Damage Evaluation for Railway Structures by Means of Acoustic Emission

Abstract

Sudden ground motions such as earthquakes sometimes cause serious damage in railway structures. For evaluating the structural integrity after the shock, damage condition of superstructures (or the upper part of substructures) is primarily investigated with the unaided eye. The results are basically subjective, and the structural integrity is evaluated only from the region that could be observed. Accordingly, in order to quantify the structural integrity objectively, an AE testing is tried to apply for the railway structures. In damaged concrete materials, it is known that secondary AE activity from existing defects are readily generated, and based on the Kaiser effect, damage degree could be quantified. In the monitoring of railway structures, however, except for AE signals from the defect, directly induced AE signals by the acceleration of the train passage could be detected. In the present paper, frequency characteristics of such AE signals as secondary AE signals and noise signals are elucidated through laboratory and in-situ experiments. The damage is quantified in an actual concrete pier based on the AE activity of raw AE data including noise signals, and extracted AE data generated from existing cracks, respectively. The results suggest that the quantitative evaluation of damage degree might be possible with the extracted AE activity, however, more data should be collected to classify damage degree reasonably.

Repair evaluation of concrete cracks using surface and through-transmission wave measurements

“…In addition to surface waves measurements, since there was access to both sides of the deck in the particular case described herein, measurements were conducted also using longitudinal waves through the thickness with application of tomography, a technique commonly used for evaluation of the interior of structures [7,8,26] originated from geophysics [27].…”

“…They may occur due to the combined effect of overloading, drying shrinkage, temperature variations, chemical attacks, weathering, differential settlement and other degradation processes. The most important consequence is the exposure of the metal reinforcement to environmental parameters that lead to its accelerated oxidation [1][2][3][4][5][6][7] and finally the loss of durability of the structure.…”

“…Materials with superior mechanical properties and resistance to corrosion enable different effective repair techniques. Common methods of repair include epoxy or grout injection [7][8][9][10] and surface applications of fiber reinforced polymer strips [10].…”

Characterization of surface crack depth and repair evaluation using Rayleigh waves

“…Some of the reasons are overloading, weathering, drying shrinkage, differential settlement, other degradation processes or combination of the above. The major threat they pose concerns the exposure of the metal reinforcement to environmental agents leading to its oxidation [1][2][3][4][5]. To seal the cracks and protect the interior, and also provide structural strength restoration, injection of epoxy or other agents can be used [6][7][8].…”

Parameter Analysis

“…When comparing with seismic b-value, the Ibvalue shall be multiplied by 20. The Ib-value has successfully been applied to evaluate developing process of fracture in such fields as soil (Shiotani & Ohtsu 1999), rock (Shiotani, Ohtsu et al 1998;Shiotani, Kumagai et al 2004), and concrete (Shiotani, Li et al, 2001;Shiotani, Bisschop et al, 2003;Shiotani, Nakanishi et al 2006). …”