Piezoceramic-based smart aggregate for unified performance monitoring of concrete structures

• US 7,987,728 B2
• Filed: 07/06/2007
• Issued: 08/02/2011
• Est. Priority Date: 07/07/2006
• Status: Active Grant

• Current Assignee: University of Houston System
• Original Assignee: University of Houston System
• Inventors: Song, Gangbing, Gu, Haichang, Mo, Yi-Lung
• Primary Examiner(s): Kirkland, III; Freddie
• Application Number:
  US11/825,370
• Publication Number:
  US 20080034884A1
• Time in Patent Office: 1,488 Days
• Field of Search: 737/86, 738/03
• US Class Current: 73/786
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0066 by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00

Abstract

A system for monitoring the health of a structure, e.g., a concrete wall, bridge, pillars, using a smart aggregate is disclosed. The smart aggregate includes a piezoceramic transducer(s) and associated communication links. The transducer is embedded into the structure prior to the manufacture of the structure. The disclosed system can monitor internal stresses, cracks and other physical forces in the structures during the structures'"'"' life. The system is capable of providing an early indication of the health of the structure before a failure of the structure can occur.

Claims

1. A system for unified monitoring of a concrete structure comprising:

a concrete structure,

a plurality of smart aggregate devices embedded in the concrete structure at desired locations, where each device comprises a small concrete housing including a coated piezoceramic transducer apparatus comprising a piezoceramic patch, two wires soldered directly to a top and a bottom of the patch and a waterproof, insulating coating, where the two wires extend out of the housing and are connected to wires extending out of the concrete structure, and where the devices are positioned in the structure before casting so that the waterproof, insulating coating is in direct contact with the concrete of the housing and with the piezoceramic patch;

a generator coupled to a first smart aggregate device, an actuator device, where the generator is adapted to generate a signal transmitted to the actuator device via its wires inducing its patch to generate a first waveform that propagates through the structure; and

a monitor coupled to one or more second smart aggregate devices, sensor devices, via their wires, where the monitor receives and evaluates a second waveform received by the sensors devices,

where the system is adapted for unified monitoring of the concrete structure comprising;

(1) early-age performance evaluation including casting, hydration, and strength development using a first harmonic waveform and receiving a second harmonic waveform to determine a harmonic amplitude correlating to a desired compressive strength, and (2) health evaluation including internal stresses, crack detection, and other physical forces in the structures, or an indication of a health of the structure before a failure of the structure can occur or damage index data about the structure during its life using a sine sweep first waveform and receiving a sweep second waveform to determine a damage index.

2. The system of claim 1, wherein the piezoceramic patches comprise lead zirconate titanate.

3. The system of claim 1, wherein the structure is a bridge.

4. The system of claim 1, wherein the structure is a building.

5. The system of claim 1, wherein the structure is a pillar.

6. The system of claim 1, wherein each piezoceramic patch has a volume no greater than a product of its length times its width times its height.

7. A method comprising the steps of:

coating a plurality of piezoceramic patches with a water-proof insulating material where each patch comprises a piezoceramic transducer and two wires soldered directly to a top and a bottom of the transducer;

embedding each coated piezoceramic patch in a housing comprising concrete so that the wire extend out past the housing to connect the patch to external devices to form a smart aggregate so that the water-proof, insulating material is the only material between the housing concrete and the piezoceramic patch;

embedding a plurality of the housings in a structure at distributed locations in the structure, prior to casting;

casting the structure to form a concrete structure;

inducing a first waveform in a first piezoceramic transducer of a first housing, where the first waveform comprises a first harmonic waveform for early-stage strength evaluation or the first waveform comprises a first sine sweep waveform for life-time concrete evaluation;

receiving a second waveform from a second piezoceramic transducer of a second housing, where the second waveform comprises a second harmonic waveform for early-stage strength evaluation or the second waveform comprises a second sine sweep waveform for life-time concrete evaluation; and

evaluating the second waveform to determine properties of the concrete structure during early-age strength development, where the properties comprise at least an amplitude of the second harmonic waveform correlating to a compressive strength of the concrete structure, after full strength development and during a life-time of the concrete structure, where the properties comprises at least a damage index.

8. The method of claim 7, wherein the structure concrete and the housing concrete are the same type of concrete.

9. The method of claim 8, wherein the step of embedding the housing occurs prior to the poring or the curing of the concrete.

10. The method of claim 7, wherein the piezoceramic transducers are composed of lead zirconate titanate.

11. The method of claim 7, wherein the housing comprises a concrete block.

12. A system for unified monitoring a structure comprising:

a plurality of blocks, where each block comprises concrete and a coated piezoceramic transducer apparatus, where each apparatus comprises a piezoceramic patch and two wires soldered directly to a top and a bottom of the patch coated with a water-proof, insulating material, where the apparatus is encased in the concrete of the block so that the wires of the patch extend out from the block, where the blocks are adapted to be embedded in a concrete structure at desired locations in the structure so that the water-proof, insulating material is the only material between concrete and the piezoceramic patch;

a waveform generator connected to one of the blocks, the actuator block, via its wires, where the waveform generator is adapted to generate a signal inducing a transducer apparatus inside of one blocks, an actuator block, to generate a first waveform that propagates through the structure, where the first waveform comprises a first harmonic waveform for early-stage strength evaluation or the first waveform comprises a first sine sweep waveform for life-time concrete evaluation; and

a monitor connected to one or more of the other blocks, sensor blocks, via their wires, where the monitor receives and evaluates a second waveform received by one or more of the sensor blocks, where the second waveform comprises a second harmonic waveform for early-stage strength evaluation or the second waveform comprises a second sine sweep waveform for life-time concrete evaluation,

where the system is adapted for unified monitoring of properties of the structure during early-age strength development, where the properties comprise at least an amplitude of the second harmonic waveform correlating to a compressive strength of the concrete structure, and after full strength development and during a life-time of the structure, where the properties comprises at least a damage index.

13. The system of claim 12, wherein the piezoceramic patches are lead zirconate titanate.

14. The system of claim 12, wherein the structure concrete and the housing concrete are the same type of concrete.

15. The system of claim 14, wherein the structure is abridge, building, or a pillar.

16. The system of claim 12, wherein each piezoceramic patch has a volume no greater than a product of its length times it width times its height.

17. A method of fabrication of a smart aggregate comprising the steps of:

soldering two wires directly onto a top and a bottom of a piezoceramic patch,

coating the piezoceramic patch with a water-proof insulating material to form a coated piezoceramic transducer apparatus; and

embedding the coated piezoceramic transducer apparatus into a concrete housing to form the smart aggregate so that the water-proof, insulating material is the only material between the housing concrete and the piezoceramic patch,

where the smart aggregate is adapted for unified monitoring of properties of a concrete structure during early-age strength development and after full strength development and during a life-time of the structure.

18. A method for monitoring the early-age strength monitoring of concrete structure comprising the steps of:

fabricating a plurality of smart aggregate devices, where each device comprises a small concrete housing including a coated piezoceramic transducer comprising a patch and two wires soldered directly to a top and a bottom of the transducer and a water-proof insulating coating, where the wires extend out past the housing for connecting the devices to external devices,

embedding the smart aggregate devices at distributed locations within a concrete structure prior to concrete casting to form a monitoring system within the completed concrete structure so that the water-proof, insulating material is the only material between the housing concrete and the piezoceramic patch,

inducing a first waveform comprising an harmonic excitation having a frequency between 60 kHz and 150 kHz at one of the smart aggregate devices for early-stage evaluation and a sine sweep excitation between 100-10 k Hz,

receiving a response waveform from one or more of the other smart aggregate devices, where the second waveform comprises a second harmonic waveform for early-stage strength evaluation or the second waveform comprises a second sine sweep waveform for life-time concrete evaluation, and

unified monitoring of properties of the structure during early-age strength development, where the properties comprise at least an amplitude of the second harmonic waveform correlating to a compressive strength of the concrete structure and after full strength development and during a life-time of the concrete structure, where the properties comprises at least a damage index.

19. A method for health monitoring of a concrete structure comprising the steps of:

fabricating a plurality of smart aggregate devices, where each device comprises a small concrete housing including a coated piezoceramic transducer apparatus comprising a piezoceramic patch and two wires soldered directly to a top and a bottom of the transducer a water-proof insulating coating, where the wires extend out past the housing for connecting the devices to external devices,

embedding the smart aggregate devices into distributed locations within the concrete structure so that the water-proof, insulating material is the only material between the housing concrete and the piezoceramic patch,

inducing a first waveform comprising a sweep sine over a frequency between 100 Hz and 10 kHz at one of the smart aggregate devices for early-stage evaluation and a sine sweep excitation between 100-10 k Hz,

receiving a response waveform from one or more of the other smart aggregate devices, where the second waveform comprises a second harmonic waveform for early-stage strength evaluation or the second waveform comprises a second sine sweep waveform for life-time concrete evaluation, and

unified monitoring of properties of the structure during early-age strength development, where the properties comprise at least an amplitude of the second harmonic waveform correlating to a compressive strength of the concrete structure and after full strength development and during a life-time of the concrete structure, where the properties comprises at least a damage index.