bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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.
Comparative assessment of stabilizing techniques for joint input-state estimation via Augmented Kalman Filter
Authors: Caglio Luigi , Stang Henrik , Katsanos Evangelos 
Published: June 2024

Abstract
In the context of Structural Health Monitoring, the accurate estimation of the state of a structural system subjected to various sources of dynamic loads can be beneficial for assessing the current structural performance and for predicting the future one. In case of linear systems, for example, the estimation of the state can provide valuable information about unmeasured strains and corresponding stresses that, in turn, can favor the prediction of fatigue damage. Additionally, state estimation of structural systems responding in the nonlinear regime can facilitate the identification of damages that occurred during an extreme event (e.g., excessive wave, earthquake and strong wind). A major challenge in the state estimation task stems from the unavailability of the external input loads. Therefore, several joint input-state estimation techniques have already been developed to address this issue; among them, the Augmented Kalman Filter (AKF) is one of the most commonly employed. Despite the advantages of the AKF, a critical aspect of this joint input-state estimation technique is associated with the instability that the estimation can experience when only noisy acceleration time series are available. Heretofore, several approaches have been proposed aiming to stabilize the estimation in case of linear systems. In this work, some of the most commonly employed approaches for stabilizing the AKF-based joint-input state estimation (e.g., dummy displacement measurements, dummy load measurements, and Gaussian process latent force model) are adopted and thoroughly compared. Two five-DOF linear systems subjected to dynamic loads are simulated, while the calculated responses are used to assess and compare the performance of various existing techniques for stabilizing the estimation.
Convolution models for output only linear structural system identification and the problem of identifiability.
Authors: Mclean J.H. , Dervilis N , Rogers T.J. 
Published: June 2024

Abstract
This paper investigates the use of the Gaussian Process Convolution Model (GPCM) as an output only system identification tool for structural systems. The form of the model assumes a priori that the observed data arise as the result of a convolution between an unknown linear filter and an unobserved white noise process, where each of these are modelled as a GP. The GPCM infers both the linear time filter (which is the impulse response function, i.e. Green’s function, of the system) and driving white noise process in a Bayesian probabilistic fashion with an approximate variational posterior over both signals. It will be shown that although the model structure is intuitive and sensible priors are applied, the GPCM falls short in recovering the linear impulse response of interest response due to the problem of identifiability. This is an interesting result indicating that physically informed kernel structures alone are not enough to recover the true impulse response in similar non-parametric probabilistic models. Despite this, the avenue of research remains highly promising, and several ideas are proposed to improve the model as a system identification tool.
Unsupported machining fixture layout optimisation
Authors: Soto C , Sims N D , Ozturk E , Weekes B 
Published: June 2024

Abstract
It is well established that excessive vibrations in machining operations hinder productivity and quality of the components being made. In these environments it is common to encounter self-excited vibrations due to the dynamic response characteristics of the cutting tool and workpiece; referred to as regenerative chatter. To suppress these effects, conventional practices provide the workpiece with as much support as possible and therefore commonly require custom-built fixturing bases and several manual intervention stages. In contrast, for modern reduced fixturing approaches, the workpiece is minimally-held, with the benefits of reduced setup times, lower fixturing and inventory costs, and improved access to the workpiece thereby avoiding multi-stage setups. However, minimal fixturing reduces support of the workpiece, and so vibration becomes a greater challenge, along with the subsequent detrimental effects to part quality and material removal rate (mrr). This paper sets out to determine an optimisation methodology for layout configurations that maximise milling depths of cut whilst achieving dynamic stability; by means of FEA model-based simulations and particle swarm optimisation (pso) methods. The optimisation algorithm is then tested on simplified setups and compared to exhaustive searches. It is shown that optimal results can differ from standard practice, and despite the comparative reduction in workpiece stiffness to a traditional approach is mostly unavoidable, careful placement of workholding elements can reportedly improve cutting conditions and increase dynamic stability within an unsupported environment.
Sensor placement optimal for the precision of modal parameter estimation with subspace methods
Authors: Greś Szymon , Döhler Michael , Dertimanis Vasilis , Chatzi Eleni 
Published: June 2024

Abstract
In this paper we focus on sensor placement for output-only modal analysis, where the objective is to choose those sensor locations yielding a minimal variance in the identification of modal parameters from measurement data. It is heuristically shown that the variance of modal parameters estimated with data-driven subspace identification can be approximated solely based on the process and the measurement noise properties with the Kalman filter and the underlying system model, and is independent of data which are not available at the experimental design stage. The performance of the proposed approach is illustrated on an extensive Monte Carlo simulation for an illustrative example of a mechanical chain system.
Vibration-based assessment of the structural integrity of a masonry wall system with single opening subjected to progressive damage induced by out-of-plane loading conditions
Authors: Meoni A , D’Alessandro A , García-Macías E , Saviano F , Parisi F , Lignola G P , Ubertini F 
Published: June 2024

Abstract
Existing masonry constructions often develop a complex mechanical response due to considerable material heterogeneity of the ancient masonry and presence of structural pathologies. The occurrence of severe loading conditions, such as those caused by differential soil settlements and seismic events, can also induce brittle collapse mechanisms in ancient masonry constructions. Operational Modal Analysis (OMA) methods are particularly well-suited Structural Health Monitoring (SHM) approaches for historical masonry constructions. Despite their benefits, low sensitivity of OMA methods to localized damage is often indicated in the literature as major limitation. This paper presents preliminary results of vibration-based structural integrity assessment of a masonry wall system with single opening. Specifically, the wall specimen was subjected to progressive damage induced by increasing out-of-plane displacements. The modal identification of the structure was performed at different steps of the test sequence. Similarly, visual inspections were carried out on the wall specimen to detect the development of damage. Changes in the identified modal features were computed for every step of the test. The obtained preliminary results show clear variations in modal features, consistently with the damage level suffered by the tested structure. Interestingly, mode shapes were found particularly sensitive to damage even under initial levels of out-of-plane deformation.
Damage detection of a typical historic masonry tower using control charts
Authors: Testa F , Barontini A , Lourenço P B 
Published: June 2024

Abstract
Control charts have become a common method for damage detection within vibration-based structural health monitoring. Successful applications have been implemented including for historical buildings preservation. Nonetheless, their performance is affected by several algorithm parameters that should be properly set and more research is needed to optimise such tools. To this end, the present work discusses the preliminary results of a project that focuses on the development of a cost-effective damage detection strategy based on control charts for masonry towers in seismic prone areas. Here, a prototype of historic tower is defined based on an extensive documentary search, a methodology to simulate realistic long-term monitoring data is developed and, finally, different parameters that may affect the damage detection performance are analysed and compared against small-extent damage scenarios. The importance of normalising the features to account for seasonal fluctuations and setting a correct threshold for detection clearly emerged and drives the future scope of the work.
Dynamic characterization of a modern heritage structure: the Palazzetto dello Sport by Pier Luigi Nervi
Authors: Ciambella Jacopo , Ranzi Gianluca , Romeo Francesco 
Published: June 2024

Abstract
This paper focuses on the dynamic characterization and monitoring of the Palazzetto dello Sport in Rome, a reinforced concrete structure built in 1957 by Pier Luigi Nervi. The study employs an experimental dynamic testing campaign to identify the structure’s modal properties via Operational Modal Analysis (OMA) and to develop an accurate 3D numerical model of the structure. The analysis of the dynamic features associated with the axial symmetry of the dome reveals the presence of axisymmetric and non-axisymmetric modes with identical frequencies. The repeated modes analysis is performed using the MAC criterion validation. The selection of suitable dynamic structural characterization strategies for monitoring the exemplary twentieth-century concrete structure considered is eventually discussed. The extracted information can be used for effective structural condition assessment.
An investigation into wave propagation in hanging chains
Authors: Cleante V G , Gonçalves P J P , Waters T , Brennan M J , Carneiro J P , Rade D A 
Published: June 2024

Abstract
The study introduced in this work is motivated by the prospect of using a hanging chain as an Acoustic Black Hole (ABH) for passive vibration control. An ABH is effectively a waveguide in which a wave slows progressively as it propagates away from the source enabling it to be extinguished with modest damping. The effect can be achieved by engineering inhomogeneity into a structure’s geometry or material, the most common realisation being a beam of tapered thickness. This paper proposes an alternative realisation, that of a chain hanging under its own weight. Such a system has a wave speed that naturally decreases to zero, owing to its linear variation in tension, thus overcoming the challenges of constructing precisely shaped beams with vanishingly thin tips. The study of transverse vibration of hanging chains is a classical problem in structural dynamics. The motion of the chain can be described in terms of Bessel or Hankel functions, which are needed to account for the variation in tension along the chain. In this work, the hanging chain problem is revisited from a wave propagation perspective. An expression is derived for the amplitude of the waves in an infinite chain due a point excitation. From which, the spatial behaviour and the receptances of the waves are evaluated, revealing differing characteristics of upward and downward propagating waves. Some experimental results are presented to support the theoretical analysis.
A three-dimensional model of an air bubble curtain in offshore pile driving
Authors: Peng Yaxi , Tsouvalas Apostolos 
Published: June 2024

Abstract
With the growing demand for renewable energy, an increased number of offshore wind farms are planned to be constructed in the coming decades. The monopile is the main foundation of offshore wind turbines in shallow waters while the installation process itself takes place with large hydraulic impact hammers. This process is accompanied by significant underwater noise pollution which can hinder the life of mammals and fish. To protect the marine ecosystem, strict sound thresholds are imposed by regulators in many countries. Among the various noise mitigation systems available, the air-bubble curtain is the most widely applied one. While several models exist which aim to describe the mitigation performance of air-bubble curtains, they all assume a cylindrically symmetric wave field. However, it is well known that the performance of the air-bubble curtains can vary significantly in azimuth due to the inherent variations in the airflow circulation through the perforated pipes positioned on the seabed surface. This paper presents a new model which is based on a multi-physics approach and considers the three-dimensional behavior of the air-bubble curtain system. The complete model consists of three modules: (i) a hydrodynamic model for capturing the characteristics of bubble clouds in varying development phases through depth; (ii) an acoustic model for predicting the sound insertion loss of the air-bubble curtain; and (iii) a vibroacoustic model for the prediction of underwater noise from pile driving which is coupled to the acoustic model in (iii) through a three-dimensional boundary integral formulation. The boundary integral model is validated against a finite element model. The model allows for a comparison of various mitigation scenarios including the perfectly deployed air bubble curtain system, i.e.no azimuth-dependent field, and an imperfect system due to possible leakage in the bubbly sound barrier along the circumference of the hose.
Acoustic streaming in porous media – homogenization based two-scale modelling
Authors: Rohan Eduard , Moravcová Fanny 
Published: June 2024

Abstract
A homogenized model of the acoustic streaming (AS) in rigid porous periodic structure is presented. Using the classical perturbation approach, the first and the second order subproblems arising from the N-S equations governing the fluid dynamics in the pores are obtained and further homogenized. The driving force of the permanent flow is obtained due to the time average of the nonlinear advection terms expressed using the first order acoustic harmonic fluctuations. Homogenization of the 1st order problem yields the dynamic Darcy flow mode governing the wave response. This is employed to constitute the streaming source term involved in the 2nd order homogenized problem for time-averaged pressure field. The AS can be observed at both the macroscopic and the microscopic levels. While the acoustics-driven microflows are observed for any microstructure, the macroscopic AS depends on the porous microstructure geometry and boundary conditions. We propose a solution method based on the spectral analysis of the characteristic microscopic dynamic Stokes flow. The AS phenomenon in the homogenized medium is illustrated using 2D examples of periodic porous microstructures.
A comparison of high frequency force balance mode shape correction approaches for predicting wind effects on a high-rise building
Authors: Mahdi Salehinejad M. , Fai Li Yin , Ma Quincy , Flay Richard George James 
Published: June 2024

Abstract
The wind loads on high-rise buildings can be predicted from the high frequency force balance (HFFB) technique. This experimental technique is widely accepted among wind and structural engineers due to its simplicity and adaptability to obtain wind-induced loads and dynamic response of tall buildings. But, for the general case of non-linear and combined sway and twist mode shapes, analysis of HFFB measurements gives rise to serious challenges and various techniques have been developed using significant assumptions. In this study, a 1:300 scale model of Building A, a benchmark tall building geometry has been chosen to perform HFFB tests in a closed-circuit boundary layer wind tunnel. It has complex 3D mode shapes combining sway and twist motions. First, the base shears, overturning moments and torques for different wind directions were measured. Subsequently, different HFFB mode shape correction approaches were examined for estimating the dynamic wind effects using modal analysis in the time domain. Furthermore, the high frequency pressure integration (HFPI) wind tunnel technique was utilised to measure surface pressure information in separate tests to obtain the more precise wind effects results for validation of the HFFB predictions. The power spectral densities (PSDs) of aerodynamic base overturning moments and torques determined from both techniques are compared. The PSDs and variance coefficients of generalised wind forces for the first three modes are calculated and compared to each other to investigate the accuracy of the different HFFB-based analysis approaches. Also, the statistical properties including standard deviations and peaks of tip acceleration and tip displacement time histories are computed for comparison. The results show that the HFFB approaches overestimate the dynamic wind-induced responses and have some weakness for twist prediction. It is found that the HFFB methods with same wind loading correlation state generally seem to perform in a similar manner.
A probabilistic approach to the Poffenberger-Swart bending stress of conductors subject to aeolian vibrations
Authors: Foti F. , Denoël V. , Martinelli L. , Perotti F. 
Published: June 2024

Abstract
Overhead electrical transmission line conductors are prone to aeolian vibrations, resulting from the alternate shedding of vortices in the wake of the cable. Aeolian vibrations are characterized by small-amplitude high-frequency flexural oscillations and, whenever not properly controlled, can induce wear damage and fatigue failures of the conductor. The standard technical approach to the assessment of aeolian vibrations and residual life of overhead conductors is based on the Energy Balance Method (EBM) and the Poffenberger-Swart formula for bending stresses. This approach relies on the main simplifying assumption of mono-modal oscillations. Typical aeolian vibration records, however, clearly show that several modes can be simultaneously excited due to wind variations in time and along the span. In this work a new approach is proposed for the prediction of aeolian vibrations of conductors within a probabilistic framework. The proposed approach allows to account both for non-linearities typical of internal damping of metallic cables and multi-modal contributions to aeolian vibrations in a straightforward and mechanically sound way. The proposed approach paves the way to a full probabilistic description of the Poffenberger-Swart bending stresses, making a further step towards a more refined methodology to define of the expected life of overhead conductors.