Development of a Magnetic Field Sensor System for Nondestructive Evaluation of Reinforcing Steel in Prestressed Concrete Bridge Members

Nondestructive evaluation of prestressed concrete mainly includes inspection of the condition of the prestressing strands for load rating. This thesis presents a magnetic inspection system to measure main magnetic flux (MMF) and magnetic leakage flux (MFL) signals, to evaluate the condition of prestressing stands. A proof-of-concept has been established using a prototype electromagnet-sensor, showing a direct relationship between the cross-sectional area of the strand and the magnitude of magnetic field induced in it. A field test of a box-beam bridge was conducted using both MMF and MFL detection techniques separately. This led to the realization of a comprehensive MMF-MFL electromagnet-sensor system for inspection of prestressed steel in concrete. A computer aided simulation model was created to model the magnetic field signals and aid in better understanding of the electromagnet-sensor. This model is also useful for generating expected magnetic field signals from magnetization of different strand size and configuration setups and thus, helps in making corrosion estimations. The MMF-MFL signal detection concept was evaluated using the existing electromagnet-sensor in a laboratory setup and on prestressed box-beams obtained from a demolished bridge. It was able to identify corrosion and defects such as breaks or fractures in prestressing strands. For this magnetic inspection system to become practical, certain modifications such as redesign of the magnetic field generated by the magnet to have higher resolution have been suggested. Other features such as accurate measurement of pole face to strand distance and weight reduction have been discussed. The overall outcome of this research has shown that magnetic field signals can be useful to detect hidden corrosion in prestressed box-beams.

Name thesis:degree_name

Doctor of Philosophy in Engineering

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Electrical Engineering

Grantor dc:publisher

University of Toledo

Year dc:date

2012

Author dc:creator

• Fernandes, Bertrand

Contributors dc:contributor

• Devabhaktuni, Vijay K.
• Nims, Douglas K.

• Civil Engineering
• Electrical Engineering
• Box-Beam Bridge
• Nondestructive Testing and Evaluaiton
• Prestressed Strand
• Electromagnet Sensor
• Main Magnetic Flux
• Magnetic Flux Leakage

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=toledo1352760825

OAI identifier oai:identifier

oai:etd.ohiolink.edu:toledo1352760825