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Proceedings Paper

Demonstration of dual-band infrared thermal imaging at Grass Valley Creek Bridges
Author(s): Nancy DelGrande; Philip F. Durbin; Clinton M. Logan; Dwight E. Perkins; Paul C. Schaich
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Paper Abstract

We demonstrated dual-band infrared (DBIR) thermal imaging at the Grass Valley Creek Bridges near Redding, CA. DBIR thermal imaging is an enabling technology for rapid, reliable, bridge deck inspections while minimizing lane closures. The bridge-deck inspections were conducted from a mobile DBIR bridge inspection laboratory during November 2- 3, 1995. We drove this self-contained unit at limited highway speeds over 0.4 lane miles of bridge deck. Using two thermal IR bands, we distinguished delaminations from clutter. Clutter, or unwanted thermal detail, occurs from foreign materials or uneven shade on the bridge deck surface. By mapping the DBIR spectral-response differences at 3-5 micrometers and 8-12 micrometers , we removed foreign material clutter. By mapping the deck diurnal thermal inertia variations, we removed clutter from uneven shade. Thermal inertia is a bulk deck property, the square root of thermal conductivity X density X heat capacity. Delaminated decks have below-average thermal inertias, or above-average day-night temperature excursions. Compared to normal deck areas, delaminated deck areas were typically 2 or 3 degrees C warmer at noon, and 0.5 degrees C cooler at night. The mobile DBIR bridge inspection laboratory is currently undergoing extensive testing to examine bridges by the Federal Highway Administration.

Paper Details

Date Published: 13 November 1996
PDF: 12 pages
Proc. SPIE 2946, Nondestructive Evaluation of Bridges and Highways, (13 November 1996); doi: 10.1117/12.259134
Show Author Affiliations
Nancy DelGrande, Lawrence Livermore National Lab. (United States)
Philip F. Durbin, Lawrence Livermore National Lab. (United States)
Clinton M. Logan, Lawrence Livermore National Lab. (United States)
Dwight E. Perkins, Lawrence Livermore National Lab. (United States)
Paul C. Schaich, Lawrence Livermore National Lab. (United States)


Published in SPIE Proceedings Vol. 2946:
Nondestructive Evaluation of Bridges and Highways
Steven B. Chase, Editor(s)

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