Continuous monitoring of reinforcements in structures

• US 5,798,457 A
• Filed: 06/06/1995
• Issued: 08/25/1998
• Est. Priority Date: 06/25/1993
• Status: Expired due to Term

• Current Assignee: Pure Technologies Limited (Xylem, Inc.)
• Original Assignee: Pure Technologies US Incorporated (Xylem, Inc.)
• Inventors: Paulson, Peter O.
• Primary Examiner(s): Oda, Christine K.
• Application Number:
  US08/467,666
• Time in Patent Office: 1,176 Days
• Field of Search: 340/566, 340/690, 364/508, 364/421, 73/579, 73/581, 73/582, 73/583, 73/587, 73/594, 73/786, 73/801
• US Class Current: 73/587
• CPC Class Codes: E04C 5/08 Members specially adapted to be used in prestressed constructions production of reinforced objects in general B28B23/00; prestressed structures produced in situ E04G21/12
• CPC Class Codes: G01H 1/00 Measuring characteristics of vibrations in solids by using direct conduction to the detector G01H9/00, G01H11/00 take precedence
• CPC Class Codes: G01N 2291/011 Velocity or travel time
• CPC Class Codes: G01N 2291/02458 Solids in solids, e.g. granules
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00
• CPC Class Codes: G01N 29/38 by time filtering, e.g. using time gates
• CPC Class Codes: G01N 29/46 by spectral analysis, e.g. Fourier analysis or wavelet analysis spectral signal processing per se G06F17/14
• CPC Class Codes: G01V 1/001 Acoustic presence detection
• CPC Class Codes: G01V 1/20 Arrangements of receiving elements, e.g. geophone pattern

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 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

indentifying 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 reinforcememt 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.