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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of The Korean Society of Civil Engineers
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Journal DOI :
Korean Society of Civil Engeneers
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Volume & Issues
Volume 19, Issue 3_6 - Nov 1999
Volume 19, Issue 2_6 - Nov 1999
Volume 19, Issue 1_6 - Nov 1999
Volume 19, Issue 3_5 - Sep 1999
Volume 19, Issue 2_5 - Sep 1999
Volume 19, Issue 1_5 - Sep 1999
Volume 19, Issue 3_4 - Jul 1999
Volume 19, Issue 2_4 - Jul 1999
Volume 19, Issue 1_4 - Jul 1999
Volume 19, Issue 3_3 - May 1999
Volume 19, Issue 2_3 - May 1999
Volume 19, Issue 1_3 - May 1999
Volume 19, Issue 3_2 - Mar 1999
Volume 19, Issue 2_2 - Mar 1999
Volume 19, Issue 1_2 - Mar 1999
Volume 19, Issue 3_1 - Jan 1999
Volume 19, Issue 2_1 - Jan 1999
Volume 19, Issue 1_1 - Jan 1999
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The Characteristics of Scour Depth Variation around Multiple Piers in a Curved Channel
Park, Sung-Sik ; Song, Jai-Woo ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 255~255
This study is to compare and analyse the variation of maximum scour depth of the single pier and multiple piers from
laboratory flume experiments. They were located in the center of straight channel and the
outer section of curved channel in which the maximum transverse bed slope was generated. The range of scour effect among multiple piers was analysed considering the flow characteristics of a curved channel. The results showed that there was no the variation of maximum scour depth if its longitudinal spacing were 21b(pier diameter) in a straight channel and 18b in a curved channel. The first pier among multiple ones had the maximum effect which was increased maximum scour depth if its longitudinal spacing were 3b both in a straight and in a curved channel. On the other hand, the second and the third pier among those had the maximum effect which was decreased maximum scour depth if their longitudinal spacing were 6b. The variation of maximum scour depth was greater in a straight channel than in a curved channel.
Field Application of Design Formula for Local Scour around a Bridge Pier - Prediction of Temporal Variation of Local Scour -
Yoon, Sung-Bum ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 265~265
As a fundamental research on the realistic estimation of scour depth for a real flood event, a simple empirical formula is proposed to predict the development of clear-water local scour process around a circular pier for steady flow. The formula is obtained using the experimental data reported earlier through the nondimensionalization of scour depths by equilibrium scour depth. It is shown that the scour depth develops with logarithmic function of time. The scour process predicted by the present formula shows a good agreement with those of the existing experimental data.
Analysis of the Bedform Variation in a Meandering Erodible Channel Using the Model FLUVIAL-12
Lee, Jong-Seok ; Cha, Young-Kee ; Kim, Yi-Hyeon ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 275~275
This study includes the investigation on flow characteristics and the resulting bedform variation due to the sediment transport during the time of maximum flood and the base runoff at the upper watershed of Han River. The analyses were performed applying the FLUVIAL-12 to the project site, in which the finite difference method was adopted to solve the continuity and momentum equations in 1-D unsteady flow, including the equations for the sediment transport. The stage-discharge relationship determined from precipitation of 8 hr. duration was used as input data for it. The modeling results show that for the well-developed meandering channel a triangular bedform develops at an intersection of two points: the end point of a straight reach and the initial point of a curved reach, while a trapezoidal bedform develops at the middle reach. It was attributed to the 'distance lag' resulting from the difference between the centerline of the theoretical flow and the thalweg of the real flow. Even through the model used in this study could not simulate completely the dynamics of flow and the resulting bedform variation occurring in nature, it appears that the useful information could be obtained from it in case of engineering purpose, in which the simple and approximate but fart estimations are required frequently.
Fractal Dimension of Stream Networks and Mainstream Length
Jeon, Min-Woo ; Song, Jai-Woo ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 285~285
Fractal dimensions of mainstream length and stream networks are derived from the Horton's laws of network composition and the empirical relationship between stream length and stream area. When the stream order gets infinitely higher order with higher and higher resolution, the fractal dimension converges to unity in the case of smaller stream length ratio
and deviates 2.0 in the case of higher
, while fractal dimension rapidly increases with decreasing stream order. The parameter
indicating relationship between the mainstream length and the mean stream area of order u can be described as a function of the stream length ratio
and the stream area ratio
representing relationship between the number of streams and the mean stream area of order u can be derived as a function of the bifurcation ratio
and the stream area ratio
. The Proposed method can be an efficient tool to yield the fractal dimension of mainstream length from
and of stream networks from
An Experimental Study on the Flow Characteristics in Curved Channel Junctions
Baek, Chang-Sik ; Yoon, Sei-Eui ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 297~297
The curved channel of total angle
with junction located in bend angle
outside bank was used to analyze the characteristics of junction flow. Experiments are conducted by changing the discharge ratios, the junction angle, and the gradient of trib utary channel. The influence on the increasing of water depth was observed in the order of the discharge ratio, the junction angle and the gradient of tributary channel. The water depth ratios increase as the junction angles increase for same discharge ratio. The depth ratio between upstream and downstream of junction was observed with the value of 1.5 with critical depth condition at downstream of junction. As the discharges of main channel without junction increased, the thread of maximum velocity moved to outer bank, and as the disharge ratio and junction angles increased, that moved to inner bank. The results of this study could be useful and practical for the design of channel bend junction.
Numerical Analysis of Water Hammer Phenomena in 1st and 2nd Stages of Seoul Metropolitan Wide Area Water Distribution Network
Park, Nam-Sik ; Kim, Sang-Hyun ; Ryu, Joong-Kwon ; Kang, Joo-Young ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 309~309
Analysis of water hammer phenomena in pipe networks involves difficulties that are not experienced in single pipes. We have simulated water hammer phenomena in the first Stage and the second Stage of Seoul Metropolitan Wide Area Water Distribution Network considering difficulties associated with water hammer analysis in pipe networks. Friction coefficients of pipe networks are usually not known accurately. We estimate these values by comparing observed and computed hydraulic heads. Uncertainty in boundary conditions is examined by using specified discharge and specified head conditions. Large differences are observed. Skeletonization of pipe networks also has a significant impact on simulation results. For reliable analysis it is essential to use realistic boundary conditions and to avoid excessive simplifications of pipe networks.
Mitigation for the Anti-function of Development in Caused by Saemangeum Reclamation
Shin, Moon-Seup ; Tetsuo, Yanagi ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 317~317
The purpose of this study is to explore the method which can minimizes the anti-function of development in the coastal region of Saemangeum area. The changes of tidal current and residual flow after the construction of dike and submerged breakwater are investigated. A numerical simulation of dispersion of larvae in the Saemangeum coastal region is attempted. The pattern of larvae dispersion is compared between the undesirable effect before and after the construction of submerged breakwater to investigate the possibility of mitigation in the fisheries ground. The dispersion range of larvae were dispersed within the range of 10 km before and 4 km after the construction of submerged breakwater in Piung island. The dispersion range of larvae released from the coastal region of Yami island is about 12 km before the construction of submerged breakwater, while 4.5 km after the construction of submerged breakwater. However most of larvae stay in the inner part of submerged breakwater one day after the releasing after the construction of submerged breakwater. Therefore, the construction of submerged breakwater greatly influences to the prevention of larvae dispersion. If larvae stay within submerged breakwater for a long time, new ecosystem and fishing ground might be formed, larvaes will mitigate in a wide region. Hexagrammos octogrammus spawn demersal egg. It is desirable that demersal egg moves from the release point to near point. Therefore, the small scale dispersion of larvae is good for their recruitment, survival. If larvae stay within submerged breakwater for a long time, new ecosystem and fishing ground might be formed. Therefore, the construction of submerged breakwater could minmize and compensate the negative impacts on the marine environment and ecosystem caused by the Saemangeum reclamation. The construction of submerged breakwater is the possibility of mitigation in the fisheries ground.
Prediction of Wave Height and Longshore Current due to the Random Waves near Surfzone
Lee, Cheol-Eung ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 329~329
The cross-shore variations of surf zone longshore currents and wave heights due to incident random waves are analyzed in this paper. In random wave model. the local reflection coefficient is also evaluated by a new method which is presented for separating the incident and reflected wave height from RMS wave heights. From comparisons of the predicted results with laboratory data and field data, it is found that the variations of random wave height and mean surface displacement near surf zone are accurately predicted by the present random wave model. Also, it is confirmed that the present wave model may be more applicable and accurate for prediction of the local reflection coefficient than the existing models through comparisons with measured data. In addition, the transport equation for mean turbulent kinetic energy created by wave breaking are introduced into the mean longshore current model to examine the contribution of the turbulent momentum transport. It is found that the longshore current model including the effect of turbulent momentum transport may correctly predict the surf zone longshore currents for random waves through comparison with the measured data. In particular, the predictive accuracy of the longshore current model for evaluating the current velocity may be improved by consideration of the effect of turbulent momentum transport on a barred beach rather than a uniformly sloping beach. However, further studies should be continued since there are still some differences between the predicted results and measured data on a barred profile.
Effect of Higher-Order Bottom Variation Terms on the Refraction of Water Waves
Lee, Chang-Hoon ; Yoon, Sung-Bum ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 345~345
It is investigated how the refraction of water waves are affected by the higher-order bottom effect terms proportional to the square of bottom slope and to the bottom curvature in the extended mild-slope equations. Two cases of waves propagating over a circular shoal and over a circular hollow are tested numerically. Numerical results are analyzed using the eikonal equation reduced from the wave equations and the wave ray tracing technique. It is found that the higher-order bottom effect terms change the wavelength resulting in the change of refraction of waves over a variable depth. In the case of waves over a circular shoal, the higher-order bottom effects increase the wavelength along the rim of shoal more than near the center of shoal, and the degree of wave refraction increases. However, the discontinuity of higher-order bottom effects along the rim of shoal weakens the increase of refraction and spreads the foci of wave rays. As a result, the focusing of wave energy behind the shoal decreases. On the contrary, in the case of waves over a circular hollow, the higher-order bottom effects decrease the wavelength near the center of the hollow in comparison with the cases of neglecting higher-order terms. Consequently, the degree of wave refraction decreases, and the spreading of wave energy behind the hollow decreases.
Experimental Study for The Hydraulic Performance of Octopus - A New Type of Armor Block
Hong, Kun-Hee ; Chun, In-Sik ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 359~359
In the determination of armoring and wave dissipating blocks used in rubble mound breakwater types, the performance and stability of block layer are primarily considered, but the economic aspects for all construction process should be also closely analyzed. It is often the case that the installation fee exceeds the manufacturing and fabrication costs. Expecting that the sort of bigger blocks is more beneficient in saving overall construction cost, a new type named Octopus (OTP), which is more suitable for regular placements, is devised here. Hydraulic experiments are performed for various layers and arrays of OTP along with existing TTP. The stability and armoring effect of the OTP appear to be very nice, but overtopping rates somewhat increase compared to the case of TTP. Several measures are experimented to lower the overtopping rates, and the capping the front top of breakwater with the random placement of the OTP is shown to be very effective.
Tidal Hydrodynamic Analysis for the Yellow Sea and East China Sea by Using a Three-Dimensional Finite Element Model
Suh, Seung-Won ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 375~375
Unstructured fine grid systems of a linear three-dimensional finite element model are applied to figure out tidal hydrodynamic analysis for the Yellow Sea and the East China Sea. Resolving of fine grids within 20 meters of shallow depth directly affects to the tide amplification of the Kyung-ki Bay and tidal systems along the west coast of Korea. Model results of cartesian coordinate based on UTM projection agree well with tidal charts. Also tidal currents are in good agreement with observed data within
of current amplification and
of phase for the
Shallow Tides Generation in the Yellow Sea by Using a Nonlinear Three-Dimensional Harmonic Finite Element Model
Suh, Seung-Won ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 389~389
A three-dimensional finite element model has been applied to simulate nonlinear tides due to the shallow depth of the west coast of Korea. Model results for astronomical tides through nonlinear interactions are better than that of linear model and show realistic tidal amplitudes in the Bohai Bay. Shallow water tides are generated by iterative computations of bottom stress and nonlinear terms interaction. Computed results show up to 15cm of amplitude of
for the Kyung-ki Bay and the Seohan Bay. Tidal residual currents are also generated and show coastal currents and well developed 5 cm/sec eddies around the Cheju Island with satisfaction owing to the application of fine grid system of 500 meters spacing which can effectively resolve complex coasts.
Characteristics of Tsunami Behaviors in the East Sea
Lee, Ho-Jun ; Fumihiko, Imamura ; Nobuo, Shuto ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 401~401
The behavior of tsunami in the East Sea is simulated by a numerical model based on the linear long wave theory. The tsunami events studied are 1964 Niigata. 1983 Nihonkai Chubu, 1993 Hokkaido Nansei Oki earthquake tsunami events and an imaginary tsunami off Sakata of the Japanese western coast. Tsunami energy propagation is computed and schematically presented. The lens effects of Yamato rise are confirmed through the comparison of tsunami heights along the Korean eastern coast simulated for both cases of including and excluding the effects of Yamato rise. The amounts of radiated and trapped tsunami energies, due to the variation of epicenter location of imaginary tsunami in offshore direction near continental shelf, are evaluated and the characteristic variation of energy propagation associate with the location of epicenter is investigated. This explains that locations of tsunami sources give considerable effects on the refraction as well as the energy radiation pattern over Yamato rise.
Relatively Safe Biomass Cultivation in Denitrification Process
Oh, Jei-Il ; Park, Jong-Moon ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 411~411
Increase in contamination of drinking water sources with nitrate ion has focused attention on biological processes which can effectively remove nitrate from contaminated waters. However, due to possibility of pathogen contamination, microorganisms used in drinking water treatment should be different from those in wastewater treatment. In this research, a new method was introduced to cultivate sanitarily safe microorganisms from soil source which were used as an inoculum in denitrification SBR system and new parameters were suggested to determine relative safety of cultivated biomass: 1) MPN(coliform bacteria)/MLVSS, 2) MPN(E. coli)/MLVSS. Both parameters were most significantly influenced by the kind of supplied carbon sources. However new parameters were not intended to indicate non-pathogenic bacterial seeding, rather than suggested to show the relative safety of a denitrifying biomass in terms of coliforms and E. coli.
Nitrite Accumulation in Activated Sludge Denitrification: Effects of Dissolved Oxygen, Substrate Limitation and pH
Oh, Jei-Il ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 419~419
Nitrite accumulation in activated sludge denitrification was investigated with various factors; DO, substrate limitation and pH. When DO levels in mixed liquor were changed from 0.1mg/L to 2.0mg/L, nitrite was not accumulated during activated sludge denitrification showing that oxygen repressed both nitrate and nitrite reductases evenly. While carbon substrate (acetate) was reduced to the C:N ratio of 1.1:1, nitrite was accumulated during acetate-limited denitrification. This can be explained by nitrate respiration outcompeting nitrite respiration for limited acetate electrons. In contrast to neutral pH(=7) condition, alkalinity pH(=8) condition demonstrated considerable nitrite accumulation during denitrification, even though the specific denitrification rates in both pH conditions were similar.
Nitrogen Removal from Household Wastewater Using Intermittently Aerated Membrane Bioreactor
Na, You-Me ; Ahn, Kyu-Hong ; Yeom, Ick-Tae ; Khim, Jee-Hyeong ;
Journal of The Korean Society of Civil Engineers, volume 19, issue 2_3, 1999, Pages 427~427
Membrane bioreactor using submerged hollow fiber membrane was applied in laboratory scale to treat Household wastewater including toilet flushing water. The bioreactor was intermittently aerated to alternate anoxic/oxic conditions while membrane filtration occurred during the aeration period in suction mode. The air bubble generated during the aeration period served two purposes: 1) supplying oxygen to the mixed liquor, 2) washing the membrane by creating turbulent flow around the membrane surface. After operating for about 100 days, the initial flux and suction pressure were maintained almost constant at 0.01m/hr and 4 kPa, respectively, indicating fouling control by air bubbling was very effective. With 15 hour HRT, and a very long SRT(250d), 97% of TCOD and 100% SS could be removed. In average, removal efficiencies for T-N and T-P were 80% and 48%, respectively. Ammonia and coliform bacteria were completely removed. Results from cycle studies revealed that 20-60 minutes was required for complete denitrification. Nitrification occurred in two stages: fast nitrification of ammonia was followed by much slower conversion of organic nitrogen. Oxygen level at the beginning of the aeration period showed two stage jump with the height and width of the first jump depending on ammonia concentration and BOD of the influent. The anoxic/oxic cycle of 60/90 minutes appears to be an appropriate choice for the process.