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REPORT
This report is an archived publication and may contain dated technical, contact, and link information
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Publication Number:  FHWA-HRT-16-007    Date:  January 2016
Publication Number: FHWA-HRT-16-007
Date: January 2016

 

Long-Term Bridge Performance (LTBP) Program Protocols, Version 1

Long-Term Bridge Performance Program Logo

Ultrasonic Surface Wave Testing—Concrete
LTBP Protocol #: FLD-DC-NDE-007


1.

Data Collected

 
1.1 Elastic modulus variation of concrete throughout tested deck area.  
1.2 Indications of concrete degradation.  

2.

Onsite Equipment and Personnel Requirements

 
2.1 Equipment:  
2.1.1 PRE-PL-LO-004, Personal Health and Safety Plan.  
2.1.2 Ultrasonic surface wave (USW) equipment/device with impact source and sensors (cart mounted or hand deployed and triggered manually at each test point location); capable of generating and accurately recording signals in a range of at least 5 to 30 kHz positioned inline.  
2.1.3 Data acquisition system, capable of sampling and recording at a minimum rate of 60 kHz.  
2.1.4 Data conditioning and analysis software, capable of filtering, clipping, segmenting, and isolating frequency response data; hand deployed and triggered manually at each test point location.  
2.1.5 Laptop or data logger.  
2.1.6 Hammer.  
2.1.7 Small diameter punch.  
2.1.8 Digital camera.  
2.2 Personnel: PRE-PL-LO-005, Personnel Qualifications.  

3.

Methodology

 
3.1 Use the global rectangular grid (FLD-OP-SC-001, Data Collection Grid and Coordinate System for Bridge Decks) to locate test points on the deck.  
3.2 Test preparation:  
3.2.1 Ensure the deck surface is clear of any debris.  
3.2.2 Measure the thickness of the asphalt overlay, if any, by driving a small diameter punch through the overlay until it reaches the concrete deck and record the embedded length of the punch.  
3.3 Testing:  
3.3.1 Collect data along any test line, as long as the location of every USW reading is properly recorded.  
3.3.2 Place the impact source and sensors in direct contact with the sampled concrete surface.  
3.3.3 Avoid hitting or resting on exposed aggregate, edges or depressions within surface voids, vugs, or surface tining. Otherwise, erroneous signals may be generated, collected, and stored.  
3.3.4 During field operations, note that displayed dispersion curves (modulus vs. depth), calculated modulus, and other data are consistent with expected results based on the design strength of the concrete, overall visible deck condition, and feedback from other nondestructive evaluation (NDE) or concrete condition assessment data. For instance, the variation of modulus with depth is relatively constant in an intact area of a bridge deck. There would be a drop in modulus in the presence of defect within the bridge deck.

NOTE—There should be no chain drag, hammer sounding, coring, impact or hammer drilling, an electric generator, or similar operations producing high-frequency vibration in the proximity (within 100 ft) of the USW equipment. Operation of such equipment may produce frequency responses within the range of interest, which decrease the signal/noise ratio and make it either impossible or more difficult to isolate and interpret collected data.
 
3.4 Traffic in the lanes outside of the work zone is permissible during the data collection.  
3.5 Final forms for collected data include time histories and frequency response of measured raw data at all x and y test locations from gridded deck. Processed data consist of condition grading based on resonant frequency response of impact-echo data (grades 1 to 4), also on an x-y coordinate system.  
3.6 Storing data, documents, and images:  
3.6.1 FLD-DS-LS-001, Data, Document, and Image Storage—Local, for local storage.  
3.6.2 FLD-DS-RS-001, Data, Document, and Image Storage—Remote, for remote storage.  
3.7 Reporting: Transfer all metadata, data, documents, and images to Federal Highway Administration (FHWA), and/or upload all metadata, data, documents, and images into the Long-Term Bridge Performance (LTBP) Bridge Portal.  

4.

Data Collection Table

 
4.1 Table:  
# Field Name Data Type Accuracy Unit Field Description Row Color
1 State
Text
 
 
State Code; e.g., Virginia = VA
Green
2 NBI structure number
Text
 
 
Item 8, structure number; from NBI Coding Guide
Green
3 Structure name
Text
 
 
Descriptive name for the bridge; e.g., Route 15 SB over I–66
Green
4 Protocol name
Text
 
 
Title of the protocol
Green
5 Protocol version
Text
Month and year
 
Month and year the protocol version was published; e.g., May 2015
Green
6 Personnel performing data collection activities
Text
 
 
First name(s) Last name(s)
Green
7 Date data were collected
Text
Exact date
 
mm/dd/yyyy
Green
8 Ambient air temperature
Number
1
°F
Range: -50 to 150
Green
9 Deck surface temperature
Number
1
°F
Range: -50 to 150
Green
10 Equipment name
Text
 
 
 
Green
11 Equipment manufacturer
Text
 
 
 
Green
12 Equipment model name and number
Text
 
 
If available
Green
13 Comments (equipment)
Text
Unlimited
 
 
Orange
14 Overlay material
Text
 
 
 
Green
15 Overlay thickness
Number
0.5
in.
 
Green
16 Bridge deck thickness
Number
0.5
in.
Range: 0 to 10
Green
17 Source type
Text
 
 
Range: 0 to 60
Green
18 Sensor type
Text
 
 
 
Green
19 Source sensor spacing
Number
0.1
in.
Range: 0.1 to 20
Green
20 Sensor 1
Sensor 2 spacing
Number
0.1
in.
Range: 0.1 to 20
Green
21 Pulse period
Number
0.1
 
 
Green
22 Pulse length
Number
1
 
 
Green
23 Sampling rate
Number
1
 
 
Green
24 Samples per scan
Number
1
 
Range: 0 to 16,400
Green
25 Number of pretrigger samples
Number
1
 
 
Green
26 Span number
Text
 
 
Span 1, Span 2, Span N (if testing on deck surface)
Blue
27 Test site
Text
 
 
Describe the location of the test on the bridge (e.g., shoulder and lane 1)
Blue
28 Location of test site
(x-coordinate)
Number
1
ft
Transverse distance from the grid origin
Blue
29 Location of test site
(y-coordinate)
Number
1
ft
Longitudinal distance from the grid origin
Blue
30 Hammer voltage array
Array of numbers
0.000000001
V

Voltage array (time history) data for the test point;
the number of elements are the same as samples per scan (item24) and can be different numbers for each element
Range: -1 to +1

Yellow
31 Sensor 1 voltage array
Array of numbers
0.000000001
V
Yellow
32 Sensor 2 voltage array
Array of numbers
0.000000001
V
Yellow
33 Comments
Text
 
 
 
Orange
4.2 Table Key:  
Column Descriptions
#
Sequential number of data item
Field Name
Data field name
Data Type
Type of data, such as text, number, predefined list, binary large object (BLOB), or PDF file
Accuracy
Accuracy to which the data are recorded
Unit
Unit in which a measurement is taken and recorded
Field Description
Commentary on the data or list of items in a predefined list
Row Color Key
Green
Data items only entered once for each protocol for each day the protocol is applied
Pink
Logical breakdown of data by elements or defect types (not always used)
Blue
Data identifying the element being evaluated or the type of defect being identified
Yellow
LTBP data reported individually for each element or defect identified
Orange
Comments on the data collection or data entered

5.

Criteria for Data Validation

 
5.1 Verification and comparison should be made with results obtained from other NDE methods, including sounding methods, such as chain drag (FLD-DC-VIC-003, Concrete Deck—Spalls and Delamination), acoustic methods, electromagnetic methods, as well as with ground truth data.  

6.

Commentary/Background

 
6.1 The purpose of this protocol is to provide a standard procedure for using USW testing to measure the elastic modulus of concrete. Significant changes in the modulus between two periodical measurements are an indication of concrete degradation. Changes in the modulus among several periodic measurements can be used to map the condition degradation rate of a structure over time.  
6.2 USW testing is the measurement of the velocity of surface waves in concrete of a bridge deck or other reinforced concrete members. The measured velocity of surface waves is linked to the elastic modulus. The frequency range of interest in testing of bridge decks and other concrete members is between 5 and 30 kHz. The testing equipment consists of an impact source and two receivers, positioned along a line, so that velocity of the surface wave can be determined with the distance between two sensors (displacement or velocity transducers, or accelerometers) and the travel time of the surface wave as it propagates away from the near receiver to the far receiver. The spacing of sensors on the instruments used for USW measurement specifies the penetration depth of surface waves. The rule of thumb is that the sensors’ spacing should be half the member’s thickness to measure the variation of surface wave velocity over the full depth of the concrete member.  

7.

References

 
7.1 LTBP Protocols:  
7.1.1 PRE-PL-LO-004, Personal Health and Safety Plan.  
7.1.2 PRE-PL-LO-005, Personnel Qualifications.  
7.1.3 FLD-OP-SC-001, Data Collection Grid and Coordinate System for Bridge Decks.  
7.1.4 FLD-DC-VIC-003, Concrete Deck—Spalls and Delamination.  
7.1.5 FLD-DC-PH-002, Photographing for Documentation Purposes.  
7.1.6 FLD-DS-LS-001, Data, Document, and Image Storage—Local.  
7.1.7 FLD-DS-RS-001, Data, Document, and Image Storage—Remote.  
7.2 External:  
7.2.1 S2-R06A-RR-1, Nondestructive Testing to Identify Concrete Bridge Deterioration, Transportation Research Board, Washington, DC, 2013.  

 

 

 

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