Abstract

Condition and health monitoring of concrete structures have experienced an increasing interest over the last decade. Many types of sensors are utilized for this purpose such as strain gages, accelerometers, displacement sensors, etc. The response of a structure to low, i.e. service-level loads can be particularly useful to capture changes over time, including accumulation of damage, changes in the load path, etc. Typically, strain gages attached to the concrete surface are utilized to measure strain and then infer stress from them. As such, these measurements represent a surface observation. In contrast, stress waves propagate through the thickness of a member and can thus interact and can detect internal changes. This study uses the ultrasonic coda wave comparison (CWC) technique to monitor minute stress changes in reinforced concrete structures due to external loads. Additionally, residual stresses can also be captured in the coda portion of the recorded ultrasonic waveforms and quantified by means of magnitude-squared coherence (MSC). Measurements from a laboratory experiment as well as an in-service bridge field test are presented and discussed in this paper. The results demonstrate that the CWC technique is able to capture minute stress changes due to lowlevel load cycles as well as provide additional information regarding residual stresses and associated potential damage.

How to Cite:

Hafiz, A. & Schumacher, T., (2019) “Capturing minute stress changes and residual stresses in structural concrete using the ultrasonic coda wave comparison technique”, Review of Progress in Quantitative Nondestructive Evaluation .