Ústav stavební mechaniky

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    Quantifying Uncertainty in Steel Member Reliability via Global Sensitivity Indices
    (2025-09-05) Omishore, Abayomi; Puklický, Libor; Kala, Zdeněk
    The study presents a comprehensive global sensitivity investigation focusing on the failure probability in torsion-loaded thin-walled steel members with uncertainties in material, geometric, and loading parameters. Two distinct sensitivity measures are scrutinised: one formulated through variance analysis of a binary failure outcome and the other based on discrete entropy. Total-effect indices, encompassing all interaction orders, are employed to assess variable importance. The results indicate that the long-term variable load significantly influences the uncertainty in structural reliability, while material and geometric parameters play a secondary role. The entropy-based measure accentuates the distinction between dominant and less influential inputs, while the variance-based approach captures a broader sensitivity structure. The findings underscore the impact of the selected sensitivity metric on input ranking and its implications for reliability assessment.
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    Support vector machines in reliability calculations of engineering structures
    (CRC Press, 2025-08-07) Sadílková Šomodíková, Martina; Lehký, David
    In the paper, a metamodeling approach based on support vector regression is studied as a promising tool in the assessment of reliability level. The method consists of two steps: firstly, an approximation of the original limit state function is performed, and in the second step a failure probability or reliability index is calculated with a simpler, approximated function using traditional simulation techniques. Two problems with explicit limit state functions are used to study the effectivity of the method. In order to be as effective as possible with respect to computational effort, a stratified Latin Hypercube Sampling simulation method is utilized to properly select training set elements. The accuracy of the method is analyzed and compared with other surrogate modeling methods, namely the polynomial- and artificial neural network-based response surface method, achieving comparable results.
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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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    Fractal Dimension Analysis of Three-Point Bending Concrete Test Specimens
    (EDP Sciences, 2020-10-05) Sobek, Jakub; Frantík, Petr; Trčka, Tomáš; Lehký, David
    The paper deals with the analysis of the fractal dimension of fracture surfaces of concrete specimens tested in a three-point bending configuration. Fifteen representative specimens were chosen out of a bigger set for the fractal dimension analysis. Their fracture surfaces were scanned by 2D optical profilometry and analysed by the FracDiM software created in the Java programming language. The resulting values of fractal dimensions for specimens of three different sizes are presented.
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    Cement based composites for thin building elements: Fracture and fatigue parameters
    (Elsevier, 2010-06-06) Seitl, Stanislav; Bílek, Vlastimil; Keršner, Zbyněk; Veselý, Jiří
    For application in civil engineering structures and also for strengthening existing structures cement-based composites are one of the most frequently used materials. Although many studies have been conducted on the mechanical properties of concrete from static tests, very little research has been reported on concrete fatigue properties. The purpose of this paper is to investigate the static and fatigue behavior of new cement-based composites, developed by ZPSV, a.s. a company producing bridge/train/building structures, are presented.