Ústav nosných konstrukcí

prof. Dr. Ing. Martin Pospíšil, Ph.D.

15122 Ústav nosných konstrukcí

Publikace přináší ucelený pohled na historii i současnost pražských nýtovaných mostů a lávek, z nichž některé, jako železniční most pod Vyšehradem nebo Čechův most, neoddělitelně patří k panoramatu hlavního města. Autory jsou vyučující z ČVUT v Praze, kteří se dané problematice dlouhodobě věnují. U každého z mostů a lávek – kromě výše uvedených jsou to ještě mosty Bohdalec a na Císařskou louku a lávky přes Smíchovské nádraží, přes nádraží Hostivař, Slavie a Strašnice – najdete zpracovanou historii od vzniku přes opravy až po současný stav, původní statické výpočty a bohatý obrazový doprovod archivní i současný. Publikace je primárně určena odborné veřejnosti a poučeným čtenářům technického zaměření.

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RNDr. Dana Kolářová

15122 Ústav nosných konstrukcí

Different methods of geometric transformations of spatial objects and development of geometric abstraction are still an integral part in architectural design processes. New technologies bring new possibilities. The aim of this paper is to introduce an educational project (realized at the Faculty of Architecture of the Czech Technical University in Prague) focused on the combination of the well-known classical methods of relief perspective with the modern technologies of 3D printing.

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Ing. Veronika Steinerová

15122 Ústav nosných konstrukcí

Several prestressing reinforced structures have recently collapsed due to chloride-induced steel corrosion. This study investigates the effect of the corrosion of hot-dip galvanized conventional prestressing steel reinforcement under hydrogen evolution on bond strength in normal-strength concrete. The impact of hydrogen evolution on the porosity of cement paste at the interfacial transition zone (ITZ) is verified through image analysis. The whole surface of prestressing strands is hot-dip galvanized, and their corrosion behavior when embedded in the cement paste is investigated by measuring the time dependence of the open-circuit potential. Concerning the uniformity of the hot-dip galvanized coating and its composition, it is advisable to coat the individual wires of the prestressing reinforcement and subsequently form a strand. It is demonstrated that the corrosion of the coating under the evolution of hydrogen in the cement paste reduces the bond strength of hot-dip galvanized reinforcement in normal-strength concrete. Image analysis after 28 days of cement paste aging indicates insignificant filling of hydrogen-generated pores by zinc corrosion products. Applying an additional surface treatment (topcoat) stable in an alkaline environment is necessary to avoid corrosion of the coating under hydrogen evolution and limit the risk of bond strength reduction.

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Ing. Veronika Steinerová

15122 Ústav nosných konstrukcí

In this study, the nature of boriding surface treatment mechanism of the steel prestressing strand is evaluated and then the corrosion resistance of the borided steel in hydrochloric acid is assessed (detection of the content of released iron and manganese in the exposure solution). The effect on the bond strength of the treated steel prestressing strand with normal strength concrete is also evaluated (pull-out test). Boriding was carried out in a boron carbide backfill with fluoride activators. This manuscript describes the first informative results on this topic.

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Ing. Veronika Steinerová

15122 Ústav nosných konstrukcí

Corrosion damage to conventional prestressing reinforcement placed in a grout channel stimulated with chloride anions can lead to unpredictable collapse of reinforced concrete structures. An expert report previously carried out on the condition of the Troja footbridge after its collapse indicated that corrosion of the prestressing reinforcement stimulated by chloride anions was the cause. In this paper, the possibility of applying corrosion protection in the form of a protective SiC-based plasma coating is studied. The barrier protection properties of the silicon carbide coating partially incongruently decomposed into elemental silicon and amorphous SiO2 were comparatively verified in hydrochloric acid - AAS solution by analyzing the iron content of the test solution after the exposure time. Furthermore, the bond strength of the reinforcement coated in this way with concrete of normal strength was verified by means of a pull-out test. Testing was carried out on standard cubic specimens with standard uncoated and ceramic coated reinforcement applied. Interpretation of the bond strength test results included measurement of changes in surface roughness (Ra) and contact surface angle of the coated ceramic.

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Ing. Veronika Steinerová

15122 Ústav nosných konstrukcí

In this study, the corrosion properties of plasma-sprayed Al2O3 coating (APSS) with a topcoat of zirconium-based conversion coating (ZrCC) and organofunctional silane coating (3-glycidyloxypropyltrimethoxysilane; GPTMS) on carbon steel are investigated in detail. Additionally, the bond strength of plain steel bars coated with this system in normal strength concrete are newly tested. The APSS coating exhibits significant porosity, with unfavourable open pores limiting the barrier protection effect. In contrast, the surface roughness (Ra) significantly increases, improving the bond strength between steel bars and concrete. Such increase in carbon steel roughness improves bond strength in concrete. The synergic application of ZrCC and GPTMS topcoats significantly enhances the corrosion resistance of the base coat (inhibition effect). The character of the GPTMS coating increases the wettability of the APSS coating, which further positively contributes to bond strength between plain bars and concrete. It is demonstrated that when the ZrCC topcoat is applied without GPTMS, the corrosion resistance increases insignificantly and the surface wettability decreases, negatively affecting bond strength in comparison with carbon steel coated using an APSS base coat only.

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Ing. Veronika Steinerová

15122 Ústav nosných konstrukcí

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Ing. Veronika Steinerová

15122 Ústav nosných konstrukcí

This article presents the results of research on the growth kinetics, microstructure (SEM/EDS/XRD), and corrosion behavior of Zn-5Al coatings obtained using a high-temperature hot dip process on B500B reinforcing steel. The corrosion resistance of the coatings was determined using the neutral salt spray (NSS) test (EN ISO 9227). Based on chemical composition tests in micro-areas (EDS) and phase composition tests (XRD), corrosion products formed on the coating surface after exposure to a corrosive environment containing chlorides were identified. In the outer layer of the coating, areas rich in Zn and Al were found, which were solid solutions of Al in Zn (), while the diffusion layer was formed by a layer of Fe(Al,Zn)3 intermetallics. The growth kinetics of the coatings indicate the sequential growth of the diffusion layer, controlled by diffusion in the initial phase of growth, and the formation of a periodic layered structure with a longer immersion time. The NSS test showed an improved corrosion resistance of reinforcing bars with Zn-5Al coatings compared to a conventional hot-dip-galvanized zinc coating. The increase in corrosion resistance was caused by the formation of beneficial corrosion products: layered double hydroxides (LDH) based on Zn2+ and Al3+ cations and Cl- anions and simonkolleite—Zn5(OH)8Cl2H2O.

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prof. Dr. Ing. Martin Pospíšil, Ph.D.

15122 Ústav nosných konstrukcí

Stereotomie se zabývá technikou, jak z daného materiálu vytvářet tělesa a jak je spojovat v projektovaný celek. Historicky vznikla z potřeby přesného rozměření a opracování kamenů pro stavbu konstrukčních objektů (zdí, kleneb, schodišť, mostů), a to v ideálním případě bez použití dalších spojovacích materiálů (malty, kovových spon). Stereotomie se během své existence prolínala i se stavební mechanikou.

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RNDr. Dana Kolářová, RNDr. Stanislava Čečáková

15122 Ústav nosných konstrukcí

This article concentrates on a project that aims to provide students of the Faculty of Architecture CTU with a fresh perspective on the world of geometry surrounding us. Origami tessellations are made from a single piece of paper, which is folded in a repeating pattern with flatly overlapped facets. Their construction combines elements of design with the use of geometry and mathematics. In addition, the topic strengthens knowledge of wallpaper symmetry groups and tessellations in general.

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