Documents published in Scipedia

• Nonlinear seismic analysis of reinforced concrete structures using POD reduced order method

  N. Ayoub, W. Larbi, J. Deü

  eccomas2022.

  
  

  Abstract

  This paper presents an extension of the Proper Orthogonal Decomposition method (POD) to nonlinear dynamic analysis of reinforced concrete multistory frame structure where the material nonlinearity is modeled by the multi-fiber section. To test the effectiveness of this approach, we first perform a nonlinear dynamic analysis under a seismic excitation using a direct implicit time integration scheme. Then, based on structural response observations, POD modes were extracted and used to reduce the structural system subjected to different earthquakes. A comparison was made between full model and reduced model analysis in order to assess the effectiveness of this technique.

  Abstract
  This paper presents an extension of the Proper Orthogonal Decomposition method (POD) to nonlinear dynamic analysis of reinforced concrete multistory frame structure where [...]

  • 8
  •  read

• Simulation of non-round particles in tribological three-body systems

  R. Bilz, K. de Payrebrune

  eccomas2022.

  
  

  Abstract

  Particles between the contact interfaces of two components in relative motion are present in many technical applications and can strongly influence the system behavior. In this context, the focus is often on the investigation of wear and damage. In addition to such undesirable phenomena, however, there is also the targeted use of hard particles, for example in the lapping process. In lapping, hard particles are intentionally inserted between a lapping disc and the workpiece surface to be processed in order to cause material removal with the help of the particles and to improve the morphology of the workpiece surface for certain applications. Many simulations of such tribological systems are based on the assumption of spherical particles. However, both, size and shape of the particles have an essential effect on the system behavior. Here, an approach is presented in which hard, arbitrarily shaped particles in tribological contacts can be studied a priori using the finite element method by performing indentation simulations for various particle orientations. Based on the results, an orientation-dependent particle model is created for simulations of the overall system, which includes particles in narrow gaps. This modular design allows direct control in the implementation of phenomenological effects and new insights into the behavior of such systems, as well as the estimation of the resulting surface topography.

  Abstract
  Particles between the contact interfaces of two components in relative motion are present in many technical applications and can strongly influence the system behavior. In [...]

  • 7
  •  read

• Molecular dynamics investigation of the effect of interlayer cavities of the structure of calcium silicate hydrate at the atomistic scale

  D. Tavakoli, M. Hajmohammadian Baghban

  eccomas2022.

  
  

  Abstract

  Calcium silicate hydrate (CSH) gel, as the most important component of hydration products, has the most significant effect on the properties of hardened cement paste. One of the most critical factors affecting the mechanical properties of CSH is the interlayer cavities in the gel. In this study, the effect of these cavities on Young's modulus of CSH has been investigated. For this purpose, first, the atomic structure of CSH is created, and then interlayer cavities with different dimensions are created inside the structure. For modelling, first, a super cell with dimensions of 3 × 6 × 1 times the unit cell of Tobermorite is prepared, and then each of these layers are placed on both sides of the new cell, and a space is created between these two layers. This distance is basically the cavity between the layers.

  Abstract
  Calcium silicate hydrate (CSH) gel, as the most important component of hydration products, has the most significant effect on the properties of hardened cement paste. One [...]

  • 9
  •  read

• Simulation and experimental investigation of tire tread block wear in three-body contact

  D. Nguyen, S. Kahms

  eccomas2022.

  
  

  Abstract

  On gravel roads, tires are not in direct contact with the surface. Particles of e.g. sand or stone contact directly with the tire and cause the tire to wear. During the sliding process, an interaction between particles and the tire occurs. On simplified conditions investigation of the movement of particles, friction and wear of a tire tread sample are done experimentally for different settings. Additionally, a finite element simulation is built up to simulate the wear of the tire tread sample under varying conditions. In this paper results from the experimental and numerical investigation of the wear of the tire tread sample are shown.

  Abstract
  On gravel roads, tires are not in direct contact with the surface. Particles of e.g. sand or stone contact directly with the tire and cause the tire to wear. During the sliding [...]

  • 14
  •  read

• Microscale numerical simulation of yarn tensile behavior using a high-fidelity geometrical fiber model extracted from micro-CT imaging

  A. Bral, L. Daelemans, J. Degroote

  eccomas2022.

  
  

  Abstract

  Air jet weaving, where the weft yarn is transported through the machine using air as propelling medium, is a popular weaving method due to its superior productivity, however at the cost of a high energy demand. The interactions between the weft yarn and the air jets are complex and not yet fully understood. Moreover, state-of-the-art techniques to simulate these interactions, are far from mature since the yarn is often simplified as a smooth and solid cylinder. Therefore, a novel multi-scale and multi-physics approach is proposed to simulate the interaction between weft yarns and air jets. Starting from microcomputed tomography (µCT) scans of a yarn used in air jet weaving, a high-fidelity microscale geometrical model is constructed, representing the yarn by its fibers. This geometrical model is used as input for microstructural simulations and will be used for flow simulations on microscale, where the aim is to extract local coefficients and as such characterize the yarn. These coefficients are then used as input for computationally cheap macroscale models, where the yarn is represented by its centerline containing the microscale properties. In a final stage, the macroscale structural and flow models will be coupled as to obtain a full FSI simulation of a weft insertion in an air jet loom. Current paper highlights the microscale geometry extraction of a fine wool fiber yarn of 28.8 tex. Consecutively, a computational framework is proposed to simulate the tensile behavior of this yarn, using the previously obtained microscale geometrical model. The resulting stress-strain curve of the yarn is compared to experiments and shows good correspondence.

  Abstract
  Air jet weaving, where the weft yarn is transported through the machine using air as propelling medium, is a popular weaving method due to its superior productivity, however [...]

  • 6
  •  read

• FEM analysis of FRCM strengthened RC columns exposed to fire

  R. Talo, M. Kyaure, S. Khalaf, A. El Refai, F. Abed

  eccomas2022.

  
  

  Abstract

  Reinforced concrete (RC) structures deteriorate over time and therefore, need to be strengthened. Despite the fact that RC structurtes have a decent fire rating, the performance of the strengthening system under fire exposure needs to be evaluated. One of the main restrictions associated with Fibre Reinforced Polymer (FRP) systems is their poor resistance to high temperatures, which originates from the combustible polymer matrix. Therefore, Fibre Reinforced Cementitious Matrix (FRCM) systems have been introduced due to their improved performance during fire exposure. The potential of Poly-paraphenylene-ben-zobisoxazole (PBO) FRCM to strengthen circular RC columns is evaluated using a nonlinear finite element analysis (FEA). The commericial software ABAQUS is used to develop 3D FE models to investigate the axial performance of the strengthening system. The modeling approach is performed by first conducting a thermal analysis to generate the nodal tempertaures. The second step of the model includes a displacement-controlled loading condition with imported nodal temperatures from the first model. The temperature dependent material properties are incorporated in both models. The modeling approach is validated against published literature and a parametric study is conducted on PBO FRCM strengthened and unstrengthened columns heated at durations of 1, 2, and 4 hours following the ASTM standard fire temperature-time curve. Results indicated a decrease in the axial capacity and stiffness of the strengthened and unstrengthened columns upon heating. Moreover, an increase in the columns' ductility due to the increase in temperature was observed. A decrease in ultimate strength of up to 78 and 68% was observed for the unstrengthened and strengthened columns respectively.

  Abstract
  Reinforced concrete (RC) structures deteriorate over time and therefore, need to be strengthened. Despite the fact that RC structurtes have a decent fire rating, the performance [...]

  • 17
  •  read

• Theoretical procedure to predict the local buckling resistance of aluminium members in elastic-plastic range

  V. Piluso, A. Pisapia

  eccomas2022.

  
  

  Abstract

  In the present research work, a theoretical approach to evaluate the ultimate resistance of aluminium alloy members subjected to local buckling under uniform compression is provided.

  Abstract
  In the present research work, a theoretical approach to evaluate the ultimate resistance of aluminium alloy members subjected to local buckling under uniform compression is [...]

  • 10
  •  read

• A coupled multiphysics approach for modelling in-stent restenosis

  S. Reese, K. Manjunatha, M. Behr, F. Vogt

  eccomas2022.

  
  

  Abstract

  Drug-eluting stents were developed to counteract the severe restenosis observed after bare-metal stent implantation. The risk of restenosis still prevailed due to the inhibitory effect of the drug on endothelial healing. The current work focuses on extending a multiphysics-based modeling framework to include the effect of anti-inflammatory drugs embedded in the drugeluting stents. An additional advection-reaction-diffusion equation governing the drug transport is introduced herein. Additionally, the effect of drugs, specifically rapamycin-based ones, on the proliferation of smooth muscle cells is captured. An optimal level of drug embedment is realized through the modeling framework.

  Abstract
  Drug-eluting stents were developed to counteract the severe restenosis observed after bare-metal stent implantation. The risk of restenosis still prevailed due to the inhibitory [...]

  • 72
  •  read

• Uncertainties of Parameters Quantification in SHM

  M. Miah, W. Lienhart

  eccomas2022.

  
  

  Abstract

  The uncertainties of parameters quantification due to various known and unknown conditions are crucial to understand structural health monitoring (SHM) systems. For instance, the amplitudes and the variation of loading conditions play a vital rule how the structural parameters are going to be changed. Hence, the aforementioned issue leads to an additional challenge in the area of SHM that requires attention. This study observed the behaviour of a steel bridge experimentally by employing multi-sensors scenarios e.g. accelerometers and laser triangulation sensor. The dynamical properties such as the peak (e.g. maximum-minimum) accelerations and displacements are evaluated. Additionally, the frequencies and damping ratio from the measured data of the tested bridge has been estimated by utilizing the fast Fourier transform (FFT) estimation. The outcome shows that the variation of input excitations (i.e., random, free-decay, extra-loading) effects the investigated properties as well as on their magnitudes considerably. Therefore, the findings suggest that before making a final judgement based on the identified/estimated properties from measured data, the underlying uncertainties need to be considered to avoid sub-optimal assessment strategy.

  Abstract
  The uncertainties of parameters quantification due to various known and unknown conditions are crucial to understand structural health monitoring (SHM) systems. For instance, [...]

  • 11
  •  read

• Multi-objective optimization for understanding tree design rules with finite element modelling.

  E. Moreno-Zapata, J. Cabrero-Ballarín, G. Ramos-Ruiz, G. Vargas-Silva

  eccomas2022.

  
  

  Abstract

  This research presents an optimization problem, which aims to understand the inherent design rules of the shape of a tree. It makes use of a classical optimization problem, the Nowacki beam, which consists of a cantilever beam with a point load at the end which seeks to obtain the lowest cross-sectional area and bending stress under a set of constraints [1]. Forrester et al. developed an algorithm to address this problem [2] by means of machine learning techniques. They began defining the beam properties and building a distributed random sampling plan and then computed the objective function and constraint functions. The process starts from an initially computed dataset that is used to train Kriging models, which are later used as a filling strategy, and genetic algorithms, as an optimization strategy. The result of each iteration is added to the dataset, and the process is repeated until convergence is found. In this way, the Pareto front with the optimal solutions is obtained. 

  Abstract
  This research presents an optimization problem, which aims to understand the inherent design rules of the shape of a tree. It makes use of a classical optimization problem, [...]

  • 12
  •  read