• Geotechnical Engineering
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• v.13 no.5
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• pp.101-124
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• 1997

The root pile system is insitu soil reinforcement technique that uses a series of reticulately installed micropiles. In terms of mechanical improvement by means of grouted reinform ming elements, the root pile system is similar to the soil nailing system. The main difference between root piles and soil nailing are due to the fact that the reinforcing bars in root piles are normally grouted under high pressure and that the alignments of the reinforcing members differ. Recently, the root pile system has been broadly used to stabilize slopes and retain excavations. The accurate design of the root pile system is, however, a very difficult tass owing to geometric variety and statical indetermination, and to the difficulty in the soilfiles interaction analysis. As a result, moat of the current design methods have been heavily dependent on the experiences and approximate approach. This paper proposes a quasi-three dimensional method of analysis for the root pile system applied to the stabilization of slopes. The proposed methods of analysis include i) a technique to estimate the change in borehole radium as a function of the grout pressure as well as a function of the time when the grout pressure is applied, ii) a technique to evaluate quasi -three dimensional limit-equilibrium stability for sliding, iii) a technique to predict the stability with respect to plastic deformation of the soil between adjacent root piles, and iv) a quasi -three dimensional finite element technique to compute stresses and dis placements of the root pile structure barred on the generalized plane strain condition and composite unit cell concept talon형 with considerations of the group effect and knot effect. By using the proposed technique to estimate the change in borehole radius as a function of the grout pressure as well as a function of the time, the estimations are made and compar ed with the Kleyner 8l Krizek's experimental test results. Also by using the proposed quasi-three dimensional analytical method, analyses have been performed with the aim of pointing out the effects of various factors on the interaction behaviors of the root pile system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.25-37
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• 1992

A nonlinear finite element formulation which has the capability of handling very large geometrical changes is presented. The formulation is based on an updated material reference frame and hence true stress-strain test can be directly applied to properly characterize properties of materials which are subjected to very large deformation. For the large deformation, a consistent formulation based on the continuum mechanics approach is derived. The kinematics is referred to an updated material frame. Body equilibrium is also established in an updated geometry and the second Piola-Kirchhoff stress and the updated Lagrangian strain tensor are used in the formulation. Numerical examples for very large deformation of framed structures and plane solids are analyzed for verification purposes. The numerical solutions are obtained by an incremental numerical procedure. The importance of handing material properties properly is also demonstrated.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.25-32
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• 2016

The two-dimensional (2D) analysis is widely used in geotechnical engineering for slope stability analysis assuming a plane-strain condition. It is implicitly assumed that the slip surface is infinitely wide, and thus three-dimensional (3D) end effects are negligible because of the infinite width of the slide mass. The majority of work on this subject suggests that the 2D factor of safety is conservative (i.e. lower than the 'true' 3D factor of safety). Recently, the 3D finite element method (FEM) became more attractive due to the progress of computational tools including the computer hardware and software. This paper presents the numerical analyses on rotational mode and translational mode slopes using the 2D and 3D FEM as well as 2D limit equilibrium methods (LEM). The results of the parametric study on the slope stability due to mesh size, dilatency angle, boundary conditions, stress history and model dimensions change are analysed. The analysis showed that the factor of safety in 3D analysis is always higher than that in the 2D analysis and the discrepancy of the slope width in W direction on the factor of safety is ignored if the roller type of W direction conditions is applied.

• Structural Engineering and Mechanics
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• v.40 no.1
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• pp.65-84
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• 2011

In this paper a simple mathematical model for approximate static analysis of combined system of framed tube, shear core and two outrigger-belt truss structures subjected to lateral loads is presented. In the proposed methodology, framed tube is modeled as a cantilevered beam with a box section and interaction between shear core and outrigger-belt truss system with framed tube is modeled using torsional springs placed at location of outrigger-belt truss; these torsional springs act in a direction opposite to rotation generated by lateral loads. The effect of shear lag on axial deformation in flange is quadratic and in web it is a cubic function of geometry. Here the total energy of the combined system is minimized with respect to lateral deflection and rotation in plane section. Solution of the resulting equilibrium equations yields the unknown coefficients of shear lag along with the stress and displacement distributions. The results of a numerical example, 50 storey building subjected to three different types of lateral loading obtained from SAP2000 are compared to those of the proposed method and the differences are found to be reasonable. The proposed method can be used during the preliminary design stages of a tall building and can provide a better understanding of the effects of various parameters on the overall structural behavior.

• Structural Engineering and Mechanics
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• v.44 no.6
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• pp.775-799
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• 2012

This work approaches the structural performance of masonry arches that have a small ratio between number of vossoirs and span length. The aim of this research is to compare and validate three different methods of analysis (funicular limit analysis F.L.A., kinematic limit analysis K.L.A. and plane stress Finite Element Analysis F.E.A.) with an experimental campaign. 18 failure tests with arches of different shapes and boundary conditions have been performed. The basic failure mechanism was the formation of enough hinges in the geometry. Nevertheless, in few cases, sliding between vossoirs also played a relevant influence. Moreover, few arches didn't reach the collapse. The FLA and KLA didn't find a solution close to the experimental values for some of the tests. The low number of vossoirs and joints become a drawback for an agreement between kinematic mechanism, equilibrium of forces and geometry constraints. FLA finds a lower bound whereas KLA finds an upper bound of the ultimate load of the arch. FEA is the most reliable and robust method and it can reproduce most of the mechanism and ultimate loads. However, special care is required in the definition of boundary conditions for FEA analysis. Scientific justification of the more suitability of numerical methods in front of classic methods at calculating arches with a few vossoirs is the main original contribution of the paper.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2595-2602
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• 2009

Hexamer cluster of N,N-dimethylformamide(DMF) based on the crystal structure was investigated for the equilibrium structure, the stabilization energies, and the vibrational properties in the density functional force field. The geometry (point group $C_i$) of fully optimized hexamer clustered DMF shows quite close similarity to the crystal structure weakly intermolecular hydrogen bonded each other. Stretching force constants for intermolecular hydrogen bonded methyl and formyl hydrogen atoms with nearby oxygen atom, methyl C–H${\cdots}$O and formyl C–H${\cdots}$O, were obtained in 0.055 $\sim$ 0.11 and $\sim$ 0.081 mdyn/$\AA$, respectively. In-plane bending force constants for hydrogen bonded methyl hydrogen atoms were in 0.25 $\sim$ 0.33, and for formyl hydrogen $\sim$ 0.55 mdynÅ. Torsion force constants through hydrogen bonding for methyl hydrogen atoms were in 0.038 $\sim$ 0.089, and for formyl hydrogen atom $\sim$ 0.095 mdynÅ. Calculated Raman and infrared spectral features of single and hexamer cluster represent well the experimental spectra of DMF obtained in the liquid state. Noncoincidence between IR and Raman frequency positions of stretching C=O, formyl C–H and other several modes was interpreted in terms of the intermolecular vibrational coupling in the condensed phase.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.6
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• pp.535-542
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• 2006

A large signal stability analysis of the solar array regulator system is performed to facilitate the design and analysis of a Low-Earth-Orbit satellite power system. The effective load characteristics of every controllable method in the solar array system are classified to analyze the large signal stability. Then, using the state plane analysis technique, the stability of various equilibrium points is analyzed. A nonlinear transformation algorithm, which changes the effective load characteristic of the solar array regulator as constant resistive load, is also proposed for the large signal stability. The proposed resistive current mode control system can control the solar array output for purposes such as peak power tracking control and battery charging control. For the verification of the proposed large signal analysis and resistive current mode control, a solar array regulator system consisting of two 100W parallel module buck converters has been built and tested using a real 200W solar array.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.81-92
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• 2008

Generally the connection of members is defined as hinge or rigid. But, real joints on structure have to be considered semi-rigid connections because this permits relative rotation for members on joints. The purpose of this study is to derive a generalized tangential stiffness matrix of frames with semi-rigid connections and to develop a buckling analysis program. For the exact stiffness matrix, an accurate displacement field is introduced using an equilibrium equation for beam-columns under the bending and axial forces. Also, stability functions that consider sway deformation and force-displacement relations with rotational spring on ends were defined. In order to illustrate the accuracy of this study and the characteristics of semi-rigid for system buckling load, samples of angle-, portal- and 3-story frames with semi-rigid connections are presented, where the proposed approach is found to be in excellent agreement with other research results. Meanwhile, the application of codes such as Eurocode 3 and LRFD led to significant inaccuracies.

• Archives of Plastic Surgery
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• v.34 no.1
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• pp.128-130
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• 2007

Purpose: Pnumosinus dilatans is a rare disease that one or more of the paranasal sinuses are dilatated without functional alteration. The most frequently involved sites are frontal and sphenoid sinus. Facial asymmetric contour is the most common signs and nasal obstruction and pain may be combined. The purpose of reconstruction of pneumosinus dilatans is two-fold, to re-establish a permanent pressure equilibrium of sinus and to correct the possible facial deformities. Methods: We present a case of a 24-year-old female with a 7-year history of protrusion of right malar region. Plane radiography and computed tomography detailed an abnormal expansion of the right maxillary sinus without thinning of bony wall, leading to diagnosis of maxillary pneumosinus dilatans. Surgical decompression and maxilloplasty were achieved by ostectomy of anterior wall of maxillary sinus and repositioning of removed bony fragment with miniplate. Results: Post operative course was uneventful without complication and malar height became symmetric by physical and radiologic examination. Conclusion: We corrected successfully pneumosinus dilatans of maxillary sinus by surgical decompression and maxilloplasty. For this case, we reviewed literature related to this topic.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.820-830
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• 1989

The tire inflation and contact problem has been solved by a finite element method. The finite element formulation is derived from the equilibrium equations by the principle of virtual work in the form of an updated Lagrangian formulation for incremental analysis. Then, a contact formulation is added to the finite element formulation to calculate stress state of tire in contact with flat rigid road under the load due to the self-weight of a vehicle. In the finite element analysis, equations of effective material properties are introduced to analyze a plane strain model of the shell-like tire by considering the bending effect of reinforced steel cords. The proposed equations of effective material properties produced stress concentration around the edge of belt layers, which does not appear when other well-known equations of material properties are adopted. The result from the above algorithm demonstrates the validity of the formulation and the proposed equations for the effective elastic constants. The result fully interprets the cause of separation between belt layers by showing the stress concentration.