Ústav betonových a zděných konstrukcí

Browse

Now showing 1 - 5 of 19

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.
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.
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.
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.
Experimental model of plan curved footbridge supported by arch
(IOP Publishing, 2020-12-09) Trenz, Jan; Zlatuška, Karel; Nečas, Radim
The new type of plan curved structure with the upper deck has been developed within the research of arch structures. The paper describes the process of the research and the design of the physical model in scale 1:10 built for testing of the structure type. The design of the structure has been based on observation of static and dynamic behaviour of arch structures of various radii of plan curvature. Internal forces, deformations and natural modes were monitored for different methods of the design. At first, a simplified method of designing plan curved structures with arch situated in the bridge axis has been investigated and the behaviour of structures designed in accordance with this method has been studied. It has been discovered that simplified method can be used for design of structures with plan curvature radius of 250 m or higher. After investigation of other design methods, the method based on inversion of suspension cable has been chosen for further development. The method has been improved with processes that allow the application for plan curved structures. The result is a plan curved structure supported by a spatial arch. The geometry of the arch corresponds with ideal thrust line of the arch for given permanent loads. The composite structure with steel arch of span of 60,0 m with radius of plan curvature of 37,5 m has been designed and analysed thoroughly in MIDAS Civil software. The behaviour of the calculation model has been compared with behaviour of physical model in scale 1:10 that has been built in laboratory of the Faculty of Civil Engineering of BUT. Results have demonstrated that calculations and measurements correspond.

Browse

Recent Submissions