• Computers and Concrete
• /
• 제26권3호
• /
• pp.227-237
• /
• 2020

Strain rate investigations are needed to calibrate strain-rate-dependent material models and numerical codes. An appropriate material model, which considers the rate effects, need to be used for proper numerical modeling. The plastic concrete cut-off wall is a special underground structure that acts as a barrier to stop or reduce the groundwater flow. These structures might be subjected to different dynamic loads, especially earthquake. Deformability of a structure subjected to dynamic loads is a principal issue which need to be undertaken during the design phase of these structures. The characterization of plastic concrete behavior under different strain rates is essential for proper designing of cut-off walls subjected to dynamic loads. The Cowper-Symonds model, as one of the most commonly applied material models, complies well with the behavior of a plastic concretes in low to moderate strain rates and will be useful in explicit dynamics simulations. This paper aims to present the results of an experimental study on mechanical responses of one of the most useful types of plastic concrete and Cowper-Symonds constant determination procedures in a wide range of strain rate from 0.0005 to 107 (1/s). For this purpose, SHPB, uniaxial, and triaxial compression tests were done on plastic concrete samples. Based on the results of quasi-static and dynamic tests, the dynamic increase factors (DIF) of this material in different strain rates and stress state conditions were determined for calibration of the Cowper - Symonds material models.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
• /
• pp.93-94
• /
• 2006

The sheath of a single-conductor cable for ac service acts as a secondary of a transformer, the current in the conductor induces a voltage in the sheath. When the sheaths of single-conductor cables are bonded to each other, as is common practice for multi-conductor cables, the induced voltage causes current to flow in the completed circuit. This current causes losses in the sheath. Various methods of bonding may be used for the purpose of minimizing sheath losses. In korea, sheath cross bonding system was employed for the prevention of sheath losses, the sheaths wire subjected to at voltages, and the bonding was designed to keep the magnitude of the induced voltages within small limits so as to prevent the possibility of sheath corrosion. But, sheath cross bonding system without transposition of cable can not achieve an exact balance of induced sheath voltages unless the cables are lain in trefoil. This paper describes a transposition system with sheath cross bonding using EMTP(Electromagnetic Transient Program). The transposition system with cross bonding can be extended to longer cable circuits for laid in flat as wall as trefoil by the methods described in this paper.

• 터널과지하공간
• /
• 제16권6호
• /
• pp.476-485
• /
• 2006

발파에 의한 암반의 손상이나 파쇄는 폭약의 폭굉 과정에서 발생하는 충격파와 가스팽창의 영향에 의해 야기된다. 발파에 의한 파괴 메커니즘을 완전히 이해하기 위해서는 두 메커니즘을 같이 연구해야한다. 본 연구에서는 개별 요소법에 기초한 수치해석 프로그램인 PFC2D를 이용하여 발파공 벽면에 작용하는 폭굉압과 가스압을 동시에 모델링 할 수 있고 이에 따른 암반 내 균열 발생을 확인할 수 있는 알고리즘을 개발하였다. 또한 시멘트-모르타르 블록에서의 모형 발파시험을 수치해석을 수행함으로써, 개발된 알고리즘을 검증하였다.

• 터널과지하공간
• /
• 제14권5호
• /
• pp.305-317
• /
• 2004

세계적으로 장벽식 채탄법이 많이 적용된 반면, 국내에서는 좁고 경사진 탄층의 특성에 의하여 위경사승 붕락식 또는 중단 붕락식 채탄법이 주로 사용되었다. 이러한 이유로 국내에 산재하는 폐광산은 그 규모와 특성을 파악하기가 어려운 특징이 있다. 따라서, 본 고에서는 국내 채탄법의 특정을 파악한 후 이를 바탕으로 동해고속도로 2공구 현장의 폐광산에 대한 조사 및 안정성 평가를 실시하였으며 추후 당 현장에 적용 가능한 최적의 지반보강공법을 선정하였다.

• Journal of Plant Biology
• /
• 제31권3호
• /
• pp.169-185
• /
• 1988

Vessel elements in lateral root, tap root, transition region, stem and mid vein of 1-year old, 3-year old and 5-year old ginseng (Panax ginseng C.A. Meyer) are studied with light microscope to clarify the distribution and differentiation of several kinds of vessel elements. Vessel elements are classified into five types such as ring vessel, spiral vessel, scalariform vessel, reticulate vessel and pitted vessel according to the secondary thickenings of cell wall. All of the five types are not observed in each organ, but diverse kinds of vessels are present in stem and mid vein compared with the underground organs such as tap root and lateral root. The length of vessel elements is longest (680$\mu$m) in stem and shortest (143$\mu$m) in tap root. The diameter of vessel elements is 19.0$\mu$m in tap root and the angle of perforation plate comes under 22$^{\circ}$-60$^{\circ}$. The degree of differentiation of vessel elements according to the length, diameter and angle of perforation plate of vessel elements is highest in tap root regardless of the age of ginseng. Three types of perforation plate such as scalariform, intermediate type of simple and scalariform, and simple perforation plate are observed. The vascular tracheids are characteristically observed in mid vein of 1-year old ginseng, and in transition region of 3 and 5-year old ginseng.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 춘계 학술발표회
• /
• pp.607-614
• /
• 2010

Shear behavior of granular soils largely affects the safety and stability of underground and earth structures. This study presents the characteristics of shear zone in a direct shear test using shear wave and electrical resistivity measurements. An innovative direct shear box made of transparent acrylic material has been developed to prevent direct electric current. Bender elements and electrical resistivity probe are embedded in the wall of direct shear box to estimate the shear wave velocities and the electrical resistivity at the shear and non-shear zones. Experimental results show that the void ratio and shear wave velocity at shear zone increase during shearing while the values remain constant at non-shear zone. The results demonstrate correlation among the contact force, small strain shear modulus, and void ratio at shear zone. This study suggests that the application of the modified direct shear box including shear wave and electrical resistivity measurements may become an effective tool for analyzing soil behavior at shear zone.

• 한국조경학회지
• /
• 제33권2호
• /
• pp.111-121
• /
• 2005

The Seoul Housing Corporation pronounced an alternative design competition and a bidding for Eunpyeong New Town in December of 2004. At first many construction companies were interested in the first New Town Project. But at last a few companies had proposed the alternative design and construction cost. This project needed a conjunction of design ideas and technology know-hows. And the client wanted the brand power of construction company. Ultimately the Corporation hoped that the first New Town Project will end up with high quality successfully. This competition had started with the original construction drawings. Then it needed some alternative ideas and the lowest cost. There were two drawings of non changeable part and changeable part. Non changeable parts are structure like housing unit plan, underground parking lots. Changeable parts are outdoor layout, interior design and building facade. So we tried all ideas of landscape technology and design principles within limited guidelines. The author applied new technology like tilted rooftop greening and sustained container greening on high-rise apartment house. This green technology will be the first trial in Seoul and in the world as well. Daewoo Corporation have accumulated greening technology through the researches by national funding since 2002. Through this New Town Project the green technology will go forward step by step.

• 한국지진공학회논문집
• /
• 제21권1호
• /
• pp.69-76
• /
• 2017

Seismic analyses of a pile under a large rigid basement foundation embedded in the homogeneous soil layer were performed practically by a response displacement method assuming a sinusoidal wave form. However, it is hard to take into account the characteristics of a large mat foundation and a heterogeneous soil layer with the response displacement method. The response displacement method is relevant to the 2D problems for longitudinal structures such as tunnel, underground cave structure, etc., but might not be relevant with isolated foundations for building structures. In this study, seismic pile analysis by a pseudo 3D finite element method was carried out to compare numerical results with results of the response displacement method considering 3D characteristics of a foundation-soil system which is important for the building foundation analyses. Study results show that seismic analyses results of a response displacement method are similar to those of a pseudo 3D numerical method for stiff and dense soil layers, but they are too conservative for a soft soil layer inducing large soil pressures on the foundation wall and large pile displacements due to ignored foundation rigidity and resistance.

• 설비공학논문집
• /
• 제16권1호
• /
• pp.101-110
• /
• 2004

This paper presents an analysis of heating energy for apartment houses in a Korean-style apartment building, paying special attention on the effect of their location. Six representative locations encompass three floors and two placements on each floor. Two different roof types are also considered. In order to incorporate actual tenant's refit, a five-zone model composed of one conditioned and four unconditioned spaces is developed. TRNSYS 15 is adopted to estimate heating energy. The predicted results show fairly good agreements with the available measured data, validating the present model. Heating energy needed for an apartment located at the uppermost and lowermost floors is far greater compared with the case of intermediate floors. In addition, an appreciable difference is found between apartment with and without side end wall. Insulation thickness of walls, floors and underground structure appears to be a dominant factor affecting heating energy, which leads to needs of revision of the related regulation. Ridged-roofs instead of flat-roofs are highly recommended in apartment buildings for effective energy saving. It is finally concluded that the location-dependent, severe imbalance in heating energy should be improved and/or reflected in the policy making process and design standards.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
• /
• pp.214-220
• /
• 2003

Pipe jacking is a name for a method to excavate a tunnel by pushing pipe into the ground from an especial pit. Size of tunnels in this method is different from under 900mm (microtunneling) to more than 3,000mm. Method of excavation is also different from hand digging to use of any kind of tunnel boring machines such as slurry and earth pressure balance (EPB) machines. Slurry pipe jacking was firmly established as a special method for the nondisruptive construction of the underground tunnels in urban area. During the pipe jacking and microtunneling process, the jacking load is an important parameter, controlling the pipe wall thickness, need to and location of intermediate jacking station, selection of jacking frame and lubrication requirements. The main component of the jacking load is due to frictional resistance. In this paper the skin friction between pipe surface and surrounding condition also lubricant quality based on a few fundamental tests, were considered. During this study unconfined compressive strength test, dynamic friction measurement test and direct shear box test were raised for one of the largest diameter slurry pipe jacking project in Fujisawa city in Japan. It could be concluded that in slurry pipe jacking, prediction of frictional forces are mainly dependent on successful lubrication, its quality and lubricant strength parameters. Conclusions from this study can be used for the same experiences.