• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.371-380
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• 2017

The risk-targeted seismic design concept was first included in ASCE/SEI 7-10 to address problems related to the uniform-hazard based seismic concept that has been constructed without explicitly considering probabilistic uncertainties in the collapse capacities of structures. However, this concept is not yet reflected to the current Korean building code(KBC) because of insufficient strong earthquake data occurred at the Korean peninsula and little information on the collapse capacities of structures. This study evaluates the risk-targeted seismic performance of steel ordinary concentrically braced frames(OCBFs). To do this, the collapse capacities of prototype steel OCBFs are assessed with various analysis parameters including building locations, building heights and soil conditions. The seismic hazard curves are developed using an empirical spectral shape prediction model that is capable of reflecting the characteristics of earthquake records. The collapse probabilities of the prototype steel OCBFs located at the Korean major cities are then evaluated using the risk integral concept. As a result, analysis parameters considerably influence the collapse probabilities of steel OCBFs. The collapse probabilities of taller steel OCBFs exceed the target seismic risk of 1 percent in 50 years, which the introduction of the height limitation of steel OCBFs into the future KBC should be considered.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.125-131
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• 2009

Reductive dechlorination of polychlorinated dibenzo-p-dioxins (PCDDs) and its toxicity change were predicted by the linear free energy relationship (LFER) model to assess the zero-valent iron (ZVI) and anaerobic dechlorinating bacteria (ADB) as electron donors in PCDDs dechlorination. Reductive dechlorination of PCDDs involves 256 reactions linking 76 congeners with highly variable toxicities, so is challenging to assess the overall effect of this process on the environmental impact of PCDD contamination. The Gibbs free energies of PCDDs in aqueous solution were updated to density functional theory (DFT) calculation level from thermodynamic results of literatures. All of dechlorination kinetics of PCDDs was evaluated from the linear correlation between the experimental dechlorination kinetics of PCDDs and the calculated thermodynamics of PCDDs. As a result, it was predicted that over 100 years would be taken for the complete dechlorination of octachlorinated dibenzo-p-dioxin (OCDD) to non-chlorinated compound (dibenzo-p-dioxin, DD), and the toxic equivalent quantity (TEQ) of PCDDs could increase to 10 times larger from initial TEQ with the dechlorination process. The results imply that the single reductive dechlorination using ZVI or ADB is not suitable for the treatment strategy of PCDDs contaminated soil, sediment and fly ash. This LFER approach is applicable for the prediction of dechlorination process for organohalogen compounds and for the assessment of electron donating system for treatment strategies.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.225-230
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• 2005

At present, there are several problems related with sand mat which is used as a way to accelerate consolidation settlement, to act like an underground drainage layer and to increase trafficability simultaneously. First of all, the unbalance of the demand and supply of sand is one of the biggest problems, which causes not only price rise but also delay of the term of the total construction work. Secondly, the damage of ecosystem and scenery is triggered by thoughtless sand dredging or mining. So, the need that sand mat should be replaced with a new environmentally friendly material has been increased. Fiber mat may be one of the proper materials that suits the need. Therefore, we intended to compare the drainage properties of sand mat with those of fiber mat by experimental model tests. On the basis of the test results, fiber mat took shorter period of consolidation than sand mat and the amount of settlement in the farmer showed a little bit bigger than in the latter. As a conclusion, the substitutability of sand mat with fiber mat could be placed highly in view of drainage efficiency. Furthermore, when fiber mat is used, it has an advantage that spoiled soil of the construction site or nearby site can be used for the purpose of increasing trafficability in addition to a role of drainage layer.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.133-144
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• 2009

Incheon Bridge, 18.4 km long sea-crossing bridge, will be opened to the traffic in October 2009 and this will be the new landmark of the gearing up north-east Asia as well as the largest & longest bridge of Korea. Incheon Bridge is the integrated set of several special featured bridges including a magnificent cable-stayed girder bridge which has a main span of 800 m width to cross the navigation channel in and out of the Port of Incheon. Incheon Bridge is making an epoch of long-span bridge designs thanks to the fully application of the AASHTO LRFD (load & resistance factor design) to both the superstructures and the substructures. A state-of-the-art of the geotechnologies which were applied to the Incheon Bridge construction project is introduced. The most Large-diameter drilled shafts were penetrated into the bedrock to support the colossal superstructures. The bearing capacity and deformational characteristics of the foundations were verified through the world's largest static pile load test. 8 full-scale pilot piles were tested in both offshore site and onshore area prior to the commencement of constructions. Compressible load beyond 30,000 tonf pressed a single 3 m diameter foundation pile by means of bi-directional loading method including the Osterberg cell techniques. Detailed site investigation to characterize the subsurface properties had been carried out. Geotextile tubes, tied sheet pile walls, and trestles were utilized to overcome the very large tidal difference between ebb and flow at the foreshore site. 44 circular-cell type dolphins surround the piers near the navigation channel to protect the bridge against the collision with aberrant vessels. Each dolphin structure consists of the flat sheet piled wall and infilled aggregates to absorb the collision impact. Geo-centrifugal tests were performed to evaluate the behavior of the dolphin in the seabed and to verify the numerical model for the design. Rip-rap embankments on the seabed are expected to prevent the scouring of the foundation. Prefabricated vertical drains, sand compaction piles, deep cement mixings, horizontal natural-fiber drains, and other subsidiary methods were used to improve the soft ground for the site of abutments, toll plazas, and access roads. Light-weight backfill using EPS blocks helps to reduce the earth pressure behind the abutment on the soft ground. Some kinds of reinforced earth like as MSE using geosynthetics were utilized for the ring wall of the abutment. Soil steel bridges made of corrugated steel plates and engineered backfills were constructed for the open-cut tunnel and the culvert. Diverse experiences of advanced designs and constructions from the Incheon Bridge project have been propagated by relevant engineers and it is strongly expected that significant achievements in geotechnical engineering through this project will contribute to the national development of the longspan bridge technologies remarkably.

• Journal of the Korean Geotechnical Society
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• v.30 no.3
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• pp.59-72
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• 2014

For circular rigid footings with a rough base on sand, combined vertical - moment loading capacity was studied by three-dimensional numerical modelling. Mohr-Coulomb plasticity model with the associated flow-rule was used for the soil. After comparing the results of the swipe loading method, which can construct the interaction diagram with smaller number of analyses, and those of the probe loading method, which can simulate the load-paths in the conventional load tests, it was found that both loading methods give similar results. Conventional methods based on the effective width or area concept and the results by eccentricity factor ($e_{\gamma}$) were reviewed. The results by numerical modelling of this study were compared with those of previous studies. The combined loading capacity for vertical (V) - moment (M) loading was barely affected by the internal friction angle. It was found that the effective width concept expressed in the form of eccentricity factor can be applied to circular footings. The numerical results of this study were smaller than the previous experimental results and the differences between them increased with the eccentricity and moment load. Discussions are made on the reason of the disparities between the numerical and experimental results, and the areas for further researches are mentioned.

• Journal of Environmental Health Sciences
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• v.35 no.1
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• pp.21-35
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• 2009

The Asian dust storms which originated in the deserts of Mongolia and China transported particles to Korea and led to a high concentration of atmospheric particulate matters (PM) of more than $1000{\mu}g/m^3$ throughout the country in the spring, of 2007. Public concern, in Korea, about the possible adverse effects of these dust events has increased, as these dust storms can contain various air pollutants emitted from heavily industrialized eastern China. The objectives of this study were to understand the concentration characteristics of PM as a function of particle size between the Asian dust storm episodes and non-Asian dust period and to consider the mass size distribution of PM in the Asian dust storms and their water soluble ion species on the potential, possible effects on deposition levels in the three regions (nasopharyngeal, tracheobronchial, and alveolar) of the human respiratory system. The size distribution of PM mass concentration during the Asian dust storms showed a peak in the coarse particle region due to the long-range transport of soil particles from the deserts of Mongolia and China, which was identified by HYSPLIT-4 model for backward trajectory analysis of air arriving in the sampling site of Iksan. During the non-Asian dust period, there were two different types in PM size distribution: bimodal distribution when low concentrations of $PM_{2.5}$ were observed, while unimodal distribution having a peak in fine particle region when high concentrations of $PM_{2.5}$ were showed. This unimodal distribution with high concentrations of fine particulate and secondary air pollutants such as ${SO_4}^{2-}$, ${NO_3}^-$, ${NH_4}^+$ was found to be due to the long-range transport of air pollutants from industrialized eastern China. During the Asian dust storms, the mean concentrations of PM that can be deposited in the nasopharyngeal, tracheobronchial, and alveolar region were $128.8{\mu}g/m^3$, $216.5{\mu}g/m^3$, and $89.6{\mu}g/m^3$, respectively. During the non-Asian dust period, the mean concentrations of PM that can be deposited in the nasopharyngeal, tracheobronchial, and alveolar region were $8.4{\mu}g/m^3$, $9.5{\mu}g/m^3$ and $38.5{\mu}g/m^3$, respectively.

• Structural Engineering and Mechanics
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• v.15 no.4
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• pp.381-394
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• 2003

While constructing multistorey buildings with reinforced concrete framed structures it is a common practice to provide parking space for vehicles at the ground floor level. This floor will generally consist of open frames without any infilled walls and is called an open-storey. From a post disaster damage survey carried out, it was noticed that during the January 26, 2001 Bhuj (Gujarat, India) earthquake, a large number of reinforced concrete framed buildings with open-storey at ground floor level, suffered extensive damage and in some cases catastrophic collapse. This has brought into sharp focus the need to carry out systematic studies on the seismic vulnerability of such buildings. Determination of vulnerability requires realistic structural response estimations taking into account the stochasticity in the loading and the system parameters. The stochastic finite element method can be effectively used to model the random fields while carrying out such studies. This paper presents the details of stochastic finite element analysis of a five-storey three-bay reinforced concrete framed structure with open-storey subjected to standard seismic excitation. In the present study, only the stochasticity in the system parameters is considered. The stochastic finite element method used for carrying out the analysis is based on perturbation technique. Each random field representing the stochastic geometry/material property is discretised into correlated random variables using spatial averaging technique. The uncertainties in geometry and material properties are modelled using the first two moments of the corresponding parameters. In evaluating the stochastic response, the cross-sectional area and Young' modulus are considered as independent random fields. To study the influence of correlation length of random fields, different correlation lengths are considered for random field discretisation. The spatial expectations and covariances for displacement response at any time instant are obtained as the output. The effect of open-storey is modelled by suitably considering the stiffness of infilled walls in the upper storey using cross bracing. In order to account for changes in soil conditions during strong motion earthquakes, both fixed and hinged supports are considered. The results of the stochastic finite element based seismic analysis of reinforced concrete framed structures reported in this paper demonstrate the importance of considering the effect of open-storey with appropriate support conditions to estimate the realistic response of buildings subjected to earthquakes.

• Korean journal of applied entomology
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• v.44 no.3 s.140
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• pp.189-197
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• 2005

Cellulose-digesting bacteria were isolated from hindgut of Allomyrina dichotoma (Coleoptera: Dynastidae). The bacterial isolates were identified as Yersinia sp. and Bacillus sp. The addition of the identified bacteria to diet increased growth rate of the cetoniid beetle, Protaetia brevitarsis senlensis (Coleoptera: Cetoniidae), probably by digesting cellulose nutrient contained in the oak tree sawdust diet. An additive of wheat flour at more than 10% to the sawdust diet significantly enhanced growth of P. brevitarsis senlensis. Trimmed branches of apple trees have been disposed in the apple farms and could be used for a diet component of the cetoniid beetle when the cellulose-digesting bacteria were mixed with the derived-sawdust. Resulting manure from mass rearing of P. brevitarsis senlensis contained high organic matters and trace amounts of toxic metals. When the manure were splayed on soil, it was effective as a natural compost and significantly stimulated lettuce growth. This research suggests a model technology to use cellulose-digesting bacteria to use for culturing grub, which results in natural recycles of trimmed branches in apple farms as grub diet, and to use grub manure as a natural compost.

• Journal of Agricultural Extension & Community Development
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• v.3 no.2
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• pp.197-209
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• 1996

Bangladesh that is known as the poorest country of the world has the large land of fertile soil and very good environment to live, even though we think she may be very bad to live. People being habituated to that good environment, the population explosion made the people to be starven, but the treatment has been simple support without deep analysis of the root of poverty. As the result it is general that the poverty is severer and severer in spite of continuous support. For the last century Korea changed from the country of poverty and despair to that of development and hope, to be model mid vision of under development countries including Bangladesh. At this point it is necessary to look back the way of development to help them to solve their poverty problem. That is the goal of this project, and this thesis is the result of it. It is evaluated for the 1st 5 years work of the project to apply the result to the next 5 years plan. This project had been proceeded from 1. Jul. 1990 to 30. Jun. 1995 at Chilmari area of Bangladesh, with teaching and training to wake up the mentality of the people, demonstration farming and cooperative association. It was proceeded as the Agriculture project of KDAB(Korean Development Association in Bangladesh, an NGO registered to Bangladesh) supported by Good Neighbors, KOICA and many churches and individuals. Especially the teaching and training work was proceeded as the branch of the Canaan Farmer`s School of Korea with instruction and support. After the basic survey for project, the confirmation of working place and the preparation of training facility, 10 times of long term training(3 months worse, boarding) was completed, with many times of short term training, informal training, demonstration farm, various demonstrating works. The results of the work are understanding of the not of problem by participatory observation, making plan to solve it, getting the trust from the people and beginning the practical work with the trainees for development of economy and living situation. The biggest problem of Bangladesh is being understood losing the desire to solve the poverty problem and the self-confidence to be able to do it. It is the conclusion that after solving the problem of thought and mentality, the education, technology and money can be effective for development. So the 1st 5 year project is evaluated as the basic work to analyse the root of problem, to chance mentality of people and to search income source. The next goal is to promote practical living level of people. For that it is necessary to develope die mentality of people including responsibility and self-confidence by teaching and training, to educate cooperative association and technology for economical development, to proceed integrated rural development work with economical development, educational improvement and reformation of environment. It is very important result that they decided to grow poultry for main economical source of Chilmari area, to do economical development work by joint operation of poultry through cooperative association.

• Journal of Korea Water Resources Association
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• v.39 no.11 s.172
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• pp.935-946
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• 2006

This study proposed a new procedure of sustainable water resources planning to prevent the urban streamflow depletion, based on the Heathcote's study in 1998: (1) to understand the watershed component and processes, (2) to identify and quantify problems within the watershed, (3) to set clear and specific goals, (4) to develop a list of management options, (5) to eliminate infeasible options, (6) to test the effectiveness of remaining feasible options, and (7) to develop the final options. PSR(Presure-State-Response) concept was used for the determination of indicators of PSD(Potential Streamflow Depletion; step 2) and effect equation (step 7) and composite programming for the calculation of PSD. The instreamflow requirement was proposed as clear and specific goal (step 3) and was determined by the larger of the PHABSIM's environmental flow and the drought flow. A continuous rainfall-runoff model is necessary to test the effectiveness of alternatives. It should estimate not only the exact runoff but also the effect of landuse change, reservoir, infiltration facility and so on like SWAT(Soil and Water Assessment Tool). The proposed procedure will be applied on the corresponding paper.