• Structural Engineering and Mechanics
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• v.74 no.6
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• pp.789-807
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• 2020

Multiple earthquakes that occur during short seismic intervals affect the inelastic behavior of the structures. Sequential ground motions against the single earthquake event cause the building structure to face loss in stiffness and its strength. Although, numerous research studies had been conducted in this research area but still significant limitations exist such as: 1) use of traditional design procedure which usually considers single seismic excitation; 2) selecting a seismic excitation data based on earthquake events occurred at another place and time. Therefore, it is important to study the effects of successive ground motions on the framed structures. The objective of this study is to overcome the aforementioned limitations through testing a two storey RC building structural model scaled down to 1/10 ratio through a similitude relation. The scaled model is examined using a shaking table. Thereafter, the experimental model results are validated with simulated results using ETABS software. The test framed specimen is subjected to sequential five artificial and four real-time earthquake motions. Dynamic response history analysis has been conducted to investigate the i) observed response and crack pattern; ii) maximum displacement; iii) residual displacement; iv) Interstorey drift ratio and damage limitation. The results of the study conclude that the low-rise building model has ability to resist successive artificial ground motion from its strength. Sequential artificial ground motions cause the framed structure to displace each storey twice in correlation with vary first artificial seismic vibration. The displacement parameters showed that real-time successive ground motions have a limited impact on the low-rise reinforced concrete model. The finding shows that traditional seismic design EC8 requires to reconsider the traditional design procedure.

• Journal of Korea Multimedia Society
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• v.17 no.3
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• pp.287-293
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• 2014

Early fire detection is very important to avoid loss of lives and material damage. The conventional smoke detector sensors have difficulties in detecting smoke in large outdoor areas. The video-based smoke detection can overcome these drawbacks. This paper proposes a new smoke detection method in video sequences. It uses the ratio of variation rate of subband energy in the wavelet transform domain. In order to reduce the false alarm, candidate smoke blocks are detected by using motion, decrease of chromaticity and the average intensity of block in the YUV color space. Finally, it decides whether the candidate smoke blocks are smokes or not by using their temporal changes of subband energies in the wavelet transform domain. Experimental results show that the proposed method noticeably increases the accuracy of smoke detection and reduces false alarm compared with the conventional smoke detection methods using wavelets.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.3
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• pp.188-198
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• 2005

This study was conducted to survey the catches of vertical bottom longline fisheries in the sea mount of central northern Pacific($30^{\circ}-42^{\circ}N$, $170^{\circ}-175^{\circ}E$), during the period of July 1 to August 25,2004 by commercial fishing vessel. The number of 57 test fishing was carried out in the central northern Pacific during 43 days and the total catches were 21,092.4kg as 19 fish species, CPUE/day and catches/day were 185 baskets and 490.5kg, respectively. Main fish species caught from the experimental fishing were Squalus mitsukurii (66.3%), Coelorhyrchus asperocephaius (11.7%) and Helicolenus avius (9.8%) and, average inside diameter for fish mouth was 4.0cm over. Catch ratio according to each fishing ground was the order of F, D, J, B and C. Catch ratio fur water depth was the order of 450-500m, 350-400m, 300-350m, 400-450m, 1000-1100m and 500-550m and, main species by water depth was Squalus mitsukurii for 300-400m, Etmopterus lucifer for 300-550m, Coelorhyrchus asperocephaius far 1,000m over. Catch ratio according to the kind of hooks was higher at the hook no.6 for Squalus mitsukurii and no. 5 for Etmopterus lucifer and, catch ratio by baits was higher at squid for Squalus mitsukurii, saury and eel for Helicolemus avius and saury for Etmopterus lucifer. Accordingly, it is thought that the extension of fishing hours is needed with the reduction of damage and loss for fishing gears during fishing operation.

• Journal of the Korean Geotechnical Society
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• v.38 no.6
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• pp.5-16
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• 2022

In the case of domestic seismic design, deformation of structures and ground is reviewed through undrained condition analysis and applied to design and maintenance. However, when the ground undergoes dissipation after liquefaction due to a dynamic load such as an earthquake, additional displacement occurs and greater damage occurs. Therefore, it is necessary to additionally analyze the drained conditions, It is necessary to grasp the exact ground behavior such as calculating and reviewing the amount of subsidence of the ground that has undergone the loss process after an earthquake and apply it to design and maintenance together. Therefore, in this study, numerical analysis was performed assuming undrained and drained conditions by dividing pure sandy soil into loose soil with Dr=30% and high-density soil with Dr=70%. In particular, when a dynamic load such as an earthquake is applied, considering the drained conditions of the ground, the settlement amount and the pore water pressure ratio of loose and dense ground are compared, This study focused on comparative analysis of settlement amount and pore water pressure ratio in the process of ground loss after an earthquake. As a result, the amount of subsidence during the dissipation process was 30 to 60 times greater than that of the earthquake.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.349-357
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• 2016

Recently, the quantity of risk in construction project has been inflated due to the fact that current construction projects have been large and complicated. Therefore, a study on the risk management methods is necessary that can predict and respond to the need in complicated modern construction projects. In this study, the objective is to analyze the cause of accident in actual construction sites and develop a risk assessment model based on insurance claims records. To reach the goal of this study, first, the frequency and severity of accidents are analyzed the causes of accidents based on the classification; progress rate, season, and total construction costs. Second, a risk assessment model is developed by utilizing a multiple regression analysis. The dependent variable is loss ratio of material damage and three categories; natural hazards, geographic information, and construction method & ability, are used as the independent variables. The model's adjusted R-square is 0.455. The contributions of this study will be used as a material for a quantitative risk analysis model development and review of the construction risk factors for future study.

• Journal of Korea Water Resources Association
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• v.46 no.1
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• pp.47-58
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• 2013

Recently, an increase in the occurrence of sudden local flooding of great volume and short duration due to global climate changes has occasioned the significant danger and loss of life and property in Korea as well as most parts of the world. Such a local flood that usually occurs as the result of intense rainfall over small regions rises quite quickly with little or no advance warning time to prevent flood damage. To prevent the local flood damage, it is important to quickly predict the flood severity for flood events exceeding a threshold discharge that may cause the flood damage for inland areas. The aim of this study is to develop the NFI (New Flood Index) measuring the severity of floods in small ungauged catchments for use in local flood predictions by the regression analysis between the NFI and rainfall patterns. Flood runoff hydrographs are generated from a rainfall-runoff model using the annual maximum rainfall series of long-term observations for the two study catchments. The flood events above a threshold assumed as the 2-year return period discharge are targeted to estimate the NFI obtained by the geometric mean of the three relative severity factors, such as the flood magnitude ratio, the rising curve gradient, and the flooding duration time. The regression results show that the 3-hour maximum rainfall depths have the highest relationships with the NFI. It is expected that the best-fit regression equation between the NFI and rainfall characteristics can provide the basic database of the preliminary information for predicting the local flood severity in small ungauged catchments.

• Journal of Korean Society of Archives and Records Management
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• v.16 no.3
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• pp.179-207
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• 2016

This study suggested the necessity of the management of R & D management records produced from government-supported science research institutes (the so-called "gwagichulyeon") and of a record management manual (item). As such, it gathered rules with regard to record management, conducted a survey, and interviewed general R & D managers. As a result of the research, the ratio of the arrangement of R & D managers to R & D management departments is 100%; however, the ratio of the arrangement of record managers is 33.3%-50%, and the ratio of the arrangement of record management departments is 23.1%, which was poor. The enactment ratio of record management rules is 26.4%, and 73.7% of institutes has managed their records under the provision only of document management rules or only of office management rules. R & D management records has been collected according to an institute's capability without a prescribed collection scope, and the conditions with regard to the omission, damage, and loss of records were poor. There are institutes that did not comprehend the production status of R & D management records. Thus, as a response, this study suggested a record management manual (item) established for the arrangement duties of record managers and record management departments as well as for notifications on the status of R & D management records. In addition, this study produced a standardized collection scope and described how to manage R & D management records.

• The Journal of the Petrological Society of Korea
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• v.25 no.4
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• pp.361-372
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• 2016

Lahar, one of catastrophic events, has the potential to cause the loss of life and damage to infrastructure over inhabited areas. This study using Laharz_py program, was performed schematic prediction on the impact area of lahar hazards at the Mt. Halla volcano, Jeju island. In order to comprehensively address the impact of lahar for the Mt. Halla, two distinct parameters, H/L ratio and lahar volume, were selected to influence variable for Laharz_py simulation. It was carried out on the basis of numerical simulation by estimating a possible lahar volumes of 30,000, 50,000, 70,000, 100,000, 300,000, $500,000m^3$ according to H/L ratios (0.20, 0.22 and 0.25) was applied. Based on the numerical simulations, the area of the proximal hazard zone boundary is gradually decreased with increasing H/L ratio. The number of streams which affected by lahar tended to decrease with increasing H/L ratio. In the case of H/L ratio 0.20, three streams (Gwangryeong stream, Dogeun stream, Han stream) in the Jeju-si area and six streams (Gungsan stream, Hogeun stream, Seohong stream, Donghong stream, Bomok stream, Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. In the case of H/L ratio 0.22, two streams (Gwangryeong stream and Han stream) in the Jeju-si area and five streams (Gungsan stream, Seohong stream, Donghong stream, Bomok stream, Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. And in the case of H/L ratio 0.25, two streams (Gwangryeong stream and Han stream) in the Jeju-si area and one stream (Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. The results of this study will be used as basic data to create a risk map for the direct damage that can be caused due to volcanic hazards arising from Mt. Halla.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.4
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• pp.523-530
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• 2019

Pavement distress and traffic accidents are caused by pot-hole. In addition, direct and indirect damages of road users are increasing, such as loss of life due to personal injury and damage to vehicles. Generally, the asphalt concrete pavements are continuously aging from the production process to the terminal performance period. Aging causes stripping due to cracks and moisture penetration and weakening the pavement structure to induce pot-hole. In this study, adhesion performance and moisture sensitivity were evaluated according to aging degree in order to investigate the effect of aging on asphalt pavement. As a result of the study, the viscosity of the asphalt binder was increased with aging and the bond strength of the aged was increased 2~3 times than that of the unaged. The results of accelerated aging test showed an increases in indirect tensile strength and the increase in the TSR (Tensile Strength Ratio) by 4.2~8.9 %. As a result, it is noted that the anti-stripping and adhesion performances of the aged asphalt concrete are improved compared to the unaged one under the aging conditions of asphalt binder coated on aggregates.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.131-139
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• 2012

The lateral reinforcements of concrete such as hoops and spiral bars are known to confine concrete to compensate the strength loss due to fire by reducing explosive spalling and improving the capacity of ductility. In this context, a study was conducted to investigate the residual mechanical properties of confined and unconfined concrete($f_{ck}$=60MPa) after a single thermal cycle at 300, 600, $800^{\circ}C$. The main parameters required to establish the stress-strain relationship are the peak stress, the elastic modulus, and the strain at peak stress. The knowledge of the residual mechanical properties of concrete is necessary whenever the thermally damaged structure is required to bear a significant share of the loads, even after a severe thermal accident. Based on the results obtained in this study, the residual stress of confined concrete under thermal damage is higher according to the level of confinement and the larger strain made it to have better ductility. The decreasing ratio of elastic modulus from the relationship of stress and strain was also smaller than that of unconfined concrete.