No abstract is provided for this article.
Local Plastic Instabilities of Perforated Thin-Walled Bars – FEM Modelling and DIC Verification Andrzej Piotrowski, Marcin Gajewski, Cezary Ajdukiewicz Abstract. In this paper results of testing and modelling of perforated thin-walled bars of low slenderness are shown. Tested and modelled elements in general are used as structural elements for storage systems. In such case the […]
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The critical moment analytical expressions used in engineering design are based on the thin-walled beam model of warping torsion and the linear eigenvalue analysis (LEA) while the analytical formulation of the buckling curve equation follows the Ayrton-Perry model with the Maquoi-Rondal initial imperfection parameter. Using the equivalent geometric imperfection concept for the resistance prediction, the Maquoi-Rondal initial imperfection amplitude for lateral-torsional buckling is usually related to the equivalent minor axis bow amplitude or the twist rotation amplitude for the lowest eigenmode imperfection profile. Such concept is also used in this paper for the evaluation of the buckling resistance of beams in bi-axial bending. Recent investigations based on the so-called GMNA+ large displacements analysis have shown that the LTB critical moment evaluated with use of LEA needs to be modified in order to account for the fact that H-section slender beams may fail by developing large inelastic twist rotations, the effect that is not included in the elastic linear buckling theory. In the present study, the influence of critical moment predictions on the LTB resistance evaluation is dealt with and the analytical formulation is proposed. Comparisons of the buckling curve formulations are presented.
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The FWD is commonly used to conduct a non-destructive evaluation of the capacity of the pavement. The layered pavement is loaded locally by falling weight, and deflection at many points is recorded. Based on these results, knowing the pavement geometry, the mechanical properties of the pavement may be determined using the back-calculation approach. Some methods are used for back calculation, such as analytical, numerical, or ML. An analytical solution for a multi-layered structure leads to non-linear relationships for the thickness or stiffness of each layer, but gives an accurate solution. The other methods, like numerical or ML methods, are just approximation methods with different levels of accuracy. In this paper, the robustness of the XGBoost ML regression model in predicting mechanical and geometrical pavement parameters was estimated. The database was generated from a static analytical solution of an axially symmetrical problem implemented in the form of JPAV software and then explored by training regression models to predict moduli and thickness of pavement layers. Two other databases were created using PCA (Principal Component Analysis) and FDM (Feature Difference Method) to compare models trained with the complete deflection database. The results showed that models trained with the complete deflection database had the best average prediction performance compared to the other two. In contrast, models trained with the database pre-processed by PCA showed predicting performance similar to the previous models, but with a little precision loss. Models trained with the database pre-processed by FDM exhibited excellent prediction on some features but worse on the rest.
This paper discusses different aspects of analytical and numerical modelling of the buckling resistance of welded I-section columns subjected to axial compression. The section considered is of class 1 that implies no local buckling affecting the column performance. The proposed analytical formulation of the buckling resistance is based on the so-called Marchant-Rankine's-Murzewski approach (M-R-M approach). The model proposed is of a 2D type and is a simplification of the 3D one that has recently been presented by the authors. The parameters of equivalent stress-strain model of the postwelding steel are calibrated in two stages of the best fit approximation procedure and with use of numerical results of the finite element simulation of the buckling resistance. In the first stage, the postyielding inelastic tangent stiffness parameter ξ E,eff is evaluated with fixed value of the first yield parameter ψ eff = ψ com . A target of the second stage is to assign the best fit value of the first yield parameter ψ eff and the imperfection factor n that allows for accounting the effect of geometric imperfections.
No abstract is provided for this article.
Two theoretical models for anisotropic elastic road meshes (grids) together with their isotropic approximations are proposed. In these models some elements of mechanics for fibrous composite materials and optimization theory were used. Grids approximation models can be used in any standard road pavement design software where the model of layered elastic or viscoelastic half space is on a theoretical basis. For the covering abstract see ITRD E157233
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<ns3:p>The article discusses the impact of seal failure in insulating glass unit (IGUs) and the resulting loss of filling gas on deflections as well as the operational safety of glass structures, with particular emphasis on roof glazing and skylights. The main objective was to demonstrate the critical role of the gas in ensuring composite action between the glass panes when transferring external loads. Numerical analyses were performed in the RF-Glass module of the RFEM 5 software for typical insulating glass configurations. The behavior of the glazing unit in a fully sealed state was compared with the situation after seal failure and gas loss, where the external load is borne solely by the outer pane. Additional comparisons of various structural variants (different thicknesses, tempering, lamination of inner and outer panes, as well as single-chamber and double-chamber arrangements) made it possible to assess how modifications to the glazing composition affect stiffness and stress levels. The results highlight that gas loss significantly worsens the working conditions of the outer pane and may lead to exceeding the ultimate limit state of load-bearing capacity. In extreme cases, this can result in sudden failure of the element and pose a risk to user safety. The article emphasizes the need for special care regarding the airtightness of insulating glass units and the rational selection of layer configurations in the design of modern metal-glass structures.</ns3:p>
In the paper two classes of poly-convex stored energy functions for transversally isotropic hyper-elastic materials have been proposed. Within these classes, a simplified model of hyper-elastic materials with an isotropic matrix reinforced with fibre family was derived and implemented in finite element software ABAQUS/Standard. The two numerical examples proving correctness of the implementation and showing its positive physical features are presented.
The article presents the results of research aimed at evaluating the properties of asphalt binders recovered from material obtained during milling of polymer-modified SMA layers. Laboratory tests were carried out on asphalts recovered from RAP, on blends in defined proportions with fresh polymer-modified binders, as well as on binders recovered from SMA mixtures containing reclaimed asphalt. The study’s scope included standard classification tests of polymer-modified binders and an assessment of rheological properties using the MSCR method. An analysis of the results was performed to evaluate the condition of the recovered binders and to select binders for blending with fresh PMB and reclaimed aggregates for the design of SMA mixtures with RAP. The analysis of blends and recovered binders enabled a relative evaluation of binder properties, indicating variants that may potentially require the application of rejuvenators. The presented research constitutes one of the stages of the rSMA2 project focused on the recycling of SMA layers.
This paper proposes two chemical activators that are used to prepare mixtures for pothole repairs based on reclaimed asphalt. Repair mixtures, especially those used as “cold” mixes, must be characterized by special properties because they are primarily used in the winter period, i.e., at low temperatures and high humidity. The proposed additives W1 and W2 affect the functional and rheological properties of asphalts. Therefore, their influence on the behavior of asphalt 35/50 in three states, i.e., non-aged, after technological aging, and after service aging, was examined. At the same time, the issue of determining the optimal mass content of additives in relation to the aged binder was undertaken using the original methodology applying the MSCR test. In the latter part of the paper, the influence of additives W1 and W2 on asphalt recovered from reclaimed asphalt (aged in real conditions) was also analyzed and asphalt mixtures for pothole repairs were made. For these mixtures, the average contact stresses and tensile strength were determined as a function of time and conditioning temperature, giving positive results in terms of practical application of the proposed solution. The obtained mixtures were successfully used to fill potholes in winter weather conditions.
