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2 2023

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Diagnostyka nieniszcząca posadzki w gdańskim Żurawiu z zastosowaniem metody georadarowej

Zielińska Monika, Rucka Magdalena, Wojtczak Erwin, Ciborowski Tomasz, Steffens Michał

Wiadomości Konserwatorskie

2023

Nr 76

129--140

W artykule przedstawiono wyniki badań georadarowych (GPR) przeprowadzonych w gdańskim Żurawiu. Badania wykonano na posadzce najniższej kondygnacji baszt południowej i północnej. Celem eksperymentu jest ocena możliwości wykrycia anomalii znajdujących się pod posadzką. Badania przeprowadzono metodami nieniszczącymi, wykorzystując georadar z antenami o częstotliwości2 GHz oraz 400/900 MHz. W artykule porównano mapy tomograficzne oraz echogramy (B-skany)uzyskane z obu pomiarów. W związku z obecnie trwającymi pracami remontowymi tego obiektu zabytkowego o dużej randze historycznej możliwe było skonfrontowanie otrzymanych wyników z elementami odkrytymi podczas prowadzenia wykopów. W pracy udowodniono efektywność wykorzystania metody GPR do wykrycia w ziemi takich elementów jak belki drewniane, rury, podbudowa kamienna czy właz. Wskazano również wyższość anteny o częstotliwości 2 GHz w przypadku odnalezienia elementów głębiej położonych.

This paper presents the results of a ground penetrating radar (GPR) survey carried out at the Crane in Gdańsk. The measurements were conducted on the floor of the southern and northern towers. The aim of the experiment is to assess the possibility of detecting anomalies beneath the floor. The surveys were carried out in a non-destructive manner, using a georadar unit with 2 GHz and 400/900 MHz antennas. This paper compares the tomographic maps and echograms (B-scans) obtained from both measurements. In view of the on going renovation of this monument of great historical importance, it was possible to compare the results obtained with the elements uncovered during the excavation. The paper proves the effectiveness of using the GPR method to detect elements such as wooden beams, pipes, stone substructures or manholes in the ground. The superiority of the 2 GHz antenna was also demonstrated for the detection of deeper elements.

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

2023

Vol. 71, nr 3

art. no. e144118

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.