• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.2
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• pp.37-47
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• 2010

In order to attain enhanced seismic performance of RC bridges, premature shear failure prior to the achievement of target ductilities of the piers should be prevented. For this purpose, a reliable shear strength evaluation is required. The shear strength of an RC column subjected to a lateral force decreases with an increase in ductility. Many empirical equations for the shear strength have been proposed by many researchers. However, there are many discrepancies in the initial shear strength in the low ductility range, and in the decrease rate according to the ductility. In this study, a new empirical equation of shear strength considering the displacement ductility effect has been proposed, in which the initial shear strength equation proposed by the authors was revised on the basis of the investigation of many other researchers' test results. The resulting improvement in accuracy is confirmed by comparison with other empirical equations.

• Air Cleaning Technology
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• v.28 no.1
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• pp.29-40
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• 2015

중국의 급속한 산업화로 대기, 수질, 폐기물 등 환경오염문제가 심화, 고착화되면서 이를 개선하기 위해 중국 정부는 환경규제를 지속적으로 강화하고 있다. 또한 외국인 투자유치로 제조업 육성에 어느 정도 성공을 거둠에 따라 외국인 투자 유치와 제조업 경영활동에 있어 환경 이슈를 매우 중요시하고 있어 신규 및 사업확장에 제동이 걸리고 있다. 중국은 신규법인수 기준으로 우리나라의 최대 해외직접투자국이며, 제조업종에 대한 투자금액이 전체 투자금액의 88.3%를 차지하고 있다. 중국에 진출한 기업들은 중소기업이 전체 진출기업의 약 90%로 중국의 환경규제 강화는 중국에 진출한 우리 중소기업들에게 직접적인 영향을 미치고 있다. 중국 정부는 분야별 환경목표를 강화하고 오염물질배출 업체를 퇴출시키는 등 강력한 조치를 전개하고 있으며, 중앙 정부의 환경목표 강화 기조와 더불어 해당 지역민의 친환경에 대한 요구가 점차 커짐에 따라, 각 지방정부는 환경 관련 지역 목표 달성을 위해 업체 관리감독을 대폭 강화하고 있는 추세이다. 이러한 중국의 환경규제 강화는 진출 기업이나 진출을 준비하는 기업들의 설비투자비나 오염배출비용 부담 증가 등 상당한 리스크로 작용하고 있으며 향후에도 중국의 환경규제 강화 기조는 지속될 것으로 전망된다. 실제 중국에 진출한 기업들은 환경규제를 직접적으로 체감하고 있다. 규제집행의 강도가 눈에 띄게 높아져 엄격한 기준을 적용받고 처벌수위 역시 높아졌으며, 과거 관시를 통해 원만한 해결이 가능했다면 이제는 환경규제에 대해 원칙적이고 보수적인 공무원의 태도로 인해 관시로도 해결이 어려운 경우가 다반사이다. 또한, 주민들도 환경규제에 대한 인식수준이 높아짐에 따라 미미한 사안에도 즉각적인 반응을 보여 민원제기 사례가 빈번히 발생하고 환경안전 기준이 점점 높아짐에 따라 이에 대응하기 위해 환경안전 설비추가, 친환경연료 사용 등 추가적인 비용이 발생하고 있다. 이에 이미 진출한 기업들은 소재지 환경규제의 강화 전망 및 이로 인한 손실정도를 사전에 파악하고 다양한 옵션에서 대응전략을 마련해야 하며, 향후 중국 진출계획을 가지고 있는 기업들은 진출에 앞서 지역별로 차별화된 시장기회와 환경규제 강도 등 현지 실사를 통한 현장중심 리스크 분석을 실시해야 한다. 또한 이미 진출한 기업 및 진출예정 기업 모두 환경규제가 강화되고 있는 중국에서 사업을 하기 위해서는 법규와 기본원칙을 반드시 준수하고 규제가 더 강화될 것 이라는 기조를 인식할 필요가 있다.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.26-30
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• 2011

최근 기후변화에 따라 강우의 패턴이 변화하고 있다. 강우일수는 줄어드는 반면, 강우강도는 증가하여, 홍수로 인한 많은 피해에 직면하고 있다. 이러한 기상이변은 홍수방어시스템을 위한 수공구조물에도 많은 영향을 미친다. 수공구조물을 설계할 때, 일반적으로 강우 기록들의 통계적 특성이 정상성을 가진다고 가정한다. 하지만 최근의 강우 자료를 분석하면, 시간에 따라 평균, 분산, 왜곡도와 같은 기본 통계량이 변화하는 것을 알 수 있다. 따라서, 수공구조물의 설계를 위한 확률 강우량은 이러한 기후변화에 따른 자료의 특성을 반영할 필요가 있다. 본 연구의 목적은 강우 자료의 비정상성의 특성을 이용하여 확률강우량을 산정하는 것이다. 최근 비정상성 강우빈도해석에 대한 연구가 활발히 진행되고 있는데, 이들 연구는 대부분 목표연도까지 경향성의 기울기가 증가, 또는 일정하다고 가정한다. 하지만, 현재는 경향성이 있지만, 목표연도에는 경향성이 없을 경우도 있고, 또는 경향성이 있어도 그 기울기가 적어지는 경향을 보일 수도 있다. 본 연구에서는 현시점과 목표연도의 시점에 대한 경향성 기울기의 변화를 고려하여 비정상성 강우빈도해석을 수행하였다. 대상지점 선정은 통계적 경향성 검정, Mann-Kendall test를 이용하여 1994년(현재시점)에 경향성이 있다고 판단되는 관측지점을 대상지점으로 선정하였다. 분석 방법은 24시간 임계지속시간의 연최대강우자료를 구축하였다. 자료를 현시점까지 선형회귀식을 이용하여 잔차 계열을 산정하고, Gumbel 분포를 이용하여 확률 잔차를 산정하였다. 확률강우량을 추정하기 위해 추세요소를 산정하였다. 기울기의 증가 혹은 감소 경향을 회귀모형을 이용하여 추세요소를 산정하였고, 잔차의 확률빈도와 추세요소의 합으로 비정상상 확률강우량을 산정하였다.

• Journal of the Korea Institute of Building Construction
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• v.13 no.5
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• pp.491-497
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• 2013

The objective of the present study is to establish a straightforward mixture proportioning procedure for structural lightweight aggregate concrete (LWAC), and evaluate the selection range of the targeted dry density of concrete against the designed concrete compressive strength. In developing this procedure, mathematical models were formulated based on a nonlinear regression analysis over 347 data sets and two boundary conditions of the absolute volume and dry density of concrete. The proposed procedure demonstrated the appropriate water-to-cement ratio and dry density of concrete to achieve the designed strength decrease with the increase in volumetric ratio of coarse aggregates. This trend was more significant in all-LWAC than in sand-LWAC. Overall, the selection range of the dry density of LWAC exists within a certain range according to the designed strength, which can be obtained using the proposed procedure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.22-29
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• 2015

In this study, we tested to develop and apply structural insulation performance improvement concrete to field, which had compressive strength in 24 MPa and thermal conductivity twice as much as normal concrete. After experiment about slump and air contents, combination product of Plain and calcined diatomite powder showed reduction of slump and air contents and combination product with micro foam cell admixture, we cannot find result of slump and air contents reduction. Unit weight of combination product with insulation performance improvement materials decreased more than that of Plain. In the test of compressive strength, compressive strength of insulation performance improvement concrete decreased more than that of Plain but was content with 24 MPa. thermal conductivity of insulation performance improvement concrete tended to decrease. Freezing and thawing resistance of insulation performance improvement concrete was similar to that of Plain. In carbonation resistance test, combination product with calcined diatomite powder showed the result which was similar to that of Plain. In carbonation resistance test, combination product with micro foam cell admixture showed a increase compared to that of Plain and length variation of combination product generally increased.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.19-26
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• 2020

This study aimed to develop non-sintered cement that could replace portland cement which emits large amount of carbon dioxide during firing process. For this purpose, ground granulated blast furnace slag, type c fly ash and slaked lime were used. In addition, through the experimental results, the characteristics of the non-sintered cement binders according to the mixing ratios will be identified, and the utilization plans for the precast concrete products will be presented. In this experiment, non-sintered cement binders using industrial by-products were prepared to compare the flexural strength and compressive strength of each of the 3, 7 and 28 days. As a result, the results satisfy the KS of the target product proposed in this study. Therefore, this study presents the possibility of using precast concrete products by developing non-sintered cement binders using industrial by-products.

• Journal of the Korean Wood Science and Technology
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• v.40 no.1
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• pp.38-43
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• 2012

Sound absorption capability and mechanical properties such as MOE and MOR in bending of miscanthus particle based board were estimated by the two microphone transfer function method and three point bending method, respectively. The results are summarized as follows: The sound absorption coefficients of miscanthus particle based board was higher than those of commercial gypsum board which is well used as sound absorbing barrier. The MOR and MOE of miscanthus particle based board increased with increasing of board density. The sound absorption coefficients of miscanthus particle based board were 50~80% in the frequency range of about 1~2.5 Khz. In entire frequency range, those value increased with target board density decreasing.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.78-86
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• 2014

The purpose of this study is the displacement and velocity dependence evaluation of I type and S type metallic dampers. For this purpose, 12 metallic damper specimens are prepared and dependence test are performed. Test variables are strut type, displacement and velocity dependence. From the evaluation results of dependence tests, number of cycles are fully exceeded than minimum 5 cycles described in ASCE 7-10. According to displacement dependence test results, larger target displacement (50mm) shows lower cyclic numbers and cumulated energy dissipated area than lower target displacement (25mm). Also it show higher strength and early failure than short target displacement. In velocity dependence evaluation, fast target velocity (60mm/sec) shows lower cyclic numbers and cumulated energy dissipated area than target velocity (40mm/sec). As a results of basic properties, dependence evaluation and cumulated energy dissipated area evaluation, dependence capacity of S type metallic damper is far superior than I type.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.157-166
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• 2008

To investigate the relationship between compressive strength ($q_u$) of Lightweight Air-mixed soil (LAS) and its physical deformation coefficient ($E_{50}$), a series of unconfined compressive tests have been performed on specimens of LAS according to various dredged soil types by percentage of sand, silt and clay. From the results it was found that the cement content ($C_i$) and unit weight (${\gamma}_m$) are most influence factors on strength, and percentage of sand, silt, clay by grain size analysis (KS F2302) have more effect on compressive strength than other physical properties of soil. It was also found that the rate of strength (a) increases with curing time, but it reduces with the increase of percentage of clay ($C_%$).

• Journal of Climate Change Research
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• v.4 no.2
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• pp.159-175
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• 2013

Emission reduction targets to respond to climate change have been discussed and set locally, nationally and globally. After Korean government set the national target in 2009, 16 metropolitan cities established voluntary emission reduction targets by 2020. This study review and compare historical greenhouse gas emissions, reduction target by 2020 and strategies in 16 metropolitan cities. Most cities chose a consumption-based inventory approach. Some cities set the reduction target excluding land use change and forestry (LUCF) at 30% against business-as-usual by 2020, while others set the absolute reduction target against past year including LUCF. The stringency of reduction target in metropolitan cities was evaluated differently according to the comparative indicators such as the targets against BAU or past year and per capita emission, etc. Key mitigation sectors were different across metropolitan cities. It is suggested that national government share detailed raw data for metropolitan cities' emission inventory with the local government. Using advanced mitigation model and two types' target based on BAU and historical year and integrating local government's climate change plan with its energy plan are also required.