Wyniki wyszukiwania - BazTech

1

Coda wave interferometry for monitoring the fracture process of concrete beams under bending test

Knak Magdalena, Wojtczak Erwin, Rucka Magdalena

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 3

art. no. e144118

EN

Early detection of damage is necessary for the safe and reliable use of civil engineering structures made of concrete. Recently, the identification of micro-cracks in concrete has become an area of growing interest, especially when it comes to using wave-based techniques. In this paper, a non-destructive testing approach for the characterization of the fracture process was presented. Experimental tests were performed on concrete beams subjected to mechanical degradation in a 3-point bending test. Ultrasonic waves were registered on a specimen surface by piezoelectric transducers located at several points. Then, the signals were processed taking advantage of wave scattering due to micro-crack disturbances. For early-stage damage detection, coda wave interferometry was used. The novelty of the work concerns the application of the complex decorrelation matrix and the moving reference trace approach for better distinguishment of sensors located in different parts of a crack zone. To enhance coda wave-based damage identification results, optical imaging of crack development was performed by means of digital image correlation measurement. The results obtained showed that the coda wave interferometry technique can be successfully used as a quantitative measure of changes in the structure of concrete. The results also indicated that the course of decorrelation coefficient curves enabled the identification of three stages during degradation, and it depended on the location of acquisition points versus the crack zone.

2

Finite Element Modeling of Self-Compacting Concrete Beams Under Shear

Hosseinimehrab lham, Sadeghi Abbasali, Noroozinejad Farsangi Ehsan

Civil and Environmental Engineering Reports

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2021

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Vol. 31, no. 4

1--16

EN

Development of self-compacting concrete (SCC) is a very desirable achievement in the reinforced concrete (RC) structures for overcoming issues associated with many problems such as congestions of steel reinforcement. This non-vibrating concrete is not affected by the skill of workers, and the shape and amount of reinforcing bar arrangement of a structure. Due to the high fluidity and resisting power of reinforcing of SCC, it can be pumped longer distances. In this study, the finite element (FE) modeling of three SCC beams in shear while taking into account, the flexural tensile strength of concrete is computed and the results are compared with the available experimental tested reinforced SCC beams. The stirrups are located at 75 mm apart from the end of beams up to the loading point. The electrical strain gauges (ESGs) have been embedded on the stirrups and their strain readings are taken for every step of load increment. For modeling longitudinal steel reinforcing bars and concrete, the 3-D elements with 2-node and 8-node, are used respectively. The comparison of results obtained by two methods is indicated that a good satisfactory agreement is achieved.

3

Flexural performance of concrete beams reinforced with steel-FRP composite bars

Ge Wenjie, Wang Yanming, Ashour Ashraf, Lu Weigang, Cao Dafu

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 2

380--396

EN

Flexural performance of concrete beams reinforced with steel–FRP composite bar (SFCB) was investigated in this paper. Eight concrete beams reinforced with different bar types, namely one specimen reinforced with steel bars, one with fiber-reinforced polymer (FRP) bars and four with SFCBs, while the last two with hybrid FRP/steel bars, were tested to failure. Test results showed that SFCB/hybrid reinforced specimens exhibited improved stiffness, reduced crack width and larger bending capacity compared with FRP-reinforced specimen. According to compatibility of strains, materials’ constitutive relationships and equilibrium of forces, two balanced situations, three different failure modes and balanced reinforcement ratios as well as analytical technique for predicting the whole loading process are developed. Simplified formulas for effective moment of inertia and crack width are also proposed. The predicted results are closely correlated with the test results, confirming the validity of the proposed formulas for practical use.

4

Wyniki doświadczeń nad efektem skali w belkach betonowych ze zbrojeniem bazaltowym

Korol E., Ostaszewska M., Suchorzewski J., Tejchman J.

Inżynieria i Budownictwo

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2016

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R. 72, nr 1

44--47

PL

Przedstawiono wyniki doświadczeń dotyczących efektu skali podczas trzypunktowego zginania belek geometrycznie podobnych. Wyniki porównano z wynikami normowymi. Podkreślono wady i zalety zbrojenia bazaltowego.

EN

The results from experimental investigation of size effect in geometrically similar concrete beams reinforced with BFRP (Basalts Fiber Reinforced Polymer) bars subjected to 3-point bending are presented. Experimental results are compared with theoretical results evaluated based on design codes. Advantages and disadvantages of BFRP bars are emphasized.

5

Relationship M(k) on the basis of research on beams subjected to changing loads

Ślusarczyk J.

Structure and Environment

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2009

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Vol. 1, no. 1

22-34

EN

While calculating reinforced concrete constructions the relationship momentum - curvature M(κ) has significant importance. In exploitation conditions reinforced concrete construction is subjected to increasing loading and unloading. In bent moments, performing even a few cycles of static loading and unloading causes increase in temporary deflection. Building a unified model of relationship M(κ) describing the whole range from the elastic state to the full plasticisation, allowing for variable reversible loads (hysteresis loop) requires further investigations. Degradation of cross section stiffness is the result of damage process and plasticisation. Unified description of processes taking place in reinforced concrete beam cross section can be obtained with the use of elastic work probability, plastic work probability and damage relating cross section stiffness.

6

Doświadczalne badania belek żelbetowych poddanych skręcaniu

Pawlak W.

Zeszyty Naukowe. Budownictwo / Politechnika Śląska

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2007

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z. 112

209-216

EN

The paper presents results of experimental testing of rectangular (BP-T) and L-shaped (BK-T) beams subjected to pure torsion. The studies were conducted in the Laboratory of Institute of Building Engineering Wrocław University of Technology. The experiment had shown that L-shaped element cracked under slightly lower load than the rectangular beam. L-shaped element has bigger strength and rigidity while subjected to torsion in later stages of loading.

7

Experimental investigations of strain localization in concrete using Digital Image Correlation (DIC) technique

Kozicki J., Tejchman J.

Archives of Hydro-Engineering and Environmental Mechanics

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2007

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Vol. 54, nr 1

3-24

EN

The paper presents results of experimental investigations of strain localization in concrete using a non-destructive method called Digital Image Correlation (DIC) technique. This technique measures surface displacements from digital images. The model tests were carried out with notched concrete specimens under three-point bending. Three different beam sizes and two different concrete mixes were used. During experiments, load--deflection curves and evolution of fracture process zone were determined. The measured size effect in strength was compared with the deterministic size effect law by Bazant (1984) and experimental results by Le Bellégo et al (2003).

8

Initial distortions in supports of continuous beams as an alternative to the plastic redistribution of moments

Garstecki A., Ścigałło J.

Archives of Civil Engineering

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2006

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Vol. 52, nr 2

249-261

EN

In the present paper it is assumed that initial distortions are introduced in the form of rotational clearances within the beam at the cross sections at the supports or in the form of gaps between the beam and the supports. Properly scaled distortions can result in the redistribution of bending moment similar to the plastic redistribution. The redistribution induced by initial distortions is not limited by the plastic rotational capacity. In the paper the method is discussed for both, linear and nonlinear moment-curvature relations. Numerical examples of continuous RC beams illustrate the theory.

PL

W pracy przyjęto, że wstępne dystorsje są wprowadzane w formie luzów obrotowych nad podporami lub w formie luzów pionowych. Temu drugiemu typowi luzów może towarzyszyć wstępne wzniesienie formy betonowania. Odpowiednio dobrane wartości dystorsji wstępnych prowadzą do podobnej redystrybucji momentów jaką obserwuje się po powstaniu przegubów plastycznych. Zaletą proponowanej metody jest to, że redystrybucja momentów wywołana przez wstępne dystorsje nie podlega ograniczeniom wynikającym z dopuszczalnego obrotu w przegubie plastycznym. Nie ma też potrzeby badania przystosowania się konstrukcji przy obciążeniach powtarzalnych. W ogólnym sformułowaniu problemu dystorsje uwzględniono w formie więzów jednostronnych. Prowadzi to do zadania programowania nieliniowego. Problem upraszcza się, jeśli przyjmie się założenie, że luzy zamkną się pod obciążeniem stałym i pozostaną zamknięte przy kombinacjach obciążeń. Tę klasę zadań zilustrowano przykładami belek dwu- i czteroprzęsłowych. Zadania rozwiązano dla liniowej i nieliniowej zależności moment-krzywizna z uwzględnieniem wpływów reologicznych. Przykłady ilustrują zastosowanie różnych metod analizy statycznej i różnice wynikające z tych metod.