Ústav betonových a zděných konstrukcí

Browse

Recent Submissions

Now showing 1 - 5 of 20
  • Thumbnail Image
    Item
    Tuned mass dampers - evaluation of the effecton two real footbridges
    (Ernst & Sohn, 2024-09-11) Nečas, Radim; Kučera, Jiří; Koláček, Jan; Bezručová, Kristína
    Pedestrian comfort, subtle design, minimizing the number of fixed supports of thefootbridge or material saving. These are the key arguments for integrating tunedmass dampers into the bridge project. The goal is to protect people and structurefrom vibrations and damage. The following paper presents findings from the design,production and tuning of mass dampers, their optimization possibilities and benefitsfor bridge engineering. The validity of damper design was verified on two footbridgesin the Czech Republic and Slovakia. It concerns the footbridge over the Svitava Riverin Bílovice nad Svitavou and the footbridge over the high-speed road in Banská Bystrica. Dynamic tests including measurement were carried out on both bridges before and after the installation of the dampers. The dynamic monitoring of thecompliance of modal parameters was conducted using operational modal analysis(OMA). The evaluation of the dynamic tests also includes the response to pedestrianeffects (comfort criteria) and the determination of the logarithmic decrement of thedamping.
  • Thumbnail Image
    Item
    Anchorage length of patented wire cables in prestressed bridge girders
    (Sciendo, 2021-12-30) Svoboda, Adam; Klusáček, Ladislav; Nečas, Radim; Koláček, Jan; Strnad, Jiří; Olšák, Martin
    This 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.
  • Thumbnail Image
    Item
    Strengthening of bridges by post-tensioning using monostrands in substituted cable ducts
    (IOP Publishing, 2017-09-15) Klusáček, Ladislav; Svoboda, Adam
    Post-tensioning is suitable, reliable and durable method of strengthening existing engineering structures, especially bridges. The high efficiency of post-tensioning can be seen in many applications throughout the world. In this paper the method is extended by a structural system of substituted cable ducts, which allows for significantly widening application of prestressing so it’s convenient mostly for application on beam bridges or slab bridges (built in years 1920 – 1960). The method of substituted cable ducts is based on theoretical knowledge and technical procedures, which were made possible through the development in prestressing systems, particularly the development of prestressing tendons (monostrands) and encased anchorages, as well as progress in drilling technology. This technique is highly recommended due to minimization of interventions into the constructions, unseen method of cable arrangement and hence the absence of impact on appearance, which is appreciated not only in case of valuable historical structures but also in general. It is possible to summarise that post-tensioning by monostrands in substituted cable ducts is a highly effective method of strengthening existing bridges in order to increase their load capacities in terms of current traffic load and to extend their service life.
  • Thumbnail Image
    Item
    Long-action of additional horizontal prestressing on masonry
    (Elsevier, 2017-07-20) Pěkník, Robin; Klusáček, Ladislav
    This article is focused on verifying behaviour of a brick masonry which was horizontally post-tensioned. An experimental model of three walls has been built for the measurement. The model is in scale 1:1 and represents a part of a real structure. Longitudinal strain of brick walls has been measured by wire strain gauges in important places. Surrounding temperature and temperature inside the walls were also recorded. Results of the experiment have been continuously evaluated and compared with the simplified numerical models. Right now we have a better picture of actual behaviour of the brick masonry wall which was horizontally prestressed and we are able to design appropriate restoration works for historical buildings.
  • Thumbnail Image
    Item
    Stochastic optimization of reinforced concrete elements’ design
    (IOP Publishing, 2018-07-04) Venclovský, Jakub; Štěpánek, Petr; Laníková, Ivana
    Main goal of the paper is to present an algorithm for stochastic optimization of design of steel-reinforced concrete element’s cross section. Firstly, the deterministic problem is introduced and described, followed by the description of uncertainties involved in the process and stochastic reformulation of the problem. Afterwards, the algorithm itself is introduced. This algorithm is based on internal cycle of deterministic optimization using reduced gradient method and external cycle of stochastic optimization using regression analysis. The probability is assessed on orthogonal grid via modified bisection method. The paper concludes with presentation of the performed calculations and their results.