Ústav kovových a dřevěných konstrukcí

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    The Influence of Hot-Dip Galvanizing on the Mechanical Properties of High Strength Steels
    (MDPI, 2021-09-10) Šmak, Milan; Kubíček, Jaroslav; Kala, Jiří; Podaný, Kamil; Vaněrek, Jan
    Modern high-strength steels achieve their strength exclusively through the manufacturing process. Typically, hot-dip galvanizing is used to form a protective zinc layer on the steel parts of structures; nonetheless, the material is exposed to high temperatures during the process. This study aims to experimentally examine and evaluate the extent of change of the mechanical properties of high-strength-steel members. The effect was studied on specimens made of different types of steel with the yield strength ranging from 460 to 1250 MPa. For each type of steel, selected mechanical propertieswere determined on specimens with and without hot-dip galvanization, and the obtained results were mutually compared. Our study shows a significant impact of the hot-dip galvanization process on the mechanical properties of some high-strength steels.
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    Welded beam-to-column steel joints: Assessment of European design rules
    (Elsevier, 2024-03-30) Conde, Jorge; Freire, Fernando; Ljubinković, Filip; Vild, Martin; da Silva, Luís Simes
    Properly validated high-quality Finite Element (FE) models with experimental tests permit an accurate description of the load-deformation path and stress state of steel joints and are nowadays accepted as “experimental results”. Changes to the design of welded joints in Eurocode 3 are currently proposed that affect the resistance and stiffness of the components associated with the column web panel. This paper presents an assessment of the design formulations included in the current Eurocode 3, part 1–8, and its forthcoming update in terms of stiffness and moment resistance, compared against a large parametric study of strong-axis beam-column welded joints for open sections carried out using validated sophisticated FE models. The results show that both the old and new Eurocode formulations provide a large scatter and no big differences between both methods. Additionally, the presence of axial force in the column shows a clear increase in the ratio between design resistance vs numerical resistance that, particularly in the case of transversally stiffened joints, may be unconservative.
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    Numerical and experimental verification of column web in transverse compression
    (Elsevier, 2024-07-23) Balázs, Ivan; Pešek, Ondřej; Horáček, Martin; Vild, Martin
    This paper focuses on the problem of steel members of open double symmetrical cross-sections in transverse compression. First, the problem is introduced with examples of its application in steel structures of buildings and followed by the overview of selected substantial literature resources and current design codes provisions. The essential part of the paper is a presentation of results of experimental tests and advanced numerical analysis of members subjected to selected cases of transverse compression. Where possible, the results are compared with resistances obtained using provisions in currently valid design codes for steel structures. The influence of selected parameters on the resistance in transverse compression is quantified within the evaluation with specific attention paid to plate buckling of the web. Based on data obtained from the experimental and numerical investigations, the most notable findings are summarized.
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    Numerical design calculation of flush endplate connections at elevated temperatures
    (Ernst & Sohn GmbH, 2025-05-07) Der, Batuhan; Wald, František; Vild, Martin
    The fire design of bolted connections is a critical aspect of structural fire engineering, as the failure of steel connections under fire conditions can compromise the entire structure. This paper presents numerical design calculations of flush endplate connections using the component-based finite-element method (CBFEM) at elevated temperatures. The CBFEM models are developed and validated against experimental data, focusing on load-rotation behaviour, connection resistance, and failure modes under thermal stress. By integrating the component method with finite-element analysis, CBFEM provides a robust framework for simulating the behaviour of steel connections in fire. Additionally, the method is verified against Eurocode design specifications for further validation. The results demonstrate that CBFEM is a reliable and accurate approach for the fire design of bolted steel connections at elevated temperatures, offering precise predictions of connection performance and failure mechanisms.
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    Decision tree for local + global imperfection combinations in double-symmetric prismatic members – Practical recommendations in the framework of advanced analysis
    (Ernst & Sohn, 2023-01-30) Müller, Andreas; Vild, Martin; Taras, Andreas
    Better and simpler possibilities of structural optimization due to increasing computational power but also for reasons of environmental sustainability, the use of materials and their reusability lead to greater acceptance towards more advanced numerically intensive, so-called ‘design by analysis' methods like geometrically and materially non-linear analyses with imperfections (GMNIA). The general choice of imperfections and their combination in such models, especially for slender cross sections of intermediate length prone to an interaction between a global and local plate buckling, is crucial in terms of the reached load-bearing capacity. Annex C of EN 1993-1-5:2010 makes use of the ‘70 %-rule' for the combination of imperfection modes and amplitudes. This rule postulates that two GMNIA calculations should be conducted when local and global interactive buckling may be dominant; one with 100 % + 70 % of the maximum specified amplitude in either case. In addition, extended information is provided on the choice and combination of imperfections in the newly introduced and currently available draft of the prEN 1993-1-14:2020 (design assisted by finite element analysis). Although information is provided on how the local and global imperfections should be combined, it is not stated when it is relevant to consider those. Based on conducted GMNIA simulations on SHS/RHS (square and rectangular hollow sections) and I-shaped sections, this article presents general decision support on the choice of equivalent imperfections. On the basis of numerical analysis, the developed flow chart and design routine allow for the decision whether the consideration of the interaction of local and global imperfections is required or not.