Demonstration of dual-band infrared thermal imaging at Grass Valley Creek Bridges

Nancy DelGrande; Philip F. Durbin; Clinton M. Logan; Dwight E. Perkins; Paul C. Schaich

doi:10.1117/12.259134

13 November 1996 Demonstration of dual-band infrared thermal imaging at Grass Valley Creek Bridges

Nancy DelGrande, Philip F. Durbin, Clinton M. Logan, Dwight E. Perkins, Paul C. Schaich

Proceedings Volume 2946, Nondestructive Evaluation of Bridges and Highways; (1996) https://doi.org/10.1117/12.259134
Event: Nondestructive Evaluation Techniques for Aging Infrastructure and Manufacturing, 1996, Scottsdale, AZ, United States

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.

Citation Download Citation

Nancy DelGrande, Philip F. Durbin, Clinton M. Logan, Dwight E. Perkins, and Paul C. Schaich "Demonstration of dual-band infrared thermal imaging at Grass Valley Creek Bridges", Proc. SPIE 2946, Nondestructive Evaluation of Bridges and Highways, (13 November 1996); https://doi.org/10.1117/12.259134

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