• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.11
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• pp.1144-1151
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• 2012

A damage in structure alters its dynamic characteristics. The change is characterized by changes in the modal parameter, i.e., modal frequencies, modal damping value and mode shape associated with each modal frequency. Changes also occur in some of the structural parameters; namely, the mass, damping, stiffness matrices of the structure. In this paper, evaluation of changes in stiffness matrix of a structure is presented as a method not only for identifying the presence of the damage but also locating the damage. It is shown that changed stiffness matrix can be accurately estimated a sensitivity coefficient matrix derived from modifying mode shapes, First, with 4 story shear structure models, the effect of presence of damage in a structure on its stiffness matrix is studied. By using these analytical model, the effectiveness of using change of stiffness matrix in detecting and locating damages is demonstrated. To validate the predicted changing stiffness and its location, the obtained results are compared to the reanalysis result which shows good agreement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.367-373
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• 1995

터빈 blade에 대해 기존의 stiffness matrix법과 finite element법에 의한 방식을 개선하여 수치계산을 행한 결과 다음의 결론을 얻었다. 1)stiffness matrix법을 적용하기 위해 th.2 order로 방정식을 유도하였으며, 회전시의 원심력의 영향 및 blade의 기하학적 형상이 수식에 고려되었다. 이 방법으로 blade의 여러 parameter의 영향을 간단히 계산할 수 있다. 계산결과는 다른 논문의 결과와 잘 일치함을 보였다. 또한, 원심력의 영향에 있어서는 th.2 order의 계산결과가 기존의 변형된 th.1 order의 결과보다 더 정확한 결과를 얻을 수 있다. 2) FEM 이용시 계산시간을 단축하면서 정확한 결과를 얻기 위해 blade를 간단히 modeling하여, 기하학적인 형상과 회전시의 영향을 고려한 식을 유도하였다. 본 방법의 결과는 타 문헌과 일치하였다.

• Steel and Composite Structures
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• v.24 no.1
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• pp.53-63
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• 2017

The paper presents the simplified matrix stiffness method for analysis of composite and prestressed beams. The method is based on the previously developed "exact" analysis method that uses the mathematical theory of linear integral operators to derive all relations without any mathematical simplifications besides inevitable idealizations related to the material rheological properties. However, the method is limited since the closed-form solution can be found only for specific forms of the concrete creep function. In this paper, the authors proposed the simplified analysis method by introducing the assumption that the unknown deformations change linearly with the concrete creep function. Adopting this assumption, the nonhomogeneous integral system of equations of the "exact" method simplifies to the system of algebraic equations that can be easily solved. Therefore, the proposed method is more suitable for practical applications. Its high level of accuracy in comparison to the "exact" method is preserved, which is illustrated on the numerical example. Also, it is more accurate than the well-known EM method.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.137-145
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• 1997

A two-dimensional program for the analysis of bimaterial inclusion has been developed using the bound- ary element method. In order to study the effects of circular inclusion on the stress field of the crack tip, numerical analysis was performed for the straight crack of finite length around the symmetric circular inclusion whose modulus of elasticity was different from that of the matrix material. In the case of inclusion whose stiffness was smaller than that of the matrix material, the stress intensity factor was found to increase as the crack enamated. The stress intensity factor was uninfluenced from the radial change in inclusion and remained constant for the stiffness equivalent to the matrix materials, where as it decreased for the inclusion with larger stiffness. For the vareation in the distance of the inclusion, a small increase in the stress intensity factor was observed for the case with small or equal stiffness compared with the matrix materials. The inclusion with larger stiffness showed a gradual decrease in the strss intensity factor as the crack emanated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.30-37
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• 2014

In this study, we studied how to perform the structural analysis which need a large-capacity flash memory with the computer program when the flash memory storage of a personal computer has no enough room for the analysis of structure. As one of the solutions of this problem, the blocking method of stiffness matrix, which is a method that stiffness matrix is divided by a few blocks and each block is sequentially used for the calculation of matrix decomposition, is proposed and an algorithm available in computer program is derived on the method. Finally, A structural analysis program (sNs) based on this study is developed and the correctness and efficiency of the algorithm is founded through some examples which are fundamental in structural analysis.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.2
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• pp.94-103
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• 1991

This study was carried out to investigate the engineering characteristics of the R.C circular ring sector plate with various boundary conditions and then to propose a rational and paraical method for application of finite element method to R.C structures. The stiffness matrix of the circular ring sector plate was obtained by using the multi-base coordinate system in which the base-coordinate systems were constructed for each nodal point of the quadrilateral element in order to reflect the complicated boundary conditions conveniently and correctly. The R.C element stiffness matrix was constructed by adding the stiffness coefficients of the steel-bar element into the plate bending element stiffness matrix. Herein, the steel-bar element was treated as the common beam element. Using the above method, the effects of steel-bar can be considered without increasing of the numbers of element and nodal points.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.3
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• pp.482-492
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• 2004

Recently. the market trend for marine diesel engine has involved the lower running speeds. larger stroke/bore ratio and higher combustion pressure. Consequently, because of the flexible engine shafting system due to the larger mass. inertia and the more elasticity, the complicated coupled torsional-axial vibrations have occurred in the operating speed range. Also, the vibrations act as an excitation on the hull-structural vibration. To predict the vibration behavior with more accuracy and reliability. many studies have proposed the several kinds of method to calculate the stiffness matrix of crankshaft. However, most of these methods have a weak point to spend much time on three dimensional modeling and meshing work for crankshaft. Therefore. in this work. the stiffness matrix for the crankthrow is calculated using the energy method (Influence Coefficient Method, ICM) with the each mass having 6 degree of freedom. Its effectiveness is verified through the comparison with the stiffness matrix obtained by using the finite element method (FEM) and measured results for actual ships propulsion system.

• Korean Journal of Mathematics
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• v.6 no.1
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• pp.17-26
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• 1998

In this paper, we briefly study the condition number of stiffness matrix with $h$-version and analyze it with $p$-version of the finite element method.

• Structural Engineering and Mechanics
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• v.51 no.4
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• pp.601-625
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• 2014

Based on continuum mechanics and the principle of virtual displacements, incremental total Lagrangian formulation (T.L.) and incremental updated Lagrangian formulation (U.L.) were presented. Both T.L. and U.L. considered the large displacement stiffness matrix, which was modified to be symmetrical matrix. According to the incremental updated Lagrangian formulation, small strain, large displacement, finite rotation of three dimensional Timoshenko fiber beam element tangent stiffness matrix was developed. Considering large displacement and finite rotation, a new type of tangent stiffness matrix of the beam element was developed. According to the basic assumption of plane section, the displacement field of an arbitrary fiber was presented in terms of nodal displacement of centroid of cross-area. In addition, shear deformation effect was taken account. Furthermore, a nonlinear finite element method program has been developed and several examples were tested to demonstrate the accuracy and generality of the three dimensional beam element.

• Journal of Power System Engineering
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• v.3 no.1
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• pp.74-79
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• 1999

This paper describes formulation for algorithm of time historical response analysis of vibration for straight-line structure. This method is derived from a combination of the transfer stiffness coefficient method and the Newmark method. And this present method improves the computational accuracy of the transient vibration response analysis remarkably owing to several advantages of the transfer stiffness coefficient method. We regarded the structure as a lumped mass system here. The analysis algorithm for the time historical response was formulated for the straight-line structure containing crooked, tree type system. The validity of the present method compared with the transfer matrix method and the Finite Element Method for transient vibration analysis is demonstrated through the numerical computations.