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PL
Artykuł prezentuje badania przyczepności przeprowadzone przy użyciu testu pull-out. Eksperymenty miały na celu ocenę wpływu długości zakotwienia na przyczepność w tym teście. Z przeprowadzonej analizy wynika, że długość styku pręt-beton znacząco wpływa na zachowanie przyczepności. Określa ona typ zniszczenia połączenia, wpływa na rozkład i wartość naprężeń w pręcie oraz rzutuje na przebieg krzywej przyczepność-poślizg, która jest kluczowym rezultatem testu pull-out.
EN
The article presents bond tests performed using the pull-out method. The experiments were designed to evaluate the effect of anchorage length on the bond in this test. The analysis shows that the length of the bar-concrete interface significantly influences the bond behavior. It determines the type of bond failure, affects the distribution and value of stresses in the bar, and projects the bond-slip curve, which is a key result of the pull-out test.
EN
The study of interfacial behaviour between ribbed steel rebars and concrete is a subject that has been widely studied. However, the definition of the bond stress distribution throughout the embedded length of the steel rebar is still controversial due to the difficulty of experimentally obtaining such distribution for a fixed load magnitude. It is also undeniable its relevancy for the better understanding and model reinforced concrete (RC) structures. So, the definition of the local behaviour between the ribbed steel rebar and concrete is critical to correctly simulate the adherence between both materials. In this matter, the local bond-slip models recommended in codes seem to satisfy some researchers while others suggest prudence in using them. Therefore, only choosing the correct bond-slip relationship may lead to exact interpretations and conclusions of the structural behaviour of a concrete structure but with the existing different bond-slip types, researchers can be misled inadvertently. This work aims to clarify some of these aspects by numerically simulating several pull-out tests under different conditions and checking their influence (or not) on real-scale specimens. After the validation of the numerical model through a proposed new bond-slip relationship, other parameters were studied also. Although the type of the bond-slip relationship influences the detachment of the steel rebar from the concrete, the yielding of the former material was found to be the main parameter that masks the differences in the behaviour of real-scale RC structures when different types of bond-slip relationships were considered in the numerical simulations.
EN
The article presents an original proposal to improve the efficiency of anchoring steel fibers in fibroconcrete mixtures. The expected effect was obtained by developing the surface of the fibers by mechanical abrasive treatment with electrocorundum. The main part of the work presents the results of the conducted experimental studies. The effect of the surface treatment of the fibers was investigated through metallographic techniques, using a metallographic microscope and equipment to determine the surface roughness. On the other hand, the direct method of assessing the effectiveness of fiber anchoring in the concrete was determined using the pull-out test. The results of these studies were subjected to detailed analysis and statistical processing. The results of metallographic and pull-out tests indicate that the proposed method of treating the fibers significantly affects their anchoring efficiency in the concrete matrix. According to the author, this may be of great practical importance because the discussed method of treating the fibers can significantly improve the general properties of fibrocomposite mixtures.
PL
Współpracę betonu ze stalą zbrojeniową zapewnia zjawisko przyczepności. Jest to wzajemne przekazywanie sił pomiędzy prętami zbrojeniowymi a betonem. Znajomość tego zjawiska pozwala na precyzyjne określenie rozkładu odkształceń stali i betonu, a tym samym na określenie przebiegu odkształceń i zarysowania konstrukcji żelbetowej. W artykule zaprezentowane zostały wyniki badań doświadczalnych przyczepności pomiędzy betonami wysokiej wytrzymałości C60/75 i C70/85 a prętami o średnicy 18 mm ze stali wysokiej wytrzymałości SAS 670/800. Dla porównania wykonano również badania przyczepności tych betonów do prętów ze zwykłej stali EPSTAL B500SP.
EN
The interaction of concrete with reinforcing steel is ensured by the phenomenon of adhesion. It is mutual transfer of forces between rebar and concrete. Knowledge of this phenomenon allows you to precisely determine the deformation distribution of steel and concrete and thus on determination of the course of deformation and cracking of a reinforced concrete structure. In this article the results of experimental tests of adhesion between concretes are presented high strength C60/75 and C70/85 and steel bars with a diameter of 18 mm and high the strength of SAS 670/800. For comparison, adhesion tests were also carried out concrete to bars made of ordinary steel EPSTAL B500SP.
PL
Artykuł dotyczy analizy przyczepności żebrowanego stalowego pręta zbrojeniowego w betonie. Celem pracy była ocena wpływu położenia pręta w betonowym bloku na lokalną zależność naprężenie przyczepności-poślizg. Podjęto także próbę numerycznej symulacji przeprowadzonych eksperymentów w programie ABAQUS. Analizę doświadczalną przeprowadzono za pomocą testu pull-out na dwóch rodzajach próbek - centrycznych i mimośrodowych w dwóch wariantach, z dolnym otuleniem o grubości 20 i 40 mm. Do obliczeń numerycznych wykorzystano modele materiałowe odpowiadające materiałom zastosowanym w doświadczeniach. Użyto modelu betonu plastycznego ze zniszczeniem (ang. Concrete Damaged Plasticity) oraz modelu liniowo-sprężystego dla stali. Przeprowadzone eksperymenty potwierdziły, że zmiana lokalizacji pręta na kierunku pionowym wpływa na zmniejszenie jego skrępowania w betonie, co rzutuje na redukcję wartości maksymalnych naprężeń przyczepności oraz na mechanizm zniszczenia, czego konsekwencją jest zmiana przebiegu krzywej naprężenie przyczepności-poślizg względem próbek centrycznych. Wykonane symulacje MES poprawnie odwzorowują zachowanie przyczepności w próbkach podczas testów pull-out.
EN
This paper deals with the bond analysis of a ribbed steel rebar in concrete. The aim of the paper was to evaluate the effect of the bar position in a concrete block on the local bond stress-slip relationship. An attempt was also made to numerically simulate the conducted experiments in ABAQUS software. The experimental analysis was carried out using pull-out test on two types of specimens - centric and eccentric in two variants, with bottom concrete cover of 20 and 40 mm thickness. Material models corresponding to the materials used in the experiments were used for numerical calculations. Concrete Damaged Plasticity model and linear elastic model for steel were used. The experiments confirmed that changing the location of the bar in the vertical direction reduces its confinement in the concrete, thus reducing the bond strength and the failure mechanism, resulting in a change in the bond stress-slip curve with respect to the centric specimens. The FEA simulations performed correctly represent the bond behavior in the specimens during pull-out tests.
PL
W artykule podjęto próbę oceny przyczepności stalowych włókien do matrycy cementowej po ich obróbce mechanicznej, która polegała na rozwinięciu powierzchni pobocznicy przez obróbkę ścierną przy użyciu elektrokorundu. W pierwszym etapie badań dokonano oceny powierzchni włókien (przed i po obróbce ściernej) za pomocą technik metalografii. Wykonano, a następnie porównano obrazy powierzchni włókien w skali mikro, jak również określono chropowatość powierzchni włókien. Drugi etap badań dotyczył bezpośredniej oceny przyczepności włókien do matrycy betonowej metodą pull-out.
EN
In the article was attempt to evaluate the adhesion of steel fibers to the concrete matrix after their mechanical treatment. The processing of the fibers consisted of developing on of their surface by an abrasive treatment with the use of electrocorundum. In the first stage of the research, the surface of the fibers was assessed (before and after abrasion treatment) using the selected metallographic techniques. A micro scale images of the fibers surface were made and compared, as well as the surface roughness of the fibers was determined. The second stage of the research concerned the direct evaluation of adhesion using the pull-out test.
7
PL
W artykule zaprezentowano analizę doświadczalną przyczepności, która miała na celu ocenę wpływu średnicy pręta na przyczepność w próbie pull-out. Ponadto zweryfikowano wybrane modele analityczne wyznaczające wytrzymałość przyczepności w stosunku do otrzymanych rezultatów z testów. Z wykonanej analizy wynika, że średnica pręta istotnie wpływa na zachowanie przyczepności. Przytoczone modele w różnym stopniu zbieżności oszacowują wartości otrzymane z zaprezentowanych badań.
EN
This paper presents an experimental analysis of bond to evaluate the effect of bar diameter on bond in pull-out test. In addition, selected analytical models determining bond strengths were verified against the obtained test results. The analysis shows that bar diameter significantly affects bond behavior. The mentioned models estimate the values obtained from the presented tests to varying degrees of convergence.
8
Content available Badania doświadczalne przyczepności
PL
W artykule zostało przedstawione powszechnie znane wśród badaczy zjawiska przyczepności badanie typu pull out. Zostały opisane wybrane próbki wykorzystywane w tych eksperymentach, sposób prowadzenia badań oraz uzyskiwane z nich rezultaty, a także opisano funkcję przyczepności uzyskiwaną na podstawie wspomnianego testu. W artykule została zaprezentowana własna koncepcja badań dotycząca analizy przyczepności, która w przyszłości ma stanowić podstawę do stworzenia modelu numerycznego służącego do symulacji współpracy betonu i stalowych żebrowanych prętów zbrojeniowych w różnych elementach żelbetowych.
EN
The article presents a pull out test commonly known among bond researchers. Selected specimens used in these experiments, the method of testing and the results obtaining from them were described, and the bond function obtained on the basis of the said test was characterized. In addition, the article presents own concept of experimental bond analysis, which in the future will be formed the basis for creating a numerical model for simulating the cooperation of concrete and steel ribbed reinforcing bars in various reinforced concrete elements.
EN
This article deals with the issue of the bond between concrete and reinforcement. The bond is crucial for reinforced concrete elements because it is possible to transfer forces (stresses) from concrete to the reinforcement. Basic information related to the cooperation of concrete and rebars was recalled in the article. Selected issues concerning theoretical and numerical analysis as well as experiments of the bond phenomenon were presented. The article also proposes its own concept of experimental studies on the bond on two types of specimens: so-called short specimen and large specimen that will be subjected to pull-out tests. The described concept is ultimately to form the basis for creating a numerical model, enabling the simulation of bond in various reinforced concrete elements, calibrated based on the results of experimental studies.
PL
Artykuł dotyczy zagadnienia przyczepności między betonem i prętami zbrojeniowymi. Przyczepność ma kluczowe znaczenie dla elementów żelbetowych, ponieważ dzięki niej możliwe jest przeniesienie sił (naprężeń) z betonu na zbrojenie. W artykule przypomniano podstawowe informacje dotyczące współpracy betonu i prętów zbrojeniowych. Przedstawiono wybrane zagadnienia z analizy teoretycznej i numerycznej oraz eksperymentów dotyczących zjawiska przyczepności. W artykule zaproponowano również własną koncepcję badań doświadczalnych przyczepności na dwóch typach próbek: tzw. próbce krótkiej i próbce długiej, które zostaną poddane testom pull-out. Opisana koncepcja ma docelowo stanowić podstawę do stworzenia modelu numerycznego, umożliwiającego symulację przyczepności w różnych elementach żelbetowych, skalibrowanego na podstawie wyników z badań eksperymentalnych.
EN
The development of the nondestructive diagnostic methods is of significant importance in the last decades. A special attention is paid to diagnostics of reinforced concrete structures, which are very popular in the civil engineering field. A possible use of the guided waves in the estimation of the resistance of steel–concrete adhesive connection is studied in the following paper. The relationships relating adhesive connection resistance and wave propagation characteristics (wave velocity and the time of flight) have been derived and experimentally verified during pull-out tests conducted on a number of reinforced concrete beams varying in the debonding area. The pull-out tests were also monitored ultrasonically. On the basis of the results in the form of the time-domain signals, the theoretical load-carrying capacities of the pulled-out bars have been calculated and compared with the exact experimentally determined values. The high agreement of the results obtained proved the correctness of the developed method. Moreover, the signals registered during pull-out tests allowed to observe the changes of the wave velocity induced by the deterioration of the adhesive connection.
11
Content available Analysis of crack propagation in a "pull-out" test
EN
The article describes a computer analysis of the pull-out test used to calculate the force needed to pull out a rock fragment and determine the shape of this broken fragment. The analyzed material is sandstone and porphyry. The analysis included the first approach to using own subroutine in the Simulia Abaqus system, that is, which task is undertaken to accurately determine the crack path of the Finite Element Method model. The work also contains a description of laboratory tests and analytical considerations.
12
Content available remote Comparison between numerical analysis and actual results for a pull-out test
EN
The paper describes a computer analysis of the pull-out test used to determine the force needed to pull out a fragment of rock and the shape of this broken fragment. The analyzed material is sandstone and porphyry. The analysis included a comparison of different methods of propagation of cracks in the Abaqus computer program using the Finite Element Method. The work also contains a description of laboratory tests and analytical considerations.
13
EN
The paper analyses the impact of casting direction of self-compacting concrete (SCC) on its bond quality to steel reinforcing bars. Tests were performed on high performance self-compacting concretes with different amount of silica fume to cement mass. Experiment was carried out on 480 mm height specimens, which allowed determining changes of bond condition along its height. The ribbed reinforcing bars have been placed perpendicularly to the direction of casting. Casting was performed from two points – from the bottom and the top of the form. Research has shown that casting from the bottom of the form improves bond strength and quality.
EN
The bond of concrete to steel reinforcing bars is the basis for the concept of reinforced concrete as a construction material. One of important bond-related issues is the bond strength-bar slip relation, which has an influence on the failure mode and rotation of structural joints. This relation can be predicted by bond–slip models and it depends on the bond behaviour at the reinforcement–concrete interface. However, the currently-known bond-slip models offer limited applications to well-studied normal concretes only. This article proposes local bond–slip relationships for high performance self-compacting con-crete (HPSCC) taking into account the quality of bond conditions. The studies were per-formed on specimens made of four different high performance self-compacting concrete mixes with varying contents of silica fume. Since the specimens had total heights of 480, 800 and 1600 mm, it was possible to measure the changes of the bond at individual levels. The results were next compared to those obtained for samples made of vibrationally-compacted high-performance concrete (HPC). It was demonstrated that the bond-slip model for normal concretes seems to underestimate the bond stiffness and ultimate bond strength for the HPSCC and HPC mixtures. Moreover, it was proven that a change of the quality of bond conditions has an effect on the local bond-slip relationship. Finally, local bond-slip relation-ships were presented separately for HPSCC and HPC with respect to the quality of bond conditions
15
Content available remote Nośność kotew chemicznych w elementach wapienno-piaskowych
PL
W artykule przedstawiono wyniki pomiarów skuteczności montażu kotew chemicznych (wklejanych) osadzonych w drążonych pionowo blokach wapienno-piaskowych. Badania wykonano dla przypadków montażu kotew w różnych fragmentach bloków: w części pełnościennej, w osi symetrii oraz na krawędzi otworu pionowego. Przebadano wpływ lokalizacji miejsc osadzenia kotew na sposób kształtowania się połączenia między żywicą a materiałem bloku. Główny nacisk położono na określenie wpływu lokalizacji montażu na nośność kotew.
EN
The article shows the results of measurements of the performance of bonded anchors (adhesive anchors) set in vertically drilled lime and sand blocks. Testing covered the cases of anchors mounted in various sections of these blocks, namely in the solid wall part, in the symmetry axis, and at the edge of the vertical opening. The effects of anchor setting locations on the formation of resin to block material joints were investigated. The primary focus was put on determination of the impact of the assembly location on the load-carrying capacity of anchors.
EN
Woven spacer fabrics are used as reinforcing materials for fiber-reinforced plastics. These fabrics consist of mostly pliable textile fibers, which still require defined rigidity for different crash applications. In this regard, multi-material woven spacer fabrics present a promising approach. This paper presents the development of multi-material woven spacer fabrics using steel wire and carbon rovings. For the development of such woven spacer fabrics, a systematic structure realization based on the weave pattern was performed. Selected structures were produced on a modified weaving machine.
PL
Tkaniny dystansowe są stosowane jako wzmocnienie kompozytów polimerowych. Tkaniny te składają się głównie giętkich włókien tekstylnych, które wymagają określonej sztywności dla zastosowania przy różnych naprężeniach udarowych. W pracy wytworzono tkaniny dystansowe zawierające druty stalowe i niedoprzęd węglowy. Przygotowano system odpowiednich struktur realizowanych na zmodyfikowanej maszynie tkackiej.
EN
The paper presents the analysis of the impact of silica fume content in high-performance concrete (HPC) on bond conditions along the height of tested elements. The tests were performed on the specimens made of six different HPC mixes with varying content of silica fume (0, 5 and 10% by mass of cement) and superplasticizer. The used specimens allowed for determining the changes of bond at individual levels of elements with a total height of 480 and 960 mm. The rebars in the elements were placed perpendicularly to the direction of concreting. The reference element, characterised by the parallel orientation to the direction of concreting, was also prepared. The tests indicated that the quality of bond conditions in HPC deteriorates as the distance from the formwork bottom increases. The experiment results indicate that concrete modification with silica fume can both increase and decrease the quality of bond conditions. The influence of silica fume depends on the thickness of the concrete cover, which determines the mechanism of bond failure.
EN
Influence of geosynthetics inserted into cohesive granular soil was obviously investigated using geosynthetics-soil-interaction-testing device (ITD). Observations were already made during undertaking pull-out test, and then the results revealed that a correlation between shear stress and normal stress exhibits non-linear behaviour. In this paper, three approaches of trend-lines namely linear, logarithmic, and polynomial were compared. From analysis, polynomial trend line gave the best correlation among others. The final equation is very important part when estimating more accurate values of cohesion and friction angle design purpose.
PL
Alkaliczna aktywacja cementów mieszanych zawierających w swoim składzie żużel wielkopiecowy lub/i popiół lotny jest jedną z metod otrzymywania spoiw specjalnych. Podobnie jak w przypadku betonów tradycyjnych, budowa granicy międzyfazowej pomiędzy stwardniałym zaczynem a kruszywem lub stalą istotnie wpływa na własności otrzymanych z ich zastosowaniem zapraw i betonów. W prezentowanej pracy przedstawiono wyniki mikroskopowych obserwacji i mikroanaliz (SEM, EDS, BSE) strefy kontaktowej stal zbrojeniowa-stwardniały alkalicznie aktywowany zaczyn. Stwierdzono, że w przeciwieństwie do powszechnie przyjętych dla konwencjonalnych betonów modeli w badanej strefie kontaktowej nie zauważono występowania strefy o podwyższonej porowatości ani warstwy krystalicznego portlandytu. Na granicy stal-zaczyn stwierdzono występowanie zbitej mieszaniny faz C-S-H i N-A-S-H, wzbogaconych dodatkowo o jony żelaza, co może świadczyć o chemicznym charakterze tego połączenia. Badania mechaniczne (pull-out test) zdają się potwierdzać powyższą tezę.
EN
Alkaline activation of blended cements containing of slag or/and fly ash is one of the new methods of special binders production. Similarly as in the case of traditional concrete, the interfacial transition zone (ITZ) between cement paste and aggregate or steel strongly influences the mechanical and transport properties of mortar and concrete. This paper presents the results of a mechanical investigation (pull-out test) and microscopic observation of steel-hardened alkali activated cement paste (AAHCP) zone contact. In presented investigation, composite mineral binder consists of: 15% Portland cements CEM I 42, 5, 15% granulated blast furnace slag and 70% fly ash. As alkaline activator, sodium water glass with silicate modulus SiO2/Na2O = 1.5 were used. The two type of samples were prepared, the first for microscopic analyses of ITZ (AAHCP containing commercial steel fibers), and the second (for pull - out test) - concrete cubes (100x100x100) = 6.15 mm, a slight surface) anchorage in matrix. Fwith steel rods ( The steel rods were pulled out from concrete matrix with a displace constants displacement velocity 0.5 mm/min. Backscattered electron images (BSE) obtained by scanning electron microscope and EDS microanalyses were used to characterize the ITZ microstructure. Results obtained for the sodium water glass activated mineral composite binder shows, that in the opposite to steel-portland cement paste system, the zone of increased porosity and crystalline Ca(OH)2 layer was no observed. On the point of contact (steel-AAHCP) the dense mixed phase, C-S-H and N-A-S-H were identified. Also were observed the increase of amounts a Fe ions in described contact zone, especially on the binder hydration products side. It can suggest that connection of steel-AAHCP have a chemical character. The analyzing of stress-strain curves in the pulling out process of steel rods, from a concrete made of alkaline activated binder and compared PC concrete matrix confirms this thesis. In the case where AASC were used, the shear strength of the steel AAHCP bond were about twice more high than in the case of compared portland cement concrete.
EN
The paper presents results of strain measurements in cohesionless sand in two different boundary value problems, namely quasi-static pull-out test of a steel wall and confined granular flow in a rectangular model silo using a non-destructive method called Particle Image Velocimetry (PIV) which is a technique for measuring surface displacements from digital images. Advantages and disadvantages of the method are outlined.
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