Probe of Unfilled Sheath of Prestressed-Concrete Girder Bridge Using Impact-Echo Method
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Sheaths are arranged in the web and lower part of prestressed-concrete girder bridges, and prestressing wires and concrete are indirectly bonded together by filling interior parts of the sheaths. However, when the filling is not sufficient,water can penetrate the interior parts of the sheaths and, thereby, prestressing wires can be corroded or transverse cracks would occur around sheaths by the freezing and thawing action of the penetrated water. Therefore, it is an important element in maintenance management of structures to find out the sheaths unfilled with grout early after construction. In this paper, in order not to damage bridge members, the impact-echo method with a new approach in application is used to probe sheaths unfilled with grout for real structures. The location of sheaths is first estimated with reinforcing bar probing instrument of radar type and the measurement locations of sheaths are determined. By sending elastic wave to the side of girders and receiving the response, the location of the unfilled part of a sheath was estimated from the difference between high frequency peak and twice the resonance frequency indicating thickness. To verify the location of void estimated by the impact-echo method, pictures were taken by an industrial fiber scope after drilling a hole.
Abstract
Sheaths are arranged in the web and lower part of prestressed-concrete girder bridges, and prestressing wires and concrete are indirectly bonded together by filling interior parts of the sheaths. However, when the filling is not sufficient,water can penetrate the interior parts of the sheaths and, thereby, prestressing wires can be corroded or transverse cracks would occur around sheaths by the freezing and thawing action of the penetrated water. Therefore, it is an important element in maintenance management of structures to find out the sheaths unfilled with grout early after construction. In this paper, in order not to damage bridge members, the impact-echo method with a new approach in application is used to probe sheaths unfilled with grout for real structures. The location of sheaths is first estimated with reinforcing bar probing instrument of radar type and the measurement locations of sheaths are determined. By sending elastic wave to the side of girders and receiving the response, the location of the unfilled part of a sheath was estimated from the difference between high frequency peak and twice the resonance frequency indicating thickness. To verify the location of void estimated by the impact-echo method, pictures were taken by an industrial fiber scope after drilling a hole.
참고문헌 (4)
- Gokudan, K, "Measurement of the Grout Filling Degree in Sheath of the PC Bridge by the Impact-Echo Method", Proceedings of JCI, 24(1), pp.1557~1562 (2002)
- Kurosawa, N, "Influence of Magnitude of Impactor to the Accuracy of Measurement to Detect the Internal Defect of Concrete by Impact-Echo Method", Proceedings of the Annual Conference of Tohoku Branch of JSCE (2010)
- Sansalone, M, "Detecting Delaminations in Concrete Slabs with and without Overlays Using the Impact-Echo Method", ACI Materials Journal, 86(2), pp.175~184 (1989)
- Tomita, Y, "Nondestructive Evaluation of Fresh Grouting Performance in Prestressed Concrete Members by Impact Echo", Journal of JSCE, (648), pp.127~135 (2000)