• 한국해양공학회지
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• 제15권1호
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• pp.26-30
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• 2001

Up to now, Most studies of hydroelasticity are about frequency domain analysis. Those aren't suited for analysis of the landing take-off, and dropping of aircraft on a structure. So, the concern of this paper is the transient behavior of a VLFS subjected to dynamic load, induced by airplane landing and take-off. To predict the added mass, damping coefficient, and wave exciting force, the source-dipole distribution method was used in the frequency domain. The responses are accomplished by using the FEM scheme. A time domain analysis method is based on the Newmark β method to pursue the time step procedure, taking advantage of memory effect function for hydrodynamic effects.

• Structural Engineering and Mechanics
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• 제82권2호
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• pp.191-204
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• 2022

A three-mass vehicle model including one rigid mass and two unsprung masses is adopted to predict the vehicle-bridge interaction (VBI) and to establish the nonlinear coupled governing equations. To overcome the numerical instability and large computation problems concerning the vehicle-bridge system, the perturbation method is used to convert the nonlinear coupled governing equations into a set of linear uncoupled equations. Formulas for bridge's natural frequencies considering both the VBI and the dynamic responses of bridge and vehicle are proposed. Compared with the numerical results obtained by the Newmark-β method, the theoretical solutions for natural frequencies and dynamic responses are validated. The effects of the important factors of unsprung mass, vehicle damping, surface irregularity on the natural frequencies and dynamic responses of bridge and vehicle are discussed, based on the theoretical solutions.

• 대한토목학회논문집
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• 제9권1호
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• pp.11-23
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• 1989

본 논문에서는 guyed tower의 mooring system에 관한 수치해석결과를 제시하였다. 가상일의 원리와 유한요소법을 사용하여 기본식을 유도하였으며 케이블의 기하학적 비선형성을 고려하였다. 유체의 항력과 관성력은 Morrison식을 사용하여 고려하였으며 비선형 운동방정식의 해는 Newton-Raphson방법과 Newmark-${\beta}$ 방법을 사용하여 구하였다. Tower와 mooring line의 부착점에서의 초기경사각, 인장력, clump weight를 집중하중으로 이상화 시키는 종래의 해석방법의 문제점도 아울러 고찰하였다. 수치해석 예를 통하여 본 논문에서의 해석방법의 정당성을 입증하였다.

• Computational Structural Engineering : An International Journal
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• 제2권1호
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• pp.43-50
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• 2002

This paper presents a method to predict dynamic responses of floating bodies in the time domain. Because of the frequency-dependence of the radiation wave forces, the memory effect must be taken into account when the responses are evaluated in the time domain. Although the formulations firstly developed by Cummins (1962) have been well-known for this purpose, the effective numerical procedure has not been established yet. This study employs FFT (Fast Fourier Transform) algorithm to evaluate the memory effect function, and the equations of motion of an integro-differential type are solved by Newmark-β method. Numerical examples for a truncated circular cylinder have indicated the effectiveness of the proposed numerical procedure.

• 대한조선학회논문집
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• 제45권2호
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• pp.168-174
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• 2008

To calculate the fluid-structure interaction(FSI) problem rationally, it should be the basic technology to analyse each domain of fluid and structure accurately. In this paper, a new FSI analysis algorithm was introduced using the 3D solid finite element for structural analysis and CFD code based on the HCIB method for viscous flow analysis. The fluid and structural domain were analysed successively and alternatively in time domain. The structural domain was analysed by the Newmark-b direct time integration scheme using the pressure field calculated by the CFD code. The results for example calculation were compared with other research and it was shown that those coincided each other. So we can conclude that the developed algorithm can be applied to the general FSI problems.

• 대한토목학회논문집
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• 제13권5호
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• pp.13-18
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• 1993

본 논문의 목적은 LRB 기초분리장치가 설치된 교량의 내진효과를 해석하는 것이다. 기초분리방법은 지진력이 구조물에 전달되기 전에 그 영향을 최소화시키는 방법으로 현재 건물, 발전소, 교량 등의 구조물에 실용화되고 있다. 본 연구에서는 대표적인 기초분리장치인 Lead Rubber Bearing이 설치된 교량의 단순화된 모델을 개발하고 여러 크기의 LRB에 대하여 지진의 영향을 해석하였다. 단순화된 교량모델의 운동방정식을 Newmark ${\beta}$ 방법에 의해 시간이력해석을 수행하였다. 기초분리장치의 모델로는 이중선형성을 갖는 스프링을, 교각모델로는 비선형성 및 강성저하를 고려한 Q-HYST모델을 사용하였다. 해석예로 미국 네바다주에 소재한 Rose Creek 교량에 대한 남북방향 El Centro지진(1940)의 영향을 해석하였다. 상부구조 횡방향처짐, 교각연성 및 교각 밑면 전단력을 구하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제23권2호
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• pp.201-209
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• 1999

This paper presents a general analytical method for analyzing mechanical unbalance response of unbalanced electromagnetic forces produced in induction motors with an eccentric rotor and a phase unbalance. The equations to be solved are a set of second order differential equations which give matrices with periodic coefficients that are a function of time due to the unbalanced electro-magnetic force. Unbalance response is processed by Newmark $\beta$ method. Two examples are given including an industrial application. The results show that the method proposed is satisfactory.

• 한국해양공학회지
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• 제28권5호
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• pp.371-377
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• 2014

In this study, the hydrodynamic characteristics of various types of jack-up legs for a wind turbine installation vessel were analyzed. Using the modified Morison equation, the wave and current excitation forces on the jack-up legs were calculated. A modal analysis was performed to predict the dynamic responses for various types of jack-up legs. The Newmark-beta time integration scheme was used to solve the equation of motion in waves in the time domain. The maximum displacement and maximum bending stress were computed for four different types of legs, and their results were compared to select an optimum leg type. Finally, a six-leg jack-up rig with the selected optimal legs was modeled, and its natural period and hydrodynamic behaviors were evaluated.

• Earthquakes and Structures
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• 제16권3호
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• pp.359-368
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• 2019

This paper focuses on the study of dynamic analysis of thick plates resting on Winkler foundation. The governing equation is derived from Mindlin's theory. This study is a parametric analysis of the reflections of the thickness / span ratio, the aspect ratio and the boundary conditions on the earthquake excitations are studied. In the analysis, finite element method is used for spatial integration and the Newmark-${\beta}$ method is used for the time integration. While using finite element method, a new element is used. This element is 17-noded and it's formulation is derived from using higher order displacement shape functions. C++ program is used for the analyses. Graphs are presented to help engineers in the design of thick plates subjected to earthquake excitations. It is concluded that the 17-noded finite element is used in the earthquake analysis of thick plates. It is shown that the changes in the aspect ratio are more effective than the changes in the aspect ratio. The center displacements of the reinforced concrete thick clamped plates for b/a=1, and t/a=0.2, and for b/a=2, and t/a=0.2, reached their absolute maximum values of 0.00244 mm at 3.48 s, and of 0.00444 mm at 3.48 s, respectively.

• Advances in nano research
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• 제12권6호
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• pp.567-581
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• 2022

The free and forced vibration in addition to electric energy harvesting of a piezoelectric disk resting on two-parameter foundation modeled by modified couple stress as well as Kirchhoff plate theory is probed. The governing equations and boundary conditions are obtained using Hamilton's principle. Then, the free and forced vibration are solved using numerical solutions, generalized differential quadrature method (GDQM) and Newmark-beta method. The forced vibration is resulted from a base excitation load. Also, the possible voltage which can be harvested from this system is obtained using generalized integral quadrature method. The validity of the formulation and solution procedure is confirmed using a compassion study. The impact of parameters such as length effect, inner to outer radius ratio, and foundations parameters on the free and forced vibration as well as energy harvesting is investigated in detail. This paper can be a basis for future studies in the area of piezoelectric harvesters in small scales.