Dynamic Response of Unbonded Prestressing Tendons Cut During Demolition

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Title: Dynamic Response of Unbonded Prestressing Tendons Cut During Demolition

Author(s): Martin S. Williams and Peter Waldron

Publication: Structural Journal

Volume: 86

Issue: 6

Appears on pages(s): 686-696

Keywords: cutting; damping; demolition; dynamic characteristics; post-tensioning; prestressed concrete; prestressing steels; stress waves; unbonded prestressing; Structural Research

Date: 11/1/1989

Abstract:
Numerous concrete structures employ modern construction techniques that may result in demolition problems. A number of such concerns have been highlighted in the field of prestressed concrete, including the cutting of elements post-tensioned by unbonded tendons. Since the tendons are not restrained along their length by bond with the concrete, the sudden energy release due to cutting may cause dangerous movement of the tendon and its end anchorage. A laboratory-based research project has examined movement of tendons cut in this way. Results are presented from a series of tests on unbonded tendons, together with a number of subsidiary tests in whichindividual parameters were studied in detail. The nature of tendon movement is discussed and the various restraints to motion are assessed. Displacements of released tendons are shown to be small, due mainly to the damping effect of the grease layer around the tendon.