Title:
Impact-Echo Thickness Frequency Profiles for Detection of Voids in Tendon Ducts
Author(s):
Odile Abraham and Philippe Cote
Publication:
Structural Journal
Volume:
99
Issue:
3
Appears on pages(s):
239-247
Keywords:
concrete; duct; tendon; test
DOI:
10.14359/11907
Date:
5/1/2002
Abstract:
The detection of voids in grouted tendon ducts in concrete structures is of key importance to the civil engineer. The methods commonly used for such detection is gamma- or x-ray radiography. Unfortunately, these powerful techniques have the disadvantage of requiring a large security zone for radiation protection. Since the end of the 1980s, the impact-echo method, among other nondestructive testing methods, has also been proposed. Shifts in the frequencies associated with the duct depth and in the frequency associated with the slab thickness have been used as indicators of voids in ducts. Usually, the shift in the thickness frequency of the concrete slab thickness serves as a confirmation factor rather than as a distinct diagnostic tool.The objective of this paper is to study the relevance of a detection method based primarily on a shift in the slab thickness resonant frequency above partially empty tendon ducts. One advantage of this criterion, when it proves effective, is that both metal and plastic ducts lead to practically the same behavior. Following a study of the parameters influencing the effectiveness of this criterion through an extensive finite element approach, a systematic experimental setup is proposed to improve this detection method's range of application.