• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.138-146
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• 1996

The presence of a damage, such as a crack, in a structure increases the flexibility and damping in the structure. Most of methods to detect damage or damage location uses stiffness matrix of the structural system. The modification of stiffness matrix, however, has complicated procedures to identify structural. system in the basis of finite element model and has too many degree of freedom to calculate. Identification of changes of flexibility of structure can offer damage information immediately and simple procedure can employ real time continuous monitoring system. To identify changes of the flexibility, vibration mode shapes and natural frequencies are usually used. In this paper, a procedure for damage location in continuous girder bridges using vibration data is described. The effectiveness and sensitivity of the presented method to measurement errors in mode shapes and natural frequencies are investigated using analytical results from finite element models. It is shown that the errors in the first mode shape and first natural frequency demonstrate much larger influence than those in the higher mode shapes and modal frequencies.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.04a
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• pp.43-47
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• 1991

For the structural analysis of optimum form decision of 3-D free fort structure such as ship, plane, automobile, definition of versatile forms and comparision between them satisfying the design criterion, is essential. In this paper, three dimensional free-form structure and it's variation are defined and attempts were made to obtain geometric form information for structural analysis. The validity of the method ks been tested for a particular free-form model selected.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.159-165
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• 2002

Currently structural design of basement exterior wall is based on the assumption of boundary condition of plate, which may lead to erroneous results. In this study, the behavior of basement exterior wall subject to earth pressure and hydraulic pressure is investigated using linear finite element analysis. Parametric studies are conducted to investigate the variation of moment and shear force according to column-to-wall stiffness and aspect ratios. Using these numerical results, modification factors applicable to the design of basement exterior wall are presented. Design example is illustrated, showing satisfactory results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.194-200
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• 1999

Localized damage to a structure affects its dynamic properties, and much work has been undertaken investigating the variation of natural frequencies, damping ratios and mode shapes. This paper presents a technique based on wavelet transform to detect the existences and locations of structural damages. The procedure operates solely on the mode shape from the damaged structure, and does not require a priori knowledge of the undamaged structure. The procedure is developed using a 32-story shear building model. Applying wavelet transform to the mode shape successfully identifies the location of damage. The procedure is best suited to the mode shape obtained from the fundamental natural frequency. The wavelet coefficients from the higher mode shapes can be used to verify the location of damage, but they are not as sensitive as the wavelet coefficients of the lower mode shapes.

• Computational Structural Engineering
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• v.5 no.2
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• pp.79-85
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• 1992

For the structural analysis of optimum form decision of 3-D free form structure such as ship, plane, automobile, definition of versatile forms and comparision between them satisfying the design criterion, is essential. In this paper, 3-D free form structure and it's variation are defined and attempts were made to obtain geometric form information for structural analysis. The validity of the method has been tested for a particular free model selected.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.04a
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• pp.182-189
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• 1996

The focus of this study is on the problem of the design of structure of undetermined topology. This problem has been regarded as being the most challenging of structural optimization problems, because of the difficulty of allowing topology to change. Conventional approaches break down when element sizes approach to zero, due to stiffness matrix singularity. In this study, a novel nonlinear Programming formulation of the topology Problem is developed and examined. Its main feature is the ability to account for topology variation through zero element sizes. Stiffness matrix singularity is avoided by embedding the equilibrium equations as equality constraints in the optimization problem. Although the formulation is general, two dimensional plane elasticity examples are presented. The design problem is to find minimum weight of a plane structure of fixed geometry but variable topology, subject to constraints on stress and displacement. Variables are thicknesses of finite elements, and are permitted to assume zero sizes. The examples demonstrate that the formulation is effective for finding at least a locally minimal weight.

• Journal of the Korea Society for Simulation
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• v.14 no.3
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• pp.147-154
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• 2005

In conventional approaches such as a functinal approach or a parametric approach to online signature verification, which could not deal with the local shape of signature, much various important informations inherent in the local part of signature shape have been overlooked. In this paper, we try a structural approach in which a signature is represented as a structural form of handwriting primitives and the local parts along a signature handwriting can be selectively compared according to their discrimination power in the process of signature verification, As a result, the error rate is diminished in the case that the weights of subpattern units is applied into comparing process, which is the degree of discrimination power of local part. And also, the global variation and complexity of each signature extracted from the analysis of local shape is found useful in determining the decision threshold more precisely.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.6
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• pp.727-737
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• 2010

Together with the Young's modulus the Poisson's ratio is another independent material parameter that governs the behavior of a structural system. Therefore, it is meaningful to evaluate separately the influence of the parameter on the random response of the structural system. To this end, a formulation dealing with the spatial randomness in the Poisson's ratio in laminated composite plates is proposed. The main idea of the paper is to transform the fraction form of the constitutive coefficients into the expanded form in an ascending order of the stochastic field function. To validate the adequacy of the formulation, a square plate is chosen and the computation results are compared with those obtained using conventional Monte Carlo simulation. It is observed that the results show good agreement with those by the Monte Carlo simulation(MCS).

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.643-646
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• 2004

The posttensioning system of nuclear containment have to be verified its structural integrity by the periodic inspection because the structural behavior of the containment is changed by the variation of the physical property of concrete and tendon as time passes. In this study a program 'SAPONC-CANDU' which is able to monitor and analysis the micro structural behavior of the domestic CANDU type containment at all times was developed. The readings of vibrating-wire strain gauges embedded into the concrete of containment were used as input data for operating the program. This program provides the long-term prediction values and bands of the concrete strain due to the time dependent factors of the concrete and tendon of the domestic CANDU type containment.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.129-137
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• 2000

In the prototype stage of a car developing program, the efficiency of trouble shooting is an important factor to be considered. Structural modifications by the design sensitivity analysis are applied to a steering wheel system for improving the idle vibration of the prototype passenger car. For the design sensitivity analysis, the experimental modal analysis for the steering system attached to a body-in-white is fulfilled and the modal parameters extracted from the experimental data are used to predict the effect of structural modification, The design sensitivity results rank the locations to be reinforced in terms of frequency variation. The modification of steering system according to the sensitivity analysis results shifted the resonant frequency of the system effectively. In addition, the idle test of the car after the structural modifications f steering system shows that the proposed method can reduce vibration of the steering wheel efficiently.