bluuebunny/crossref_metadata_2025 huggingface dataset:
Floor vibrations from data acquisition with android phones
Authors: Martinelli L , Foti F , Perotti F , Cucchi M
Published: June 2024

Android mobile devices are provided with sensors that allow to monitor several aspects in terms of motion and position of the device; these sensors are hardware-based physical components built into the device, operated by software and mobile apps, providing us with data about motion, temperature, position, and environment in general. Correlation analyses on vibration data recorded on structures are at the base of many methods that allow to extract important modal information from the recorded data. This type of data acquisition demands a high level of time accuracy in order the correlation analyses to be successful. It follows that, whenever data is recorded by different mobile devices, some sort of synchronization between them is required to allow for the necessary precision in time of the recordings. This paper presents the results obtained with a recent solution in which vibration data is picked up with multiple Android mobile phones equipped with accelerometers, and is then transmitted to a server over a wireless connection to be analysed in time on the base of a synchronization procedure. The subject of this study are the recordings of the floor vibrations of a recently constructed building. These are compared with the recordings coming from professional grade acceleration sensors. The capabilities of the proposed recoding technique are discussed on the base of the precision in recovering the mode shapes of a flexible floor from the acceleration records, and also at the light of the relative ease with which Android mobile phones are becoming more available, capable, and less expensive.
Seismic assessment of masonry structures by means of code-based selected records
Authors: Caicedo Daniel , Hussaini Sayed Mohammad Sajad , Karimzadeh Shaghayegh , Bernardo Vasco , Lourenço Paulo B
Published: June 2024

Through the centuries, earthquakes represent one of the main causes of damage and loss of cultural heritage, monumental buildings, and historic centres, affecting the development of many countries worldwide. These kinds of constructions are usually constituted by structural masonry and have shown evidence of good behaviour under vertical static loads, however, given the mechanical properties of this heterogeneous material, such as the high specific mass, low tensile/shear strength, and reduced ductility, makes its use unsuitable in seismic prone areas. This paper conducts a comprehensive study regarding the seismic assessment of an existing masonry structure, using various sets of ground motions selected and fitted to the target elastic response spectrum according to the Eurocode 8 provisions. A comparison between the fitted response spectrum in the period range of 0.2T1-2T1 and in the full period domains is performed.
Measured hospital building vibrations induced by air conditioning systems and elevators
Authors: Rinaldi C , Talebi A , D’Alessio M , Potenza F , Gattulli V
Published: June 2024

A recent large campaign of vibration measurements has been conducted on a hospital building in Italy to perform an operational modal analysis of the structure utilized for model updating. Subsequently, the updated model has been used to carry out a vulnerability analysis of the hospital structural system. The building is composed of 41 structural subsystems separated by technical joints. At the same time, several subsystems are differently interconnected, especially through a roof sustained by large-span wooden beams. Long acceleration time histories have been measured by wireless sensors located at the top level of the building in two days of testing. During the tests conducted in operational conditions, in different locations of the building air conditioning systems and elevators were functioning and they were affecting the measures in the high-frequency content. This work aims to investigate the structural identification of the complex structure, the effectiveness of technical joints, and the influence of the wooden roof connection on the dynamic structural behavior. In pursuing these goals, the main challenge is considering the influence of air conditioning and elevator systems on the natural frequency identification of the structure. Therefore, based on the location of the sensors, the similarities in the geometry, and the vicinity of the sensors to the mechanical equipment, all the sensors have been classified into different groups to observe the dynamic response. Furthermore, an Artificial Neural Network (ANN), trained on numerical model results, is applied to experimental data to establish a relation between increasing prediction error and the influence of the air conditioning system and elevator frequencies.
Dynamics of beams travelled by equally spaced forces via transfer matrix approach
Authors: Migliaccio G. , Ferretti M. , Di Nino S. , Luongo A.
Published: June 2024

This work addresses the dynamic behavior of slender elastic structures travelled by a train of equally spaced transverse forces. Assuming the structures are representable via an Euler-Bernoulli beam, the velocity of the train of forces is constant, and the distance between adjacent forces is equal to an integer submultiple of the beam length, the problem is solved analytically. The analytical solution is based on a linear map, which transforms the system state (positions and velocities of the beam points) at the time instant at which one of the travelling forces leaves the beam from one of its ends, to the system state at the time instant at which the subsequent travelling force in the train leaves the beam from the same end. The reiteration of the linear map provides the time response of the beam. The proposed solution enables the analytical study of the dynamic behavior of the structure and highlights the presence of critical velocities at which divergence phenomena by response accretion may occur. Comparisons with the results of numerical methods confirm the accuracy of the analytical solution.
Train-track-circular tunnel spatially coupled dynamics model and coupling effects of dynamic track-tunnel interactions
Authors: Yang Jianjin , Li Qiuyi , Zhu Shengyang , Zhu Bin , Zhai Wanming
Published: June 2024

The train-induced environmental vibration is an important issue for the rail transport. The study on tunnel vibrations plays an important role in the prediction and evaluation of environmental vibration induced by underground train. A three-dimensional (3D) time-domain train-track-tunnel-soil coupled dynamics model is proposed in this study for the underground circular tunnel commonly used in subway. In the model, the tunnel lining and surrounding grouting area are modelled as a cylindrical dual-layer thin shell supported by cylindrical viscoelastic layer which is used to describe the influences of soil. Subsequently, the partial differential equations of the shell are transformed into ordinary differential ones by using semi-analytic modelling method. Then, the model of tunnel lining and grouting area is coupled with the train-track spatially coupling dynamics model through the track-tunnel dynamic interactions, forming the 3D train-track-tunnel coupled dynamics model. The accuracy and reliability of the proposed model are verified by the field test results. Finally, the model is employed to study the influence of coupled solving of train-track subsystem and tunnel subsystem. Results show that the proposed model can achieve real-time dynamics simulation of the train-track-tunnel spatially coupled system on a desktop computer. The coupling effect between the train-track subsystem and the tunnel subsystem has an evident impact on the dynamic responses of the train, track, and tunnel subsystems.
A numerical model based on moving mesh FE for vehicle bridge interaction
Authors: Greco Fabrizio , Lonetti Paolo , Pascuzzo Arturo , Sansone Giulia
Published: June 2024

The main purpose of the present study is to investigate the effects of damage phenomena on the structural behavior of Reinforced Concrete (RC) bridges and related identification procedures. To this end, an effective FE numerical model able to analyze the structural response, in presence of different damage scenarios, is implemented. Moreover, the influence of moving loads on the damage behavior is also considered by means of the vehicle-bridge interaction (VBI) FE model. The combination of the structural model and the vehicle mechanical system provides an advanced numerical model able to simulate the dynamic interaction between the bridge and the moving vehicle. This problem is managed by using the moving mesh technique. In particular, the formulation “Arbitrary Lagrangian-Eulerian” (ALE) provides an accurate description of the interaction between two systems. ALE approach is based on a fixed-referential system and moving coordinate variables, representing the positions of the computational nodes during the application of the moving loads. Vibrational analyses in terms of damage scenarios are presented to verify how the presence of material discontinuities affects the natural frequencies of the structural system. Moreover, results in terms of dynamic amplification factor for typical design bridge variables, in presence of damage phenomena and moving loads, are also developed. Finally, a discussion on the impact of the proposed results on the dynamic identification procedures is provided.
Nonlinear Earthquake Response Analysis Using Causal Hysteretic Damping and Extended Rayleigh Damping
Authors: Nakamura Naohiro , Nabeshima Kunihiko , Mogi Yoshihiro , Ota Akira
Published: June 2024

In dynamic design, damping considerably influences the response of structures, so it must be set appropriately. Stiffness-proportional damping is generally used as an inherent damping model, but this model tends to overestimate the damping of higher-order modes. Certain models can evaluate the damping of higher-order modes, such as modal damping and Rayleigh damping. One of the authors proposed causal hysteresis damping and extended Rayleigh damping as damping models with a low frequency dependence of the damping ratio. However, although the use of these models for linear analysis has been studied, their application to nonlinear analysis has not been sufficiently studied. Therefore, in this paper, the effect of these inherent damping models on the response characteristics of structures was evaluated to obtain basic data for future research. Specifically, stiffness-proportional damping, Rayleigh damping, modal damping, causal hysteresis damping, and extended Rayleigh damping were studied. Their response characteristics were evaluated and compared. These damping types for nonlinear analysis could be divided into the initial type and the tangential type, depending on how to handle changes in stiffness. These properties were also examined.
Novel three-dimensional non-self-intersecting plots for describing the dynamics of structural systems and their hysteresis
Authors: Gallo Patricio Quintana
Published: June 2024

In earthquake structural dynamics, because the ground acceleration term (external excitation) explicitly depends on the time, the equation of motion of a single-degree-of-freedom (SDOF) system constitutes a nonautonomous 2-dimensional (2D) dynamical system. Thus, the true dimension of the equivalent autonomous dynamical system is three, such that the state is 3-dimensional (3D) and, naturally, so is the phase-space where it should be visualized. The 2D plots of two state variables of a 2D-nonautonomous system, unlike for autonomous counterparts, are self-intersecting. The self-intersecting nature of these 2D plots represents a barrier for a proper visualization of the system’s dynamics and render them unsatisfactory for conducting graphical qualitative evaluations. To cope with such a disadvantage, this paper presents novel 3D non-self-intersecting plots for describing the dynamics of SDOF systems, including those with hysteretic restoring force, as a 3D-autonomous dynamical system. The 3D curves comprise plots incorporating the time as an additional variable as well as others of the type [velocity, restoring force, displacement], which, somehow, resemble Lorentz’s ‘butterfly’ 3D plot obtained for meteorology. The paper uses examples of problems having harmonic and earthquake-induced actions (accelerations) typically encountered in dynamics of structures. In addition, the paper presents 3D curves of the measured force-displacement hysteresis loops of reinforced concrete beam-column joint assemblies tested under quasi-static loading regime. It is shown that the 3D plots allow visualizing relationships and behaviours that cannot be identified using the 2D counterparts. It is thought that the novel 3D curves can be of much use in structural/seismic and mechanical engineering.
On a nonlinear behavior of an aeroelastic system with quartic stiffness
Authors: Machado Raphaela Carvalho , Ribeiro Maurício Aparecido , Varanis Marcus Vinicius Monteiro , Nabarrete Airton , Balthazar José Manoel
Published: June 2024

This research performs a nonlinear analysis of a typical section airfoil limited to two degrees of freedom emphasizing the evaluation of the effects of a quartic structural stiffness on dynamic responses. Analytical studies are presented based on a simulated model. First, the influence of the quartic term of nonlinear structural stiffness in spring moment is evaluated. Then, phase portraits are presented as a function of freestream velocity, and a time domain decomposition of time histories is performed to identify the limit cycle frequency. Additionally, it maps the region of limit cycle oscillations (LCOs). Furthermore, the aim of this work is to characterize the nonlinear aeroelastic response.
An asymptotic approximation of the chattering time for the rocking problem
Authors: Giouvanidis Anastasios I. , Dimitrakopoulos Elias G. , Lourenço Paulo B.
Published: June 2024

The dynamic behaviour of a freestanding block rocking on a rigid base when subjected to a strong ground excitation is a classical problem of nonlinear dynamics that has recently gained considerable momentum. However, when a rocking block is subjected to a low amplitude (i.e. weak) ground motion has drawn little attention due to the belief that it has marginal effect on the response trajectory. Despite its apparent structural simplicity, a rocking block undergoes complex nonlinear and nonsmooth dynamics phenomena under both low and high amplitude ground motions. This study focuses on one of the least investigated nonlinear phenomena of rocking dynamics that might appear during the low amplitude forced oscillations of a block, called chattering. Chattering can be complete or incomplete. Complete chattering occurs when a block undergoes a theoretically infinite sequence of impacts in finite time, that eventually bring the block to the state of persistent (continuous) contact even under a nonzero excitation. On the contrary, incomplete chattering does not bring the block to rest after a theoretically infinite number of impacts. A challenging problem that arises during complete chattering is the accurate estimation of the time needed for the block to reach the state of persistent (continuous) contact, i.e. chattering time. Thus, this paper presents an iterative algorithm that approximates chattering time using asymptotic analysis and perturbation methods.
The seismic responses of the Post-Tensioned frame with Sliding Keys on Inclined Deflecting-cantilevers device (the PT-SKID frame)
Authors: Zhang Y , De Risi R , Alexander N A
Published: June 2024

Recently, a novel Sliding Keys on Inclined Deflecting-cantilevers (SKID) device was proposed for application with Post-Tensioned (PT) frames. The SKID device features a triangular-shaped hysteretic curve, which enables it to provide hysteretic damping with a zero activation threshold. The PT-SKID frame is characterised by a dual-triangular-flag-shaped hysteretic curve with full self-centring capability. The properties of the PT frame and the SKID device have been theoretically investigated and physically demonstrated. In this paper, the hysteretic curve of the PT-SKID frame is discussed first. There are three core parameters for the SKID device: friction coefficient μ, slope angle β, and cantilever bar stiffness k
s. Then, the influence of these parameters on the seismic response of the PT-SKID frames is investigated by numerically testing 560 PT-SKID frames in OpenSees. Three pairs of spectrum-matched ground motions are used in the analysis. The results indicate that SKID devices with a small β and large k
SKID and μ have a better peak drift ratio control. However, larger sections have to be used for the structural components supporting the SKID devices, as a larger base shear is generated.
Uncertainty parameters of the floor response spectrum in a seismically isolated structure
Authors: Lee S J , Kim S Y , Byun Y J , Kim J H
Published: June 2024

To evaluate the earthquake safety of the equipment in structures, it is essential to analyze the Floor Response Spectrum (FRS). FRS has a peak value at a frequency corresponding to the structural vibration mode; however, the frequency and amplitude at the peak can vary because of many uncertain parameters. Several seismic design criteria exist for FRS peak-broadening in fixed-base structures. However, no criteria for constructing a design FRS for seismically isolated structures have been suggested. The FRS of isolated structures may change because of the major uncertainty parameter of the isolator, which is the shear stiffness of the isolator, and several other uncertainty parameters caused by the nonlinear behavior of the isolators. This study evaluated the effects of the initial stiffness of the bilinear curve of isolators and the variation in the effective stiffness based on the input ground motion intensity and intense motion duration. An analysis of a simplified structural model for an isolated base structure confirmed that the FRS at the frequency of the structural mode was amplified and shifted. The uncertainty in the initial stiffness of the isolators was found to significantly affect the shape of the FRS. The variations caused by the intensity and duration of the input ground motion were also evaluated. These results suggest several considerations for generating FRS for seismically isolated structures.
Finite element model updating of a ferry dock bridge
Authors: Siedziako B , Nord T S , Fenerci A
Published: June 2024

An accurate finite element representation of a real structure allows designers to investigate how it will perform over time when exposed to external loading in order to ensure economical de-sign, structural safety, and a more accurate estimation of the remaining useful life of that structure. For structures such as ferry dock bridges that have been little studied in the past, there are many uncertainties related to properly modelling in finite element software. In such cases, a finite element updating technique can shed a light on uncertain parameters. This paper presents results from the finite element model updating of the Rykkjem ferry dock bridge in Norway based on vibration test data with an emphasis on the estimation of vertical stiffness provided by the lifting towers.
Damage detection in 3D printed plates using ultrasonic wave propagation supported with weighted root mean square calculation and wavefield curvature imaging
Authors: Wojtczak E , Rucka M , Andrzejewska A
Published: June 2024

3D printing (additive manufacturing, AM) is a promising approach to producing light and strong structures with many successful applications, e.g., in dentistry and orthopaedics. Many types of filaments differing in mechanical properties can be used to produce 3D printed structures, including polymers, metals or ceramics. Due to the simplicity of the manufacturing process, biodegradable polymers are widely used, e.g., polylactide (polylactide – PLA) with a practical application for manufacturing complex-shaped elements. The current work dealt with the application of ultrasonic guided waves for non-destructive damage detection and imaging in AM plates. Two specimens with defects were manufactured from PLA filament. Different sizes of damage areas were considered. The specimens were tested using the guided wave propagation technique. The waves were excited using a PZT actuator and recorded contactless with the scanning laser Doppler vibrometry (SLDV) in a set of points located at one surface of the sample. The collected signals were processed with two methods. The first was the weighted root mean square (WRMS) algorithm. Different values of the calculation parameters, namely, averaging time and weighting factor were considered. The WRMS damage maps for both samples were prepared to differentiate between intact and damaged areas. The second approach was wavefield curvature imaging (WCI) which allowed the determination of damage maps based on the curvature of the wavefront. The compensation of wave signals was performed to enhance the quality of results. It was observed that the size of the defect strongly influenced the efficiency of imaging with both methods. The limitations of the proposed approaches were characterized. The presented results confirmed that guided waves are promising for non-destructive damage imaging in AM elements.
Estimation of bolt tension using transverse natural frequencies of the shank and protruding end
Authors: Rashid D. S. , Giorgio-Serchi F. , Hosoya N. , Garcia Cava D.
Published: June 2024

Bolted connections are crucial components in mechanical systems with the purpose of assembling different components. However, the tension of bolts may decrease due to recursive loading and environmental conditions. Monitoring the tension of bolted connections can help prevent failures and identify damage at an early stage. Vibration-based techniques have shown promising results for evaluating the tension present in a bolted connection. However, previous studies have neglected the effect of the protruding end, which can significantly affect the dynamic response of the bolted connection. In this study, a novel extended model based on an Euler-Bernoulli beam is proposed that accurately captures the effects of the protruding end on the estimation of the transverse natural frequency of the bolt. The proposed technique incorporating the transversal natural frequencies associated with the protruding end of the bolted connection provides a more representative frequency response of the bolted connection. The results show that there is a significant shift in the natural frequencies at higher modes which are associated with the protruding end. The findings have important implications for the monitoring of bolted connections and provide a basis for more accurate and reliable health and performance assessments. Further research could focus on the validation of the proposed model using experimental data and its application in practical settings.
Accelerometer configuration assessment of Milad Tower utilizing operational modal analysis
Authors: Sadeqi Amirali , Esfandiari Akbar , Behboodi Saeed , Sanayei Masoud
Published: June 2024

In operational modal analysis, the observability and quality of the extracted modal parameters, apart from the characteristics of structures, loads, and noise, largely depend on the data acquisition system. Especially in large-scale structures, because of the low frequency- and low amplitude of vibration, the configuration and arrangement of the sensors are of particular interest. Milad Tower, with a height of 435m in Tehran, is the sixth tallest telecommunication tower in the world. The authors have previously identified the tower’s modal parameters by developing an automated data-driven subspace approach and investigated the long-term variations of modal parameters for structural health monitoring purposes. This paper adopts this identification approach to a Milad Tower finite element model subjected to random and seismic loadings. The identified modal parameters are compared with those obtained based on real acceleration records. The MEMS accelerometers’ performance is investigated by stabilizing identified natural frequencies for different setups and scenarios. Also, the performance of various accelerometers temporarily mounted on the tower is compared, and a response signal measured under the most recent earthquake in Tehran is presented. The qualitative and quantitative assessments of the sensors are discussed, and required improvements are recommended.
Quantum Machine Learning for Structural Health Monitoring
Authors: Yaghoubi Vahid
Published: June 2024

Nowadays, employing deep learning for Structural Health Monitoring is a common practice. However, one of the main challenges here is the lack of data. Several methods have been developed to address this issue. Quantum machine learning is known to be trained faster and with less data, therefore, it could be a suitable option to be used for this purpose. However, since at the current stage limited numbers of qubits can remain stable at the same time, hybrid quantum-classical deep learning approaches can be a replacement. In this study, the benefit of incorporating a quantum layer into a classical deep learner for detecting damage is investigated. For this purpose, a deep learning model with and without a quantum layer is used to predict damage in a wind turbine blade by using ultrasonic inspection data. The results indicate the benefit of employing hybrid quantum-classical ML in detecting damage.
A Vehicle Bridge Interaction based approach for the monitoring of bridges through an electric mobile platform
Authors: Fiandaca D , Denoël V , Pirrotta A
Published: June 2024

The main purpose of the Structural Health Monitoring (SHM) techniques applied in bridges is to monitor many structural parameters to prevent serious damage that may eventually lead to collapse of the entire structure. To date, Operational Modal Analysis (OMA) methods are widely seen as the most reliable SHM technique. These encompass a series of procedures for deriving the modal parameters of a structure using the data acquired under its operating conditions, without recording the external excitation. However, traditional OMA methods generally require expensive setup and time-consuming procedures. With the aim of overcoming these issues, in this paper, an innovative Vehicle-Bridge Interaction (VBI) based approach is investigated as a low-cost monitoring system for the identification of the structural modal parameters. These are obtained from the analysis in the frequency domain of the measured vehicle’s vibration response during several passages on the structure. Therefore, the proposed approach has been adopted in an experimental campaign on a pedestrian bridge in the city of Palermo (Italy). In particular, a very low-cost setup comprising a scaled-up electric vehicle as a mobile platform and few accelerometers has been used.
High-performance beam finite element for predictive response in monitoring existing bridges
Authors: Fusco D , Rinaldi C , Addessi D , Gattulli V
Published: June 2024

In recent years, several advanced technologies, such as Artificial Intelligence (AI) techniques, have been developed to automate inspections and monitoring processes of existing bridges. In this context, the efficiency of computational models is crucial in model updating for monitoring systems and training neural networks. Although the nonlinear structural response of the bridges can be efficiently analysed through two-dimensional and three-dimensional finite element (FE) models, these commonly require high computational efforts. This work adopts a high-performance beam finite element based on a damage-plasticity model, implemented in the OpenSees framework, for prestressed reinforced concrete girders. The beam FE relies on a force-based (FB) formulation which is more efficient than the classical displacement-based approach. The constitutive law of the concrete fibers is based on a plastic-damage model, which considers two different damage parameters for the compression and tensile behaviour to take into account the re-closure of the tensile cracks. Dynamic responses in both linear and nonlinear regime are simulated under white noise excitation. ANNs are trained in a subset of the predicted responses in the linear range and the trained network is used to simulate the high amplitude response in which nonlinear behaviour is experienced. Interesting results are acquired useful for further investigations.
Structural health monitoring of a curved roadway bridge: model calibration and collapse simulation aspects
Authors: Farneti Elisabetta , Meoni Andrea , Natali Agnese , Celati Simone , Cavalagli Nicola , Salvatore Walter , Ubertini Filippo
Published: June 2024

This work aims to explore the potential of the Applied Element Method (AEM) for structural analysis application in the framework of bridge monitoring, focusing in particular on the aspects of model calibration and simulation of the collapse behaviour. An AEM model of a curved roadway bridge undergoing slow landslide-induced movements was built and calibrated by using the results of ambient vibration testing and modal identification. A simulation under increasing displacements caused by the landslide was carried out, predicting the deformation evolution of the bridge and comparing it with the current state of damage observed on site.
Cases of sensor fault assessment
Authors: Lydakis E , Amador S D R , Koss H , Tarpø M , Brincker R
Published: June 2024

The field of structural health monitoring (SHM) is based on collecting data, and according to that, useful information about the monitored structures is obtained. Therefore, it is essential that the signals from the sensors used in the monitoring campaign can be trusted. However, some of these sensors will sometimes fail or will, at least, pick up excessive noise that might influence the quality of the information extracted from the data. In this paper, a new technique of sensor fault detection is illustrated that is based on constraints between multiple output signals from the monitored structures.
Experimental machine learning approach for building structural health monitoring application
Authors: Mghazli Mohamed Oualid , Zoubir Zineb , Rallu Antoine , Lamdouar Nouzha , Elmankibi Mohamed
Published: June 2024

The research and development field of structural health monitoring is evolving, and as a result, it now provides choices for disaster prevention and life cycle extension. This can help boost structural safety and infrastructures resiliency. Researchers have taken an interest in the use of machine learning techniques for these applications as a result of the promising outcomes that those approaches have delivered. In spite of this, damage detection applications necessitate the use of sophisticated and reliable data-driven enabled technologies. This is because of the complex behavior of structures that is notoriously difficult to track. In this investigation, triaxial accelerometers are used for data acquisition purposes in order to monitor and examine the structural performance of an experimental four-story building frame when subjected to a variety of structural configurations. The effectiveness of supervised machine learning algorithms was analyzed and compared to that of unsupervised learning approaches. In spite of the fact that supervised models have demonstrated good performances for the detection of initially established anomalies, they have only partially exhibited performances for newly produced damage patterns, which restricts their application in real life cases. The results obtained by the unsupervised algorithms, on the other hand, were comparable and satisfying, revealing essential capabilities for damage detection applications.
Feasibility study on monitoring the structural health of a transmission tower with controlled damage scenarios
Authors: Bel-Hadj Yacine , Fernandes Adelmo , Weijtjens Wout , Devriendt Christof
Published: June 2024

The Smart Tower project, a collaboration between Vrije Universiteit Brussel (VUB) and Elia, aims to explore the application of Structural Health Monitoring (SHM) for transmission towers. The tower was equipped with a variety of sensors, including Strain Gauges (SG), Resistance Temperature Detectors (RTD), Piezoelectric Transducers (PZT), accelerometers (ACC), and Acoustic Emission (AE) sensors. It was then subjected to controlled damage scenarios to simulate typical failure modes. The study analyzed the collected sensor data to assess its suitability for SHM. The results revealed that the acceleration data features were sensitive to the simulated damage, with modal parameters identifying almost all relevant damage instances. However, minor damage to specific areas, such as bolt loosening, affected only high-frequency modes and required sensors in close proximity to the damage. Conversely, significant damage, like bar removal, impacted low-frequency modes and was detectable by all accelerometers. Although the PZT sensor was able to identify multiple modes, it could not detect the simulated damage due to its location. These findings illustrate the potential of SHM for transmission towers and underscore the importance of sensor placement in detecting specific types of damage.
Investigation of modal damage-sensitive features of a scaled three-storey steel frame for vibration-based damage detection.
Authors: Marafini Francesca , Zini Giacomo , Barontini Alberto , Monchetti Silvia , Betti Michele , Bartoli Gianni , Mendes Nuno , Cicirello Alice
Published: June 2024

The application of vibration-based Structural Health Monitoring (SHM) for damage detection is characterised by three fundamental aspects: the features extracted as representative of the structural condition that can be directly linked to some form of damage, the metrics selected as novelty or damage index, and the statistical model or classifier built to identify underlying patterns indicative of changes in the structure’s state. Focusing on the first step to improve the performance of vibration-based SHM strategies, the extracted features should be robust to noise, sensitive to the presence of a specific type of damage. Further, damage should induce patterns that are distinguishable from environmental and operational variabilities and other forms of damage such as ageing phenomena. In this paper, the problem is framed as an outlier detection problem and the the use of different modal parameters as Damage Sensitive Features (DSFs) is investigated, evaluating them based on the detection performance of an unsupervised One-Class Support Vector Machine (OCSVM) classifier. In particular, an artificial dataset is generated from the calibrated numerical model of a three-storey steel frame structure in different damage scenarios. The methodology is validated against available experimental data. For the case investigated the natural frequencies were sensitive to damage and robust to noise.
Dynamic Characterization of a Full-Scale Three-Story Mass Timber Building Structure
Authors: Uarac P Patricio A. , Barbosa Andre R. , Sinha Arijit , Simpson Barbara G. , Ho Tu X.
Published: June 2024

A veneer-based engineered wood product known as Mass Ply Panels (MPP) was recently introduced and certified per ANSI-PRG 320. A full-scale three-story mass timber building structure was constructed and tested at Oregon State University to demonstrate the potential of MPP in the design of resilient, structural lateral force-resisting systems. The building structure comprised MPP diaphragms, laminated veneer lumber (LVL) beams and columns, and an MPP rocking wall design. Two opportunistic vibration tests were performed to charac-terize the dynamic properties of the structure. First, an implosion of a stadium within 600 m of the building location was used as the main excitation source, during which bi-directional horizontal acceleration data were collected for approximately 18 seconds. Second, an ambient vibration test was conducted to collect horizontal acceleration data for one hour. In both tests, sixteen accelerometers were used to measure the response of the structure. Modal features were extracted using an output-only method and compared with the estimates from a finite element model. Lessons learned can be used to inform future modeling efforts of a mass timber building to be tested on the Natural Hazards Engineering Research Infrastructure (NHERI) Experimental Facility at the University of California San Diego high-performance outdoor shake table.
An experimental study on the performance of virtual sensing using optimal and regular physical sensors placement
Authors: Bourdalos D M , Zisopoulos S S , Tcherniak D , Sakellariou J S
Published: June 2024

Vibration analysis is highly beneficial in a variety of engineering areas. However, in many real-world applications, vibration data acquisition may be challenging due to the accessibility of the desired sensor locations. It can be also costly if many measurement points are required. Consequently, a few vibration estimation methods have been proposed, which are referred to as “virtual sensing”. Virtual sensing claims to be able to replace a physical sensor with a virtual one, whose signal should closely resemble the signal from the physical sensor if it was placed at the same location. The signal from such a virtual sensor is estimated based on a numerical model of the structure under test and data from a number of physical sensors. In this study, the well-known modal expansion and decomposition-based virtual sensing method is examined, and its sensitivity to the amount and location of physical sensors is explored. Two sensor placement scenarios are considered: (i) the most common scenario where the physical sensors are placed in the nodes of a regular mesh, and (ii) where the sensors configuration is generated by the optimal sensors placement (OSP) algorithm. The experimental examination is performed on a simple test structure (rectangular aluminum plate) using time and frequency domain performance indicators for three excitation profiles (pseudo-random, burst pseudorandom, and sinusoidal). The results demonstrate that the use of OSP significantly improves the performance of virtual sensing.
Indirect assessment of tension force in cables equipped with TMDs
Authors: Pomaranzi G. , Argentini T. , Zasso A.
Published: June 2024

In this paper, an indirect method to obtain the actual tension force in stay cables is presented. It is based on a combined experimental and numerical approach, where the experimental measurement of the first natural frequency of the cable is combined with a FE model of the cable to finally obtain an estimate of the actual tension force. The method is suitable to be applied to cables eventually equipped with tuned mass dampers. It is here presented referred to an application case, the stays of the Hovenring Bridge. Being those cables endowed with two tuned mass dampers, the well-established indirect method based on the string theory cannot be applied to the present case. Therefore a new approach is proposed: it makes advantage of a FE model of the cable, made by equivalent tensioned beam elements and includes the effects of the dampers through equivalent mass-spring-damper systems. A complete description of the method is presented along with its validation through a comparison with a direct measurement of the tension force in 4 cables.
Quantifying uncertainties of empirical damping estimates from full-scale responses of a polar vessel
Authors: Van Zijl C M , Bekker A
Published: June 2024

Damping is critical for accurately predicting wave-induced ship vibrations. Operational modal analysis (OMA) is useful for identifying damping estimates from measured outputs. In reality, periodic and non-stationary wave excitation violates fundamental OMA assumptions which, along with noisy finite output measurements, produce bias and random errors. To address uncertainty in empirical damping estimates of the two-node vertical bending (2nVB) modal damping of a polar vessel, OMA is performed on full-scale measurements obtained during dedicated open water test sequences. The effect of user-selected block size and model order for the data-driven stochastic subspace identification algorithm is investigated. Random errors in damping estimates generally decrease with increasing ship speed possibly due to higher signal-to-noise ratios in the higher speed cases. Further, higher encountered wave lengths, which occur at low ship speeds, may increase periodic wave excitation of the vessel and requires higher model orders to eliminate bias. In general, block sizes of 40 to 80, and model orders ≥ 80 yielded the most stable estimates. Uncertainty in damping estimates are estimated using a first-order sensitivity analysis and, even for the most stable estimates, relatively large random errors are obtained. A conservative estimate for the 2nVB damping is ≤ 2%. Damping estimates are observed to decrease with increasing ship speed possibly due to hydro-elastic effects.
Effect of eccentricity on sensing in spider web inspired cable nets
Authors: Masmeijer T.C.P. , Méndez Echenagucia T. , Slavič J. , Loendersloot R. , Habtour E.
Published: June 2024

Spider webs are multifunctional tools that, besides capturing prey, monitor vibration in the web to localize the prey. Spiders obtain an evolutionary benefit from improving monitoring because better information processing leads to more successful captures, leading to higher chances for survival. Based on this, combined with the costly energy requirements of signaling, biologists observe that the spider’s web operates as an extended cognition of the spider’s central nervous system. Here an extended cognition means that the web filters signals to make decoding information easier. Spider webs contain characteristic design patterns, such as an eccentric location of the central hub. This paper investigates how this eccentricity enables a spatially dependent dynamic response of web-like structures, potentially enabling extended cognition. Modeling consists of modal analyses in a Finite Elements Model on web-like structures where a mass is sequentially moved across all nodes. This yields the natural frequencies of the structure depending on the mass location. Analysis shows that the natural frequency forms patterns based on the mass location, and more importantly, it shows how these patterns become more intricate by including eccentricity. The resulting maximum change in natural frequency grows as the eccentricity in the design grows. This shows that eccentricity influences the dynamic response, hence indicating that eccentricity could enable the web’s extended cognition. The numerical model of spider web-inspired structures can investigate the effects of the geometry on any network-like structures besides spider webs. The authors believe the model can be utilized for impact/anomaly detection on network-like structures.
Structural damage inverse detection from noisy vibration measurement with physics-informed neural networks
Authors: Yuan Lei , Ni Yi-Qing , Rui En-Ze , Zhang Weijia
Published: June 2024

Structural damage detection is an inverse problem to identify and quantify structural damage from measurement data by discovering the variation of structural mechanical parameters. Recently, a novel deep learning framework named physics-informed neural networks (PINNs) has been proposed and successfully applied to solve inverse problems of various linear/nonlinear partial differential equations (PDEs) by integrating physical information such as governing equations as prior information. In this study, we propose a PINN-based framework to exploit a novel method of structural damage detection. Specifically, a deep neural network model as the core of PINNs is built to predict the dynamic response in different degrees of freedom. The unknown mechanical parameters are initialized randomly and updated together with the neural network model parameters. Then, the structural physics model is embedded by calculating the residuals of governing equations as parts of the loss function. The residual between the predicted dynamic response and measurement data is also used as another part of the loss function. A two-step optimization strategy is proposed to obtain the best unknown parameter values that can fit the measurement data and governing equations simultaneously. Through numerical experiments of a single-degree-of-freedom system, we demonstrate that the proposed method can successfully identify potential structural mechanical parameters and quantitatively detect structural damage. The influence of sparsity and noise in the measurement data on the detection results is also analysed.
Identification of closely spaced modes in space truss structures as base for the determination of member normal forces
Authors: Abdelnour Mena , Zabel Volkmar
Published: June 2024

Space truss structures are a type of versatile lightweight systems that are applied in different fields such as civil and aerospace engineering. For some of these systems that were built decades ago, for example as roof structures for relatively large spans, not all proofs regarding the load-bearing capacity and serviceability can be satisfied according to current codes of practice as the requirements may have changed since the initial design phase of these systems. In such cases, it may become necessary to obtain the actual stress status of the structural skeleton based on experimental investigations. From the identification of forces in many members, a general stress status can be derived, which leads to an estimation of the current status and possible reserves in the load-bearing capacity of space truss structures. One option for the identification of element forces is their identification from modal parameters of the structure. In literature, the main focus has been put so far on the identification of longitudinal forces and boundary conditions inside a single tension member/cable utilising vibration-based methods. Very good results were also reported for the identification of longitudinal forces in elements of two-dimensional truss structures of moderate complexity. Fewer studies documented in the literature concentrate on space truss structures. For these modular systems consisting of standardized elements, not only the identification of element forces based on identified modal parameters is very challenging, but also the modal identification itself. The latter is often caused by the situation that space truss structures often have numerous modes characterised by both local and global vibrations at close natural frequencies. The study presented in this contribution focuses on the identification of mode shapes and natural frequencies required as a prerequisite for a model based approach to estimate the stress state of the complete considered space truss structure. Apart from aspects with respect to the instrumentation for modal testing, specific issues within a parametric modal analysis such as the choice of model order are discussed. It is explained by means of a case study, why the minimal model order to be taken into account in the modal identification of space truss structures can become considerably higher than those commonly applied in the analysis of, for example, bridge structures, towers or floor systems. These descriptions are illustrated by the results of both numerical and experimental analyses.