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In-Depth Verification of a Numerical Model for an Axisymmetric RC Dome PDF Print E-mail
Przemysław Czumaj, Sławomir Dudziak, Zbigniew Kacprzyk, In-Depth Verification of a Numerical Model for an Axisymmetric RC Dome, Symmetry 2021, 13(11), 2152;
online: https://doi.org/10.3390/sym13112152

Abstract
The designers of civil engineering structures often have to face the problem of the reliability of complex computational analyses performed most often with the Finite Element Method (FEM). Any assessment of reliability of such analyses is difficult and can only be approximate. The present paper puts forward a new method of verification and validation of the structural analyses upon an illustrative example of a dome strengthened by circumferential ribs along the upper and lower edges. Four computational systems were used, namely Abaqus, Autodesk Robot, Dlubal RFEM, and FEAS. Different models were also analyzed—two-dimensional (2D) and three-dimensional (3D) ones using continuum, bar, and shell finite elements. The results of the static (with two kinds of load—self-weight and load distributed along the upper ring) and modal analyses are presented. A detailed comparison between the systems’ and models’ predictions was made. In general, the spatial models predicted a less stiff behavior of the analyzed dome than the planar models. The good agreement between different models and systems was obtained for the first natural frequency with axisymmetric eigenmodes (except from the Autodesk Robot system). The presented approach to the verification of complex shell–bar models can be effectively applied by structural designers.
 
prof. Tomasz Lewiński na liście "Stanford Top 2% world scientists" PDF Print E-mail
Udostępniamy link do aktualnego zestawienia "Stanford Top 2% world scientists": https://elsevier.digitalcommonsdata.com/datasets/btchxktzyw/3 ,
które obejmuje tzw. top 2% : 186 178 pracowników naukowych całego świata wszystkich dziedzin,
w tym 957 osób z afiliacją w naszym kraju.

Z Wydziału IL PW na liście jest obecna jedna osoba:
nr 178908 Tomasz  Lewiński,

a z Politechniki Warszawskiej 48 osób.
Informacja na stronie Politechniki Warszawskiej>>.
 
Probabilistic Modelling of Bending Strength of Timber Beams with the Help of Weak Zones Model PDF Print E-mail
Ireneusz Czmoch, Probabilistic Modelling of Bending Strength of Timber Beams with the Help of Weak Zones Model, Periodica Polytechnica - Civil Engineering, 65(4), pp. 1295–1305, 2021

on line>> https://pp.bme.hu/ci/article/view/19228/9231

Abstract
The variability of longitudinal bending strength of timber beams due to the presence of knots and other defects is analyzed. The weak zones model of timber beam bending strength used in the analysis consists of short weak zones (knots or group of them) and strong sections of clear wood. The load bearing capacity of timber beams is defined as an extreme (minimum) value problem or as a first downcrossing problem. (...)
 
Bending-Free Lattices as Underlying Optimal Isotropic Microstructures of the Least-Compliant 2D Elastic Bodies PDF Print E-mail
Sławomir Czarnecki, Tomasz Łukasiak; Bending-Free Lattices as Underlying Optimal Isotropic Microstructures of the Least-Compliant 2D Elastic Bodies, Physica Status Solidi 2021
https://doi.org/10.1002/pssb.202100344
Abstract
This study puts forward a method of reconstruction of the suboptimal isotropic truss microstructures for the known distribution of Young's modulus and Poisson's ratio predicted by the Isotropic Material Design (IMD) method of minimizing the compliance (maximizing the stiffness) of a 2D elastic body. The varying underlying microstructures corresponding to the optimal designs are recovered by matching the values of the optimal elastic moduli with the values of the effective moduli of the representative volume elements (RVE) computed by the asymptotic homogenization method. ...
 
Nagroda PTMKM dla pracowników Zakładu PDF Print E-mail
Nagrodę Polskiego Towarzystwa Metod Komputerowych Mechaniki w roku 2021 (za osiągnięcia z roku 2020) w kategorii za „rozwiązanie zagadnień w zakresie mechaniki opublikowane w czasopismach” otrzymała praca:

R. Czubacki, T. Lewiński, Optimal archgrids: a variational setting, Structural and Multidisciplinary Optimization, 2020, vol. 62, nr 3, str. 1371-1393.


 
Vibrations of bars including transverse shear deformations and warping due to torsion PDF Print E-mail
S. Czarnecki, T. Lewiński - Vibrations of bars including transverse shear deformations and warping due to torsion, Archives of Civil Engineering, vol. LXVIII, 2, 2021, pp. 355-381.

Abstract
The paper deals with coupled flexural-torsional vibrations of straight prismatic elastic bars made of a linearly elastic isotropic and homogeneous material. One of the aims is to develop an effective method of modelling vibrations of train rails of cross-sections being mono-symmetric, taking into account warping due to torsion as well as transverse shear deformations. The Librescu-Song 1D model has been appropriately adapted to the above research aims by incorporating all the inertia terms corresponding to the kinematic hypotheses. The finite element(FE) program has been written and its correctness has been verified. The results concerning natural vibrations compare favourably with those predicted by 3D FE modelling using dense meshes. The paper proves that neglecting warping due to torsion leads to omitting several eigen-modes of vibrations, thus showing that the popular Timoshenko-like models are useless for the vibration analysis of bars of mono-symmetric cross sections.
 
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