POST-TENSION HEADACHE

The Department of Transport has postponed the use of grout-duct post tensioned bridge designs pending the results of research into the possibility of a corrosion problem. Design and construction standards are being revised and 600 existing bridges are being investigated. Examples are given of corrosion damage to tendons on a number of bridges thought to be due to poor grouting and voids. There is renewed interest in external tendoning, which is an alternative to integral post tensioning. The new Severn crossing between England and Wales is to be built with unbonded external tendons. This technique is slightly more costly and the prestressing is not used so efficiently. Existing bridges are drilled to examine wires with radar sometimes being used to locate the tendons. The presence of corrosion does not necessarily mean that the bridge needs to be replaced and methods of continuously monitoring prestress loss is seen as an important development. A fibre-optic method is outlined making use of the property that the amount of light lost from a bent fibre-optic is proportional to the degree of bend. Other non-destructive testing techniques outlined include the use of X-rays and examination of the shape of an electrical impulse passed down the strand. Advances in monitoring technology also mean that the corrosion may be determined more accurately and less bridges would need replacing.

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  • Corporate Authors:

    Reed Business Information, Limited

    Quadrant House, The Quadrant
    Brighton Road
    Sutton, Surrey  United Kingdom  SM2 5AS
  • Authors:
    • Campbell, J
  • Publication Date: 1992-10-15

Language

  • English

Media Info

  • Pagination: p. 14-5
  • Serial:
    • SURVEYOR
    • Publisher: Hemming Group, Limited
    • ISSN: 0039-6303

Subject/Index Terms

Filing Info

  • Accession Number: 00675140
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Mar 28 1995 12:00AM