• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.10a
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• pp.217-224
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• 1997

Static characteristics of hemispherical aerodynamic bearing is studied theoretically. In this paper nonlinear equation of second order considering compressibility and slip effect of air is calculated by Newton-Raphson method. Results indicate that axial load capacity has maximum value when the inclination angle of groove is about 30$\circ$, the ratio of groove clearance to ridge clearance is two. We also present the design method of hemispherical Aerodynamic bearing based on it's load capacity taking into account manufacturing and assembling viewpoint.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.33 no.1
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• pp.1-8
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• 1984

The system of synchronous generator with power static converter are analyzed in detail and the output characteristics of generator are computed by digital simulation. The power static converter is considered as 3-phase converter in which the interlude interval and the commutation interval repeats itself six times per cycle. The synchronous generator is considered as a direct-phase quantities model for a more exact study of the performance. As the numerical method for nonlinear differential equations of the system, the Runge -Kutta method is used.

• Computers and Concrete
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• v.13 no.1
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• pp.1-16
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• 2014

To evaluate the behavior of the advanced unbonded pre-stressed concrete containment vessel (UPCCV) for one typical China nuclear power plant under Japan's March 11 earthquake, five nonlinear time history analysis and a nonlinear static analysis of a 1:10 scale UPCCV structure have been carried out with MSC.MARC finite element program. Comparisons between the analytical and experimental results demonstrated that the developed finite element model can predict the earthquake behavior of the UPCCV with fair accuracy. The responses of the 1:10 scale UPCCV subjected to the 11 March 2011 Japan earthquakes recorded at the MYG003 station with the peak ground acceleration (PGA) of 781 gal and at the MYG013 station with the PGA of 982 gal were predicted by the dynamic analysis. Finally, a static analysis was performed to seek the ultimate load carrying capacity for the 1:10 scale UPCCV.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.5
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• pp.229-238
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• 2015

For small-size reinforce-concrete buildings, Midas Gen, OpenSees, and Perform-3D, which are structural analysis programs that are most popularly used at present, were applied for nonlinear static pushover analysis, and then difference between those programs was analyzed. Example buildings were limited to 2-story frames with irregular shaped walls. Analysis result showed that there were more differences than for frames only and frames with rectangular walls, but it was not so significant. Nevertheless, the capacity curve were different in some buildings, which is attributed to shape and location of walls, and feature of the analysis program. Especially, selection of automatic or manual input in Midas Gen, or nonlinear wall elements in Perform3D can affect the capacity curve and performance of the buildings. Therefore, the program users should understand the feature of the program well, and then conduct performance assessment. The result of this study is limited to low-story buildings so that it should be noted that it is possible to get different results for mid- to high-rise buildings.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.3 s.22
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• pp.29-35
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• 2006

Fiber element method in earthquake response analysis of bridges is used to represents a realistic flexural deformation according to nonlinear behavior of beam-column section. Nonlinear pseudo-static analysis of two column bent using fiber element is accomplished and failure mechanism of the plastic hinge region is studied. Load-displacement curve obtained by nonlinear pseudo-static analysis can be applicable to earthquake response analysis by capacity spectrum method. The nonlinear time history analysis of a full bridge model using fiber element experienced by the ground motion corresponding to the target response spectrum is accomplished. The result of time history analysis is similar to that of capacity spectrum method.

• Structural Engineering and Mechanics
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• v.54 no.3
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• pp.433-451
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• 2015

This paper focuses on large deflection static behavior of edge cracked simple supported beams subjected to a non-follower transversal point load at the midpoint of the beam by using the total Lagrangian Timoshenko beam element approximation. The cross section of the beam is circular. The cracked beam is modeled as an assembly of two sub-beams connected through a massless elastic rotational spring. It is known that large deflection problems are geometrically nonlinear problems. The considered highly nonlinear problem is solved considering full geometric non-linearity by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. There is no restriction on the magnitudes of deflections and rotations in contradistinction to von-Karman strain displacement relations of the beam. The beams considered in numerical examples are made of Aluminum. In the study, the effects of the location of crack and the depth of the crack on the non-linear static response of the beam are investigated in detail. The relationships between deflections, end rotational angles, end constraint forces, deflection configuration, Cauchy stresses of the edge-cracked beams and load rising are illustrated in detail in nonlinear case. Also, the difference between the geometrically linear and nonlinear analysis of edge-cracked beam is investigated in detail.

• Steel and Composite Structures
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• v.28 no.2
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• pp.209-221
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• 2018

An empirical and efficient method is presented for calculating the dynamic increase factor to amplify the applied loads on the affected bays of a steel frame structure with semi-rigid connections. The nonlinear static alternate path analysis is used to evaluate the dynamic responses. First, the polynomial models of the extended end plate and the top and seat connection are modified, and the proposed polynomial model of the flush end plate connection shows good agreement as compared with experimental results. Next, a beam model with nonlinear spring elements and plastic hinges is utilized to incorporate the combined effect of connection flexibility and material nonlinearity. A new step-by-step analysis procedure is established to obtain quickly the dynamic increase factor based on a combination of the pushdown analysis and nonlinear dynamic analysis. Finally, the modified dynamic increase factor equation, defined as a function of the maximum ratio value of energy demand to energy capacity of an affected beam, is derived by curve fitting data points generated by the different analysis cases with different column removal scenarios and five types of semi-rigid connections.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.6
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• pp.496-501
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• 2007

In order to enhance sintering characteristics on the $ZnO-Pr_6O_{11}$ based multilayer chip varistors (MLVs), a response surface analysis using central composite design method were carried out. As a result, varistor voltage($V_{1mA}$), nonlinear coefficient ($\alpha$), leakage current ($I_L$) and capacitance (C) were considered to be mainly affected by sintered temperature and holding time. MLVs sintered at $1200^{\circ}C$ and above $1200^{\circ}C$ revealed poor electrical characteristics, possibly due to the reaction between electrode materials(Pd) and $ZnO-Pr_6O_{11}$ based ceramics. On the sintering temperature range $1150{\sim}1175^{\circ}C$, nonlinear coefficient ($\alpha$) and leakage current ($I_L$) were shown to be $60{\sim}69$ and below $0.3{\mu}A$, respectively. In particular, MLVs sintered at $1175^{\circ}C$, 1.5 hr and $2^{\circ}C/hr$ (cooling speed) showed stable ESD(Electrical Static Discharge) characteristics under the condition of 10 times at 8 Kv with deviation varistor voltage, and deviation nonlinear coefficient were 0.3% and 0.33% (at positive), 0.55% (at negative), respectively.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.1
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• pp.9-18
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• 2019

In 2017 Pohang Earthquake, a number of residential buildings with pilotis at their first level were severely damaged. In this study, the results of an analytical investigation on the seismic performance and structural damage of two bearing wall buildings with pilotis are presented. The vibration mode and lateral force-resisting mechanism of the buildings with vertical and plan irregularity were investigated through elastic analysis. Then, based on the investigations, methods of nonlinear modeling for walls and columns at the piloti level were proposed. By performing nonlinear static and dynamic analyses, structural damages of the walls and columns at the piloti level under 2017 Pohang Earthquake were predicted. The results show that the area and arrangement of walls in the piloti level significantly affected the seismic safety of the buildings. Initially, the lateral resistance of the piloti story was dominated mainly by the walls resisting in-plane shear. After shear cracking and yielding of the walls, the columns showing double-curvature flexural behavior contributed significantly to the residual strength and ductility.

• Steel and Composite Structures
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• v.52 no.5
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• pp.501-513
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• 2024

Two-directional functionally graded materials (2D-FGMs) show extraordinary physical properties which makes them ideal candidates for designing smart micro-switches. Pull-in instability is one of the most critical challenges in the design of electrostatically-actuated microswitches. The present research aims to bridge the gap in the static pull-in instability analysis of microswitches composed of 2D-FGM. Euler-Bernoulli beam theory with geometrical nonlinearity effect (i.e. von-Karman nonlinearity) in conjunction with the modified couple stress theory (MCST) are employed for mathematical formulation. The micro-switch is subjected to electrostatic actuation with fringing field effect and Casimir force. Hamilton's principle is utilized to derive the governing equations of the system and corresponding boundary conditions. Due to the extreme nonlinear coupling of the governing equations and boundary conditions as well as the existence of terms with variable coefficients, it was difficult to solve the obtained equations analytically. Therefore, differential quadrature method (DQM) is hired to discretize the obtained nonlinear coupled equations and non-classical boundary conditions. The result is a system of nonlinear coupled algebraic equations, which are solved via Newton-Raphson method. A parametric study is then implemented for clamped-clamped and cantilever switches to explore the static pull-in response of the system. The influences of the FG indexes in two directions, length scale parameter, and initial gap are discussed in detail.