• Journal of Ocean Engineering and Technology
• /
• v.27 no.2
• /
• pp.13-18
• /
• 2013

Most ships and offshore structures are equipped with a variety of pipes, which inevitably contain curved portions. The structural design of these pipes mostly relies on the commercial code, CAESAR-II, which was especially developed for the structural analysis of pipes. This study conducted stress analyses of the same pipe unit, including loops, using both CAESAR-II and MSC/NASTRAN, and compared the results to investigate the characteristics of CAESAR-II. A parametric study was then conducted of the various design variables of pipe loops using CAESAR-II to draw some useful information about the structural characteristics of the loops.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2010.04a
• /
• pp.674-677
• /
• 2010

본 논문에서는 지반에 매립된 파이프에서 전파되는 유도초음파의 종파 모드 특성을 분석하였다. 지상 배관과는 달리 매립 배관에서는 주변 매질로 유도초음파의 누설이 발생할 수 있으며, 이로 인하여 유도초음파의 감쇠가 상대적으로 커질 수 있다. 따라서 본 연구에서는 유도초음파의 여러 특성들 중 종파 모드의 감쇠 특성을 중점적으로 분석하였다. 감쇠에 영향을 미치는 지반의 파동 특성(밀도, 체적종파속도, 체적횡파속도)을 결정하기 위하여 포화도와 다짐을 고려하였다. 포화도가 증가할수록 지반의 체적종파속도와 체적횡파속도는 감소하며, 다짐된 지반은 밀도와 체적종파속도, 체적횡파속도를 증가시킨다. 이와 같은 조건으로 결정된 지반의 파동 특성치와 배관의 물성치를 바탕으로 유도초음파 종파 모드의 감쇠 곡선을 계산하고, 특성을 분석하였다. 결과적으로 포화도가 증가할수록 종파 모드의 감쇠는 감소하는 경향을 나타내었고, 다짐이 증가할 경우 감쇠는 전반적으로 증가하는 경향을 나타냄을 알 수 있었다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.10 no.1
• /
• pp.57-69
• /
• 1990

The static nonlinear analysis of offshore pipeline is carried out by the finite element method. The governing equilibrium equation are derived by the principle of minimum potential energy and the modified Newton-Raphson procedure is used to solve the system of nonlinear algebraic equation. Geometrically nonlinear beam elements and spring elements are utilized to model the pipeline, stinger, pipe supports and seabed simultaneously. The beam element developed can be used to model redundant structures. It provides for both the torsional deformation and elongation of pipeline, and permits the use of different physical properties in each principal direction. The validity of this method is investigated by comparing the results with these obtained by other methods.

• Journal of KSNVE
• /
• v.7 no.3
• /
• pp.489-498
• /
• 1997

In this paper, chaotic motions of a curved pipe conveying oscillatory flow are theoretically investigated. The nonliear partial differential equation of motion is derived by Newton's method. The transformed nonlinear ordinary differential equation is a type of Hill's equation, which has the external and parametric excitation with a same frequency. Bifurcation curves of chaotic motion of the piping systems are obtained by applying Melnikov's method. Numerical simulations are performed to demonstrate theoretical results and show the strange attractor of the chaotic motion.

• Journal of Ocean Engineering and Technology
• /
• v.8 no.2
• /
• pp.151-156
• /
• 1994

The equations of motion of a submarine pipeline with the internal flowing fluid and subject to hydrodynamic loadings are derived by using Hamilton's principle. Coupling between the bending and the longitudinal extension due to axial load and thermal expansion are considered. Coupling between the twisting and extension are not considered. The equations of motion are well agreed with the results which are derived by the vector method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.10a
• /
• pp.288-294
• /
• 1996

In this paper, Chaotic motions of a curved pipe conveying oscillatory flow are theoretically investigated. The nonlinear partial differential equation of motion is derived by Newton's method. The transformed nonlinear ordinary differential equation is a type of Hill's equation, which have the parametric and external excitation. Bifurcation curves of chaotic motion of the piping systems are obtained by applying Melnikov's method. Poincare maps numerically demonstrate theoretical results and show transverse homoclinic orbit of the chaotic motion.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.11a
• /
• pp.649-654
• /
• 2000

The non-linear differential equations of motion of a fluid conveying curved pipe are derived by making use of Hamiltonian approach. The extensible dynamics of the pipe is based on the Euler-Bernoulli beam theory. Some significant differences between linear and nonlinear equations and the basic analysis results are discussed. Using eigenfrequency analysis, it can be shown that the natural frequencies are changed with flow velocity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.983-986
• /
• 2005

Free vibration characteristics of a curved pipe conveying fluid is studied when the pipe is clamped at both ends. Using the perturbation method, the non-linear governing equations divided into two parts; the steady state non-linear equilibrium equations and the linearized equations of motion in the neighborhood of the equilibrium position. The natural frequencies are computed from the linearized equations of motion. In this study, the equilibrium positions are determined by two types of equations, i.e., (1) the non-linear equations, and (2) the equations obtained by neglecting the non-linear terms. The natural frequencies obtained from the non-linear equilibrium equations are compared to those obtained from the linearized equilibrium equations. From the results, as the fluid velocity increases, the equilibrium position should be determined from the nonlinear equations for the vibration analysis of the curved pipe conveying fluid.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2004.05a
• /
• pp.1157-1160
• /
• 2004

현재 사용되고 있는 대부분의 메신저는 서버에 로그 온할 때 패스워드를 RC5등으로 암호화해서 보내지만 패스워드 크래킹 프로그램들이 많이 알려져 있어 안전하지 못하다. 또한 로그 온한 후 통신하는 두 호스트들 간의 전송되는 정보가 아무런 보호 장치 없이 네트워크를 통해 전송되어 제3자에 의한 도청이 가능하게 된다. 따라서 전송되는 정보의 암호화를 포함하는 안전한 메신저 서비스의 필요성이 대두되고 있다. 본 논문에서 제안된 안전한 메신저는 동일한 키 사이즈를 갖는 다른 공개키 암호체계보다 훨씬 강하다고 알려져 있는 타원곡선 암호체계를 이용하여 빠르고 효율적이며 높은 안전도를 나타내는 패스워드 키 교환 방식을 설계하였고, 사용자간에 IPSec프로토콜을 사용하여 효율적인 데이터 전송이 가능하고 또한 보안성을 높이기 위한 방법으로 Host-to-Host간의 데이터가 인터넷에서 가상의 파이프를 통해 전달되도록 터널 모드를 제시하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.677-682
• /
• 2003

The non-linear dynamic characteristics of a semi-circular pipe conveying fluid are investigated when the pipe is clamped at both ends. To consider the geometric non-linearity for the radial and circumferential displacements, this study adopts the Lagrange strain theory for large deformation and the extensible dynamics based on the Euler-Bernoulli beam theory for slenderness assumption. By using the Hamilton principle, the non-linear partial differential equations are derived for the in-plane motions of the pipe, considering the fluid inertia forces as a kind of non-conservative forces. The linear and non-linear terms in the governing equations are compared with those in the previous study, and some significant differences are discussed. To investigate the dynamic characteristics of the system, the discretized equations of motion are derived form the Galerkin method. The natural frequencies varying with the flow velocity are computed fen the two cases, which one is the linear problem and the other is the linearized problem in the neighborhood of the equilibrium position. Finally, the time responses at various flow velocities are directly computed by using the generalized- method. From these results, we should to describe the non-linear behavior to analyze dynamics of a semi-circular pipe conveying fluid more precisely.