• Journal of Korean Society of societal Security
• /
• v.2 no.2
• /
• pp.75-83
• /
• 2009

When the exposed surface of rock slopes investigated, various factors have not been considered. The factors required to be considered include the vlume swelling of rock caused by stress release at the fault zone, unexposed discontinuities in the earth and so on. Also, rock slope failure occurs sometimes due to these factors. In this paper, we intend to help engineers to judge about the stability of similar new cutting-slopes or the maintenance of already cut-slope, so that they can consider these factors.

• Tunnel and Underground Space
• /
• v.4 no.3
• /
• pp.261-273
• /
• 1994

Direct shear tests were carried out on the rock joints and artificial discontinuities to investigate the influence of joint roughness on the shear strength and deformation behaviour. Single direct shear testing apparatus used in experiment was designed and manufactured. Its capacity is 200 tons of shear load, 20 tons of normal load and 50$\textrm{cm}^2$ of maximum shear area. Test samples were cement mortar with artificial discontinuity and sandstone with natural joint. Peak shear strength was increased as joint roughness or normal stress was increased, especially, linearly increased with roughness angle in cement mortar. If joint roughness angle was constant at low normal stress, shear strength was not affected by width and height of joint roughness in cement mortar. Peak shear strengths obtained from tests were larger than the values calculated by Barton's equation, and shear stiffness was increased with joint roughness coefficient.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.5
• /
• pp.65-73
• /
• 2009

Large scale model tests and numerical analyses are performed to investigate the stress distribution of pillar due to surface loading nearby two-arch tunnel which is constructed in the regularly jointed rocks. It is observed that the influence of discontinuities on the stress distribution in the discontinuous rock mass and the underground stresses induced by surface loading are greater than those of linear elastic theory. Especially, lines of equal stresses are developed to the direction of inclination according to the inclined grade. In cases of discontinuities imbedded in parallel with or vertical to the ground, the pressure bulbs are formed symmetrically, however, the inclined ones result in stress distribution in parallel with and vertical to the planes of discontinuities. Results indicated that stress distribution is seriously affected by the angle of discontinuity. When stresses propagating to the pillar need to be estimated, relative location of surface loading, grade of discontinuous plane, and location of two-arch tunnel should be carefully considered.

• Journal of Welding and Joining
• /
• v.33 no.4
• /
• pp.50-56
• /
• 2015

In general, discontinuity of metallurgical and structural points of weld zone could decline the fatigue strength. For the lightweight trend, the AHSS application in automotive chassis is in-progress. However, there are few research reports on AHSS welds fatigue strength in especially automotive chassis parts. Therefore, in this study, we evaluated the effects of the factors affecting the AHSS welding fatigue strength. As the result, the stress concentration of weld bead is the most important factor for welding fatigue strength. For the enhancement of welding fatigue strength, we focused on reducing the stress concentration of the welding beads. So, we applied and proved the plasma welding process and GTAW (Gas Tungsten Arc Welding) dressing method. It was verified by uniaxial fatigue specimen, fatigue performance increased from 40 to 60% by applying TIG dressing method compared to the conventional GMAW (Gas Metal Arc Welding). These results could be recommended the enhancement of fatigue performance of AHSS.

• Interaction and multiscale mechanics
• /
• v.2 no.1
• /
• pp.31-44
• /
• 2009

While the classical theory of Griffith is the foundation of modern understanding of brittle fracture, it has a number of significant shortcomings: Griffith theory does not predict crack initiation and path and it suffers from the presence of unphysical stress singularities. In 1998, Francfort and Marigo presented an energy functional minimization method, where the crack (or its absence) as well as its path are part of the problem's solution. The energy functionals act on spaces of functions of bounded variations, where the cracks are related to the discontinuity sets of such functions. The new model presented here uses modified energy functionals to account for molecular interactions in the vicinity of crack tips, resulting in Barenblatt cohesive forces, such that the model becomes free of stress singularities. This is done in a physically consistent way using recently published concepts of Sinclair. Here, for the consistency of the model, it becomes necessary to allow for crack reversibility and to consider local minimizers of the energy functionals. The latter is achieved by introducing different time scales. The model is solved in its global as well as in its local version for a simple one-dimensional example, showing that local minimization is necessary to yield a physically reasonable result.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.865-872
• /
• 2006

Recently, many apartment buildings in the shear wall system often has pilotis in the lower story to meet the architectural needs. If the lateral force resisting system consists of shear walls supported by columns and beams. the discontinuity at the lowest level with pilotis results in the vertical irregularity with strength and stiffness. So, there are needs to be considered tile analysis and design about column and beam bellow shear walls and the behavior and stress condition of structure by stiffness change being generated at shear walls. The purpose of this paper is to investigate the behavior of shear wall structures with pilotis using the floors modeled as rigid diaphragm or semi rigid diaphragm. Through analyses, after estimating values of the story drift, natural period, stress condition of shear walls and the forces of column, we inferred how the behavior of shear wall structures with pilotis was influenced by the floor stiffness.

• Journal of Welding and Joining
• /
• v.21 no.5
• /
• pp.575-581
• /
• 2003

It has been well known that the ductile cracking of steel would be accelerated by triaxial stress state. Recently, the characteristics of critical crack initiation of steels are quantitatively estimated using the two-parameters, that is, equivalent plastic strain and stress triaxiality, criterion. This study is paid to the fundamental clarification of the effect of geometrical heterogeneity and strength mismatching, which can elevate plastic constraint due to heterogeneous plastic straining, and loading rate on ductile crack initiation behavior. Also, the ductile crack initiation testing were conducted under static and dynamic loading using round bar specimens with circumferential notch and strength mis-matching. The result showed that the nominal strain at ductile crack initiation of circumferential notch specimens small then the round bar specimens for effect of geometrical discontinuity. Also, the nominal strain at ductile crack initiation was decreased with decrease of notch root radius of curvature.

• Economic and Environmental Geology
• /
• v.34 no.6
• /
• pp.601-615
• /
• 2001

The study area. Boeun-eup Boeun-kun, belongs to Ogchon metamorphic belt which is highly metamorphosed and consisted of complex geologic formations. Even though the geological structures and formations are complex and metamorphosed, the geological investigation and consideration are not enough and consequently the plane failure is occurred in the rock slope which was under construction on 1 : 0.5 gradient. This area is assessed as unstable and additional failure is possible by the discontinuity with same direction of failure surface. Therefore, the authors evaluate the slope stability using various analysis methods such as SMR, stereographic projection method, and the limit equilibrium analysis. In order to analyze stress redistribution and nonlinear displacement behavior caused by stress release, the authors conduct numerical analysis with UDEC and then the behavior of rock mass is analyzed after reinforcements are applied.

• Steel and Composite Structures
• /
• v.25 no.2
• /
• pp.127-139
• /
• 2017

In this paper, an exact analytical solution for simply supported sandwich plate which considers the permeation effect of adhesives is presented. The permeation layer is described as functionally graded material (FGM), the elastic modulus of which is assumed to be graded along the thickness following the exponential law. Based on the exact three-dimensional (3-D) elasticity theory, the solution of stresses and displacements for each layer is derived. By means of the recursive matrix method, the solution can be efficiently obtained for plates with many layers. The present solution obtained can be used as a benchmark to access other simplified solutions. The comparison study indicates that the finite element (FE) solution is close to the present one when the FGM layer in the FE model is divided into a series of homogeneous layers. However, the present method is more efficient than the FE method, with which the mesh division and computation are time-consuming. Moreover, the solution based on Kirchhoff-Love plate theory is greatly different from the present solution for thick plates. The influence of the thickness of the permeation layer on the stress and displacement fields of the sandwich plate is discussed in detail. It is indicated that the permeation layer can effectively relieve the discontinuity stress at the interface.

• Geotechnical Engineering
• /
• v.2 no.2
• /
• pp.5-16
• /
• 1986

Reasonable solutions are needed when the lateral load acting on the head of a pile can not be ignored. There are many difficulties in analyzing the displacement of a laterally loaded Pile because of the complex interaction between the pile and the surrounding soil. In this paper, assuming that a pile and surrounding soil are elasto-plastic mass, and discontinuity between the two is connected with interface elements, writers have tried to solve the problem by using three-dimensional finite element method. Furthermore, the results of numerical analysis obtained by the developed program in this study have been compared with measured field values. The conclusions of this study are as follows; 1. Assuming that the soil behaves as an elasto-plastic mass, there has been a good agreement with measured field displacements. 2. It has been confirmed that interface elements overcome discontinuity between a pile and surrounding soil. 3. As the thickness of interface elements Increases, the stress and the displacement decrease. Al- though the difference is not significant, good results can be expected when it is as thin as possible.