foam concrete was simulated as filling material of reserved deformation layer using numerical simulation.Through the comparison with the common large-span soft rock tunnel,the vault settlement and surrounding convergence are reduced by about 61% and 45%,respectively,after creep of 100 a.And in the second lining,the plastic zone reduces apparently and the maximum equivalent plastic strain decreases relatively.So,it can be found that the application of the new type of foam concrete as the filling material of reserved deformation layer can relieve the excessive force in second lining induced by rock creep,reduce its deformation and improve the stability of tunnel.展开更多
In order to study the distribution laws and types of plastic zone of surrounding rock in large-span roadway, we analyzed the distribution laws with different spans and lateral pressures using FLAC3D numerical calcu- l...In order to study the distribution laws and types of plastic zone of surrounding rock in large-span roadway, we analyzed the distribution laws with different spans and lateral pressures using FLAC3D numerical calcu- lation software. Based on the roadway support difficulty and distribution laws of the plastic zone of sur- rounding rock, we defined the large-span roadway and classified the types of large-span rectangular roadways. As a result, the distribution laws of the plastic zone on surrounding rock in a rectangular roadway with different spans and lateral pressures were obtained. The results show that the area of the plastic zone on surrounding rock increased with the increase of the spans and lateral pressures, and the plastic zone was symmetrical to the center line of roadway. At λ=0.5, 1.0, 1.5, and 2.0, the plastic zone presented ＂addle- shape＂ distribution, ＂ellipse＂ distribution, ＂thin and high＂ distribution and ＂inverse trapezium＂ distribu- tion, respectively. In addition, we classified the roadways into four types according to the different lateral pressures and spans, including small-span, moderate-span, large-span and extreme-large-span roadways.展开更多
A section of the Nanliang high speed railway tunnel on Shijiazhuang-Taiyuan high-speed passenger railway line in China was instrumented and studied for its mechanical properties and performances. The cross section for...A section of the Nanliang high speed railway tunnel on Shijiazhuang-Taiyuan high-speed passenger railway line in China was instrumented and studied for its mechanical properties and performances. The cross section for the tunnel was300 m2and is classified as the largest cross section for railway tunnels in China. Through in situ experimental studies, mechanistic properties of the tunnel were identified, including the surrounding rock pressure, convergences along tunnel perimeter and safety of primary support and lining structure.Based on the field measured data, the surrounding rock pressure demand for large-span deep tunnel in hard rock is recommended as double peak type in the vertical direction and fold line type was recommended for horizontal pressure. The results suggested that Promojiyfakonov's theory was most close to the monitored value. Specific recommendations were also generated for the use of bolts in tunnel structures.Numerical simulation was used to evaluate the safety of the tunnel and it confirmed that the current design can satisfy the requirement of the current code.展开更多
To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly ...To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed.展开更多
The wind pressure pulse events, among the most important characteristics of wind pressure fluctuations on large-span flat roofs, were investigated by wind tunnel tests in this paper. Incorporating the formation mechan...The wind pressure pulse events, among the most important characteristics of wind pressure fluctuations on large-span flat roofs, were investigated by wind tunnel tests in this paper. Incorporating the formation mechanism of wind pressure pulse events, the peak over threshold method was employed to study properties of this kind of events. The event duration time, the energy contribution, the number of the pulse events, and the distribution of average peak pressure were calculated. Probability density functions of some typical samples in separation region were also given. Results show that the non-Gaussian roof pressure is strong in the flow separation region owing to the wind pressure pulse events. Evaluations of the extreme peak pressures, which can be determined by the peak over threshold method effectively, are important to the design of building cladding.展开更多
Purpose–The microseismic monitoring technique has great advantages on identifying the location,extent and the mechanism of damage process occurring in rock mass.This study aims to analyze distribution characteristics...Purpose–The microseismic monitoring technique has great advantages on identifying the location,extent and the mechanism of damage process occurring in rock mass.This study aims to analyze distribution characteristics and the evolution law of excavation damage zone of surrounding rock based on microseismic monitoring data.Design/methodology/approach–In situ test using microseismic monitoring technique is carried out in the large-span transition tunnel of Badaling Great Wall Station of Beijing-Zhangjiakou high-speed railway.An intelligent microseismic monitoring system is built with symmetry monitoring point layout both on the mountain surface and inside the tunnel to achieve three-dimensional and all-round monitoring results.Findings–Microseismic events can be divided into high density area,medium density area and low density area according to the density distribution of microseismic events.The positions where the cumulative distribution frequencies of microseismic events are 60 and 80%are identified as the boundaries between high and medium density areas and between medium and low density areas,respectively.The high density area of microseismic events is regarded as the high excavation damage zone of surrounding rock,which is affected by the grade of surrounding rock and the span of tunnel.The prediction formulas for the depth of high excavation damage zone of surrounding rock at different tunnel positions are given considering these two parameters.The scale of the average moment magnitude parameters of microseismic events is adopted to describe the damage degree of surrounding rock.The strong positive correlation and multistage characteristics between the depth of excavation damage zone and deformation of surrounding rock are revealed.Based on the depth of high excavation damage zone of surrounding rock,the prestressed anchor cable(rod)is designed,and the safety of anchor cable(rod)design parameters is verified by the deformation results of surrounding rock.Originality/value–The research provides a new method to predict the surrounding rock damage zone of large-span tunnel and also provides a reference basis for design parameters of prestressed anchor cable(rod).展开更多
Hanping tunnel is a control project of national highway 310 Dahejia to Qingshui highway project.It needs to cross a 330kV high-voltage transmission line under the condition of small clear distance,which requires high ...Hanping tunnel is a control project of national highway 310 Dahejia to Qingshui highway project.It needs to cross a 330kV high-voltage transmission line under the condition of small clear distance,which requires high construction requirements.In view of the difficulties such as shallow buried depth of tunnel and small clear distance between tunnel and tower of high-voltage line,multiple excavation blasting method is adopted,and smooth blasting,charge quantity control and damping hole setting are comprehensively used to reduce the impact on the tower and structure of high-voltage line.In order to ensure the smooth progress of the project,the large-scale finite element analysis software is used to simulate the whole excavation project.The influence of the full-section method and the middle partition wall method(CD method)on the surrounding rock and the high-voltage electric tower is compared.It is found that the CD method can effectively control the displacement of the surrounding rock and the tower on it and the uneven settlement.展开更多
This paper presents a novel and precise seismic performance evaluation method for large-span offshore cable-stayed(LSOCS)bridge by considering the strain rate effect of RC materials and the spatial variation effect of...This paper presents a novel and precise seismic performance evaluation method for large-span offshore cable-stayed(LSOCS)bridge by considering the strain rate effect of RC materials and the spatial variation effect of seafloor seismic motions. Threedimensional finite element(FE) model of a LSOCS bridge located in the southeast coast of China is constructed in the ABAQUS platform. The non-uniform ground motions at the offshore site beneath the bridge are stochastically simulated and used as seismic inputs. Moreover, a subroutine for considering the rate-dependent properties of RC materials in a fiber-based beamcolumn element model is developed to account for the strain rate effect of RC materials in the nonlinear time-history analysis.The numerical results indicate that seismic responses and fragilities of the LSOCS bridge are both considerably affected by the non-uniform seafloor seismic motions and strain rate effect. The seismic performance evaluation approach presented in this paper can provide vital support for earthquake resistant design of LSOCS bridges.展开更多
Wind loading is one of the most important loads for controlling the design of large-span roof structures. Equivalent static wind loads, which can generally aim at determining a specific response, are widely used by st...Wind loading is one of the most important loads for controlling the design of large-span roof structures. Equivalent static wind loads, which can generally aim at determining a specific response, are widely used by structural designers. A method for equivalent static wind loads applicable to multi-responses is proposed in this paper. A modified load- response-correlation （LRC） method corresponding to a particular peak response is presented, and the similarity algorithm implemented for the group response is described. The main idea of the algorithm is that two responses can be put into one group if the value of one response is close to that of the other response, when the structure is subjected to equivalent static wind loads aiming at the other response. Based on the modified LRC, the grouping response method is put forward to construct equivalent static wind loading. This technique can simultaneously reproduce peak responses for some grouped responses. To verify its computational accuracy, the method is applied to an actual large-span roof structure. Calculation results show that when the similarity of responses in the same group is high, equivalent static wind loads with high accuracy and reasonable magnitude of equivalent static wind distribution can be achieved.展开更多
Overloads of vehicle may cause damage to bridge structures,and how to assess the safety influence of heavy vehicles crossing the prototype bridge is one of the challenges.In this report,using a large amount of monitor...Overloads of vehicle may cause damage to bridge structures,and how to assess the safety influence of heavy vehicles crossing the prototype bridge is one of the challenges.In this report,using a large amount of monitored data collected from the structural health monitoring system(SHMS)in service of the prototype bridge,of which the bridge type is large-span continuous rigid frame bridge,and adopting FEM simulation technique,we suggested a dynamic reliability assessment method in the report to assess the safety impact of heavy vehicles on the prototype bridge during operation.In the first place,by using the health monitored strain data,of which the selected monitored data time range is before the opening of traffic,the quasi dynamic reliability around the embedded sensor with no traffic load effects is obtained;then,with FEM technology,the FEM simulation model of one main span of the prototype bridge is built by using ANSYS software and then the dynamic reliability when the heavy vehicles crossing the prototype bridge corresponding to the middle-span web plate is comprehensively analyzed and discussed.At last,assuming that the main beam stress state change is in the stage of approximately linear elasticity under heavy vehicle loads impact,the authors got the impact level of heavy vehicles effects on the dynamic reliability of the prototype bridge.Based on a large number of field measured data,the dynamic reliability value calculated by our proposed methodology is more accurate.The method suggested in the paper can do good for not only the traffic management but also the damage analysis of bridges.展开更多
1 Background As the basic principle of the world economy,environment,and social development,sustainable development is the focus of the international community today.In the Olympic Agenda 2020 published by the Interna...1 Background As the basic principle of the world economy,environment,and social development,sustainable development is the focus of the international community today.In the Olympic Agenda 2020 published by the International Olympic Committee(IOC),sustainable development was officially listed as one of the core concepts of the Olympic Games.Since the beginning of the bid,the concept of ctathlete-centered,sustainable and economical”was proposed,which was highly consistent with the idea of the Olympic Agenda 2020.To implement the concept of holding“green”Olympic Games and meet the sustainability requirements of the IOC,the Organizing Committee of Beijing Winter Olympic Games issued a series of documents related to the sustainability of sports venues such as Sustainability Policies for 2022 Beijing Winter Olympic Games and Winter Paralympic Games,and strived to realize the sustainable development of sports venues in the whole life cycle of planning and design stage,construction stage,operation stage,and post-game utilization.展开更多
文摘A steel-concrete composite cable-stayed bridge features integrated steel girders and concrete decks linked by shear connectors to support loads,but stress concentration in wet joints can lead to cracking.In-situ tests were conducted on key sections of steel-concrete composite cable-stayed bridges to analyze the stress-strain evolution of wet joints under environmental factors,constraints,and complex construction processes.The coordinated working performance of the bridge decks was also analyzed.The results indicate that temperature is the key factor affecting the stresses and strains in wet joint concrete.Approximately 7 days after casting the wet joint concrete,the strains at each measurement point of the wet joint are approximately negatively correlated with the temperature change at the measurement point.Different locations within the wet joints have respective impacts,presenting potential weak points.Construction conditions have a certain impact on the stress and strain of the wet joint.The top deck of the steel box girder is not fully bonded to the bottom surface of the wet joints,resulting in a certain strain difference after loading.To further analyze the cooperative working performance of steel box girders and concrete wet joint bridge deck systems,finite element analysis was conducted on composite girder structures.A stiffness calculation method for shear connectors based on numerical simulation was proposed.The results indicate that strain differences can cause interface slip in composite girders.This slip leads to increased deflection of the composite girders and increased tensile stress in the bottom plate of the steel box girders.This study clarifies the stress conditions and factors affecting wet joints during construction,preventing early cracking,and offers precise data for a full bridge finite element model.
基金funded by the Science and Technology Research Program of the Chongqing Municipal Education Commission(grant number KJQN202403002).
文摘The steel tube arch rib in a large-span concrete-filled steel tube arch bridge has a large span and diameter,which also leads to a larger weld seam scale.Large-scale welding seams will inevitably cause more obvious welding residual stress(WRS).For the purpose of studying the influence of WRS from large-scale welding seam on the mechanical properties of steel tube arch rib during arch rib splicing,test research and numerical simulation analysis on the WRS in arch rib splicing based on the Guangxi Pingnan Third Bridge,which is the world’s largest span concrete-filled steel tube arch bridge,were conducted in this paper,and the distribution pattern of WRS at the arch rib splicing joint was obtained.Subsequently,the WRS was introduced into the mechanical performance analysis of joints and structures to analyze its effects.The findings reveal that the distribution of WRS in the arch rib is greatly influenced by the rib plate,and the axial WRS in the heat-affected zone are primarily tensile,while the circumferential WRS are distributed in an alternating pattern of tensile and compressive stresses along the circumferential direction of the main tube.Under the influence of WRS,the ultimate bearing capacity of the joint is reduced by 29.4%,the initial axial stiffness is reduced by 4.32%,and the vertical deformation of the arch rib structure is increased by 4.7%.
基金Project(2023YFC3805700) supported by the National Key Research and Development Program of ChinaProjects(42477166,42277174) supported by the National Natural Science Foundation of China+2 种基金Project(2024JCCXSB01) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(KFJJ24-01M) supported by the State Key Laboratory of Explosion Science and Safety Protection,Beijing Institute of Technology,ChinaProject(HLCX-2024-04) supported by the Open Foundation of Collaborative Innovation Center of Green Development and Ecological Restoration of Mineral Resources,China。
文摘The surrounding rock is prone to large-scale loosening and failure after the excavation of shallow large-span caverns because of the thin overlying strata and large cross-section span.The rational design of bolt support is very important to the safety control of surrounding rock as a common support means.The control mechanism and design method of bolt support for shallow-buried large-span caverns is carried out.The calculation method of bolt prestress and length based on arched failure and collapsed failure mode is established.The influence mechanism of different influencing factors on the bolt prestress and length is clarified.At the same time,the constant resistance energy-absorbing bolt with high strength and high toughness is developed,and the comparative test of mechanical properties is carried out.On this basis,the design method of high prestressed bolt support for shallow-buried large-span caverns is put forward,and the field test is carried out in Qingdao metro station in China.The monitoring results show that the maximum roof settlement is 6.8 mm after the new design method is adopted,and the effective control of the shallow-buried large-span caverns is realized.The research results can provide theoretical and technical support for the safety control of shallow-buried large-span caverns.
基金supported by the National Natural Science Foundation of China(U23A20666)the China National Railway Group Corporation Science and Technology Research and Development Program(N2023G083).
文摘Welded Turnout on Large-span Bridge(WTLB)is a complex multi-layer heterogeneous system and can significantly influence the service performance of High-Speed Railway(HSR).Understanding the coupling dynamic response of the vehicle and WTLB is essential.Previous research did not consider the dynamic behavior of foundations,leading to an underestimation of the vehicle-turnout-foundation coupling dynamic response,particularly when turnouts were laid on large-span bridges.This study proposes a novel modeling method that includes the foundations,to overcome the previous shortcomings by applying a rigid-flexible coupling system.In this approach,the vehicle was modeled as a rigid body sub-model in a Multi-Body Software(MBS),while WTLB was modeled as a flexible bodies sub-model using Finite Element(FE)software.The modal information from the FE model was imported into the MBS software.The two sub-models were coupled by the wheel-rail contact in the MBS environment and then the Vehicle-turnout-bridge Rigid-flexible Coupling Dynamic(VRCD)calculation model was established and it was discovered that the calculation results showed good agreement with the field test data.Through the VRCD model,the safety of the structure,the stability of the vehicle and the comfort of passengers were investigated,as well as several important infrastructure factors.The results demonstrate that this novel method provides accurate calculations and highlights the complex and significant interactions in the vehicle-turnout-bridge system.
基金Projects(41072238,51009133)supported by the National Natural Science Foundation of China
文摘The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock.The development of a new type of foam concrete which has the property of high compressibility and low ductility was introduced.And it was made as filling material of reserved deformation layer between the first lining and the second lining used in large-span soft rock tunnel.The effect of the new type of foam concrete was simulated as filling material of reserved deformation layer using numerical simulation.Through the comparison with the common large-span soft rock tunnel,the vault settlement and surrounding convergence are reduced by about 61% and 45%,respectively,after creep of 100 a.And in the second lining,the plastic zone reduces apparently and the maximum equivalent plastic strain decreases relatively.So,it can be found that the application of the new type of foam concrete as the filling material of reserved deformation layer can relieve the excessive force in second lining induced by rock creep,reduce its deformation and improve the stability of tunnel.
基金Financial supports are from the National Natural Science Foun-dation of China (No. 50874104)the Scientific Research Indus-trialization Project of Jiangsu Universities (No. JH07-023)
文摘In order to study the distribution laws and types of plastic zone of surrounding rock in large-span roadway, we analyzed the distribution laws with different spans and lateral pressures using FLAC3D numerical calcu- lation software. Based on the roadway support difficulty and distribution laws of the plastic zone of sur- rounding rock, we defined the large-span roadway and classified the types of large-span rectangular roadways. As a result, the distribution laws of the plastic zone on surrounding rock in a rectangular roadway with different spans and lateral pressures were obtained. The results show that the area of the plastic zone on surrounding rock increased with the increase of the spans and lateral pressures, and the plastic zone was symmetrical to the center line of roadway. At λ=0.5, 1.0, 1.5, and 2.0, the plastic zone presented ＂addle- shape＂ distribution, ＂ellipse＂ distribution, ＂thin and high＂ distribution and ＂inverse trapezium＂ distribu- tion, respectively. In addition, we classified the roadways into four types according to the different lateral pressures and spans, including small-span, moderate-span, large-span and extreme-large-span roadways.
基金sponsored by projects (Grant Nos. 50978172, 51078318) of the National Natural Science Foundation of ChinaProject (Grant No. 10-0667) supposed by the New Century Excellent Talents in University
文摘A section of the Nanliang high speed railway tunnel on Shijiazhuang-Taiyuan high-speed passenger railway line in China was instrumented and studied for its mechanical properties and performances. The cross section for the tunnel was300 m2and is classified as the largest cross section for railway tunnels in China. Through in situ experimental studies, mechanistic properties of the tunnel were identified, including the surrounding rock pressure, convergences along tunnel perimeter and safety of primary support and lining structure.Based on the field measured data, the surrounding rock pressure demand for large-span deep tunnel in hard rock is recommended as double peak type in the vertical direction and fold line type was recommended for horizontal pressure. The results suggested that Promojiyfakonov's theory was most close to the monitored value. Specific recommendations were also generated for the use of bolts in tunnel structures.Numerical simulation was used to evaluate the safety of the tunnel and it confirmed that the current design can satisfy the requirement of the current code.
基金National Natural Science Foundation of China under Grant Nos.51738007,51808099the Fundamental Research Funds for the Central Universities under Grant No.DUT20RC(3)005。
文摘To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50708030 and 90815021)
文摘The wind pressure pulse events, among the most important characteristics of wind pressure fluctuations on large-span flat roofs, were investigated by wind tunnel tests in this paper. Incorporating the formation mechanism of wind pressure pulse events, the peak over threshold method was employed to study properties of this kind of events. The event duration time, the energy contribution, the number of the pulse events, and the distribution of average peak pressure were calculated. Probability density functions of some typical samples in separation region were also given. Results show that the non-Gaussian roof pressure is strong in the flow separation region owing to the wind pressure pulse events. Evaluations of the extreme peak pressures, which can be determined by the peak over threshold method effectively, are important to the design of building cladding.
基金supported by the Fundamental Research Funds for Chinese National Natural Science Foundation under Grant 51678035National Key Research and Development Programs of China under Grant 2017YFC0805401China Railway Corporation Research and Development Program of Science and Technology under Grant 2014004-C.
文摘Purpose–The microseismic monitoring technique has great advantages on identifying the location,extent and the mechanism of damage process occurring in rock mass.This study aims to analyze distribution characteristics and the evolution law of excavation damage zone of surrounding rock based on microseismic monitoring data.Design/methodology/approach–In situ test using microseismic monitoring technique is carried out in the large-span transition tunnel of Badaling Great Wall Station of Beijing-Zhangjiakou high-speed railway.An intelligent microseismic monitoring system is built with symmetry monitoring point layout both on the mountain surface and inside the tunnel to achieve three-dimensional and all-round monitoring results.Findings–Microseismic events can be divided into high density area,medium density area and low density area according to the density distribution of microseismic events.The positions where the cumulative distribution frequencies of microseismic events are 60 and 80%are identified as the boundaries between high and medium density areas and between medium and low density areas,respectively.The high density area of microseismic events is regarded as the high excavation damage zone of surrounding rock,which is affected by the grade of surrounding rock and the span of tunnel.The prediction formulas for the depth of high excavation damage zone of surrounding rock at different tunnel positions are given considering these two parameters.The scale of the average moment magnitude parameters of microseismic events is adopted to describe the damage degree of surrounding rock.The strong positive correlation and multistage characteristics between the depth of excavation damage zone and deformation of surrounding rock are revealed.Based on the depth of high excavation damage zone of surrounding rock,the prestressed anchor cable(rod)is designed,and the safety of anchor cable(rod)design parameters is verified by the deformation results of surrounding rock.Originality/value–The research provides a new method to predict the surrounding rock damage zone of large-span tunnel and also provides a reference basis for design parameters of prestressed anchor cable(rod).
基金National Key Research and Development Program(Research on Key Technologies for the Operation and Maintenance of Typical Urban Traffic Infrastructure Safety)(2017YFC0806000)Chinese Academy of Engineering Institute-Local Cooperation Project(2019-CQ-ZD-4)。
文摘Hanping tunnel is a control project of national highway 310 Dahejia to Qingshui highway project.It needs to cross a 330kV high-voltage transmission line under the condition of small clear distance,which requires high construction requirements.In view of the difficulties such as shallow buried depth of tunnel and small clear distance between tunnel and tower of high-voltage line,multiple excavation blasting method is adopted,and smooth blasting,charge quantity control and damping hole setting are comprehensively used to reduce the impact on the tower and structure of high-voltage line.In order to ensure the smooth progress of the project,the large-scale finite element analysis software is used to simulate the whole excavation project.The influence of the full-section method and the middle partition wall method(CD method)on the surrounding rock and the high-voltage electric tower is compared.It is found that the CD method can effectively control the displacement of the surrounding rock and the tower on it and the uneven settlement.
基金supported by the National Natural Science Foundation of China (Grant No. 51808099)the Fundamental Research Funds for the Central Universities (Grant No. DUT20RC(3)005)。
文摘This paper presents a novel and precise seismic performance evaluation method for large-span offshore cable-stayed(LSOCS)bridge by considering the strain rate effect of RC materials and the spatial variation effect of seafloor seismic motions. Threedimensional finite element(FE) model of a LSOCS bridge located in the southeast coast of China is constructed in the ABAQUS platform. The non-uniform ground motions at the offshore site beneath the bridge are stochastically simulated and used as seismic inputs. Moreover, a subroutine for considering the rate-dependent properties of RC materials in a fiber-based beamcolumn element model is developed to account for the strain rate effect of RC materials in the nonlinear time-history analysis.The numerical results indicate that seismic responses and fragilities of the LSOCS bridge are both considerably affected by the non-uniform seafloor seismic motions and strain rate effect. The seismic performance evaluation approach presented in this paper can provide vital support for earthquake resistant design of LSOCS bridges.
基金Ministry of Science and Technology of China Under Grant No.SLDRCE10-B-04the National Natural Science Foundation Under Grant No.50621062
文摘Wind loading is one of the most important loads for controlling the design of large-span roof structures. Equivalent static wind loads, which can generally aim at determining a specific response, are widely used by structural designers. A method for equivalent static wind loads applicable to multi-responses is proposed in this paper. A modified load- response-correlation （LRC） method corresponding to a particular peak response is presented, and the similarity algorithm implemented for the group response is described. The main idea of the algorithm is that two responses can be put into one group if the value of one response is close to that of the other response, when the structure is subjected to equivalent static wind loads aiming at the other response. Based on the modified LRC, the grouping response method is put forward to construct equivalent static wind loading. This technique can simultaneously reproduce peak responses for some grouped responses. To verify its computational accuracy, the method is applied to an actual large-span roof structure. Calculation results show that when the similarity of responses in the same group is high, equivalent static wind loads with high accuracy and reasonable magnitude of equivalent static wind distribution can be achieved.
文摘Overloads of vehicle may cause damage to bridge structures,and how to assess the safety influence of heavy vehicles crossing the prototype bridge is one of the challenges.In this report,using a large amount of monitored data collected from the structural health monitoring system(SHMS)in service of the prototype bridge,of which the bridge type is large-span continuous rigid frame bridge,and adopting FEM simulation technique,we suggested a dynamic reliability assessment method in the report to assess the safety impact of heavy vehicles on the prototype bridge during operation.In the first place,by using the health monitored strain data,of which the selected monitored data time range is before the opening of traffic,the quasi dynamic reliability around the embedded sensor with no traffic load effects is obtained;then,with FEM technology,the FEM simulation model of one main span of the prototype bridge is built by using ANSYS software and then the dynamic reliability when the heavy vehicles crossing the prototype bridge corresponding to the middle-span web plate is comprehensively analyzed and discussed.At last,assuming that the main beam stress state change is in the stage of approximately linear elasticity under heavy vehicle loads impact,the authors got the impact level of heavy vehicles effects on the dynamic reliability of the prototype bridge.Based on a large number of field measured data,the dynamic reliability value calculated by our proposed methodology is more accurate.The method suggested in the paper can do good for not only the traffic management but also the damage analysis of bridges.
文摘1 Background As the basic principle of the world economy,environment,and social development,sustainable development is the focus of the international community today.In the Olympic Agenda 2020 published by the International Olympic Committee(IOC),sustainable development was officially listed as one of the core concepts of the Olympic Games.Since the beginning of the bid,the concept of ctathlete-centered,sustainable and economical”was proposed,which was highly consistent with the idea of the Olympic Agenda 2020.To implement the concept of holding“green”Olympic Games and meet the sustainability requirements of the IOC,the Organizing Committee of Beijing Winter Olympic Games issued a series of documents related to the sustainability of sports venues such as Sustainability Policies for 2022 Beijing Winter Olympic Games and Winter Paralympic Games,and strived to realize the sustainable development of sports venues in the whole life cycle of planning and design stage,construction stage,operation stage,and post-game utilization.
