Chae B.-G.,Korea Institute of Geoscience and Mineral Resources |
Kim M.-I.,Korea Infrastructure Safety and Technology Corporation
Environmental Earth Sciences | Year: 2012
An early warning system can be an effective measure to reduce the damage caused by landslides by facilitating the timely evacuation of residents from a landslide-prone area. Early detection of landslide triggering across a broad range of natural terrain types can be accomplished by monitoring rainfall and the physical property changes of soils in real time or near-real time. This study involved the installation of a real-time monitoring system to observe physical property changes in soils in a valley during rainfall events. This monitoring included the measurement of volumetric water content, which was compared with the results of laboratory flume tests to identify landslide indicators in the soils. The response of volumetric water content to rainfall events is more immediate than that of pore-water pressure, and volumetric water content retains its maximum value for some time before slope failure. Therefore, an alternative method for landslide monitoring can be based on the observation of volumetric water content and its changes over time at shallow soil depths. Although no landslide occurred, the field monitoring results showed a directly proportional relationship between the effective cumulative rainfall and the gradient of volumetric water content per unit time (t/t max). This preliminary study thus related slope failure to the volumetric water content gradient as a function of rainfall. Laboratory results showed that a high amount of rainfall and a high gradient of volumetric water content could induce slope failure. Based on these results, it is possible to suggest a threshold value of the volumetric water content gradient demarcating the conditions for slope stability and slope failure. This threshold can thus serve as the basis of an early warning system for landslides considering both rainfall and soil properties. © 2011 Springer-Verlag.
Jeong G.-C.,Andong National University |
Kim K.-S.,Korea Institute of Geoscience and Mineral Resources |
Choo C.-O.,Andong National University |
Kim J.-T.,Andong National University |
Kim M.-I.,Korea Infrastructure Safety and Technology Corporation
Natural Hazards | Year: 2011
Landslides induced by debris flow have been discussed in relation to the geotechnical properties of soil developed on bedrock, together with an emphasis on the importance of mineralogy comprising precursor soils. Three areas composed of different types of geology were compared to relate landslide with soil compositions: Precambrian gneiss (Jangheung area), Jurassic granite (Sangju area), and Tertiary sedimentary rocks composed of shale and mudstone (Pohang area) in Korea. X-ray diffraction for mineral identification and quantitative analysis, Scanning Electron Microscope for observation of microtexture, and laser size analysis for very fine particles ranging from micrometer were performed, with conventional measurements of particle size, porosity, density, permeability, and consistency for the soils. Soils at landslide sites containing a large amount of finer particles have higher uniformity and gradation coefficients, but lower consistency than those at non-landslide sites. Landslide areas are characterized by higher porosity and lower density. Soil from the gneiss area shows a high plasticity index while that of mudstone has high water content. Main clay minerals contained in soils of the sites where landslides took place are illite, chlorite, kaolinite, and montmorillonite. Mineralogical information on the constituents and microtexture of soils aids in better understanding the causes and patterns of landslide, together with mechanical properties of soils. © 2011 Springer Science+Business Media B.V.
Shin J.-H.,Konkuk University |
Kim S.-H.,Hoseo University |
Shin Y.-S.,Korea Infrastructure Safety and Technology Corporation
Soils and Foundations | Year: 2012
With regard to tunnel design, the presence of water requires that consideration be given to leakage from and pore water pressure on the lining. A segmented tunnel is generally constructed as a watertight tunnel with a certain amount of allowable leakage. It has been reported that the leakage from watertight tunnels increases with time due to lining deterioration. The deterioration of joints and/or grouts in segmented linings changes the hydraulic boundary conditions, which results in long-term hydraulic and mechanical interaction, and consequently, an increase in leakage. In this paper, the coupled mechanical and hydraulic interaction between the segment lining and the surrounding ground is investigated using the numerical modeling method. It is identified that hydraulic deterioration causes significant changes in pore water pressure and structural behavior, and accelerates leakage. It is shown that design requirements for joint contact pressure are not sufficient for controlling long-term leakage, as they do not consider hydraulic deterioration. A strain requirement, controlling leakage, and a leakage evaluation method, considering hydraulic deterioration, are proposed in this paper. © 2012. The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.
Jung H.,Korea University |
Jung H.,Incheon Bridge Corporation IBC |
Kim G.,Korea Infrastructure Safety and Technology Corporation |
Park C.,Kangwon National University
KSCE Journal of Civil Engineering | Year: 2013
As the characteristics of dynamic loadings on bridges changes its influence should be appropriately taken into account during a design process. This study utilized the measured impact factor data from 256 bridges and found about 32% exceeded the design criteria of the impact factor which was based on a span length. This study aims to suggest new design criteria for an impact factor which is based on a natural frequency rather than the span length. In order for easier estimation of the natural frequency of the bridges, equations were suggested to calculate natural frequencies with respect to different types of superstructure by using the statistical regression. The impact factors computed based on the suggest methods were compared to the field measured impact factors. The suggested calculation method herein provided very reliable results of the impact factors. It was also found that the impact factor criteria from the suggested method provided more conservative values regarding the structural performance of bridges under dynamic loadings. © 2013 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
Lee D.-S.,Inha UniversityIncheon |
Kim S.-J.,Korea Infrastructure Safety and Technology Corporation |
Cho Y.-H.,Yeungnam University |
Jo J.-H.,Inha UniversityIncheon
Energy and Buildings | Year: 2015
Exterior venetian blinds (EVBs) are widely used in commercial and residential buildings, and show a high performance level for both shading and lighting purposes. However, an EVB installed over an open window also influences natural ventilation rates. In this study, applying the pressure loss rate of an EVB to wind-driven natural ventilation rates was proposed. A mock-up building was set that the EVB was installed on the front opening. Wind generator was installed toward the front opening in order to describe wind-driven cross ventilation in a single zone. To investigate wind pressure changes through the EVB plane, 16 pressure measuring taps were installed on each of the front and back side of the EVB plane. Various wind speeds were induced toward the front opening so as to derive the pressure loss rate for the four EVB slat angle cases (0°, 45°, 90°, and no shading). The pressure loss rates for each case were derived from the field measurements. The results show that the pressure loss rates have a range of 0.22 to 0.90. In addition, the measurement results indicated that an EVB can change the air velocity by about 50% based on the slat angle. Therefore, when an EVB is installed on a window opening, the effect of the EVB on wind-driven cross ventilation rate should be taken into account. © 2015 Elsevier B.V.
Choi T.,University of Seoul |
Han J.,Korea Infrastructure Safety and Technology Corporation |
Koo J.,University of Seoul
Desalination and Water Treatment | Year: 2015
Abstract: The water pipe is an important component of the tap water facility, and plays a role as critical as that of the blood vessel in the body. However, accurate diagnosis of its condition is very difficult because it is buried under the ground, even as pipe aging frequently leads to phenomena that threaten water quality such as pipe damage and water leakage. In order to maintain and improve the performance of the existing pipe network, planned examination, operation, and maintenance, as well as technologies for proper renewal, are required. Accordingly, the present research proposes a method that can be used for the maintenance of the pipe network in each water distribution block (WDB). For this purpose, the weighted performance indicator (PI) determined by means of PI and the analytic hierarchy process technique which allows evaluation for individual water WDBs, was applied to the ELECTRE technique which is a multi-factor decision-making method. This result may be used as a reference for water leakage maintenance and for the renewal and change of a WDB. The frequency of pipe accidents is expected to be reduced by appropriate plans set up beforehand. The research was conducted by investigating the 60 WDBs of both Sujeong-Gu and Joongwon-Gu in Seongnam City. The water pipe rehabilitation ranking of the 60 WDBs could be determined as a result. In order to determine the best R model out of the 16R models, a comparison was made of the correlation coefficient, rate of ranking conformance, mean square error, and mean absolute error. The result showed that the R12 model was the most suitable model, while the priority in the maintenance of the pipe network for each block could be determined. As a result, the blocks least suitable for first maintenance were determined to be Blocks 22, 48, 38, 18, and 32, whereas the most satisfactory ones were Blocks 42, 55, 23, 12, and 41. © 2014, © 2014 Balaban Desalination Publications. All rights reserved.
Lee D.K.,Korea Infrastructure Safety and Technology Corporation |
Lee S.C.,Korea Infrastructure Safety and Technology Corporation |
You D.W.,Korea Infrastructure Safety and Technology Corporation
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2015
This case study shows the vortex-induced vibration of over-sea bridges due to wind loads and it is verified by measured data. Measurement sensors such as accelerometers, anemometers and displacement measurement sensors are installed on the bridge for structural health monitoring system. Also this paper presents the example of suppression of vibration by installing tuned mass damper. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).
Park J.-W.,Korea Infrastructure Safety and Technology Corporation |
Yoo J.-H.,Seoul National University of Science and Technology
Steel and Composite Structures | Year: 2015
This paper presents the experimental results of flexural and compression steel members strengthened with carbon fiber reinforced polymers (CFRP) sheets. In the flexural test, the five specimens were fabricated and the test parameters were the number of CFRP ply and the ratio of partial-length bonded CFRP sheets of specimen. The CFRP sheet strengthened steel beam had failure mode: CFRP sheet rupture at the mid span of steel beams. A maximum increase of 11.3% was achieved depending on the number of CFRP sheet ply and the length of CFRP sheet. In the compression test, the nine specimens were fabricated and the main parameters were: width-thickness ratio (b/t), the number of CFRP ply, and the length of the specimen. From the tests, for short columns it was observed that two sides would typically buckle outward and the other two sides would buckle inward. Also, for long columns, overall buckling was observed. A maximum increase of 57% was achieved in axial-load capacity when 3 layers of CFRP were used to wrap HSS columns of b/t = 60 transversely. Copyright © 2015 Techno-Press, Ltd.
Im E.-S.,National Institute of Meteorological Research |
Lee B.-J.,National Institute of Meteorological Research |
Kwon J.-H.,Korea Infrastructure Safety and Technology Corporation |
In S.-R.,National Institute of Meteorological Research |
Han S.-O.,National Institute of Meteorological Research
Asia-Pacific Journal of Atmospheric Sciences | Year: 2012
Because of the importance of the changes in the hydrologic cycle, accurate assessment of precipitation characteristics is essential to understand the impact of climate change due to global warming. This study investigates the changes in extreme precipitation with sub-daily and daily temporal scales. For a fine-scale climate change projection focusing on the Korean peninsula (20 km), we performed the dynamical downscaling of the global climate scenario covering the period 1971-2100 (130-year) simulated by the Max-Planck-Institute global climate model, ECHAM5, using the latest version of the International Centre for Theoretical Physics (ICTP) regional climate model, RegCM3. While annual mean precipitation exhibits a pronounced interannual and interdecadal variability, with the increasing or decreasing trend repeated during a certain period, extreme precipitation with sub-daily and daily temporal scales estimated from the generalized extreme value distribution shows consistently increasing pattern. The return period of extreme precipitation is significantly reduced despite the decreased annual mean precipitation at the end of 21 st century. The decreased relatively weak precipitation is responsible for the decreased total precipitation, so that the decreased total precipitation does not necessarily mean less heavy precipitation. Climate change projection based on the ECHAM5-RegCM3 model chain clearly shows the effect of global warming in increasing the intensity and frequency of extreme precipitation, even without significantly increased total precipitation, which implies an increased risk for flood hazards. © 2012 Korean Meteorological Society and Springer Netherlands.
An J.-W.,Korea Infrastructure Safety and Technology Corporation |
Kim Y.-S.,Korea Infrastructure Safety and Technology Corporation |
Kim H.-K.,Korea Infrastructure Safety and Technology Corporation |
Park J.-B.,Korea Infrastructure Safety and Technology Corporation
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2016
The proportion of infrastructure using for more than 30 years is expected to be increased as construction projects of infrastructure have been rapidly growing since 1970s. The maintenance of the infrastructures is essential, because aging of infrastructure can lead to its collapse and it can seriously damage the national economy and people. The existing evaluation method of tunnels in South Korea has many limitations to consider the tunnels' various performances (e.g. durability, usability etc.), because the existing method is mainly focused on the structural safety such as appearance defects or safety factors. Hence, the development of the new concept of evaluation method is needed to deal with the structure aging issues and to keep the tunnels performances continuously. The change of paradigm to performance-Based evaluation system is an effective way to invest limited finance. In this paper, the research of the performance-based evaluation technique of tunnels was conducted to improve the existing maintenance system in South Korea. © Copyright 2016 by the International Society of Offshore and Polar Engineers (ISOPE).