• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.674-679
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• 1998

In designing the prestressed concrete box-bridge, the dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which, therefore, must be considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP, JSCE and KSCE design code and EMM, AEMM, RCM, IDM and SSM has been suggested for analytical method in consideration of the time-dependent characteristics. In this study, the creep test was carried out for four curing ages of concrete which were applied to the prestressed concrete structure at a construction site, and the results of test were compared to the values of creep prediction by the design code. Also the creep test of step-wise incremental stresses were performed and were compared to analytical methods.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1139-1144
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• 2000

Recent advance in material technology has accelerated the development of high strength concrete using lightweight artificial aggregates. The lightweight concrete has many advantages that the reduction of dead lads and the increase in load capacity can ofter. In this study, lightweight polymer concrete using unsaturated polyester resin and lightweight aggregate were prepared and tested for testing the physical and the mechanical properties. The compressive strengths of lightweight polymer concretes with specific gravities from 1.32 to 1.78 were compressive strength of 250 to 470 $kgf/cm^2$ and flexural strengths were measured to be in the range of a third to a quarter of compressive strength

• Interaction and multiscale mechanics
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• v.1 no.3
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• pp.381-396
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• 2008

The aerostatic instability of cable-supported bridges is studied, with emphasis placed on modeling of the geometric nonlinear effects of various components of cable-supported bridges. Two-node catenary cable elements, which are more rational than truss elements, are adopted for simulating cables with large or small sags. Aerostatic loads are expressed in terms of the mean drag, lift and pitching moment coefficients. The geometric nonlinear analysis is performed with the dead loads and wind loads applied in two stages. The critical wind velocity for aerostatic instability is obtained as the condition when the pitching angle of the bridge deck becomes unbounded. Unlike those existing in the literature, each intermediate step of the incremental-iterative procedure is clearly given and interpreted. As such, the solutions obtained for the bridges are believed to be more rational than existing ones. Comparisons and discussions are given for the examples studied.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.247-255
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• 1999

Because of relatively heavy dead weight of concrete itself and unavoidable heat of massive concrete in bridge piers circular hollow columns are widely used in Korean highway bridges Since the occurrence of 1995 Kobe earthquake there have been much concern about seismic design for various infrastructures inclusive of bridge structures. It is however understood that there are not much research works for nonlinear behavior circular hollow columns subjected to earthquake motions. The ultimate of this experimental research is to investigate nonlinear behavior of hollow reinforced concrete bridge piers under the quasi-static cyclic load test and than to enhance their ductility by strengthening the plastic hinge region with glassfiber sheets. It can be concluded from Quasi-static test for 7 bridge piers that approximate 4-5 ductility factor can be experimentally obtained for bridge piers nonseismically designed in conventional way which approximate 5-6 ductility factor for those seismically designed.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.89-98
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• 2014

Employing tilted forms in tall buildings is a relatively new architectural phenomenon, as are the cases with the Gate of Europe Towers in Madrid and the Veer Towers in Las Vegas. This paper studies structural system design options for tilted tall buildings and their performances. Tilted tall buildings are designed with various structural systems, such as braced tubes, diagrids and outrigger systems, and their structural performances are studied. Structural design of today's tall buildings built with higher strength materials is generally governed by lateral stiffness. Tilted towers are deformed laterally not only by lateral loads but also by dead and live loads due to their eccentricity. The impact of tilting tall buildings on the gravity and lateral load resisting systems is studied. Comparative evaluation of structural systems for tilted tall buildings is presented.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.23-34
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• 1999

In designing PSC box girder bridge, the dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which, therefore, must considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP, JSCE and KSCE design code. In this study the creep and shrinkage test were carried out for four curing ages of concrete which was applied to the pretressed concrete box-girder bridge at a construction site, and the results of test were compared to the values of prediction by the design code. Shrinkage test shows that the test results are similar to KSCE-96 and JSCE-96 but very higher than other prediction model and creep test results are generally similar to ACI-209 and DSCE-96 but lower than other prediction models in contrast to shrinkage test.

• KCI Concrete Journal
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• v.11 no.3
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• pp.99-107
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• 1999

In designing the Prestressed concrete box-girder bridge. dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which. therefore, must be considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP, JSCE and KSCE design code and EMM, AEMM, RCM, IDM and SSM has been suggested for analytical method in consideration of time-dependent characteristics. In this study the creep test was carried out for four different curing ages of concrete which were applied to the Prestressed concrete structure at the construction site, and the results of test were compared with the values of creep prediction proposed by the design code. Also the creep test was performed with step-wise incremental stresses and the results were compared to the analytical values.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.305-308
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• 2006

In this paper, the seismic performance of SRC piers for near fault motions was evaluated by shaking table tests on small scale models. Dead load of the superstructures was simulated by axial prestress at the center of the column section. A mass frame linked with steel bars was fabricated to include the effect of superstructure mass. Friction of the mass frame when it moves was minimized by special details and it was proved before tests. Five pier models with 400mm diameter were tested by increasing the acceleration of the near fault motion. Test results were discussed and compared with previous quasi-static tests.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.29-31
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• 2013

In this study, the characteristics of particulate matters (PM) from diesel and biodiesel fuel combustion was experimentally investigated. The experiment was performed in a single cylinder common-rail compression ignition engine. The fuels were injected at -5 CAD (Crank angle degree) ATDC (After top dead center) with 80 MPa injection pressure. Size distribution of PM was measured by scanning mobility particle sizer (SMPS) and morphology of PM was studied by transmission electron microscopy (TEM). PM from biodiesel shows lower emission level and smaller primary particles.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.395-396
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• 2014

3상 독립형 인버터의 비대칭 출력 전압은 부하의 불평형에 의하여 야기되며 암 단락을 방지하기 위한 데드타임은 출력 전압에 비선형적인 특성을 발생시킨다. 인버터가 불평형부하 구동 시 3상 출력전압은 불평형의 홀수배 고조파를, 동기좌표계 상에서 dq전압은 서로 크기가 다른 짝수배 고조파를 발생시킨다. 본 논문에서는 불평형부하에 따른 불평형 출력 전압을 평형으로 유지하는 동시에 공진제어를 이용하여 데드타임에 의한 불평형 고조파를 보상하는 전압제어기를 제안하였으며 10kW 용량의 독립형 인버터를 제작하여 제안한 제어기법의 타당성을 입증하였다. 실험을 통해 출력 전압의 THD는 4.3%에서 1.5%로, 불평형율은 4.3%에서 1.1%로 감소함을 확인하였다.