Dynamic Structural Health Monitoring Research Articles

Assessment of different optimal sensor placement methods for dynamic monitoring of civil structures and infrastructures

The optimal sensor placement is a critical aspect in the structural health monitoring of structures, as the number and layout of sensors directly impact the quality and usefulness of collected data. When developing a monitoring system, it is of paramount importance to use the minimum number of sensors to gain the maximum amount and quality of information. However, in the case of a limited number of sensors, their location on the structure becomes crucial. This study aims to assess the potential of several optimal sensor placement methods for the development of cost-efficient and well-dimensioned dynamic structural health monitoring systems to be implemented in a wide range of civil engineering structures and infrastructures. Indeed, the construction stock consists of a great variety of civil engineering structures and infrastructures that significantly differ from each other in terms of typology, historical period, construction techniques, materials, etc. Some of the most widely used optimal sensor placement methods are selected and applied in real case studies, and the obtained sensor configurations are discussed and compared. The results illustrated in this paper will contribute to defining good practice in the optimal sensor placement procedure for typical civil engineering structures and infrastructures.

Quantifying the value of SHM information for bridges under flood-induced scour

Bridge scour is a leading cause of failure for bridges over waterways and is notoriously difficult to detect with accuracy. Dynamic Structural Health Monitoring (SHM) of bridges for scour has gained traction in recent years as monitoring systems have improved and the reliability of measurements increased. Due to the large number of bridges on typical networks and the limited financial resources within asset management agencies, decision-makers must prioritize certain structures when it comes to management in the event of flooding. The decision to install a dynamic SHM system on a bridge must be balanced by the financial benefit of doing so, as limited resources often need to be carefully rationed. In this paper, a methodology is proposed to evaluate such benefit based on the Value of Information (VoI) from Bayesian decision analysis. A case study is presented whereby a dynamic SHM system is considered to be installed on a typical bridge with the aim to support emergency management operations during flooding. The proposed methodology allows computation of the financial benefit of installing a dynamic SHM system over a certain reference period, thus accounting for multiple flood events and scenarios. The various elements of the procedure are discussed in detail.

Underexposed Vision-Based Sensors’ Image Enhancement for Feature Identification in Close-Range Photogrammetry and Structural Health Monitoring

This paper describes an alternative structural health monitoring (SHM) framework for low-light settings or dark environments using underexposed images from vision-based sensors based on the practical implementation of image enhancement algorithms. The proposed framework was validated by two experimental works monitored by two vision systems under ambient lights without assistance from additional lightings. The first experiment monitored six artificial templates attached to a sliding bar that was displaced by a standard one-inch steel block. The effect of image enhancement in the feature identification and bundle adjustment integrated into the close-range photogrammetry were evaluated. The second validation was from a seismic shake table test of a full-scale three-story building tested at E-Defense in Japan. Overall, this study demonstrated the efficiency and robustness of the proposed image enhancement framework in (i) modifying the original image characteristics so the feature identification algorithm is capable of accurately detecting, locating and registering the existing features on the object; (ii) integrating the identified features into the automatic bundle adjustment in the close-range photogrammetry process; and (iii) assessing the measurement of identified features in static and dynamic SHM, and in structural system identification, with high accuracy.

Static and Dynamic Structural Health Monitoring System for Bridges

Abstract This document describes a system for static and dynamic monitoring of the structural health of bridges, but not only. The need to develop the system resulted from the difficulties encountered by the authors in installing and operating complex monitoring systems, composed of elements from different manufacturers, with different measurement technologies, power supplies, communication modes and software applications. The described system facilitates the integration of different measurements, sensors, power supplies and communication technologies, in a unitary system that allows both static and dynamic measurements, simultaneously.

Dynamic structural health monitoring of a model wind turbine tower using distributed acoustic sensing (DAS)

Maintenance of wind turbine towers is currently a manual process that requires visual inspection and bolt tightening yearly. This process is costly to energy companies and its necessity is not well-defined. In this study, two Rayleigh-based distributed fiber optic sensing technologies are evaluated and compared for their ability to monitor the dynamic structural behavior of a model wind turbine tower subject to free and forced vibration. They are further tested for their ability to detect structural phenomena associated with loose bolts and material damage within the tower. The two technologies examined are optical frequency domain reflectometry (OFDR) and phase-based optical time domain reflectometry (phi-OTDR), which is a technology used in distributed acoustic sensing (DAS). OFDR is a tested and proven strain measurement technology commonly used for structural health monitoring but can only make strain measurements over short distances (10 s of meters). OFDR was used to validate the measurements made with phi-OTDR which can measure over much longer distances (several kilometers). Due to its sensing distance capability, phi-OTDR is a promising technology for monitoring many wind turbines networked together with a single fiber optic cable. This study presents a first-of-its-kind use of phi-OTDR for structural health monitoring to demonstrate its capabilities.

Inverse problem for dynamic structural health monitoring based on slime mould algorithm

In this paper, damage detection, localization and quantification are performed using modal strain energy change ratio (MSEcr) as damage indicator combined with a new optimization technique, namely slime mould algorithm (SMA) developed in 2020. The SMA algorithm is employed to assess structural damage and monitor structural health. Two structures, including a laboratory beam and a bar planar truss are considered to study the effectiveness of the proposed approach. Another recent algorithm called marine predators algorithm (MPA) is also used for comparison purposes with SMA. The MSEcr is utilized in the first stage to predict the location of the damaged elements. Single and multiple damages cases are analysed based on different number of modes to study the sensitivity of the proposed indicator to the total number of modes considered in the analysis. Next, this indicator is used as an objective function in a second stage to solve the inverse problem using SMA and MPA for damage quantification of the elements identified in the first stage. Experimental validation is conducted using a 3D frame structure with four stories that have damaged components. It is demonstrated that the proposed approach, using MSEcr and SMA, provides superior results for the considered structures. The effectiveness of this technique is tested by introducing a white Gaussian noise with different levels, namely 2% and 4%. The results show that the provided approach can predict the location and level of damage with high accuracy after introducing the noise.

Dynamic structural health monitoring for concrete gravity dams based on the Bayesian inference

The preservation of concrete dams is a key issue for researchers and practitioners in dam engineering because of the important role played by these infrastructures in the sustainability of our society. Since most of existing concrete dams were designed without considering their dynamic behaviour, monitoring their structural health is fundamental in achieving proper safety levels. Structural Health Monitoring systems based on ambient vibrations are thus crucial. However, the high computational burden related to numerical models and the numerous uncertainties affecting the results have so far prevented structural health monitoring systems for concrete dams from being developed. This study presents a framework for the dynamic structural health monitoring of concrete gravity dams in the Bayesian setting. The proposed approach has a relatively low computational burden, and detects damage and reduces uncertainties in predicting the structural behaviour of dams, thus improving the reliability of the structural health monitoring system itself. The application of the proposed procedure to an Italian concrete gravity dam demonstrates its feasibility in real cases.

Synergistic and combinatorial optimization of finite element models for monitored buildings

This paper investigates the use of rank aggregation strategies for the finite element model calibration of monitored masonry structures subjected to earthquakes. Ranking is used to obtain optimal results from several competing optimization strategies, with the final aim of establishing a numerical model of reference to support the existing monitoring systems installed on the structures. For the tuning of the model, different optimization methods are currently employed (i.e., genetic optimization, particle swarm optimization, and simulated annealing optimization), which can provide an initial nonunique definition of the structural parameters. Starting from the results obtained from selected updating methods, a combinatorial parameter selection is proposed to define the best finite element model among several optimal results. In this case, the ranking problem is solved by using a Plackett-Luce model-based strategy. The calibrated model is a useful tool to investigate the dynamic response of the structure, allowing a preliminary structural assessment at the same time. The data recorded by the permanent dynamic structural health monitoring system installed on a masonry building, the Town Hall of Pizzoli in central Italy, are used to demonstrate the proposed model calibration strategy.

Damage assessment of an existing RC infilled structure by numerical simulation of the dynamic response

This paper proposes a dynamic structural health monitoring and damage detection method to assess the structural integrity and safety of an RC framed building with masonry infills. The effectiveness of the method is verified by numerical analyses that were performed on a RC moment-resisting frame structure investigated by Paultre et al. and applied on an existing RC framed building with masonry infill walls, which provide a strong contribution to the dynamic response and seismic performance of the building. Different damage states are simulated through the nonlinear static (pushover) analysis developed by the FE model of the building, and this analysis considers both the bare framed structure and the infilled structure to appraise the damage to the infill walls. The identification and location of the damage is estimated using the modal properties of the damaged building at various steps of the nonlinear analysis. The results highlight the different evolutions of the damage in the bare and infilled frames and the possibility of detection via dynamic monitoring.

Experimental evaluation of vibration based damage identification techniques on a pedestrian bridge

Failures of civil structures, such as bridges, due to natural events or anthropic loads can generate significant social and economic impacts. As an alternative for the identification of damage in these structures, dynamic structural health monitoring has been proposed. This paper presents the experimental evaluation of three damage identification techniques on a full-scale footbridge. One of the evaluated techniques is based on damage localization vectors; a second technique is based on changes in the curvature of the modal shapes, while the third technique uses a numerical model and artificial neural networks for locating the damaged section. Five scenarios of controlled damage were induced in the footbridge. Output-only ambient vibration tests were performed at each damage state and the results of the identification techniques were analyzed. The three implemented techniques showed promising results for the numerical simulations, and two of these techniques produced satisfactory results in the experimental evaluation.

Building Information Modeling (BIM) for Structural Engineering: A Bibliometric Analysis of the Literature

Building information modeling (BIM) is transforming the way of work across the architecture, engineering, and construction (AEC) industry, where BIM offers vast opportunities for improving performance. BIM is therefore an area of great interest across the AEC industry in general and for the structural engineering field in particular. This paper is aimed at providing a broad picture of published papers that relate BIM with structural engineering. This overview will enhance understanding of the state of the research work on this subject, drawing upon bibliometric analysis of 369 papers. Findings provide an updated picture of how now‐available studies that link BIM developments and applications in structural engineering are distributed chronologically, across journals, authors, countries, and institutions. Detailed analyses of citation networks present the cooccurrence map of keywords, citation patterns of journals and articles, the most cited journals, and the top 15 most cited articles on BIM in the area of structural engineering. Discussions demonstrate that research on BIM applications for structural engineering has been constantly growing with a sudden increase after 2014. This study reveals that research attempts on this area have been dominated by exploring generic issues of BIM like information management; however, technical issues of structural engineering, to be resolved through BIM capabilities, have remained overlooked. Moreover, the research work in this area is found to be conducted largely in isolation, comprising disjointed and fragmented research studies. Gaps and important areas for future research include modeling of structural components, automation of the assembly sequence, planning and optimization of off‐site construction, and dynamic structural health monitoring.

Structural Interpretation of Data from Static and Dynamic Structural Health Monitoring of Monumental Buildings

Structural Health Monitoring (SHM) has a crucial role in the diagnosis and conservation of historical buildings, which are typically characterized by articulated fabrics, constructed over decades using different materials and construction techniques. All these issues lead to very complex structural behaviour whose reliable assessment cannot disregard from a sound interpretation of data from SHM systems. SHM systems can be classified into (i) static systems, monitoring the long term time evolutions of specific quantities (such as amplitude of cracks, inclination of walls, relative distances, etc.) and (ii) dynamic systems, continuously monitoring the dynamic response (velocities, accelerations) in order to gather information upon overall dynamic properties such as natural frequencies, mode shapes and damping ratios. The recorded raw data need to be processed in order to distinguish eventual evolutionary trends from the seasonal and daily variations related to thermal effects. In the present work, a simple unified approach for data interpretation acquired from both static and dynamic SHM systems installed in historical buildings is presented. The approach is aimed at: (i) introducing reference quantities for interpretation of seasonal and daily variations, (ii) providing order of magnitudes of reference quantities and (iii) identifying eventual evolutionary trends which could be related to the presence of potential structural criticalities. The approach is illustrated referring to the “Two Towers” of Bologna.

Dynamic structural health monitoring of a civil engineering structure with a POF accelerometer

Purpose – In this work, the paper aims to demonstrate the feasibility of plastic optical fiber (POF) based accelerometers for the structural health monitoring (SHM) of civil engineering structures based on measurements of their dynamic response, namely to estimate natural frequencies. These sensors use POFs, combining the advantages of the optical technology with the robustness of this particular kind of fiber. The POF sensor output is directly compared with the signal from an electrical sensor, demonstrating the potential use of such sensors in structural monitoring applications. Design/methodology/approach – Within this work, the paper demonstrates the feasibility of using a low-cost acceleration system based on a POF accelerometer on the dynamic monitoring of a civil engineering structure, aiming its natural frequency evaluation, which is a primary parameter to be used in SHM methods and numerical models calibration. Findings – A low-cost POF-based accelerometer was used in the characterization of a civil engineering structural component, located in a building at the University of Aveiro Campus, being used to estimate its natural frequency with a relative error of 0.36 percent, comparatively to the value estimated recurring to a calibrated electronic sensor. Originality/value – Optical fiber sensors take advantage of the fibers properties, such as immunity to electromagnetic interference and electrical isolation. They are very attractive for use in hostile environments, like submerse environments or flammable atmospheres where electrical currents might pose a hazard. The advantages of POF itself should also be considered, like resistance to hash environments, robustness, flexibility, low-cost interrogation units and high numeric aperture (lower cost components). The paper demonstrates the feasibility of using a low-cost acceleration system based on a POF accelerometer on the dynamic monitoring of a civil engineering structure, aiming its natural frequency evaluation.

Geometrically non-linear transient thermo-elastic response of FG beams integrated with a pair of FG piezoelectric sensors

This paper deals with the geometrically non-linear static and dynamic analysis of functionally graded (FG) beams under combined effect of thermal fields and mechanical excitations integrated with a pair of sensor layers for structural monitoring. The sensor layers are considered to be made of the functionally graded piezoelectric (FGP) materials. The material properties of the host FG beam and FGP sensors are assumed to be graded in the thickness direction according to a power law distribution. The von Karman type geometric non-linearity and the first-order shear deformation theory are used to formulate the governing equations of motion utilizing the Hamilton principle. The solution of coupled non-linear partial differential equations in spatial and time domains is obtained using the hybrid generalized differential quadrature method–Newmark algorithm–Newton–Raphson iterative scheme. A set of parametric study is conducted to show the influence of geometric non-linearity, material parameters and temperature field on the static and dynamic responses of piezoelectric FG beams subjected to impulsive loads. Due to the absence of similar results in the specialized literature, it is expected that the results of this research will be instrumental toward an optimal design of piezoelectric FG structures for static and dynamic structural health monitoring purpose.

Dynamic structural health monitoring of Saint Torcato church

The paper presents the dynamic structural health monitoring activities on Saint Torcato church, in Guimarães, Portugal, which has significant structural problems due to soil settlements. Cracks can be observed on the main and the lateral façades, the bell-towers are leaning, and the arches in the nave exhibit a failure mechanism with cracks and vertical deformations. These phenomena are progressing and a structural intervention is planned. A monitoring system has been installed to control the current condition and to assess the success of the future intervention. The paper shows the monitoring results with an emphasis in the dynamic analysis carried out before the structural strengthening, namely with respect to: experimental tests with output-only techniques for frequencies, damping and mode shapes estimation, FE model updating analysis and dynamic monitoring. The automatic system identification process uses ambient vibration signatures in combination with cluster analysis and rule-based approach for the interpretation of the results of the Stochastic Subspace Identification method.

Dynamic Structural Health Monitoring of Slender Structures Using Optical Sensors

In this paper we summarize the research activities at the Instituto de Telecomunicações—Pólo de Aveiro and University of Aveiro, in the field of fiber Bragg grating based sensors and their applications in dynamic measurements for Structural Health Monitoring of slender structures such as towers. In this work we describe the implementation of an optical biaxial accelerometer based on fiber Bragg gratings inscribed on optical fibers. The proof-of-concept was done with the dynamic monitoring of a reinforced concrete structure and a slender metallic telecommunication tower. Those structures were found to be suitable to demonstrate the feasibility of FBG accelerometers to obtain the structures' natural frequencies, which are the key parameters in Structural Health Monitoring and in the calibration of numerical models used to simulate the structure behavior.