In this study, Ni-Y2O3 powder was prepared by alloying recomposition oxidation sintering (AROS), solution combustion synthesis (SCS), and conventional mechanical alloying (MA). The microstructure and mechanical properties of the alloys were investigated by spark plasma sintering (SPS). Among the Ni-Y2O3 powders synthesized by the three methods, the AROS powder had approximately 5 nm of Y2O3 crystals uniformly distributed within the Ni particles, whereas the SCS powder contained a mixture of Ni and Y2O3 nanoparticles, and the MA powder formed small Y2O3 crystals on the surface of large Ni particles by milling the mixture of Ni and Y2O3. The average grain size of Y2O3 in the sintered alloys was approximately 15 nm, with the AROS sinter having the smallest, followed by the SCS sinter at 18 nm, and the MA sinter at 22 nm. The yield strength (YS) of the SCS- and MA-sintered alloys were 1511 and 1688 MPa, respectively, which are lower than the YS value of 1697 MPa for the AROS-sintered alloys. The AROS alloy exhibited improved strength compared to the alloys fabricated by SCS and conventional MA methods, primarily because of the increased strengthening from the finer Y2O3 particles and Ni grains.

손상된 콘크리트 구조물은 적절한 보수 및 보강을 통해 성능과 기능을 회복시켜야 한다. 장기간 공기 중에 노출된 콘크리트는 동결융화 작용으로 균열 및 박리를 일으켜 내부 철근의 부식을 유발하게 되는 주요 요인이 된다. 본 연구에서는 동 결융해 손상을 입은 콘크리트 교각의 FRP 보강의 연성에너지 증가 효과를 분석하였다. 보강 FRP 재료와 보강 높이, 보강 겹수 에 따라 동결융해 손상 콘크리트의 푸쉬오버 매개변수 해석을 수행하여 모멘트 곡률의 연성에너지를 비교 분석하였다. FRP 보 강 높이는 소성 힌지 이상의 높이 보강은 비효율적이며, 동결융해 손상이 커질수록 FRP 보강으로 인한 연성에너지 증가량은 커 지는 것을 확인하였다. 보강으로 인한 연성에너지 증가를 위해서는 고강도 FRP 재료보다는 높은 탄성계수를 갖는 FRP 재료가 효율적으로 나타났다. 또한 각 FRP 재료의 특성에 따라 일정 보강 겹수 이상에서 보강 효과가 나타나는 것을 확인하여 FRP 보 강으로 인한 손상된 콘크리트 교각의 연성에너지를 비교 분석하였다.

Long-span marine bridges are generally designed as long-span bridges in order to secure the running route of the ship and reduce the cost and time of the bridge pier construction. In long-span bridges, the range of load resistance transmitted by the superstructure and cable is determined by the mast and foundation. In the other words, the range of designable span length would be determined by the mast and foundation condition. The floating bridge is a type in which the superstructure is supported by the force of buoyancy without the pier mounted on the seabed so that the buoyancy of the floating bridge is balanced by the dead load and buoyancy of the structure. As a technique to overcome the weakness of existing long span bridges, it is possible to consider the type of cable supported bridges with floating tower. In this study, according to the tendon arrangement and initial tension distribution, the static global performance of the long-span bridges with floating tower were evaluated.

All structures can not be perfect due to geometric or material initial imperfections. Initial imperfections are an important factor in determining the buckling mode and are known to be important factors in evaluating the actual buckling strength. The DNV-RP-C202 design standard limits the longitudinal stiffener spacing. However, the criteria for the stiffener spacing presented in DNV-RP-C202 is a guideline derived from the curved panel theory of perfect cross-sectional shape without initial imperfections. In this study, considering geometric initial imperfections, the transition point of stiffener spacing where longitudinal stiffeners affect the buckling strength of reinforced steel wind turbine tower is analyzed using finite element analysis program. The results of finite element analysis compared with theoretical results based on the perfect shape. As a result, a more reasonable stiffener spacing considering the initial imperfections was suggested.

Recently, wind power has received attention as one of remarkable renewable energy resources, and worldwide researches about wind power are actively being proceeded. Wind turbine tower has a major role for safety in the wind turbine systems. It is necessary for design tower structure to consider various environmental conditions. Earthquake, as one of the such environmental loads, is ground motion that applied to bottom of the tower structure and has a possibility of critical effect to the wind tower structure. There are various ways for seismic analysis, but design specifications that are in use do not suggest detailed method for seismic analysis. In this study, seismic responses are analyzed through different ways and the adequacy of seismic design methods is examined.

Natural frequency characteristic of Wind turbine tower is important for designing of tower due to guarantee of structural safety of tower. In GL specification, natural frequency of tower should be designed by consideration of blade rotational frequency. Natural frequency characteristic of tower could be changed by mass ratio of RNA-tower, modeling method of blade and angle of blade in idling condition. In this research, natural frequency of tower is analysed by ABAQUS and compared it result according to tower dimension.

The thin cylindrical shell structure under compression should be checked with buckling stability. In DNV, there is a spacing criteria of stiffener which based on linear theory without initial imperfection. In this study, structural analysis, using geometry nonlinear analysis, of stiffened cylindrical buckling strength with various initial imperfection were performed and compared with DNV and FEM results.

교량의 장경간화에 따라 큰 모멘트가 작용하는 부모멘트 구간에 트러스를 배치하고 상대적으로 적은 모멘트가 발생하는 정모멘트 구간에는 강박스 구조를 활용한 강박스-트러스 하이브리드 교량의 곡선교 적용성 및 활용 가능성을 평가하여 보았다.본 연구에서는 다양한 곡률을 가지는 강박스-트러스 하이브리드 교량의 트러스 구간의 트러스 형식 변화에 따른 전체적 교량의 구조적 거동을 분석하였다. 이를 통해 직선교량과 곡선교량의 거동 차이성 및 곡선교 적용 시 보다 안전한 트러스 형식을 평가하는데 큰 도움이 될 것이다.

Steel Box-Truss Hybrid bridge consisted with steel box type in positive moment that is allowed to resist with low depth and truss type in negative moment is new type bridge. This can be used as 80m∼150m long span bridge and is economical structural type. But safety of truss type is concerned because of torsion that occurs when Steel Box-Truss Hybrid bridge applies a curved bridge. Therefore, it is necessary to analyze and evaluate straight and curved bridge for commercialization of Steel Box-Truss Hybrid bridge. In this study, structural analysis of Steel Box-Truss hybrid curved bridge with various curvature is performed and compared with member force and displacement of Steel Box-Truss Hybrid straight bridge. Also the applicable limited curvature of Steel Box-Truss Bridge form is proposed.

Wind Turbine Tower takes about 26.3% of overall wind turbine cost. So tower shell design is very important part. When designing tower eigenfrequency, strength analysis, fatigue strength analysis, buckling analysis and flange connection analysis have to considered. This paper contains procedure of tower analysis and compare ABAQUS result with design specification

For the optimized design of the wind turbine tower, demonstrate the superiority of ability to resist the lateral load on the ICH-CFT, i.e. ability to resist the moment, compared to Steel Tubular Type that is mainly used in the existing, by using P-M Diagram

This study estimated extreme wind speed by means of national wind map, provided by Korea Institute of Energy Research, to sustain the wind towers’ structural stability that is required for the production of mass wind power. The number of research object regions is three in the East, West and South seas. Meteorological resource data were calculated by dividing the data into the various reference periods. In addition, Gumbel distribution method and Extreme Wind Speed Model (EWM) indicated in IEC 61400-3 were adopted to measure the extreme wind speed. In conclusion, it is discovered that the more suitable Gumbel distribution method is to secure the stability of wind towers.

Measuring displacement data is very useful as it can be applied to static, quasi-static, and dynamic behavior of structures. GNSS system is used to measuring displacement of structures. In this study, test bridge model was made to evaluate GNSS singnal characteristic.

Steel Box-Truss Hybrid bridge consisted with steel box type in positive moment that is allowed to resist with low depth and truss type in negative moment not only has restriction of delivery but has to use high depth is new type bridge. In this study, structural analysis of Steel Box-Truss hybrid curved bridge with various curvature is performed and compared with member force and displacement of Steel Box-Truss Hybrid straight bridge. Also the applicable limited curvature of Steel Box-Truss Bridge form is proposed.

In this study, structural analysis was performed for the trapezoidal steel box girders. The girder is assumed to be made not by welded but by folded. Because the girder has no welded connection, the material can show its full strength without residual stresses. In the nonlinear analysis, however, there should be difference between sharp-corner girder and rounded-corner girder. Therefore, the parametric study was performed due to the radius of fillet to estimate the shear buckling strength of the girders.