Ústav betonových a zděných konstrukcí
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- ItemThe effect of the bent of FRP rebar on its short-term mechanical properties(IOP Publishing, 2023-08-25) Lagiň, Juraj; Prokeš, Jan; Girgle, František; Kostiha, Vojtěch; Vašátko, David; Bezděk, Ondřej; Sedláček, Ondřej; Štěpánek, PetrIn the construction industry, FRP (fibre-reinfoced-polymer) reinforcement is used mainly because of its high resistance to aggressive environments. The production and design of straight FRP rebars are now very well understood and described. However, when designing concrete elements, it is usually necessary to adapt the reinforcement to the structure shape and to use bent rebars. However, during the production process, unfavourable changes in the fibre distribution across the cross-section may occur at the bent section. It has a significant effect on the short and long-term properties of the rebar. The paper addresses the highly topical issue of the composition, manufacturing and testing of shaped composite rebar. Consequently, the article presents experimentally determined values of mechanical characteristics obtained from the performed tests.
- ItemDetermination of temperature gradient of slender structure(IOP Publishing, 2021-12-21) Velešík, Marek; Požár, Michal; Nečas, RadimThis study investigates convenient methods of determination of temperature gradient of slender structures in time. Correct determination of temperature along the height of the cross-section takes a key role in defining the temperature loading of slender bridge structures. A proper definition of temperature loading is crucial for structures such as stress ribbon because of their sensitivity to temperature change in terms of geometrical changes of the structure. Correct determination of the temperature gradient is important during long-term geodetic monitoring, which might be used to prove the correctness of computational models of bridge structures. To approximate heat transfer in cross-section, a test specimen with temperature sensors installed along the height was formed and continuously monitored. The accuracy of the retrofitted temperature sensors was also investigated. The temperature at the surface of the specimen, solar radiation and wind velocity were used as input data for heat transfer analysis. The measured values from sensors situated along the height were subsequently used for verification of performed heat transfer analysis on volume computational model in the software Ansys Mechanical.
- ItemAnchorage length of patented wire cables in prestressed bridge girders(Sciendo, 2021-12-30) Svoboda, Adam; Klusáček, Ladislav; Nečas, Radim; Koláček, Jan; Strnad, Jiří; Olšák, MartinThis paper briefly describes the methodology, performance and the obtained results of unique experiments performed on original I-73 precast bridge girders. The main objective of the experiments was to determine the actual anchorage length of corroded-through fully grouted prestressing reinforcement (prestressing wires), which is important for determination of the residual load-bearing capacity of prestressed structures. Observation probes leading all the way to the prestressing wires were drilled on selected sections of the girders along the length of the prestressing reinforcement. Optical image acquisition devices were then installed at these probes. Subsequently, controlled breakage of the patented wires (corrosion failure simulation) and observation of the changes that occurred in the prestressing wires after relief of stress were carried out. Evaluation of the experiments was then performed by analyzing the images obtained before and after the prestressing reinforcement failure.
- ItemProbability-Based Design and Life Cycle Assessment of a Spun Concrete Pole(Atlantis Press, 2015-12-15) Štěpánek, Petr; Laníková, Ivana; Šimůnek, PetrThis contribution compares concrete structure design results obtained via the partial reliability factor method and using a probability-based method. The Monte Carlo simulation method, modified by the Latin Hypercube Sampling method, was used to calculate the reliability of a designed structure. Economic and ecological aspects (acquisition costs, CO2 and SO2 emissions and embodied energy associated with the concrete member through the production, utilization and demolition stages of its life cycle) were taken into account when assessing the quality of the design. An example of a designed structure – a prestressed spun concrete pole manufactured from reinforced concrete – is presented.
- ItemDevelopment of Variants of High-Performance Self-Compacting Concrete with Improved Resistance to the Attack of Sulfates(MDPI, 2021-06-26) Terzijski, Ivailo; Kocáb, Dalibor; Štěpánek, Petr; Strnad, Jiří; Girgle, František; Šimůnek, PetrThis paper presents experimental and analytical work of which the main objective was to support the introduction of a new technology for the production of sewer pipes. In this technology, the pipes produced consist of two differently produced parts. The direct part uses conventional vibro press compacted concrete. In the curved part, on the other hand, self-compacting concrete technology is used. The cooperating company, Prefa Brno a.s., defined possible negative effects on concrete of sewer pipes. The task of the research team and now the author’s team was to propose a procedure for the development of suitable self-compacting concrete variants and subsequently the design of a methodology to verify their durability in aqueous environments containing sulfates. To increase the efficiency of the development, the model mortar method was used in the experimental work. That is, instead of the original concrete, a model mortar derived from it was tested. The principle and procedure of derivation of model mortars are described in the paper. In total, eight variants of model mortars were tested, and at least three of them fulfilled the requirements. An optional but beneficial part of the carried out work was the derivation and practical application of the time-anchored-triangles-of-cracking graphical method developed during the research. This method is used to quickly compare the degree of attack of different silicate composites tested in a common bath inducing type III corrosion.