Volume 11, Issue 3 (2011)
MCEJ 2011, 11(3): 0-0 |
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Lotfollahi-Yaghin1*, M A, Shamsai2 A, Hesari M A. Application of Stationary Wavelet Transform (SWT) to the Crack
Detection in Concrete Arch Dams by Frequency Analysis. MCEJ 2011; 11 (3)
URL: http://mcej.modares.ac.ir/article-16-10623-en.html
URL: http://mcej.modares.ac.ir/article-16-10623-en.html
Abstract: (11581 Views)
In this paper, crack detection possibility in an arch dam structure is investigated by wavelet transform
analysis. An arch dam is a solid concrete dam, curved upstream in plan. In addition to resisting part of
the pressure of the reservoir by its own weight, it obtains a large measure of stability by transmitting
the remainder of the water pressure and other loads by arch action into the canyon walls. The complete
necessity of high safety, economical design, complex of designing and its application increase the
importance of concrete arch dams. Successful arch action is dependent on a unified monolithic
structure, and special care must be taken in the construction of an arch dam to ensure that no structural
discontinuities such as open joints or cracks exist at the time the structure assumes its water load.
According to the principles of theory of structures, there is a relationship between the dynamic and
static responses and, consequently, the stiffness. Any sudden change in stiffness leads to dynamic and
static response variation. This condition will help to estimate the damage and to investigate the
structural response before and after the failure. Wavelet analysis has recently been considered for
damage detection and structural health monitoring (SHM). It provides a powerful tool to characterize
local features of a signal. The basis function in wavelet analysis is defined by two parameters: scale
and translation. This property leads to a multi-resolution representation for stationary signals. It has
high ability in analysis of static and dynamic response signals. Staionary wavelet transform (SWT) can
show the location of frequency changes. That these locations are the points that they have been
damaged.
The case study is the concrete curvature arch of KAROON-1 (Shahid Abbaspour) dam with the height
of 200 m. This dam is considered as one of the most complex dams because of different external and
internal radia and angles, as well as asymmetrical center of the external and internal archs in different
levels. Using the geometrical dimensions of the above-mentioned dam- from respective design sheetsand
its mechanical and physical properties, the dam with and without crack was modeled by the
ABAQUS FE software package. After frequency analysis of the dam by ABAQUS for both safe and
cracked models in the same frequency mode, displacement responses at the cracked level (crest) were
extracted along the reservoir’s longitudinal axis. Afterwards, the responses were used for the wavelet
analysis by the wavelet toolbar of the MATLAB software and the detection of crack in the dam
structure was investigated with SWT. The results of wavelet analysis showed that the graphs have
considerable rise at or around the crack location. But there was no noise or any harmony in the graphs
of the safe dam. Hence, detecting the location of crack in dam structures is possible with wavelet
transform.
Received: 2007/12/17 | Accepted: 2008/07/15 | Published: 2011/11/9
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