• Proceedings of the KSR Conference
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• 2005.11a
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• pp.1165-1170
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• 2005

In order to perform the spatial buckling analysis of the curved beam element with nonsymmetric thin-walled cross section, exact static stiffness matrices are evaluated using equilibrium equations and force-deformation relations. Contrary to evaluation procedures of dynamic stiffness matrices, 14 displacement parameters are introduced when transforming the four order simultaneous differential equations to the first order differential equations and 2 displacement parameters among these displacements are integrated in advance. Thus non-homogeneous simultaneous differential equations are obtained with respect to the remaining 8 displacement parameters. For general solution of these equations, the method of undetermined parameters is applied and a generalized linear eigenvalue problem and a system of linear algebraic equations with complex matrices are solved with respect to 12 displacement parameters. Resultantly displacement functions are exactly derived and exact static stiffness matrices are determined using member force-displacement relations. The buckling loads are evaluated and compared with analytic solutions or results by ABAQUS's shell element.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2642-2649
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• 2023

A real-time unmeasured dynamic response prediction process for the nuclear power plant pressure pipeline is proposed and its performance is tested in the test-loop system (KAERI). The aim of the process is to predict unmeasurable or unreachable dynamic responses such as acceleration, velocity, and displacement by using a limited amount of directly measured physical responses. It is achieved by combining a well-constructed finite element model and robust inverse force identification algorithm. The pressure pipeline system is described by using the displacement-pressure vibro-acoustic formulation to consider fully filled liquid effect inside the pipeline structure. A robust multiphysics modal projection technique is employed for the real-time sensor synchronized prediction. The inverse force identification method is also derived and employed by using Bathe's time integration method to identify the full-field responses of the target system from the modal domain computation. To validate the performance of the proposed process, an experimental test is extensively performed on the nuclear power plant pressure pipeline test-loop under operation conditions. The results show that the proposed identification process could well estimate the unmeasured acceleration in both frequency and time domain faster than 32,768 samples per sec.

• Computational Structural Engineering
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• v.9 no.4
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• pp.107-115
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• 1996

Displacement response is one of the important parameter to determine vibration characteristics of bridge structure. Reliable estimate of displacement response is obtained economically from integration of measured acceleration data in frequency domain. Proper sampling rate of frequency in discretization process of measured acceleration is proposed. Comparison of integrated and directly measured displacement response from laboratory experiment for a cantilever beam shows good agreement each other. Mode shape obtained from estimated displacement response also closely match with analytical result, thus the developed method is proved to be effective in practical use.

• Structural Engineering and Mechanics
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• v.40 no.1
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• pp.121-148
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• 2011

Closed form solutions for equilibrium and flexibility matrices of the Mindlin-Reissner theory based eight-node rectangular plate bending element (MRP8) using Integrated Force Method (IFM) are presented in this paper. Though these closed form solutions of equilibrium and flexibility matrices are applicable to plate bending problems with square/rectangular boundaries, they reduce the computational time significantly and give more exact solutions. Presented closed form solutions are validated by solving large number of standard square/rectangular plate bending benchmark problems for deflections and moments and the results are compared with those of similar displacement-based eight-node quadrilateral plate bending elements available in the literature. The results are also compared with the exact solutions.

• Structural Engineering and Mechanics
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• v.33 no.4
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• pp.485-502
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• 2009

A new 8-node serendipity quadrilateral plate bending element (MQP8) based on the Mindlin-Reissner theory for the analysis of thin and moderately thick plate bending problems using Integrated Force Method is presented in this paper. The performance of this new element (MQP8) is studied for accuracy and convergence by analyzing many standard benchmark plate bending problems. This new element MQP8 performs excellent in both thin and moderately thick plate bending situations. And also this element is free from spurious/zero energy modes and free from shear locking problem.

• Journal of Power System Engineering
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• v.19 no.2
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• pp.22-26
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• 2015

The main objective of this work is to estimate the fluid flow of a proportional valve. The study is based on the classical compressible flow theory and the computations with the help of CFD based commercial software - ANSYS CFX. The fluid flow with the movement of spool along the sleeve is simulated. To change the spool moving from 0.4mm to 2.0mm, the moving mesh method with different condition of orifice is considered here. The results show that it is the highest at the 80 % (1.6mm) opening and at the 20 % (0.4mm) opening, is the lowest.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.43-44
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• 2022

Recently, there is a demand for a fast and efficient method for measuring displacement during construction or maintenance of new buildings. As the number of safety accidents caused by structural collapse increases, the integrated management plan of the measurement and management system has become a platform and data is shared with stakeholders, so that it is possible to establish safety management in advance according to the displacement of the structure.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.4
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• pp.345-351
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• 2003

Due to increasing legal and market demands for safety in the automotive design process, the design of integrated seat is important more and mote because it should satisfy the conflict between stronger and lower weight for safety and environmental demands. In this study for crash simulations, the numerical simulations have been carried out using the explicit finite element program LS-Dyna according to the FMVSS 210 standard for safety test of seat. Since crash simulations are very time-consuming and a series of simulations that does not lead to a better result is very costly, the optimization method must be both efficient and reliable. As a result of that, statistical approaches such as design of experiments and response surface model have been successfully implemented to reduce time-consuming LS-Dyna simulations and optimize the safety and environmental demands together with nonlinear optimization algorithm. Design of experiments is used lot exploring the design space of maximum displacement and total weight and for building response surface models in order to minimize the maximum displacement and total weight of integrated seat.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.6
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• pp.583-591
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• 2011

Accurate observation results of dynamic displacements are essential to the protection of civil structures. In this study, we evaluated the optimal methods of the RTK/GPS Accelerometer integration through comparison and analysis of several experiments results. Two methods will be used to calculate the dynamic displacements from the results of the acceleration data as well as two integration methods for measuring the dynamic, static, and quasi-static displacements by incorporating the displacement results from the RTK-GPS and Accelerometer. By using a Cantilever Beam and LVDT measurement, we were able to ensure that the different displacement comparisons would be reliable and accurate. As a results from experiments, the accelerometer processing method applied by use of accelerometers data was filtering with the double integral using FIR band-pass filter which is most optimal for assessing the dynamic displacements. Also, the integrated method using extracting substitution displacements is suitable for measuring synthetically the dynamic static and quasi-static displacements of civil structures with RTK-GPS and accelerometer.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.478-485
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• 2002

The shape memory alloys (SMAs) are often used in smart materials and structures as the active components. Their ability to provide a high recovery force and a large displacement has been used in many applications. In this paper the radial displacement of an externally pressurized elliptic composite cylinder where SMA liner or strips actuators are bonded on its inner or outer surface is investigated numerically. The elliptic composite cylinders consisting of an inlet duct system with SMAs are designed and analyzed to determine the feasibility of such a system for the removal of stiffeners from an externally pressurized duct of an aircraft inlet. The deformations caused by prestrained SMAs placed on either surface of an elliptic composite cylinder are studied when activated. The externally pressurized elliptic composite cylinders with the SMA actuators were analyzed using the 3-D finite element method incorporated with 3-D SMA behaviors. The results show that the role of stiffeners may be switched by the activated light SMA actuators.