• Journal of Power System Engineering
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• v.9 no.1
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• pp.42-49
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• 2005

The vibration analysis of a rectangular plate with stiffeners is formulated by using the transfer stiffness coefficient method (TSCM). This method is based on the concept of the successive transmission of stiffness coefficients which are defined as the relationship between the force vector and the displacement vector at an arbitrary nodal line. In order to confirm the validity of the present method, bending vibration analysis for a rectangular plate with stiffener is carried out on a personal computer by using the present method and the finite element method (FEM). Through comparing computational results of the TSCM and the FEM, the effectivness of the TSCM from the viewpoint of computational cost, that is, computational time and storage is demonstrated.

• International Journal of Railway
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• v.7 no.2
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• pp.46-56
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• 2014

The superstructure of the railway track undertakes the forces that develop during train passage and distributes them towards its seating. The track panel plays a key role in terms of load distribution, while at the same time it maintains the geometrical distance between the rails. The substructure and ballast undergo residual deformations under high stresses that contribute to the deterioration of the so-called geometry of the track. The track stiffness is the primary contributing factor to the amount of the stresses that develop on the substructure and is directly influenced by the fastening resilience. Four methods from the international literature are used in this paper to calculate the loads and stresses on the track substructure and the results are compared and discussed. A parametric investigation of the stresses that develop on the substructure of different types of railway tracks (i.e. balastless vs ballasted) is performed and the results are presented as a function of the total static track stiffness.

• 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.

• Structural Engineering and Mechanics
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• v.8 no.3
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• pp.243-256
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• 1999

Using appropriate transformations, the differential equation for flexural free vibration of a cantilever bar with variably distributed mass and stiffness is reduced to a Bessel's equation or an ordinary differential equation with constant coefficients by selecting suitable expressions, such as power functions and exponential functions, for the distributions of stiffness and mass. The general solutions for flexural free vibration of one-step bar with variable cross-section are derived and used to obtain the frequency equation of multi-step cantilever bars. The new exact approach is presented which combines the transfer matrix method and closed form solutions of one step bars. Two numerical examples demonstrate that the calculated natural frequencies and mode shapes of a 27-storey building and a television transmission tower are in good agreement with the corresponding experimental data. It is also shown through the numerical examples that the selected expressions are suitable for describing the distributions of stiffness and mass of typical tall buildings and high-rise structures.

• Journal of Power System Engineering
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• v.2 no.1
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• pp.59-66
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• 1998

The authors have studied vibration analysis algorithm which was suitable to the personal computer. Recently, we presented the transfer stiffness coefficient method(TSCM). This method is based on the concept of the transfer of the nodal dynamic stiffness coefficients which are related to force and displacement vectors at each node. In this paper, we describes the general formulation for the longitudinal and flexural coupled vibration analysis of a beam type structure by the TSCM. And the superiority of the TSCM to the finite element method(FEM) in the computation accuracy, cost and convenience was confirmed by results of the numerical computation and experiment.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.449-456
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• 2003

Hybrid semi-active control system is applied to improve the seismic peformance of the building structure against earthquake excitation and the LQR-based semi-active control algorithm is developed to tune the integrated stiffness/damping characteristics of the hybrid system complementarily. Numerical simulation for a 8-story shear building has been carried out to verify the applicability and effectiveness of the proposed method. Analysis results showed that the hybrid system can be a compromising solution to the seismic response control problem, compared with conventional variable stiffness or variable damping systems. Comparison results proved that the proposed algorithm can perform refined tuning of the stiffness and damping coefficients of the hybrid semi-active control system better than sliding mode control algorithm.

• Journal of the Korea Society for Simulation
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• v.8 no.3
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• pp.39-48
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• 1999

A finite element model of geared rotor system with flexible bearings were used to simulate the critical speeds and to investigate the effects of bearing coefficients on the dynamic behaviors of the systems. The finite element model includes the effects of tooth mesh stiffness, gyroscopic moment, rotary inertia, shear, and torque of the shaft. The gear mesh was modelled as a pair of rigid disks connected by a spring of time varying stiffness. The time varying mesh stiffness results in the abrupt change of the critical speeds of spur geared systems. As the bearing stiffness increases, critical speeds increase rapidly in case of stiff shafts, compared with flexible shafts.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.950-956
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• 2013

This paper describes a sensitivity-coefficient-based iterative method for detecting cracks in a structure. The sensitivity coefficients of a cracked structure are obtained by changing its eigenvectors. The proposed method is applied to a cracked cantilever. The crack is modeled as a rotational stiffness. The predicted cracks are in good agreement with those from a structural reanalysis of the cracked structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.762-769
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• 2017

The extensional stiffness in quasi-isotropic laminates is uniform in the radial direction, but the bending stiffness varies radially due to the stacking sequence. This paper addresses the directional dependency of the bending stiffness and its radial variation in three types of quasi-isotropic laminate reflectors consisting of unidirectional fiber composite materials (UDM) and randomly distributed composite materials (short fiber, RDM). The extensional stiffness and bending stiffness in optical reflectors using RDM are uniform, while the bending stiffness in those using UDM varies radially from 11% to 26%. Also, the stiffness sensitivity, such as the bend-twist or bend-torsion effect, due to the differences in the stiffness value in the composite, is large. These factors are problematic in the optical field requiring precision surfaces. Utilizing RDM might be one way to eliminate the presence of bending stiffness in composite mirror substrates.

• Ecology and Resilient Infrastructure
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• v.10 no.3
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• pp.51-63
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• 2023

Riverine tree management is crucial in realizing a balance between flood control and ecological preservation, which requires an accurate assessment of the impact of trees on river water elevations. In this study, eight different formulas for evaluating vegetation roughness considering the drag force acting on trees, were reviewed, and the characteristics and applicability of these methods were evaluated from a practical engineering perspective. The study compared the characteristics of vegetation roughness measurement methods for calculated roughness coefficients at different water depths and analyzed factors such as effects of tree canopy width, tree density and diameter, and tree stiffness coefficient, and water level estimation results. A comparison of roughness coefficients at the same water depths revealed that the Kouwen and Fathi-Moghadam formulas and the Fischenich formula yield excessive drag coefficients compared to other formulas. Factors such as channel geometry, tree diameter, and tree density showed varying trends depending on the formula but did not exhibit excessive outliers. Formulas considering the tree stiffness coefficient, such as the Freeman et al.'s formula and the Whittaker et al.'s formula, showed significant variations in drag coefficients depending on the stiffness coefficient. When applied to small- and medium-sized virtual rivers in South Korea using the drag coefficient results from the eight formulas, the results indicated a maximum increase in water level of approximately 0.2 to 0.4 meters. Based on this review, it was concluded that the Baptist et al., Huthoff et al., Cheng, Luhar, and Nepf's formulas, which exhibit similar characteristics and low input data uncertainties, are suitable for practical engineering applications.