01046999

Monograph

http://onlinepubs.trb.org.../NCHRP102_Final_Report.pdf

This Innovations Deserving Exploratory Analysis project developed a nondestructive method based on impact-echo and ultrasonic reflection techniques with continuous scanning features for determining the grout condition inside post-tensioned bridge ducts. Initial efforts were focused on evaluating and establishing the accuracy/reliability of the impact echo scanning test. The impact echo scanner hardware was modified by incorporating a rolling transducer into the prototype to overcome the problem of variable thickness. The scanner software was also improved to provide three-dimensional display of impact echo results. Data on a mock-up slab fabricated with defects of different types and sizes and collected using the modified instrument were analyzed. Visualization from three-dimensional surface plots helped interpret the data. The presence of a tendon duct and grouting discontinuities appeared to cause an increase in the apparent slab thickness. Two U-shaped precast bridge girders with four ducts on each wall were procured from the Colorado Department of Transportation for full-scale tests. Impact echo tests using a rolling scanner at different times after the grouting process were performed on the walls of the girders. The results showed good agreement with the actual defect design. The clearest indication of the presence of grouting defect was given by the apparent increase in slab thickness due to a reduction in the impact echo resonant frequency (caused by a decrease in stiffness associated with a detect). The equipment is now ready for field implementation and is commercially available.

This NCHRP-IDEA investigation was conducted by Olson Engineering, Inc., Wheat Ridge, Colorado. 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

TRB-NCHRP-102

English

37p

2006-12

NCHRP-IDEA Program Project Final Report

Final Report

June 2003-December 2006

Print

Figures; Photos; References (6) ; Tables (2)

Accuracy; Bridges; Crash tests; Defects; Ducts; Girders; Grout; Nondestructive tests; Prototype tests; Ultrasonic tests

Innovations Deserving Exploratory Analysis (IDEA) (Program)

Stress waves

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

TRIS, TRB

Apr 25 2007 3:07PM