• Earthquakes and Structures
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• 제7권5호
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• pp.691-704
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• 2014

Reinforced concrete (RC) shear walls are commonly used for building structures to resist seismic loading. While the RC shear walls can have a high load-carrying capacity, they tend to fail in a brittle mode under shear, accompanied by forming large diagonal cracks and bond splitting between concrete and steel reinforcement. Improving seismic performance of shear walls has remained a challenge for researchers all over the world. Engineered Cementitious Composite (ECC), featuring incredible ductility under tension, can be a promising material to replace concrete in shear walls with improved performance. Currently, the application of ECC to large structures is limited due to the lack of the proper constitutive models especially under shear. In this paper, a new Cyclic Softening Membrane Model for reinforced ECC is proposed. The model was built upon the Cyclic Softening Membrane Model for reinforced concrete by (Hsu and Mo 2010). The model was then implemented in the OpenSees program to perform analysis on several cases of shear walls under seismic loading. The seismic response of reinforced ECC compared with RC shear walls under monotonic and cyclic loading, their difference in pinching effect and energy dissipation capacity were studied. The modeling results revealed that reinforced ECC shear walls can have superior seismic performance to traditional RC shear walls.

• 한국환경과학회지
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• 제16권6호
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• pp.763-769
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• 2007

This study compared the performance of a bioscrubber, a biofilter, and a combined system of bioscrubber and biofilter employed being operated at the laboratory-scale. for the removal of hydrogen sulfide. The bioscrubber maintained 100% removal of hydrogen sulfide up to inlet load of $56\;g-S/m^3{\cdot}hr$, while the removal efficiency was decreased with the increase of inlet load. The biofilter showed 100% removal efficiency up to inlet load of $126\;g-S/m^3{\cdot}h$ and the maximum elimination capacity of $126\;g\;S/m^3{\cdot}h$ for the inlet load of $224\;g-S/m^3{\cdot}h$. On the other hand, the combined system of bioscrubber and biofilter showed 100% removal for an inlet hydrogen sulfide load of up to $85\;g-S/m^3{\cdot}h$ and the maximum elimination capacity of $153\;g-S/m^3{\cdot}h$ for inlet loads of $224\;g-S/m^3{\cdot}h$.

• 한국환경과학회지
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• 제32권8호
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• pp.563-572
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• 2023

Scoria from Jeju-island (Jeju scoria) was converted into zeolitic material (Z-SA) via zeolitification using the fusion/hydrothermal method. Jeju scoria could be synthesized into Z-SA to from a surface covered with Na-A zeolite crystals, which was confirmed through an analysis of X-ray diffraction peak patterns and scanning electron microscopy images. Jeju scoria and Z-SA were employed as adsorbents to evaluate the adsorption rate and adsorption capacities for Cu²⁺ and Zn²⁺ ions. The adsorption rates and isothermal adsorption capacities could be well fitted by the pseudo-quadratic adsorption kinetics and Langmuir adsorption isotherm, respectively. The maximum adsorption capacities (q_m) of Z-SA for Cu²⁺ and Zn²⁺ ions were found to be 163.36 mg/g and 120.51 mg/g, respectively, using the Langmuir adsorption isotherm. When Z-SA is synthesized from Jeju scoria via zeolitification using the fusion/hydrothermal method, Z-SA exhibits an adsorption capacity that is more than approximately 100 times the value exhibited by Jeju scoria. As a result, the synthesized Z-SA was regarded as an effective, economic adsorbent.

• Computers and Concrete
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• 제33권5호
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• pp.509-518
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• 2024

In this study, we investigated the effect of shear-key placement on the performance of grouted connections in offshore wind-turbine structures. Considering the challenges of height control during installation, we designed and analyzed three grouted connection configurations. We compared the crack patterns and strain distribution in the shear keys under axial loading. The results indicate that the misalignment of shear keys significantly influences the ultimate load capacity of grouted connections. Notably, when the shear keys were positioned facing each other, the ultimate load decreased by approximately 15%, accompanied by the propagation of irregular cracks in the upper shear keys. Furthermore, the model with 50% misalignment in the shear-key placement exhibited the highest ultimate strength, indicating a more efficient load resistance than the reference model. This indicates that tensile-load-induced cracking and the formation of compressive struts in opposite directions significantly affect the structural integrity of grouted connections. These results demonstrate the importance of considering buckling effects in the design of grouted connections, particularly given the thin and slender nature of the inner sleeves. This study provides valuable insights into the design and analysis of offshore wind-turbine structures, highlighting the need for refined design formulas that account for shifts in shear-key placement and their structural implications.

• 청정기술
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• 제9권4호
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• pp.179-187
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• 2003

건식 흡착제를 이용한 유동층 공정에 관한 기술은 이산화탄소 처리 비용을 철강하고 효율적으로 운전될 수 있는 신기술이라고 할 수 있다. 따라서, 본 연구에서는 유동층 공정에서 건식 흡착제를 사용할 때 조업변수에 따른 이산화탄소 제어에 대해 살펴보고, 이산화탄소 흡착능과 압력강하에 대해서 고정층 공정과 비교하였으며, 활성탄, 활성 알루미나, 분자체 5A, 분자체 13X의 이산화탄소 흡착능을 각각 살펴보았다. 연구 결과, 유동층 공정의 운전을 위한 기초자료를 얻을 수 있었고, 유속이 증가할수록 유동층 공정은 상대적으로 높은 이산화탄소 흡착능과 낮은 압력강하를 지니는 것으로 나타났다. 그리고, 분자체 5A는 다른 건식 흡착제들보다 1.1~3.0배 파괴점이 늦게 나타났으며, 1.1~2.7배 높은 흡착능을 보였다.

• 한국환경농학회지
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• 제15권4호
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• pp.472-478
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• 1996

도시지역이나 공단지역과 같은 대기오염이 우려되는 지역의 가로수, 공원수, 녹화수로 널리 사용하고 있는 활엽교목류 중에서 내연성이 있다고 보고된 바 있는 가중나무, 능수버들, 양버즘나무, 은단풍나무, 은행나무를 대상으로 가스상 대기오염물질에 대한 흡수${\cdot}$흡착능력을 간편하게 비교할 수 있는 평가 인자를 알아보기 위하여 식물환경조절실에서 $SO_2$, $NO_2$, CO 가스 접촉실험을 실시하였다. 가스소비량은 가중나무가 가장 많았고 양버즘나무가 가장 적었다. 기공확산저항치는 가스소비량과 밀접한 관계를 나타내 간편하게 측정할 수 있는 정화능 지표로서의 사용가능성을 확인할 수 있었다. 그러나, 체내에 흡수축적된 전황 및 수용성황 함량과 기공밀도는 가스소비량과 다른 변화경향을 나타내 수목의 종합적인 대기오염정화능을 지표하지는 못하였다.

• 한국환경과학회지
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• 제14권1호
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• pp.61-69
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• 2005

Adsorption characteristics of toluene vapor, which is one of important source of volatile organic compounds (VOCs), by activated carbon were investigated using a fixed bed adsorption column. The operating parameters such as breakthrough curve, adsorption capacity, mass transfer zone (MTZ), and length of unused bed (LUB) were studied. The experimental results showed that the breakthrough time decreased with increasing inlet toluene concentration and gas flow rate. MTZ and LUB increased with the increase of inlet concentration, gas flow rate, and particle size of activated carbon. The adsorption capacity increased with the increase of inlet toluene concentration, while it decreased with increasing particle size. However, it was kept at constant value regardless of the increase of gas flow rate. Adsorption isotherm of toluene vapor could be represented by the Freundlich adsorption equation fairly well. From the adsorption experiments using some VOC gases such as toluene, xylene, butyl acetate. butanol and acetone, it was also found that the adsorption capacity was higher in the case of gas with higher boiling point and lower vapor pressure.

• 한국산학기술학회논문지
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• 제10권3호
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• pp.602-606
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• 2009

나트륨계 흡수용액의 이산화탄소흡수특성을 알아보기 위하여 회분식 기-액 흡수평형 반응기를 이용하여 $Na_{2}CO_{3}$ 5%, 10%, 15%, 20% 수용액에 대한 이산화탄소 흡수능 및 초기흡수속도를 측정하였으며 반응온도는 $40^{\circ}C$이었다. 또한, 알칼리염계 흡수제($KHCO_3$, $CaCO_3$, $K_{2}CO_{3}$)들의 혼합에 따른 초기흡수속도를 비교하였다. 농도에 따른 실험결과 10%의 $Na_{2}CO_{3}$에서 가장 좋은 흡수능 및 흡수속도를 보였고, 알칼리염계 흡수제들 중에서 $K_{2}CO_{3}$와 혼합할 때 흡수속도가 다소 증가되었다. $Na_{2}CO_{3}$ 5% 용액의 초기흡수속도를 개선시키기 위하여 Pz와 Pp를 각각 첨가하여 실험한 결과, 증진제를 첨가함으로써 초기흡수속도를 증가시킬 수 있었다.

• 한국산학기술학회논문지
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• 제15권5호
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• pp.3270-3278
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• 2014

도시배수시스템에서는 초기유출수(first flush)에 의한 하천오염이 심각한 문제로 대두되고 있다. 이는 강우발생시 강우에 의해 도시지역의 비점오염원들에 의해서 오염물이 하수관거로 유입되고 한정된 하수처리장의 용량으로는 제대로 처리하지 못하는 월류수에 의해 하천의 수질이 악화되기 때문이다. 대상유역으로 선정한 경기도 구리시 돌다리분구는 합류식 관거로 이루어져 있어 우기시 강우에 의한 월류가 발생할 확률이 높다. 월류에 의해 인근 왕숙천의 수질오염이 가중될 우려가 있어 적절한 처리시설의 설치가 필요하였다. 기존의 CSOs 설계에서는 강우의 최대치를 이용하여 설계가 연구되었다. 그러나, 강우의 최대치를 이용한 설계는 시설의 과다계획으로 이어져 많은 예산낭비를 초래할 수 있으며, 처리시설의 적정규모를 산정하지 못한다. 본 연구에서는 강우특성을 분석하여 매개변수들을 산정하고 이에 따른 유출분석을 실시하였다. 또한 위험도를 고려한 강우-유출분석을 이용하여 유출량을 계산하였다. 유출량을 포함한 유출특성에 의해 월류특성을 분석하였다. 왕숙천 BOD 오염농도를 기준으로 설계하기 위해 하수처리장 용량별 처리시설 요구효율을 산정하였으며 현재 하수처리장의 하수처리를 고려하여 간이 CSOs 처리시설의 효율을 71.48%로 하여 설계하였다.

• 상하수도학회지
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• 제36권4호
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• pp.229-237
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• 2022

The sewer capacity design have been based on the Huff model or the rational equation in South Korea and often failed to determine optimal capacity, resulting in frequent urban flooding or over-sizing. A time distribution of rainfall (i.e., Huff or ABM method) could be used instead of a rainfall hyetograph obtained from statistical analysis of previous rainfalls. In this study, the Huff method and the ABM method, which predict the time distribution of rain intensity, which are widely used to calculate sewage pipe drainage capacity using the SWMM, were compared with the standard rainfall intensity hyetograph of Seoul. If the rainfall duration was 30 minutes to 180 minutes, the rainfall intensity value calculated by the Huff model tended to be less than the rainfall intensity value of the standard rainfall intensity in the initial 5-10 minutes. As a result, more than 10% to 30% of under-design would be made. In addition, the rainfall intensity value calculated by the Huff model from the section excluding the initial 5-10 minutes of rainfall to the rainfall duration was calculated larger than the value using the standard rainfall intensity equation, which would result in an over-design of 10% to 30%. In the case of a relatively long rainfall duration of 360 minutes (6 hours) to 1,440 minutes (24 hours), it showed an lower rainfall intensity of 60 to 90% in the early stages of rainfall, but the problem of under-design had been solved as the rainfall duration time had elapsed. On the other hand, in the alternating block method (ABM) method, it was found that the rainfall intensity at the entire period at each assumed rainfall duration accurately matched the standard rainfall intensity hyetograph of Seoul.