• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6B
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• pp.551-560
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• 2010

This study presents the export of constituent transport loads through a river system. The proposed constituent transport load estimating procedure can be operated with the on-going Korean TMDL monitoring system. This study firstly discusses the use of a hydrologic simulation model (TANK) to estimate stream-flow for the 40 sub-catchments. Model parameters are estimated from 8-days intervals flow data which has been monitored by NIER since 2004. Constituent transport loads are estimated with the 7-parameter log linear model whose parameters are estimated by the minimum variance unbiased estimator. Results from Nakdong river basin reveals that the proposed procedure provides satisfactory TN, TP and SS transport load estimates. As an application, a representative load duration curve is derived to represent the overall hydrologic flux of TN, TP and SS at Nakdong river basin.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4D
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• pp.571-576
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• 2011

In general, conventional road pavements are designed under the assumption that the shear strength of geomaterials are under saturated state. In reality, however, most of the pavement geomaterials exists under the unsaturated state. To deal with this gap between saturated and unsaturated conditions, in this paper, unsaturated shear strength was estimated using the results from the triaxial compression test and soil-water characteristics curves. Then, yield loads were assessed using 2-Dimensional finite element method with the selected nonlinear elastic model and the Mohr-Coulomb yield criteria. In addition, various unsaturated condition and surface layer effects on the yield load of granular materials were identified. Therefore, the results demonstrated would provide a possibility to estimate bearing capacity of paved or unpaved roads using unsaturated soil mechanics.

• Wind and Structures
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• v.17 no.2
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• pp.227-244
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• 2013

Non-stationary extreme winds such as thunderstorm downbursts are responsible for many structural damages. This research presents a time domain approach for estimating along-wind load effects on tall buildings using multiple wind speed time history samples, which are simulated from evolutionary power spectra density (EPSD) functions of non-stationary wind fluctuations using the method developed by the authors' earlier research. The influence of transient wind loads on various responses including time-varying mean, root-mean-square value and peak factor is also studied. Furthermore, a simplified model is proposed to describe the non-stationary wind fluctuation as a uniformly modulated process with a modulation function following the time-varying mean. Finally, the probabilistic extreme response and peak factor are quantified based on the up-crossing theory of non-stationary process. As compared to the time domain response analysis using limited samples of wind record, usually one sample, the analysis using multiple samples presented in this study will provide more statistical information of responses. The time domain simulation also facilitates consideration of nonlinearities of structural and wind load characteristics over previous frequency domain analysis.

• Journal of the Korean Wood Science and Technology
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• v.43 no.5
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• pp.652-660
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• 2015

To study the bearing characteristics of glass fiber reinforced glulam for structural design, bearing strength tests were performed. Bearing loads were applied in the direction parallel to the grains, and the holes were prepared in such a way that the bolts would bear and support all the layers. The yield bearing strengths of the glass fiber reinforced glulam were found to be similar to those of the non-reinforced glulam, and were almost constant regardless of increases in bolt diameter. The ratio of the experimental yield bearing strength to the estimated bearing strength according to the suggested equation of the Korea Building Code and National Design Specification was 0.91~1.03. For the non-reinforced glulam and the sheet glass fiber reinforced plastic glulam, the maximum bearing load was measured according to the splitting fracture of specimens under bolt. The textile glass fiber reinforced glulam underwent only an embedding failure caused by the bearing load. The failure mode of reinforced glulam according to bearing load will influence the failure behavior of bolted connection, and estimating the shear yield strength of the bolted connection of the reinforced glulam is necessary, not only by using the bearing strength characteristics but also using the fracture toughness of the reinforced glulam.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.4
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• pp.120-128
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• 2001

Pollution sources and their environmental contributions were investigated to select the best management practices for the effective control of water quality. The nitrogen isotope mass ratio was determined to estimate the nitrate sources and their contribution. Sampling sites were chosen by calculating effluent loads at each watershed. Two liters each of the surface water samples were collected from four sites at Bokha river and two sites and Gwanri river. They were sequentially prepared through distillation method and analyzed using an isotope ratio mass spectrometer(IsoPrime EA). As revealed by the experimental values obtained the mass ratio values ($\delta$$^{5}$ N) of watersheds with a large amount of nonpoint sources were less than +5 an indication that the samples were influenced by chemical fertilizers. However watersheds with large amount of point sources were influenced not only by chemical fertilizers but also by animal and municipal wastes. The mass ratio values of samples generally decreased during rainy days. But during dry days the mass ratio values well-reflected the nitrate sources and the condition of watersheds. Through this study the nitrogen isotope mass ratio has been found to be useful for estimating nitrate sources and their contribution to the rural watersheds.

• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.5
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• pp.255-264
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• 2017

Dynamic numerical simulation of pile-supported slab track system embedded in a soft soil and embankment was performed. 3D model was formulated in a time domain to consider the non-linearity of soil by utilizing FLAC 3D, which is a finite difference method program. Soil non-linearity was simulated by adopting the hysteric damping model and liner elements, which could consider soil-pile interface. The long period seismic loads, Hachinohe type strong motions, were applied for estimating seismic respose of the system, Parametric study was carried out by changing subsoil layer profile, embankment height and seismic loading conditions. The most of horizontal permanent displacement was initiated by slope failure. Increase of the embedded height and thickness of the soft soil layer leads increase of member forces of PHC piles; bending moment, and axial force. Finally, basic guidelines for designing pile-supported slab track system under seismic loading are recommended based on the analysis results.

• Korean Journal of Environmental Agriculture
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• v.37 no.3
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• pp.189-196
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• 2018

BACKGROUND: Water quality management of river requires quantification of pollutant loads and implementation of measures through monitoring study, but it requires labour and costs. Therefore, many researchers are performing nonpoint source pollution analysis using computer models. However, calibration of model parameters needs observed data. Nitrogen concentration in rainfall is one of the factors to be considered when estimating the pollutant loads through application of the nonpoint source pollution model, but the default value provided by the model is used when there are no observed data. Therefore, this study aims to provide the representative nitrogen concentration of the rainfall for the administrative district ensuring rational modeling and reliable results. METHODS AND RESULTS: In this study, rainfall monitoring data from June 2015 to December 2017 were used to determine the nitrogen concentration in rainfall for each administrative district. Range of the $NO_3{^-}$ and $NH_4{^+}$ concentrations were 0.41~6.05 mg/L, 0.39~2.27 mg/L, respectively, and T-N concentration was 0.80~7.71 mg/L. Furthermore, the national average of T-N concentration in this study was $2.84{\pm}1.42mg/L$, which was similar to the national average of T-N 3.03 mg/L presented by the Ministry of Environment in 2015. Therefore, the nitrogen concentrations suggested in this study can be considered to be resonable values. CONCLUSION: The nitrogen concentrations estimated in this study showed regional differences. Therefore, when estimating the pollutant loads through application of the nonpoint source pollution model, resonable parameter estimation of nitrogen concentration in rainfall is possible by reflecting the regional characteristics.

• Land and Housing Review
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• v.12 no.2
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• pp.109-120
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• 2021

Global warming due to increased carbon dioxide is perceived as one of the factors threatening the future. Efforts are being made to reduce carbon dioxide emissions in each industry around the world. In particular, environmental loads and impacts during the life cycle of SOC structures and buildings have been quantitatively assessed through a quantitative method called Life Cycle Assessment (LCA). However, the construction sector has gone through difficulty in quantitative assessment for several reasons: 1) LCI DB is not fully established; 2) the life cycle is very long; 3) the building structures are unique. Therefore, it takes enormous effort and time to carry out LCA. Rather than estimating carbon emissions with accuracy, this study aims to present a simplified estimation model that allows owners or designers to easily estimate carbon dioxide emissions with little effort, given that rapid and rough decisions regarding environmental load reduction are to be made. This study performs the LCA using data from 25 road construction projects across the country, followed by multiple regression analyses to derive a simplified carbon estimation model (SLCA). The study also carries out a comparative analysis with values estimated by performing a typical LCA. The comparison analysis shows an error rate of less than 5% for 16 road projects.

• Journal of Environmental Impact Assessment
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• v.23 no.5
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• pp.393-405
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• 2014

In this study, the nonpoint sources were evaluated by calculating the Nadonggang basin regional water quality and nonpoint source pollution load discharged. And were selected the banks of first administration based on the results and the direction of the next administration. As a results of estimating the water quality about BOD concentration in the mid influence area in the Nakdonggang basin, it was founded that 10 sites for 'Ia' water quality level, 6 sites for 'lb' water quality level, 5 sites for 'II' water quality level, 1 sites for 'I' water quality level. The estimation of COD concentration in the mid influence area, It showed that 9 sites for 'Ib' water quality level, 6 sites for 'II' water quality level, 6 sites for 'III' water quality level, 1 site for 'IV' water quality level. The assessment of water quality made Mid influence area of Gumhogang, Nakdong Goryung, Nakdong Milyang and Namgang selected as the mid influence area of high pollution. And delivery loads of nonpoint sources were calculated for mid influence area in Nakdonggang basin(max delivery load : 17,706.7 kg/day for Gumhogang influence area). As the result of calculating NPS(nonpoint sources) delivery load and water quality at influence area in Nakdonggang basin, Gumhogang influence area was selected as an area for management priority among nonpoint sources.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.5
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• pp.453-460
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• 2005

Since late 1970s, water quality monitoring had been performed in Korea by various agencies according to their own needs and objectives. Lacking of consistency in principles, such diverse operation has been producing difficulties in management of information on water quality parameters. These difficulties resulted from the fact that the expansion of monitoring networks had been based not on systematic methodology with considerations on scientifically established planning objectives but on personal experiences and subjective judgments in locating monitoring stations. This study aimed, therefore, to develop a selection methodology for locating monitoring stations to provide various informations on water quality to satisfy various monitoring objectives such as understanding short and long term trends of water quality, monitoring violations to water quality standards, identifying external causes and sources affecting water quality changes, supporting utilization of water resources, examining short-term variations in water quality through a concentrated investigation, estimating pollution loads from each unit watershed, supporting water quality modeling, and establishing informative systems for water resources management. Also, we applied the proposed methodology and presented an improved expansion plan for water quality monitoring networks in the Han River.