Message Board Thread - "Infrared Thermography and Bridges structures "

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Infrared Thermography and Bridges structures thermoimagen 3/7/2004
How come some termographers inspect bridges Structres?.. are they looking for something in special or just want to keep reference for future?..
It is possible that any mechanical distorsion produce enough heat to detect?..

Re:Infrared Thermography and Bridges structures Gary Orlove 3/10/2004
Here are some references to look at:

D4788-03 Standard Test Method for Detecting Delaminations in Bridge Decks Using Infrared Thermography
This test method covers the determination of delaminations in portland-cement concrete bridge decks using infrared thermography. This test method is intended for use on exposed and overlaid concrete bridge decks.

Infrared Thermography, or thermal imaging as it is sometimes known, provides a cost effective and accurate method of detecting delamination and debonding in concrete structures. It works because the delaminations or voids are filled with air or water, each of which has a different density and thermal conductivity to the surrounding concrete.

The use of Infrared Thermography is based on the poor thermal conductivity of concrete. This characteristic of concrete is such that on a sunny day, significant temperature differences exist throughout the pavement. Consequently, any discontinuity parallel to the surface inhibits the transfer of heat to the concrete.

This paper explores the possibility of detecting geometrical defects in concrete specimens using thermal imaging. The method is based on the characteristics of heat flow phenomenon, in a conductive medium of specific geometry, which is intended to model predetermined boundary conditions. A range of crack widths, representing mechanical damage, has been induced under controlled laboratory conditions. In all cases the cracks have been located successfully.

Nondestructive Evaluation of Bridges and Highways

Infrared thermography has the potential to size defects, to evaluate the quality of the adhesive bonds remotely and to cover a large area per scan. In this paper, a feasibility study was carried out to evaluate bonded and hollow areas between tile and concrete substrate. A locked-in thermography system was used. The study shows that there is a distinct difference in thermographic phase patterns. This is a possibility of using this technique when there is complete disbond (hollow area) between tile and concrete substrate.

Gary Orlove
Infrared Training Center

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