Fatigue Crack Detection Using Unmanned Aerial Systems in Under-Bridge Inspection

121 Pages·2017·5.94 MB·English

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RP 256
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Fatigue Crack Detection Using
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T Unmanned Aerial Systems in
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Under-Bridge Inspection
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N

R S
E P
By
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Sattar Dorafshan
A R
R T Marc Maguire
C
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H Nathan V. Hoffer
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I Calvin Coopmans
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P

O N
R Department of Civil and Environmental Engineering
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E Utah State University
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R Prepared for
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Idaho Transportation Department
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Research Program, Contracting Services
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N Division of Engineering Services
T http://itd.idaho.gov/alt-programs/?target=research-program

August 2017
Standard Disclaimer
This document is disseminated under the sponsorship of the Idaho Transportation Department and the
United States Department of Transportation in the interest of information exchange. The State of Idaho
and the United States Government assume no liability of its contents or use thereof.
The contents of this report reflect the view of the authors, who are responsible for the facts and
accuracy of the data presented herein. The contents do not necessarily reflect the official policies of the
Idaho Transportation Department or the United States Department of Transportation.
The State of Idaho and the United States Government do not endorse products or manufacturers.
Trademarks or manufacturers’ names appear herein only because they are considered essential to the
object of this document.
This report does not constitute a standard, specification or regulation.
1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No.
FHWA-ITD-17-256
4. Title and Subtitle 5. Report Date
Fatigue Crack Detection Using Unmanned Aerial Systems in Under-Bridge August 2017
Inspection 6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.
Sattar Dorafshan, Marc Maguire, Nathan V. Hoffer, Calvin Coopmans
9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)
Department of Civil and Environmental Engineering
Utah State University 11. Contract or Grant No.
4110 Old Main Hill USU-2016-01
Logan, UT 84322
12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered
Idaho Transportation Department Final Report
Division of Engineering Services, Contracting Services, Research Program 02/01/2016 - 1/31/2017
PO Box 7129 14. Sponsoring Agency Code
Boise, ID 83707-7129 RP 256
15. Supplementary Notes
Project performed in cooperation with the Idaho Transportation Department and FHWA.
16. Abstract
The applications of Unmanned Aerial Systems (UAS) for bridge inspection, with emphasis on under-bridge inspection and
fatigue crack detection, were studied in this report. The potential benefits and challenges of using UAS for bridge inspection
were identified through an extensive literature survey. The feasibility of using UAS for fatigue crack detection was studied by
determining the minimum lighting, camera distance and environmental requirements for three UAS. The DJI Mavic UAS
performed better than the others in both indoor and outdoor GPS-denied inspections. An in-service bridge in Ashton, Idaho
was inspected using this UAS to find fatigue cracks. No fatigue crack, known or new, was detected in the UAS images but
marker lines around the known fatigue cracks (drawn by the inspectors in previous inspections), concrete defects, and steel
rust were detected. Thermography showed promising results for fatigue crack detection in a lab setting, but it was not
feasible for UAS applications since it had to be performed using active thermography techniques to obtain adequate results.
Additionally, image processing algorithms for autonomous detection of both concrete and fatigue cracks were successfully
developed. These algorithms, especially for fatigue crack detection, require more images to perform better, but were
demonstrated as feasible to aid in a real-time inspection.
17. Key Words 18. Distribution Statement
Unmanned Aerial Vehicles, Unmanned Aerial Systems, Bridge Copies available online at
Inspection, Fatigue Cracks, Concrete Cracks, Bridge Condition http://itd.idaho.gov/alt-
Assessment, Remote Sensing, Thermography, Image Processing, programs/?target=research-program
Fracture Critical Bridge Inspection.
19. Security Classification (of this report) 20. Security Classification (of this page) 21. No. of Pages 22. Price
Unclassified Unclassified 120 None
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METRIC (SI*) CONVERSION FACTORS
APPROXIMATE CONVERSIONS TO SI UNITS APPROXIMATE CONVERSIONS FROM SI UNITS
Symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By To Find Symbol

LENGTH LENGTH

in inches 25.4 mm mm millimeters 0.039 inches in
ft feet 0.3048 m m meters 3.28 feet ft
yd yards 0.914 m m meters 1.09 yards yd
mi Miles (statute) 1.61 km km kilometers 0.621 Miles (statute) mi

AREA AREA

in2 square inches 645.2 millimeters squared cm2 mm2 millimeters squared 0.0016 square inches in2
ft2 square feet 0.0929 meters squared m2 m2 meters squared 10.764 square feet ft2
yd2 square yards 0.836 meters squared m2 km2 kilometers squared 0.39 square miles mi2
mi2 square miles 2.59 kilometers squared km2 ha hectares (10,000 m2) 2.471 acres ac
ac acres 0.4046 hectares ha

MASS MASS
(weight) (weight)

oz Ounces (avdp) 28.35 grams g g grams 0.0353 Ounces (avdp) oz
lb Pounds (avdp) 0.454 kilograms kg kg kilograms 2.205 Pounds (avdp) lb
T Short tons (2000 lb) 0.907 megagrams mg mg megagrams (1000 kg) 1.103 short tons T

VOLUME VOLUME

fl oz fluid ounces (US) 29.57 milliliters mL mL milliliters 0.034 fluid ounces (US) fl oz
gal Gallons (liq) 3.785 liters liters liters liters 0.264 Gallons (liq) gal
ft3 cubic feet 0.0283 meters cubed m3 m3 meters cubed 35.315 cubic feet ft3
yd3 cubic yards 0.765 meters cubed m3 m3 meters cubed 1.308 cubic yards yd3

Note: Volumes greater than 1000 L shall be shown in m3

TEMPERATURE TEMPERATURE
(exact) (exact)

oF Fahrenheit 5/9 (oF-32) Celsius oC oC Celsius temperature 9/5 oC+32 Fahrenheit oF
temperature temperature temperature

ILLUMINATION ILLUMINATION

fc Foot-candles 10.76 lux lx lx lux 0.0929 foot-candles fc
fl foot-lamberts 3.426 candela/m2 cd/cm2 cd/cm candela/m2 0.2919 foot-lamberts fl
2

FORCE and FORCE and
PRESSURE or PRESSURE or
STRESS STRESS

lbf pound-force 4.45 newtons N N newtons 0.225 pound-force lbf
psi pound-force per 6.89 kilopascals kPa kPa kilopascals 0.145 pound-force psi
square inch per square inch

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Acknowledgements
The authors would like to acknowledge the Idaho Transportation Department for funding this research.
Several students and research personnel helped to complete this project, including, Hannah Young,
Hunter Buxton, Dan Robinson, Shawn Grant, Abhishek Manjunath, Parwinder Mehrok and Anusna
Chakraborty. The assistance of the Technical Editor Hannah Young and Peer Reviewer George Hearn was
appreciated.
Technical Advisory Committee
Each research project is supervised by a technical advisory committee (TAC), led by an ITD project
sponsor and project manager. The Technical Advisory Committee (TAC) is in charge of overseeing the
project progress, reviewing deliverables and ensuring that study objectives are met in a timely manner.
The work of the following TAC members in guiding this research study is gratefully recognized.
Project Sponsor – Matt Farrar, PE, State Bridge Engineer
Project Manager – Dan Gorley, PE, Bridge Asset Management Engineer
TAC Members
Alan Buehrig, PE
Mike Pape
James Bennett
FHWA-Project Advisor — Ed Miltner, PE

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Table of Contents
Executive Summary .................................................................................................................................... xvii
Chapter 1 Introduction ................................................................................................................................. 1
Research Motivation ................................................................................................................................. 1
Use of UASs by ITD .................................................................................................................................... 2
Research Objectives .................................................................................................................................. 3
FAA Regulations for Flying UASs ............................................................................................................... 3
UAS Definitions ......................................................................................................................................... 6
Interpretation of Photographic Images .................................................................................................... 7
Pilot ........................................................................................................................................................... 7
Archived Data ............................................................................................................................................ 7
Chapter 2 Literature Review ......................................................................................................................... 9
UAS Applications for Bridge Inspection .................................................................................................... 9
California ................................................................................................................................................... 9
Georgia ...................................................................................................................................................... 9
Michigan.................................................................................................................................................. 10
Minnesota ............................................................................................................................................... 10
Florida ..................................................................................................................................................... 11
Literature Review Summary .................................................................................................................... 12
Chapter 3 Small Bridge Experiment ............................................................................................................ 15
Concrete Surface Cracks ......................................................................................................................... 16
Automated Concrete Surface Crack Detection ....................................................................................... 17
Deck Thermal Inspection ........................................................................................................................ 19
Girder Inspection .................................................................................................................................... 20
Off-the-Shelf 3D Model Reconstruction ................................................................................................. 21
Lessons Learned from the Small Bridge Experiment .............................................................................. 22
Chapter 4 Fatigue Crack Detection Requirements ..................................................................................... 23
Fatigue Definition .................................................................................................................................... 23
Current Practice for Fatigue Crack Detection ......................................................................................... 24
Selected UASs ......................................................................................................................................... 24
Fatigue Crack Detection-Minimum Conditions ....................................................................................... 24
Equipment ........................................................................................................................................... 25
Lighting Condition Definitions and Camera Distance ......................................................................... 26
Indoor Office Procedure ......................................................................................................................... 27
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Indoor Office Results ............................................................................................................................... 27
GoPro .................................................................................................................................................. 27
DJI Camera .......................................................................................................................................... 28
Nikon Camera ...................................................................................................................................... 30
Findings ............................................................................................................................................... 30
Inspection in a Controlled Environment ................................................................................................. 31
3DR Iris Indoor Inspection ................................................................................................................... 32
DJI Mavic Indoor Inspection ................................................................................................................ 32
Goose Indoor Inspection ..................................................................................................................... 32
Indoor Inspection Conclusion ............................................................................................................. 35
Outdoor Bridge Inspections .................................................................................................................... 36
3DR Iris Outdoor Inspection ................................................................................................................ 36
DJI Mavic Outdoor Inspection ............................................................................................................. 38
Goose Outdoor Inspection .................................................................................................................. 41
Outdoor Inspection Conclusions ......................................................................................................... 41
Autonomous Fatigue Crack Detection .................................................................................................... 42
Image Processing Using the 3DR Iris Photographs ............................................................................. 43
Image Processing Using the DJI Mavic Photographs .......................................................................... 43
Image Processing Using the Goose Photographs ............................................................................... 43
Autonomous Fatigue Crack Detection Conclusion ............................................................................. 45
Passive Thermal Fatigue Crack Detection ............................................................................................... 45
Active Thermal Fatigue Crack Detection ................................................................................................. 49
Thermal Fatigue Crack Detection Summary ....................................................................................... 54
Controlled Fatigue Crack Detection Conclusions .................................................................................... 55
Chapter 5 UAS Bridge Inspection in Ashton, Idaho..................................................................................... 59
Introduction ............................................................................................................................................ 59
Inspection Images ................................................................................................................................... 63
Image Processing and the Inspection Images ......................................................................................... 69
UAS Fatigue Crack Detection Comparison to Manned Inspections ........................................................ 70
Conclusion and Recommendation from the Inspection ......................................................................... 75
Chapter 6 Conclusions ................................................................................................................................ 77
Conclusions ............................................................................................................................................. 77
Recommendations and Future Work ...................................................................................................... 81
References .................................................................................................................................................. 83
Appendix A List of Specimens and Experiments ......................................................................................... 85
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Appendix B Concrete Crack Detection Code ............................................................................................... 89
Appendix C Fatigue Crack Detection Code ................................................................................................. 97

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