Enhancing Structural Integrity Assessment Through Non-Destructive Evaluation

Area of Science:

• Civil Engineering
• Materials Science
• Geophysics

Background:

• Non-destructive testing (NDT) is crucial for assessing the condition of existing concrete structures.
• Accurate determination of reinforcement bar (rebar) size and depth is essential for structural integrity evaluation.
• Ground-penetrating radar (GPR) is a widely used NDT technique, but precise rebar characterization remains challenging.

Purpose of the Study:

• To develop and validate an amplitude-based GPR approach for estimating rebar diameter in reinforced concrete.
• To introduce normalized amplitude-diameter-depth (NADD) relationships for improved GPR data interpretation.
• To enhance the reliability of GPR for evaluating reinforcement characteristics in existing structures.

Main Methods:

• Utilized an amplitude-based non-destructive testing (NDT) approach with ground-penetrating radar (GPR).
• Developed normalized amplitude-diameter-depth (NADD) relationships using an exponential attenuation model.
• Normalized GPR signal amplitudes to account for signal energy and antenna coupling variations.
• Validated the NADD model on a reinforced concrete slab and subsequently on prestressed concrete box beams from a decommissioned bridge.

Main Results:

• The NADD approach effectively links reflected GPR wave amplitude to rebar diameter and cover depth.
• Normalization improved the consistency of amplitude-depth interpretation across different depths.
• The model achieved a minimum mean prediction error of approximately 4.7% for 12.7 mm (#4) rebar.
• Demonstrated the quantitative framework's capability in accurately evaluating reinforcement characteristics.

Conclusions:

• The proposed normalization-based GPR method provides a reliable way to estimate rebar diameter.
• The NADD relationships offer a quantitative framework for interpreting GPR data in structural health monitoring.
• This technique enhances the evaluation of reinforcement in existing concrete structures, contributing to improved infrastructure management.