• Journal of the Korean GEO-environmental Society
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• v.10 no.3
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• pp.21-28
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• 2009

As the natural aggregates such as sand and clay are getting exhausted, the quantity of utilizing geosynthetics is being increased in the solid waste landfill. Especially, the waste landfills have been constructed at the gorge in the mountainous area and reclaimed land from the sea in the Korean Peninsula. Those areas are not favorable for construction of waste landfill in geotechnical engineering aspect. In this study, the frictional characteristics of geosynthetics that used in the waste landfill were estimated. Then, the studies of the behavior of geosynthetics and stability of LDCRS (Leachate Detection, Collection, and Removal System) of side slope were conducted in the waste landfill by means of the pilot test, and numerical analysis. Geocomposite which is combined type or separated type is influenced on the strain itself, and also implicated in the stress and strain of geomembrane at the lower layer. The strain on the combined type of geocomposite is about 50% smaller than that of the separated type at the side slope. The lateral displacement and settlement of top at the slope with the separated type are three times greater than that of the combined type. In the numerical analysis, discontinuous plans in between ground and geosynthetic, geosynthetic and geosynthetic, goesynthetic and waste have been modeled with the interface element. The results gave a good agreement with the field large-scale model test. The relative displacements of geosynthetics were also investigated and hence the interface modeling of liner system is appropriate for analysis of geosynthetics liner system in the waste landfill.

• Computational Structural Engineering
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• v.9 no.2
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• pp.133-142
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• 1996

In this paper, two different techniques for mixed-mode type engineering fracture mechanics are investigated to estimate the stress intensity factors by using p-version finite element model. These two techniques are displacement extrapolation with COD and CSD method and J-integral with decomposition method. By decomposing the displacement field obtained from p-version of finite element analysis into symmetric and antisymmetric displacement fields with respect to the crack line, Mode-I and Mode-II stress intensity factors can be determined using aforementioned techniques. The example problems for validating the proposed techniques are centrally and centrally oblique cracked panels under tension. The numerical results associated with the variation of oblique angle and the ratio of crack length and panel width (a /W ratio) are compared with those by theoretical values and empirical solutions in literatures. Very good agreements with the existing solutions are shown.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.1-7
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• 2020

Although the temperature load is an important load among the various loads affecting the behaviors of general rahmen-type temporary bridges (GRTB), no study of the thermal load has been carried out. In the case of GRTB, horizontal displacement should be free, and the generated internal force should be minimized to reduce stress due to a temperature load. Sliding girder type bridge (SGTB) allows the axial deformation due to thermal load, and decreases the axial stress and delivers bending stress. This study examined the temperature behavior of an SGTB. Structural analysis was carried out for four types of spans (eq, 10, 20, 30, and 40m) and three types of pier heights (eq, 2, 4, and 6m) along with the GRTB. The applied loads were a fixed vertical load and an axial temperature load. The friction coefficient was 0.4, which is a representative value of a steel girder. Consequently, the stress of the SGTB increased with increasing span length, regardless of the temperature load. The stress of the GRTB increased with increasing temperature and span length. Compared to the GRTB, the stress of the SGTB decreased by 20% to 50% at the center of the girder and by 50% to 90% at the bottom of the pier. This could secure the structural efficiency compared to the GRTB with the same specifications.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.4
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• pp.3-14
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• 1990

For a moored body on the sea surface, incident waves with narrow-banded spectra excite the body oscillations of short and long periods. Since the period of slow oscillations can be as long as the natural period of the moored body in horizontal modes, resonance can occur and resulting large motions may cause significant strains in mooring cables. By using the perturbation method of multiple scales, the large slow motion can be analyzed without solving any second-order potentials explicitly. To the leading order, the flows associated with the fast and slow motions interact only parametrically and thus they can be studied separately. It is found that the slow motion strongly depends on the mooring stiffness. In particular, if the moring stiffness is considerably weak compared to the body inertia, the slow motion is highly amplified near resonance. It is also shown that the slow motion is associated with the generation of long waves.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1844-1851
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• 1997

Displacement fields and interface stresses are obtained by modifying the potential energy functional with a penalty function which enforces the continuity of stresses at the interface of two-materials. Based on the displacement field and the interface stresses, a new methodology to generate a continuous stress field over the entire domain including the interface of the dissimilar materials has been proposed by combining the L$^{2}$ projection method of stress-smoothing and the Loubignac's iterative method of improving the displacement field. Stress analysis was carried out on two examples which are made of highly dissimilar materials. As a result of the analysis, it is found that the proposed method provides improved continuity of the stress field over the entire domain as well as predicting accurate nodal stresses at the interface. In contrast, the conventional displacement-based finite element method provides significant stress discontinuties at the interfaces. In addition, it was found that the total strain energy evaluated from the improved continuous stress field converge to the exact value as increasing the number of iterations in the proposed method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.2
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• pp.189-196
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• 2009

This paper presents the subparametric finite element model formulated by partial-linear layerwise theory for the analysis of laminate composites. The proposed model is based on refined approximations of two dimensional plane for orthotropic thick laminate plate as well as thin case. Three dimensional problem can be reduced to two dimensional case by assuming piecewise linear variation of in-plane displacement and a constant value of out-of-plane displacement across the thickness. The integrals of Legendre polynomials are chosen to define displacement fields and Gauss-Lobatto numerical integration is implemented in order to directly obtain maximum values occurred at the nodal points of each layer without other extrapolation techniques. The validity and characteristics of the proposed model have been tested by using orthotropic multilayered plate problem as compared to the values available in the published references. In this study, the convergence test has been carried out to determine the optimal layer model in terms of central deflection and stresses. Also, the distribution of displacements and stresses across the thickness has been investigated as the number of layer is increased.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.505-512
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• 2012

In this paper, an efficient yet accurate method for the thermal stress analysis using a first order shear deformation theory(FSDT) is presented. The main objective herein is to systematically modify transverse shear strain energy through the mixed variational theorem(MVT). In the mixed formulation, independent transverse shear stresses are taken from the efficient higher-order zigzag plate theory, and the in-plane displacements are assumed to be those of the FSDT. Moreover, a smooth parabolic distribution through the thickness is assumed in the transverse normal displacement field in order to consider a transverse normal deformation. The resulting strain energy expression is referred to as an enhanced first order shear deformation theory, which is obtained via the mixed variational theorem with transverse normal deformation effect(EFSDTM_TN). The EFSDTM_TN has the same computational advantage as the FSDT_TN(FSDT with transverse normal deformation effect) does, which allows us to improve the through-the-thickness distributions of displacements and stresses via the recovery procedure. The thermal stresses obtained by the present theory are compared with those of the FSDT_TN and three-dimensional elasticity.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.237-242
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• 2001

Residual stress is a dominant obstacle to efficient production and safe usage of products by reducing the mechanical strength and failure properties. Especially, it causes interfacial failure and substrate deflection in the case of thin film. So, the exact evaluation and optimum control of thin film residual stress is indispensable. However, hole drilling or X-ray diffraction techniques have some limits in application to thin film. And, curvature technique for thin film materials cannot give the information about local stress variation. Therefore, we applied the nanoindentation technique in evaluating the thin film residual stress. In this study, we modeled the change of indentation loading curve for residually stressed and stress-free thin films during stress relaxation. The value of residual stress was directly related to the indentation depth change by relaxation. The residual stress from nanoindentation analysis was consistent with the result from curvature technique.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.381-387
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• 2016

In this paper, the methodology applied to the improvement of stress analyses is extended to free vibration and buckling analyses. The essence of the methodology is the Saint-Venant's principle that is applicable to beam and plate models. The principle allows one to dimensionally reduce three-dimensional elasticity problems. Thus the methodology can be employed to vibration and buckling as well as stress analysis. First, the principle is briefly revisited, and then the formations of classical beam theories are presented. To improve the predictions, the perturbed terms (unknowns) are introduced together with the warping functions that are calculated by stress equilibrium equations. The unknowns are then calculated by applying the equivalence of stress resultants (i.e., Saint-Venant's principle). As numerical examples, cantilever and simply supported beams are analytically solved. The results obtained are compared with those of the classical beam theories. It is shown that the methodology can be used to improve the predictions without introducing shear correction factors.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.5-19
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• 2014

In this study, the structural analysis is performed on the method of shallow block and deep cement mixing pile, and then their characteristics and associated behaviors were analyzed. In the case of continuous beam analysis, the predicted settlement was very small, and shear force and bending stress are somewhat overestimated. The frame method is similar to numerical analysis in the internal force shallow block and long pile, but because the settlement of pile is underestimated, the additional calculation using the reaction of the long pile is necessary. For soil arching method and piled raft foundation method, the excessive axial force of long pile was predicted because the load sharing of pile is very large compared to the other methods. In the behavior of the shallow block and deep pile method, the settlement of shallow block and contact pressure are much in the center than the edge. In the estimating method considering the interaction between improved material and ground, the load sharing of the soil-cement pile ranges from 20% to 45%, and the stress ratio is 2.0~5.0 less than piled DCM. The maximum member forces at the boundary conditions of pile head are similar, but in fixed head the axial force and vertical displacement are different in accordance with pile arrangement.