Journal of Civil Structural Health Monitoring最新文献

The development of operational modal analysis (OMA) techniques has enabled the monitoring of large civil engineering structures, such as long-span bridges and high-rise buildings. However, implementing these techniques in real-world testing sites with limited resources remains a challenge. This study introduces a novel approach to obtain the modal characteristics of a box girder bridge in a more cost-effective and simplified manner, with experiments performed in a gap of more than 4 years (Years: 2018 and 2023). The study proposes two output-only frequency domain system identification techniques, namely roving reference normalized power spectrum and roving reference frequency domain decomposition, as part of the OMA-based approach. These techniques involve measuring responses from a pair of roving accelerometers. The collected vibration data records the concrete bridge's response to various external factors, including vehicular traffic on the carriageway, pedestrian movement, river flow, and wind. Despite weak environmental excitations and sensor noise, the findings suggest that accurate modal properties can still be extracted. The two proposed OMA approaches yielded five mode shapes and modal frequencies with closely matching results. When these experimental findings are compared with the numerical results, they exhibit a notable level of consistency. The paper identifies the dynamic characteristics of bridge structures from ambient vibration responses using only two accelerometers with two-point roving technique. This is especially important in real-world testing sites where data are inevitably noisy, unlike in laboratory environments. Additionally, it significantly reduces the cost of the bridge health monitoring.

Continuous monitoring of the structural health of strategic structures and transport infrastructures plays a crucial role in providing an effective assessment of the safety conditions and in timely planning of the ordinary and extraordinary maintenance programme. Deformation monitoring and dynamic characteristic identification are some commonly used strategies for this purpose. One of the main challenges of recent years in the field of structural health monitoring is the use of data deriving from satellite interferometry, capable of providing information on structural deformations at a local and territorial scale. Despite the solidity and dependability of satellite-based methods for assessing ground deformation over time, when it comes to structural surveillance, there are certain circumstances under which satellites are incapable of accurately assessing displacements. This is particularly true for structures that are sensitive to temperature variations. The paper uses the “Ponte della Musica–Armando Trovajoli” in Rome as a case study to explore these aspects in more depth. This bridge has a steel arch structure with a prestressed concrete deck below it. It represents an example in which satellite differential interferometry does not allow obtaining useful information on displacement, at least for the most deformable portion of the deck, and therefore also on any pathological movements. This work proposes a 3D digital twin of the bridge, appropriately calibrated through experimental measurements of the environmental vibrations performed on the bridge. This will allow to evaluate the role played by thermal deformations related to air temperature variations and thus better understand the connection between physiological deformations and satellite limits.

This paper offers a structural assessment of the historical Santa Maria Church and its Guesthouse building in Trabzon, Turkey. This process involves non-destructive experimental investigation using ambient vibration test and numerical evaluation using finite element method. Finite element model updating procedure was employed for the buildings using experimental data such as dynamic features provided by the ambient vibration test. Time-history analyses were carried out by using initial and final finite element models to draw attention to the effectiveness of the finite element model updating procedure and evaluate the seismic performance. The 1992 Erzincan earthquake ground motion data was used for seismic analysis. The ground motion was exposed to buildings in bidirectional. The maximum displacements and principal stresses are detailed at the end of the analysis using contour diagrams. Result of the analyses, the buildings demonstrated a Limited Damage Performance Level throughout the imposed seismic record according to the Earthquake Risk Management Guide for Historical Structures which is a formal guide.

The health monitoring system is considered mandatory during the operating period of truss structures, which are periodically tested to investigate damage detection in the critical components of such structures. Wave propagation-based damage detection has just been implemented in health monitoring systems. This paper proposes four new, efficient, and robust methodologies for systematic structural damage detection of truss structures. The main key used in the proposed methods is the continuous detection of changes in the node position of an element, the velocity time series responses, or the frequency spectrum of the responses affected by probable damage. Maximum amplitude ratio (MAR), Coherency ratio (CR), Maximum amplitude ratio and summation ratio of PSD spectrum (MPSDR & SPSDR) are four approaches for damage detection in the structure, which are based on assigning a relative damage index (RDI) to each truss element and calculating the total damage intensity (TDI) for the entire considered span of the main structure. The proposed methods have been validated both experimentally and mathematically to determine they could be utilized as reliable methods of structural health monitoring. To validate the proposed methods, a laboratory was used to construct a three-dimensional truss structure with two spans. The results show that all methods are able to illustrate the presence of damage in one span of the structure by locating the damaged element that has a higher RDI value. Moreover, the SPSDR method is sensitive to the amount of damage, as the TDI parameter increases efficiently as the stiffness of the damaged element is reduced. The main feature of the proposed methods that distinguishes them from others is their ability to localize and identify the intensity of a 10 percent stiffness reduction in a well-organized element.

Bridge inspection is a crucial process for ensuring the safety and reliability of transportation infrastructure. Traditional bridge inspections are time-consuming, costly, and often require bridges to be closed, disrupting traffic. In recent years, the use of drones and computer vision techniques for bridge inspection has gained attention due to their ability to provide accurate and comprehensive data while reducing costs and disruptions. This paper presents an automated bridge inspection framework that utilizes drones and computer vision techniques for detecting and analyzing cracks on bridge decks. The framework comprises three main components: orthomosaic map generation, deep learning-based crack detection, and georeferencing and visualization in a geographic information system (GIS) platform. The cracks are segmented, identified, and extracted with their georeferenced coordinates, which can be seamlessly integrated into a GIS platform. This integration enables enhanced visualization and spatial analysis of the cracks. In addition, an image data set has been created to facilitate the process of crack segmentation in the context of the proposed automated bridge inspection framework. The network achieved a mIoU of 80.5%, a dice coefficient of 88.1%, a precision of 77.5%, and a recall of 76.5%, highlighting the robust performance of the network in crack detection. The proposed framework was evaluated on a real bridge, and the results showed that it detected and analyzed cracks accurately and efficiently. This framework can be adaptable to various types of infrastructure, making it a valuable tool for managing transportation infrastructure.

This paper reports on a series of experimental tests and a numerical study carried out on the historic masonry bridge of Santa Teresa of Bitonto, located in Bari (Southern Italy). A systematic working technique was planned and carried out with the final objective of defining the dynamic properties of the bridge and verifying the seismic repose by means of a response spectrum analysis. Initial stages were carried out including historical research, visual inspection, and geometric integrated aerial and ground survey on-site using UAV technique for the identification of the geometric details of the structural and non-structural elements of the bridge. An experimental campaign was scheduled and executed by performing free and forced-vibration tests using uniaxial and biaxial accelerometers placed at 22 monitoring points to retrieve the main vibration modes of the bridge with their corresponding frequencies and damping ratios. Although the free vibration tests detected only the main mode of vibration due to the squat nature of the structure, the forced-vibration tests help to confirm the findings and identify further modes of vibration. The consistency of the experimental frequencies was statistically confirmed by varying the conditions of the forced-vibration tests. A Finite-Element (FE) model was constructed and calibrated qualitatively (i.e., order of vibration modes) with respect to the experimental ones, based on both the geometric survey and the visual inspection outputs. Then, a second phase of calibration was undertaken by tuning the remaining free parameters to match the numerical values of all the detected modes. The calibrated model, capable of producing the experimental results, was adopted for performing a response spectrum analysis for the global response evaluation of the bridge. The results showed a globally acceptable level of stress, while excessive values were limitedly observed in a few critical zones.

It is very important to distinguish the reason of change in natural frequencies of structures either caused by a possible damage or environmental conditions (temperature and humidity). In this study, the changes in the dynamic properties of masonry and reinforced concrete minarets under environmental effects, such as temperature and humidity, were investigated. The masonry minarets of İskenderpaşa, Hacı Kasım, and Tavanlı Mosques and the reinforced concrete minarets of Karadeniz Technical University, Dilaveroğlu and Papatya Mosques in Trabzon were monitored by ambient vibration test method, and the relationship between natural frequencies and temperature and humidity was tried to be determined. For this purpose, the natural frequencies of these minarets were measured at certain intervals under different temperature and humidity conditions over a period of approximately 6 months. The vibration measurement system which was developed by our research team was used in the measurements. From the data collected by these measurements, the variation intervals of the natural frequencies (the smallest and the highest values), the percentages of change and their relations with temperature and humidity were revealed. This relationship was determined using linear–non-linear simple and multiple regression analyses. From this study, it was found that the natural frequencies change under environmental effects, such as temperature and humidity, and this rate of change was approximately 7%. There was moderate correlation in Tavanlı, Dilaveroğlu, and Papatya Minarets, and strong correlation in Hacı Kasım Minaret.

Spatio-temporal (S-T) analysis is not typical in structural monitoring applications of buildings and infrastructure. However, monitoring always includes the temporal component, and observations are often captured in specific locations. In other words, a monitoring dataset could also be considered a spatio-temporal archive, notwithstanding that not all monitoring applications can benefit from S-T processing methods. The paper discusses spatio-temporal analysis using the structural monitoring dataset of the Cathedral of Milan, which has an archive of vertical settlements collected from more than 50 years of measurements. The proposed methods can be adapted and extended for other structural monitoring applications, including single buildings, infrastructure, and the environmental level. The cases of pure temporal (T) and spatial (S) analyses are also discussed, comparing the different approaches, illustrating the pros and cons, and describing the opportunities of the S-T combined workflow. The paper specifically focuses on different typologies of S-T processing: data visualization and exploration techniques, clustering, change detection, prediction, and forecasting. The proposed algorithms were all implemented within the R open-source programming language. They can be replicated (and adapted) for other structural monitoring datasets featuring spatio-temporal correlation.

Vibration-based structural health monitoring aims to not only detect the occurrence of the damage but also identify the location of damage. The pseudo-local flexibility method (PLFM) is a vibration-based approach that only requires the identified modal parameters of the structure to perform damage detection. Thus, the cost of constructing a finite-element model of the structure and the modeling error of the finite-element model can be circumvented. In addition, the PLFM is based on the flexibility matrix of the structure, which is practical, because only the first few modes are required to estimate the necessary flexibility matrix and only the first few modes can be identified accurately in real applications. However, the potential damage region that is identified using the PLFM is indicated by the location of the center of the applied virtual forces, but not the potential damage elements. Hence, in this study, an enhanced PLFM (EPLFM) is proposed to improve the resolution of damage localization in the conventional PLFM. The regional rigidity ratios obtained by the PLFM are distributed to each element based on the virtual strain energy corresponding to virtual forces. The damage locations indicated by the EPLFM are marked at each element, and hence, more specific damage locations can be identified by the elements with smaller elemental rigidity ratios. Herein, the present EPLFM was numerically and experimentally validated with a simply supported steel-truss bridge. In the numerical validation, a simplified two-dimensional finite-element model for the truss structure was constructed using SAP2000 software package, and seven damage scenarios and two setups of measurement degrees of freedom (DOF) were investigated. It is found that accurate damage localization of the 2D simply supported truss structure was achieved when both the vertical and horizontal DOFs of all nodes were measured and the virtual force configurations acting on both ends of each element were used. In the in-field experimental validation where the mode-truncation errors and measurement noises were unavoidably introduced, it was observed that the EPLFM could identify the full-cut vertical member at the mid-span or 5/8^th span, even though the cut member was identified in a group with some adjacent un-damaged members.