bluuebunny/crossref_metadata_2025 huggingface dataset:
Vision-based dynamic monitoring of a steel footbridge
Authors: Buoli E. , Bassoli E. , Eslami Varzaneh G. , Ponsi F. , Vincenzi L.
Published: June 2024

The increasing slenderness and lightness of modern footbridges make the vibration serviceability assessment a key aspect for their design and maintenance. A promising approach to the characterization of footbridge dynamic behaviour is represented by computer vision-based techniques. In contrast to traditional monitoring systems relied on dense sensor networks, computer vision-based monitoring requires the installation of one or more cameras together with, if necessary, some targets on the monitored structure. The article presents some preliminary results of the short-term dynamic monitoring of a steel footbridge based on computer vision techniques. The structural deflection caused by a jumping pedestrian was recorded from three cameras in different measurement positions. The post-processing of the video frames is presented and discussed in the article. Special attention is paid to the use of circular targets placed on the footbridge, which allowed for the identification of deflections with sub-pixel resolution. A traditional accelerometer based monitoring system is also installed on the footbridge for validation purposes. Displacements evaluated through a double integration of the measured accelerations are compared to those obtained from the image processing. Results demonstrate the high potential of computer vision-based systems for the monitoring of structures and infrastructures.
Determination of cable tension force in pedestrian suspension bridge short hangers based on finite element model updating
Authors: Ereiz Suzana , Duvnjak Ivan , Pajan Jurica , Bartolac Marko , Damjanović Domagoj
Published: June 2024

The hangers are the important element on suspension bridges that transfer the forces from the deck to the main cable. To verify their capacity and identify possible risks, the forces transferred by the hangers and the corresponding tension must be determined. However, this is often done using standard equations for determining cable forces. Due to the different lengths of the hangers and the way in which their tensioning is achieved, the effects of boundary conditions occur that need to be considered and that require an update of the finite element model at the local level (when the whole bridge structure is observed). This paper presents a method for determining the cable tension of hangers that combines the experimentally determined dynamic properties (natural frequencies and mode shapes) and the numerical model updating. In addition to the usual approach based on the determination of the natural frequency of hangers, this paper presents an approach based on the mode shapes of the hangers. Special attention is paid to the boundary conditions coefficient. The method is applied on suspension bridge case study.
Evaluation of Evacuation Possibility During Earthquake based on Seismic Response Analysis Model of Human Body Considering Walking and Falling
Authors: Sakuma Haruki , Hida Takenori
Published: June 2024

In the past massive earthquakes, many people suffered severe damage. Among them, not a few people suffered fall-induced injury because of evacuation actions during the shaking. Therefore, it is important to estimate the human response to shaking and the possibility of evacuation to evaluate human injury during an earthquake. Considering these background, this study proposes the evaluation method of fall and walking difficulty during an earthquake considering human behavior by constructing the seismic response analysis model of human body. First, the shaking table tests with human subject were conducted to observe the human behavior under strong motion excitation. Then the human body model considering walking and falling was developed based on a cart-type double inverted pendulum with feedback control system. In order to set appropriate feedback gains of the control system, the displacement and velocity of head of the human body model was compared to those of the human subject of the shaking table test. Then, the behavior and mechanism of falling of the human due to walking during shaking was investigated by inputting the strong motion record, which observed during 1995 Hyogo-ken Nanbu earthquake, to the human body model. Next, sinusoidal waves of various amplitudes and periods were input to the human body model to clarify the relationship between the vibration characteristics of the input motion and the response of the human body. Then, the evaluation method for evacuation possibility during an earthquake was proposed. Finally, the validity of the proposed method was investigated by comparing the behavior of the human body excited by sinusoidal wave with that excited by an earthquake shaking.
Structural assessment of a half-built building by vibration tests
Authors: He H , Meijers W
Published: June 2024

Structural quality of a half-built building was investigated by different experimental approaches. Vibration test was specially employed as it is a non-destructive method, which can be performed without the interruption of the construction. The principle of the tests is identifying the dynamic behaviour of the structural element by the measurement of structure response (acceleration or velocity) under certain excitations. Various floor locations are chosen for the evaluation of specific structural elements. For the comparison and verification purpose, numerical and analytical methods are also used for structural analysis. By the comparison between theoretical estimations and tested results on a reference structure, different methods are verified. It shows the eigenfrequency of (complex) structural elements/systems can be estimated accurately with relatively simple analytical formulas. Therefore, the analytical method was further used for the comparison with the vibration tests and the assessment of structural quality.
Dynamic amplifications in railway transition zones: investigation of key phenomena
Authors: Jain A. , van Dalen K.N. , Steenbergen M.J.M.M. , Metrikine A.V.
Published: June 2024

The railway transition zone where the track transitions from a ballasted track to a slab track, is a crucial area that can experience amplified dynamic responses. This work aims to develop a deeper insight into the mechanisms leading to the amplified dynamic response in railway transition zones. The study employs a finite element model to investigate the amplification of total strain energy due to the phenomena of reflection and redistribution of energy close to the transition interface. The results of the study are obtained for three case studies involving non-reflecting boundary (representing an energy sink) and homogeneous material along the vertical direction of the track, and the responses are studied for individual and combined effects in comparison to a benchmark case. The findings of the study show that eliminating the phenomena results in no dynamic amplification in total strain energy in railway transition zones. The conclusion highlights the importance of understanding these phenomena in order to design an efficient railway transition structure.
Active mitigation of self-excited vibrations of a magnetic track brake
Authors: Ebner Bernhard , Tippelt Daniel , Edelmann Johannes , Plöchl Manfred
Published: June 2024

Magnetic track brakes (mtbs) are additional braking systems used in railway vehicles at emergency situations and low adhesion conditions. Operation at low velocities can cause harmful self-excited vibrations, which must be avoided at all circumstances. Few passive countermeasures are already published, but active vibration control of an mtb lacks in literature so far. In this paper an active vibration control to diminish self-excited vibrations, based on reducing the energy, drawn by the oscillating system, is studied. Considering a minimal model of the mtb, the energy input depends on the electromagnetic-mechanical coupling and the friction force in the mtb—rail contact. The obtained equation of this energy reveal a dependency of the phase shift, between magnetic flux and the oscillatory mechanical motion. A control law for the input voltage is obtained to reach a specific phase shift reducing the energy input and oscillating amplitudes.
Description of impact energy dissipation in fibrous composite materials using a nonlinear dynamic degenerate model
Authors: Olaleye Kayode , Pyka Dariusz , Bocian Mirosław , Jamroziak Krzysztof
Published: June 2024

To design effective energy-absorbing shields made of modern composite materials (e.g., fibrous composite panels), it is necessary to use deformable materials whose important feature is the largest possible dissipation of impact energy. Rheological properties of these materials differ significantly from dissipative and elastic properties described by the Hooke and Kelvin linear models. Moreover, the range of material deformation at the place of impact is so wide that the above-mentioned models are not sufficient to properly describe the process of energy dissipation. The value of dissipated energy is also important for the determination of the lifespan of dissipative and elastic elements subjected to cyclic dynamic loading and made of modern structural materials (fatigue phenomena). The authors proposed a dynamic model in which the rheological properties of the material are described by two spring parameters c, c
0 and one parameter of viscous damping k
0 in the configuration used in the so-called rheological standard model (Zener model). In addition, the model introduces the element of dry friction described by the appropriate function h(x). In addition, it was assumed that the non-linear element present in this model describes the effect of the occurrence of dry friction hSign(dx/dt) in the tested material, the value of which h is not constant but depends to some extent on the level of material deformation (variable x) is described by the relevant function. In this way, a non-linear third-order equation was obtained describing the motion of the so-called degenerate system. The developed method was tested on a computer system.
Design, build and test of packaging for vibration control of medical goods delivered by drone
Authors: Waters T P , Sherman L , Moxey H , Yang J , Court B , Chan H , Ng Y X , Cherrett T J , Oakey A , Theobald K
Published: June 2024

The delivery of medical products by drone is potentially game-changing and promises increased speed, particularly when trying to service hard to reach rural areas, and reduced carbon emissions. However, this raises a number of questions, including the effects of flight on the stability of medical products and how this can be mitigated through the design of appropriate packaging. The aim of this study was to design and experimentally evaluate a medical goods package capable of mitigating the vibration experienced during transportation by drone. Two proposed designs have been developed that feature coil spring and wire rope isolators. Transmission of vibration by these prototype packages, together with an industry-standard product, was measured both in the laboratory and in transportation trials. The prototype packages reduced transmitted vibration by a factor of six during drone flight tests but performed slightly worse when transported by car since road inputs occur at characteristically lower frequencies. The prototypes are significantly heavier than the standard product when empty although this is partially offset by a reduction in the number of required cool packs facilitated by the use of high performance vacuum insulation panels.
Analysis of a tendon-based deformation aggregation mechanism to host discrete vibration absorbers in continuum structures
Authors: Jayatilake S D , Woods B K S , Lowenberg M H , Titurus B
Published: June 2024

This paper investigates the possibility of developing a novel vibration absorber aimed towards slender continuous structures such as wings or blades. The absorber essentially consists an axially elastic tendon guided along a series of points along the span of cantilevered laboratory beam demonstrator, such that an aggregate of its induced extensional activity is observed at a specific location. The central idea is to introduce a discrete absorber at this strategically selected point, with the tendon providing the stiffness between the absorber and the primary structure. To explore the concept, the presented experiment is aimed at providing a comparison against a reduced 2 degree of freedom representation of the combined and mutually coupled absorber system. The specific focus of this arrangement is to support the interpretation of the underlying modal characteristics of the proposed concept.
A Topologically Designed Metamaterial Filter for Nonlinear-guided-wave-based Structural Health Monitoring Application
Authors: Liu Ze , Shan Shengbo , Cheng Li
Published: June 2024

Nonlinear guided waves (NGW) show great promise for structural health monitoring (SHM) due to their high sensitivity to the early detection of material micro-structural defects. In an SHM system, however, there exist inevitable non-damage-related nonlinear sources that may overwhelm the damage-induced nonlinear wave components, which in turn may jeopardize the practical implementation of the NGW-based SHM methodology. To eliminate these deceptive nonlinear interferences, this study introduces the concept of metamaterials to SHM. A wave filtering device, referred to as a meta-filter (MF), is developed to be surface-mounted on the structure under inspection under a second harmonic Lamb wave based SHM paradigm. Through a topological design, the MF enables ultra-wide stopbands to eliminate the secondary Lamb waves of the probing waves while preserving their strong fundamental wave components. The band structure, underlying wave filtering mechanism and the wave filtering function of the MF are investigated through finite element simulations. Upon tactically introducing deceptive nonlinear interferences at the actuation area, exemplified by adhesive bonding layers in a PZT-activated SHM system, the performance of the MF is examined from an SHM perspective, and finally validated experimentally using a metal specimen containing local plasticity-related incipient damage. Results demonstrate that the designed MF entails significant enhancement of the detection ability of NGW-based SHM system for incipient damages on one hand, and also allows for flexible selection of the excitation frequency on the other hand thanks to the customized band features enabled by the topological optimization.
Crack monitoring in concrete beams under bending using ultrasonic waves and coda wave interferometry: the effect of excitation frequency on coda
Authors: Knak M , Wojtczak E , Rucka M
Published: June 2024

Concrete is one of the most widely used construction materials in the world. In recent years, various non-destructive testing (NDT) and structural health monitoring (SHM) techniques have been investigated to improve the safety and control of the current condition of concrete structures. This study focuses on micro-crack monitoring in concrete beams. The experimental analysis was carried out on concrete elements subjected to three-point bending in a testing machine under monotonic quasi-static loading. During the tests, the fracture process was characterized using ultrasonic waves. The recorded signals were further processed by coda wave interferometry (CWI). This technique allowed the detection of cracks using the decorrelation between ultrasonic wave signals collected at different stages of degradation. Different values of excitation frequencies in the range from 100 kHz to 400 kHz were used to investigate the influence of frequency selection on the effectiveness of the damage indication based on the decorrelation of coda waves. The results obtained from the experiments were intended to highlight the effect of the applied frequencies on the coda wave interferometry.
Dynamic changes on a masonry cross vault after a forced damage
Authors: Bru D , Ivorra S , Torres B
Published: June 2024

This work shows the preliminary results related to the evaluation of the dynamic behavior of a 5x5 m masonry cross vault after undergoing different changes in its structural behavior. It has been built using solid clay bricks and lime and sand mortar. The cross vault has been built in the laboratory specifically for carrying out these tests and evaluating its structural behavior. A device has been designed to be able to carry out a controlled settling of one of its supports without causing an instantaneous collapse of the structure. Dynamic identification using OMA was performed by installing seismic accelerometers at several selected points on the structure, using ARTEMIS software to analyze the results. The evolution of the dynamic characteristics was carried out in four different states: (i) After construction (ii) After the generation of generalized damage through the forced settlement of one of its supports. (iii) After repair using Textile Reinforced Mortars (TRM) (iv) After generating new damage by settling one of its supports in the TRM repaired structure. After the generation of the damage in the structure, important cracks are observed in various points of the structure, although no situation was reached that would foresee a possible collapse. The repair with TRM has consisted of the introduction of fiberglass mesh bands coated in lime and sand mortar. These bands have been arranged forming a cross in the upper part of the structure and in all the edge arches of the structure. In all these phases the OMA was developed under a situation of ambient vibrations, where these vibrations levels were very low due to the situation inside of a laboratory. After each of these phases, their main frequencies, their vibration modes and the structural damping factor of each of the identified modes have been obtained. It is observed how a loss of rigidity of the vault occurs after the production of damage and how it completely recovers by means of reinforcement and repair with TRM. An increase in the damping ratio of practically all the vibration modes has been detected when the structure is damaged, although after repair with TRM these values are reduced again.
Cahora Bassa vibrations monitoring between 2010-2022. Analysis of frequencies using HST statistical models for effects separation
Authors: Oliveira S , Mendes P , Rodrigues M , Alegre A , Proença J , Carvalho E , Matsinhe B
Published: June 2024

Cahora Bassa dam is a 170m-high arch dam located in western Mozambique. In operation for almost 50 years, since 1974, the dam is affected by a swelling process of small/medium amplitude. Aiming to control its structural health over time, in 2010 the dam was instrumented with a continuous vibrations monitoring system, designed for Seismic and Structural Health Monitoring (SSHM), which includes 10 uniaxial accelerometers in the crest gallery and 3 triaxial accelerometers in the dam-foundation interface. The latest results on the dynamic behaviour monitoring of the dam are presented, namely the evolution of the main natural frequencies over time and the corresponding mode shapes. Then, HST statistical models for separation of effects, considering the hydrostatic pressure (H), seasonal variations (S), and time (T) dependent factors, are used to analyse the evolution of the experimental natural frequencies over the last 12 years. The achieved results show that the dynamic behaviour of the dam is mostly influenced by the water level variations. However, a very small decreasing tendency of the natural frequency values was detected, which may indicate a slight decrease of the global stiffness of the dam, possibly due to the evolution of the concrete swelling pathological process.
Data-Driven Railway Vehicle Parameter Tuning using Markov-Chain Monte Carlo Bayesian updating
Authors: Hoelzl Cyprien , Keller Lisa , Simpson Thomas , Stoura Charikleia , Kossmann Claudia , Chatzi Eleni
Published: June 2024

Understanding the dynamics of the interaction between railway vehicles and tracks is essential for forecasting vehicle and track conditions and performing maintenance actions to preserve the safety of railway infrastructure. In this work, physics-based models are deployed to predict the dynamic response of railway vehicles to track alignment and irregularities. Such models comprise a large number of parameters that need to be validated and possibly tuned, a task often accomplished on the basis of expert knowledge or trial-and-error without necessarily reflecting the condition of the operating system as-is. Therefore, model uncertainties persist due to assumptions on the actual system behavior, as well as due to varying operational parameters (e.g., wheel profile, rail profile, rail moisture). To improve modelling accuracy, this study adopts a multi-body vehicle model, realized in SIMPACK software, and performs parameter tuning based on on-board measurement data (accelerations and forces) from an instrumented tilting train, which regularly traverses the Swiss Federal Railways (SBB) network. The pertinent vehicle model is optimized in terms of the interaction forces at the wheel-rail contact using a Bayesian model updating approach, relying on Markov-Chain Monte Carlo (MCMC). Specifically, the MCMC method is applied to estimate both optimal vehicle parameters and their uncertainty by minimizing the mean squared error between simulated and measured contact forces, leading to an improved vehicle twin.
A combined implicit-explicit vibration-based SHM method for damage detection of wind turbine blades
Authors: Drangsfeldt Casper Aaskov , Avendaño-Valencia Luis David
Published: June 2024

Today, the green transition is being pursued more than ever, leading to a significant increase in the installation of wind turbines and wind farms. Maintaining and servicing the wind turbines is accompanied by extensive expenses. Therefore, predictive maintenance techniques are in increasing demand, including the implementation of a well-functioning Structural Health Monitoring (SHM) system. In this work, physical and non-physical vibration features along with various techniques to mitigate the effect of Environmental and Operational Variability (EOV) are investigated. Vibration features originating from Vector Auto-Regressive (VAR) models are considered. Physics-domain DSFs comprise the natural frequency, while the non-physical DSFs comprise the VAR model coefficients. A challenging and inevitable aspect in SHM is the effect of EOV that can alter the DSFs so as damage does. Two mitigation approaches are considered, the first based on Bayesian non-linear regression –explicit– and the second based on Principal Component Analysis (PCA) –implicit–. Additionally, a novel combined approach is proposed, featuring regression of Principal Components (PCs). As some of the PCs will be EOV-insensitive, the specific corrected PCs are automatically selected using the F-statistic of individual regressions. A comparative analysis is carried out in a controlled experiment, featuring the vibration response of a lab-scale wind turbine blade under various temperature and damage conditions. The methods are assessed in terms of correctly detected damages from a one-class classifier based on the squared Mahalanobis distance on the EOV-corrected features, and best performing method combinations are thereby identified.
Resolving the effects of peak-splitting alike artefacts in FBG measurements for fatigue assessments of an offshore wind turbine foundation
Authors: Fallais D , Weijtjens W , Devriendt C
Published: June 2024

Fiber Bragg grating (FBG) based optical strain sensors have become more commonplace for fatigue monitoring applications of large structures. Despite many advantages above conventional strain gauges, in some cases FBG measurements can become corrupted by complicated failure modes, which might relate to fiber integrity or interpretation of optical signals. In this article, over one month of corrupted FBG strain data obtained from a monopile of an operational wind turbine will be assessed, with the objective to resolve the issues around the severe jump-like distortions which are present in the data. To this end, an initial working hypothesis is formulated which states that removing the jump-like distortions will improve the quality of the data and increase usability. Throughout the article this hypothesis will be tested and adjusted, as the amount of information used in the assessment will be step-wise increased. The results show that the initial goal of removing jump-like artefacts is achievable, resulting in a visually much-improved signal; however, the results obtained using the fatigue-related metrics show inconsistencies when compared with predicted fatigue quantities; these predictions are obtained using two virtual sensing methods, which extrapolate strain reference data, in terms of damage equivalent moments and time series, to the locations of the corrupted FBG sensors. Results indicate that the observed failure mode is more complex than initially expected. Finally the hypothesized failure mode is revisited, and recommendations about the usability of the data are discussed.
Estimating Modal Properties of Nonlinear Cables Using Targetless Visual Tracking
Authors: Riveros N , Boroschek R L , Beltran J F
Published: June 2024

One way to study the health state and operational force on a cable under varying environmental conditions is to estimate its modal properties. In this study, the vibration of a nonlinear polymer cable is examined in the laboratory using computer vision techniques, such as videos, in comparison with traditional sensors. Two types of excitations are used to induce cable vibration: broad band ambient vibrations and initial conditions (deformation and impact). Displacements are measured simultaneously with traditional sensors and consumer-grade cameras (including smartphones) from different perspectives (full-field and local measurements). The traditional sensors include six ultrasonic sensors equidistantly located along the cable and an accelerometer near one end. For each video obtained, multiple feature points of the cable are tracked using the KLT algorithm without artificial targets, and the displacement records are obtained in pixels. Modal properties are determined using parametric techniques like SSI-COV and ERA. To determine displacement in metric units and mode shapes with perspective correction, a methodology is proposed using camera calibration. The non-linearity of the cable is studied by analyzing the temporal evolution of frequencies over time. The performance of the proposed methodology was then compared to that of conventional sensors.
An effective approach based on reliability methods for high-dimensional Bayesian model updating of dynamical nonlinear structures
Authors: Jerez D. J. , Jensen H. J. , Beer M. , Figueroa C.
Published: June 2024

Bayesian model updating represents a sound formulation to incorporate the unavoidable uncertainties arising in the system identification of infrastructure assets. However, the treatment of cases involving a relatively large number of model parameters remains an open issue, especially for dynamic nonlinear structural models. In this context, an effective implementation of subset simulation is considered within the framework of Bayesian model updating with structural reliability methods (BUS). For improved numerical efficiency, a substructure coupling technique for dynamic analysis is implemented to develop a reduced-order model strategy. To assess the capabilities of the proposed method, an application example that considers a three-dimensional bridge model equipped with nonlinear devices is presented.
Novelty detection across a small population of real structures: A negative selection approach
Authors: Delo Giulia , Mattone Massimiliano , Surace Cecilia , Worden Keith
Published: June 2024

Vibration-based Structural Health Monitoring (SHM), exploits a variety of approaches for novelty detection. In particular, many data-based methods try to recognise patterns by exploiting analogies with the human body’s natural defences at a cellular level. These algorithms fall within the Artificial Immune System (AIS) class and can be chosen, according to their peculiarities, to solve specific problems in diverse application areas. This study investigates the damage-detection process in different operational conditions, obtained by applying structural modifications to a laboratory-scale aeroplane, which follows the geometric features of the GARTEUR benchmark project. Damage identification is performed by exploiting the Negative Selection Algorithm (NSA), already applied by some of the authors on numerically-simulated case studies, and chosen for its capability of self/non-self discrimination under varying operational or environmental conditions. The research is expanded by using sparse autoencoders for feature dimensionality reduction. The method is applied to an experimental dataset acquired via Scanning Laser Doppler Vibrometer (SLDV) measurements, to identify consistent damage-sensitive features from the frequency response functions, and to obtain a reliable fault-detection performance.
R/C buildings’ seismic damage prediction based on semi-supervised automatic differentiation variational inference deep autoencoder
Authors: Demertzis K , Kostinakis K , Morfidis K , Iliadis L
Published: June 2024

Structural damage from earthquakes has been assessed using a variety of methodologies, both statistical and, more recently, utilizing Machine Learning (ML) algorithms. The effectiveness of data-driven procedures, even when applied to extremely time-consuming scenarios and data sets that reflect substantial expertise and research, completely depends on the quality of the underlying data. The performance of the intelligent model can also be impacted by a lack of in-depth knowledge and expertise in using complex machine learning architectures. This can also prevent some crucial hyperparameters from being adjusted, which ultimately reduces the algorithm’s reliability and generalizability. The present research offers a Bayesian-based semi-supervised Automatic Differentiation Variational Inference (ADVI) deep autoencoder for forecasting seismic damage of R/C buildings. It is a state-of-the-art, intelligent technology that automatically converts the variables in the issue into actual coordinate space using an upgraded ADVI technique. Finally, using a brand-new Adaptive Learning Rate Gradient Algorithm (ALRGA), it chooses a technique in this area that is a function of the changed variables and optimizes its parameters. Using the sophisticated ADVI technique to establish a posterior distribution without having an analytical solution is an upgraded version of the semi-supervised learning method. Estimating seismic damage to buildings is accelerated and greatly simplified by the suggested methodology, which eliminates the computational complexity of the analytical methods. By performing Nonlinear Time History Analyses of 3D R/C structures exposed to 65 earthquakes, a realistic dataset for the model evaluation is produced. The system’s strong generalizability and the proposed methodology’s detailed convergence stability reveal that it is a valuable method that can outperform other ML algorithms.
Bayesian updating of the displacement-strain transformation matrix
Authors: Adarsh S , Panda Jagajyoti , Ray-Chaudhuri S
Published: June 2024

The updating of the displacement-strain transformation matrix has not garnered much attention over the years, as most studies focus on updating mass, damping, and stiffness matrices. In this study, updating of the parametrized displacement-strain transformation matrix is done in a Bayesian probabilistic framework by combining the data from both acceleration and strain sensors. The Bayesian framework ensures that the uncertainties, especially modeling uncertainties, are explicitly considered and provides multiple possible estimates of the parameters, unlike a classical estimation framework where only one value is estimated. Samples from the posterior probability density function of the parameters are simulated using the transitional Markov Chain Monte Carlo method. The updated displacement-strain transformation matrix can be used to obtain strains with higher fidelity in numerical simulations and to obtain robust response predictions incorporating modeling uncertainties. In addition, once a transformation matrix has been updated, only acceleration data are required for damage localization, i.e., strain measurements are not required post-updating, thereby reducing the overall health monitoring costs and data storage burden. The Bayesian updating procedure is investigated using experimental data from a four-story shear building laboratory model.
Translating Assembly Accuracy Requirements to Cut-Off Frequencies for Component Mode Synthesis
Authors: Janssen Lars A.L. , Besselink Bart , Fey Rob H.B. , Wouw Nathan van de
Published: June 2024

One of the most popular methods for reducing the complexity of assemblies of finite element models in the field of structural dynamics is component mode synthesis. A main challenge of component mode synthesis is balancing model complexity and model accuracy, because it is difficult to predict how component reduction influences assembly model accuracy. This work introduces an approach that allows for the translation of assembly model accuracy requirements in the frequency domain to the automatic selection of the cut-off frequencies for the model-order reduction (MOR) of components. The approach is based on a mathematical approach for MOR for coupled linear systems in the field of systems and control. We show how this approach is also applicable to structural dynamics models. We demonstrate the use of this approach in the scope of component mode synthesis (CMS) methods with the aim to reduce the complexity of component models while guaranteeing accuracy requirements of the assembly model. The proposed approach is illustrated on a mechanical, three-component structural dynamics system for which reduced-order models are computed that are reduced further compared to reduction using standard methods. This results in lower simulation cost, while maintaining the required accuracy.
A Hazard-consistent Residual Drift Model for SMRF
Authors: Zahra Faridah , Macedo Jorge , Málaga-Chuquitaype Christian
Published: June 2024

The seismic permanent or residual drift is a structural response parameter of relatively easy collection and one whose usefulness in damage assessment has been proven in many past earthquake events. Oftentimes, residual drifts are a key factor when deciding on the demolition of a number of structures, even if said structures do not show other evident signs of severe damage. However, general studies on seismic residual drift demands are far less common than those dealing with its transient maximum drift counterpart. In this paper, we offer a simple data-driven predictive model for residual drift demands in Steel Moment Resisting Frames (SMRF). To this end, our model is based on a database generated by nonlinear response history analyses (NRHA) on 24 deteriorating SMRFs under the action of 596 hazard-consistent ground-motion records resulting in a database of more than 14 000 structural responses. The model development is preceded by an extensive feature selection process that employs several Machine Learning (ML) algorithms. Importantly, all available seismic codes and studies regarding residual drift demands available to date have overlooked the issue of hazard consistency, therefore disregarding the causal connection between seismic hazard level and the corresponding ground motion suite used. In contrast, we use the Conditional Scenario Spectra method, which generates a set of realistic earthquake spectra with an assigned rate of occurrences based on their spectral shape and intensity, hence, our results preserve the critical relationship of hazard consistency. In this context, our model highlights the severe over- and under-estimations associated with hazard-inconsistent estimates of residual drifts.
Computational homogenization method for the bending analysis of submarine power cables
Authors: Fang Pan , Li Xiao , Jiang Xiaoli , Hopman Hans , Bai Yong
Published: June 2024

The complex structure and material property of a cable, particularly the stick-slip issue among its components pose the challenge for the bending analysis of submarine power cables. The calculation time and convergence problem of a full model makes the simulation unpractical during the design phase. This paper takes advantage of the peculiar structural property of helical components inside a cable, proposing a computational homogenization approach for analyzing the cable behavior under bending from global and local perspectives. This method assumes a macro model that is based on the theory of periodic beamlike structure, and a short-size micro model that is solved through a detailed finite element study. Results demonstrate the efficiency and capability of the proposed model that considers the structure nonlinearity and contact condition of a multi-layer cable with helical wires.
Railway vibration emission model based on a multi-contact source-receiver mobility approach
Authors: Villot Michel , Guigou-Carter Catherine
Published: June 2024

Railway ground-borne vibration emission is an ongoing issue, which shows a need for vibration emission characterization and prediction where the approach used should ensure transferability from one site to another. This transfer is often calculated using heavy frequency-based (narrow band) numerical models. This paper suggests a quicker approach, where the rolling stock/track/ground system is considered as a source-receiver mechanical system and the three parts of the system represented by their mechanical mobilities. In such a mobility approach, the passing train acts as primary vibration source (represented by a line of uncorrelated forces applied to the track), and the track acts as a vibration transfer system between passing train and ground. The couplings between passing train and track and between track and ground are both represented by a multi-contact line with the same spatial resolution. The output quantity is the line of uncorrelated contact forces (contact force density) applied to ground and the quantity used to evaluate the railway vibration emission is the vibration power transmitted to ground. An application of this mobility approach to IC trains rolling on ballasted track laid on typified homogeneous soils (soft, medium and stiff) is presented.
A numerical validation of a 3D hybrid meshless methodology for dynamic soil-structure interaction problems
Authors: Arcos Robert , Soares Paulo J , Conto Kenny F , Costa Pedro Alves , Godinho Luís
Published: June 2024

In this paper, a hybrid meshless methodology for the simulation of dynamic soil-structure interaction problems is verified in a three-dimensional context. The method aims to predict the ground-borne noise and vibration levels to which a new building to be constructed close to a ground vibration source will be subjected. The method is based on three steps: incident wave field evaluation in a set of collocation points, incident wave field virtualization by a set of virtual forces and structure response determination applying the set of virtual forces to a coupled soil-structure model. The proposed meshless method is verified in the context of the problem of one and four shallows foundations embedded in a homogeneous half-space subjected to harmonic loading using synthetic data for the incident wave field in the ground surface. Discussions on the practical deployment of the method are also included.
Quantification of Polymorphic Uncertainties in Structural Dynamics: Case Study of a Guyed Mast
Authors: Marwitz Simon , Lahmer Tom , Zabel Volkmar
Published: June 2024

Aging vibration-prone structures may require up-to-date proofs of their load-bearing capacity for retrofitting or life-cycle assessments. The structural vibration response is affected by naturally variable structural properties and loads, known as aleatory uncertainties. With modeling, additional epistemic uncertainties are introduced due to missing knowledge of model parameters. The model responses then include both types of uncertainties in a mixed and nested form. Quantifying these polymorphic uncertainties is particularly important in structural dynamics, where a deterministic model may significantly underestimate responses, such as resonance phenomena.

A case study is conducted to characterize the vibration behavior of a guyed mast under polymorphic uncertainties. A simplified linear structural model is built using commercially available FEM software. Polymorphic uncertainties in the input parameters are modeled and propagated using in-house code.

Aleatory uncertainties are modeled by probability theory, and a quasi-Monte Carlo simulation based on weighted sampling facilitates an efficient reuse of computed samples. Epistemic uncertainties are modeled by evidence/belief function theory and their propagation is performed using interval optimizations on Radial Basis Function interpolators and quasi-Monte Carlo sequences. Particular emphasis is placed on computational efficiency, as the developed method is designed to be used for more complex numerical models. Statistics and aggregation of belief functions are used to yield explainable results.

The case study scenario is a retrofit of a guyed mast based on outdated design documents. Epistemic uncertain parameters include unknown structural damping, cross-section tolerances, material properties, the additional mass from antennas and cables, and the pre-tensioning forces of the guy cables. Aleatory uncertainties arise from temperature effects on the guy cables and the viscosity of the dampers, as well as from icing in winter. The results highlight the intrinsic variations of natural frequencies, the characterization of resonance bands due to epistemic uncertainties, and the effectiveness of a deterministically designed Tuned Mass Damper (TMD) in a structural model influenced by polymorphic uncertainties.

The developed methodology is applicable to moderately computationally expensive models of any type. Model runs are efficiently re-used and the uncertainty propagation can be highly parallelized. The method reveals where enhancing knowledge about partly-known model parameters is beneficial and permits robust retrofit designs or increased confidence in life-cycle estimates.
Model updating for the simulation of surface strains on printed circuit boards considering parameter uncertainty
Authors: Schmidt H , Käß M , Lichtinger R , Hülsebrock M
Published: June 2024

The efficient and reliable design of power electronic components plays an important role in the development process of electrically driven vehicles. One key aspect is the reliability of solder joints on printed circuit boards (PCB) that greatly depends on the surface strain at the solder joint locations. It is therefore unavoidable to use precise simulations of surface strains to reliably estimate the solder joint lifetime. This work presents a procedure of model updating of a printed circuit board model that considers the variability of board behavior due to uncertainties in the material composition or the manufacturing process. Hierarchical Bayesian model updating is applied to incorporate this variability. The printed circuit board is seen as a multi-level model that is updated in two steps. Experimental data from system and component level are used to sequentially update the printed circuit board and the board mounting. The experimental data combine modal information and measured frequency response functions. The proposed procedure is applied to a test PCB and the updated model is validated with experimental surface strain data.
An innovative only-output method to identify a structural system
Authors: Russotto S , Denoël V , Pirrotta A
Published: June 2024

Structural Health Monitoring (SHM) is nowadays common in many branches of engineering since it allows to have a continuous or periodic report of the structural conditions and therefore to promptly intervene if there are incipient damages. The first step to perform a SHM is the identification of the dynamic parameters, i.e. natural frequencies, damping ratios and modal shapes, and it is a crucial step since a modification of the structural parameters can be a direct consequence of structural damages. Among the structural identification methods, Operational Modal Analysis (OMA) methods have received increasing attention from the researchers since they do not require the knowledge of the structural excitation that is due to ambient vibrations and that is usually modeled as a white noise. This aspect makes this kind of methods cheaper and simpler than the classical Experimental Modal Analysis (EMA) methods.

In this paper an innovative OMA method is proposed. It is a semi - automated method that allows to identify natural frequencies, damping ratios and modal shapes of a structural system and that can be used also from users that have not knowledge in stochastic dynamics and signal analysis. First of all, the modal shapes are estimated through the use of signal filtering techniques applied on the stochastic properties of the output process and then natural frequencies and damping ratios can be estimated from the mono - component analytical signals obtained by performing a decomposition of the analytical signals matrix. The proposed method has been used to perform the dynamic identification of a real historic building situated in Palermo, i.e. Chiaramonte palace, and the results obtained have been compared with those obtained by using other OMA methods.
On reduction of noise emissions from thin-walled slender tubes by means of acoustic metamaterials
Authors: Søndergaard S H , Søe-Knudsen A
Published: June 2024

The dynamic response of a thin-walled slender tube is dominated by noisy flexural modes. One topic of interest in research today is the use of acoustic metamaterials to reduce noise emissions from structures. These aspects are combined in the present work in which a solution for reducing the noise emission from thin-walled tubes is sought. The Wave Finite Element Method (WFEM) is used to estimate the dispersion relation of the free propagating waves in the tube. Extrudable rings of thermoplastic material are added to the inside of the steel tube as local resonators for changing the response. The rings are added in sections to create a periodic waveguide which introduces interference stop-bands for the flexural waves. Additionally, local bending modes of the rings couple with the global modes of the tube to reduce global vibrations at the resonant frequencies of the rings. The results of free wave propagation analyses obtained through WFEM are compared to the forced response of the structure in standard linear harmonic analyses conducted in the commercial FE software Ansys. This is done in different loading scenarios to determine the impact of adding the resonator rings to different excitations and frequencies.