• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.3
• /
• pp.281-292
• /
• 1999

지반-기초 상호작용계를 해석할 때 실제로 지반은 다양한 지반종류와 다층으로 형성되어 있으므로 지반 특성의 변화를 고려해야 한다. 초기의 대부분의 상호작용계의 정·동적 해석은 지반의 복잡한 성질을 역학적으로 탄성거동을 한다고 가정한 Winkler 지반모델 혹은 지반을 등방성이고 균질한 반무한 탄성체로 가정한 반무한 탄성지반 모델로 보아 수행되었다. 본 연구는 유한 요소법을 이용하여 지반-기초 상호작용계의 동적 거동을 해석하기 위해 기초는 4절점 후판요소를 사용하고 지반은 지반특성을 고려할 수 있도록 8절점 6면체 요소를 사용하였고, 지반의 감쇠효과 및 지반특성을 고려한 지반-기초 상호작용계의 동적 거동을 유한요소법으로 해석하고 지반의 영향범위를 결정하는 것이다.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.1 no.1
• /
• pp.87-92
• /
• 1989

In this study, the nonlinear dynamic model of the systems which include the offshore structure, the surrounding sea water in terms of the added mass, the foundation in terms of frequency independent springs, dashpots, and the floating ice feature with its hydrodynamic added mass, are proposed for the problem of the large ice floes impact. Dynamic Analysis is performed on two site conditions, sand site and silt site, and on two seasons, winter and summer, for various ice floe velocities. As a result of study, Ice floes from energy balenced method is lower than that from dynamic modeling on sand site, and higher than the on silt site.

• Journal of Korean Society of Steel Construction
• /
• v.23 no.3
• /
• pp.397-404
• /
• 2011

In this paper, a research for the dynamic wheel loads of a 3D vehicle model, which relates to a tire-enveloping model, is carried out. A single truck with four axles is modeled as a 10-D.O.F. vehicle by modeling both contact length of tires and pitching of tandem spring axles. The dynamic equations of the vehicle are obtained using the Lagrange's equation, the solution of the equations is calculated by Newmark-${\beta}$ method. The validity of the developed 3D vehicle model is demonstrated by comparing results obtained from the proposed method with those from experimental data. The maximum impact factors of tire force are evaluated according to the various step bumps on which a 24-ton dump truck is running.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.9
• /
• pp.67-75
• /
• 2006

A fully nonlinear model accounting for swirling effect has been applied in analyzing the dynamic response for a classical swirl injector. The current work applied highly accurate Boundary Element Methods (BEMs) in assessing its static and dynamic characteristics. On the basis of moving surface treatment method and surface instability study, which are obtained from the previous static characteristics analysis in pressure-swirl injectors, this work was expanded for analyzing the dynamics of a classical swirl injector. The dynamic response through injector components for disturbed inflow condition was investigated. The modified code was validated from comparison with the theoretical result for a typical swirl injector. Clearly the simulated result shows the interesting characteristics of swirl injectors to provide either amplification or damping of the input disturbance through each component. These results give promise in applying the current model to nonlinear dynamic characteristics of swirl injectors.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.13 no.1
• /
• pp.75-85
• /
• 2000

When applying a system identification technique, which incorporates an experimental model to a corresponding finite element model of a structure, one of the major problems is the large difference in the numbers of degrees of freedom (dof) between the two models. While there are large number of dofs in a finite element model, the number of measurement points is practically limited. So it is very difficult to incorporate them. Especially rotational dofs are hard to measure. In this study a method is presented for estimating structural dynamic responses at unmeasurable locations in frequency domain. The proposed method is tested numerically and the feasibility for practical application has been demonstrated through an example structure under moving loads, where translational and rotational dofs of beam at a center point are estimated from the partial measurements of responses at accessible points.

• Composites Research
• /
• v.19 no.1
• /
• pp.1-8
• /
• 2006

Prediction of damage caused by low-velocity impact in laminated composite plate is an important problem faced by designers using composites. Not only the inplane stresses but also the interlaminar normal and shear stresses playa role in estimating the damage caused. But it is well known that the conventional approach based on the homogenization has the limit in description of damage. The work reported here is an effort in getting better predictions of dynamic behavior and damage in composite plate using DNS approach. In the DNS model, we discretize the composite plates through separate modeling of fiber and matrix for the local microscopic analysis. In the view of microscopic mechanics with DNS model, interlaminar stress behaviors in the inside of composite materials are investigated and compared with the results of the homogenized model which has been used in the conventional approach to impact analysis. Also the multiscale model based on DNS concept is developed in order to enhance the effectiveness of impact analysis, and we present the results of multiscale analysis considering micro and macro structures simultaneously.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.3
• /
• pp.35-51
• /
• 2008

In this paper, the application of the DSC model to the analysis of liquefaction potential is examined through experimental and analytical investigations. For more realistic description of dynamic responses of saturated sands, the DSC model was modified based on the dynamic effective stress path and excess pore pressure development. Both static and cyclic undrained triaxial tests were performed for sands with different relative densities and confining stresses. Based on test results, a classification of liquefaction phases in terms of the dynamic effective stress path and the excess pore pressure development was proposed and adopted into the modified DSC model. The proposed methods using the original and modified DSC models were compared with examples with different relative densities and confining stresses. Based on the comparisons between the predicted results using the original and modified DSC models and experimental data, the parameters required to define the model were simplified. It was also found that modified model more accurately simulate initial liquefaction and dynamic responses of soil under cyclic undrained triaxial tests.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.14 no.2
• /
• pp.225-235
• /
• 2001

본 연구는 물리·역학적 특성을 고려한 점탄성 감쇠기의 수치모델에 의한 강뼈대구조물의 지진응답개선에 관해서 조사하고자 한다. 온도변화에 의한 감쇠기 이력거동에 미치는 영향을 고려하기 위하여, 점탄성 감쇠기의 모델은 온도-주기 등가원리와 더불어 개선된 분수도함수법에 기초하여 정식화하였다. 본 감쇠기 모델의 알고리즘을 일반화된 강뼈대구조물의 비선형 동적 해석 프로그램에 추가하였다. 강뼈대구조물에 대한 해석 예를 통하여, 제시된 모델에 의한 점탄성 감쇠기의 지진응답개선에 관한 효과를 확인할 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.3
• /
• pp.224-231
• /
• 2009

In this study, an aerodynamic performance analysis code has been developed as a part of rotorcraft comprehensive program. Airloads on rotor blades are calculated based on the blade element theory with look-up tables of aerodynamic coefficients of 2-D airfoils. In order to calculate rotor induced inflow, various inflow prediction methods such as linear inflow, dynamic inflow, prescribed wake and free wake model are integrated into the present module. The aerodynamic characteristics of each method are compared and validated against available experimental data such as Elliot's inflow distribution and sectional normal force coefficients of AH-1G.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.17 no.4
• /
• pp.389-403
• /
• 2004

This study presents the structural model modification based on the modal data such as natural frequencies and mode shapes. Preliminary structural model can be obtained using design drawings and field measurement, and therefore the deteriorated stiffness of a structure and the effect of the boundary conditions are difficult to be evaluated in preliminary analysis model, and the preliminary model can be modified using structural response data including static and/or dynamic characteristics. In this study, the structural model is modified based on the structural modal data using genetic algorithm. Modal testing were carried out for Imjin River Bridge and Hangjoo Bridge, the modal properties were estimated using modal identification techniques, and finally the structural models were updated using genetic algorithm. The modified structural model could give us more reliable structural analysis results and therefore those can be used for structural performance evaluation such as load carrying capacity and seismic capacity.