Ústav betonových a zděných konstrukcí

Browse

Recent Submissions

Now showing 1 - 5 of 21
  • Thumbnail Image
    Item
    New method for prediction of punching resistance of flat slabs with shear reinforcement and its comparison with recently proposed code provisions
    (Springer Nature, 2025-04-25) Lyčka, Lukáš; Štěpánek, Petr
    The use of flat slabs in constructions is wide-spread due to its many functional and economic advantages. Behavior of flat slabs in shear and flexure is a complex problem and over the last decades several buildings have collapsed due to the failure of the punching shear strength, resulting in loss of lives and financial damages. These disasters revealed gaps in the current (or former) design codes and recommendations. A new method for predicting the punching shear strength of flat slabs with shear reinforcement has been developed. This method incorporates a simple system of struts and ties within the shear crack region while utilizing the current Eurocode 2 model for predicting the punching shear strength without shear reinforcement. The accuracy and safety of predictions of the newly developed method were evaluated against some of the major design codes and standards. Specifically, it was compared with the current Eurocode EN 1992, with the final proposition of the newly proposed Eurocode FprEN 1992, and with the method presented in Model Code 2020. This comparison was carried out using experimental data from load tests on flat slab specimens with shear reinforcement that were published in the scientific literature over the last half of a century. The newly developed method achieved the lowest coefficient of variation among all the compared methods while also obtaining the fewest prediction results that could be deemed unsafe due to overestimation of punching shear resistance.
  • 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.