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Settlement of piles with negative skin friction: design approaches according to part 3 of Eurocode 7
Full text linkPiles offer an effective solution for supporting structures in challenging ground conditions. However, ground settlement around deep foundations can induce negative skin friction, adding complexity to the geotechnical analysis and requiring careful consideration in both the pile settlement evaluation and structural integrity design. The article discusses the general recommendations provided by the informative annex of the revised Eurocode 7 version for designing piles subjected to negative skin friction. Using the Fellenius unified pile design concept, we provide a practical design framework for piles subjected to negative skin friction that extends the load-settlement curve methods proposed by Masopust, representing the standard pile design approaches in the Czech Republic. For examples presented, the introduced practical approach, also suitable for manual calculations, is in very good agreement with a refined calculation providing a nonlinear load-settlement curve
Anchor test and long-term monitoring of grouted anchors instrumented with Fiber Bragg Grating sensing technology
Full text linkGeotechnical monitoring of anchors provides fundamental data for analysis and evaluation to ensure safe environment. The use of optic fiber sensing technology, especially Fiber Bragg Gratings, brings many advantages of optic fiber sensors, such as high measurement accuracy, real-time continualmonitoring of deformation, on-line access to data and resistance against electromagnetic interferences. This article deals with anchor tests instrumented with FBG deformation gauges of the root and the tendon of the pre-stressed strand anchor in a test field in the Central Bohemian Region. First, the anchor with three optic cables with FBG sensors for measurement of axial deformation was subjected to six loading stages of the anchor test. Most of the sensors measured values of axial deformation less than 200 με and the root mobilisation was observed. Then, the measurement continued by 26-day long-term monitoring and a trend of a small increase of deformations occurred
On realizations of Lie algebras
Full text linkWe discuss and compare the main methods for constructing of Lie vector fields from the given Lie algebra structure constants. Generic realizations of three conformal algebras are obtained by the algebraic method and all realizations of the three-dimensional complex special linear algebra are obtained by the general method and compared with the finite-dimensional weight representations
Unitary generation of GHZ states
Full text linkEntangled states represent fascinating elements of quantum mechanics and quantum technology. Their generation is an interesting problem combining many techniques developed in quantum optics. Using algebraic properties of special transforms we derive the explicit form of the effective Hamiltonian that enables the generation of highly nonclassical states of the GHZ type. Such Hamiltonians belong to the higher order Hamiltonians often discussed in nonlinear quantum optics. We derive the form of the effective Hamiltonian that enables the generation of highly nonclassical states of the GHZ type
NMM 2024 Nano & Macro Mechanics
No full textThe 15th conference Nano & Macro Mechanics was held in Prague, in September 12, 2024.
The main objective of the conference is to bring together researchers, students and engineers devoting their work to comuting and experimental mechanics in different areas of engineering applications on a common platform.
The conference key topics were following:
Testing of buildings materials at the nano, micro, mezzo and macro levels.
Destructive and non-destructive methods for determining the mechanical properties of building materials.
Relationships between material parameters.
Computational and experimental dynamics and mechanics.
Material research for steel, buildings materials, glass, woods, textiles, and composites.
Analyses of constructions.
Computational methods for analyses of constructions and materials.
Scientific comittee:Tomáš PlachýPavel TesárekPavel PadevětPetr BittnarAleš JíraJan VorelBořek PatzákMichal Šejnoha
Local organizing comittee:Petr BittnarTomáš PlachýPavel PadevětPavel TesárekOndřej ZobalZdeněk Prošek
Guarantor of the peer review process:Pavel Padevět
Guarantor of the language editing:Tomáš Plach
Optimising truss-based metamaterials for unimodal and pentamodal behaviour
Full text linkOur study focuses on the optimisation of the internal structure of unimodal and pentamodal metamaterials, modelled as three-dimensional linear elastic lattice structures. For optimisation, we represent the metamaterials with discrete truss models of their respective Periodic Unit Cells (PUCs), whose effective response is determined by the first-order numerical homogenisation. The optimisation is formulated as an inverse homogenisation problem with objective functions comprising a ratio of selected eigenvalues of the effective stiffness matrix, which allows us to dispense with the traditional volume constraint and solve the optimisation problem with a simple gradient method combined with the line search method. We demonstrate the efficacy of the formulation with a design of a unimodal material compliant in a chosen shear deformation mode and we also show that our formulation recovers the traditional pentamodal metafluid
Fire resistance of high-performance concrete reinforced with selected fibers
Full text linkOne of the biggest issues of high-performance concrete is its behavior during fire. Because of the much lower amount of pores in high-performance concrete, extremely high water vapor pressure is created. This leads to explosive spalling of the concrete. One way to prevent this effect is by adding fibers to the concrete mixture. In this article, the impact of commonly used polypropylene fibers is compared to that of flax fibers and viscose fibers. Subsequently, mechanical compressive and flexural strength were tested on those samples that remained intact after the fire experiment. Their mechanical properties were compared with the reference samples without exposure to fire at the same age
Šimáně 2025 – International Student Conference on Nuclear Engineering
No full textNuclear-related sciences and technology have a long and rich history within the Czechoslovakia. Even though the Czech Republic and Slovakia have been separated since 1993, wide cooperation on different levels including education and research still exists. In order to support cooperation and good relations between Czech and Slovak students in nuclear engineering and related disciplines, the Department of Nuclear Reactors organizes annually a student conference on nuclear engineering - Šimáně. Students mainly from Czech and Slovakian nuclear institutes are invited to present their research and share their knowledge. Participants from other foreign institutes are welcomed as well.
The conference is named after professor Šimáně, who graduated at the Dr. Edvard Beneš Technical University in Brno. During his early career, he had the opportunity to work with Fréderic Joliot-Curie at College de France. Later, he significantly contributed to the foundation of the nuclear science, industry and education in the Czechoslovakia. He became the first employee of the Institute of Nuclear Physics at the Czechoslovakian Academy of Science, later he became the first director of the Nuclear Research Institute in Řež. Professor Šimáně was well established even on the international level. He was a director at the Joint Institute of Nuclear Research in Dubna or a division director at the International Agency for Atomic Energy. His work was also significantly connected with Faculty of Nuclear Sciences, CTU in Prague where he acted as Dean from 1967 to 1972.
The main objective of the conference is to provide an opportunity for BSc., MSc. and Ph.D. students of nuclear-oriented study programmes to publish and present their scientific results achieved during their university studies. Furthermore, it should give the participants experience in the field of presenting their own research, writing scientific papers and also broaden their knowledge throughout the related fields and to remind them rich Czechoslovakian history in nuclear fields by inviting experienced experts.
The organizing committee would like to thank all participants for their contributions and also to the CTU in Prague for funding this student conference. The committee also hopes that the work achieved and presented will fulfill the heritage of professor Čestmír Šimáně in current as well as future conferences.
Date: June 17 - 18, 2025Venue: Prague, Czech RepublicURL: https://lenochod.fjfi.cvut.cz/simane/
Organized by:Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering
Guest editor:Milan ŠtefánikMartin CesnekPavel SukMartin Ševeček
Scientific committee:Milan ŠtefánikMartin CesnekPavel SukMartin Ševeček
Local organizing committee:Martin ŠevečekPavel SukŠtěpán JedlanJakub MátlOndřej LachoutJosef Sabol
Guarantor of the peer review process: Milan Štefánik
Guarantor of language editing: Martin Cesne
Numerical simulation of secondary heat exchanger in S-Allegro
Full text linkThis paper presents a computational analysis of the Secondary Heat Exchanger (SHX) in the S-Allegro experimental facility. The S-Allegro facility is a helium circuit which serves as an experimental platform for validating thermohydraulic calculations of helium flow in support of Gascooled Fast Reactor (GFR) development. A computational analysis performed on the SHX included calculations using criterial equations of heat transfer and, most importantly, numerical simulation. Both methods were compared to experimental data and adjusted to achieve a good agreement. The results of the numerical simulations are used to analyse flows in the heat exchanger and identify potential improvements in future design of heat exchangers for GFR. The study provides insights into the thermal performance of helium-water heat exchangers and contributes to the validation of computational methods for GFR technology development
Experimental study on mechanical properties, failure, and dilatacy behaviour of high and ultra high strenth concrete under triaxial compressive stress
Full text linkTo study the mechanical properties of high- and ultra-high-strength concrete, the conventional triaxial tests were carried out on four types of concrete with different strengths under six levels of confining pressure. The influence on the failure mode, strength, deformability, and dilation properties of four kinds of concrete with different strengths by the confining pressure was studied. The test results show that: the cracks generated in high strength concrete always bypassed the coarse aggregate, while in ultra-high-strength concrete, the cracks mainly passed through the coarse aggregate. With increasing confining pressure, the peak stress and stress of dilatancy onset of four types of concrete increase, and the corresponding strain at peak stress and dilatancy onset mount approximately linearly. The enhancement of the confining pressure on the peak stress, stress of dilatancy onset, strain at the peak stress and dilatancy onset in a negative relation to the uniaxial compressive strength of concrete. The peak volumetric strain of concrete increases as the confining pressure mounts. Under the same condition of confining pressure, the lower the uniaxial compressive strength is, the higher the volumetric strain is. The parameters were modified to make the volumetric model more suitable to describe the change law of volume for high- and ultra-high-strength concrete with a wider range of confining pressure levels. The failure envelopes of four kinds of concrete under uniaxial and triaxial stress states were obtained by using the nonlinear Mohr-Coulomb criterion.
Received: 26.09.2024
Received in revised form: 11.04.2025
Accepted: 24.11.202