To get the probability of long span bridges under the influence of external random factors, the Monte Carlo method using Latin hypercube sampling is applied. Combined with the condition assessment system on Runyang Su...To get the probability of long span bridges under the influence of external random factors, the Monte Carlo method using Latin hypercube sampling is applied. Combined with the condition assessment system on Runyang Suspension Bridge, which is the longest suspension bridge in China, the structural probabilities in normal and damaged situations are calculated with the external random factors considered including environmental temperature, wind load, load of vehicles, etc. The main assessment items contain the maximal vertical displacement of girder, the maximal stress of cables, the maximal horizontal displacement of towers etc. Finally, the probabilities and their cumulative distribution functions are provided. The analysis results can be plotted on line in a clear and vivid way, so the efficiency of assessment is increased and the decision-making of maintenance is more objective and accurate.展开更多
Health state of shield tunnels is one of the most important parameters for structure maintenance.Usually,the shield tunnel is extremely long in longitude direction and composed by many segments.It is difficult to quan...Health state of shield tunnels is one of the most important parameters for structure maintenance.Usually,the shield tunnel is extremely long in longitude direction and composed by many segments.It is difficult to quantify the relationship between the structure damage state and shield tunnel structure deformation by the model test because of unpredictable effects of different scales between model test and prototype tunnel structure.Here,an in-situ monitoring project was conducted to study the excavation induced shield tunnel structure damage,which could be considered a prototype test on the tunnel deformation.The disaster performance of tunnel leakage,segment crack,segment dislocation and segment block drop-off during longitude deformation and cross-section ovality developments was analyzed.The results indicate that instead of the longitude deformation,the ovality value has the strongest correlation to the rest disease performance,which could be used as the assessment index of the tunnel health.For this tunnel,it is in health state when the ovality is less than 0.5%,and the serious damage could be found when the ovality value is higher than 0.77%.The research results provide valuable reference to shield tunnel health assessment and help complete the standard of shield tunnel construction.展开更多
This paper introduces a new concept of ＂State Representation Methodology （SRM）＂ which is a kind of bridge condition assessment method for structural health monitoring system （SHM）. There are many methods for sys...This paper introduces a new concept of ＂State Representation Methodology （SRM）＂ which is a kind of bridge condition assessment method for structural health monitoring system （SHM）. There are many methods for system identification from the simplicity comparison of damage index to the complicated statistical pattern recognition algorithms in SHM. In these methods, modal analysis and parameters identification or many defined indices are common-used for extracting the dynamic or static characteristics of a system. However, there is a common problem： due to the complexity of a large size system with high-order nonlinear characteristics and severe environment interference, it is impossible to extract and quantify exactly these modal parameters or system parameters or indices as the feature vectors of a system in damage detection in an easy way. The SRM considered a more general theory for the non-parametric description of system state.展开更多
Following recent rapid developments in tunnel engineering in China,the heavy structural maintenance work of the future is likely to pose a great challenge.Newly developed vibration-based health assessment and monitori...Following recent rapid developments in tunnel engineering in China,the heavy structural maintenance work of the future is likely to pose a great challenge.Newly developed vibration-based health assessment and monitoring methods offer good prospects for large-scale structural monitoring,hidden surface detection and disease pre-judgment.However,because the dynamic properties of tunnels are sensitive to the coupling and damping effects of the surrounding soil,there is little relevant research on tunnel structures.Using the PiP(pipe in pipe)model,the intrinsic tunnel modes and their response characteristics are investigated in this paper,and the degree to which the identification of these characteristics is influenced by mode superposition and the soil coupling effect are also considered.The response features of these flexible wave modes are found to be barely recognizable in a tunnel-soil coupled system,while the phase velocity of the torsional wave can be determined by combining phase spectrum analysis and the HHT(Hilbert-Huang transformation)method.A new structural health assessment method based on the torsional wave speed is therefore proposed.In this method,the torsional wave speed is used to determine the tunnel structure’s global stiffness based on a newly developed dispersion algorithm.The calculated stiffness is then used to evaluate the tunnel’s structural service status.A field test was also carried out at a newly built tunnel to validate the proposed method;the tunnel structure’s Young’s modulus was obtained and was very close to the designed value.This indicates that this method is an effective way to assess tunnel service conditions,and also provides a theoretical basis for future applications to health assessment of shield tunnels.展开更多
The "Structural Health Monitoring" is a project supported by National Natural Science Foundation for Distinguished Young Scholars of China(Grant No.50725828).To meet the urgent requirements of analysis and a...The "Structural Health Monitoring" is a project supported by National Natural Science Foundation for Distinguished Young Scholars of China(Grant No.50725828).To meet the urgent requirements of analysis and assessment of mass monitoring data of bridge environmental actions and structural responses,the monitoring of environmental actions and action effect modeling methods,dynamic performance monitoring and early warning methods,condition assessment and operation maintenance methods of key members are systematically studied in close combination with structural characteristics of long-span cable-stayed bridges and suspension bridges.The paper reports the progress of the project as follows.(1) The environmental action modeling methods of long-span bridges are established based on monitoring data of temperature,sustained wind and typhoon.The action effect modeling methods are further developed in combination with the multi-scale baseline finite element modeling method for long-span bridges.(2) The identification methods of global dynamic characteristics and internal forces of cables and hangers for long-span cable-stayed bridges and suspension bridges are proposed using the vibration monitoring data,on the basis of which the condition monitoring and early warning methods of bridges are developed using the environmental-condition-normalization technique.(3) The analysis methods for fatigue loading effect of welded details of steel box girder,temperature and traffic loading effect of expansion joint are presented based on long-term monitoring data of strain and beam-end displacement,on the basis of which the service performance assessment and remaining life prediction methods are developed.展开更多
文摘To get the probability of long span bridges under the influence of external random factors, the Monte Carlo method using Latin hypercube sampling is applied. Combined with the condition assessment system on Runyang Suspension Bridge, which is the longest suspension bridge in China, the structural probabilities in normal and damaged situations are calculated with the external random factors considered including environmental temperature, wind load, load of vehicles, etc. The main assessment items contain the maximal vertical displacement of girder, the maximal stress of cables, the maximal horizontal displacement of towers etc. Finally, the probabilities and their cumulative distribution functions are provided. The analysis results can be plotted on line in a clear and vivid way, so the efficiency of assessment is increased and the decision-making of maintenance is more objective and accurate.
基金Projects(BK20150337,BK20140845,BK20140844)supported by the Natural Science Foundation of Jiangsu Province,ChinaProject(2015Y04)supported by the Transportation Science and Technology Project of Jiangsu Province,China+1 种基金Project(41504081)supported by the National Natural Science Foundation of ChinaProjects(2014M561567,2016T90416)supported by the China Postdoctoral Science Foundation
文摘Health state of shield tunnels is one of the most important parameters for structure maintenance.Usually,the shield tunnel is extremely long in longitude direction and composed by many segments.It is difficult to quantify the relationship between the structure damage state and shield tunnel structure deformation by the model test because of unpredictable effects of different scales between model test and prototype tunnel structure.Here,an in-situ monitoring project was conducted to study the excavation induced shield tunnel structure damage,which could be considered a prototype test on the tunnel deformation.The disaster performance of tunnel leakage,segment crack,segment dislocation and segment block drop-off during longitude deformation and cross-section ovality developments was analyzed.The results indicate that instead of the longitude deformation,the ovality value has the strongest correlation to the rest disease performance,which could be used as the assessment index of the tunnel health.For this tunnel,it is in health state when the ovality is less than 0.5%,and the serious damage could be found when the ovality value is higher than 0.77%.The research results provide valuable reference to shield tunnel health assessment and help complete the standard of shield tunnel construction.
文摘This paper introduces a new concept of ＂State Representation Methodology （SRM）＂ which is a kind of bridge condition assessment method for structural health monitoring system （SHM）. There are many methods for system identification from the simplicity comparison of damage index to the complicated statistical pattern recognition algorithms in SHM. In these methods, modal analysis and parameters identification or many defined indices are common-used for extracting the dynamic or static characteristics of a system. However, there is a common problem： due to the complexity of a large size system with high-order nonlinear characteristics and severe environment interference, it is impossible to extract and quantify exactly these modal parameters or system parameters or indices as the feature vectors of a system in damage detection in an easy way. The SRM considered a more general theory for the non-parametric description of system state.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2011CB013803)the National Natural Science Foundation of China(Grant No.41372273)the Shanghai Science and Technology Development Funds(Grant Nos.12231200900,13231200102)
文摘Following recent rapid developments in tunnel engineering in China,the heavy structural maintenance work of the future is likely to pose a great challenge.Newly developed vibration-based health assessment and monitoring methods offer good prospects for large-scale structural monitoring,hidden surface detection and disease pre-judgment.However,because the dynamic properties of tunnels are sensitive to the coupling and damping effects of the surrounding soil,there is little relevant research on tunnel structures.Using the PiP(pipe in pipe)model,the intrinsic tunnel modes and their response characteristics are investigated in this paper,and the degree to which the identification of these characteristics is influenced by mode superposition and the soil coupling effect are also considered.The response features of these flexible wave modes are found to be barely recognizable in a tunnel-soil coupled system,while the phase velocity of the torsional wave can be determined by combining phase spectrum analysis and the HHT(Hilbert-Huang transformation)method.A new structural health assessment method based on the torsional wave speed is therefore proposed.In this method,the torsional wave speed is used to determine the tunnel structure’s global stiffness based on a newly developed dispersion algorithm.The calculated stiffness is then used to evaluate the tunnel’s structural service status.A field test was also carried out at a newly built tunnel to validate the proposed method;the tunnel structure’s Young’s modulus was obtained and was very close to the designed value.This indicates that this method is an effective way to assess tunnel service conditions,and also provides a theoretical basis for future applications to health assessment of shield tunnels.
基金supported by the National Natural Science Foundation for Distinguished Young Scholars of China (Grant No. 50725828)
文摘The "Structural Health Monitoring" is a project supported by National Natural Science Foundation for Distinguished Young Scholars of China(Grant No.50725828).To meet the urgent requirements of analysis and assessment of mass monitoring data of bridge environmental actions and structural responses,the monitoring of environmental actions and action effect modeling methods,dynamic performance monitoring and early warning methods,condition assessment and operation maintenance methods of key members are systematically studied in close combination with structural characteristics of long-span cable-stayed bridges and suspension bridges.The paper reports the progress of the project as follows.(1) The environmental action modeling methods of long-span bridges are established based on monitoring data of temperature,sustained wind and typhoon.The action effect modeling methods are further developed in combination with the multi-scale baseline finite element modeling method for long-span bridges.(2) The identification methods of global dynamic characteristics and internal forces of cables and hangers for long-span cable-stayed bridges and suspension bridges are proposed using the vibration monitoring data,on the basis of which the condition monitoring and early warning methods of bridges are developed using the environmental-condition-normalization technique.(3) The analysis methods for fatigue loading effect of welded details of steel box girder,temperature and traffic loading effect of expansion joint are presented based on long-term monitoring data of strain and beam-end displacement,on the basis of which the service performance assessment and remaining life prediction methods are developed.
