• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.122-128
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• 2009

In this study, damage detection method using harmony search method and frequency response is proposed. In order to verify this method, the following approaches are implemented. Firstly, damage detection method using harmony search was developed. To detect damage, objective functions that minimize difference with natural frequency and modal strain energy from undamaged and damaged model are used. Secondly, efficiency of developed damage detection method was verified by damage detection of beam structure. And results of harmony search and micro genetic algorithm are compared and evaluated. Thirdly, numerical model was implemented for harbor caisson structure and damage scenario was determined. Lastly, damage detection was performed by proposed method and utility of proposed method is verified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1223-1228
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• 2006

This paper presents an experimental investigation of a recently developed Kronecker Product (KP) method to determine the type, location, and intensity of structural damage from an identified state-space model of the system. Although this inverse problem appears to be highly nonlinear, the system mass, stiffness, and damping matrices are identified through a series of transformations, and with the aid of the Kronecker product, only linear operations are involved in the process. Since a state-space model can be identified directly from input-output data, an initial finite element model and/or model updating are not required. The test structure is a two-degree-of-freedom torsional system in which mass and stiffness are arbitrarily adjustable to simulate various conditions of structural damage. This simple apparatus demonstrates the capability of the damage detection method by not only identifying the location and the extent of the damage, but also differentiating the nature of the damage. The potential applicability of the KP method for structural damage identification is confirmed by laboratory test.

• Journal of Cadastre & Land InformatiX
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• v.50 no.2
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• pp.81-100
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• 2020

The purpose of this study was to propose applicability of spatial data and quality check criteria for estimating damage from storm and flood. Using the data from the National Disaster Management System and National Spatial Data Infrastructure, spatial database for estimation of storm and flood damage has been mapped to each type of damage. This was proposed as the quality check criteria for damage analysis. Through this study, it is possible to utilize the spatial database for estimating storm and flood damage. The reliability of analysis results are ensured through the quality check criteria.

• Journal of KIBIM
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• v.10 no.2
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• pp.21-28
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• 2020

As the number of aging bridges increases, more studies are being conducted on developing effective and reliable methods for the assessment and maintenance of bridges. With the advancement in new sensing systems and data learning techniques through AI technology, there is growing interests in how to evaluate bridges using these advanced techniques. This paper presents a CNN(Convolution Neural Network) deep learning based technique for evaluating the damage existence and for estimating the damage location in PSC bridges using static strain data. Simulation studies were conducted to investigate the proposed method with error analysis. Damage was simulated as the reduction in the stiffness of a finite element. A data learning model was constructed by applying the CNN technique as a type of deep learning. The damage status and its location were estimated using data set built through simulation. It was assumed that the strain gauges were installed in a regular interval under the PSC bridge girders. In order to increase the accuracy in evaluating damage, the squared error between the intact and measured strains are computed and applied for training the data model. Considering the damage occurring near the supports, the results of error analysis were compared according to whether strain data near the supports were included.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.71-75
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• 2005

For the damage tolerance improvement of conventional laminated composites, stitching process have been utilized for providing through-thickness reinforcements. 2D preforms were stacked with S-2 glass plain weave and S-2 glass MWK (Multi-axial Warp Knit) L type. 3D preforms were fabricated using the stitching process. All composite samples were fabricated by RTM (Resin Transfer Molding) process. To examine the damage resistance performance the low speed drop weight impact test has been carried out. For the assessment of damage after the impact loading, specimens were examined by scanning image. CAI (Compressive After Impact) tests were also conducted to evaluate residual compressive strength. Compared with 2D composites, the damage area of 3D composites was reduced by 20-30% and the CAI strength showed 5-10% improvement.

• Computers and Concrete
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• v.7 no.4
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• pp.285-301
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• 2010

In this work we first review the statistical data on large fires in urban areas, presenting a detailed list of causes of fires, the type of damage to concrete and reinforced concrete structures. We also present the modern experimental approach for studying the fire-resistance of different structural components, along with the role of numerical modeling to provide more detailed information on quantifying the temperature and heat flux fields. In the last part of this work we provide the refined models for assessment of fire-induced damage in structures built of concrete and/or reinforced-concrete. We show that the refined models of this kind are needed to provide a more thorough explanation of damage and to complete the damage assessment and post-fire evaluations.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.264-267
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• 2005

Impact damages are very important in the perspective of residual strength of composite structures such as aircrafts, ships, and trains because those damages are sometimes not visible on the surface of the point of impact and the impact resistance of laminated composites is usually not so high. Thus, the impact characteristics of laminated composites should he investigated for the safety of composite structures. This paper investigates the low-velocity impact and damage detection conducted on woven carbon/epoxy laminates. Experimental results show that the type of damage is dependent on the impact energy level and the delamination area becomes larger as the impact energy increases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.494-497
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• 2001

Identification of damage of structures has recently received considerable attention in the light of maintenance and safety assessment. In this respect, the vibration characteristics of buildings have been applied steadily to obtain a damage index of the whole building, but it cannot be established as a practical method until now. A practical method for the estimation of structural damage using the first natural frequency and mode shape of building is proposed in this paper. The effectiveness of the proposed method is verified by numerical and experimental tests. From the results, it is observed that severity and location of damage can be estimated with a relatively small error by using modal properties of building.

• Structural Monitoring and Maintenance
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• v.4 no.3
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• pp.269-299
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• 2017

This paper presents a Level III damage evaluation methodology, which simultaneously, identifies the location, the extent, and the severity of stiffness damage in deep beams. Deep beams are structural elements with relatively high aspect (depth-to-length) ratios whose response are no longer based on the simplified Euler-Bernoulli theory. The proposed methodology is developed on the bases of the force-displacement relations of the Timoshenko beam theory and the concept of invariant stress resultants, which states that the net internal force existing at any cross-section of the beam is not affected by the inflicted damage, provided that the external loadings in the undamaged and damaged beams are identical. Irrespective of the aspect ratios, local changes in both the flexural and the shear stiffnesses of beam-type structures may be detected using the approach presented in this paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.608-613
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• 2003

In this paper, the variability of modal properties caused by temperature effects is assessed to adjust modal data used for frequency-based damage detection in plate-girder bridges. First, experiments on model plate-girder bridges are described. Next, the relationship between temperature and natural frequencies is assessed and a set of empirical frequency-correction formula are analyzed for the test structure. Finally, a frequency-eased method is used to locate and estimate severity of damage in the test structure using experimental modal data which are adjusted by the frequency-correction formula. Here, local damage in beam-type structures is detected by using measured frequencies and analytical mode shapes.