• Structural Engineering and Mechanics
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• 제83권5호
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• pp.609-615
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• 2022

A numerical approach for dynamic stability analysis of sandwich plates has been provided using Chebyshev-Ritz-Bolotin approach. The sandwich plate with porous core has been formulated according to a higher-order plate. All of material properties are assumed to be dependent of porosity factor which determines the amount or volume of pores. The sandwich plate has also been assumed to be under periodic in-plane loading of compressive type. It will be shown that stability boundaries of the sandwich plate are dependent on static and dynamical load factors, porosity factor, porosity variation and core thickness.

• Smart Structures and Systems
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• 제21권5호
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• pp.583-590
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• 2018

Nowadays, many tunnels have been commissioned for several decades, which require effective inspection methods to assess their health conditions. The ambient vibration test has been widely adopted for the damage identification of concrete structures. In this study, the vibration characters of tunnel lining shells built with forepoling method was analyzed based on the analytical solutions of the Donnell-Mushtari shell theory. The broken rock, foreploing, rock-concrete contacts between rock mass and concrete lining, was represented by elastic boundaries with normal and shear stiffness. The stiffness of weak contacts has significant effects on the natural frequency of tunnel lining. Numerical simulations were also carried out to compare with the results of the analytical methods, showing that even though the low nature frequency is difficult to distinguish, the presented approach is convenient, effective and accurate to estimate the natural frequency of tunnel linings. Influences of the void, the lining thickness and the concrete type on natural frequencies were evaluated.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.235-242
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• 2004

In this study numerical and experimental studies are conducted to examine the wave screening effectiveness of trenches. The numerical study is based on a finite element model of a "sandbox" with Lysmer-Kuhlemeyer-type absorbing boundaries. Using the model, the screening effectiveness of trench is studied for different trench dimensions and distance from source and receiver to trench. The results of the numerical modeling are compared with the results of the ultrasonic experiment which is performed on a acrylic block with a drilled rectangular cut. These results show that the screening effectiveness of the trench is nearly equal if the depth of trench is lager than 60 % of the surface wave length. If is also shown that if the distance between the trench and the source is lager than twice the surface wave length, the thickness of the trench does not affect the screening effectiveness.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.33-38
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• 2008

For the propagation of elastic waves in unbounded domains, absorbing boundary conditions at the fictitious numerical boundaries have been proposed. Paraxial boundary conditions(PBCs) which are kinds of absorbing boundary conditions based on paraxial approximations of the scalar and elastic wave equations not only lead to well-posed problem but also are stable and computationally inexpensive. But the complex mathematical forms of PBCs with partial derivatives complicate the application of those to finite element analysis. In this paper a penalty functional is newly proposed for applying PBCs into finite element analysis and the existence and uniqueness of the extremum of the proposed functional is demonstrated. The numerical verification of the efficiency is carried out through comparing PBCs with a viscous boundary condition.

• 전산구조공학
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• 제6권4호
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• pp.83-88
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• 1993

시간변수에 대하여 불연속성을 주는 시간불연속 Galerkin 방법을 유한요소법으로 해석하였다. 이 방법은 미분방정식 관점에서 지금까지 요소간에 연속성을 준 일반적 유한요소법과 다르게 임의의 시간요소를 선택, 매 시간단계에서 요소경계에 불연속을 허락함으로서 해의 정확성을 높이고 무조건의 안정을 주는 상미분방정식의 해법인 것이다.

• 전산구조공학
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• 제9권4호
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• pp.165-172
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• 1996

들보나 아치, 판재 그리고 쉘과 같은 박판구조물의 경계부근의 매우 좁은 영역에는 경계층이 존재하는데, 이 영역에서 해는 급격하게 변화하는 특이 거동을 나타낸다. 유한요소법을 이용하여 이러한 물체의 거동을 해석하는 경우, 이런 특이성을 묘사하기 위해 유한요소 체눈패턴이 대단히 중요한 역할을 한다. 이 논문은 경계층에 대한 이론적 해석과 최적의 체눈패턴을 형성하기 위한 가이드를 제시한다. 또한 이론적인 결과를 입증하는 예제도 소개하고자 한다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.411-418
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• 2004

Using a level set method we develop a shape optimization method applied to energy flow problems in steady state. The boundaries are implicitly represented by the level set function obtainable from the 'Hamilton-Jacobi type' equation with the 'Up-wind scheme.' The developed method defines a Lagrangian function for the constrained optimization. It minimizes a generalized compliance, satisfying the constraint of allowable volume through the variations of implicit boundary. During the optimization, the boundary velocity to integrate the Hamilton-Jacobi equation is obtained from the optimality condition for the Lagrangian function. Compared with the established topology optimization method, the developed one has no numerical instability such as checkerboard problems and easy representation of topological shape variations.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.279-287
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• 2003

This paper deals with a comparative study on coupling of Element-free Galerkin(EFG) method and Infinite Element(IE) by IE's shape function. In this study, mapped infinite elements(mapped IE) and decay function infinite elements(decay IE) are coupled with the EFG method. A coupling procedure of EFG-Mapped IE is much easier to be integrated than a coupled EFG-Decay IE. A coupled EFG-IE method used well-defined functions to preserve the continuity and linear consistency on the interface of the EFG region and IE region. Several benchmark problems are solved to verify the effectiveness and accuracy of the coupling algorithms by IE's shape function. The numerical results show that the developed algorithms work well for the elastic problems with infinite boundaries.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.480-485
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• 2004

If a wall separates the bounded and unbounded spaces, then the wall's role in transporting the acoustic characteristics of the two spaces is not well defined. In this paper, we attempted to see how the acoustic characteristical of two spaces are really affected by the spatial characteristics of the wall. In order to understand coupling mechanism, we choose a finite space and a semi-infinite space separated by the flexible or rigid wall and an opening. A volume interaction can be occurred in structure boundary and a pressure interaction can be happened in the opening boundary. For its simplicity, without loosing generality, we use rather simplified rectangle model instead of generally shaped model. The source impedance is presented to the various types of boundaries. The distributions of pressure and active intensity are also presented at the cavity and structure-dominated modes. The resulting modification, shifts of mode1 frequencies and changing of standing wave patterns to satisfy both coupled boundary conditions and governing equations, are presented.

• Selected Papers of The Society of Naval Architects of Korea
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• 제1권1호
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• pp.52-64
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• 1993

There exist many frame structural systems having some attachments reducible to damped spring-mass systems, concentracted masses and spring supports. For free and forced vibration analyses of such a system an analytical method based on the receptance method is presented. A framed structure having attachments is considered as a combined system composed of various Timoshenko beam and bar elements and the attachments. So, the vibration characteristics of the system are calculated by synthesizing receptances and Support Displacement Transfer Ratio (SDTR) of beam and bar elements In spectral and/or closed forms, and receptances of the attachments. In forced vibration analysis, arbitrary excitation forces at a point on the structure and displacement excitations at boundaries are considered. Numerical investigations are carried out for verification of the presented method, and the results show good accuracy and very high computational efficiency.