bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the static and dynamic response of a post-tensioned concrete box girder bridge with vertically prestressed joints showing vertical deflections due to concrete creep deformation
Authors: Meoni A , Galassi Sconocchia G , Mariani F , Ierimonti L , Castellani M , Tomassini E , Venanzi I , Ubertini F
Published: June 2024

Time-dependent phenomena, such as creep of concrete, induce stress/strain redistributions in post-tensioned concrete bridges that must be taken into account during their design. The underestimation of time-dependent effects can negatively influence the load-deformation behavior of this bridge typology, leading to unexpected deformations of the deck, serviceability issues, and collapses. Numerical models able to simulate time-dependent phenomena should also be used to properly conduct the structural assessment of existing post-tensioned concrete bridges. However, before the introduction of specific materials’ constitutive laws to account for time-dependent phenomena, numerical models should be calibrated and validated according to the information gathered by testing the structures they represent, to carry out reliable numerical simulations. The paper presents the preliminary results obtained from the structural assessment of a post-tensioned concrete box girder bridge with vertically prestressed internal structural joints, which exhibits marked deflections of the box girder. A numerical model of the case study bridge was constructed, hence non-destructive and partially destructive tests were carried out on the structure to characterize its structural response. Overall, the resulting numerical model represents a solid basis for conducting more advanced analyses, such as those investigating the influence of time-dependent phenomena on the long-term structural response of the structure.
Damage Identification in Masonry Wall Specimens: Shake Table Studies
Authors: Latha Lakshmi , Ray-Chaudhuri S
Published: June 2024

Over the past few decades, vibration-based structural health monitoring and damage detection have drawn significant research attentions world-wide. The major motivation for such a research emphasis is the need to develop reliable methods to monitor the performance of structures in real-time. Real-time or continuous monitoring is also beneficial for timely maintenance of structure and to avoid any undesired failure. In this study, the efficiency of a few vibration based damage detection approaches has been investigated for identifying damage in a few wall specimens of brick masonry structures. Masonry is one of the most common and oldest material which is being used for constructing buildings for many years. Like concrete, masonry is also a brittle and highly non-linear material with good compressive but poor tensile strength. In masonry structures, damage generally occurs in distributed fashion and the pattern of cracks is often very complex as compared to steel structures. In addition, damping changes with the level of damage. An experimental study using shake table has been performed on a few half-scale wall-specimens. A suit of ground motions were selected based on Indian Code specified design ground motion spectrum. These motions were then scaled from very low intensity to high intensity by introducing amplitude scale factor with respect to the code specified level. The purpose of varying intensity input was to introduce progressive damage when subjected to the these excitations. In between each scale change, shake table tests with low intensity white-noise motions were performed. The purpose of white noise run in between two consecutive level of excitation was to simulate an ambient vibration condition for system identification. The specimens and the shake table were instrumented with accelerometers and displacement sensors to measure the input and responses. Various vibration-based techniques such as frequency domain decomposition and natural excitation technique (NExT) coupled with Eigen realization algorithm (ERA) techniques have been used for extraction of modal properties. It has been found from the experimental results that damage level can be easily correlated with a few damage identification parameters.
Investigating the relation between complex mode shapes and local damage for structural assessment
Authors: Masciotta Maria-Giovanna , Pellegrini Daniele
Published: June 2024

Modal parameters define the inherent characteristics of real-world structures, being therefore employed as reference information for various purposes, including the assessment of structural damage, the evaluation of operational and environmental effects, and the calibration of realistic numerical models. Among frequencies, damping ratios and mode shapes, the latter have been proved far more effective in localizing structural damage given their spatial dependency on the nodal coordinates of vibrating systems. Most of modal analysis applications resort to the real part of these quantities for vibration-based damage identification of structural systems, assuming them as classically damped. However, the classical viscous damping assumption is often idealistic for real-world structures as the damping matrix cannot be considered as proportional to mass and stiffness matrices. It follows that the mode shapes of real systems are complex in nature, and their complexity level can vary with damage. Based on the above considerations, this work intends to shed light on the relationship between structural damage and modal complexity. Numerical investigations are carried out to track the variation of complex mode shapes in a multi-span bridge subjected to progressive damage scenarios and to infer about the generalization of a new index that relies on the variation of the imaginary content of complex eigenmodes to detect, locate and assess the structural damage.
System identification in time domain of flexible aircraft using panel methods
Authors: Paula Thiago Rosado de , Sarmento Andrew Gomes Pereira , Fernandes Vitor Paixão , Fisher Clécio , Machado Raphaela Carvalho , Silva Roberto Gil Annes da , Sandoval Góes Luiz Carlos
Published: June 2024

The motivation to accurately model the dynamics of flexible aircraft grew with the development of energy-efficient aircraft, consequently, great aspect ratio aircraft. The development of an accurate model that represents the flight dynamics of a flexible aircraft has been pursued by industry and aeronautical research organizations during the last decades. One of these approaches is to find a flexible aircraft model using systems identification methods. This research aims to apply an integrated model containing longitudinal and lateral directional rigid body dynamics, coupled to the first four flexible body modes, for identification and validation from flight test data. The Unmanned Aerial Vehicle (UAV) Eolo with the flexible wing is used during the experiments. Initially, a finite element structural model (FEM) based on beam elements, concentrated masses, and rigid bars was used. The quasi-stationary panel model based on the Vortex Lattice Method (VLM) was adopted for the aerodynamic model. Two diagonal matrices were used to correct the aerodynamic influence coefficients (AIC) matrix obtained via VLM before and post-multiplication for aircraft identification. The estimation of the main diagonal elements of each matrix was obtained through the Output Error Method in the time domain. A model validation analysis was carried out, which shows a good correlation between the model and measurement data. In conclusion, getting correction matrices instead of stability derivatives is beneficial because matrices can be used more directly during the aeronautical design and observe the behavior concerning loads.
Highly stable kinematic nonlinear simulations using a Taylor basis
Authors: Andersen S , Poulsen P N
Published: June 2024

The simulation of kinematic nonlinear systems is typically very time-consuming. The computational cost is primarily related to a time-consuming evaluation of the internal restoring forces performed before each integration step. Using basis projection is a way to reduce the computational cost and, thereby, the simulation time. The present work considers a novel Taylor basis that can significantly improve the stability of the central difference time integration scheme for kinematic nonlinear simulations. It is illustrated that the time step stability limit for a kinematic nonlinear simulation using Taylor basis projection is more or less identical to the analytical stability limit known from linear systems. Furthermore, an example shows that the time step stability limit in simulations using Taylor basis projection can be two orders of magnitude higher than the stability limit of a standard kinematic nonlinear simulation. Thus, Taylor basis projection has the potential to significantly reduce the number of time steps and, thereby, the computational cost.
AI-Based Surrogate Models for Multibody Dynamics Systems
Authors: Koutsoupakis J , Giagopoulos D
Published: June 2024

Advancements in computer sciences and technology allow for implementation of detailed numerical models of a system such as the Finite Element (FE) or Multibody Dynamics (MBD) models. Complex mechanical systems can easily be modelled in detail, yielding accurate results. This opportunity provided by these high-fidelity numerical models has led to the broad application of such methods in development and prototyping of mechanical systems, their optimization and fault analysis and so on. The capability of detailed modelling however usually comes at a great computational cost, with the simulation time needed for a problem in many cases rising exponentially, rendering these models impractical. This problem becomes even more profound when one considers the recent integration of model-based data in data-driven methods where a large number of datasets is usually required, and multiple iterations of the same model must be simulated in order to produce the desired number of samples. To mitigate these short-comings, surrogate modelling has been extensively used in applications including large systems or repetitive runs in the form of Reduced Order Models (ROMs) to reduce the computations time and render these simulation-driven methods more viable. Use of these ROMs however is limited to cases where low loss of information is ensured, and the features lost due to the model simplification are insignificant. The developments in Artificial Intelligence (AI) and its applications have demonstrated its potential to accurately describe the relationships between a model’s inputs and outputs and as such using an AI algorithm as a surrogate model is a promising alternative. A properly trained AI algorithm can usually fit to FE and MBD models and yield accurate results at a fraction of the computational burden. To this end, an AI-based surrogate modelling framework is proposed in this work, with application on an experimental gear drivetrain system. A detailed MBD of the actual system is initially constructed and optimized via a black box optimization method in order to better simulate the physical system. A variety of supervised AI algorithms such as regression models and Convolutional Neural Networks (CNNs) is then examined as a surrogate to the various mechanisms of the system, aiming to replace them with the goal of reducing the simulation time while maintaining the high accuracy and fidelity of the original model. The various algorithms are then compared in terms of time reduction and accuracy both to each other and to the initial MBD model in order to conclude to the best suited for the application. The results are also compared to the measured response data of the physical system to ensure the validity of the models and prove the viability of the proposed method through its use on a relatively complex model. The proposed framework provides an alternative to the commonly used ROM methods and the presented application acts as a benchmark case for its implementation to more complex systems and different operating conditions.
Parametric Study on Structural Damage Classification with Numerically Simulated Vibration Data
Authors: Seventekidis Panagiotis , Karyofyllas George , Giagopoulos Dimitrios
Published: June 2024

Monitoring the health and working conditions of critical structures and machines can prevent failures and arrange for effective maintenance schedules. Access to vibration data from states with damages is valuable in order to train models that can perform explicit classification of faults in later states. This usually requires expensive and sometimes not feasible destructive tests in various operating conditions. Recent works have employed numerical models in order to simulate such scenarios. However, simulated data carries usually systematic errors in terms of the originally identified structure on the healthy state. In the present work, a test structure of a simple truss is studied with a Finite Element Model for vibration data generation. Training data sets are generated containing different errors in terms of damping, stiffness and mode shape accordance in order to emulate real application faults. The training data sets are used after in a Convolutional Neural Network for damage classification. It is investigated how different simulation error sources affect the generalization in terms of correct damage case prediction on a reference data set. The results may aid in strategies for focus on specific FE model updating parameters in order to generate reliable simulated training data
Modeling error assessment of reduced-order finite element models for SHM: A case study of Milad Tower
Authors: Sanayei Masoud , Esfandiari Akbar , Vahedi Maryam , Behboodi Saeed , Dabbaghchian Iman
Published: June 2024

Condition assessment, model updating, and basic studies of large and complex structures subjected to static and dynamic loadings necessitate establishing a reasonably low order model to enhance computational efficiency. An essential requirement for the development of a low-order model is to preserve the main characteristics of the full-scale model within the frequency range of interest or the desired static and/or dynamic response. In this regard, a novel reduced-order model (ROM) is developed based on a full-scale model (FSM) built using commercial finite element analysis software. Utilizing the common lumped mass matrix can introduce mass modeling errors. Hence, a method is proposed to extract the reduced consistent mass matrix model (RCMM) for use in the ROM. The modeling errors in the proposed ROM is studied for comparison with the static and dynamic responses. It can curtail capability of parameter estimation to capture the physical behavior of the structure using the ROM. Modeling error simulations prior to actual field-testing is highly recommended to determine the feasibility of non-destructive tests for successful system identification. The Milad telecommunication tower is the sixth tallest tower in the world, with a height of 435 meters. Using the proposed method, the consistency of the generated ROM based on the RCMM is verified with the Milad Tower’s FSM. In this regard, displacements due to equivalent static wind loads, natural frequencies, mode shapes, slopes of mode shapes, and time history response for earthquake loading are compared. The proposed ROM assessments utilizing RCMM confirm the accuracy of the static and dynamic characteristics.
Critical Speed and Dynamic Response of High-Speed Railway in Ballastless Track
Authors: Wu Ying , fu Haoran , Bian Xuecheng
Published: June 2024

The current requirements for train speed are getting higher and higher. When the train increases to the critical speed, it will cause resonance of track and substructure, which will adversely affect the train driving safety. At present, ballastless track is widely used in high-speed railway, and the vibration characteristics is different from ballasted track. Based on 2.5D finite element method, this paper establishes the vehicle-track-subgrade coupling model to analyze the critical speed of ballastless track under different foundation conditions. The relationship between critical speed and shear wave velocity of homogenous and layered subsoil is obtained through parametric analysis. The results show that the critical speed of bal-lastless track under homogenous subsoil depends on the Rayleigh wave velocity of subgrade. Besides, the presence of subgrade can improve the critical speed to be greater than the Ray-leigh wave speed of homogenous subsoil. Moreover, the critical speed of ballastless track un-der layered subsoil is influenced by the shear wave speed ratio of adjacent soil layers. Finally, the proposed empirical formula is of guiding significance for the construction of ballastless track.
Prediction of Ground and Building Vibrations Induced by High-speed Trains using a 3D Coupled Numerical Model Based on a Spectral Element Analysis Code
Authors: Feng Duo , Paolucci Roberto , Mazzieri Ilario
Published: June 2024

Controlling the vibrations induced by high-speed trains on environmental infrastructures, especially buildings situated along railway tracks, is an essential demand and a challenging task. In order to accurately predict the dynamic response of the ground and adjacent buildings to railway-induced vibrations, we conduct numerical validation based on an existing in-situ model test in Portugal. This validation is done using the spectral element numerical code SPEED, developed at Politecnico di Milano, which considers a fully coupled 3D model of both the ground and building. The mechanical parameters of the track structure, modeled by the beam on elastic foundation, are obtained by iteratively calibrating the analytical dynamic receptance curve according to the experimental data. We use a multi-objective optimization-based method to estimate the equivalent rectangular sections of building structural components. The recorded dynamic vertical responses of the nearby ground and building slab under the excitation of 219 km/h moving trains are compared with the numerical results. Specific attention is paid to the frequency range that dominates the dynamic response of the building to discuss the accuracy of the results.
Under ballast mats as mitigation measure for structure borne noise from railroad – assessment of effect on track deflection
Authors: Norén-Cosgriff Karin , Brekke Arild , Ekblad Alf , Aasen Trygve
Published: June 2024

The limit values commonly used in Sweden and Norway for structure borne noise from railroad are strict when seen in an international context. At the same time, tunnels with low coverage are regularly built through densely populated areas, which can cause complaints about high structural borne noise levels in nearby dwellings. Traditionally, ballasted tracks are used in most railway tunnels in Norway and Sweden and under ballast mats (UBM) are the usual structure borne noise mitigation measure. Since UBMs that meet technical regulations for rail in many cases do not provide sufficient effect, dispensations have been granted for the use of softer ballast mats in some projects. However, there is limited information about the effect of softer UBMs on maintenance and about whether soft UBMs lead to excessive rail deflections, which could affect the track adversely. There is therefore a need for more knowledge about how UBMs affect the track and especially at higher speeds. When assessing the effect of UBMs on the track, both information about the track displacement amplitude and the shape of the deflection curve is important. As a first step, a pilot study has been carried out to find a suitable method to measure rail deflection, which can be used for long-term monitoring in tunnels with UBM to gather more information. Three measurement methods were compared in a laboratory test rig: Linear Variable Differential (LVDT) displacement sensors, Fiber Bragg Grating (FBG) optical strain sensors, and high sensitivity low frequency accelerometers. The results indicate that by using a high-sensitivity, low-frequency (DC) accelerometer in combination FBG strain sensors, both an accurate determination of the displacement amplitude and information about the shape of the deflection curve can be obtained.
Vibration mitigation using seismic metamaterials on layered soil
Authors: Carneiro David , Kabirian Zohre , Reumers Pieter , Lombaert Geert , Degrande Geert
Published: June 2024

This paper investigates how the soil profile affects the vibration mitigation performance of seismic metamaterials in a wide frequency band (1 – 80 Hz). A 3D coupled finite element - boundary element (FE-BE) model with an efficient substructuring method is developed to analyze the vibration reduction performance of seismic metamaterials on top of a layered soil. Resonators are modeled as single degree of freedom systems on top of square concrete surface foundations. The response of uniform and graded metasurfaces on a homogeneous and layered halfspace due to harmonic point load are compared. The narrow band gap obtained for a uniform metasurface on a homogeneous halfspace is widened over a broader range of frequencies (40 – 70 Hz) using inverse metawedges. For layered soil conditions, vibration mitigation in a wide frequency band still emerges using metawedges. Their efficiency, however, is reduced.
On the improvement of design space subsets formulation for iteratively optimizing structural systems
Authors: Khalid M A , Bansal S
Published: June 2024

Structural optimization is the process of identifying the optimal set of design parameters for a structural system. Optimization techniques provide an effective approach for rationally improving structural engineering design, both for the structural system with deterministic and uncertain parameters. It is unanimously agreed that in engineering design applications, knowledge about a planned system is never comprehensive. These uncertainties resulting from incomplete information are often assessed probabilistically. In this probabilistic framework, the system design process is referred to as stochastic system design, and the concomitant design optimization problem is alluded to as stochastic optimization. The stochastic optimization process has been widely used in civil, mechanical, and aeronautical engineering designs. Stochastic system optimization includes two stages where initially the performance measure is approximated either by Taylor series approximation or the metamodels, and in the second stage, the approximated performance function is optimized by implementing the available optimization techniques such as nonlinear programming methods, gradient-based methods, metaheuristic methods, etc. Approaches available in literature can effectively take into account the uncertainties, but still, achieving higher accuracy and lower computational cost remains a challenging task for designing complex and realistic structural systems. To obliviate these aforementioned limitations, a simulation-based approach known as Stochastic Subset Optimization (SSO) is found to be very effective. The basic principle in the original SSO is to reduce the design space size iteratively, which has high plausibility of containing the optimal design solution. However, the success of the approach depends on the shape selection of the design space while implementing the SSO. Therefore, in the present study, the dependency of the original SSO over the selection of the shape of the design subset is overcome by exploring the design space based on the density of simulated design samples with the design space. This improves the applicability of the SSO to the complex, realistic problem. Two benchmark optimization problems: a 2-dimensional bowl-shaped sphere function and a helical compression spring design, are solved with the proposed approach to demonstrate the efficiency of the proposed approach.
Accurate frequency response function estimation using noise measurements in experimental modal analysis
Authors: Steffensen M T , Tcherniak D , Thomsen J J
Published: June 2024

In experimental structural dynamics, reliable estimation of Frequency Response Functions (FRF) is important to correctly characterize a mechanical system. In Experimental Modal Analysis (EMA), the FRFs are used as input to a modal parameter estimation algorithm to obtain the modal characteristics of the system. Errors due to noisy measurements are inevitably present in the FRFs and propagate to the modal parameters. A consistent FRF-estimator with low uncertainty is therefore needed. Different FRF estimators have been proposed with some consistency when certain noise-related assumptions are fulfilled (H1, H2, etc.). To choose the appropriate frequency response function estimator, information about the noise in the experimental setup is desirable. In this work it is shown how to use measurements of noise, to characterize different noise components in the experimental setup and determine the appropriate number of averages needed for the experimental setup. The identified noise components can be used to identify the main source of uncertainty in the experimental setup and which FRF estimator to use.
Intelligent Automatic Operational Modal Analysis: preliminary results
Authors: Rosso Marco Martino , Aloisio Angelo , Marano Giuseppe Carlo , Quaranta Giuseppe
Published: June 2024

Within the structural health monitoring (SHM) field, consistent research efforts have been invested in developing automatic vibration-based indirect methodologies for inspecting existing heritage conditions. Current trends are mainly focused on output-only automatic operational modal analysis (AOMA), specifically throughout the stochastic subspace identification (SSI) technique among others. In the literature, a widespread workflow is implemented in a four-step solution: choice of the SSI control input parameters, computation of stabilization diagrams, stable poles’ alignments detection, and their final clustering. However, the so far proposed solutions have not provided yet complete answers to some challenging and still open questions. For instance, an arbitrarily poor initial choice of the SSI control parameters may jeopardize the entire procedure. Therefore, in the current study, the authors present a novel intelligent-based AOMA framework in a machine learning perspective. Specifically, random-forest-driven Monte Carlo sampling of control parameters represents a promising intelligent way to automatically choose the proper SSI control parameters. Furthermore, the recurrent stable physical poles in the stabilization diagram among the Monte Carlo simulations deliver some special insights about mode shape confidence intervals. A numerical benchmark is herein analyzed illustrating some preliminary results and potentials of the proposed methodology.
Analysis of the dynamic behavior in a masonry dome in the city of Florence: Chiesa di Santa Maria del Fiore’s Dome
Authors: Vitorino S , Corazzi R , Doz G
Published: June 2024

Masonry construction has been practiced for thousands of years, being an important part of the world’s cultural heritage, containing sociological, economic, cultural and political elements of the place where it is inserted, physically offering us the opportunity to research and learn about the past. The analysis and prediction of historical structures behaviour over the years constitute a fundamental field of research to perpetuate the construction methods and the cultural heritage of civilizations. Such analyses involve not only the static aspect of the constructions but must also include the seismic action, not only due to the possible damages generated to the structure, but also, to the uncertainties associated with the occurrence of this phenomenon in the patrimonial and social security. In this context, the urban area of the Italian municipality and capital of Tuscany, Florence, which became a symbol of the Renaissance during the early Medici period and has the greatest concentration of universally renowned works of art associated with events of universal importance, is located in a seismic zone, with episodes of earthquakes in May 2022, with a magnitude of up to 3.7Mw. Thus, the present work aims to numerically analyse the dynamic behaviour and safety of the main masonry dome in the historic center of Florence: Dome of Santa Maria del Fiore’s Cathedral. For this, it was used the structural analysis software by the finite element method ABAQUS, and the numerical models were validated using the results of experimental analyses, present in the literature. The final model, which adequately reproduces the experimental results, can be used as part of a permanent monitoring system for the structural health of the dome and the prevention of possible damage.
An application of different surrogate models to model updating of a heritage structure
Authors: Rosati I , Fabbrocino G , Rainieri C
Published: June 2024

The preservation of historic structures is of primary importance due to their significant cultural value. However, destructive tests as well as invasive interventions should be as much limited as possible. In this contest, Finite Element model updating can be applied as a non-destructive method to indirectly estimate selected unknown parameters through numerical model calibration. To this aim, an inverse problem has to be solved by minimizing the gap between corresponding experimental and numerical estimates of modal parameters. However, the application of Finite Element model updating is usually associated with large computational efforts. These can be reduced through the choice of a suitable surrogate model. Douglas-Reid method and Response Surface method are frequently applied to this aim due to their relatively simple quadratic formulations. In spite of the similarity of the mathematical formulation of the surrogate models in the two cases, the methods show some peculiarities affecting their application and, in some cases, their performance. The present paper illustrates an application of Douglas-Reid method and Response Surface method to a historical building, reporting a comparative assessment of the two approaches in terms of computational time and model updating results.
Dynamic monitoring of the Temple of Neptune in Paestum (Italy) - Preliminary results
Authors: Petti L , Lupo C , D’Angelo T
Published: June 2024

This paper focuses on an experimental monitoring system developed for the Temple of Neptune in Paestum within a joint research project carried out by the Department of Civil Engineering (DICIV) at the University of Salerno and the Archaeological Park of Paestum and Velia (PAEVE).This monitoring system is an innovative seismometric network consisting of mechanical and electronic components of high sensitivity and precision, allowing the assessment of the static and dynamic response of the structure in order to monitor its evolution over time and support proactive maintenance activities. In particular, the paper presents the monitoring network and discusses the preliminary results highlighting the contribution that such an innovative system can provide to a broader maintenance process. The results confirm the high level of accuracy and stability of the overall system, as well as preliminary correlations between the temple’s daily response and weather changes such as temperature.
An Experimental Investigation Into Non-Contact Measurements for Leak Detection Using a Commercial Camera to Measure Vibration
Authors: Campos B C , Brennan M J , Gonçalves P J P , Iwanaga M K , Rustighi E , Matos P H M C , de Almeida F C L
Published: June 2024

Leaks in water distribution systems are a major problem as a large amount of water is wasted between treatment plants and consumers. Water supply companies use different strategies to identify and locate leaks in their pipe networks, among which, vibro-acoustic methods and devices (i.e. listening sticks, geophones, and leak noise correlators) are the most popular. Although single-point listening devices are cheap and simple to use, they rely on the operator’s hearing training. Moreover, this may lead to a search based on trial and error as only vibration intensity is used, so no information regarding the leak direction is available to aid in its location. Leak noise correlators, however, use two sensors and a leak can be pinpointed by estimating the time of flight between the two measured signals together with knowledge of the speed at which the leak noise propagates. These sensors need to be directly placed on the pipe or a pipe fitting. This paper concerns an investigation of a new technique, where leak noise signals measured using cameras (non-contact measurements), are pre-processed using computer vision techniques to extract meaningful information regarding vibration due to a leak. Here, this is conducted in controlled conditions by using a test bench that simulates the vibration response of a buried pipe at two measurement positions. Tests are carried out to evaluate the camera sensitivity regarding the distance from the signal source, lighting, contrast intensity, and the relation between image resolution and detection of a simulated leak are performed. The results are compared to classic contact measurements made using accelerometers, showing that the proposed technique is promising for leak detection. Moreover, this comparison is conducted using classical signal processing tools such as Power Spectral Density (PSD), modulus and phase of the Cross-Power Spectral Density (CPSD), coherence and Cross-Correlation Coefficient (CCC).
On the identification of aerodynamic derivatives using forced vibration in active grid generated turbulent flow
Authors: Kildal Oddbjørn , Petersen Øyvind W , Øiseth Ole
Published: June 2024

Aerodynamic derivatives are widely used to model the self-excited forces on bridges and for estimating the corresponding flutter stability limit. It is currently unclear to which degree the aerodynamic derivatives of a cross-section depend on the presence of turbulence in the incoming flow. However, it is believed to depend on the cross-section. In this study, wind tunnel experiments were conducted with forced vibration testing to investigate whether aerodynamic derivatives for a twin deck cross-section changed with increasing turbulence and whether longer measurement periods would yield less uncertainty in the estimated aerodynamic derivatives. Critically, large scatter in the wind tunnel experimental results was observed. Numerical simulations were run to investigate the uncertainty of aerodynamic derivatives related to turbulence and the length of the measurement period. It was shown that the presence of buffeting forces might disturb the identification of aerodynamic derivatives and that the uncertainty of the aerodynamic derivatives decreases for longer measurement periods. Real changes in aerodynamic damping due to turbulence are shown to be probable despite the shortcomings of the system identification procedure.
Design, Wind Tunnel Tests, Normative and Theoretical Approaches of the ARC MAJEUR Subject to Vortex Shedding
Authors: Palm A , Duchêne Y , de Ville de Goyet V , Denoël V , Andrianne T
Published: June 2024

The monumental work of art by Bernar Venet, called ‘Arc Majeur’ wraps the Belgian motorway E411 at Lavaux-Ste-Anne, offering drivers an unmissable landmark in the landscape. This sculpture is a curved steel structure with a height of 60 meters and a 2.25 meters square section. Due to its slenderness, lightness and low vibration frequencies, the structure is very sensitive to wind excitations and mainly to vortex induced vibrations (VIV). After the presentation of the design and the main properties of the structure, the paper presents two approaches to estimate VIV amplitudes. The first one details the mathematical models of VIV included in the Eurocode and several theoretical approaches. The second approach compares the mathematical models to the results of experiments conducted in the wind tunnel facility of the University of Liège. The influence of several parameters is investigated. The experiments revealed lower VIV amplitudes than the theoretical approaches. As the Arc Majeur cannot withstand the fatigue induced by the VIV, it is mitigated by increasing the damping ratio by adding a tuned mass damper (TMD) at the top. Due to the vital importance of its operation, an online processing is developed to verify that the damper operates as intended.
Alongwind dynamic response of slender vertical structures: thunderstorm outflows vs extra-tropical cyclones
Authors: Roncallo L , Tubino F , Gimondo M
Published: June 2024

This paper studies the maximum dynamic response of a slender vertical structure subjected to thunderstorm outflows and provides a comparison with synoptic events. A reinforced concrete telecommunication tower is considered as case study. The thunderstorm wind speed is modelled as sum of a slowly-varying mean and nonstationary turbulent fluctuations with a vertical nose profile, while for synoptic wind the Italian CNR Guideline is adopted. A reference wind speed with 50 years return period is considered for both the thunderstorm and synoptic events, based statistical analyses carried out on in previous studies. In view of the results outlined for the considered structure, the thunderstorm wind loading, which is currently not accounted by codes and standards, can be more demanding than synoptic events.
Multimodal aeroelastic analysis of suspension bridges with aerostatic nonlinearities
Authors: Russo S , Piana G , Carpinteri A
Published: June 2024

A one-dimensional (1D) continuum model for the multimodal aeroelastic analysis of suspension bridges is presented which refines a previous model by some of the authors. The classical linearized equations governing the (self-excited) bridge vertical and torsional oscillations are enhanced to include geometric stiffness contributions related to the steady lift and drag forces. A multi-degree-of-freedom (MDOF) system is obtained by Galerkin method and, for increasing values of wind speed, the damped linear dynamics, modulated by both the steady and the self-excited aerodynamic forces, is studied in the complex field. Stability thresholds for divergence and flutter are determined by the classical Lyapunov dynamic criterion. Selected engineering case studies are considered to demonstrate the capabilities and the validity of the proposed model and of the relevant numerical code. In a comprehensive dynamic framework, the method allows for: (i) determining the variation of the bridge mode shapes and frequencies for increasing values of wind speed, including an effective description of the coupling between the two displacement components as well as the interaction between different vibration modes; (ii) detecting both single-degree-of-freedom (i.e. damping-driven) and coupled (i.e. stiffness-driven) flutter instability; (iii) detecting static divergence instability; and (iv) investigating geometric nonlinearities associated with the aerostatic load.
Bayesian Statistics to determine Aerodynamic Admittance based on measurements at a high-rise Building
Authors: Kemper F.H. , Geurts C.P.W.
Published: June 2024

For the modeling of stochastic structural responses due to wind gusts, it is reasonable to make elementary assumptions for the aerodynamic admittance. However, there are still a large variety of corresponding models, and there is a lack of validation and reliable model estimation studies based on real data. In this paper, real data from a high-rise tower in Rotterdam are used to identify the aerodynamic admittance (size-effect and joint-acceptance functions, SEF and JAF) using inverse modeling based on Maximum Likelihood Estimates (MLE), Markov-Chain Monte Carlo (MCMC) sampling, and a Bayesian posterior (BP) implementation to find parametric models for both aspects of the aerodynamic admittance.
Quadratic Basis Pursuit in Model Updating of Underconstrained Problems
Authors: Bernal Dionisio , Ulriksen Martin D.
Published: June 2024

This paper considers the extraction of sparse solutions using the L1 minimization surrogate for two approximations of the nonlinear relation between parameters and features; in the first, nonline-arity is discarded altogether and in the second a quadratic relation is assumed. The associated algorithms are the well-known Basis Pursuit (BP) and the more recently introduced Quadratic Basis Pursuit (QBP). It is contended that measuring success by comparing the extracted solutions with the underlying truth is unnecessary, as all that’s needed from the extractor is to identify a sufficiently small parameter set to render the problem determined. Specifically, with p as the number of features, one is interest in the likelihood that the algorithm leads to Ω
p
∩ Θ = Θ, where Θ = true set and Ω
p
= set of the largest p non-zero entries in the solution. When operating in this manner the disruption that nonlinearity brings into the BP solution derives only from the nonlinearity induced rotation of the right-hand side away from the span of the column partition of the Jacobian for the non-zero entries. From this perspective one expects performance to deteriorate only weakly with the extent of damage and this result is numerically con-firmed. It is found that although QBP has the quadratic premise as an advantage over BP, the perfor-mance in simulations, due to the difficulty in obtaining optimal values for the free parameters (and the fact that damage extent prediction was not relevant) proved somewhat poorer than BP.
Cone penetration tests and dynamic soil properties
Authors: Schepers W , Kulke D
Published: June 2024

Current standards like ISO 14837-32:2015 and DIN EN 1998-1/NA:2021 as well as prEN 1997-2:2022 allow for using correlations between the results of in-situ soil penetration tests and shear wave velocity (or shear modulus) to determine soil properties to be used in dynamic analyses. While the ISO and prEN standards even provide some recommendations on specific correlations to be used, the DIN standard does not. Due to the statistical nature of such correlations their general applicability has to be verified. We collected data sets from test sites from Germany as well as New Zealand at which cone penetration tests (CPT) as well as seismic site investigation methods were conducted. These sites comprise sandy soils as well as clayey soils, mixed soils as well as glacial soils. We compare the results of several correlations between CPT results and shear wave velocity. The accuracy of such correlations is assessed with respect to the accuracy of seismic in-situ tests. It turns out that for clean sands such correlations between CPT and V
s have a similar order of variability as seismic in-situ tests conducted at the same site. The higher the fines portion of the soil, the higher the variability of the statistical correlations, and consequently the less the general applicability. For glacial soils and other special soil types usage of statistical correlations to determine dynamic soil properties is not recommended.
Wireless Sensor Network-Based Systems for Monitoring a Lifting Bridge
Authors: Kilic Gokhan
Published: June 2024

Assessing the health and condition of structures like bridges involves frequently using structural health monitoring (SHM). In the past, wire sensors had to be installed on bridge structures as part of the SHM process so that data could be collected and sent to a data gathering unit there. However, this study suggests switching out the conventional wire sensors with wireless ones to create a Bridge Health Monitoring System (BHMS) that is affordable, practical, and simple to install. A software translation program attached to the monitoring server is used by each wireless sensor. In a GSM LAN (Global System for Mobile Communications) environment, this monitoring server system has the ability to link and interact with other similar systems of that type. The evaluation approach provided by the BHMS is thorough, secure, and portable.
Dynamic Responses and Associated Permanent Deformation of Ballasted Trackbed Due to Train Passages at High Speed
Authors: Gao Zelei , Bian Xuecheng
Published: June 2024

The ballasted trackbed plays a crucial role in railway infrastructure. However, as train speeds escalate, it experiences heightened vibrations and substantial permanent deformation, posing a notable threat to normal train operations. This study is dedicated to investigating the dynamic response and associated irreversible deformation of railway ballast under varying train speeds, with a specific focus on particle-scale manifestations. To accomplish this, a comprehensive ballasted trackbed model, encompassing the entire transversal cross-section, was built using the discrete element method (DEM) with realistic polygonal elements. The DEM model underwent preliminary validation against measurements from full-scale model tests and was subsequently employed to simulate the mechanical behavior of the ballasted trackbed under various train speeds. The findings reveal that increased train speeds lead to vigorous shaking of ballast particles, manifesting as intense vibration at the macroscopic level of the track structure. The heightened particle activity indicates instability in the inter-particle contact network and distinctive particle migration. Consequently, a notable accumulation of permanent deformation occurs in the granular trackbed. Notably, once the train speed surpasses a certain threshold, there is observable migration of ballast particles beneath the sleeper towards both ends. This phenomenon results in the absence of a stabilized inter-particle contact network to support the upper train load, leading to rapid and significant irreversible deformation in the ballasted trackbed.
Monitoring of thermal deformations of a highway bridge: Comparison of geodetic measurements, finite element simulations and AI predictions
Authors: Lorenz R , Petryna Y
Published: June 2024

Structural Health Monitoring of civil engineering structures is experiencing an increasing progress in the last decades. The present work focuses mainly on static behaviour of a highway bridge due to environmental temperature effects. The first goal is to compare the results of the finite element simulations to the classical geodesy surveying measurements for deformation monitoring of a large, curved highway bridge. The second goal is to test the applicability of artificial intelligence (AI) methods to predict such deformations online without comprehensive computer simulations. In this context, it is also shown how AI can be used to compensate outage of the measurement system and as an element of a monitoring system for system change detection.
Real-world data-supported and higher-order element theory-enabled progressive damage model assembly
Authors: Pei Jin-Song , Chatzi Eleni
Published: June 2024

Dynamic responses of steel bolts anchored in concrete and subjected to cyclic loads are complex: Qualitative physical attributes include pinching, displacement drift and force-intercept. In fact, these attributes vary with time, involving uncertainties that can lead to different failure patterns. This study explores higher-order elements (HOEs), an emerging theoretical macro-modeling framework originated from electrical engineering and transferred to engineering mechanics by using physical analogies. This study proposes a systematic procedure for a new model formulation – a model assembly that is made up of three distinct modeling elements, a higher-order spring, higher-order damper, and loading-rate independent damper to capture pinching, displacement drift, and force intercepting, respectively. The two higher-order elements play significant roles to model responses of fatigue loading in two opposite directions each involving loading and unloading. To afford more physical insights, the higher-order spring is further formulated into a mem-spring, where new choices of state variables are employed. The proposed model formulation benefits both efficient simulation of time-varying dynamical systems and qualitative failure analysis. In addition, this study offers a case study to reveal a new utility of HOE theory. Two major datasets of anchoring blots are used to develop and validate the proposed modeling approach, while three minor datasets are used for a supplementary investigation. This study shows that, both qualitatively and quantitatively under ordered excitation, HOE can be employed with more modeling power and efficiency compared with existing models for progressive damage, and with the flexibility to interface with some existing models when needed.