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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. ...
 
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.
 
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.


 
An accurate method for fast assessment of under slab mats (USM) performance in ballastless track structures PDF Print E-mail
A. Zbiciak, C. Kraśkiewicz, S. Dudziak, A. Al-Sabouni-Zawadzka, J. Pełczyński - An accurate method for fast assessment of under slab mats (USM) performance in ballastless track structures, Construction and Building Materials, Vol. 300, 20 September 2021,

Abstract
The paper is devoted to testing, modelling and performance assessment of vibration isolation products applied in ballastless track structures. In the first part of the paper, results of laboratory tests of vibration isolation products, such as under slab mats (USM) and under block pads (UBP) are summarised. On their basis, the Fractional Zener Model (FZM) is calibrated and it is shown that the model properly covers the stiffness and damping characteristics of tested materials in a wide frequency range. Then, results of the finite element analysis performed in a frequency domain using the Abaqus code are presented, taking into account the frequency-dependent material characteristics. The analysis concerned a ballastless track structure with a discrete system of rail fastening (embedded block system – EBS) laid on USM. The proposed approach was compared with the simplified one, in which the frequency-dependence of material properties is neglected. The presented modelling methodology, based on outcomes of laboratory tests, makes it possible to compare various vibration isolation systems in a short time. Consequently, it can be considered as a useful engineering tool.
 
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