Suigen, South Korea
Suigen, South Korea

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Kim S.-J.,Civil Engineering Research Team | Cha K.-S.,Civil Engineering Research Team | Kim T.-H.,Civil Engineering Research Team
Geotechnical Special Publication | Year: 2012

Power plants, including tidal and nuclear power plants and bridges, as well as shipbuilding yards, are frequently constructed in offshore areas. Such structures inevitably require cofferdams in order to cut off water flowing from the seaside. Recently, the cut-off of seawater using grouting has increased. The grouting work is carried out in the sea and at deep depth, and sometimes exposed to a severe sea level variation. For sodium silicate-cement grout, alkali which is dissolved in sodium silicate fluid, leaches when it meets the water. It thus has weak durability, and therefore is inadequate for long term water cut-off. In this study, a geo-polymer type of grout is developed in order to improve durability and stability. AluminoSilicate Oxide (Si2O5Al2O2) that is contained in fly ash or meta-kaolin is combined with SiOAl reacting to water glass, which is different from CSH gel. In order to figure out the effect of geo-polymer type of grout on compressive strength of sodium silicate- cement gel, X-ray diffraction analysis and short/long term uniaxial compression tests are conducted. The results show that the strength is improved by 1.5 times up to 20 times. © 2012 American Society of Civil Engineers.

Park S.-W.,Dankook University | Chae D.,Dankook University | Kim K.-O.,Civil Engineering Research Team | Kwon O.,Korea Ocean Research and Development Institute | Cho W.,Dankook University
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2011

In Korea, due to the restriction of current use of land and the rather complicated shore line, the reclamation has been applied to many places near the west shore of Korea to maximize the use of current land such as Song-Do and Saemankeum sites. Accordingly, large quantity of soils is required for the reclamation of those sites and various research on the artificial soil mixture have been performed as well. Coal combustion by-products (CCBPs) are fly ash and bottom ash which are generated in large quantities in the coal-fired steam plants. More than hundreds tons are disposed in the designated ash pools even though some of them are reused as construction materials. To extend the use of CCBPs, this paper investigated the applicability to the reclamation site with dredged soils. The artificial soil mixture is resedimented with 300 mm consolidometer in the composition of 30% of CCBPs and 70% of fine-grained soils. Based on the consolidation characteristics of fine-grained soils, the compressibility and consolidation characteristics of artificial soil mixture is investigated through the conventional consolidation tests. As a result, the artificial soil mixture is very suitable for the large reclamation sites. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).

Shin H.Y.,Civil Engineering Research Team | Kim K.O.,Civil Engineering Research Team | Kim Y.S.,Civil Engineering Research Team | Kim T.H.,Korea University
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2011

In Korea, reclaiming works have been performed in many coastal areas during last two decade. Most of these reclaiming works were performed with dredged material due to its economical benefits. However, frequent dredging and its reuse cause the exhaustion of near shore dredged material. Because of these reason, nowadays, long distance pumping and transfer of dredged material have to be considered. Long distance transfer is another branch of study, and this seems to be more expensive. For this reason, new interests concerning the development of alternative filling material arose. Studies for using many kind of recycled material such as wasted tire, wasted shell, wasted concrete, etc., as an alternative filling material had been performed. However most of these materials have to be experienced another manufacturing process, and also some of these materials have a small applicability because of its environmental hazard. In this paper, application of buried coal ashes as a land reclamation material was studied. Developing new material needs many geotechnical and environmental examination, such as settling and self-weigh-consolidation characteristics, shear strength characteristics and environmental problems, etc. As a first attempt, DAEWOO E&C in Korea started to study the applicability of buried coal ash mixture as an alternative filling material. As a result of the series of self-weigh-consolidation tests, this paper briefly presents the basic geotechnical characteristics of these mixtures according to their mixture ratio, and also presents their improved effect comparing to dredging material without coal ash. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).

Kim I.-G.,Civil Engineering Research Team | Chung C.-H.,Dankook University | Shim C.-S.,Chung - Ang University | Kim Y.-J.,Civil Engineering Research Team
International Journal of Steel Structures | Year: 2014

The use of concrete filled circular hollow steel section (CFCHS) members in bridge design is a relatively new concept. In the design of recently constructed steel-concrete composite bridges using CFCHS truss girders for the main load carrying structure, the fatigue verification of the tubular spatial truss joints is a main issue. This paper presents a comprehensive study on stress concentration in welded tubular steel N-joints. Finite element analyses are performed in order to derive stress concentration factors (SCFs) from hot-spot stresses for typical three load conditions. The SCF values are presented in the form of equations in terms of the non-dimensional joint parameters. The proposed SCF equation for CFCHS N-joints shows good agreement with the test results on a tubular girder model. The presence of infilled grout in the chord is found to reduce the SCF. © 2014 Korean Society of Steel Construction and Springer-Verlag Berlin Heidelberg.

Shin H.Y.,Civil Engineering Research Team | Kim K.O.,Civil Engineering Research Team | Kim Y.S.,Civil Engineering Research Team | Kim T.H.,Korea University
14th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering | Year: 2011

In constructing a new ground near the coastal region, landfill of dredged soil such as marine clay and silty clay has been generally used as a ground material. Unfortunately, as a dredging sequence causes serious problems related to the floating material and influent sewage which is occurred in pumping seabed ground, minimum use of dredged material is recommended. Also, development of new ground in the coastal region, dredged marine clay and/or silt clay experiences a successive process so called settling and self-weight consolidation. In design and construction of coastal landfill ground, the rate of settling and self-weight consolidation is very important factors which influence on the construction period and coat. In addition, nowadays there are serious shortages of quality soils which are used as a filling material. In order to overcome these problems, many researchers had been studying to develop new alternative materials and to reuse construction wastes. This study performed series of small size column test according to the adding ration of coal ash to the clay, to estimate approximate applicability of coal ash aggregates an addictives which accelerate a settling and self-weight consolidation of clay slurry. Test results show that the amount of coal ash addictives increases, rate of settling and self-weight consolidation could be accelerated.

Shim C.,Chung - Ang University | Kim D.,Chung - Ang University | Jung D.,Chung - Ang University | Kim I.,Civil Engineering Research Team | Chung C.,Dankook University
NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering | Year: 2014

Digital manufacturing and fast construction using machinery need standard design models and connection methods of prefabricated modules. Modular bridge substructures with concrete-filled steel tube (CFT) columns and composite pier caps were suggested to realize accelerated bridge construction. Column modules have bracings to connect each other and use standard tube products. Each bridge pier has four or six CFT columns which connect to the pier cap. From the cyclic test of a modular bridge pier, connection failure due to low cycle fatigue was observed. In order to solve the problem, four types of the connection for the enhancement of energy dissipation were fabricated and tested to derive moment-rotation curves. Using the curves, seismic behavior of CFT bridge piers with the connections was investigated. Intentional plastic hinge connection provided ductile behavior without premature failure of the connection. A prototype modular bridge pier was constructed and cyclic tests were performed. Incremental cyclic tests showed that the connections between column modules provided plastic hinge at the bottom part of CFT columns after yielding of bracing connection parts without connection failure. Through the cyclic test, design concepts of column modules, connection of bracings and pier cap module were verified.

Shim C.-S.,Chung - Ang University | Chung C.-H.,Dankook University | Kim I.-K.,Civil Engineering Research Team | Kim Y.-J.,Civil Engineering Research Team
Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE) | Year: 2010

This paper deals with prefabricated composite bridges with full-depth precast decks. For steel-concrete composite bridges, a new shear connection and its design provisions were suggested by extensive experiments and finite element (FE) analyses. The shear connection for precast decks was investigated to consider the effects of bedding layer, filling material in shear pockets and group arrangement. For the integrity of the precast decks, longitudinal prestressing was introduced and design guidelines for the magnitude of prestress were proposed. It is necessary to keep the joints compressive during the service life of the bridge to prevent cracking and leakage at the joints. Bonding strength was neglected in the design. In order to take full advantage of precast slabs, the concept of incremental prestressing was adopted for continuous prestressed concrete (PSC) girders. Based on the experimental research on joints and connections, several model tests were performed to verify the suggested design guidelines. There are several applications using precast decks not only for steel bridges and but also for concrete ones. Among them, design characteristics and enhanced details for construction were introduced for two bridges.

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