Unbonded Performance

by Morris Schupack, (M.ASCE), President; Schupack Suarez Engineers, Inc. 225 Wilson Ave., Norwalk, CT 06854,

Serial Information: Civil Engineering—ASCE, 1989, Vol. 59, Issue 10, Pg. 75-77

Document Type: Feature article


Unbonded single strand tendons have been used in the U.S. for about 30 years. In a small number of buildings, strand corrosion failures have occurred. Although it is clear that post-tensioning steel and its anchorage should be protected against corrosion, comprehensive corrosion protection recommendations were not written until 1985, the year the Post Tensioning Institute issued Specifications for Unbonded Single Strand Tendons. As expected, corrosion continues to surface in structures that predate PTI's specifications. But, telltale signs of corrosion at anchorage pockets are also showing up in structures barely five years old. So it seems an appropriate time to reexamine unbonded tendons, reviewing good and bad details and construction practices that lead to the 1985 recommendations.

Subject Headings: Corrosion | Tendons | Anchorages | Failure analysis | Tension | Steel | Ultimate strength | Tension members

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