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dc.contributor.authorHaskins, Richard W.-
dc.contributor.authorEvans, James A.-
dc.contributor.authorEbeling, Robert M., 1954--
dc.description.abstractPurpose: This Coastal and Hydraulics Technical Note (CHETN) describes recent efforts undertaken to develop a nondestructive test (NDT) method to detect and locate broken in situ wires within seven-strand post-tension cables used in multistrand anchor systems. While broken wire detection is pursued here as an easier first step, characterization of cross-sectional losses within a cable due to corrosion is the ultimate goal of the cable NDT research. This need was described in the initial project publication Technical Note ERDC\CHL CHETN-IX-28 (Ebeling et al. 2012) and is part of a broader research effort under the work unit Probabilistic Assessment of the Reduced Capacity of Multistrand Post Tensioned Ground Anchorage due to Tendon Corrosion. Highlights from the NDT research component of that effort are briefly introduced in the "INITIAL GUIDED WAVE INVESTIGATIONS" section of this technical note; additional findings and background information are presented in reports by Ebeling et al. (2013) and Haskins et al. (2014). Cable post-tensioning is a method of strengthening concrete with high-strength steel strands. These are typically referred to as tendons and are commonly used in dams, bridges, stadiums, parking structures, rock and soil anchors, houses, and many other structures. Figure 1 (left) and (middle) show a typical cable and multistrand anchor head. While corrosion protection mechanisms have improved over the years, a large inventory of cables with poor or marginal corrosion protection will remain in service for years to come. Even with a modern corrosion protection mechanism, there is a potential for corrosion in the stress-concentrated region of the grip wedge where the assemblage is in closest proximity to the environment and the jacketing materials must be cut back for the wedge-to-steel compression mechanism to function. The primary deterioration mechanism is pitting-corrosion-based loss of cable cross section, generally near the anchor heads and most commonly due to moisture intrusion into the post-tension system. Critical area and radius corrosion loss to cables often results in single wire failures, which may or may not visibly eject wires from the exposed grip wedge. Figure 1 (right) shows a heavily corroded anchorage that was examined during this project. In dams, generally only one end of the cable is accessible. Additionally with navigation structures, the cable’s path is most often deep within the concrete, and inspection methods that rely on shallow concrete cover are not applicable. These characterization technologies that are not generally applicable to locks and dams include magnetic polarity scans, corrosion potential/current measurements, impulse response of the structure, ground penetrating radar, and any form of probing or excavation. Also, in large concrete masses, there is generally less known about the cables’ local environment. Literature reviews conducted in this project have confirmed that a new method must be developed if improved condition assessment of in situ post-tension cables in navigational structures is to be achieved.-
dc.publisherEngineer Research and Development Center (U.S.)-
dc.publisherCoastal and Hydraulics Laboratory (U.S.)-
dc.relation.ispartofseriesERDC/CHL ; CHETN-IX-42-
dc.subjectAnchorage (Structural engineering)-
dc.subjectTendons (Prestressed concrete)-
dc.titleDevelopment of a new nondestructive inspection strategy for corroded multistrand anchor cables-
Appears in Collections:Technical Note

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