00748758

Monograph

http://onlinepubs.trb.org.../NCHRP024_Final_Report.pdf

This Innovations Deserving Exploratory Analysis (IDEA) project investigated the feasibility of a fiber-optic (FO) strain sensor system for long-term monitoring of highway structures. The principle of operation relies upon measuring the time-of-flight of an optical signal's propagation through an optical fiber and then converting it to mechanical strain. By segmenting an optical fiber string with optical reflectors, the strain of in-line segments can be determined separately. This method enables strain mapping of an entire structure with a finite-element sensor grid and is capable of detecting localized damage such as cracking and stress corrosion. The monitoring system includes a custom-built high-resolution optical time domain reflectometer (OTDR), dedicated FO data acquisition (FODAC) software, and novel FO strain gauge patches (FOSGPs), which allow monitoring of integral strain in large structures. The FOSGPs are flexible sensor patches that can be embedded in or attached to the structure to be monitored. The FOSGPs were developed and design parameters were optimized. Data acquisition software was also developed. Steel and composite coupons with attached or embedded FOSGPs were tested for strain. Results showed that using latest OTDR, the FOSGP sensors achieved a resolution of 0.01% strain and could resolve tensile strain in reinforced concrete just before the failure due to fracture. The data also suggest that FOSGP sensors will be most successful at detecting strain in concrete structures if placed in compression locations.

This NCHRP-IDEA investigation was conducted by Simula Government Products, Inc., Tempe, Arizona. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved

NCHRP-IDEA Project 24

NCHRP-24

English

32 p.

1997-9

NCHRP-IDEA Program Project Final Report

Figures (22) ; Photos (7) ; Tables (4)

Data collection; Defects; Detection and identification; Detectors; Fiber optics; Fracture mechanics; Monitoring; Patching; Reinforced concrete; Sensors; Software; Strain (Mechanics); Strain gages; Stress corrosion; Structures; Technological innovations; Tension; Time domain reflectometers; Time duration

National Cooperative Highway Research Program

Long term; Structural damage

Bridges and other structures; Design; Highways; I24: Design of Bridges and Retaining Walls

TRIS, TRB

May 19 2001 12:00AM