• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5D
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• pp.741-747
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• 2008

Nowadays, the accuracy of the geoid model has been improved through development of the combination model which was composed of traditional gravimetric geoid and geometric geoid by the GPS/leveling data in USA and Japan. It is a state of the art method in geoid modeling field that what so called hybrid geoid. In this paper, as a basic study to develop Korean hybrid geoid model, we studied gravimetric geoid solutions using three gravity reduction methods (Helmert's condensation method, RTM method and Airy-isostatic method) and evaluated the usefulness of each method in context of precise geoid. The gravimetric geoid model were determined by restoring the gravity anomalies (included TC) and the indirect effects were made from various reduction methods on the EIGEN-CG03C reference field. The results are compared with respect to the geometric geoid undulation determined from 498 GPS/leveling after LSC fitting. The results showed that hybrid geoid with RTM (Residual terrain model) reduction method was most accurate method and the value of the difference compared to geometric geoid was $0.001{\pm}0.053m$.

• Aerospace Engineering and Technology
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• v.1 no.1
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• pp.8-27
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• 2002

In this study, the load analysis of a composite canard aircraft is performed numerically. Excel visual basic program for PC is used to calculate aerodynamic coefficients, loads and moments etc.. The basic data required for the load analysis such as aircraft configuration and dimension, parts and its weight and coordinate etc. are obtained from Catia modeling, measurement or material density. Aircraft weight, center of gravity, inertia moment, structural design speeds, wing load distribution, forces and moments are evaluated by using these data. V-n diagram is also represented for selecting critical loads applied to the wing and fuselage. The V-n diagram is investigated to decide the flight envelope of canard aircraft for design speed VA, VC, VD and load factor +3.8G, -1.52G at maximum weight of 2,573 lbs and sea level. In the future, the results of the wing and fuselage load analysis is to represented by using selected critical loads.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.593-601
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• 2021

The axial fan is an element of a blower used for ventilation in various industrial fields. Many studies on aerodynamic performance have been conducted to assess axial fans using fluid dynamics. The subject was a large axial fan size, 1800 mm in diameter with 100 horsepower. The blower's axial fan consisted of blades, hubs, hub caps, and bosses are important components. The blade design has a great influence on the aerodynamic performance. 3D point data is extracted using an aerodynamic performance prediction program, and a 3D modeling shape is generated. The blades and hubs, which are important components, can be easily modified if processed by cutting owing to the environment in which blades and hubs are manufactured through die casting or gravity casting. In this study, the structural safety of components and the analysis results of weak areas at the rated operating speed of the axial fan were verified using the maximum stress and safety factor. The tip clearance reflected in the design was the rotation of the blade. To check whether there is interference with other components, the displacement result was derived to verify the structural safety of the axial fan.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.381-388
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• 2010

In this study, characteristics of the seismic response of the non-earthquake resistant reinforced concrete (RC) frame were identified. The test building is designed to withstand only gravity loads and not in compliance with modern seismic codes. Smooth bars were utilized for the reinforcement. Members are provided with minimal amount of stirrups to withstand low levels of shear forces and the core concrete is virtually not confined. Columns are slender and more flexible than beams, and beam-column connections were built without stirrups. Through the modeling of an example RC frame, the feasibility of the fiber elementbased 3D nonlinear analysis method was investigated. Since the torsion is governed by the fundamental mode shape of the structure under dynamic loading, pushover analysis cannot predict torsional response accurately. Hence, dynamic response history analysis is a more appropriate analysis method to estimate the response of an asymmetric building. The latter method was shown to be accurate in representing global responses by the comparison of the analytical and experimental results. Analytical models without rigid links provided a good estimation of reduced stiffness and strength of the test structure due to bond-slip, by forming plastic hinges closer to the column ends. However, the absence of a proper model to represent the bond-slip poased the limitations on the current inelastic analysis schemes for the seismic analysis of buildings especially for those with round steel reinforcements. Thus, development of the appropriate bond-slip model is in need to achieve more accurate analysis.

• Ocean Systems Engineering
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• v.1 no.4
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• pp.285-296
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• 2011

Spar platforms have several advantages for deploying wind turbines in offshore for depth beyond 120 m. The merit of spar platform is large range of topside payloads, favourable motions compared to other floating structures and minimum hull/deck interface. The main objective of this paper is to present the response analysis of the slack moored spar platform supporting 5MW wind turbine with bottom keel plates in regular and random waves, studied experimentally and numerically. A 1:100 scale model of the spar with sparD, sparCD and sparSD configuration was studied in the wave basin ($30{\times}30{\times}3m$) in Ocean engineering department in IIT Madras. In present study the effect of wind loading, blade dynamics and control, and tower elasticity are not considered. This paper presents the details of the studies carried out on a 16 m diameter and 100 m long spar buoy supporting a 90 m tall 5 MW wind turbine with 3600 kN weight of Nacelle and Rotor and 3500 kN weight of tower. The weight of the ballast and the draft of the spar are adjusted in such a way to keep the centre of gravity below the centre of buoyancy. The mooring lines are divided into four groups, each of which has four lines. The studies were carried out in regular and random waves. The operational significant wave height of 2.5 m and 10 s wave period and survival significant wave height of 6 m and 18 s wave period in 300 m water depth are considered. The wind speed corresponding to the operational wave height is about 22 knots and this wind speed is considered to be operating wind speed for turbines. The heave and surge accelerations at the top of spar platform were measured and are used for calculating the response. The geometric modeling of spar was carried out using Multisurf and this was directly exported to WAMIT for subsequent hydrodynamic and mooring system analysis. The numerical results were compared with experimental results and the comparison was found to be good. Parametric study was carried out to find out the effect of shape, size and spacing of keel plate and from the results obtained from present work ,it is recommended to use circular keel plate instead of square plate.