Coda Wave Interferometry Method Applied in Structural Monitoring to Assess Damage Evolution in Masonry and Concrete Structures

Abstract

In this experimental program the main goal is to monitor the damage evolution in masonry and concrete structures by Acoustic Emission (AE) signal analysis applying a wellknow seismic method. For this reason the concept of the coda wave interferometry is applied to AE signal recorded during the tests. Acoustic Emission (AE) are very effective non-destructive techniques applied to identify micro and macro-defects and their temporal evolution in several materials. This technique permits to estimate the velocity of ultrasound waves propagation and the amount of energy released during fracture propagation to obtain information on the criticality of the ongoing process. By means of AE monitoring, an experimental analysis on a set of reinforced masonry walls under variable amplitude loading and strengthening reinforced concrete (RC) beams under monotonic static load has been carried out. In the reinforced masonry wall, cyclic fatigue stress has been applied to accelerate the static creep and to forecast the corresponding creep behaviour of masonry under static long-time loading. During the tests, the evaluation of fracture growth is monitored by coda wave interferometry which represents a novel approach in structural monitoring based on AE relative change velocity of coda signal. In general, the sensitivity of coda waves has been used to estimate velocity changes in fault zones, in volcanoes, in a mining environment, and in ultrasound experiments. This method uses multiple scattered waves, which travelled through the material along numerous paths, to infer tiny temporal changes in the wave velocity. The applied method has the potential to be used as a "damage-gauge" for monitoring velocity changes as a sign of damage evolution into masonry and concrete structures.

Correlation of Load-Bearing Behavior of Reinforced Concrete Members and Velocity Changes of Coda Waves

“…The coda is scattered several times and thus interacts with larger regions. It is known to be sensitive to small changes in mechanical strain (compressive and tensile) [9][10][11][12][13][14][15], temperature [16][17][18], moisture [19][20][21] as well as cracks or other discontinuities in the concrete [22][23][24][25][26]. Since strain is the fundamental state variable of RC [27]; it seems most promising to establish a direct correlation between it and the coda to infer the health of structures.…”

Fatigue Analysis of FRP Strengthened Masonry by Acoustic Emission Monitoring

“…Therefore the masonry reinforced with this composite material has not undergone any mechanical resistance decay after the fatigue tests. On the contrary, as happened in the previous experiments, the reinforced specimens with reinforced plaster has shown lower resistances if subjected to preventive fatigue test [17,18].…”

Early-age concrete strength development monitoring using piezoelectric self-emission and detection (SED) and coda wave energy (CWE)

“…Coda wave has found research in the field of nondestructive testing and structural health monitoring. Examples include using the change of velocity which is extracted from the coda wave to study the properties of the rock [45,46], evaluating the bolt connection status by the coda wave energy (CWE) [43], studying the bridge load by the ultrasonic coda wave interference technology [47], and evaluating the structural damage of concrete by the coda wave analysis method [48]. Because of the high sensitivity of coda wave to structural property changes, we expect coda wave can be used to monitor the concrete hydration process.…”