CA2178373C

CA2178373C - Continuous monitoring of reinforcements in structures

Info

Publication number: CA2178373C
Application number: CA 2178373
Authority: CA
Inventors: Peter O. Paulson
Original assignee: Pure Technologies Ltd
Current assignee: Pure Technologies Ltd
Priority date: 1995-06-06
Filing date: 1996-06-06
Publication date: 2007-04-24
Anticipated expiration: 2016-06-06
Also published as: CA2178373A1

Abstract

Method and apparatus for detecting failure of tensioned reinforcements in a structure by means of a plurality of acoustic or seismic detectors disposed about the structure in a known arrangement, processing signals from the detectors to determine frequency contents and origins, and identifying simultaneous signals as due to the failure of tensioned reinforcements in the structure when they meet spectral oe energy and origin criteria.

Claims

1. A method for monitoring the failure of tensioned reinforcements in a structure comprising the steps of:
(a) positioning a plurality of acoustic or seismic detectors about the structure in a known arrangement and in close proximity to the structure;
(b) processing signals from the detectors;
(c) identifying those of said signals which are due to the failure of a tensioned reinforcement in the structure;
(d) identifying at least one signal received at more than two sensors after passage from an origin through a medium to such sensors;
(e) determining the relative times of arrival of said identified signal at more than two sensors;
(f) calculating the origin of said identified signal from the difference of its time of arrival at each of said more than two sensors.

2. The method as claimed in claim 1, wherein the steps of processing and identifying those of said signals which are due to failure of a tensioned reinforcement further comprise: analyzing said signals from the detectors for frequency contents;
and identifying said signals as being due to failure of a tensioned reinforcement only when the frequency content of said signals exhibits frequencies above a predetermined frequency-threshold and voltages above a predetermined voltage-threshold.

3. The method as claimed in claim 1, wherein the step of processing further comprises: converting the signals from the detectors by Fourier transforms.

4. The method as claimed in claim 3, wherein said signals are identified as being due to the failure of a tensioned reinforcement in the structure if such signals are a plurality of nearly simultaneous acoustic emissions originating from sources located substantially on a line along a tensioned reinforcement cable.

5. The method as claimed in claim 1, wherein said signals are identified as being due to the failure of a tensioned reinforcement in the structure if such signals are a plurality of nearly simultaneous acoustic emissions originating from sources located substantially on a line along a tensioned reinforcement cable.

6. The method as claimed in claim 1, wherein a said signal is identified as being due to the failure of tensioned reinforcement in a structure when it exhibits a short burst having spectral components at frequencies greater than 6 kHz.

7. A method as claimed in claim 1, in which said detectors are placed in contact with the structure.

8. A method as claimed in claim 1, in which said signals are acoustic signals.

9. A method as claimed in claim 1, in which said signals are seismic signals.

10. An apparatus for detecting the location of failure of a tensioned reinforcement in a structure comprising:
(a) a plurality of detectors positioned about the structure in a known arrangement and in close proximity to the structure, the detectors being responsive to acoustic energy or seismic energy or a combination thereof to produce a signal;
(b) a processor comprising means for identifying whether a signal is caused by failure of the tensioned reinforcement in the structure;

(c) means coupling said means for identifying each one of said detectors so that the central processor means receives signals from said detectors along with identification of the detectors sending such signals;
(d) timing means for determining the relative time of arrival of the energy from a signal due to failure of a tensioned reinforcement at each of at least two such detectors;
(e) calculating means associated with said central processor means to calculate the origin of such signal from its relative time of arrival at said at least two detectors; and (f) reporting means to indicate the failure of the tensioned reinforcement at said origin.

11. Apparatus for monitoring the failure of tensioned reinforcements in a plurality of separate structures, comprising: a first detector group which comprises at least three acoustic or seismic detectors in each separate structure: a second detector group which comprises one detector in each separate structure; analog-to-digital converter means for converting signals from said first detector group to digital representations;
means for processing the digital representations of signals from said first detector group to determine whether such signals indicate failure of the tensioned reinforcement; and means for processing the digital representations of signals from the second detector group to determine the particular separate structure which is the source of such signals.

12. Apparatus as claimed in claim 10, in which the processor comprises means for detecting substantially simultaneous signals which are acoustic signals having originals along a linear reinforcement cable.

13. Apparatus as claimed in claim 11, in which the means for processing the digital representations of signals from said first detector group comprises means for detecting substantially simultaneous signals which are acoustic signals having originals along a linear reinforcement cable.