• Journal of the Korean Geosynthetics Society
• /
• v.13 no.4
• /
• pp.143-151
• /
• 2014

This paper describes external and internal stability of reinforced earth wall using large-scale modular block and geogrid reinforcement. The evaluation for external and internal stability was conducted to analyze effect of wall height, reinforced soil (or backfill soils) and reinforcement strength. The external stability showed that the analysis cases were satisfied with design criteria, when the required minimum length and vertical spacing of reinforcement were 0.7H and 1m, respectively. The internal stability conformed that some cases were satisfied with design criteria in $25^{\circ}$ of internal friction angle of reinforced soil. Expecially, it will be applicable as wall structure considering a structural stability and economic efficiency based on evaluation of internal stability.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.10B
• /
• pp.1876-1884
• /
• 1999

The next generation of wireless LAN AND PBX systems will make use of the unlicensecd band at 2.5 GHz. Deployment of these systems inside buildings requires and understanding of propagation characteristics within buildings. Because the wavelength is small compared to building dimensions, ray methods can be used to predict propagation, but they require knowledge of the transmission and reflection properties of walls. This paper reports on transmission measurements made at walls made of gypsum board on metal studs, and at concrete block walls using directive antennas. The measurements are found to give good agreement with theoretical results that account for the periodic nature of the wall structure.

• Explosives and Blasting
• /
• v.31 no.2
• /
• pp.6-13
• /
• 2013

Recently, complaints or environmental problems caused by the noise and dust generated from crusher of the mine and quarry are emerging. Therefore mining facilities such as crushers and mills have been installed in an underground. In order to facilitate crusher equipments in the underground, excavation of large space is required and then the stability of the large space underground structure is an important issue. In this study, the blast experiments, which use a block of the limestone, are performed. Based on the blast experiments, the numerical model was prepared and simulated using dynamic fracture process analysis code(DFPA) with considering the rising time of applied borehole pressure and microscopic tensile strength variation. Comparing the non-dimensional crack length and no-dimensional tensile strength obtained from blast experiments and numerical analyses, the input parameters of DFPA code for predicting a radial tensile crack in limestone blasting were determined.

• The Journal of the Acoustical Society of Korea
• /
• v.35 no.3
• /
• pp.223-233
• /
• 2016

Design of a vegetation type sound barrier was presented as a noise barrier on the boundary of neighborhood facilities including schools, and apartments. The suggested noise barrier is made of unit blocks that are to be formed by stacking over the wall structure containing the plant and soils in the blocks. The advantage of the vegetation noise barrier is to acquire not only sound absorptive effects of plants and soils, but also sound diffusive effect caused by the irregular surface of the barrier which could eventually mitigate the noise. First, the optimum size of the units to obtain the highest noise reduction was investigated using 1/10 scaled model experiment, and sound attenuation experiments were carried out using a 1/2 mock-up model which is 2 m high and 5 m long. Total 1,137 unit blocks were made of synthetic woods with the size of $10{\times}10{\times}9cm$. These unit blocks were installed on the both side of the 1/2 mock-up steel framed noise barrier. As a result, it was revealed that the block typed vegetation noise barrier has 7 dB higher insertion loss in comparison with the general plane noise barrier. Also, it was found that the appropriate size of unit blocks is $20{\times}20cm$ which has large effect of sound insertion loss.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.4
• /
• pp.2006-2012
• /
• 2013

This case study deal with the investigation of various causes and analyses concerning the cases of the collapse of reinforced segmental retaining walls installed for newly constructing a peripheral road within the campus of ${\bigcirc}{\bigcirc}$ University located in Gyeonggi-do. As results of stability analyses and reviewing of design documents concerning collapsed reinforced segmental retaining walls, such a collapse appeared because of problems related to construction including poor-compacted backfill, the omission of the investigation on the bearing capacity, the length and space in the installation of reinforced materials, and drainage systems. Also, problems during diverse types of designing were confirmed involving the stability analysis of the entire slope stability to be considered during designing and failure in application of the proposed methods of FHWA or NCMA which are generally used for two-tier reinforced segmental retaining walls. In addition, based on these details of the stability assessment, the study proposed reinforcement solutions and construction methods for stabilizing reinforced segmental retaining walls to be reconstructed in the future.

• 한국방재학회:학술대회논문집
• /
• 2011.02a
• /
• pp.182-182
• /
• 2011

현재 국내에서 PSC 거더의 제작은 주로 포스트텐션방식을 사용하고 있다. 포스트텐션방식은 콘크리트 양생 후 긴장력을 도입하여 제작회전율이 높은 특성을 가지나 쉬스, 그라우팅, 정착장치 등이 요구되어 조립과정이 복잡하고 제작단가가 높다. 교량에 적용되는 PSC 거더를 포스트텐션방식 대신에 프리텐션방식으로 제작한다면 제작단가를 대폭 감소시킬 수 있을 것이나, 교량용 PSC 거더의 길이가 일반적으로 30~50m이므로 공장에서 제작하여 현장으로 운반하는 것은 운반비용의 상승 및 운반 가능한 크기의 제한을 받게 된다. 운반의 문제를 해결하기 위해서는 현장에서 PSC 거더를 제작하여야 하는데 현장에 긴장대를 고정식으로 설치하는 것은 제작단가의 상승으로 이어져 경제성을 잃게 된다. 따라서 현장에서 사용할 수 있도록 이동식 긴장대를 제작한다면 경제성을 갖춘 프리텐션방식의 PSC 거더 생산이 가능할 것이다. 50m급 이동식 긴장대에는 약 10MN에 이르는 매우 큰 긴장력이 가해져 이동식 긴장대가 콘크리트 양생전까지 이 긴장력을 저항하여야 한다. 본 논문에서는 유한요소 해석프로그램인 ABAQUS를 사용하여 50m급 PSC 거더를 생산할 수 있는 이동식 긴장대를 모델링하여 약 10MN에 이르는 긴장력이 가해질 때에 이동식 긴장대의 각 구성요소의 거동특성 및 하중에 대한 안전성 및 좌굴에 대한 안정성 확보 여부를 해석적으로 파악하고자 한다. 이동식 긴장대는 구성요소인 정착블럭(긴장BOX)과 중간연결블럭으로 나누어 모델링하였다. 정착블럭(긴장BOX)은 다수의 강판을 4절점 쉘요소(S4R)를 사용하여 직육면체의 BOX 형상에 내부를 보강한 단면으로 구성하였고, 중간연결블럭은 H형강 2개를 일체화한 긴장대 거더와 콘크리트 바닥판 블록이 볼트로 합성된 구조이며, H형강은 4절점 쉘요소(S4R), 바닥판블럭은 8절점솔리드요소(C3D8R)를 사용하였다. 긴장대거더와 바닥판블럭은 합성거동을 하도록 weld option을 사용하여 부분적으로 결합하였다. 정적해석결과 이동식 긴장대에 발생하는 응력은 도로교 설계기준에 SS400 강재의 허용응력 140MPa 보다 작으며 선형탄성좌굴 해석결과 가력하중의 2.22배 약 21MN의 하중이 가력되어야 전체좌굴이 발생하게 될 것으로 추정된다. 해석결과를 보아 50m급 PSC 거더를 생산할 수 있는 이동식 긴장대는 하중에 대한 안전성 및 좌굴에 대한 안정성을 확보하고 있는 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.260-266
• /
• 2009

Non-revenue water reduction(NRW) technologies are implemented to evaluate and manage leakages scientifically in water distribution systems under local governments. A development of quantitative leakage indicator by measuring minimum night flow, pressure control policy by installation of PRV(pressure reducing valve) and the establishment of leakage prevention schemes by residual life modeling of deteriorated water pipes are reviewed and studied. Estimation models of allowable leakage are developed by measuring and analyzing minimum night flow at residential and commercial area in Nonsan city, which is suggested from UK water industry and can improve an existing leakage indicator for the evaluation of non-revenue water. Also, pressure control method is applied and analyzed to Uti distribution area in Sacheon city in the operation aspect. As results, $466\;m^3/day$ of leakage can be reduced and it is expected that 113million won of annual cost can be saved. In the part of corrosion velocity and residual life assessment, non-linear prediction models of residual thickness are proposed by assessment of corrosion velocity based on exposure years, soil and water quality etc., since the deteriorated water pipe play a major role to increase leakage. It is expected that collection data and analyzing results can be applied effectively and positively to reduce non-revenue water by accumulating surveying data and verifying the results in the business field of water distribution systems under local governments.

• Journal of the Korean Geosynthetics Society
• /
• v.11 no.2
• /
• pp.39-47
• /
• 2012

This paper describes large-scale pullout test results of geosynthetic strip, which can be applied in reinforced earth wall with block-type wall facing. The pullout tests are conducted to evaluate the strain distribution, the induced pullout force and the pullout strength. The maximum pullout force is appeared regardless of reinforcement width and normal stress when end displacement is less than 15 mm. The pullout behavior based on horizontal spacing of reinforcement was similar in relationship between pullout force and end displacement. The strain distribution and pullout force distribution of the geosynthetic strip are concentrated in the front part of reinforcement, and it appeared clearly in higher normal stress condition This means that the pullout behavior of geosynthetic strip is affected by the bond between soil and friction resistance reinforcement according normal stress. Therefore, the pullout resistance design is reasonable when pullout behavior of geosynthetic strip should be evaluated by effective length considering tensile characteristic.

• Journal of Korean Association for Spatial Structures
• /
• v.8 no.3
• /
• pp.45-51
• /
• 2008

A single layer-latticed dome is advantageous for large span structures because it is very stiff despite the light weight of the structure itself. However, this structure becomes easily unstable during erection due to its large size. The Block method is popular with the large span structures. A partial block of the dome is fabricated on the ground and lifted by crane to a designated location of structures. The lifting point selection is very important to create a stable erection and to avoid buckling of members during the erection. The purpose of this study is to analyze the structural behaviors and buckling characteristics according to the lifting point of single-layer latticed domes with triangle network in order to take materials about the safe and economic erection. The conclusions are obtained as follow. 1) The buckling strength of the block part varies with the location of lifting points when it is erected. In case, the height of the dome is lower, the effort of buckling strength of the structure is higher. 2) In buckling strength, the effect of the lifting rope length is smaller than it of the lifting points change.