• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.474-479
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• 2004

According to our previous study, it is confirmed that the Petrov-Galerkin natural element method (PGNEM) completely resolves the numerical integration inaccuracy in the conventional Bubnov-Galerkin natural element method (BG-NEM). This paper is an extension of PG-NEM to two-dimensional nonlinear dynamic problem. For the analysis, a constant average acceleration method and a linearized total Lagrangian formulation is introduced with the PG-NEM. At every time step, the grid points are updated and the shape functions are reproduced from the relocated nodal distribution. This process enables the PG-NEM to provide more accurate and robust approximations. The representative numerical experiments performed by the test Fortran program, and the numerical results confirmed that the PG-NEM effectively and accurately approximates the nonlinear dynamic problem.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.110-115
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• 1997

In this work, the constant average acceleration, which is a fundamental feature of the trapezoidal rule, is investigated and generalized. Using the generalization of average acceleration concept, a higher order accurate and unconditionally stable time-integration method is developed. The linear approximate of the present methods is exactly the same as the famous trapezoidal rule. To observe the accuracy and stability of the method, several numerical tests are performed and the results are compared with the results from the trapezoidal rule and the exact solution. From the numerical tests, it has been known that the present method has a higher order accuracy and unconditional stability.

• 대한토목학회논문집
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• 제12권4_1호
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• pp.9-21
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• 1992

논문에서는 주구조물의 기초와 부구조물의 지지점에 설치된 감진장치가 구조물의 지진응답 감소에 미치는 영향을 분석하였다. 여러가지 지진하중의 특성에 따른 감진장치가 설치된 주구조물과 부구조물의 거동을 비교분석하였으며, 이때 사용된 해석모델은 고정기초 구조물에 지지점이 고정된 부구조물, 감진기초 구조물에 지지점이 고정된 부구조물, 고정기초 구조물에 지지점 감진장치가 설치된 부구조물과 같은 세가지이다. 부구조물의 응답계산에서는 주구조물과 부구조물의 상호작용을 고려하였다. 계산에 사용한 수치적분방법은 constant average acceleration 방법이며, 이 방법과 축소행렬방법을 이용한 전산프로그램(KBISAP)을 사용하였다. 또한 지진하중에 대한 구조물의 지면에 대한 상대변위를 제한시키기 위하여 여러가지 지진하중에 대한 구조물의 가속도와 변위의 상관관계를 계산하여 감진장치의 적합한 수평강성을 분석하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.348-355
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• 2001

A computer program named \"NLDA-BIS\", which runs under the MATLAB environment, is developed fur seismic response analysis of base isolated structures. This program can explicitly model the various nonlinear isolation elements such as elastomeric bearings, sliding bearings and general viscous dampers, and so on. Newmark'\`s constant average acceleration method fur calculating the responses in time domain and the iterative pseudo-force method for treating the nonlinear isolation forces are adopted. For capturing the hysteretic behavior of isolation elements, the modified Wen's equations are adopted and solved by the numerical differentiation formula method. To verify the validity of the developed program, the seismic responses of a six-story reinforced concrete base isolated structure are calculated and compared with results obtained by the program \"3D-BASIS\" developed at the State University of New York at Buffalo which is the most widely used code far analyzing isolated structures today.ed structures today.

• Structural Engineering and Mechanics
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• 제13권5호
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• pp.569-589
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• 2002

In performing the dynamic analysis, the step size used in a step-by-step integration method might be much smaller than that required by the accuracy consideration in order to capture the rapid chances of dynamic loading or to eliminate the linearization errors. It was first found by Chen and Robinson that these difficulties might be overcome by integrating the equations of motion with respect to time once. A further study of this technique is conducted herein. This include the theoretical evaluation and comparison of the capability to capture the rapid changes of dynamic loading if using the constant average acceleration method and its integral form and the exploration of the superiority of the time integration to reduce the linearization error. In addition, its advantage in the solution of the impact problems or the wave propagation problems is also numerically demonstrated. It seems that this time integration technique can be applicable to all the currently available direct integration methods.

• 대한토목학회논문집
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• 제12권2호
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• pp.35-42
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• 1992

본 논문에서는 주 구조물 내에 설치된 기기의 지지점에 감진계통을 도입함으로써 지진하중에 대한 기기의 응답감소효과를 연구하였으며, 효율적인 해석을 수행하기 위해 구조물-기기 상호작용 고려 및 축소 행렬방법을 이용한 전산프로그램(KBISAP)을 개발하였다. 지지점에 감전장치가 설치된 기기의 지진하중에 대한 응답감소 효율성을 평가하기 위해 세가지 해석모델, 즉 고정기초구조물 상의 지지점이 고정된 기기, 감진기초구조물 상의 지지점이 고정된 기기 및 고정기초구조물 상의 지지점에 감진계통이 설치된 기기를 채택한 예제해석 결과, 본 논문에서 채택한 방법이 일반적인 고정기초구조물은 물론 감진기초구조물 상에 설치된 기기의 지진하중에 대한 응답감소 보다 더 효율적임을 알 수 있었다. 따라서 본 방법은 기기의 응답감소는 물론 중요한 기기의 안전성 향상에 효과적이다.

• 대한조선학회논문집
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• 제58권6호
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• pp.400-406
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• 2021

The primary effect of the far-field underwater explosion (UNDEX) is the whipping of the ship hull girder. This paper aims to verify why inelastic effects should be considered in the whipping response estimations from the UNDEX simulations. A navy ship was modeled using Timoshenko beam elements over the ship length uniformly keeping the constant midship section modulus. The transient UNDEX pressure was produced using two types of the Geers-Hunter doubly-asymptotic models: compressible and incompressible fluids. Because the UNDEX model based on incompressible fluid assumption provided more increased fluid volume acceleration in the bubble phase, the incompressible fluid-based UNDEX model was adopted for the inelastic whipping response analyses. The non-linear hull girder bending moment-curvature curve was used to embed inelastic effects in the UNDEX analyses where the Smith method was applied to derive the non-linear stiffness. We assumed two stand-off distances to see more apparent inelastic effects: 40.5 m and 35.5 m. In the case of the 35.5 m stand-off distance, there was a statistically significant inelastic effect in terms of the average of peak moments and the average exceeding proportional limit moments. For the conservative design of a naval ship under UNDEX, it is recommended to use incompressible fluid. In the viewpoint of cost-effective naval ship design, the inelastic effects should be taken into account.