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

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 leading approach towards this goal has been based on acoustoelasticity, the relationship between mechanical properties, such as mechanical wave speed, and the stress state of the solid medium. In concrete materials, acoustoelasticity has been increasingly studied, mainly using wave propagation phenomena, and usually in small samples of plain concrete — without steel reinforcement — axially loaded. A less studied approach involves the use of resonance phenomena, which offers other benefits. In this study, we tested a real-size reinforced concrete column of cross section 20 cm × 20 cm and 2 m long, by applying three cycles of controlled compressive axial load, varying from 0 to 4 MPa, and measuring axial strains and torsional frequencies of vibration. Repeatable results show that the frequencies of vibration and applied compression are positively correlated. indicating a dominant elastic behavior. This study is an important step forward on the path to understanding and implementing a nondestructive technique for stress monitoring of real concrete structures.