• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.563-574
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• 2006

The objective of this study is to determine the effect of the loading size on displacements of stiffened plates with open ribs using the orthotropic rigidity ratio as the parameter. To analyze the displacement behavior of stiffened plates according to the loading size, a concentrated load and three types of uniform distributed loads were applied on the rib at the center of some plates. The results of the analysis of various stiffened plates show that the central displacement ratio of the distributed load to the concentrated load increased according to the decrease in the loading size, and that the ratio can be expressed as a function of the rigidity ratio for each rib space. The maximum displacement of the stiffened plate subjected to the distributed load did not appear at the center of the plate due to the local behavior, and the increasing ratio of the maximum displacement to the central displacement can be expressed as a function of the rigidity ratio for each rib space. Orthotropic plate analysis can achieve more accurate results using the proposed functions, and the application of the functions to examples of a different aspect ratio and support condition shows good accuracy. Therefore, using the functions proposed in this study, the central and maximum displacements can easily be achieved in the orthotropic plate analysis of stiffened plates subjected to the distributed load.

• Geotechnical Engineering
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• v.14 no.4
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• pp.117-128
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• 1998

Solid mattress foundation using geogrid has often been used on soft grounds to increase the bearing capacity, and its effect has received much recognition. Geogrid-mattress system is the method of construction which increases the bearing capacity and the effect of controlling settlement by dispersing load to wider foundation through its stiffness. But ifs mechanism has not been examined exactly yet. considered to be influential factors in the experiments. As a result of the experiments, the characteristic of dispersing stress under mattress foundations was understood and the way of calculating the bearing capacity in designing the mattress foundations was suggested.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.107-115
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• 2002

A parametric study has been conducted to evaluate the effects of finite element modeling methods on the internal loads, sizing and the weight of the multi-spar aircraft wing structures. The wing is idealized into total 18finite element models and subjected to 4typical external load conditions. An automatic sizing algorithm based on MSC/NASTRAN and MSC/PATRAN is developed. The results show that the critical part affection the internal loads and weight of the structure is wing skin. Effect of modeling of the spar and rib on the structural behavior is not manifest. On the contrast to the general expectation, the models using the bending-resistant elements show the heavier weight than ones by the elements without bending stiffness. From this results, designers of multi-spar wing are recommended to construct the finite element model considering the bending stiffness, or to check the characteristics of the structure before modeling.

• Computational Structural Engineering
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• v.11 no.1
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• pp.191-204
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• 1998

The general formulation for free vibration and stability analysis of unsymmetric thin-wared space frames is presented in case where the shear deformation effects are neglected. The kinetic and total potential energies are derived by applying the extended virtual work principle, introducing displacement parameters defined at the arbitrarily chosen axis and including warping deformation and second order terms of finite semitangential rotations. In formulating the finite element procedure, cubic Hermitian polynomials are utilized as shape functions of the two node space frame element. Mass, elastic stiffness, and geometric stiffness matrices for the unsymmetric thin-walled section are evaluated, and load-correction stiffness matrices for off-axis distributed loadings are considered. In order to illustrate the accuracy and practical usefulness of this formulation, finite element solutions for the free vibration and stability problems of thin-walled beam-columns and space frames are presented and compared with available solutions.

• Journal of the Korean Geotechnical Society
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• v.32 no.5
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• pp.15-26
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• 2016

Dam and embankment are very important civil structures. Grouting is widely used to repair and maintain dam and embankment, and it is important to evaluate the effect of grouting for dam safety. The non-destructive method based on determination of wave velocity in the dam or embankment is effectively used to evaluate grouting effect because wave velocity is identical with stiffness and grouting increases local stiffness in a dam. In this paper, HWAW (Harmonic wavelet analysis of waves) method was applied to evaluate the grouting effect. HWAW method can determine two-dimensional shear wave velocity map with good spatial resolution and the shear velocity profile by the proposed method is sensitive to a variation of stiffness of target system. Through numerical simulation and field tests, the applicability of HWAW method in determining grouting effect is shown.

• Journal of Aerospace System Engineering
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• v.13 no.6
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• pp.52-59
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• 2019

The rotor blade is a key component that generates the lift, thrust, and control forces required for helicopter flight by the torque transmitted through the hub and the blade pitch angle control, and should be designed to factor vibration characteristics so that there is no risk of resonance with structural safety. In this study, the structural design of the main rotor blade for MPUH(Multi-Purpose Unmanned Helicopter) was conducted and the sectional stiffness measurement of the fabricated blade was performed. The evaluation of the vibration characteristics of the main rotor system was then conducted factoring the measured stiffness distribution. The interior of the rotor blade comprised of the skin, spar, and torsion box, and carbon and glass fiber composites were applied. The Ksec2D program was applied to predict the stiffness of blade, and the results were compared to the measured data. CAMRADII, a comprehensive rotorcraft analysis program, was applied to investigate the natural frequency trends and resonance risks due to the rotor rotation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.84-91
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• 2019

For the goal of the proposal for optimum position of offset outrigger system, a structural schematic design of 70 stories building was carried out, using the general structure analysis program of MIDAS-Gen. In this research, the primary factors of this analysis research were the shear wall stiffness, the frame stiffness, the outrigger stiffness, the stiffness of column linked in outrigger system, etc. To achieve the aim of this study, we analyzed and studied the lateral displacement in top level, the force distribution of outrigger, the existing model of optimal outrigger location, and so on. This paper proposed the optimal position of offset outrigger system. Furthermore it is considered that the study results can be useful in getting the structure engineering data for seeking the optimal position of offset outrigger in the tall building.

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.509-516
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• 2013

In this paper, performance based design of coupling beam using non-linear static analysis is proposed considering probability distribution of flexural and shear strength in order to develop flexural hinge. This method considers post-yielding behavior of coupling beam and stress redistribution of system. It can verify the reduced effective stiffness to meet the current design requirement based on linear analysis. It also evaluates the lateral displacement under service load (un-factored wind load) properly. In addition, it can optimize the coupled shear wall system by taking stress redistribution between members into account. For a simplified 30-story building, non-linear static (push-over) analysis was performed and the structural behavior was checked at performance point and several displacement steps. Furthermore, system behavior according to the amount of reinforcement and depth of coupling beam was explored and compared each other.

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.161-170
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• 2002

This paper describes a systematic way of simultaneously identifying the ambient pore pressure and the rigidity index $(=G/s_u)$ of soil by applying an optimization technique to the early part of piezocone dissipation test result. An analytical solution developed by Randolph & Wroth(1979) was implemented in normalized from to express the build-up and dissipation of excess pore pressures around a piezocone as a function of the rigidity index. An ambient pore pressure and optimal rigidity index were determined by minimizing the differences between theoretical and measured excess pore pressure curves using optimization technique. The effectiveness of the proposed back-analysis method was examined against the well-documented performance of piezocone dissipation tests(Tanaka & Sakagami, 1989), from the viewpoints of proper determination of selected target parameters and saving of test duration. It is shown that the proposed back-analysis method can evaluate properly the ambient pore pressure and the rigidity index by using only the early phase of the dissipation test data. Also, it is shown that the proposed back-analysis method permits the horizontal coefficient of consolidation to be identified rationally. Consideration for strain level of back-analyzed rigidity index shows that it corresponds to at least intermediate to large strain level.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.489-492
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• 2011

장대레일 궤도의 부동구간에서 발생되는 과도한 축력은 혹서기 궤도의 좌굴을 유발시켜 주행하는 열차의 안정성을 위협할 수 있다. 궤도 제원을 제외한 압축응력과 관련된 레일온도 인자, 궤도 강성과 관련된 도상저항력, 궤도의 초기결함인 궤도틀림과 같은 인자들은 기후조건, 궤도 운영조건, 유지관리조건 등에 의해 임의적으로 변동되는 불확실성이 높은 궤도 매개변수이다. 그러므로 장대레일 궤도의 좌굴은 불확실성이 높은 현상임을 알 수 있다. 따라서 궤도 매개변수들의 불확실성 및 임의성을 합리적으로 고려하기 위해서는 확률론적 접근방법의 적용이 필수적이라 할 수 있다. 본 논문에서는 기존 본 연구진에 의해 개발된 장대레일 궤도의 좌굴확률 평가시스템을 이용하여 장대레일 축력을 산정하기 위한 필수요소인 중립온도의 확률분포 특성에 따른 좌굴 안정성을 분석하였다.