• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.833-838
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• 2001

The objectives of this study are to investigate effective stiffness of circular reinforced bridge columns and to provide reasonable effective stiffness equations for seismic design to the current Korean Bridge Design Standard. The material nonlinear analysis was conducted for 5184 columns of which variables were the concrete compressive stress, the steel yielding stress, the longitudinal steel location parameter, the longitudinal steel ratio, the axial load level, and the diameter of section. The current Korean Bridge Design Standard generally used the gross section stiffness because of unclear provision, it may be non-conservative because of being evaluated greater design seismic force and less design displacement than those of the abroad provision. Therefore, the proposed effective stiffness equations include three variables such as : the longitudinal steel location parameter, the longitudinal steel ratio, and the axial load ratio. Two equations of effective stiffness are proposed which may be used for earthquake force estimation and for earthquake displacement estimation, respectively.

• Steel and Composite Structures
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• 제1권4호
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• pp.377-392
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• 2001

The response of multi-story building structures to lateral loads, mainly due to earthquake and wind, is investigated for preliminary design purposes. Emphasis is placed on structural systems consisting of rigid and braced steel frames. An attempt to gain a qualitative understanding of the influence of bending and shear stiffness distribution on the deformations of such structures is made. This is achieved by modeling the structure with a stiffness equivalent Timoshenko beam. It is observed that the conventional stiffness distribution, dictated by strength constraints, may not be the best to satisfy deflection criteria. This is particularly the case for slender structural systems with prevailing bending deformations, such as flexible braced frames. This suggests that a new approach to the design of such frames may be appropriate when serviceability governs. A pertinent strategy for preliminary design purposes is proposed.

• 한국소음진동공학회논문집
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• 제16권9호
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• pp.919-925
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• 2006

An accurate mathematical model for complex stiffness of the pneumatic spring would be necessary for an efficient design of a pneumatic spring used in vibration isolation tables for precision instruments such as optical devices or nano-scale equipments. A diaphragm, often employed for prevention of air leakage, plays a significant role of complex stiffness element as well as the pressurized air itself Therefore, effects of the diaphragm need to be included in the dynamic model for a more faithful description of dynamic behavior of pneumatic spring. But the complex stiffness of diaphragm is difficult to predict In an analytical way, since it is a rubber membrane of complicated shape in itself. Moreover, the diaphragm should be expandable in response to pressurization inside a chamber, which makes direct measurement of complex stiffness of diaphragm extremely difficult. In our earlier research, the complex stiffness of diaphragm was indirectly measured, which was just to eliminate the theoretical stiffness of pressurized air from the measured complex stiffness of the pneumatic spring. In order to reflect complex stiffness of inflated diaphragm on the total stiffness at the initial design or design improvement stage, however. it is required to be able to predict beforehand. In this paper, how to predict the complex stiffness of inflated rubber diaphragm by commercial FE codes (e.g. ABAQUS) will be discussed and the results will be compared with the indirectly measured values.

• 한국정밀공학회지
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• 제28권1호
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• pp.89-95
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• 2011

High stiffness frame design for a spine manipulation device was developed in this research. For the safety of a spinal manipulation, high stiffness of the device is required. A finite element (FE) model of the device frame is created and validated by measured vibration data. Parameters are suggested for high stiffness design of the frame. Based on the Taguchi design of experiment (DOE), a practical set of design parameter values is suggested.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.844-849
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• 2006

Accurate modeling of complex dynamic stiffness of the pneumatic springs is crucial for an efficient design of vibration isolation tables for precision instruments such as optical devices or nano-technology equipments. Besides pressurized air itself, diaphragm made of rubber materials, essentially employed for prevention of air leakage, plays a significant contribution to the total complex stiffness. Therefore, effects of the diaphragm should be taken care of precisely. The complex stiffness of an inflated diaphragm is difficult to predict or measure, since it is always working together with the pressurized air. In our earlier research, the complex stiffness of a diaphragm was indirectly estimated simply by subtracting stiffness of the pressurized air from measurement of the total complex stiffness for a single chamber pneumatic spring. In order to reflect dynamic stiffness of inflated diaphragm on the total stiffness at the initial design or design improvement stage, however, it is required to be able to predict beforehand. In this presentation, how to predict the complex stiffness of inflated rubber diaphragm by commercial FE codes(e.g. ABAQUS) will be discussed and the results will be compared with the indirectly measured values.

• 대한기계학회논문집A
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• 제21권1호
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• pp.180-187
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• 1997

A formula for estimating the elastic stiffness of TW-HDS with a uniformly tapered width from w$_{0}$ to w$_{1}$ over the length, has been analytically derived based on Euler beam theory and Castigliano's theorem. Elastic stiffnesses of the TW-HDSs designed in the same dimensional design spaces as the KOFA HDSs have been estimated from the derived formula, in addition, a sensitivity study on the elastic stiffness of the TW-HDSs has been carried out. Analysis results show that elastic stiffnesses of the TW-HDSs have been by far higher than those of the KOFA HDSs, and that, as the effects of axial and shear force on the elastic stiffness have been 0.15-0.21%, most of the elastic stiffness is attributed to the bending moment. As a result of sensitivity analysis, the elastic stiffness sensitivity at each design variable is quantified and design variables having remarkable sensitivity are identified. Among the design variables, leaf thickness is identified as that of having the most remarkable sensitivity of the elastic stiffness.

• 한국강구조학회 논문집
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• 제10권1호통권34호
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• pp.63-72
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• 1998

강구조물의 강성설계법을 실용적인 변위조절법인 구조물량재분배기법과 강도설계법을 결합하여 개발하였다. 본 연구에 사용된 재분배기법은 최적화기법에 의하여 유도되었으며, 최적화문제의 에너지이론에 근거한 부재변위기여도를 이용하여 정식화되었다. 이러한 재분배기법에 의한 변위조절은 설계민감도계수의 계산 그리고 구조재해석을 필요로 하지 않는 특성을 가지고 있다. 변위조절을 위한 구조물량의 재분배에 의한 부재응력의 재분배 효과는 허용응력설계법에 준한 강도설계모듈에 의하여 조절되었다. 개발된 강성설계법을 3차원 트러스 구조물의 설계에 적용하였다.

• 한국소음진동공학회논문집
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• 제17권10호
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• pp.901-906
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• 2007

Lightweight body due to the decrease of panel thickness and reinforcing member might cause low stiffness. On the other hand, high stiffness body requires an increase of mass. Front pillar section area has been decreased for increasing the driver's visual field. Global vehicle stiffness is affected by stiffness distribution ratio between upper part and lower part at a side body structure. This paper describes a process used to evaluate the stiffness distribution ratio based on strain energy. In addition, optimum design schemes are presented for high stiffness and lightweight body structure considering the investigated stiffness distribution ratio.

• 한국해양공학회지
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• 제15권1호
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• pp.98-103
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• 2001

This paper is conducted to compare the seismic design standard of a bridge column such as the Korean Bridge Design Standard(KBDS), EC 8, NZS 3101 and ATC 32. The KBDS adopted the seismic design requirements in 1992. The earthquake magnitude in Korea is compared with those in the west coast of the USA. It may be said that the current seismic design requirements of the KBDS provides design results, that are too conservative especially for transverse reinforcement details and amounts in reinforced concrete columns. This fact usually creates construction problems in concrete casting, due to congestion of transverse reinforcement. Furthermore, the effective stiffness; $I_{eff}$ depends on both the axial load P/$A_gF_{ck}$ and the longitudinal reinforcement ratio $A_{st}/A_g, so it is the conservative to use the effective stiffness I$_{eff}$ than the gross section stiffness Ig. Seismic design for the transverse reinforcement content of the concrete column was analyzed and considered to have an extreme-fiber compression strain, response modification factor, axial load and effective stiffness etc.c.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.921-924
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• 2005

Diesel generator sets with resilient mounts often experience resonances by major excitations which come from diesel engine and their foundation with rigid body modes. Because their natural frequency is determined by moment of inertia and stiffness of resilient mount vibration problems are resolved by changing location and stiffness of resilient mounts. But the calculated natural frequencies are inaccurate due to uncertainty of the inertia and mount stiffness. So this result can be useless on the design stage. In this paper, the stiffness of mount is evaluated on result from mount stiffness test in laboratory and generator set vibration test and a simple calculation method for moment of inertia is proposed. Based on these data, the procedure to select optimized mount stiffness and location on the design stage is set up.