Title:
Detecting Voids in Grouted Tendon Ducts of
Post-Tensioned Concrete Structures Using the
Impact-Echo Method
Author(s):
Barbara J. Jaeger, Mary J. Sansalone, and Randall W. Poston
Publication:
Structural Journal
Volume:
93
Issue:
4
Appears on pages(s):
462-473
Keywords:
concretes; grout; impact tests; nondestructive tests; post-tensioning;
prestressing; prestressing steels.
DOI:
10.14359/9705
Date:
7/1/1996
Abstract:
An ongoing research program at Cornell University is aimed at developing the theoretical basis and practical applications for impact-echo, a nonde-structive testing technique based on the use of transient stress waves. This paper discusses a recently completed phase of the program that involved detecting voids in grouted tendon ducts in post-tensioned concrete structures. Results from numerical finite element studies, controlled-flaw laboratory studies, and a field study are presented. Three-dimensional dynamic finite element analyses were performed to examine the response of fully grouted, partially grouted, and ungrouted tendon ducts to transient stress waves. Laboratory specimens were built and tested to verify the numerical results. Numerical and laboratory studies demonstrated that the impact-echo method could be used successfully to detect both complete and partial voids in grouted tendon ducts. Afield study was then conducted on an exist-ing post-tensioned bridge. Fully grouted, partially grouted, and ungrouted tendon ducts located in actual bridge girders were examined. The results of the impact-echo tests were confirmed by invasive testing; the ducts were opened up and visually inspected. The impact-echo results correctly located fully grouted, partially grouted, and ungrouted tendon ducts.