Electromagnetic testing method using tangential coil for measurement of covering thickness and diameter of rebars in concrete

Koido, Junji; Hoshikawa, Hiroshi
May 2000
AIP Conference Proceedings;2000, Vol. 509 Issue 1, p1723
Conference Proceeding
Reinforcing bar in concrete provide tensile strength of structure. So, a measurement of covering thickness and diameter of rebar is important in maintenance inspection of concrete structure. The electromagnetic testing are expected as the method that can estimate covering thickness and diameter of rebar simultaneously. Magnetic flux generated by an excitation coil must reach a rebar sufficiently, to estimate covering and diameter of rebar. However, conventional test coil systems, which had been previously designed in these works, were insufficient for that requirement. Therefore, a new mutual induction type test coil system was developed for measuring rebars. The system has two tangential excitation windings and they are connected differentially to generate concentrated magnetic flux around rebar. And two pickup coils, that are arranged co-axially and normal to rebar, are also connected differentially to eliminate unbalanced voltage for no existence of rebar. In addition, neural nets were employed to estimate covering and diameter of rebar. Signal from the test coil was given as input for neural nets. From the result of experiment, this new type of coil provides good characteristic for measuring covering and diameter. And the estimation accuracy by the neural nets are discussed. © 2000 American Institute of Physics.


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