• The korean journal of orthodontics
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• v.36 no.3 s.116
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• pp.178-187
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• 2006

The present study was performed to evaluate the stress distribution on the diameter of the mini-implant and insertion angle to the bone surface. To perform three dimensional finite element analysis, a hexadron of $15{\times}15{\times}20mm^3$ was used, with a 1.0 mm width of cortical bone. Mini-implants of 8 mm length and 1.2 mm, 1.6 mm, and 2.0 mm in diameter were inserted at $90^{\circ},\;75^{\circ},\;60^{\circ},\;45^{\circ},\;and\;30^{\circ}$ to the bone surface. Two hundred grams of horizontal force was applied to the center of the mini-implant head and stress distribution and its magnitude were analyzed by ANSYS, a three dimensional finite element analysis program. The findings of this study showed that maximum von Mises stresses in the mini-implant and cortical and cancellous bone were decreased as the diameter increased from 1.2 mm to 2.0 mm with no relation to the insertion angle. Analysis of the stress distribution in the cortical and cancellous bone showed that the stress was absorbed mostly in the cortical bone, and little was transmitted to the cancellous bone. The contact area increased according to the increased diameter and decreased insertion angle to the bone surface, but maximum von Mises stress in cortical bone was more significantly related with the contact point of the mini-implant into the cortical bone surface than the insertion angle to the bone surface. The above results suggest that the maintenance of the mini-implant is more closely related with the diameter and contact point of the mini-implant into the cortical bone surface rather than the insertion angle.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.33-49
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• 2016

The study area, located in Sinam-ri, Ulsan, in the southeastern part of the Korean Peninsula, is mainly composed of hornblende granite (ca. 65 Ma). Fracturing and reactivation of a fault striking ENE-WSW was strongly controlled by the intrusion of a mafic dyke (ca. 44 Ma), which behaves as a discontinuity in the mechanically homogeneous pluton, increasing the instability of the basement in this area. A geometric and kinematic study undertaken to interpret the faults and fractures was performed in a trench excavated almost perpendicular to the orientation of the dyke. The analysis of structural elements, such as dykes, veins, and faults, is used to infer the deformation history and to determine the paleostress orientations at the time of formation of the structures. The deformation history established based on this analysis is as follows: (1) NNE-SSW, E-W, ENE-WSW, and NE-SW trending fractures had already developed in the pluton before dyke intrusion; (2) felsic dykes intruded under conditions of σ_Hmax oriented N-S and σ_Hmin oriented E-W; (3) mafic dykes intruded under conditions of σ_Hmax oriented E-W and σ_Hmin oriented N-S; (4) dextral reactivation of the main fault associated with the development of hydrothermal quartz veins under conditions of σ_Hmax oriented E-W and σ_Hmin oriented N-S; (5) sinistral reactivation of the main fault and high-angle normal faults under conditions of σ_Hmax oriented NE-SW and σ_Hmin oriented NW-SE; and (6) dextral reactivation of the main fault and NE-SW low-angle reverse faults under conditions of σ_Hmax oriented NW-SE and σ_Hmin oriented NE-SW. These results are consistent with the tectonic history of the Pohang-Ulsan block in the southeastern part of the Korean Peninsula, and indicates the tectonic deformation of the southern area of the Ulsan fault bounded by Yangsan fault was analogous to that of the Pohang-Ulsan area from the Cenozoic. This work greatly aids the selection of sites for critical facilities to prevent potential earthquake hazards in this area.

• Korean Journal of Agricultural Science
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• v.10 no.2
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• pp.277-291
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• 1983

In order to investigate the shear characteristics of earth structure after construction. Four sample soils with different gradation were selected and compacted under the optimum moisture content and the maximum dry density. And the direct shear test and the triaxial compression test were performed with those sample soils under various pre-compression loads. The results were summarized as follows; 1. With the increase of the percent passing of No. 200 sieve, the cohesion of soil increased regularly and the internal friction angle of soil decreased with slow ratio. 2. The pre-compression increased the shear strength of compacted cohesive soil. The increase of cohesion was very apparent but the internal friction angle didn't show such regular tendency. 3. With the increase of pre-compression load, the slope of stress-strain curve showed steep at the early stage of horizontal strain. The vertical strain was small at the compression stage and big at the expansion stage. 4. When the vertical stress of shear test with increase in the horizontal strain was small, stress ratio(shear stress vs. vertical stress) of sample showed the largest value and the slope of stress ratio curve showed also steep. 5. When the sample was had the same condition, the cohesion of soil showed bigger value in the triaxial compression test and the internal friction angle of soil showed bigger value in the direct shear test.

• Explosives and Blasting
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• v.14 no.2
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• pp.71-80
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• 1996

A series of nurmerical analysse for the earhtquake of Iran railway tunnles under construction by NATM(New Astrian Tunnelling Method) were careid out throuth a pseudo-dynamic analyses techique used in a FFM computer program, DWTAP(Daewoo Tunnel Analysis Program), and the results are described in the paper. The analyses were performErl for two case;one is for the primary supports and the other is for the rompletEd permanent roncrete lining. The horizontal and verical groW1d accelerations for the design were estimatEd as 0.34 g and 0.23 g, respectively based on the historical reismic rerords in the proj3et area and the empirical equations. The results show that the turmel would be safe W1der the anticipitOO earthquake motion with the permanent roncrete lining, but some minor cracks rnigt be developErl in the primary shotcrete lining without any significant structural damages.

• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.595-604
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• 2000

Web openings of large beams provide space for wiring, piping, and duct work to provide for proper drainage, pipes and duct must be slightly sloped with the attendant result that all web openings can not be centered on the centroidal axes of the beams. Test specimens are made for opening-depth to beam-depth ratio of 0.5 and for eccentricities of the opening center line of 10% from middepth of the beam because of the proximity of the opening edge to the flange. In this paper, available test results and theories relating to the strength of composite beams having eccentric rectangular openings are surveyed and experiments were carried out to examine the structural behaviors. In all the tests in this paper good agreement is demonstrated with maximum loads measured in tests, and observed failure modes Furthermore, compared with analytical values and experimental values of interaction diagram between moment and shear capacity were safed as it is scattered with outer part of the analytical values.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.362-371
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• 2013

We conducted hollow cylinder tensile strength tests and Brazilian tests in Seokmo granite to measure tensile strength necessary for estimating the magnitude of the maximum horizontal principal stress in hydraulic fracturing stress measurements. Two different pressurization rates were used in hollow cylinder tests. Tensile strengths were determined to be higher at higher pressurization rate, which suggests that tensile strength should be measurement at the same rate used in actual in situ hydraulic fracturing tests. Considering the effect of pressurization rate and specimen size on tensile strength, the hollow cylinder tests and Brazilian tests yield similar results each other. This demonstrates that Brazilian tests can be utilized to produce representative tensile strengths for interpretation of hydraulic fracturing test results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.4
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• pp.227-233
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• 2001

최근 비약적인 경제발전에 힘입어 장대교량, 항만, 댐, 도로, 원자력 발전소 등과 같은 대규모 기간구조물의 건설이 증가하고 있으며, 구조물은 대형화 혹은 고강도화되는 추세에 있다. 특히, 전술한 구조물을 매스콘크리트로 가설하게 되면 초기재령시에 수화열로 인한 균열이 발생할 가능성이 매우 높기 때문에 효율적인 매스콘크리트의 개발과 매스콘크리트 구조물의 설계기술 및 시공방법이 중요한 연구대상으로 등장하게 된다. 본 논문에서는 가로 52.6m, 세로 14.4m, 높이 8.5m의 기계기초 매스콘크리트의 시공에 적합한 온도관리기법을 다음과 같은 단계로 제안하고자 한다. 먼저 온도상승요인을 최소화하는 콘크리트의 배합비를 산정한다. 산정된 콘크리트의 열특성을 측정하기 위해 단열온도실험을 수행하여 각종 열특성상수와 단열온도 상승곡선식을 도출한다. 이와 같은 열특성치를 콘크리트 구조체에 적용하여 열응력해석을 수행한다. 이와 같은 열응력해석을 통하여 구조물의 분할타설높이에 따라 온도균열이 발생하지 않는 콘크리트 내외부의 온도차를 결정한다. 이때 열응력해석에 범용 유한요소 프로그램인 Diana을 사용한다. 콘크리트의 타설은 현장조건과 타설시점을 최대로 고려하고 양생방법으로 콘크리트 내외부의 온도차를 최소화하기 위해 이중단열효과가 있는 거푸집과 가열장비을 사용한다. 또한 콘크리트의 온도관리를 위하여 구조물 내외부에 온도게이지를 매립하고 30분마다 계측을 수행하면서 콘크리트 내외부 온도차가 허용 해석범위를 유지하도록 한다. 양생기간은 7-10일 정도를 유지한다. 전술한 온도관리기법을 통하여 완공후 수평정밀도가 기초의 허용침하량으로 환산하여 $1{\mu}m$ 인 고정밀도의 기계기초는 완벽하게 시공되었다. 따라서 매스콘크리트의 온도균열을 제어할 수 있는 시공방법으로 제안한다. 또한 매스콘크리트의 내외부 온도차를 단열온도실험과 온도해석으로부터 정한 값이내로 제어하고 충분한 양생관리를 병행하면 수화열에 의한 콘크리트의 온도균열을 최소화할 수 있을 것으로 기대한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.453-459
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• 2006

This paper presents an experimental evaluation of wandering effect on asphalt concrete pavement responses. A laser-based wandering system has been developed and its performance is verified under various field conditions. The portable wandering system composed of two laser sensors with Position Sensitive Devices can allow one to measure the distance between laser sensors and tire edges of moving vehicle. Therefore, lateral position of each wheel on the pavement can be determined in a real time manner. Pavement responses due to different loading paths are investigated using a roll over test which is carried out on one of asphalt surfaced pavements in the Korea Highway Corporation test road. The pavement section (A5) consists of 5 cm thick surface course; 7 cm intermediate course; and 18 mm base course, and is heavily instrumented with strain gauges, vertical soil pressure cells and thermo-couples. From the center of wheel paths, seven equally-spaced lateral loading paths are carefully selected over an 140 cm wandering zone. Test results show that lateral horizontal strains in both surface and intermediate courses are mostly compressive right under the loading path and tensile strains start to develop as the loading offset becomes 40 cm from the wheel path. The development of the vertical stresses in the top layers of subbase and anti-frost is found to be minimal once the loading offset becomes 50 cm.

• The Journal of Engineering Geology
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• v.10 no.3
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• pp.237-245
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• 2000

This study was for characterizing the engineering geological properties of Moryang Fault, and providing the basic data for tunnel design. Land-sat image analysis, geologic surveys, resistivity prospecting and 3-dimensional analysis for results of resistivity prospecting, core boring, mineralogical identification and chemical analysis for the bedrock, and K-Ar age dating for fault clay were carried out for the study of Moryang Fault which is located at Duckhyunri Sangbukmyun Uljinkun Ulsan metropolis. As a result of the study, it was shown that strike/dip was N20-3$0^{\circ}C$E/70-9$0^{\circ}C$NW, width of fault ranged from 20 to 60m(maximum 80m), and depth was more than 50m. K-Ar age dating results of fault clay were 5,700$\pm$1.129Ma and 1,900$\pm$0.380Ma. Hydraulic fracturing test results showed the principal stress direction similar to the strike of Moryang Fault.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.211-225
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• 2019

Recently, earthquakes have occurred throughout the entire region of Korea and seismic analysis studies have been actively conducted in various fields. SSI analyses studies considering ground have been carried out consistently. However, few comparative analyses have been performed on the dynamic behavior of buildings according to numerical analysis method in the case of the previous dynamic analyses considering grounds. Therefore, in this study, the dynamic analyses were performed on a high-rise building by using both a finite element program MIDAS GTS NX and a finite difference program FLAC 2D. The results were compared and analyzed each other. As a result, both the maximum compressive and tensile bending stresses of above ground and below ground part were estimated to be a little larger by MIDAS GTS NX than by FLAC 2D. However, the maximum horizontal displacement value, the horizontal displacement distribution, and the position of weak part were turned out to be similar in both analysis programs. Therefore, it can be concluded that there is no difference in using either a finite element program or a finite difference program for the convenience of a user for a dynamic analysis.