• Journal of Korean Society of Steel Construction
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• v.13 no.2
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• pp.153-162
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• 2001

A direct design method of three-dimensional frames using practical advanced analysis is presented. In this method. separate member capacity checks encompassed by the code specifications are not required. because the stability of separate members and the structure as a whole can be rigorously treated in determining the maximum strength of the structures. Advanced analysis accounts for geometric and material nonlinearities. The geometric nonlinearlity is considered by the use of stability function. The material nonlinearity is accounted for using CRC tangent modulus and parabolic function. The load-displacements predicted by the proposed analysis compare well with those given by other approaches. A design example has been presented for a 22-story frame. The analysis results show that the proposed method is suitable for adoption in practice.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.77-88
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• 2000

연약지반상에 하중 경감을 목적으로 발포성 폴리스티렌(Expanded Polystyrene)을 사용하는 사례가 최근 꾸준히 증가하고 있다. 공법의 요점은 연약지반상에 축조되는 상부구조물에 의한 응력증가를 감소시켜서 결국에는 침하를 방지하기 위한 것이다. 이것을 지오폼(geofoam)이라고 하는데, 지오폼은 교대나 옹벽의 뒷채움재로 사용할 경우 횡토압을 감소시키기 때문에 옹벽이나 교대의 뒷채움재료로 사용하기도 한다. 이와 같이 그 사용이 꾸준히 증가하고 있지만 뒷채움이나 연악지반상에 사용할 때 지오폼의 거동을 예측하는 적절한 수치모델이 아직은 개발되자 않았다. 본 연구에서는 지오폼의 응력-변형 특성을 연구하고 그 탄소성 예측모델을 제시하였다. 이를 위하여 삼축압축시험을 실시하였으며 구속응력과 지오폼의 밀도를 다양하게 변화시켜 그 응력-변형특성을 조사하고 회귀분석을 통하여 비선형 구성모델을 제시하였다. 그 결과 지오폼은 탄성 선형모델보다 탄소성모델 특성에 더 가까운 것을 알 수 있었으며 체적변화율과 축방향 변형률에는 특별한 상관 관계가 있음을 알 수 있었다.

• Korean Chemical Engineering Research
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• v.48 no.6
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• pp.784-790
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• 2010

VOCs such as acetone, benzene, toluene, ethylbenzene were adsorbed in a fixed-bed adsorber using zeolite synthesized from coal fly ash and 4 kinds of activated carbon at 101.3 kPa. The adsorber was operated batchwise with the charge of 5 g adsorbent to obtain the breakthrough curve of VOCs. Experiments were carried out at $40^{\circ}C$, nitrogen flow rate of $70cm^3/min$ and sparger temperature of $30^{\circ}C$. The deactivation model was tested for these curves by combining the adsorption of VOCs and the deactivation of adsorbent particles. The observed values of the adsorption rate constant and the deactivation rate constant were evaluated through analysis of the experimental breakthrough data using a nonlinear least square technique. The experimental breakthrough data were fitted very well to the deactivation model than the adsorption isotherm models in the literature. Also, adsorption capacities of adsorbents were obtained from the breakthrough curve to observe the correlation between adsorption capacity and the physical properties of VOCs.

• Geotechnical Engineering
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• v.12 no.5
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• pp.127-136
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• 1996

Recently, EPS which has unit weight of only 20~30kg/m3, is used for acquiring the safety of settlement and bearing capacity, In Korea, EPS was first used in 1993 as backfill material for abutment that was constructed on soft ground in Inchon. Since then EPS has been used increasingly as backfill material. However, adequate modelling has not yet been proposed for the prediction of the behavior of EPS. Only it's design strength was proposed as the results of unconfined strength and creep test. Accordingly this paper executed triaxial compression test on EPS with various density and confining pressure. Through the analysis of test data the behavior of EPS for strainstress, tangential modulus and poisson's ratio can be expressed in functions with parameters of density and confining pressure of EPS. From these results, this paper proposed a nonliner model describing the behavior of EPS.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.565-572
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• 2009

In this study, corrosion resistance of palm oil fuel ash (POFA) concrete as a blended concrete is evaluated by using electrochemical technique. The POFA is an industrial byproduct obtained from fuel ash after extracting palm oil from palm-tree. In order to obtain basic material characteristics of the POFA concrete, tests on compressive strength, slump, weight loss, bleeding and expansion ratio were carried out the early-aged POFA concrete. On the other hand, durability characteristics, both chloride penetration and carbonation depth test, were also conducted. Finally, corrosion resistance were evaluated by applying electro-chemical artificial crack healing technique, and the tests on the impressed voltage characteristic, galvanic current and linear polarization resistance. From the experimental results, it was found that long-term strength, bleeding, lower slump ratio, expansion ratio, chloride penetration, carbonation and corrosion resistance were improved by using the POFA due to activated pozzolanic reaction. It can be also mentioned that POFA concrete has a potential to be used as a cementitious binder for green-recycling resources.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.73-79
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• 2011

Based on the results of Part 1 of our two-parts paper, the possibility on field applicability of CMDS(Coal Mine Drainage Sludge) mixed with bentonite and cement as a liner in landfill sites was investigated. The optimum moisture content that met the landfill liner condition was obtained when the ratio of CMDS: bentonite: cement was 1: 0.5: 0.3 in a lab-scale. The relative compaction was measured in 90.1%, which results for construction field have been generally acceptable. In this study, a large-scale Lysimeter($1.0m{\times}1.5m{\times}2.0m$) was used to simulate the effects of the layer on the freeze/thaw by -20 average temperature. The mixture after freezing/thawing showed compressive strength more than $5kg/cm^2$, which was satisfied with EPA standards. Initial permeability of CMDS was $7.10{\times}10^{-7}cm/s$ and permeability its mixture after freezing/thawing was increased to $9.80{\times}10^{-7}cm/s$. The change of temperature in the layers rises and falls with linear and temperature gradient keep maintain the present state. Moisture contents in the layers have not been radically changed. Through the leaching test determined by KSLT method, it was found that heavy metals excluding Zn and Ni were not leached out or leached out less than the standards during 7 cycles of freezing/thawing process. Since it shows the increased permeability about 1.5 times and slight change in moisture content, but it was satisfied with EPA standar through 7 cycles of freezing/thawing process, this mixture can be applied as a liner in landfill final cover system.