The work presented in this paper aims at investigating the ability of acoustic noise correlation technique for railway infrastructure health monitoring. The principle of this technique is based on impulse responses re...The work presented in this paper aims at investigating the ability of acoustic noise correlation technique for railway infrastructure health monitoring. The principle of this technique is based on impulse responses reconstruction by correlation of random noise propagated in the medium. Since wheel-rail interaction constitutes a source of such noise, correlation technique could be convenient for detection of rail defects using only passive sensors. Experiments have been carried out on a 2 m-long rail sample. Acoustic noise is generated in the sample at several positions. Direct comparison between an active emission-reception response and the estimated noise correlation function has confirmed the validity of the equivalence relation between them. The quality of the reconstruction is shown to be strongly related to the spatial distribution of the noise sources. High sensitivity of the noise-correlation functions to a local defect on the rail is also demonstrated. However, interpretation of the defect signature is more ambiguous than when using classical active responses. Application of a spatiotemporal Fourier transform on data recorded with variable sensor-defect distances has allowed overcoming this ambiguity.展开更多
Fiber Bragg grating (FBG) based sensors offer important advantages over traditional instrumentation with regards to real-time structural health monitoring (SHM) of composite materials and structures in recent years. F...Fiber Bragg grating (FBG) based sensors offer important advantages over traditional instrumentation with regards to real-time structural health monitoring (SHM) of composite materials and structures in recent years. FBG sensors, integrated into existing structures or embedded into new ones, have played a major role in assessing the safety and integrity of engineering structures. In this paper, a review on the latest research of the FBG-based SHM technique for composite field is presented. Firstly, the FBG sensing principle is briefly discussed and FBG and several other optical fiber sensors (OFSs) for SHM are performance-compared. Then, several examples of the use of FBG sensors in composite SHM are illustrated, including those from the field of cure monitoring, civil engineering, aviation, aerospace, marine and offshore platform. Finally, some existing problems are pointed out and some proposals for further researches are provided.展开更多
This paper deals with an improved bonding approach of surface-bonded fiber Bragg grating (FBG) sensors for airship envelope structural health monitoring (SHM) under the strain transfer theory. A theoretical formula is...This paper deals with an improved bonding approach of surface-bonded fiber Bragg grating (FBG) sensors for airship envelope structural health monitoring (SHM) under the strain transfer theory. A theoretical formula is derived from the proposed model to predict the strain transfer relationship between the airship envelope and fiber core. Then theoretical predictions are validated by numerical analysis using the finite element method (FEM). Finally, on the basis of the theoretical approach and numerical validation, parameters that influence the strain transfer rate from the airship envelope to fiber core and the ratio of effective sensing length are analyzed, and some meaningful conclusions are provided.展开更多
It is becoming an important social problem to make maintenance and rehabilitation of existing short and medium span(10-20 m)bridges because there are a huge amount of short and medium span bridges in service in the wo...It is becoming an important social problem to make maintenance and rehabilitation of existing short and medium span(10-20 m)bridges because there are a huge amount of short and medium span bridges in service in the world.The kernel of such bridge management is to develop a method of safety(condition)assessment on items which include remaining life and load carrying capacity.Bridge health monitoring using information technology and sensors is capable of providing more accurate knowledge of bridge performance than traditional strategies.The aim of this paper is to introduce a state-of-the-art on not only a rational bridge health monitoring system incorporating with the information and communication technologies for lifetime management of existing short and medium span bridges but also a continuous data collecting system designed for bridge health monitoring of mainly short and medium span bridges.In this paper,although there are some useful monitoring methods for short and medium span bridges based on the qualitative or quantitative information,mainly two advanced structural health monitoring systems are described to review and analyse the potential of utilizing the long term health monitoring in safety assessment and management issues for short and medium span bridge.The first is a special designed mobile in-situ loading device(vehicle)for short and medium span road bridges to assess the structural safety(performance)and derive optimal strategies for maintenance using reliability based method.The second is a long term health monitoring method by using the public buses as part of a public transit system(called bus monitoring system)to be applied mainly to short and medium span bridges,along with safety indices,namely,"characteristic deflection"which is relatively free from the influence of dynamic disturbances due to such factors as the roughness of the road surface,and a structural anomaly parameter.展开更多
建筑物的共振频率是结构健康监测(Structural Health Monitoring,SHM)的重要指标。人们通常认为该指标受地震事件或环境变化影响最大,但很少有人讨论人类活动对它的影响。为了对福建省防灾减灾中心大楼进行结构健康监测,并分析人类活动...建筑物的共振频率是结构健康监测(Structural Health Monitoring,SHM)的重要指标。人们通常认为该指标受地震事件或环境变化影响最大,但很少有人讨论人类活动对它的影响。为了对福建省防灾减灾中心大楼进行结构健康监测,并分析人类活动对建筑物共振频率的影响,通过分析地震背景噪声数据,采用水平垂直谱比法(Horizontal to Vertical Spectral Ratio,HVSR),得出中心大楼地基的场地放大频带为1.5~3.5 Hz的多峰宽频带,大楼顶层的共振放大频带为以1.4 Hz左右为中心的单峰频带。大楼共振放大和场地效应处于同一频带,但放大程度是场地的近10倍。同时,顶层的HVSR谱幅值呈现出与人类活动有关的日变化、周变化特征,即春节、周末和夜间幅值小,工作日的白天幅值大。大楼的共振频率变化呈突变和渐变两个过程。其中,突变表现为:工作日白天,建筑物共振频率集中在1.36 Hz附近,其他时间集中在1.48 Hz附近,是被人类活动影响的体现;渐变表现为:在每天夜间、春节和大部分周末,中心大楼的共振频率不断上升,展现了建筑物共振频率恢复的动态过程。本研究的结果有助于建筑结构健康监测中考虑人类活动对共振频率的影响及共振频率的恢复,并为类似建筑物的健康监测提供参考。展开更多
文摘The work presented in this paper aims at investigating the ability of acoustic noise correlation technique for railway infrastructure health monitoring. The principle of this technique is based on impulse responses reconstruction by correlation of random noise propagated in the medium. Since wheel-rail interaction constitutes a source of such noise, correlation technique could be convenient for detection of rail defects using only passive sensors. Experiments have been carried out on a 2 m-long rail sample. Acoustic noise is generated in the sample at several positions. Direct comparison between an active emission-reception response and the estimated noise correlation function has confirmed the validity of the equivalence relation between them. The quality of the reconstruction is shown to be strongly related to the spatial distribution of the noise sources. High sensitivity of the noise-correlation functions to a local defect on the rail is also demonstrated. However, interpretation of the defect signature is more ambiguous than when using classical active responses. Application of a spatiotemporal Fourier transform on data recorded with variable sensor-defect distances has allowed overcoming this ambiguity.
基金the National High Technology Research and Development Program (863) of China(No. 2011AA7052011)the National Natural Science Foundation of China (No. 51205253)
文摘Fiber Bragg grating (FBG) based sensors offer important advantages over traditional instrumentation with regards to real-time structural health monitoring (SHM) of composite materials and structures in recent years. FBG sensors, integrated into existing structures or embedded into new ones, have played a major role in assessing the safety and integrity of engineering structures. In this paper, a review on the latest research of the FBG-based SHM technique for composite field is presented. Firstly, the FBG sensing principle is briefly discussed and FBG and several other optical fiber sensors (OFSs) for SHM are performance-compared. Then, several examples of the use of FBG sensors in composite SHM are illustrated, including those from the field of cure monitoring, civil engineering, aviation, aerospace, marine and offshore platform. Finally, some existing problems are pointed out and some proposals for further researches are provided.
基金Project (No. 2011AA7052011) supported by the National High-Tech R&D (863) Program of China
文摘This paper deals with an improved bonding approach of surface-bonded fiber Bragg grating (FBG) sensors for airship envelope structural health monitoring (SHM) under the strain transfer theory. A theoretical formula is derived from the proposed model to predict the strain transfer relationship between the airship envelope and fiber core. Then theoretical predictions are validated by numerical analysis using the finite element method (FEM). Finally, on the basis of the theoretical approach and numerical validation, parameters that influence the strain transfer rate from the airship envelope to fiber core and the ratio of effective sensing length are analyzed, and some meaningful conclusions are provided.
文摘It is becoming an important social problem to make maintenance and rehabilitation of existing short and medium span(10-20 m)bridges because there are a huge amount of short and medium span bridges in service in the world.The kernel of such bridge management is to develop a method of safety(condition)assessment on items which include remaining life and load carrying capacity.Bridge health monitoring using information technology and sensors is capable of providing more accurate knowledge of bridge performance than traditional strategies.The aim of this paper is to introduce a state-of-the-art on not only a rational bridge health monitoring system incorporating with the information and communication technologies for lifetime management of existing short and medium span bridges but also a continuous data collecting system designed for bridge health monitoring of mainly short and medium span bridges.In this paper,although there are some useful monitoring methods for short and medium span bridges based on the qualitative or quantitative information,mainly two advanced structural health monitoring systems are described to review and analyse the potential of utilizing the long term health monitoring in safety assessment and management issues for short and medium span bridge.The first is a special designed mobile in-situ loading device(vehicle)for short and medium span road bridges to assess the structural safety(performance)and derive optimal strategies for maintenance using reliability based method.The second is a long term health monitoring method by using the public buses as part of a public transit system(called bus monitoring system)to be applied mainly to short and medium span bridges,along with safety indices,namely,"characteristic deflection"which is relatively free from the influence of dynamic disturbances due to such factors as the roughness of the road surface,and a structural anomaly parameter.
