<p>Nondestructive detection and monitoring of stress in concrete structural members is highly coveted. Yet, there are still no efficient techniques capable of achieving that goal. The development of such a technique would improve a wide range of tasks in the construction industry, such as building quality control, condition assessment for structural rehabilitation, and prestress losses monitoring, among others. The leading approach towards this goal has been based on acoustoelasticity, the relationship between mechanical properties, such as wave propagation velocity, and the stress state of the solid medium. In concrete materials, acoustoelasticity and its applications have been increasingly studied during the past decades, mainly using wave propagation phenomena, and usually in small samples of plain concrete -without steel reinforcement- axially loaded. A few recent studies have shown that resonance vibration can also identify the acoustoelastic behavior, where frequency of vibration increases as axial stress increases, offering several benefits in contrast to the wave propagation technique. In this study, we tested a real-size reinforced concrete column of cross section 20 cm x 20 cm and 2.00 m long. The column is part of a larger concrete structure, composed of 13 cm thick slab, supported by nine columns founded on a 13 cm slab. We tested the central column of the structure, by applying three cycles of controlled compressive axial load, varying from 0 to 4 MPa in steps of 0.6 MPa, and measuring the axial strain and the fundamental torsional frequency of vibration at each loading step. Results show that the frequencies of vibration and applied compression are positively correlated. This confirms the existence of a dominant acoustoelastic behavior due to the material nonlinearity; moreover, there is very good repeatability among cycles indicating an elastic dominant behavior. Finally, results display an interesting characteristic, where the slope of the frequency vs. strain relationship gradually decreases. This behavior could indicate a change of concavity in the stress-strain relationship, by leaving the hardening phase to enter a linear one. This study is an important step forward on the path to understanding and implementing an NDT technique for stress monitoring of real concrete structures.</p>

Stress Monitoring in a Real-Size Reinforced Concrete Column Using Torsional Resonance

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.