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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 Testing—Steel Fatigue Cracking
LTBP Protocol #: FLD-DC-NDE-008


1.

Data Collected

 
1.1 Location and measurements of cracks and discontinuities.  

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 testing (UT) system.  
2.1.3 Wire brush or hand broom.  
2.1.4 Tape measure.  
2.1.5 Temporary marker.  
2.1.6 Digital camera.  
2.1.7 Pencil, sketch pad, and clipboard.  
2.2 Personnel: PRE-PL-LO-005, Personnel Qualifications.  

3.

Methodology

 
3.1 Establishing a local origin:  
3.1.1 Use the segmentation and numbering system (FLD-OP-SC-002, Structure Segmentation and Element Identification System) so defects can be located and noted by a unique element identifier.  
3.1.1.1 Use FLD-OP-SC-003, Determination of Local Origins for Elements, to establish a local origin on each individual element. Establish the two relevant coordinate axes for each face of each element being evaluated.  
3.2 Test preparation:  
3.2.1 Use a wire brush to clean the surface of the bridge element in the area where cracking is suspected and flaw detection and measurement is desired.  
3.2.2 Calibrate the system according to the manufacturer's instructions.  
3.3 Testing:  
3.3.1 Run the procedure as described in the instruction manual of the ultrasonic testing system to do the following:  
3.3.1.1 Configure the transducer wavelength/frequency in order to detect voids (generally, a void must be larger than half the wavelength to be detected).  
3.3.1.2 Create and propagate waves in the material, using couplant and wedges when necessary.  
3.3.1.3 Determine the thickness of the material.  
3.3.1.4 Record reflected waves seeking reflection from defects; convert waveforms into a frequency spectrum if necessary.  
3.3.1.5 Determine the distance to any defect identified.  
3.3.1.6 When a flaw is detected, scan the area, and estimate the length of the crack from beginning point to ending point with the ultrasonic testing system and the tape measure. Collect these values and note the location in the segment.  
3.3.1.7 Mark the beginning and ending points of the crack.  
3.4 Documenting cracks:  
3.4.1 Location:  
3.4.1.1 Document the unique element identifier of the superstructure element on which the crack is located.  
3.4.1.2 Follow FLD-OP-SC-003, Determination of Local Origins for Elements, to establish a local origin on each element; identify the relevant coordinate axis (such as x, z for a girder web), and document the beginning and ending points of the crack using the y, z coordinates.  
3.4.1.3 Describe the location of the crack, e.g., adjacent to the connection of diaphragm 1Di1AB to girder 1A.  
3.4.2 Size and orientation:  
3.4.2.1 Record the length of the crack (from one end to the other in a straight line) in decimal inches using the tape measure, measuring wheel, and/or laser measuring device.  
3.4.2.2 Measure the maximum crack width (opening) with the crack comparison card (crack gage).  
3.4.2.3 Record the orientation of the crack (degrees) using a plump bob, compass, or other angle- measuring device.  
3.4.3 Take photographs (FLD-DC-PH-002, Photographing for Documentation Purposes) and/or draw sketches that illustrate the location and size of the crack.  
3.5 Storing data, documents, and images:  
3.5.1 FLD-DS-LS-001, Data, Document, and Image Storage—Local, for local storage.  
3.5.2 FLD-DS-RS-001, Data, Document, and Image Storage—Remote, for remote storage.  
3.6 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
Text
 
State Code, e.g., Virginia = VA
Green
2 NBI structure number
Text
Text
 
Item 8, Structure Number from NBI Coding Guide
Green
3 Structure name
Text
Text
 
Descriptive name for the bridge, e.g., Route 15 SB over I–66
Green
4 Protocol name
Text
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
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
ºF
Numeric means negative and positive integers, range: -50 to 150
Green
9 Deck surface temperature
Number
1
ºF
Numeric means negative and positive integers, range: -50 to 150
Green
10 Equipment name
Text
Text
 
 
Green
11 Equipment manufacturer
Text
Text
 
 
Green
12 Equipment model name and number
Text
Text
 
If available
Green
13 Comments (equipment)
Text
Unlimited
 
 
Orange
14 Bridge deck thickness
Number
0.5
in.
Range: 0 to 10
Green
15 Pulse period
Number
0.1
 
 
Green
16 Pulse length
Number
1
 
 
Green
17 Pulse voltage
Number
0.1
 
 
Green
18 Sampling rate
Number
1
 
 
Green
19 Samples per scan
Number
1
 
 
Green
20 Location of crack: element type and unique identifier
Text
 
 
Example: Girder 1A; evaluate and record data for each crack identified in the individual element
Blue
21 Test site
Text
 
 
Descriptive location of the crack on the bridge (e.g., adjacent to the connection of diaphragm 1DiAB to girder A)
Yellow
22 Voltage array
Array of numbers
0.000000001
Volts
Voltage array (time history) data for the point; the number of elements are the same as samples per scan (item19) and can be different numbers for each element
Range: -1 to +1
Yellow
23 Thickness of member
Number
0.1
in.
 
Yellow
24 Pair of axis used to locate crack on deck or element
Text
 
 
(x, y),
(x, z), or
(y, z)
Yellow
25 Coordinates of the beginning of the crack
Number
0.125
in.
Example on web (x, z)
Yellow
26 Coordinates of the end of the crack
Number
0.005
in.
Example on web (x, z)
Yellow
28 Crack length
Number
0.1
in.
 
Yellow
29 Crack width
Number
0.01
in.
 
Yellow
30 Presence of rust at crack
List
 
 
Yes or No
Yellow
31 Crack photo
BLOB
 
 
Take one or more photos of each crack identified
Yellow
32 Comments
Text
Unlimited
 
 
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 Comparison should be made with crack data and photos from previous inspections as well as with crack data and photos from FLD-DC-NDE-006, Dye Penetrant Testing, if available.  

6.

Commentary/Background

 
6.1 The purpose of this protocol is to provide a standard procedure for using ultrasonic testing to locate and measure cracks or discontinuities in steel members.  
6.2 Ultrasonic testing uses high-frequency sound energy used for flaw detection and evaluation. A UT system uses a transducer that generates high-frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a void) in the wave path, part of the energy is reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen. Signal travel time can be related to the distance that the signal traveled. From the signal, information about the void location and size can be determined.  
6.3 Only single-sided access is needed when the pulse-echo technique is used. However, there are some limitations to UT: the surface must be accessible to transmit ultrasound, skill and training is more extensive than with other NDE methods, and it requires a coupling medium to promote the transfer of sound energy into the test specimen.  

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-002, Structure Segmentation and Element Identification System.  
7.1.4 FLD-OP-SC-003, Determination of Local Origins for Elements.  
7.1.5 FLD-DC-NDE-006, Dye Penetrant Testing.  
7.1.6 FLD-DC-PH-002, Photographing for Documentation Purposes.  
7.1.7 FLD-DS-LS-001, Data, Document, and Image Storage—Local.  
7.1.8 FLD-DS-RS-001, Data, Document, and Image Storage—Remote.  
7.2 External: None.  

 

 

 

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