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Evaluation program of radar measurement with different polarisation: Sustainable Bridges Background document SB3.5
BAM, Berlin, Germany.
BAM, Berlin, Germany.
2007 (English)Report (Refereed)
Abstract [en]

For the investigation of concrete structures, the main task is to detect and localise inhomogeneities such as untensioned reinforcement bars, tendon ducts, voids, pipes and other constructional elements and to estimate thickness of layered structures, based on the contrast in dielectric properties. Impulse radar has been applied very efficient to solve these problems. The method is based on the propagation of electromagnetic impulses having maximum frequencies between 500 MHz and 2.5 GHz for civil engineering applications. The waves are emitted by an antenna (transmitter), which is moved along the surface. The transmitting impulsesare reflected at interfaces of materials with different dielectric properties and detectedby a second antenna (receiver), also positioned on the surface. In most cases both antennas are close to each other, in the same housing (zero offset). Since radar cannot penetrate to metallic elements, rebars and tendon ducts are perfect reflectors.

The following conclusions could be drawn from these results:

· Detection of reinforcement bars being parallel and perpendicular to antenna movement depends strongly on the positioning of the antenna and the polarisation of the emitted electromagnetic waves. It is always easier to detect rebars which are crossed by the movement of the antenna. The highest intensity of reflection could be achieved if the polarisation is parallel to the rebars.

· Detection of tendon ducts is possible, if the reinforcement grid above has not too small grid sizes (> 5 cm). In other cases, most part of the electromagnetic energy is reflected at the grid. To reduce the intensity of reflections from crossed rebars for a better detection of the tendon ducts, it is useful to select the polarisation perpendicular to the crossed rebars.

· Detection of reinforcements and tendon ducts is possible with the 900 MHz as well as with the 1.5 GHz. With the 1.5 GHz antenna, a better resolution but less penetration depth could be achieved.

Place, publisher, year, edition, pages
2007. , p. 48
Keywords [en]
Concrete Bridges, Radar detection of rebars
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-75302OAI: oai:DiVA.org:ltu-75302DiVA, id: diva2:1337397
Note

EC Sixth Framework Program

Sustainable Bridges – Assessment for Future Traffic Demands and Longer Lives

TIP3-CT-2003-001653

Available from: 2019-07-14 Created: 2019-07-14 Last updated: 2019-08-14

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CiteExportLink to record
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Citation style
  • apa
  • ieee
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  • de-DE
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  • Other locale
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Output format
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