• 환경영향평가
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• 제11권1호
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• pp.25-36
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• 2002

The purpose of this study is to assess the environmental carrying capacity of Chongju City for the environmental management and the urban growth management. The urban environmental carrying capacity assessment of the city by the index of ecological footprint(EF), shows that the ecosystem of the city has been overloaded and most of the deficiencies has come from outside of the city. The EF index, the area of land per capita required for production and consumption in the city, was 1.731 ha per capita in 1989 and 1.901 ha per capita in 1999. On the other side, the ecologically productive land is 0.0175 ha per capita. It means that every citizen owes 1.88 ha per capita to the ecosystem in 1999. The land consumption of the city has increased by 0.1705 ha per capita during the last 10 years. The capacity of infrastructure and the service supply estimated by the Onishi model does not exceed the demand of the city in 1999. But the rapidly increasing population and fast urban growth need the expansion of the capacity. The water supply capacity of the city appears to be sufficient in 1999, but the water supply demand will increase in the future. The capacity of sewage treatment facilities seems to be sufficient, but the higher level of sewage treatment facilities should be adopted for the improvement of water quality as the generation of sewage will increase and its characteristics will also make the wastewater treatment difficult. Due to the decrease of solid waste generated, the land fill capacity for solid waste disposal is not insufficient at present, but the capacity will be saturated in the near future. Therefore, the scientific management system of solid wastes should be introduced. The air quality of the city meets both the national air quality standard and WHO recommendation standard, but the strong regulation and control of automobile emission gas such as CO, $CO_2$, NOx and HC is required for clean air.

• 대한수학회지
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• 제58권5호
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• pp.1227-1237
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• 2021

This paper is concerned with a reaction-diffusion logistic model. In [17], Lou observed that a heterogeneous environment with diffusion makes the total biomass greater than the total carrying capacity. Regarding the ratio of biomass to carrying capacity, Ni [10] raised a conjecture that the ratio has a upper bound depending only on the spatial dimension. For the one-dimensional case, Bai, He, and Li [1] proved that the optimal upper bound is 3. Recently, Inoue and Kuto [13] showed that the supremum of the ratio is infinity when the domain is a multi-dimensional ball. In this paper, we generalized the result of [13] to an arbitrary smooth bounded domain in ℝⁿ, n ≥ 2. We use the sub-solution and super-solution method. The idea of the proof is essentially the same as the proof of [13] but we have improved the construction of sub-solutions. This is the complete answer to the conjecture of Ni.

• Structural Engineering and Mechanics
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• 제82권1호
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• pp.81-92
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• 2022

Ultra-high performance fiber reinforced concrete (UHPFRC) is a composite building material with high ductility, fatigue resistance, fracture toughness, durability, and energy absorption capacity. The aim of this study is to develop a nonlinear finite element model that can simulate the response of the UHPFRC beam exposed to impact loads. A nonlinear finite element model was developed in ABAQUS to simulate the real response of UHPFRC beams. The numerical results showed that the model was highly successful to capture the experimental results of selected beams from the literature. A parametric study was carried out to investigate the effects of reinforcement ratio and impact velocity on the response of the UHPFRC beam in terms of midpoint displacement, impact load value, and residual load-carrying capacity. In the parametric study, the nonlinear analysis was performed in two steps for 12 different finite element models. In the first step, dynamic analysis was performed to monitor the response of the UHPFRC beam under impact loads. In the second step, static analysis was conducted to determine the residual load-carrying capacity of the beams. The parametric study has shown that the reinforcement ratio and the impact velocity affect maximum and residual displacement value substantially.

• 한국수산과학회지
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• 제35권4호
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• pp.386-394
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• 2002

패류 양식 해역의 서식 환경과 양식 생물간의 상호 관계를 파악하고 지속적인 생산 방안을 위하여 굴 성장과 관련된 생리 대사 과정인 섭이, 소화, 배설, 호홉 등의 제 인자를 수식화하여 기존에 개발된 생태계모델 (EUTRP2)에 연계하여 환경용량 산정 모델을 구축하였다. 구축된 모델이 굴 성장과 서식환경과의 상호관계를 재현함에 있어 타당성 여부를 검정한 결과, 굴 성장에 따른 서식환경 중 식물플랑크톤 현존량이 감소하고 영양염 농도가 증가하는것으로 보아, 패류양식해역의 생태계 환경관리를 위한 도구로 사용할 수 있는 것으로 나타났다. 그리고, 생태계 구성 요소에 영향을 미치는 생물 인자에 대한 민감도 분석 결과, 구성 요소들은 식물플랑크톤의 증식 속도와 높은 민감도를 보였고, 굴 성장의 경우 동물플랑크톤 최대 섭이 속도와는 민감도가 낮은 반면, 식물플랑크톤 증식 속도, 사멸 속도와 굴의 먹이 흡수 효율에 매우 민감하였다.

• Geomechanics and Engineering
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• 제10권5호
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• pp.599-615
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• 2016

The present research presents experimental and finite element studies to investigate the behavior of piled raft-tunnel system in a sandy soil. In the experimental work, a small scale model was tested in a sand box with load applied vertically to the raft through a hydraulic jack. Five configurations of piles were tested in the laboratory. The effects of pile length (L), number of piles in the group and the clearance distance between pile tip and top of tunnel surface (H) on the load carrying capacity of the piled raft-tunnel system are investigated. The load sharing percent between piles and rafts are included in the load-settlement presentation. The experimental work on piled raft-tunnel system yielded that all piles in the group carry the same fraction of load. The load carrying capacity of the piled raft-tunnel model was increased with increasing (L) for variable (H) distances and decreased with increasing (H) for constant pile lengths. The total load carrying capacity of the piled raft-tunnel model decreases with decreasing number of piles in the group. The total load carrying capacity of the piles relative to the total applied load (piles share) increases with increasing (L) and the number of piles in the group. The increase in (L/H) ratio for variable (H) distance and number of piles leads to an increase in piles share. ANSYS finite element program is used to model and analyze the piled raft-tunnel system. A three dimensional analysis with elastoplastic soil model is carried out. The obtained results revealed that the finite element method and the experimental modeling are rationally agreed.

• Structural Engineering and Mechanics
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• 제59권4호
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• pp.703-718
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• 2016

Masonry arch bridges present a large segment of Iranian railway bridge stock. The ever increasing trend in traffic requires constant health monitoring of such structures to determine their load carrying capacity and life expectancy. In this respect, the performance of one of the oldest masonry arch bridges of Iranian railway network is assessed through field tests. Having a total of 11 sensors mounted on the bridge, dynamic tests are carried out on the bridge to study the response of bridge to test train, which is consist of two 6-axle locomotives and two 4-axle freight wagons. Finite element model of the bridge is developed and calibrated by comparing experimental and analytical mid-span deflection, and verified by comparing experimental and analytical natural frequencies. Analytical model is then used to assess the possibility of increasing the allowable axle load of the bridge to 25 tons. Fatigue life expectancy of the bridge is also assessed in permissible limit state. Results of F.E. model suggest an adequacy factor of 3.57 for an axle load of 25 tons. Remaining fatigue life of Veresk is also calculated and shown that a 0.2% decrease will be experienced, if the axle load is increased from 20 tons to 25 tons.

• 한국전산구조공학회논문집
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• 제30권1호
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• pp.55-61
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• 2017

최근 콘크리트 궤도 슬래브 하면과 교량 바닥판 사이에 저마찰 슬라이드층을 형성하는 궤도 시스템인 슬라이딩 궤도와 관련된 연구가 활발히 진행되고 있다. 본 연구에서는 슬라이딩 궤도에서 열차 주행에 따른 횡방향 하중을 저항하기 위해 설치되는 횡방향 지지 콘크리트 블록의 전단 내하력에 대한 연구를 수행하였다. 횡방향 지지 콘크리트 블록의 전단 내하력 산정을 위해 타설경계면에서의 콘크리트 마찰 및 철근의 다월 거동을 고려한 산정 기법을 개발하다. 제안된 산정 기법은 기존의 실험에서 측정된 전단 내하력을 13~23% 정도 보수적으로 예측하는 것으로 나타났다. 이는 균열면 골재 맞물림 효과를 무시한 것에 따른 것으로, 현장에서의 타설경계면 상태가 불확실한 것을 고려할 때 횡방향 지지 콘크리트 블록에 대한 안전측 설계를 위해 제안된 산정 기법이 합리적인 것으로 판단된다. 제안된 전단 내하력 산정 기법을 토대로 횡방향 지지 콘크리트 블록에 대한 설계 방안을 마련하였다.

• 한국산림과학회지
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• 제99권4호
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• pp.508-516
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• 2010

2007년 국립공원 입장료 폐지 후 한라산국립공원 탐방객이 지속적으로 증가함에 따라 적정 이용 수준에 대한 관심이 높아졌다. 본 연구는 한라산국립공원의 적정 수용력 관리에 필요한 영향지표 및 평가기준과 이를 활용할 수 있는 수용력 지표관리프로그램 개발을 위해 수행되었다. 전문가 설문조사를 통해 8개의 영향지표(계곡수질, 탐방객 수, 탐방로 훼손정도, 혼잡 등)를 선정하였으며, 각 영향지표별 현지 조사를 통해 실험적 평가기준을 제시하였다. VERP 모델을 이용한 수용력 지표관리프로그램은 자원 및 탐방행태 변화에 대한 과학적인 분석과 국립공원의 지속 가능성을 평가하는데 효율적일 것이다. 또한, 통합 데이터 관리 및 활용으로 데이터를 체계적으로 관리하여 합리적인 의사결정을 내릴 수 있는 업무수행을 지원한다.

• Earthquakes and Structures
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• 제17권2호
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• pp.221-232
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• 2019

Material non-linearity of Reinforced Concrete (RC) framed structures is studied by modelling concrete using the Concrete Damage Plasticity (CDP) theory. The stress-strain data of concrete in compression is modelled using the Hsu model. The structures are analyzed using a finite element approach by modelling them in ABAQUS / CAE. Single bay single storey RC frames, designed according to Indian Standard (IS):456:2000 and IS:13920:2016 are considered for assessing their maximum load carrying capacity and failure behavior under the influence of gravity loads and lateral loads. It is found that the CDP model is effective in predicting the failure behaviors of RC frame structures. Under the influence of the lateral load, the structure designed according to IS:13920 had a higher load carrying capacity when compared with the structure designed according to IS:456. Ultra High Performance Fiber Reinforced Concrete (UHPFRC) strip is used for strengthening the columns and beam column joints of the RC frame individually against lateral loads. 10mm and 20mm thick strips are adopted for the numerical simulation of RC column and beam-column joint. Results obtained from the study indicated that UHPFRC with two different thickness strips acts as a very good strengthening material in increasing the load carrying capacity of columns and beam-column joint by more than 5%. UHPFRC also improved the performance of the RC frames against lateral loads with an increase of more than 3.5% with the two different strips adopted. 20 mm thick strip is found to be an ideal size to enhance the load carrying capacity of the columns and beam-column joints. Among the strengthening locations adopted in the study, column strengthening is found to be more efficient when compared with the beam column joint strengthening.

• 한국환경생태학회지
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• 제15권3호
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• pp.257-266
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• 2001

국립공원에서 가장 보편화된 이용공간이며, 생태적 공간에 대한 이용압력이 일차적으로 작용하는 등산로 주변의 환경피해도를 바탕으로 국립공원의 수용능력을 추정하였다. 북한산국립공원의 22개 법정 등산로에 대한 환경피해도와 통행량 및 통행패턴을 조사하고. 등산로 폭과 통행량 두 변수간의 상관관계 및 회귀분석을 통하여 적정 탐방객 수를 추출하는 모형을 수립하였다. 그리고 유효 입장객 수와 등산로 구간별 평균통행량을 고려하여 수용능력 추정식을 고안하였다. 수용능력 추정식을 적용하여 북한산국립공원의 적정 수용능력을 추정한 결과. 등산로 노폭을 2.2m로 유지하는 관리목표하에서는 연간 최대 적정 수용능력을 300만 명 이하로 유지하는 것이 바람직하며 보존강도를 높여 등산로 노폭을 2.0m 수준으로 관리하고자 할 경우에는 연간 최대 200만 명 이하를 유지해야 하는 것으로 나타났다