• Steel and Composite Structures
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• 제4권4호
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• pp.317-331
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• 2004

The lateral sway of a multi-storey steel frame should be limited so as to ensure the comfort of the occupants and for the protection of mechanical and architectural systems. This paper investigates the applicability of Schueller's equation for predicting sway of rigid steel frames, and proposes a number of modifications to the equation so that it can produce results that are almost identical to those given by accurate Finite Element (FE) analysis. The behaviour of irregular steel frames has also been studied and proposals are made so that Schueller's Equation can also be used to predict sway of such frames.

• 한국전산유체공학회지
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• 제14권1호
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• pp.86-95
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• 2009

A kinetic theory analysis is used to study the ultra-thin gas flow field in gas bearings. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations are made for flows inside micro-channels of backward-facing step, forward-facing step, and slider bearings. The results are compared well with those from the DSMC method. The present method does not suffer from statistical noise which is common in particle based methods and requires less computational effort.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.283-286
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• 2012

The analytical model determining the unknown parameters of reaction rate equation which is necessary to simulate the combustion phenomena of energetic materials is proposed. The relationship between detonation velocity and size effect of energetic materials is derived from simplified JWL++ model. Theoretical model is used to investigate the combustion characteristics of certain energetic materials before running Hydrocode by pre-determination of unknown parameter, b. When b=0.8, the behavior of HANFO gunpowder is in the form of concave-up and ANFO explosives has the concave-down form in case of b=1.5. The analytical model provides efficient and highly accurate results rather than previous method which simulated the unconfined-rate-stick via the numerical means.

• 한국공간구조학회논문집
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• 제15권1호
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• pp.47-55
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• 2015

This paper shows the simplified equation to predict the ultimate moment capacity and corresponding rod stress in reinforced concrete beam with external post-tensioning rods. Because the stress of external post-tensioning rod depends on the beam deflection, the previous analytical model for post-tensioned beams requires a tedious iteration process. Also, the stress equations in ACI code or other researchers' models are suitable only for internal tendons in concrete beams. In this study, given the lack of analytical approaches to predict the nominal stress of the external unbonded rod, a simple and robust equation has been proposed for externally post-tensioned concrete beams. It is concluded that the proposed equation predicted the stress of external steel rods in post-tensioned concrete beams reasonably well.

• Structural Engineering and Mechanics
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• 제43권2호
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• pp.211-223
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• 2012

This paper deals with large deformation post-buckling of a linear-elastic and hygrothermal beam with axially nonmovable pinned-pinned ends and subjected to a significant increase in swelling by an alternative method. Analytical approximate solutions for the geometrically nonlinear problem are presented. The solution for the limiting case of a string is also obtained. By coupling of the well-known Maclaurin series expansion and orthogonal Chebyshev polynomials, the governing differential equation with sinusoidal nonlinearity can be reduced to form a cubic-nonlinear equation, and supplementary condition with cosinoidal nonlinearity can also be simplified to be a polynomial integral equation. Analytical approximations to the resulting boundary condition problem are established by combining the Newton's method with the method of harmonic balance. Two approximate formulae for load along axis, potential strain for free hygrothermal expansion and periodic solution are established for small as well as large angle of rotation at the end of the beam. Illustrative examples are selected and compared to "reference" solution obtained by the shooting method to substantiate the accuracy and correctness of the approximate analytical approach.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.275-278
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• 2004

In this paper, the fracture strength of the surface damaged laminates was predicted by applying the fracture strengths of the unflawed and flawed laminates. For prediction, the theoretical equation about the fracture strength of laminates was simplified applying classical laminate theory and was applied to the surface damaged laminates. Lagace's and Tsai's experimental data were used for verifying the theoretical equation. Moreover, to verify the theoretical prediction, an experiment was performed. Surface unflawed laminate and flawed laminates were fabricated and the experiments were made and these results were compared with theoretical predictions. The specimens' fiber direction was same to the tensile direction and the theoretical predictions and the experimental results were showed good agreement. Therefore, by this equation, the fracture strength of structures made of composites will be able to be predicted when the surface of the structures was damaged.

• Journal of Mechanical Science and Technology
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• 제20권2호
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• pp.177-184
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• 2006

An orbital design method of the formation initialization based on the relative orbital element method is presented. It firstly constructed the relative motion equation of the satellite formation flying in terms of the leader and followers' orbital elements. Then the equation was simplified when the orbit eccentricity of the leader satellite was small. And according to the satellites' mission, a general design method for the relative trajectory was proposed. The advantage of this method is that one can get a very simple analytical formula of each follower satellite's orbital elements when the orbital eccentricity of the leader satellite is zero. The simulation results show that the method is effective.

• 한국기계가공학회지
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• 제13권5호
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• pp.90-97
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• 2014

This paper presents a simplified dynamics model, dynamics simulations, and computed torque control experiments of the Delta high-speed parallel robot. Using the typical Newton-Euler method, a simplified but accurate dynamics model with practical assumptions is derived. Accuracy and fast calculations of the dynamics are essential in the computed torque control for high-speed applications. It was found that the simplified dynamics equation is in very god agreement with the ADAMS model, and the calculation time of the inverse kinematics and inverse dynamics is about 0.04 msec. From the dynamics simulations, the cycle trajectory along the y-axis requires less peak motor torque and a lower angular velocity and less power than that along the x-axis. The computed torque control scheme can reduce the position error by half as compared to a PD control scheme. Finally, the developed Delta parallel robot prototype, half the size of the ABB Flexpicker robot, can achieve a cycle time of 0.43 sec with a 1.0kg payload.

• Structural Engineering and Mechanics
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• 제10권1호
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• pp.67-79
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• 2000

Critical loads and load-carrying capacities for steel scaffolds used as shoring systems were compared using computational and experimental methods in Part I of this paper. In that paper, a simple 2-D model was established for use in evaluating the structural behavior of scaffold-shoring systems. This 2-D model was derived using an incremental finite element analysis (FEA) of a typical complete scaffold-shoring system. Although the simplified model is only two-dimensional, it predicts the critical loads and failure modes of the complete system. The objective of this paper is to present a closed-form solution to the 2-D model. To simplify the analysis, a simpler model was first established to replace the 2-D model. Then, a closed-form solution for the critical loads and failure modes based on this simplified model were derived using a bifurcation (eigenvalue) approach to the elastic-buckling problem. In this closed-form equation, the critical loads are shown to be function of the number of stories, material properties, and section properties of the scaffolds. The critical loads and failure modes obtained from the analytical (closed-form) solution were compared with the results from the 2-D model. The comparisons show that the critical loads from the analytical solution (simplified model) closely match the results from the more complex model, and that the predicted failure modes are nearly identical.

• 한국강구조학회 논문집
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• 제11권3호통권40호
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• pp.271-279
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• 1999

보와 기둥과의 반강접에 관한 최근 연구로서 기둥 면과 T-stub 플랜지 사이에 격리재를 설치하는 개량된 T-stub 요소를 개발하고 있다. 개량된 T-stub에 대한 비탄성 해석을 수행하였으며, 그 결과를 실험값과 비교 분석하였다. 비탄성 해석 방법은 기둥 면과 격리재 사이에 간격요소(gap element)를 적용하고, 고력볼트에 초기 응력을 부여하여 실험값과 잘 일치하는 결과를 보인다. 실무에서의 설계와 해석에 적용할 수 있는 약산식으로서 T-stub의 초기 강성도와 압축하중에 의한 소성내력에 관한 설계식을 제시한다.