• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.48-55
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• 2002

An Internet-based software called the Repair Advisory Service (RAS) was developed to assist aircraft composite repair. The RAS takes advantage of the web user interface and provides estimation of the failure loads of repaired composite laminates and Structural Repair Manual (SRM) with search capability. In this paper, a failure model of lap repair is discussed as an example of the modules in the RAS. The model takes into account anisotropy of each ply in the laminate and in the repair ply, and non-elastic behavior of the interlayer between the laminate and the repair patch. Failure loads calculated by the model were compared with test data, and a good agreement was found between the results of the model and the test.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.191-198
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• 2005

This study was carried out to investigate quantitatively the relationship between the degree of rebar corrosion and the strength of reinforced concrete beams. After producing equations for the relationship between both the tensile properties of rebars and bond properties and the corrosion percentage of rebars, finite element analysis and bending tests were conducted for RC beams damaged by corrosion of tension main rebar. As a result, it was made that the strength of RC beams damaged by corrosion could be practically simulated by FEM analysis using experimentally determined material properties representing the bond and the mechanical characteristics of corroded rebars.

• Journal of the Society of Disaster Information
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• v.14 no.1
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• pp.43-50
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• 2018

This study presented 3D Finite Element (FE) analysis of curved beam structures subjected to static and dynamic loading conditions, which is particularly strong ground motions. It was shown that the results obtained from 3D FE analyses was similar to the theoretical solution within 1% convergency error, in order to validate the 3D solid FE models in this study. In particular, it was focusing on development of dynamic characteristics of curved beam structures subjected to three-different seismic ground motions: GyeongJu, Lomaprieta and Northridge earthquakes. Consequently, It was interesting to find that the results obtained from GyeongJu earthquake was detuned due to high frequency effect, but the Von-Mises of the curved beam structure under Lomaprieta earthquake was 647.824 MPa at 45 curvature degree.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.148-156
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• 2018

The integrity assessment of the bridge behavior is generalized by field data of a static load-deformation curve and dynamic properties such as impact factors and natural frequencies. Evaluating it with numerical analysis is a reasonable method. The results of the mockup test and the numerical analysis are corresponded with each other since the behavior of service load proceeds in elastic region. In case of the dynamic behavior of structure, especially for the analysis of vibration, the result of the mockup test differs from the result of numerical analysis a little due to the geometric shape and non-homogeneous materials. In order to converge on these tolerances, this study suggested several numerical models, analyzed the sensitivity and finally offered a practical modeling method for the estimation of bridge on the basis of the result of mockup test. Based on the model substituted concrete section for strands section, the natural frequency of the model composed with axial stiffness of strands or the model applied the modified modulus of elasticity was closest with the result of the mockup test.

• Magazine of the Korea Concrete Institute
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• v.7 no.1
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• pp.145-155
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• 1995

The purpose of this paper is to present an analysis method which can exactly analyze load-deflection relationships. crack propagations and stresses and strains of steel reinforccnlent and concrete in hehaviors of elastic, mclastic and ultlmate ranges of reinforced concretc beams under monotonically increasing loads. For these purposes, the material nonlinearities are taken into account by comprising the tension. compression and shear models of cracked concrete and a model for reinforcement in the concrete. Smeared crack model is used as a modeling of concrete. The steel reinforcement is assumed to be in an uniaxial stress state and modeled srncaretl layers of eqivalent thickness and line elernents for correct positiori arid behavior. For the verification of application and validity of the method proposed in this paper, several numerical examples are analyzed and compared with those from other researchers. As a results, this method shown in 3.5-15(%) error is correct.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.625-632
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• 2008

In the companion paper (Model Development), an analytical model estimating the available rotation capacity of fully restrained beam-column connections in special steel moment-resisting frames was proposed. In this paper, two limit states were considered as the connection rotation capacity criteria: (i) strength degradation failure when the strength falls below the nominal plastic strength due to the local buckling of the beam's cross-section and (ii) low-cycle fatigue fracture caused by plastic strain accumulation at the buckled flange after only a few cycles of high-amplitude deformation. A series of analyses are conducted using the proposed model with two limit states under monotonic and cyclic loadings. Beam section geometric parameters, such as flange and web slenderness ratios, varied over the practical ranges of H-shapedbeams to observe their effect on the rotation capacity and low-cycle fatigue life of pre-qualified WUF-W connections.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.39-47
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• 2004

In this paper, the defects of two-dimensional anisotropic elastic bodies are identified by using the boundary element method. The use of numerical models that contain only boundary integral terns reduces the dimensionality of the problem by one. This advantage is particularly important in problems such as crack mechanics. Avoiding domain meshing is also particularly advantageous in the solution of inverse problems since it overcomes mesh perturbations and simplifies the procedure. In this paper, nondestructive approaches for the existing isotropic materials are extended to analyze the elastic bodies made of anisotropic materials such as composites. After verifying that the proposing boundary element model is in good agreement with numerical results reported by other investigators, the effect of noise in the measurements on the identifiability is studied with respect to different design parameters of layered composites. Sample studies are carried out for various layup configurations and loading conditions. The effects of the layup sequences in detecting flaw of composites is explored in this paper.

• Journal of the Korean Society for Railway
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• v.18 no.3
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• pp.212-222
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• 2015

The characteristics of noise emission from tram systems should be investigated in order to design and construct an urban tram network that raises fewer environmental noise problems. In this paper, the characteristics of rolling noise from a tram were studied and a desired stiffness of the rail supports was proposed using a noise prediction model. The mobilities of embedded rails and resilient wheels were predicted using the Timoshenko beam model and the finite element model, respectively. The predicted mobilities were compared with the measured results. Compared with the measured values, the calculated noise level near the track showed small errors for frequencies higher than 300 Hz. Then, the source strengths of rail and wheel components were examined by varying the rail supporting stiffness and the slab supporting stiffness so that suitable stiffness values could be estimated that would reduce noise radiated from rails and wheels but that would not greatly increase the ground vibration.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.273-278
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• 2019

In this study, a new simple method for the estimation of hyperelastic material properties by indentation tests is proposed. Among hyperelastic material models, the Yeoh model with three material properties ($C_{10}$, $C_{20}$, $C_{30}$) is adopted to describe the strain energy density in terms of strain invariants. Finite element simulations of the spherical indentation of hyperelastic materials of the Yeoh model with different material properties are performed to establish a database of indentation force-displacement curves. The indentation force-displacement curves are fitted by cubic polynomials, which are approximated as a product of third-order polynomials of ($C_{10}$, $C_{20}$, $C_{30}$). A regression analysis is conducted to determine the coefficients of the equations for the indentation force-displacement curve approximations. A regression equation is used to estimate the hyperelastic material properties. The present method is verified by comparing the estimated material properties with true values.

• International Journal of Highway Engineering
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• v.3 no.1 s.7
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• pp.185-197
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• 2001

This paper dealt with modification of effective crack length model (ECM) by adding Poisson's ratio term to evaluate fracture toughness of asphalt concrete which varies its material property by temperature. The original ECM model was developed for solid materials, such as cement concrete, and Poisson's ratio of materials was not considered. However, since asphalt concrete is sensitive to temperature variation and changes its Poisson's ratio by temperature, it should be taken into consideration to know exact fracture property under various temperatures. Four binders, including 3 polymer-modified asphalt (PMA) binders, were used to make a dense-grade asphalt mixture and 3-point bending test was peformed on notched beam at low temperatures, from -5oC to 35oC. Elastic modulus, flexural strength and fracture toughness were obtained from the test. The results showed that, since Poisson's ratio was considered, the more accurate test values could be obtained using modified ECM equation than original ECM. PMA mixture showed higher stiffness and fracture toughness than normal asphalt mixture under very low temperatures.