• 한국환경과학회지
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• 제17권2호
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• pp.149-162
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• 2008

Aquatic and riparian vegetation of river ecosystems are very important both in ecological and management perspectives. Vegetation surveys were conducted to understand the characteristics of riparian vegetation in the mid and lower reaches of the Nakdong River, Korea. A total of 68 families and 260 species were identified at eleven survey sites. The numbers of taxa were similar to those reported in a previous survey in 1996,but the percentage of naturalized plants increased more than two times compared to that in the previous survey. Survey sites near Yangsan Bridge and Nambu Park in Yangsan showed the highest percentage of naturalized plant species. Urbanization indices of the survey sites were high at 18.8% on average. Therophytes were the most dominant plant life form at the survey sites with 39.2% of total plants identified, followed by phanerophytes (19.2%), hemicryptophytes (18.9%), aquatic plants (13.9%), cryptophytes (5.8%), and chamaephytes (3.1%). The relative composition of hemicryptophytes decreased whereas those of therophytes and chamaephytes increased compared to those in the survey in 1996. This may be due to increase in dryness of riparian soils or degradation of riparian areas. Plant compositions at sites near Jeokpo Bridge and Hwoicheon suggest that the composition and distribution of riparian vegetation are affected by land use pattern surrounding riparian areas or human accessibility to the areas.

• 대한토목학회논문집
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• 제26권5C호
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• pp.323-331
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• 2006

지반의 저항인자인 침식특성을 정량화하여 이를 세립토 지반의 세굴심 산정에 반영하는 것은 세계적인 추세이다. 이러한 노력의 일환으로 국내에서 많은 장대 해상교량이 계획 또는 시공되고 있는 서해안 지역 세립토 지반의 침식특성을 실험을 통해 분석하였다. 대상지역으로는 인천대교 현장, 강화 초지대교 현장, 환경교 현장, 군산 장항지구 등 4곳을 선정하였으며, 총 34개의 불교란시료를 채취하여 세굴률 실험을 수행하였다. 지반의 침식능을 나타내는 한계전단응력은 지반의 비배수전단 강도와 비례하는 경향을 보였으며, 점성을 가진 세립토가 세굴에 대한 저항이 보다 큰 것으로 나타났다. 실험을 통해 지역별 침식특성을 분석 및 체계화하여 서해안 지역 장대교량 건설시 보다 정확한 세굴심도 산정 및 기초 설계를 위한 기초자료로 제공하고자 한다.

• 한국물환경학회지
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• 제21권4호
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• pp.385-392
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• 2005

The control of nonpoint source pollution is essentially needed to successfully perform the Total Maximum Daily Load program. Of the various land uses in the nonpoint source, the paved areas such as a parking lot and a bridge are stormwater intensive land uses because of high imperviousness and high pollutant mass emissions. This research was performed to understand the magnitude and nature of the stormwater emissions with the purposes of quantifying stormwater pollutant concentrations and mass emission rates from a parking lot and a bridge. Two monitoring sites in Kongju city were equipped with an automatic rainfall gages and an automatic flow meter for accumulating the data such as rainfall, water quality and runoff flow rates. This paper will summarize the metal concentration changes during the storm duration and metal EMCs to characterize the concentration profiles in a parking lot and a bridge. Also a new concept, dynamic EMC, will be proposed to find the relationship between EMC and first flush effect. It can be used to determine the economical treatment criteria in best management practices.

• 대한토목학회논문집
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• 제26권2B호
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• pp.197-208
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• 2006

본 연구에서는 기개발된 교량세굴 유지관리 시스템의 현장 적용성을 검증하기 위하여 실제 교량현장에 대한 사례연구를 실시하였다. 사례연구는 강릉국도 관내의 20개 교량을 대상으로 지반조사를 포함한 현장조사, 설계 홍수량에 대한 교량세굴의 해석, 그에 따른 교량기초의 지지력 평가 및 위험도 등급 결정 그리고 교량세굴 유지관리 체계에 대한 종합적인 평가 등의 절차에 의해 진행되었다. 교량세굴 유지관리 시스템은 사례연구를 통해 세굴로 인한 교량기초의 위험도를 정량적으로 평가할 수 있는 유용한 시스템임이 검증되었으며, 효율적인 방재대책을 수립하고 홍수 시 교량의 안전을 확보할 수 있는 합리적이고 체계적인 시스템으로 제안된다.

• Korean Journal of Hydrosciences
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• 제2권
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• pp.39-59
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• 1991

Scour at bridge pier is a complicated three-dimensional problem involving interaction of fluld force on movable aid nonuniformily distributed sand grains. Although several analytical solution approaches, experimental research and field investigations for scout at piers have been conducted, no comprehensive and universally acceptable solution is so far available. Even though many methods and equations for predicting scour at piers are available in the literature, hydraulic and/or bridge design engineers are often at a loss over which method or equation is applicable for the specific bridge sites. To provide better understanding about scour phenomena and better predicting of scour at piers, intensive research is conducted through comprehensive review of published literature. Based on the research the state-of-the-art of pier scour prediction for design application is provided as a design guide for practicing engineers in this field. Recommendations for applying aggradation and degradation, contraction scour, and local scour prediction methods or equations are suggested. It is hoped that this paper may provide good information for the prediction of scour at piers.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.35-35
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• 2010

Understanding the mechanistic details of heterogeneous catalytic reactions will provide a way to tune the selectivity between various competing reaction channels. In this regard, catalytic decomposition of alcohols over the rutile $TiO_2$(110) surface as a model oxide catalyst has been studied to understand the reaction mechanism employing the temperature-programmed desorption (TPD) technique. The $TiO_2$(110) model catalyst is found to be active toward alcohol dehydration. We find that the active sites are bridge-bonded oxygen vacancies where RO-H heterolytically dissociates and binds to the vacancy to produce alkoxy (RO-) and hydroxyl (HO-). Two protons adsorbed onto the bridge-bonded oxygen atoms (-OH) readily react with each other to form a water molecule at ~500 K and desorb from the surface. The alkoxy (RO-) undergoes decomposition at higher temperatures into the corresponding alkene. Here, the overall desorption kinetics is limited by a first-order decomposition of intermediate alkoxy (RO-) species bound to the vacancy. We show that detailed analysis on the yield and the desorption temperatures as a function of the alkyl substituents provides valuable insights into the reaction mechanism. After the catalytic role of the oxygen vacancies has been established, we employed x-ray photoelectron spectroscopy to further study the surface electronic structure related to the catalytically active defective sites. The defect-related state in valence band has been related to the chemically reduced $Ti^{3+}$ defects near the surface region and are found to be closely related to the catalytic activity of the $TiO_2$(110) surface.

• 산업기술연구
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• 제28권A호
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• pp.125-132
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• 2008

As of 2003, construction waste has been produced at the level of 130,614.8 tons/day, in which the amount of waste concrete was 92,639.1 tons/day and accounted for about 66.4% of the amount of construction waste. Waste concrete is mainly produced in construction work and civil engineering work. Especially, road surface crushing method using a large amount of water requires thorough management of concrete wastewater. The aim of this study was to analyze water pollution due to concrete wastewater generated in repair of bridge deck using road surface crushing equipment and to suggest reasonable countermeasures for solve the problem. In this study, it was surveyed current conditions of produced concrete wastewater in bridge deck repair, analyzed physical features of concrete wastewater, expected effects of water pollution on inflow rivers if it is not treated, established treatment plan of water pollution by categories, and calculated capacity of each treatment process and required amount of necessary chemicals. As a result of sampling wastewater generated in field sites and testing it at a lab scale, it was revealed that the original wastewater was produced in removing concrete from bridge deck slabs using surface crushing equipment whose pH was 12.53, CODMn was 12.910mg/L, SS was 547.0mg/L, and other heavy metals were included in extremely small quantities.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.245-248
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• 2001

During the core drilling for the design of a railway bridge crossing over the inferred fault system along the river, fracture zone, extends vertically more than the bottom of borehole, filled with fault gouge was found. The safety of bridge could be threatened by the excessive subsidence or the reduced bearing capacity of bedrock, if a fault would be developed under or around the pier foundation. Thus, a close examination of the fault was required to rearrange pier locations away from the fault or to select a reinforcement method if necessary. Geophysical methods, seismic reflection method and electrical resistivity survey over the water covered area, were applied to delineate the weak zone associated with the fault system. The results of geophysical survey clearly showed a number of faults extending vertically more than 50m. Reinforcement was not desirable because of the high cost and the water contamination, etc. The pier locations were thus rearranged based on the results of geophysical surveys to avoid the undesirable situations, and additional core drillings on the rearranged pier locations were carried out. The bedrock conditions at the additional drilling sites turned out to be acceptable for the construction of piers.

• 한국안전학회지
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• 제34권5호
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• pp.103-110
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• 2019

In order to reduce the accidents occurring at construction sites, it is necessary to approach with harmonious measures considering various aspects such as systems, training, facilities, and protection equipments. Suggestion of safe construction method can be a good alternative. In the previous study, the half-depth precast deck with RC rib panel was proposed as an alternative method for safe bridge deck construction, and the performance required by the design code was verified through a four-point bending test. But the actual bridge deck is subjected to the repetitive action of the wheel load rather than the bending condition due to the four-point load. In this study, fatigue test was performed by repeating the wheel load $2{\times}10^6$ cycles to verify the safety of the half-depth precast deck with RC rib panel under actual conditions. As a result, fatigue effect due to repetition of wheel load was not significant in terms of serviceability such as crack width and deflection. In the residual strength test conducted after the fatigue test, the half-depth precast deck with RC rib panel failed by punching shear which is typical failure mode of bridge decks and the residual strength was similar to the punching strength of the RC and PSC bridge decks in spite of the fatigue effects.

• 로봇학회논문지
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• 제16권3호
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• pp.199-206
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• 2021

The robot is an effective means to perform repetitive tasks quickly and accurately. It could be more effective in dangerous environments where human is difficult to access. The construction site is a dangerous environment with a high possibility of industrial accidents where heavy work is frequently carried out at a high place. In particular, an accident in the construction site is highly likely to lead to a severe disaster. Of course, various technologies are being developed to monitor the safety of workers in construction sites and prevent accidents, but there is a limit to eliminate the risk of accidents. Therefore, it is necessary to make efforts to replace workers exposed to dangerous environments with equipment or robots that could be controlled remotely in a more active way. In this study, Remote Precise Installation System was proposed to replace the workers exposed to the risk of accident at a high place during the bridge construction. Also, the conceptual design and analytical reviews of this system were carried out. Suppose Remote Precise Installation System is developed according to the derived concept and the target performance. In that case, this system is expected to be applied as a technology that can effectively replace the workers at the bridge construction site.