NDE for Bridge Assessment using Image Processing and Infrared 1

Thermography 2

3

Masato MATSUMOTO 4

Executive Vice President, NEXCO-West USA, Inc., 5

1015, 18th Street, N.W., Suite 504, Washington, DC, USA 6

TEL: 202-223-7040, email: m.matsumoto@w-nexco-usa.com 7

8

Koji MITANI 9

President & CEO, NEXCO-West USA, Inc. 10

1015, 18th Street, N.W., Suite 504, Washington, DC, USA 11

TEL: 202-223-7040, email: k.mitani@w-nexco-usa.com 12

13

F. Necati CATBAS 14

Dept. of Civil, Environmental and Construction Engineering 15

University of Central Florida 16

4000, Central Florida Blvd, Orlando, FL, USA 17

TEL: 407-823-3743, Email: catbas@ucf.edu 18

19

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(This Paper includes 2,788 words, 4 tables and 15 figures = 7,688 words) 21

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Submission date: August 1, 2014 23

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Abstract 25

Traditionally, highway bridge conditions have been monitored by visual inspection with structural 26

deficiencies being manually identified and classified by qualified engineers and inspectors. The need for 27

safer and more objective inspection methods calls for new innovations in bridge inspection technologies. 28

One of major toll road operators in Japan has been working to develop efficient non-destructive highway 29

bridge inspection methods using high quality digital image and Infrared (IR) thermography technologies. 30

This paper describes the results of on-site applications of above technologies performed in conjunction with 31

the joint research with University of Central Florida. In March, 2014, a bridge condition assessment project 32

was performed at the SR417 Bridge #770054 (Lake Jessup Bridge) for the purpose of utilizing the digital 33

imaging and infrared (IR) technology to evaluate its capabilities in detecting surface and subsurface 34

indications within the concrete structure and determine the AASHTO element level condition state for the 35

bridge decks, railings and beams. After the execution of the surface transportation act ‘Moving Ahead for the 36

Progress in the 21st Century Act (MAP-21)’ in July 2012, it is mandatory that the element level condition 37

states for bridges carrying National Highway Systems (NHS) be reported biannually to the federal 38

government. Applying a more efficient method to collect filed data to determine the current state of a bridge 39

can save significant time and lead to cost reduction for bridge owners. The scanning systems presented in 40

this paper were proved to be capable of calculating quantity of distressed areas in terms of cracking and 41

delamination rapidly and accurately. 42

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1. Introduction 44

Condition ratings of bridge components in the Federal Highway Administration (FHWA)’s Structure 45

Inventory and Appraisal (SI&A) database are determined by bridge inspectors in the field for bridge deck, 46

superstructure and substructure. This information has been used by bridge owners as a basis for decisions on 47

bridge maintenance, rehabilitation, and replacement. The condition ratings also influence a bridge’s 48

Sufficiency Rating (SR), as well as whether the bridge may be classified as “structurally deficient”. 49

However, the determination of bridge condition ratings is generally subjective depending on individual 50

inspectors’ knowledge and experience, as well as varying field conditions. For the evaluation and 51

documentation of concrete deterioration (cracks, potholes, delamination, spalls, etc.) and changes over time, 52

the current practice can be lacking in accuracy and completeness, as well as time consuming and costly if 53

road closures are required for the inspection (Fig.1). 54

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Fig.1: Current Bridge Inspection Practice 70

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Recent advancements in imaging technologies have made their applications practical and possible in more 72

detailed bridge inspections. The technologies can overcome some shortcomings of human subjectivity and 73

are intended to improve and complement, but not to replace, human inspections. The innovative technologies 74

presented herein will be able to make bridge inspections more objective, more consistent, more scientific, 75

and more efficient. The need for utilization of thermography has been advocated especially for detecting 76

subsurface defects using low-cost hand-held infrared cameras by Washer et al. These thermal imaging 77

cameras are intended to be used by the state DOT personnel using while they are conducting their 78

conventional visual inspections and walk-throughs [1]. Guideline requirements developed for the effective 79

application of the technology in the field using the hand-held cameras are also described along with 80

application of the technology for the detection of deterioration in a typical highway bridge [2]. In this paper, 81

the authors present the integrated use of high-end infrared thermography (IR) and line sensors to obtain 82

bridge deck cracks, defects and delamination at a very rapid and high resolution for structural assessment and 83

decision making [3]. The authors present that the integrated system can scan a network of bridge decks from 84

a vehicle at 50 mph (without any lane closure) with excellent detail in a matter of couple days. In order to 85

validate the effectiveness of the new inspection technologies, a pilot inspection project was conducted 86

through a joint research effort with the University of Central Florida (UCF). The objective of the research 87

project was to investigate the technologies on the selected bridges to objectively characterize these 88

deteriorated bridges with a university-government-industry collaboration, by exploring the use of novel 89

image based technologies in a way that the information generated through these technologies will provide 90

useful data for the inspection and evaluation of civil infrastructure systems. 91

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2. The pilot Project 93

On March 8-14, 2014, a condition assessment project was performed at Bridge #770054 (Lake Jessup 94

Bridge) carrying SR417 for the purpose of evaluating the capabilities of the digital imaging and infrared (IR) 95

technology by determining condition states for concrete bridge elements. The total length of the bridge is 96

approximately 1.5 miles (Fig.2). Both north bound and south bound lanes, supported by prestressed I-shaped 97

beams and reinforced concrete deck were scanned and analyzed. In this study, a sophisticated IR camera was 98

used, which is currently used in industry for delamination detection. The Infrared camera (FLIR 5600) has 99

the shutter speed of 1/1400, enabling the bridge deck scanning team to drive 50mph while collecting the high 100

quality IR images for analysis (where the conventional IR inspection uses lower standard IR camera with 101

only 1/125 shutter speed). The uncooled detector which is used in the conventional IR inspection works by 102

the change of resistance, voltage or current when heated by infrared radiation, thus requiring longer exposure 103

time to take the IR image. In this study, raw infrared images were further analyzed based on algorithm 104

developed and tested in Japan on many bridges. The proprietary IR software applied in this project can 105

classify the damage rate into three categories; the classification categories being “Critical” (crack caused by 106

delamination reaches on concrete surface and immediate attention is required), “Caution” (crack exists 107

within 2cm from the concrete surface and close monitoring is recommended) and “Indication” (Currently 108

satisfactory) (see Fig.3). Raw infrared (IR) image data is filtered and rated into three categories by the 109

software to indicate and evaluate the severity of the subsurface defects in concrete structures. 110

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112 Fig.2 Location of the lake Jessup Bridge 113

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Fig.3: Damage Rating by Infrared Imagery Software 127

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3. Digital image and IR scanning for the deck top 129

Digital images for the deck top were collected from a moving vehicle in the morning of Sunday, March 9th 130

(Fig.4). The deck top surface was scanned at a speed of approximately 50mph (80km/h). Two line cameras 131

were attached to the aluminum frame which was designed, manufactured and mounted on top of the vehicle. 132

Infrared (IR) images for the deck top were collected from a moving vehicle at 10:30pm-11:30pm of Sunday, 133

March 9th. The IR images were also recorded at a speed of approximately 50mph (80km/h).No lane closure 134

of any kind was required during the field data collection. The collected images have been processed and 135

analyzed by the digital imaging and IR software. Widths of the cracks were evaluated by comparing the 136

magnified digital image with the electronic crack width ruler on the computer screen (Fig.5). Table 1 137

describes the four condition states defined in the AASHTO Guide Manual for Bridge Element Inspection 138

(AASHTO, 2013 [4]). The element condition state (CS) for reinforced concrete deck (Element #12) was 139

determined from the results of deck top scanning based on the area of delamination or spall, exposed rebar 140

condition and cracking. 141

Line Camera

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Fig.4: Digital image scanning for deck top from a moving vehicle 158

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Fig.5: The electronic crack width ruler on the computer screen 174

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Table 1: Standard Condition States for Defects in Bridge Elements (after AASHTO, 2013) 176

Condition State (CS) # Condition State

1 Good

2 Fair

3 Poor

4 Severe

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Fig.6 depicts typical delaminated areas found on the deck surface. This type of cracking and delamination 179

were found at some of the joints throughout the entire bridge deck. These delaminated areas were detected 180

by digital image and IR scanning results, and hatched in yellow (for CS2: Fair) or red (for CS3: Poor) 181

depending on their size. According to AASHTO manual [4], areas of delamination or spall with 6 in. or less 182

in diameter should be evaluated as ‘CS2: Fair’, while those areas of greater than 6 in. diameter or areas with 183

unsound patch should be evaluated as ‘CS3: Poor’. The hatched areas were automatically summarized by the 184

software to calculate the quantity of deck surface with each condition state. Fig.7 depicts the typical cracking 185

found on the deck surface. The spacing of the crack was less than 1.0ft, and these cracking areas were 186

evaluated as ‘CS3: Poor’. Fig.8 is an example of IR scanning results successfully detecting the spall on the 187

deck surface. These spalls were less than 6 in. in diameter and were evaluated as ‘CS2: Fair’. 188

Table 2 is an example of element level inspection summary for the south bound bridge. The area of each 189

condition state was also summarized for each span/lane of the bridge deck. Fig.9 is a graphical presentation 190

for element level condition state distribution for each span of the south bound bridge. This kind of 191

information can be a quantitative parameter for the bridge owner to monitor the overall deck condition over 192

time and to prioritize future repair/rehabilitation programs. 193

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Fig.6: Typical delaminated areas on the deck surface (near the joint area) 208

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Fig.7: Typical cracking on the deck surface (hairline cracks with narrow spacing) 224

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Fig.8: Typical spall found on the deck top 245

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Table 2: Condition state summary for #12 Reinforced Concrete Bridge Deck (south bound) 247 248

Element

Number

Element

Description

Unit of

Measure

Total

Quantity

Condition

State 1

Condition

State 2

Condition

State 3

Condition

State 4

12

Reinforced

Concrete

Deck

ft

2

317,520

(100.0%)

317,266

(99.9%)

119

(0.0%)

135

(0.0%)

0

(0.0%)

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Fig.9: Element condition state distribution (south bound bridge deck) 265

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4. Digital image and IR scanning from the sides of the bridge 267

Digital video images for the sides of the bridges were recorded by three high definition video cameras from a 268

pontoon boat on Tuesday, March 11th at approximately 5 knots (5.74mph) (Fig.10). Both faces of the north 269

bound and the south bound bridges were scanned from a distance of 40 feet, and it took about thirty (30) 270

minutes for scanning each face of the entire bridge. The video image includes 30 frames of still images per 271

second, and these images were stitched with each other to generate a high resolution digital image for the 272

entire face of the prestressed concrete beams and reinforced concrete bridge railings. IR images for the sides 273

of the bridge were obtained from a pontoon boat at 10:00pm to 12 midnight of Tuesday, March 11th at 274

approximately 5 knots (5.74mph). The recorded movie images by three high definition video cameras were 275

used to find the indications on the concrete surface such as cracks, efflorescence and spalls. The element 276

condition state (CS) for reinforced concrete bridge railings (Element #331) and prestressed concrete beams 277

(Element #109) were determined based on the delamination or spall, exposed rebar condition and cracking 278

(AASHTO, 2013 [4]). 279

The reinforced concrete bridge railings show some cracks with efflorescence, coupled with possible 280

delaminated areas adjacent to the cracks (Fig.11). The existence of delaminated areas was detected by IR 281

scanning. Areas including cracks with minor delamination and/or efflorescence should be evaluated as ‘CS2’ 282

based on the criteria in AASHTO Manual. Table 3 is an example of element level inspection quantity 283

summary for the bridge railings for west face of the south bound bridge. The length of the bridge railing in 284

each condition state can also be summarized for each span of the bridge. Fig.12 is a graphical presentation 285

for element level condition state distribution for each span of the west face of the south bound bridge. The 286

percentage of linear footages in bridge railings in ‘CS2’ varies for each span, and this information can be a 287

quantitative parameter for the bridge owner to monitor the overall condition for bridge railings over time and 288

to prioritize the repair/rehabilitation program. 289

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Fig.10: Digital image scanning from a pontoon boat 305

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Fig.11: Typical cracks with delamination on the reinforced concrete bridge railing 318

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Table 3: Condition state summary for Bridge Railings (South bound, West Face) 320

Element

Number

Element

Description

Unit of

Measure

Total

Quantity

Condition

State 1

Condition

State 2

Condition

State 3

Condition

State 4

331 Reinforced

Concrete

Bridge Railing ft

7,938

(100.0%)

7,629

(96.1%)

133

(1.7%)

0

(0.0%)

0

(0.0%)

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331

332

333

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(Cracks w/ efflorescence and/or delamination) 337

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Fig.12: Element level condition state distribution for reinforced concrete bridge railings 339

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On the other hand, no significant cracks/delaminations were found in the outer faces of the prestressed 341

concrete beams except for some minor spall and cracking at the end of the beam (Fig.13). Sections including 342

minor cracks and delamination should be evaluated as ‘CS2’ based on the condition state criteria defined in 343

the AASHTO Manual. Based on the information obtained by digital image and IR scanning, condition state 344

for element ‘#109 Prestressed Concrete Girders/Beams’ for the Lake Jessup Bridge was summarized. Table 4 345

is an example of an element level inspection quantity summary for the prestressed concrete beam for the 346

west face of the south bound bridge. The length of each condition state for prestressed concrete beams was 347

also summarized for each span of the bridge. Fig.14 is a graphical presentation for element level condition 348

state distributions for each span of the beam of the west face of the south bound bridge. The percentage of 349

beams in ‘CS2’ (depicted in yellow color) varies for each span, and this information can be a quantitative 350

parameter for the bridge owner to monitor the overall condition for prestressed concrete beams over time and 351

to prioritize the repair /rehabilitation programs. Fig.15 is an example stitched image and IR scanning results for 352

the west face of Span 7 (Bent 84- Bent 85) of the north bound bridge. AASHTO condition state distribution for 353

reinforced concrete bridge railing and prestressed concrete beam are also shown in Fig.15. 354

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Fig.13: Typical cracking and spalls at the prestressed concrete beams 368

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Table 4: Condition state summary for #109 Prestressed Concrete Girders/Beams 370

Element

Number

Element

Description

Unit of

Measure

Total

Quantity

Condition

State 1

Condition

State 2

Condition

State 3

Condition

State 4

109

Prestressed

Concrete

Girders/Beams

ft 7,938

(100.0%)

7,755

(97.7%)

6.5

(0.1%)

0

(0.0%)

0

0.0%

371

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Fig.14: Element condition state distribution for prestressed concrete beams 388

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Fig.15: Example of Digital image, IR thermography image and software output 410

5. Summary and Conclusions 411

The full scan and analysis of Bridge #770054 (Lake Jessup Bridge) resulted in the discovery of only 412

nominal delaminations and spalls. All findings were categorized and defined based on AASHTO’s 413

guideline for bridge elements. By utilizing the imaging and IR technology at high speeds, what would 414

have taken perhaps weeks traditionally was accomplished in a matter of days. Not only was the data 415

taken rapidly, but it proved to be accurate to a degree which more than satisfied AASHTO standards for 416

crack width, spacing, and length, as well as area of delamination. This information can be easily stored 417

and referenced for future repair and rehabilitation. 418

The deck showed frequent cracking and delamination around the joints: very rarely were they observed 419

elsewhere. Some other areas showed signs of very fine groups of cracks, especially towards the south 420

end of both northbound and southbound sides. The barrier or railing showed very little sign of wear, 421

save a few thin vertical cracks. The prestressed concrete beams were also sound. When reviewing the 422

bridge during future examinations, the cracks near joints and the groups of cracks observed in Bent 60-423

91 (southbound) and 1-30 (northbound) should be closely monitored for consideration of future repair. 424

Objective condition assessment can contribute information to make better decisions for safety and 425

serviceability of roadway bridges. Understanding the real, as-is condition of the structure is important to 426

better plan and prioritize maintenance activities, to make operational decisions and to assure the highest 427

level of safety at the lowest cost. Applying more efficient methods of collecting and managing data is 428

becoming more and more critical, especially in the face of the growing amount of aging and degrading 429

bridges across the country. Also, increasing government regulations pose a need for effective record 430

keeping and continued observation. Technologies described in this paper demonstrate significant time 431

and cost reduction for bridge owners. 432

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References 434

[1] Washer, G.A., Fenwick, R.G., Bolleni,N.K., and Harper, J. (2009), “Effects of Environmental 435

Variables on the Infrared Imaging of Subsurface Features in Concrete Bridges,” Transportation 436

Research Record 2108: Journal of the Transportation Research Board, Washington, D.C., pp. 437

107-114. 438

[2] Washer, G., Bolleni, N.K., Fenwick, R.(2010), “Thermographic Imaging of Subsurface 439

Deterioration in Concrete Bridges,” Transportation Research Record: Journal of the 440

Transportation Research Board, No. 2201Washington, D.C., pp. 27-33. 441

[3] Matsumoto, M., Mitani, K. and Catbas, F. (2013): Bridge Assessment Methods Using Image 442

Processing and Infrared Thermography Technology: On-Site Pilot Application in Florida. 443

Compendium of Papers of the 92nd Annual Meeting of the Transportation Research Board. 444

Transportation Research Board, National Research Council, Washington, DC. 445

[4] AASHTO (The American Association of State Highway and Transportation Officials) (2013): 446

Manual for Bridge Element Inspection, First Edition 447

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