Documents published in Scipedia

• Dynamic displacement recognition of frame structures based on computer vision

  M. He, J. He, X. Sun

  WCCM2024.

  
  

  Abstract

  Displacement induced by external forces is one of the most intuitive variables for assessing structural safety. Traditional contact methods, such as deploying displacement sensors on structures, are often limited by objective factors. Non-contact methods, such as utilizing computer vision algorithms like optical flow estimation and feature matching, offer the advantages of rapid and accurate structural displacement acquisition, unaffected by the structure itself and quick deployment. However, enhancing the accuracy of displacement monitoring based on computer vision remains a focal point in this field of study. In this paper, based on experimental data from a vibration table testing a four-layer reinforced concrete framework under three different conditions, we propose a method for processing dynamic displacement data that combines non-contact and contact approaches. This method integrates dynamically recognized structural displacements based on computer vision technology with data recorded by acceleration sensors on the structure to enhance displacement monitoring accuracy. The research results demonstrate that our method can obtain structural dynamic displacements based on computer vision information, confirming the effectiveness and reliability of our approach.

  Abstract
  Displacement induced by external forces is one of the most intuitive variables for assessing structural safety. Traditional contact methods, such as deploying displacement [...]

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• Study of wind-induced vibrations on a trellis pylon controlled through an active mass damper system

  F. Ripamonti, S. Cii, A. Bussini

  WCCM2024.

  
  

  Abstract

  The rapid expansion of telecommunications infrastructure, driven by the deployment of the 5G network, necessitates innovative engineering solutions to ensure the reliability and stability of these critical structures. Steel trellis pylons, designed for hosting several telecommunication antennas, are particularly susceptible to wind-induced vibrations due to their slender profiles, high equivalent area exposed to wind loads and low structural damping. Such vibrations can lead to structural deterioration, signal disturbance, and, in severe cases, total structural failure. In this context, the need for effective vibration control measures is becoming more and more relevant. This paper underscores the complex challenge of windinduced vibrations in telecommunications pylons and the promising potential of AMD systems as a mitigation strategy. This study aims at advancing the state of the art by integrating experimental wind load measurements, modal analysis, and the application of AMD technology to a 50-meter-high steel trellis pylon. Through comprehensive analysis and numerical simulation, the effectiveness of AMD systems in enhancing structural performance and resilience under wind loading conditions is validated.

  Abstract
  The rapid expansion of telecommunications infrastructure, driven by the deployment of the 5G network, necessitates innovative engineering solutions to ensure the reliability [...]

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• Mathematical and experimental modeling of a Stockbridge damper used to suppress Aeolian vibration of transmission line conductors

  Z. Zondi, T. Ngonda, M. Kaunda, R. Stephen

  WCCM2024.

  
  

  Abstract

  The asymmetric Stockbridge vibration damper is commonly employed in overhead power cables to mitigate Aeolian vibration, which is the oscillation of conductor cables within the 3–150 Hz frequency range. The damper's effectiveness is determined by its resonant frequencies, which increase power dissipation to exceed the wind-induced power input. While the basic symmetric Stockbridge damper has two resonant frequencies, the asymmetric version can exhibit up to four. Previous studies have shown that changes in the counterweight's geometry can increase the natural frequencies. This paper presents experiments on a modified asymmetric damper and uses an analytical model from Vaja et al. (2018), to confirm their findings. employed in overhead transmission lines to mitigate Aeolian vibration

  Abstract
  The asymmetric Stockbridge vibration damper is commonly employed in overhead power cables to mitigate Aeolian vibration, which is the oscillation of conductor cables within [...]

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• Weight reduction in dynamically loaded systems through the effect of damping in bolted joints

  S. Roediger, C. Koenke, H. Beinersdorf

  WCCM2024.

  
  

  Abstract

  In order to reduce vibration amplitudes, the MFPA Weimar is investigating joint damping. The effect is based on the relative displacement between two components between which a surface pressure acts. In this case, the surface pressure is applied by a bolted connection. The damping behavior is dependent on normal force and amplitude. Decay tests clearly show that it is not possible to approximate the curves due to the viscous behavior (exponential decay function). The superposition with Coloumb's friction leads to a new damping model, especially in the initial range. The aim is to set up a numerical model in order to be able to take the local damping effects into account in the development of components. For this purpose, zero thickness elements (ZTE) are introduced into the joint in the FE simulation and provided with a constitutive model that can represent the energy dissipation. The ZTEs are parameterized as a function of material, surface pressure and surface roughness. The amplitude reduction, which is often achieved by a frequency shift of the natural frequencies via tuned mass dampers, is replaced and thus contributes to lightweight construction.

  Abstract
  In order to reduce vibration amplitudes, the MFPA Weimar is investigating joint damping. The effect is based on the relative displacement between two components between which [...]

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• Modeling of an oblique incident P-wave within a water saturated soil with the wave based method

  M. Lainer, G. Müller

  WCCM2024.

  
  

  Abstract

  In this contribution, a coupling approach between the Wave Based Method and an oblique incident P1-wave is presented. The approach is used to model a poroelastic halfspace with an empty canyon by applying Biot’s theory for low frequencies. The system’s response is compared with a reference solution from literature. Moreover, a second coupling approach is introduced to permit the modeling of a filled canyon. In the special case of a canyon filled with the material of the surrounding soil, the simulation results are compared with the underlying analytical solution

  Abstract
  In this contribution, a coupling approach between the Wave Based Method and an oblique incident P1-wave is presented. The approach is used to model a poroelastic halfspace [...]

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• Stochastic FE-BE method for homogenization analysis of 2D diffusion problems considering uncertainties of inclusion shape

  K. Koro

  WCCM2024.

  
  

  Abstract

  The stochastic method for homogenization analysis of diffusion problems considering uncertainties of inclusion shape is developed using a microscopic spectral stochastic BEM and a macroscopic FEM. The spatial variation of inclusion shape is modeled using KarhunenLoeve expansion with exponential-type covariance kernels. The characteristic function on a 2-D unit cell and the homogenized diffusion tensor are calculated using the spectral stochastic BEM. The macroscale diffusion problems are solved using the stochastic FEM with the polynomial chaos (PC) expansion. Through numerical tests, the expected value and the standard deviation of the concentration in macroscale problems and their distribution are investigated.

  Abstract
  The stochastic method for homogenization analysis of diffusion problems considering uncertainties of inclusion shape is developed using a microscopic spectral stochastic BEM [...]

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• Optimal design of graphene-reinforced composites using shunted piezoelectric systems for optimal vibration attenuation

  M. Daraki, G. Drosopoulos, G. Foutsitzi, G. Stavroulakis

  WCCM2024.

  
  

  Abstract

  . Smart structures exploit the synergy between several coupled physical phenomena to produce materials and structures with enhanced properties. Such structures incorporate integrated sensors and actuators, mechanical and electronic components and control. The design of smart structures is a multidisciplinary challenge, which is of high importance for viability and resilience of industry. Usage of piezocomposites with integrated nonlinear shunted circuits for vibration suppression improves effectiveness and accuracy of many high-value products. The finite element method is widely used to simulate the mechanical response of composite materials and multi-physics problems. In this work a numerical investigation is conducted on small scale beams aiming to improve their vibration response by applying piezoelectric shunted circuits. Finite element models are developed in MATLAB, simulating graphene-reinforced nanocomposite piezoelectric beams with shunted circuits under vibration excitations. Piezoelectric materials are applied to the beams to allow for the interaction between electric charge and mechanical deformation. In addition, shunted circuits, which are paired with piezoelectric elements, are used to provide damping (vibration suppression) of one or more critical eigenfrequencies. To derive the optimal vibration response, a particle swarm optimization (PSO) algorithm is adopted. Optimization is then aimed to minimize the vibration amplitude as well as optimize the mechanical and electrical parameters of the investigated system.

  Abstract
  . Smart structures exploit the synergy between several coupled physical phenomena to produce materials and structures with enhanced properties. Such structures incorporate [...]

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• Nonlinear interaction in composites using physics informed neural networks

  G. Stavroulakis, A. Mouratidou, G. Drosopoulos

  WCCM2024.

  
  

  Abstract

  Modelling of composites requires the consideration of various components that work together and interact in a linear and nonlinear way. Linear and nonlinear modelling in view of demanding needs, like representative volume element calculations within numerical homogenization and the advent of new tools, like physics informed neural networks, are reviewed in this article. In particular, a concept is proposed towards the implementation of a unilateral contact mechanics law within physics-informed neural networks. The theoretical framework and related applications are presented. Results indicate that the proposed deep learning approach can further be applied towards solving contact mechanics problems, considering the mechanical interactions between the constituents of composites.

  Abstract
  Modelling of composites requires the consideration of various components that work together and interact in a linear and nonlinear way. Linear and nonlinear modelling in view [...]

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• A nonoverlapping domain decomposition method for extreme learning machines solving elliptic partial differential equations

  C. Lee, Y. Lee, B. Ryoo

  WCCM2024.

  
  

  Abstract

  Extreme learning machine (ELM) is a methodology for solving partial differential equations (PDEs) using a single hidden layer feed-forward neural network. It presets the weight/bias coefficients in the hidden layer with random values, which remain fixed throughout the computation, and uses a linear least squares method for training the parameters of the output layer of the neural network. It is known to be much faster than Physics Informed Neural Networks. However, classical ELM is still computationally expensive when a high level of representation is desired in the solution as this requires solving a large least squares system. In this paper, we propose a nonoverlapping domain decomposition method (DDM) for ELMs that not only reduces the training time of ELMs, but is also suitable for parallel computation. In numerical analysis, DDMs have been widely studied to reduce the time to obtain finite element solutions for elliptic PDEs through parallel computation. Among these approaches, nonoverlapping DDMs are attracting the most attention. Motivated by these methods, we introduce local neural networks, which are valid only at corresponding subdomains, and an auxiliary variable at the interface. We construct a system on the variable and the parameters of local neural networks. A Schur complement system on the interface can be derived by eliminating the parameters of the output layer. The auxiliary variable is then directly obtained by solving the reduced system after which the parameters for each local neural network are solved in parallel. An initialization method suitable for high approximation quality in large systems is also proposed. Numerical results that verify the acceleration performance of the proposed method with respect to the number of subdomains are presented.

  Abstract
  Extreme learning machine (ELM) is a methodology for solving partial differential equations (PDEs) using a single hidden layer feed-forward neural network. It presets the weight/bias [...]

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• A performance analysis procedure based on corrected displacements to evaluate the seismic response of steel 2D frames

  J. Mendoza, B. Sensale, A. Canelas

  WCCM2024.

  
  

  Abstract

  In the proposed methodology, a load pattern is applied in a non-adaptive fashion to obtain the seismic response of two-dimensional steel moment resisting frames. The proposed methodology is based on the structural dynamics theory and consists of a single run nonlinear analysis. This invariant load pattern is formulated by considering higher mode effects with the use of an effective modal mass contribution factor. Also, part of the proposed procedure, a corrective factor is employed to adjust the displacements obtained from the nonlinear analysis ensuring that the drift values obtained from the corrected displacements are adequate. The procedure allows the analysis of the structural response, i.e, story displacement and story drifts. To evaluate the methodology a nine-story steel moment frame is analyzed. Material and geometric non linearities are considered for all the cases. The results are compared with the ones obtained by the Nonlinear time history analysis.

  Abstract
  In the proposed methodology, a load pattern is applied in a non-adaptive fashion to obtain the seismic response of two-dimensional steel moment resisting frames. The proposed [...]

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