Computer vision for SHM of civil infrastructure: From dynamic response measurement to damage detection – A review

In the last two decades, a significant number of innovative sensing systems based on optical fiber sensors have been exploited in the engineering community due to their inherent distinctive advantages such as small size, light weight, immunity to electromagnetic interference (EMI) and corrosion, and embedding capability. A lot of optical fiber sensor-based monitoring systems have been developed for continuous measurement and real-time assessment of diversified engineering structures such as bridges, buildings, tunnels, pipelines, wind turbines, railway infrastructure, and geotechnical structures. The purpose of this review article is devoted to presenting a summary of the basic principles of various optical fiber sensors, innovation in sensing and computational methodologies, development of novel optical fiber sensors, and the practical application status of the optical fiber sensing technology in structural health monitoring (SHM) of civil infrastructure.

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Structural health monitoring of civil infrastructure using optical fiber sensing technology: a comprehensive review.

Accurate measurement and monitoring of vibration characteristics is critical for proper detection of the location and severity of damage. However, experimentally measured modal properties are inevitably corrupted by measurement noise and errors, which could render most vibration-based structural damage identification algorithms unreliable for civil structural health monitoring (SHM). This article, through computer simulation and experimental investigation of a simply supported beam, comparatively evaluates the performance of these techniques for practical civil SHM by using displacement modes from accelerometers and long-gage distributed strain measurements. Most of all the techniques proved unreliable for damage identification using noisy measurements from accelerometers, while successful with distributed strain measurements. The findings reveal that long-gage distributed strain measurements are much more efficient choice over the traditional measurement techniques for reliable civil SHM. It may therefor...

Assessment of Vibration-based Damage Identification Methods Using Displacement and Distributed Strain Measurements

This article describes how cracks may develop and the modal shapes and frequencies of the cracked structure may change accordingly when the structure is subjected to dynamic or static loads. Based on this fact, a new method is proposed to locate beam cracks and to estimate their depths. The fault-induced modal shape and frequency changes of cracked structures are taken into account in order to construct a new hybrid crack detection method. The method includes two steps: crack localization and depth estimation. The locations of the cracks are determined by applying the wavelet transform to the modal shape. Using the measured natural frequencies as inputs, the depths of the cracks are estimated from a database established by wavelet finite element method. The effectiveness of the proposed hybrid two-step method is demonstrated by numerical simulation and experimental investigation of a cantilever beam with two cracks. The analyses presented in this article also indicated that the proposed method performed reasonably well at certain level of noise.

Wavelet-Based Detection of Beam Cracks Using Modal Shape and Frequency Measurements

The optimal decisions to maintain or improve the reliability and functionality of structures and infrastructure systems can only be achieved through proper integrated management planning in a life-cycle comprehensive framework. Structure and Infrastructure Engineering (SIE) is an international journal dedicated to recent advances inmaintenance, management, and life-cycle performance of a wide range of infrastructures. The purpose of this article is to provide a brief review of the recent research accomplishments in the field of design, maintenance, life-cycle management, and optimisation of structures and infrastructures reported in papers published in SIE during the period 2005–2011. The papers are categorised under main topics and very briefly discussed.

Maintenance, management, life-cycle design and performance of structures and infrastructures: a brief review

The essence of structural health monitoring (SHM) requires an innovative sensing system similar to a human nervous system throughout the whole body to catch comprehensive information without losing structural integrity. In a recent research by the authors, an integrated structural assessment strategy based on distributed strain sensing technologies is proposed [1], which has been dedicated to utilize the strain distribution throughout the full or some partial areas of structures to detect the arbitrary and unforeseen damage. To implement such strategy, a typical distributed fiber optic sensing system is developed by extending the gage length of fiber Bragg grating (FBG) and then arranging the long-gage FBG sensors in series. This article summarizes the packaging design and manufacture method of such long-gage FBG sensors and verifies the performance of the developed sensors and the distributed sensing system by using a series connection of long-gage FBG sensors. Combined with the practical application in ...

Development of Distributed Long-gage Fiber Optic Sensing System for Structural Health Monitoring

The concept of distributed strain sensing techniques has been proposed in a recent research by the authors, which had been dedicated to utilize the strain distributions throughout the full or some partial areas of structures to detect the arbitrary and unforeseen damage. Based on the distributed long-gage fiber optic sensors, a two-level strategy is proposed in this study for damage detection in flexural structures using modal parameters extracted from dynamic macro-strain responses. Modal macro-strain vector (MMSV), similar to the mode shape from acceleration measurements, is utilized to construct damage evaluating indexes for Level 1 damage locating with no need for a detailed analytical model. Hereto, the damaged area with a space resolution of the gage lengths of fiber optic sensors can be detected and the unknown parameters to be identified are greatly reduced into the damaged domain. Then based on the concept of FE model updating, natural frequencies that present high accuracy and precision in pract...

Two-level Damage Detection Strategy Based on Modal Parameters from Distributed Dynamic Macro-strain Measurements

In a recent study by the authors, an advanced structural health monitoring (SHM) strategy based on distributed fiber optic sensing techniques has been proposed to utilize the strain responses throughout the full or some partial areas of structures to detect the arbitrary and unforeseen damages As one of the essential components, a two-level scheme based on modal parameters from distributed dynamic macro-strain responses has been developed for damage locating and quantifying This work further investigates the superiority and some concerns of using distributed long-gage fiber optic sensing technique for vibration based SHM through a theoretical modal analysis on the dynamic macro-strain distribution Modal testing is also carried out to verify the performance of macro-strain frequency response function (FRF) and identify the modal parameters including resonant frequency, damping ratio, and modal macro-strain vector (MMSV) From the SHM point of view, their applications are summarized finally

Modal Analysis on Macro-strain Measurements from Distributed Long-gage Fiber Optic Sensors:

In this article, a technique is proposed to detect damage in structures from measurements taken under different environmental and operational conditions. The method is based on the regression analysis of the features extracted from the vibration measurement. Macro strain was chosen as the selected feature to be measured using the long-gage distributed fiber Bragg grating (FBG) sensors. Features extracted from the measurements on an intact structure were used to construct a reference model for damage identification. Damage was identified by comparing the slope of the regression line of the subsequent measurements to its counterpart of the reference model. Experimental results show that the extracted features were very consistent. The proposed method was demonstrated and validated using noise-polluted numerical simulation data from two different types of structures, a bridge girder and a plane frame, as well as experimental results from a steel beam with different damage scenarios under changing environment...

A Nonphysics-based Approach for Vibration-based Structural Health Monitoring under Changing Environmental Conditions

In our previous study, a distributed long-gauge fibre optic sensing system (with the ability to obtain effective average strain, or macro-strain, distributions) for practical adaptation in civil structural health monitoring was developed and verified. The present paper is devoted to proposing an integrated health monitoring scheme for elastic beam-like structures, where flexure dominates structural responses, based on static testing and measurements using the developed sensors. A series of experimental investigations on steel beams with different levels of damage are first carried out. The static strain measurements from distributed sensors are characterised and some concerns on the data processing and feature extraction are discussed. On the basis of the extracted features, structural health monitoring (SHM) investigations are deployed in three parts: damage identification with no requirement for a structural analytical model, parametric estimation based on finite element (FE) models, and evaluation of s...

Suzhen Li

Papers

Development of Distributed Long-gage Fiber Optic Sensing System for Structural Health Monitoring

Two-level Damage Detection Strategy Based on Modal Parameters from Distributed Dynamic Macro-strain Measurements

Modal Analysis on Macro-strain Measurements from Distributed Long-gage Fiber Optic Sensors:

A Nonphysics-based Approach for Vibration-based Structural Health Monitoring under Changing Environmental Conditions

Health monitoring of flexural steel structures based on distributed fibre optic sensors