Use of Thermography for Bridge Inspection. Glenn A. Washer, Ph.D University of Missouri

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1 Use of Thermography for Bridge Inspection Glenn A. Washer, Ph.D University of Missouri

2 Agenda Goals and Objectives Background Research Field examples Conclusions

3 Goals and Objective Pooled fund TPF-5(152) (Phase 1) Goal: Improve technology and methods for the condition assessment of civil infrastructure Objectives: Develop thermal imaging technology for detecting subsurface damage in concrete Provide a practical tool for routine inspection and maintenance Pooled fund research allows state Departments of Transportation to pool research funding to work on common problems

4 TPF-5(247) States

5 The Objectives of this project: Using new cameras, test operational parameters with DOT personnel on actual bridge inspections Collect data and upload results to a database Conduct periodic interviews to determine improvements / modifications in use procedures to optimize value Disseminate findings among participating states on an on-going basis In parallel with field operations, conduct verification testing, modify the guidelines and conduct lab investigations Analyze field data, integrate lab data, and develop a recommended practice that instructs DOT personnel on how to best apply the cameras in the field 5

6 Motivations for Using IR Camera ABC Chicago

7 Motivation

8 Risk of Soffit Damage OKLAHOMA CITY (AP) In 2004, a footballsized piece of concrete fell from a bridge and crashed through Yvonna Osborn's windshield while she was driving home on Interstate 35. State inspectors to examine bridge where concrete fell Posted: 02/01/ :50 AM

9 IR Thermography Instruments Shorter wavelengths High frequency Longer wavelengths Low frequency Typical components of an IR thermography

Basic Principles of IR Thermography Subsurface delaminations create perturbation in heat transfer through the concrete [http://www.flir.com/thermography/ americas/us/content/?

10 Basic Principles of IR Thermography Subsurface delaminations create perturbation in heat transfer through the concrete [ americas/us/content/?id=36667] Thermal Image of surface temperature Thermal response of delaminations in concrete: (A) day time condition; (B) night time condition; (C) surface temperature and thermal contrast as a function of time

Research The detection of the subsurface

the day Warming in the daytime, cooling at night

11 Research The detection of the subsurface delaminations depends on the environmental conditions at the bridge Effects: Ambient Temperature Changes: Temperature variations during the day Warming in the daytime, cooling at night Wind speed: Convective heat transfer from the environment Depth of defect Solar exposure

12 3 fundamental methods of heat transfer Wind over hot concrete cools it by convection Direct sunshine on concrete heats it by radiation Heat flows through concrete by conduction Convection h T 2 T ) Q c ( 1 Conduction T A T L 2 1 Q Emission (Radiation) Q T 4 12

13 Thermal Contrast Comparison of solar exposure vs. shade THERMAL CONTRAST ( C) AmbientTemperature 1 in. 3 in. ΔT(-1") IR ( C) ΔT(-3") IR ( C) Ambient ( C) AMBIENT TEMPERATURE ( C) THERMAL CONTRAST ( C) Solar loading 1 in. 3 in. ΔT(-1") IR ( C) ΔT(-3") IR ( C) Solar (W/m²) SOLAR LOAD (W/m²) -3 07/14/ :00 4:00 8:00 12:00 16:00 20:00 0:00 Time (hh:mm) :00 4:00 8:00 12:00 16:00 20:00 0:00 TIME (hh:mm) Shady / soffit Sunny / deck

14 Shady Conditions 48 hrs

Phase I: Guidelines Sunrise 150 125 100 75 Sunset Sunrise 150 125

(mm) -75-75 -100-100 -125-125 -150-150 0:00 2:00 4:00 6:00 8:00

15 Phase I: Guidelines Sunrise Sunset Sunrise Target Depth (mm) Target Depth (mm) :00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 Inspection Period (hh:mm) 15

16 Effect of Depth and Thickness Effect of Void Depth Effect of Void Thickness The constant K The maximum thermal contrast decreased exponentially by a constant multiple of 0.98 as the void depth increased The maximum thermal contrast increased nonlinearly (as a logarithm function) with increasing thickness of the void.

17 Different Materials in Void

18 Examples from Field Testing with States

19 Soffit Example

20 Bridge Soffit Example

21 FRP 21

22 Stephen s Pedestrian Bridge 22

23 Stephen s Pedestrian Bridge B C D A E

25 A B C D

26 Under Bridge Domicile- PA

27 Hybrid Beams

28 Conclusions Main Advantage Extend the reach of the inspector Observe damage without accessing surface Relatively easy to use, real-time results Main Disadvantages Uneven performance due to Environmental conditions Variations in damage Best for <=~2 in., more limited for ~3-4 in., limit ~5 in. Best Uses A tool for the inspectors toolbox that greatly improves capability, with known limitations Detect loose concrete that could fall into roadway Rapid deck, abutment, soffit assessments

29 Questions

JOHN c. DUKE, JR., AND STEVEN c. WARFIELD

84 TRANSPORTATION RESEARCH RECORD 1347 Abridgment Evaluation of Infrared Thermography as a Means for Detecting Delaminations in Reinforced Concrete Bridge Substructure Elements JOHN c. DUKE, JR., AND STEVEN