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Application of the SiGMA analysis to the stress evaluation of the cracking structures

100%
ŚWIT G., TEODORCZYK M.
Edukacja-Technika-Informatyka
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2014
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vol. 5
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issue 1
676-681
EN
The paper presents the method for the elastic wave processing and propagation analysis applied to the reinforced concrete element under load. The quantitative method gives information about structural changes within the material and enables three-dimensional location of local damage. The Sigma analysis based on a waveform of longitudinal waves was chosen for the study. On this base the analysis can locate the place of the concrete deterioration and evaluate the stress which causing cracking. The acoustic emission test was conducted by the industrial apparatus and six piezoelectric sensors. The waveforms of acoustic emission signals were analysed using computer software. The experimental study confirmed the correctness of the analysis on the base of cracking appearing. The Sigma analysis identified tensile stress, shearing stress and both simultaneously. The method can be useful in the early detection of the micro-cracking of the reinforced concrete elements.
2
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Concrete heritage in the Netherlands. Valuation and conservation of concrete and reinforced concrete structures

72%
de Jonge W.
Architectus
|
2021
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issue 2(66)
39-49
EN
The article deals with reinforced concrete structures in the Netherlands in the interwar period. The aim of the article was to present the changes in the use of reinforced concrete and the introduction of various light concrete products for the construction of light façades structures such as curtain walls. Reinforced concrete, which appeared in Dutch architecture around 1900, causes conservation problems today, which are discussed in the article on the example of the Sint Jobsveem (Jan J. Kanters), the Zonnestraal Sanatorium in Hilversum (Jan Duiker, Bernard Bijvoet and Jan Gerko Wiebenga) and the Van Nelle Factory in Rotterdam (Johannes Brikman, Leendert van der Vlugt and Jan Gerko Wiebenga), involving the author’s own experiences related to renovation works on these buildings. The most serious problem today is the porosity of concrete and the process of its carbonation due to the high level of CO2 caused by air pollution. In the past, the influence of cement alkalinity and its role in protecting reinforcement against corrosion was not well understood. The damaging effects of curing agents such as calcium chlorides were unknown. The focus was mainly on the relationship between the water-cement ratio and the compressive strength. Today, concrete repair methods are usually selected individually, depending on whether we are dealing with exposed or plastered concrete work, and on the size and scale of the damage. The most effective way to protect concrete against carbonation is to use a special waterproof protective coating – offering the highest possible diffusion resistance to carbon, sulfur and chloride ions and the lowest possible diffusion resistance to water vapor. Such a coating protects concrete against the penetration of CO2 and acid ions, and at the same time allows free evaporation of moisture from the concrete to the environment. The described experiences show that even heavily damaged concrete can be restored. It is a matter of cost and the challenge of keeping its original appearance.
PL
Artykuł dotyczy konstrukcji żelbetowych stosowanych w Holandii w okresie międzywojennym. Jego celem było przedstawienie zmian w użyciu żelbetu oraz różnych wyrobów z betonu lekkiego wykorzystywanych do budowy ścian osłonowych. Żelbet, który pojawił się w architekturze holenderskiej około 1900 r., powoduje dziś problemy konserwatorskie, które omówiono w artykule w oparciu o własne doświadczenia autora związane z renowacją następujących budynków: Sint Jobsveem (Jan J. Kanters), Sanatorium Zonnestraal w Hilversum (Jan Duiker, Bernard Bijvoet i Jan Gerko Wiebenga) oraz Fabryki Van Nelle w Rotterdamie (Johannes Brikman, Leendert van der Vlugt i Jan Gerko Wiebenga). Najpoważniejszym problemem jest dziś porowatość betonu i proces jego karbonatyzacji ze względu na wysoki poziom CO2 spowodowany zanieczyszczeniem powietrza. W przeszłości wpływ zasadowości cementu na ochronę zbrojenia przed korozją nie był dobrze rozumiany. Szkodliwe działanie środków utwardzających, takich jak chlorki wapnia, nie było znane. Skupiono się głównie na relacji między stosunkiem wodno-cementowym a wytrzymałością na ściskanie. Dziś metody naprawy betonu dobierane są zazwyczaj indywidualnie, w zależności od tego, czy mamy do czynienia z betonem odsłoniętym czy pokrytym tynkiem, a także od wielkości i skali uszkodzeń. Najskuteczniejszym sposobem ochrony betonu przed karbonatyzacją jest zastosowanie specjalnej wodoodpornej powłoki ochronnej – umożliwiającej najwyższą możliwą odporność na wnikanie jonów węgla, siarki i chlorków oraz przepuszczającej parę wodną na zewnątrz. Taka powłoka zabezpiecza beton przed wnikaniem jonów CO2 i kwasów, a jednocześnie umożliwia swobodne odparowanie wilgoci z betonu do otoczenia. Opisane doświadczenia pokazują, że nawet bardzo zniszczony beton można odtworzyć. To kwestia kosztów i umiejętności zachowania oryginalnego wyglądu.
3
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Analysis of the impact of high temperature on the change in tensile strength of cement mortars with or without polypropylene fibres added

72%
Drzymala T., Reszka M.
Scientific Journal of the Military University of Land Forces
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2018
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vol. 50
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issue 3(189)
109-126
EN
When evaluating concrete, its strength is the most important feature from the practical point of view. In compliance with technological requirements, the strength of concrete depends primarily on its composition, mainly on the content and strength of cement slurry. This is because this concrete component is most susceptible to changes in working conditions in a construction, including high temperature impact on concrete during the fire. The paper presents the results of tests performed on the cement mortar with and without the addition of polypropylene fibers. This treatment allowed for the elimination of the effect of the coarse aggregate by reason of the accuracy of the tested strength characteristics. The studies concerned the impact of high temperature on the change in tensile strength of cement mortars modified with the addition of polypropylene fibers. The analysis of available literature shows that one of the main causes of concrete’s thermal spalling is seen in high tensile stresses. The results of many tests prove that the addition of polypropylene fibers can have a positive effect on the behavior of concrete structures at high temperatures and help reduce spalling. The polypropylene fibers present in a composite may also positively influence the increase in tensile strength. This article discusses the purpose and scope of research, research methods, the experiment plan, test benches, and test results as well. The conclusions of the study were formulated in the final part of the article.
4

Pierwsze w Królestwie Polskim łukowe mosty systemu Moniera zbudowane przez inżyniera Arnolda Bronikowskiego

58%
Mistewicz M.
Kwartalnik Historii Nauki i Techniki
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2019
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vol. 64
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issue 1
39–55
EN
The article lists the first applications of the Joseph Monier patent for the construction of reinforced concrete bridges that took place on the Polish lands. The history of the construction of Monier reinforced concrete arch bridges by Biuro Techniczne Arnold Bronikowski & S-ka Inżynierowie in the Kingdom of Poland was described on the basis of written sources, iconography, literature and current records. In particular, these included the bridge on the pond in the Ujazdów Park in Warsaw, the Reformacki Bridge on the Rypinowski Canal in Kalisz, the bridge over the Czechówka River in Lublin and the viaduct along the Karowa Street in Warsaw. The basic technical parameters of these constructions, dates of implementation and current status were specified. The life and professional achievements of engineer Arnold Bronikowski were presented in the context of his constructions, both beautiful and innovative at the time. Three of the engineering objects described in the article survived the ravages of war and remain in use today.
5

Inżynier Kajetan Mościcki (1855–1933) i jego działalność na rzecz budowy ulic i mostów Warszawy

58%
Mistewicz M.
Kwartalnik Historii Nauki i Techniki
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2020
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vol. 65
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issue 1
9–36
EN
The article presents the problems of building and maintaining urban transport infrastructure in Warsaw at the turn of the 20th century. The text concerns Kajetan Mościcki (1855–1933), engineer, who was appointed by the acting Mayor of Warsaw, General Sokrates Starynkiewicz, to the position of senior city engineer and head of the municipal construction department, where he worked from 1889 to 1909. During this period, he paved the streets which were worn or damaged by sewerage works with wooden blocks and covered the sidewalks with concrete slabs. He designed the first slip road in the Kingdom of Poland in the form of a spiral, and he also participated in the construction of the oldest road engineering structures made of reinforced concrete, located in Ujazdowski Park and on Karowa street in Warsaw, the first Warsaw power plant and the second city bridge across the Vistula. In addition to his professional activity, Kajetan Mościcki was an inventor in the fields of mechanics and electrical engineering. At the end of his life, he founded an award that the Polish Academy of Arts and Sciences was to grant to Polish scientists for outstanding achievements.
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