Civil Infrastructure Monitoring Research Articles

Intensity-modulated abrupt tapered Fiber Mach-Zehnder Interferometer for the simultaneous sensing of temperature and curvature

An abrupt tapered fiber In-Line Mach-Zehnder Interferometer sensor for simultaneous measurement of temperature and curvature is proposed and experimentally demonstrated. The sensor head is fabricated by arcing Corning SMF-28 using a commercial arc fusion splicer. The individual parameters discrimination was achieved by manipulating the unequal sensitivities of optical power to temperature and curvature obtained at two wavelengths within the sensing spectrum. The curvature and temperature sensitivities at λ1 (1537nm) and λ2 (1568.7nm) were found to be 11.8264dBm/m−1, 12.4885dBm/m−1 and 0.0829dBm/°C, 0.0833dBm/°C, respectively. The experimental results show unperturbed readings with rms deviation of ±0.1801m−1 and ±0.0826°C, for curvature and temperature measurements, respectively, through measurement of optical power response of the sensor. With this simultaneous sensing technique, the proposed sensor can be deployed for many field applications such as nondestructive structural health monitoring of civil infrastructure.

Design of Structural Health Monitoring Using Wireless Sensor Network Case Study Pasupati Bridge

Structural health monitoring (SHM) of civil infrastructure using wireless sensor networks (WSNs) has received significant public attention in recent years. The benefits of WSNs are that they are low-cost, easy to install, and provide effective data management via on-board computation. This paper reports on the designing SHM using WSN on the Pasupati Bridge a cable-stayed bridge in Bandung with a construction 303-m long bridge across the valley , including a cable stayed bridge along 161-m. The design central components of the WSN that will be proposed are the Imote2 smart sensor platforms, a custom-designed sensor boards, and gateway. In total, 42 sensor nodes and one gateway will be proposed to monitor the bridge using autonomous SHM application with vibration triggering the system to initiate monitoring.

Application of High-precision Accelerometer Made in Korea to Health Monitoring of Civil Infrastructures

A high-precision force-feedback 3-axes accelerometer developed in Korea has been investigated and studied for the verification of feasibility in the computational analysis and health monitoring of civil infrastructures. Through a series of experiment, the nonlinearity, bandwidth, low-frequency signal measurement accuracy and bias characteristics of the accelerometer has been thoroughly compared to those of two accelerometers produced by two market leaders in domestic and global accelerometer market. The experiment results shows that the overall measurement performance of the accelerometer has superiority over the performance of the two accelerometers from global market leader companies. Especially, the accelerometer shows a better low-frequency signal measurement accuracy and constant bias characteristic, which are mostly required in the computational analysis and the long-term health monitoring of large-scale civil infrastructures.본 논문에서는 풍산 FNS에서 개발한 force-feedback형 고정밀 국산 3축 가속도계의 성능을 실험적으로 평가하고, 건설 구조물 전산구조해석 및 유지관리용 건전성 모니터링에의 적용성을 논한다. 레이트 테이블 및 가진기를 통해 다양한 형태로 가진실험을 수행함으로써 국산 가속도계의 비선형성, 대역폭, 저주파 신호계측 성능, 바이어스 특성을 검증하고, 국내 가속도계 시장의 대부분을 차지하고 있는 해외 업체들의 대표적 가속도계와 성능을 비교 평가하여 국산 가속도계의 적용성과 시장진입 가능성을 평가하였다. 실험분석 결과 국산 가속도계는 실험으로 평가한 모든 항목에서 실험에 사용된 수입 가속도계보다 좋은 성능을 보였다. 특히 건설 구조물 계측에 필수적인 저주파 대역 계측성능은 수입 가속도계의 성능을 능가하였으며, 바이어스도 상수 특성을 가장 잘 유지하는 것으로 나타나 향후 실험기반 구조해석 및 구조물 장기 건전도 모니터링에 좋은 대안이 될 것으로 평가된다.

Development of High-Sensitivity and Low-Cost Electroluminescent Strain Sensor for Structural Health Monitoring

Visualized strain/stress sensing is receiving interests in structural health monitoring area, but former approaches cannot be effectively applied to civil infrastructure monitoring, because of limited sensitivity to low-level response and/or limited response to civil structures for both static and dynamic strain/stress. This paper presents a high-sensitivity and low-cost method to visualize the strain by employing the precisely controllable Wheatstone bridge and monochrome electroluminance (EL) technology. A sensor prototype is developed to convert the structural strain responses into visible brightness change with brightness change mode (BCM) and to color change with color alternation mode (CAM). In the BCM, the brightness can be changed according to the strain change. In the CAM, two different-color EL panels are used to light on to indicate the necessity for the professional structural health evaluation. Brightness linearity evaluation results show that the BCM is suitable for both static and dynamic low-level strain visualization. Bill of materials shows the cost of the prototype is as low as U.S. $46 including the EL panels.

Recent R&D activities on structural health monitoring in Korea

In this paper, recent research trends and activities on structural health monitoring (SHM) of civil infrastructure in Korea are reviewed. Recently, there has been increasing need for adopting smart sensing technologies to SHM, so this review focuses on smart sensing, monitoring, and assessment for civil infrastructure. Firstly, the research activities on smart sensor technology is reviewed including optical fiber sensors, piezoelectric sensors, wireless smart sensors, and vision-based sensing system. Then, a brief overview is given to the recent advances in smart monitoring and assessment techniques such as vibration-based global monitoring techniques, local monitoring with piezoelectric materials, decentralized monitoring techniques for wireless sensors, wireless power supply and energy harvest. Finally, recent joint SHM activities on several test beds in Korea are discussed to share the up-to-date information and to promote the smart sensors and monitoring technologies for applications to civil infrastructure. It includes a Korea-US joint research on test bridges of the Korea Expressway Corporation (KEC), a Korea-US-Japan joint research on Jindo cable-stayed bridge, and a comparative study for cable tension measurement techniques on Hwamyung cable-stayed bridge, and a campaign test for displacement measurement techniques on Sorok suspension bridge.

Structural monitoring and identification of civil infrastructure in the United States

Monitoring the performance and estimating the remaining useful life of aging civil infrastructure in the United States has been identified as a major objective in the civil engineering community. Structural health monitoring has emerged as a central tool to fulfill this objective. This paper presents a review of the major structural monitoring programs that have been recently implemented in the United States, focusing on the integrity and performance assessment of large-scale structural systems. Applications where response data from a monitoring program have been used to detect and correct structural deficiencies are highlighted. These applications include (but are not limited to): i) Post-earthquake damage assessment of buildings and bridges; ii) Monitoring of cables vibration in cable-stayed bridges; iii) Evaluation of the effectiveness of technologies for retrofit and seismic protection, such as base isolation systems; and iv) Structural damage assessment of bridges after impact loads resulting from ship collisions. These and many other applications show that a structural health monitoring program is a powerful tool for structural damage and condition assessment, that can be used as part of a comprehensive decision-making process about possible actions that can be undertaken in a large-scale civil infrastructure system after potentially damaging events.

Target-free approach for vision-based structural system identification using consumer-grade cameras

Recent reports on America's infrastructure have emphasized the importance of structural health monitoring of civil infrastructures. System identification is a key component of many structural health monitoring strategies. Current system identification methods estimate models of a structure by measuring displacements, accelerations, and strains with wired or wireless sensors. However, these methods typically involve installation of a limited number of sensors at discrete locations and require additional data acquisition devices. To overcome these limitations, computer vision-based techniques have been introduced recently that employ high-speed and high-resolution cameras. Such cameras can be quite costly and require tedious installation of targets. This paper investigates the potential of using consumer-grade cameras for structural system identification without the need to install targets. The underlying methods for target-free displacement measurements are introduced, including region of interest selection, feature detection, point tracking, and outlier removal. A set of experiments are conducted to assess the efficacy of the proposed approach by comparing the accuracy of the identified model with one obtained using a conventional wired system. Careful comparison of the results demonstrates the significant potential of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd.

Monitoring of Architectural Buildings and Civil Infrastructures

Monitoring of Architectural Buildings and Civil Infrastructures

A framework for the damage evaluation of acoustic emission signals through Hilbert–Huang transform

The acoustic emission (AE) is a powerful and potential nondestructive testing method for structural monitoring in civil engineering. Here, we show how systematic investigation of crack phenomena based on AE data can be significantly improved by the use of advanced signal processing techniques. Such data are a fundamental source of information that can be used as the basis for evaluating the status of the material, thereby paving the way for a new frontier of innovation made by data-enabled analytics. In this article, we propose a framework based on the Hilbert–Huang Transform for the evaluation of material damages that (i) facilitates the systematic employment of both established and promising analysis criteria, and (ii) provides unsupervised tools to achieve an accurate classification of the fracture type, the discrimination between longitudinal (P-) and traversal (S-) waves related to an AE event. The experimental validation shows promising results for a reliable assessment of the health status through the monitoring of civil infrastructures.

Smart One-Channel Sensor Node for Ambient Vibration Test with Applications to Structural Health Monitoring of Large Civil Infrastructures

Dynamic characteristics of structures have been monitored for safe operation and efficient maintenance of large civil infrastructures. For vibration data measurement, the conventional system uses cables, which cause very expensive costs and inconvenient installation. Therefore, various wireless sensor nodes have been developed to replace the conventional wired system. However, there still remain lots of issues to be resolved such as time synchronization between sensor nodes, data loss, data security, and power supply. In this study, Smart One-Channel Sensor Node (SOSN) was developed to measure vibration data, which can practically solve the issues on installation, time synchronization, and data storage. It is designed for temporal measurement with a limited capacity to operate for several hours using embedded batteries. Laboratory tests were carried out to verify the performance of the developed SOSN compared with conventional wired system. Its practical advantages were investigated through three full-scale tests on large civil infrastructures. Three field applications revealed that SOSN is a very practical tool for short-term monitoring of large civil infrastructures with respect to traffic control, installation time and convenience, secure data gathering, and so forth.

Building structural health monitoring using dense and sparse topology wireless sensor network

Wireless sensor technology has been opened up numerous opportunities to advanced health and maintenance monitoring of civil infrastructure. Compare to the traditional tactics, it offers a better way of providing relevant information regarding the condition of building structure health at a lower price. Numerous domestic buildings, especially longer-span buildings have a low frequency response and challenging to measure using deployed numbers of sensors. The way the sensor nodes are connected plays an important role in providing the signals with required strengths. Out of many topologies, the dense and sparse topologies wireless sensor network were extensively used in sensor network applications for collecting health information. However, it is still unclear which topology is better for obtaining health information in terms of greatest components, node\'s size and degree. Theoretical and computational issues arising in the selection of the optimum topology sensor network for estimating coverage area with sensor placement in building structural monitoring are addressed. This work is an attempt to fill this gap in high-rise building structural health monitoring application. The result shows that, the sparse topology sensor network provides better performance compared with the dense topology network and would be a good choice for monitoring high-rise building structural health damage.

Experimental study on pullout performance of sensing optical fibers in compacted sand

The distributed optical fiber sensing systems have played an increasingly important role in monitoring civil infrastructures over the past few years. One of the main challenges of their applications to geotechnical monitoring is to increase the reliability of strain sensing optical fibers in measuring the deformation of surrounding soil masses. In this paper, a pullout test method is proposed to characterize the deformation compatibility between an optical fiber and soil. A series of pullout tests on three types of sand-embedded optical fibers are conducted to investigate the performance of the fiber–sand interface. Based on the test results, an explicit tri-linear pullout force–displacement relationship is proposed to describe the mechanical behavior of the fiber–sand interface. The performance of the three fibers regarding fiber–sand interaction mechanism is evaluated in terms of ratio of effective pullout displacement to diameter, ratio of residual pullout displacement to diameter, peak shear strength and residual shear strength. All four parameters of the three fibers are found to have approximately linear relationships with the applied confining pressure, which reveals that the deformation compatibility of the fiber–sand interface is utterly dependent on the confining pressure. For all the three fibers, the first shear stiffness coefficient is about 8N/mm and the ratio of residual to peak shear strength is about 0.5. Furthermore, the Mohr–Coulomb failure criterion is used to get the cohesions and friction angles of the three fiber–sand interfaces. Through a comparison of the pullout performance, one out of three types of fibers tested is found to be more preferable for soil deformation measurement in laboratory-scale tests. The conclusions can provide valuable references for predicting the fiber–soil interface behavior and evaluating the reliability of strain monitoring data.

Recent advances in wireless smart sensors for multi-scale monitoring and control of civil infrastructure

While much of the technology associated with wireless smart sensors (WSS) has been available for over a decade, only a limited number of full-scale implementations have been realized for civil infrastructure, primarily due to the lack of critical hardware and software elements. Using the Imote2, a flexible WSS framework has been developed for full-scale, autonomous structural health monitoring (SHM) that integrates the necessary software and hardware elements, while addressing key implementation requirements for civil infrastructure. This paper discusses the recent advances in the development of this WSS framework and extensions to structural control. Their successful implementations at full-scale for SHM of the 2nd Jindo Bridge in South Korea and the Government Bridge at the Rock Island Arsenal in Illinois, USA, as well as for wireless control of a lab-scale structure are presented.

Detection of steel fatigue cracks with strain sensing sheets based on large area electronics.

Reliable early-stage damage detection requires continuous monitoring over large areas of structure, and with sensors of high spatial resolution. Technologies based on Large Area Electronics (LAE) can enable direct sensing and can be scaled to the level required for Structural Health Monitoring (SHM) of civil structures and infrastructure. Sensing sheets based on LAE contain dense arrangements of thin-film strain sensors, associated electronics and various control circuits deposited and integrated on a flexible polyimide substrate that can cover large areas of structures. This paper presents the development stage of a prototype strain sensing sheet based on LAE for crack detection and localization. Two types of sensing-sheet arrangements with size 6 × 6 inch (152 × 152 mm) were designed and manufactured, one with a very dense arrangement of sensors and the other with a less dense arrangement of sensors. The sensing sheets were bonded to steel plates, which had a notch on the boundary, so the fatigue cracks could be generated under cyclic loading. The sensors within the sensing sheet that were close to the notch tip successfully detected the initialization of fatigue crack and localized the damage on the plate. The sensors that were away from the crack successfully detected the propagation of fatigue cracks based on the time history of the measured strain. The results of the tests have validated the general principles of the proposed sensing sheets for crack detection and identified advantages and challenges of the two tested designs.

State-of-the-art in structural health monitoring of large and complex civil infrastructures

Researchers and administrative authorities have long recognized the significance of implementing long-term structural health monitoring (SHM) systems for civil infrastructures, especially large-span space structures or other complex infrastructures, in order to secure structural safety and issue warnings regarding the structural damage prior to costly repair or even collapse. This paper starts with a critical review of SHM objectives and standardization for the SHM in civil infrastructures. At the same time as an example, the authors present their experiences through the case study of SHM applications for large and complex civil infrastructures through a custom-made polytypic and synchronous data acquisition device that was utilized in the SHM of the large-span gymnasium in Dalian. The paper concludes with a discussion of state-of-the-art in the SHM for civil infrastructures, highlighting areas where further work is needed.

Performance assessment of indigenously developed FBG strain sensors under short-term and long-term loadings

Fibre Bragg Grating (FBG) sensors are the most recent type of fibre optic sensors, which are gaining importance in the field of structural health monitoring of civil infrastructure. These are proven to be more versatile due to their distinct advantages such as high sensitivity, immunity to electromagnetic interference, ease of multiplexing and remote sensing. These are suitable for the short-term and long-term monitoring of the structures. Multiple Fibre Bragg Grating (FBG) sensors can be surface mounted and/or embedded in structures to measure strain, temperature, cracks and vibrations. Use of FBG sensors for real time health monitoring of various civil engineering structures is well-established in western world since last decade, whereas in the Indian context this technology is still in a nascent stage. In this paper, performance assessment of indigenously developed FBG sensors for the application of health monitoring of civil engineering structures by conducting short-term and long-term studies is presented. Brief details of the laboratory studies carried out on indigenously developed FBG sensors are covered in this paper. From the laboratory studies it is found that, these FBG sensors are suitable in health monitoring of civil engineering structures.

Construction performance monitoring via still images, time-lapse photos, and video streams: Now, tomorrow, and the future

Timely and accurate monitoring of onsite construction operations can bring an immediate awareness on project specific issues. It provides practitioners with the information they need to easily and quickly make project control decisions. Despite their importance, the current practices are still time-consuming, costly, and prone to errors. To facilitate the process of collecting and analyzing performance data, researchers have focused on devising methods that can semi-automatically or automatically assess ongoing operations both at project level and operation level. A major line of work has particularly focused on developing computer vision techniques that can leverage still images, time-lapse photos and video streams for documenting the work in progress. To this end, this paper extensively reviews these state-of-the-art vision-based construction performance monitoring methods. Based on the level of information perceived and the types of output, these methods are mainly divided into two categories (namely project level: visual monitoring of civil infrastructure or building elements vs. operation level: visual monitoring of construction equipment and workers). The underlying formulations and assumptions used in these methods are discussed in detail. Finally the gaps in knowledge that need to be addressed in future research are identified.

Distributed Sensor Networks for Health Monitoring of Civil Infrastructures

Distributed Sensor Networks for Health Monitoring of Civil Infrastructures

On the advances of automatic modal identification for SHM

Structural health monitoring of civil infrastructures has great practical importance for engineers, owners and stakeholders. Numerous researches have been carried out using long-term monitoring, for instance the Rio-Niterói Bridge in Brazil, the former Z24 Bridge in Switzerland, the Millau Bridge in France, among others. In fact, some structures are monitored 24/7 in order to supply dynamic measurements that can be used for the identification of structural problems such as the presence of cracks, excessive vibration, damage or even to perform a quite extensive structural evaluation concerning its reliability and life cycle. The outputs of such an analysis, commonly entitled modal identification, are the so-called modal parameters, i.e. natural frequencies, damping ratios and mode shapes. Therefore, the development and validation of tools for the automatic identification of modal parameters based on the structural responses during normal operation is fundamental, as the success of subsequent damage detection algorithms depends on the accuracy of the modal parameters estimates. The proposed methodology uses the data driven stochastic subspace identification method (SSI-DATA), which is then complemented by a novel procedure developed for the automatic analysis of the stabilization diagrams provided by the SSI-DATA method. The efficiency of the proposed approach is attested via experimental investigations on a simply supported beam tested in laboratory and on a motorway bridge.

An integrated approach for structural health monitoring using an in-house built fiber optic system and non-parametric data analysis

Multivariate statistics based damage detection algorithms employed in conjunction with novel sensing technologies are attracting more attention for long term Structural Health Monitoring of civil infrastructure. In this study, two practical data driven methods are investigated utilizing strain data captured from a 4-span bridge model by Fiber Bragg Grating (FBG) sensors as part of a bridge health monitoring study. The most common and critical bridge damage scenarios were simulated on the representative bridge model equipped with FBG sensors. A high speed FBG interrogator system is developed by the authors to collect the strain responses under moving vehicle loads using FBG sensors. Two data driven methods, Moving Principal Component Analysis (MPCA) and Moving Cross Correlation Analysis (MCCA), are coded and implemented to handle and process the large amount of data. The efficiency of the SHM system with FBG sensors, MPCA and MCCA methods for detecting and localizing damage is explored with several experiments. Based on the findings presented in this paper, the MPCA and MCCA coupled with FBG sensors can be deemed to deliver promising results to detect both local and global damage implemented on the bridge structure.