• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.227-233
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• 2008

Porous concrete has large continuous voids of 20-30 % by volume, and this concrete is attractive as environmental material in Japan i.e. permeable road pavement, river bank protection with vegetation and green roof system which influence thermal environment. It is necessary to confirm the frost resistance when constructing porous concrete structure in cold region. However applicable test method and evaluation criterion of porous concrete has not defined yet. Therefore, the object of this study is to investigate the frost resistance of porous concrete and this investigation attempts to address this concern by comparing 4 kinds of specified freezing and thawing tests methods (JIS A1148 procedure A/B and RILEM CIF/CDF test) in consideration of actual environment. RILEM freeze-thaw tests are different from JIS A1148 freeze-thaw tests, which are widely adopted for evaluating the frost resistance of conventional concrete in Japan, in water absorption, cooling rate, length of freezing and thawing period, and number of freezing and thawing cycles. RILEM CIF test measures internal damage and is primarily applicable for pure frost attack. CDF test is appropriate for freeze-thaw and de-icing salt attack. JIS A1148 procedure A/B showed extremely low frost resistance of porous concrete if the large continuous voids were filled with water and the ice expansion in the large continuous voids set in during cooling. Frost resistance of porous concrete was improved by mixing coarse aggregate (G7) which particle size is smaller and fine aggregate in JIS freezing and thawing tests. RILEM CIF/CDF test showed that freeze-thaw and de-icing resistance of porous concrete was seems to be superior in that of conventional concrete.

• 한국디지털건축인테리어학회논문집
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• 제12권4호
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• pp.87-95
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• 2012

Autoclaved lightweight concrete (ALC), also known as autoclaved aerated concrete (AAC), is a lightweight, precast building material that simultaneously provides structure, insulation. ALC is a unique building material. Because of its cellular nature, it is lightweight, self-insulating, as well as sound and fireproof. ALC products include blocks, wall panels, floor and roof panels, and lintels. Recently, the use of ALC has became increasingly popular. However, ALC have high water absorption, low compressive strength and popout the origin of the low surface strength in its properties. Thus, this study is to improve the fundamental strength by controls of increasing of admixtures and chemical reactants. Admixtures make use of meta kaolin and silica fume, chemical reactants make use of sodium silicate and sodium hydroxide. From the test result, the ALC using admixtures and chemical reactants have a good fundamental properties compared with plain ALC. These good fundamental properties is caused by the admixtures and chemical reactants of ALC by the reason of the micro filling effect and chemical binding of C-S-H gel, tobermolite and quartz.

• Geomechanics and Engineering
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• 제28권3호
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• pp.209-224
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• 2022

In this study, the numerical analysis model of π-beam explosion is established to compare and analyze the failure modes of the π-beam under the action of explosive loads, thus verifying the accuracy of the numerical model. Then, based on the numerical analysis of different protection forms of π beams under explosive loads, the peak pressure of π beam under different protection conditions, the law of structural energy consumption, the damage pattern of the π beam after protection, and the protection efficiency of different protective layers was studied. The testing results indicate that the pressure peak of π beam is relatively small under the combined protection of steel plate and aluminum foam, and the peak value of pressure decays quickly along the beam longitudinal. Besides, as the longitudinal distance increases, the pressure peak attenuates most heavily on the roof's explosion-facing surface. Meanwhile, the combined protective layer has a strong energy consumption capacity, the energy consumed accounts for 90% of the three parts of the π beam (concrete, steel, and protective layer). The damaged area of π beam is relatively small under the combined protection of steel plate and aluminum foam. We also calculate the protection efficiency of π beams under different protection conditions using the maximum spalling area of concrete. The results show that the protective efficiency of the combined protective layer is 45%, demonstrating a relatively good protective ability.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.475-480
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• 2002

This study is to develop a strengthening method for slab bridges with external prestressing. There are so many different strengthening methods for damaged slab bridges, external prestressing method is the most effective, economical and durable strengthening method among them. But, its problem lies in anchoring devices, so recently, an effective anchoring method was developed and showed its improvements. In this study, a more improved method is suggested. Longitudinal tendons placed on both side of slab strengthens the whole bridge, and lateral tendons placed under the slab strengthens the middle of slab, and conveys the load at middle slab to both sides. Structural analysis for the tensile force for strengthening were analysed. Generally, 200-280tons for longitudinal tendon and 130-190 tons for lateral tendons are good enough to strengthen the damaged slab. This method has no upward roof work, so it is very convenient for installing. And no spaces under the slab are need, so it is good for shallow slabs which has less space under the slab.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.387-392
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• 2002

In many years, post-tensioning method has been used for structural reinforcement of RC structures due to easy installation and good quality control. This study presents practical application results for the effectiveness of structural post-tensioning reinforcement of the FCM bridge girders, cement silos and building girders. For the FCM bridges deflected excessively at the end of girders, for cement silos cracked vertically at silo surface and for building girders deflected due to heavy load from roof, the external post-tensioning method was used for uplifting deflected girders and closing cracks with increasing resisting capacity of the structures. It was demonstrated that all the items were rehabilitated nearly to the initial construction status according to the field test results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.363-366
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• 2003

This study is to develop a strengthening method for RC slab bridges and rigid-frame bridges with external prestressing. In this study, we design the slab specimen that have a strengthening of the DB-13 and set up the longitudinal tendons placed on both side of slab strengthens the whole bridge, and lateral tendons placed under the slab strengthens the middle of slab, and conveys the load at middle slab to both sides. Structural analysis for the tensile force for strengthening were analysed and we know that displacement and strain was improved from this test. This method has no upward roof work, so it is very convenient for installing. And no spaces under the slab are need, so it is good for shallow slabs which has less space inder the slab.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.329-332
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• 2006

To study the effect of the macroscopic TVLEM(Three Vertical Line Element Model) which is developed in 2D, a bearing wall system is selected and 2D and 3D pushover analyses are carried out. In 2D model, the participating width of a flage wall to lateral resistance is modelled based on Paulay's effective width. From the comparisons of roof displacements, 2D model which uses the effective width of flange wall has better prediction and less analysis time than 3D model which has intrinsically the full width of the flange that causes higher stiffness and strength and shorter deformation capacity than 2D model.

• 터널과지하공간
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• 제6권3호
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• pp.260-266
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• 1996

Safety concern is one of the most important parameters in the design of explosive building demolition. Laboratory experiments were performed to investigate the failure behaviour of concrete columns and the effects of protection materials. Fourteen reinforced columns with two sizes were constructed and the effects of protection materials were tested for two kinds of materials: non woven fabrics and wire net. The results showed that control of gas effects is a key to the control of flying chips. It was recommended to use both wire net and non woven fabrics as primary and secondary protection materials. Such protection method was successfully applied to the explosive demolition of 16 and 17-strory apartment buildings.and the results of a simulation on a model tunneling workings using diesel equipments are introduced. In case of typical model of tunneling face, the gas concentration of human height is about one third of roof concentration and right side half of the tunnel shows better environment than left half. NOx concentration of workings can be estimated about 0.45ppm which is much lower than permissible level(5 ppm).

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.157-157
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• 2021

2015년 파리에서 체결된 파리협정은 1850년 대비 2100년까지의 지구 평균기온 상승을 1.5℃ 이내로 제한하기 위해 5년마다 참여국에 상향된 온실가스 배출 감축 목표를 제출하게 하고, 탄소 배출 및 온도상승 저감 목표 달성을 위해 도시 내 그린인프라를 적극적으로 도입하는 등 국제사회 공동의 종합적인 이행을 예정하고 있다. 그린인프라의 유형 중 하나인 옥상녹화(Green Roof)는 기후변화 적응을 위한 도시 인프라 구축 방법의 하나로 국내에서도 많은 각광을 받고 있다. 옥상녹화(Green Roof)는 도시의 불투수층인 지붕 면적을 모두 혹은 일부 식생으로 덮어 표면층에 추가의 투수층을 조성하는 것을 지칭한다. 옥상녹화의 경우 별도의 토지면적 확보가 필요하지 않고 기존의 시설물에 추가적인 설치가 가능해 여분의 토지가 부족한 도심지의 녹지 확보를 위한 친환경적인 그린인프라로 각광받고 있다. 현재까지 옥상녹화(Green Roof) 관련 국내 연구 현황은 '옥상 녹화의 공법'을 다룬 비율이 높고 실증적인 결과를 가진 선행연구가 거의 없다. 따라서 본 연구는 동일한 조건하에 4개의 실험동을 설치하고 동질성 검사를 한 후 옥상에 설치된 재료[일반 콘크리트(Bare Concrete), 고반사 도장(High Reflective Paint), 사사(Short Bamboo), 잔디(Grass)]에 따른 건물 내 온도 변화 저감효과에 대한 분석을 수행하였다. 2020년 8월 17일부터 22일까지 측정된 지붕 표면 평균 최고온도 모니터링 결과를 일반 콘크리트 지붕과 비교했을 때. 고반사 도장 지붕의 경우 8.26℃, 옥상녹화(사사, short bamboo) 지붕의 경우 7.21℃, 옥상녹화(잔디, grass)의 경우 10.8℃ 낮은 것으로 측정되었다. 또한 실내 천정 표면 평균 온도의 경우 콘크리트 지붕과 비교하여 고반사 도장 지붕은 6.46℃, 옥상녹화(사사, short bamboo) 지붕은 13.52℃, 옥상녹화(잔디, grass)는 13.3℃ 낮은 것으로 나타났다. 본 연구결과는 옥상녹화의 온도저감 효과를 정량적으로 제시하고 있어, 향후 기후변화 대응 및 적응 전략적 수립에 기여할 수 있을 것으로 판단된다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.170-177
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• 2000

Recently many high-rise apartment buildings are constructed using the box system which is composed only of concrete walls and slabs. Commercial softwares such as ETABS used for the analysis of high-rise apartment buildings are employing the rigid diaphragm assumption for simplicity in the analysis procedure. In general the flexural stiffness of floor slabs are ignored in the analysis, This assumption may be reasonable for the estimation of seismic response of framed structures. But in the case of the box system used in the apartment buildings floor slabs has major effects on the lateral stiffness of the structure. So if the flexural stiffness of slabs in the box system is ignored the lateral stiffness may be significantly underestimated, For these reasons it is recommended to use plate elements to represent the floor slabs. In the study A typical frame structure and a box system structure are chosen as the example structure. When a 20 story frame structure is subjected to the static lateral loads the displacements of the roof are 15.33cm and 17.52cm for the cases with and without the flexural stiffness of the floor slabs. And in case of box system the roof displacement was reduced from 16.18cm to 8.61cm The model without the flexural stiffness of floor slabs turned out to elongate the natural periods of vibration accordingly.