• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2001.09a
• /
• pp.348-355
• /
• 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.

• Proceedings of the KSR Conference
• /
• 2007.05a
• /
• pp.1062-1067
• /
• 2007

This study presents an experimental technique to monitor the dynamic behavior of the railway bridge system simultaneously using multiplexed fiber Bragg grating (FBG) sensors. The measuring quantities include stains, curvatures, vertical deflections, and vertical accelerations. The strains are directly measured from multiplexed FBG sensors at various locations of the test bridge followed by curvature calculations based on the plane section assumption. Vertical deflections are then estimated using the Bernoulli beam theory and regression analysis. Finally, vertical accelerations are obtained from the numerical differentiation in time domain. In order to verify the proposed method, several conventional electric strain gauges, displacement transducers, and accelerometers are installed at the mid-span of the bridge for comparisons. A test train is passed over the bridge to monitor the dynamic response of the bridge. The monitoring results show that the multiplexed FBG sensing system is able to capture the essential behavior of the test bridge while resolving wiring problem in practice.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.8
• /
• pp.1438-1445
• /
• 1992

A new and efficient method is presented to evaluate contact force and motion of an electric railway simple catenary-pantograph system. Overhead lines are regarded as simple strings, and hangers connected to the strings are replaced with concentrated forces acting on them. The displacement of strings due to concentrated forces caused by hangers and pantograph is expressed using Green's function. A system of linear algebraic equations in terms of unknown forces is derived based upon the compatibility requirement at the location of hangers and pantograph. This procedure is more analytic in formulation compared to the existing methods such as finite difference method or normal modes method, and it is expected to be more accurate. Present method has additional advantage that it requires neither numerical differentiation nor system eigenvalues.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.686-691
• /
• 2001

Structural optimization often require the evaluation of design sensitivities. The Semi Analytic method(SAM) is popular for shape optimization because this method has several advantages. But when relatively large rigid body motions are identified for individual elements, the SA method shows severe inaccuracy. In this paper, the improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes. Moreover, the error of the SA method caused by numerical difference scheme is alleviated by using a series approximation for the sensitivity derivatives and considering the higher order terms.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.4
• /
• pp.593-600
• /
• 2003

Structural optimization often requires the evaluation of design sensitivities. The Semi Analytic Method(SAM) fur computing sensitivity is popular in shape optimization because this method has several advantages. But when relatively large rigid body motions are identified for individual elements. the SAM shows severe inaccuracy. In this study, the improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes. Moreover. the error of the SAM caused by numerical difference scheme is alleviated by using a series approximation for the sensitivity derivatives and considering the higher order terms. Finally the present study shows that the refined SAM including the iterative method improves the results of sensitivity analysis in dynamic problems.

• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.602-606
• /
• 2000

A general procedure for the design sensitivity analysis of structural dynamic problems has been presented in frame of the FRF-based substructuring formulation. In the procedure, the direct differentiation method is used for the sensitivity formula. For a system response function, the proposed method gives a parametric design sensitivity formula in terms of the partial derivatives of the connection element properties and the transfer matrix of the subsystems. The derived design sensitivity formula is applied to a numerical example. The comparison of sensitivities derived by the proposed method and the finite difference method shows that the proposed method is efficient and accurate.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.11B
• /
• pp.1191-1199
• /
• 2009

As the Internet service evolves from the best effort data service to a multimedia service such as a mix of voice, data and video, a need for the guarantee of the quality of service to network services became one of the hot issues for the network operators. On the other hand, the introduction of the multimedia services over the IP network requires a managed differentiated service that adopts a prioritized treatment of packets. This incurs a need for a differentiated pricing scheme for the packets that receive different level of quality of service. This work proposes an analytic framework about packet pricing scheme for these services, and investigate the effect of service differentiation to the packet price for each class. Via numerical experiment, we validate our argument and illustrate the implication of the work.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.3
• /
• pp.110-117
• /
• 1998

A continuum-based configuration design sensitivity analysis method is developed for kinematically driven mechanical systems. The configuration design variable for mechanical systems is defined. The 3-1-3 Euler angle is employed as the orientation design variable. Kinematic admissibility conditions of configuration design change. Direct differentiation method is used to derive the governing equations of the design sensitivity. Numerical examples are presented to demonstrate the validity and effectiveness of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.40 no.9
• /
• pp.859-865
• /
• 1991

This paper presents a new shaoe optimal design method using Desing Sensitivity Analysis. Design Sensitivity, defined as the variation of the object function with respect to the design variables, is based on the total differentiation of the matrix equation obtained from discretization of governing equations with respect to design variables. Analysis of the various characteristics adn calculation of Design Sensitivity of optimization model are achieved by using finite or boundary element methods. The proposee algorithm is applied to the optimal shape design of high voltage electrode under specified conditions. It is shown, from the numerical results, that the algorithm is very useful for the optimal shape design of electric apparatus.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2001.10a
• /
• pp.159-166
• /
• 2001

Structural optimization often requires the evaluation of design sensitivities. The Semi Aanalytic method(SAM) for computing sensitivity is popular in shape optimization because this method has several advantages. But when relatively large rigid body motions are identified for individual elements, the SA method shows severe inaccuracy. In this paper, the improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes. Moreover, the error of the SA method caused by numerical difference scheme is alleviated by using a series approximation for the sensitivity derivatives and considering the higher order terms. Finally, this paper shows that the refined SA method including the iterative method improves the results of sensitivity analysis in dynamic problems.