Ústav stavební mechaniky

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    Tendon optimization for prestressed concrete structures using genetic algorithms
    (ACHE, 2025-06-25) Houšť, Vladimír; Mašek, Jan; Eliáš, Jan
    The contribution presents a computer code that optimizes a prestress tendon force and geometry. The mechanical part computes time-dependent analysis of the prestress concrete structure taking into account shrinkage, creep, tendon relaxation, friction and anchor slip, i.e., all necessary components of prestress short- and long-term losses. The optimization part executes genetic algorithm with chosen parameters of the tendon geometry subjected to optimization with respect to mechanical and geometrical constraints. The minimized variable is prestressing force. A parametric study of a 3-span post-tensioned bridge deck is presented in the last section.
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    Forecasting approach of ultimate bearing capacity of underreamed anchor under local shear failure
    (Elsevier, 2025-06-01) Zheng, Bin; Bayat, Mahmoud; Shi, Yehui; Jiang, Yazhou; Qian, Xiangdong; Novák, Drahomír; Cao, Maosen
    The end resistance formula in the current industry specification has parameters that are difficult to determine precisely, resulting in estimated results often does not reflect the true condition of underreamed anchor. To address this problem, based on the elucidation of load transfer law when local shear damage occurs in the soil around anchor under vertical pulling action of underreamed anchor, a model of end resistance of underreamed anchor is proposed. The model can calculate the end resistance while avoiding uncertainty of parameters of current formula. Numerical simulations and field tests show that the proposed model significantly improves the accuracy of calculating end resistance of underreamed anchor.
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    Fatigue behavior of high strength steels under various levels of corrosion
    (Elsevier, 2024-02-01) Malíková, Lucie; Benešová, Anna; Al Khazali, Mohammad Sami; Seitl, Stanislav
    Propagation of a short fatigue crack directly from a corrosion pit is investigated within this work. A corroded rectangular specimen subjected to remote tensile cyclic loading is modelled via finite element method. Propagation of the angled crack is then controlled by both loading modes (I + II). A parametric study is performed to estimate the directions of further crack propagation for various geometrical configurations. Corrosion pit size is varied to simulate various levels of corrosion, and the analysis is carried out for a range of crack lengths and different initial crack inclination angles. Assumptions of linear elastic fracture mechanics are accepted, and classical maximum tangential stress criterion is applied to calculate the angles of crack deflection. Results obtained are discussed and are prepared to mutual comparison with observations of decrease of fracture mechanical/fatigue properties on real specimens subjected to relevant experiments.
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    Dual discrete and continuous meso-scale modelling of concrete
    (Vysoká škola báňská - Technická univerzita Ostrava, 2024-01-04) Mašek, Jan; Miarka, Petr
    The present paper is devoted to the development of a software equipment that allows to model composite materials by both discrete and continuous modelling approaches. The aim is to create a geometrical and topological representation of a discrete lattice particle model as well as its 1:1 twin counterpart as modelled by a continuum FEM model. Both representations capture the heterogeneous composite structure at the meso-level. The presented results illustrate the ongoing initial phase of the efforts of the team in advanced modelling of damage propagation within concrete.
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    The generalized Kelvin chain-based model for an orthotropic viscoelastic material
    (SPRINGER, 2024-03-01) Trcala, Miroslav; Suchomelová, Pavlína; Bošanský, Michal; Hokeš, Filip; Němec, Ivan
    We propose a constitutive material model to describe the rheological (viscoelastic) mechanical response of timber. The viscoelastic model is based on the generalized Kelvin chain applied to the orthotropic material and is compared to the simple approach given by standards. The contribution of this study consists of the algorithmization of the viscoelastic material model of the material applied to the orthotropic constitutive law and implementation into the FEM solver. In the next step, the fitting of the input parameters of the Kelvin chain is described, and at least a material model benchmark and comparison to the approach given by standards were done. The standardized approach is based on the reduction of the material rigidity at the end of the loading period using a creep coefficient, whereas the loading history state variables are not considered when establishing the result for a specific time step. The paper presents the benefits of the rheological model. It also demonstrates the fitting algorithm based on particle swarm optimization and the least squares method, which are essential for the use of the generalized Kelvin chain model. The material model based on the orthotropic generalized Kelvin chain was implemented into the FEM solver for the shell elements. This material model was validated on the presented benchmark tasks, and the influence of the time step size on the accuracy of model results was analyzed.