The GPR survey of bridges in Utica, NY found wide variation in bridge deck condition, with some spans showing localized deterioration and others showing deterioration over large areas. Percentages of deteriorated deck area ranged from 3% to 43% across spans. Overall bridge condition did not represent condition on individual spans. The survey results can guide strategies for rehabilitating and repairing the most deteriorated areas.

1. Findings from
Ground Penetrating Radar Survey
of Bridge Network
in Utica, NY
ARMA International, LLC.
3 Computer Drive West
Ste. 102
Albany, NY 12205
P & F: (518) 813-9269
www.ARMATech.net

2. Outline
 Overview of Ground Penetrating Radar (GPR) Methodology
 Brief background
 Equipment
 Steps to results
 ASTM Standard
 Surveyed Bridges in Utica, NY
 GPR Survey Findings

3. GPR: Brief Background
GPR occupies this range of frequencies in
the electromagnetic spectrum
 The radiation emitted from a GPR antenna consists of
a broad band of frequencies with a central frequency
that designates what application it is intended for
 Frequency determines the range of penetration and
level of resolution
 The results generated are based on the dielectric
properties of the material along with other factors

4. GPR: Brief Background (Cont’d)
 Pulse Wave Form
 Wide range of frequencies
 Central frequency has highest amplitude
Amplitude
Frequency

5. GPR: Brief Background (Cont’d)
 Radiating Energy
 Squashed cone

6. GPR System Components
• Transmitter generates
EM wave
• Energy reflected is
captured by a receiving
antenna
• Transmitter and receiver
operate as one unit
• Data captured is processed into images and output is displayed
on color monitor

7. GPR in Layered Systems
The reflection of electromagnetic waves forms a stratigraphy of layers due to
the change in material as the antenna passes along the surface
Position and depth information is found by reading distance traveled along the
line of scan, the travel time of transmission and reflection, and the strength of
the reflected signal

8. GPR for Subsurface Targets
χ1 χ2 χ3 χ4 χ5
χ1 χ2 χ3 χ4 χ5
 How Targets Are “Seen”
 Concave down parabola
 Shaped formed due to travel time

9. Dielectric Value and Its Role
 Affects Depth of Penetration and Intensity
 Used to determine depth
Material Dielectric
Air 1
Concrete 6-8
c v = wave propagation speed
Asphalt 3-5
v c = speed of light
PVC 3
K K = relative dielectric permittivity
“Average soil" 16
s = interface depth Sand (dry) 3-6
s vt v = wave propagation speed Sand (wet) 25 - 30
2 t = two-way travel time Silt (wet) 10
Clay (wet) 8 - 15
Clay soil (dry) 3
Water (fresh) 81
Water (sea) 81
Pure ice 3.2

10. GPR Equipment
 GPR Antenna Types: Air-Coupled and Ground-Coupled
 Air-Coupled
 Mounted above ground
 Fast surveys, about 55 mph
 Penetration about 1 meter or less
 Low resolution
 Ground-Coupled
 Maintain ground contact
 Slower survey speeds, <10 mph
 Penetration ranges from 0.5 m to 25 m
 High resolution

11. GPR Equipment (Cont’d)
 High Speed Surveys
 Performed at posted speeds
 Utilize air-horn antennas
 Typical data collection rates: 6 scans/ft., 3 ft. spacing between survey
passes
 Depth of penetration: approximately 3 ft.
12’
1.5’ 3’ 3’ 3’ 1.5’1.5’

12. GPR Equipment (Cont’d)
 Support and Safety
 Position and distance measurement
 Wheel mounted distance measuring instrument (DMI)
 Camera on extending pole provides lane positioning
 Safety lights
 Strobe and rotating beacons
 Arrow board

13. Steps to Results
 GPR Data Processing and Interpretation
 Calibration
 Filtering
 Processing
 Interpretation

14. ASTM Standard
 ASTM D6807-07 entitled “Standard Test Method for Evaluating
Asphalt-Covered Concrete Bridge Decks Using Ground
Penetrating Radar.”
 Provides guidance on what type of survey to be used for different
applications
 Equipment configuration
 Guidance on establishment of threshold to be used as the point
between suspected deterioration and “good” subsurface condition
 Provides methods to bring GPR results from a statistical result to real-
world condition through the use of supplemental methods (e.g. cores,
hammer sounding, etc.)

15. Surveyed Bridges in Utica, NY
 Small Network
 All bridges have bare concrete deck
 BIN: 1002281, Carries Rt. 5 Southbound crossing Rt. 5S, 19
spans, 31,702 sq. ft. surveyed
 BIN: 1002282, Carries Rt. 5 Northbound crossing Rt. 5S, 18
spans, 31,856 sq. ft. surveyed
 BIN: 100228A, On-ramp for Rt. 5 Southbound from Rt. 5S
Westbound, 4 spans, 3,917 sq. ft. surveyed
 BIN: 100228B, Off-ramp from Rt. 5 Northbound to Rt. 5S
Westbound, 3 spans, 3,005 sq. ft. surveyed
N

16. GPR Survey Findings
 Tables Listing Percent Area of Deterioration for Each Span
 Deterioration Maps Visualize Location and Extent of
Deterioration BIN: 1002281
Percent Area of Deterioration BIN: 1002282
Approach 22% Percent Area of Deterioration
Span 1 24% Approach 22%
Span 2 10% Span 1 9%
BIN: 100228A
Span 3 17% Span 2 15%
Percent Area of Deterioration
Span 4 24% Span 3 11%
Approach 28%
Span 5 15% Span 4 18%
Span 1 36%
Span 6 6% Span 5 18%
Span 2 21%
Span 7 36% Span 6 24%
Span 3 16%
Span 8 30% Span 7 36%
Span 4 14%
Span 9 3% Span 8 27%
Overall 21%
Span 10 16% Span 9 43%
Bridge Only 20%
Span 11 37% Span 10 37%
Span 12 18% Span 11 43%
Span 13 22% Span 12 38%
Span 14 32% Span 13 7%
BIN: 100228B Span 15 38% Span 14 16%
Percent Area of Deterioration Span 16 35% Span 15 9%
Span 1 15% Span 17 21% Span 16 10%
Span 2 31% Span 18 8% Span 17 9%
Span 3 28% Span 19 13% Span 18 26%
Approach 15% Approach 20% Approach 27%
Overall 24% Overall 20% Overall 21%
Bridge Only 26% Bridge Only 20% Bridge Only 21%

17. GPR Survey Findings (Cont’d)
 Wide Variation in Condition
 Spans with both localized and large areas or deterioration
 Low, medium, and high degrees of deterioration
 Small, medium, and large percent areas of deterioration on spans for
each bridge
 Overall bridge condition does not really represent the condition
present on spans
 Results Focus on Trouble Areas
 The maps can guide rehabilitation and repair strategies
 Other findings
 Hmm
 Hmm