• Computational Structural Engineering
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• v.10 no.3
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• pp.167-174
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• 1997

Engineers must be aware of possible sources of chaotic behavior. They may render conventional design predictions untrustworthy and potentially unsafe because of the sensitivity to initial conditions. Dynamic responses of a spherical shell subjected to impulsive loading which act on the center are analyzed using the finite element method. The chaotic responses are identified by the standard methods, such as displacement-time histories, Poincare maps, and phase diagrams. The responses are chaotic, but, not so sensitive to the initial conditions, and the characteristics of responses are not changed with time, in contrast to the case of the responses of beam. The Poincare points scattered in the limited area represent that the responses are chaotic, but do not show the geometric structures. The snap-through phenomena of the shell to the side of the direction of the load or of the opposite direction, is analysed by using the energy diagram.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.300-303
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• 2009

본 논문에서는 유체-구조물 상호작용(Fluid-Structure interaction;FSI)에 관한 새로운 수치적 접근 방법의 제안과 타당성 검토가 목적이다. 기존의 유체 관내 유동에서는 유체-구조물 상호작용방법을 이용하여 해석하였으나 해석과정과 수치적 효율성에 문제점이 있다. 본 논문은 다공질 매체 거동을 이용하여 관내 유체 유동해석이 제안된다. 제안된 기법은 기존의 방법이 갖는 모델링의 어려움을 개선하고, 비교적 복잡한 과정이 수행되어 많은 계산 시간이 요구되어지는 수치적 효율성이 개선되었다. 또한 다공질 매체 거동에서 중요요소인 침투성과 유체-구조물 상호작용의 중요요소인 유체와 구조물경계의 마찰사이의 관계가 도출되었다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.04a
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• pp.13-18
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• 1992

구조물의 동적실험을 통하여 얻은 하중과 거동에 대한 시간기록을 분석하여, 구조계의 동 특성계수들을 추정하는 기법에 대하여 연구하였다. 실험과정 및 해석모형과정의 오차를 고려하기 위하여, 하중기록과 구조거동기록간의 관계를 추계론적 자동회기 및 이동평균모형(Stochastic Auto-Regressive and Moving-Average (ARMAX) Model)음 사용하여 모형화하였다. 미지의 ARMAX 계수행렬들은 순차적 예측오차기법을 사용하여 추정하였으며, 계수추정기법의 효율성을 증진시키기 위하여, Exponential Data Weighting, Global Data Weighting 및 Square Root Estimation 기법을 활용하였다. 다중거동측정계의 예제해석을 통하여 이의 효율성을 분석하였다.

• Composites Research
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• v.23 no.4
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• pp.1-6
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• 2010

The dynamicresponse of biomimetic composites mimicking nacre under low velocity impact is investigated. The composites have hierarchical structures with a staggered pattern consisting of a protein and a mineral. To analyze the impact response of the composites, the finite element method is used. The effects of the hierarchical structures of the compositeson the dynamic response are examined. It is shown that the maximum stress, displacement and contact force in the composite subjected to low velocity impact decrease as the level of structural hierarchy increases.

• Computational Structural Engineering
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• v.11 no.4
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• pp.209-218
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• 1998

고장력강이 구조강재로서 널리 사용되고 있다. 구조물의 극심한 하중을 받게되면 최종강도에 도달할 때까지 좌굴을 동반하게 된다. 그러므로, 고장력강판의 좌굴에 대한 정확한 평가가 중요한 설계기준이 되고 있다. 그러나, 고장력강을 효율적으로 사용하기 위해서는 좌굴허용설계를 도입할 수 있도록 판구조물의 판두께가 얇아져야 한다. 따라서, 박판구조물의 합리적인 설계를 하기 위해서는 좌굴후거동해석이 매우 중요하다. 그러므로, 본 논문에서는 호장증분법을 이용하여 압출하중을 받는 박판구조물의 초기좌굴후거동과 2차좌굴강도에 대하여 규명하였다. 특히, 호장증분법을 좌굴정에서의 하중경로를 추정하기 위하여 적용하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.692-695
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• 2010

일반적으로 모델개선에서는 부재단위의 강성을 파악하기 때문에 구조물의 취약부인 부재단부의 손상이 집중될 경우 손상의 형태를 세밀히 파악하기 어려우며 손상된 구조물의 거동을 정확하게 모사하기 어려운 단점이 있었다. 이를 해결하기 위해서는 부재 단부에 발생한 손상을 고려할 수 있는 좀 더 정밀한 해석 모델을 통한 모델개선이 필요하다. 본 연구에서는 부재 단부에 반강접 접합을 가지는 해석모델을 사용해 모델 개선을 실시하고 이를 통해 접합부의 손상 평가와 손상 구조물의 거동을 파악하였다. 제안된 방법을 5층 1경간의 RC 벽식 실험체의 손상탐지에 적용하였으며 그 결과 부재단위 모델을 사용할 때보다 더욱 정확하게 구조물의 손상을 평가하고 거동을 모사할 수 있었다.

• Computational Structural Engineering
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• v.8 no.3
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• pp.59-66
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• 1995

The dynamic responses of structure under impulsive loading have been investigated according to its duration, based on the theory of viscoplasticity which can appropriately represent the effects of plasticity and rheology simultaneously. The viscoplastic model has been implemented into the two-dimensional finite element system to solve plane stress, plane strain or axi-symmetric problems, and the implicit integration scheme, of which solutions are unconditionally stable for relatively large time step length, has been developed to simulate visoplastic straining with deriving the explicit relationship between stress and strain at a material point level. After simulation, one carefully concludes that the duration as well as magnitude of impulsive loading plays an important role in design of structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1541-1549
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• 2013

This study investigates the response of structures to tunnelling-induced ground movements in sand ground, varying tunnel excavation condition (tunnel depth and diameter), tunnel construction condition (ground loss), ground condition (loose sand and dense sand). Four-story block-bearing structures have been used because the structueres can easily be characterized of the extent of dmages with crack size and distribution. Numerical parametric studies have been used to investigae of the response of structures to varying tunnelling conditions. Numerical analysis has been conducted using Discrete Element Method (DEM) to have real cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The results of structure responses from various parametric studies have been integrated to consider tunnel excavation condition, tunnel construction condition, and ground condition and provided as a relationship chart. Using the chart, the response of structures to tunnelling can easily be evaluated in practice in sand ground.

• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.503-513
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• 2007

The seismic responses of a building are affected by the connection characteristics that have effects on structural stiffness. In this study, push-over analysis and time history analysis were performed to estimate structural behavior of 2D eight-story unbraced steel structures with partially restrained composite connections using a nonlinear dynamic analysis program. Nonlinear $M-{\theta}$characteristics of connection and material inelastic characteristics of composite beam and steel column were considered. The idealization of composite semi-rigid connection as fully rigid connection yielded an increase in initial stiffness and ultimate strength in the push-over analysis. In time history analysis, the stiffness and hysteretic behavior of connections have effects on base-shear force, maximum story-drift and maximum moment in beams and columns. For seismic waves with PGA of 0.4 g, the structure with the semi-rigid composite connections shows the maximum story-drift with less than the life safety criteria by FEMA 273 and no inelastic behavior of beam and column, whereas in the structure with rigid connections, beams and columns have experienced inelastic behaviors.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.361-373
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• 2010

Bridges constructed without any expansion joint or bridge bearing are called integral abutment bridges. They integrate the substructure and the superstructure. Possible deformation of the superstructure, due to changes in temperature for example, is prevented by the bending of the piles placed at the lower part of the abutment. This study examines the behavior of integral abutment bridges through soil-pile interaction modeling method and proposes an appropriate modeling method. Also, it assesses the behavior characteristics of the superstructure and piles of integral abutment bridges through parametric study. Soil condition around the pile, abutment height, and pile length were selected as parameters to be analyzed. Structural analysis was conducted while considering the interactions of soil-pile and temperature change-earth pressure on the abutment. Comparative behavior analysis through soil-pile interaction modeling showed that elastic soil spring method is more appropriate in evaluating the behavior of integral abutment bridges. The parametric study showed the tendency that as the soil stiffness around the pile increases, the moment imposed on the superstructure increases, and the displacement of the piles decreases. In addition, it was observed that as the bridge height increases, the earth pressure on the abutment increases and that in turn affects the behavior of the superstructure and piles. Also, as the length of the pile increased, the integral bridge showed more flexible behavior.