• Coupled systems mechanics
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• v.7 no.4
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• pp.455-483
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• 2018

The study deals with physical modeling of a typical three storeyed building frame supported by a pile group of four piles ($2{\times}2$) embedded in cohesive soil mass using three dimensional finite element analysis. For the purpose of modeling, the elements such as beams, slabs and columns, of the superstructure frame; and that of the pile foundation such as pile and pile cap are descretized using twenty noded isoparametric continuum elements. The interface between the pile and the soil is idealized using sixteen node isoparametric surface element. The soil elements are modeled using eight nodes, nine nodes and twelve node continuum elements. The present study considers the linear elastic behaviour of the elements of superstructure and substructure (i.e., foundation). The soil is assumed to behave non-linear. The parametric study is carried out for studying the effect of soil- structure interaction on response of the frame on the premise of sub-structure approach. The frame is analyzed initially without considering the effect of the foundation (non-interaction analysis) and then, the pile foundation is evaluated independently to obtain the equivalent stiffness; and these values are used in the interaction analysis. The spacing between the piles in a group is varied to evaluate its effect on the interactive behaviour of frame in the context of two embedment depth ratios. The response of the frame included the horizontal displacement at the level of each storey, shear force in beams, axial force in columns along with the bending moments in beams and columns. The effect of the soil- structure interaction is observed to be significant for the configuration of the pile groups and in the context of non-linear behaviour of soil.

• Structural Engineering and Mechanics
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• v.69 no.3
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• pp.257-268
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• 2019

Infills are as important members in structural design as beams, columns and braces. They have significant effect on structural behavior. Because of lots of variables in infills like material non-linear behavior, the interaction between frames and infill, etc., the infills performance during an earthquake is complicated, so have led designers do not consider the effect of infills in designing the structure. However, the experimental studies revealed that the infills have the remarkable effect on structure behavior. As if these effects ignored, it might occur soft-story phenomena, torsion or short-column effects on the structures. One simple and appropriate method for considering the infills effects in analyzing, is replacing the infills with diagonal compression strut with the same performance of real infill, instead of designing the whole infill. Because of too many uncertainties, codes and researchers gave many expressions that were not as the same as the others. The major intent of this paper is calculation the width of this diagonal strut, which has the most characteristics of infill. This paper by comprehensive on different parameters like the modulus of young or moment of inertia of columns presents a new formula for achieving the equivalent strut width. In fact, this new formula is extracted from about 60 FEM analyses models. It can be said that this formula is very efficient and accurate in estimating the equivalent strut width, considering the large number of effective parameters relative to similar relationships provided by other researchers. In most cases, the results are so close to the values obtained by the FEM. In this formula, the effect of out of plane buckling is neglected and this formula is used just in steel structures. Also, the thickness of infill panel, and the lateral force applied to frame are constant. In addition, this new formula is just for modeling the lateral stiffness. Obtaining the nearest response in analyzing is important to the designers, so this new formula can help them to reach more accurate response among a lot of experimental equations proposed by researchers.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.2
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• pp.61-68
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• 2002

In order to design the Linear DC Motor (LDM) with improved characteristics, transient and steady state analysis are required. furthermore, 3D analysis is also needed to analyze the precise characteristics like thrust, time harmonics. This paper deals with the transient and dynamic characteristic analysis of LDM by coupling of external circuit and motion equation using 3D Equivalent Magnetic Circuit Network Method (EMCN). For the three dimensional analysis of electric machine, EMCN is very effective method that ensures high accuracy similar to FEM and short computation time. Also, The modeling by EMCN easily allows the mover to move with respect to the stater at each time step, and the spatial moving step is determined by the solution of the mechanical motion equation and the computed electromagnetic thrust The results are compared with experimental ones to clarify the usefulness and verify the accuracy of the Proposed method.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.372-380
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• 2000

Seismic forces for member design of bridges may be determined by modifying elastic member forces induced by design earthquakes using appropriate response modification factors according to national design code of bridges. Modeling of soil/foundation system is one of the critical parameter in the process of elastic seismic analysis of bridge system which greatly affects on the analysis results. In this paper, a simplified modelling procedure of soil/foundation system which gives practically reasonable results is presented and its applicability has been validated through example bridge. Based on the results, it has been shown that the procedure is acceptable in modelling soil/foundation system for practical seismic analysis of bridges.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.4
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• pp.395-403
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• 2002

The advanced space vector PWM is Implemented for the control system using high arithmetic performance microprocessor such as DSP. It is difficult to realize the complicate SLIM which is applied to SVPWM system, but widely used in vector control system or servo control system for AC motor because of its high performance in current control. In this paper, we use the dynamic characteristic analyzing method that can calculate efficiently the end effect by using equivalent circuit methode in the operating SLIM system modeling and examine the dynamic characteristics of SVPWM with PI controller.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.6
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• pp.794-805
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• 1999

Pneumatic cushioning cylinders are commonly employed for vibration and shock control. A mathematical simulation model of a double acting pneumatic cushioning cylinder designed to absorb shock loads is presented which is based on the following assumptions; ideal equation of state isentropic flow through a port conservation of mass polytropic thermodynamics single degree of freedom piston dynamics and energy equivalent linear damping. These differential equation can be solved through numerical integration using the fourth order Runge-Kutta method. An experimental study was conducted to validate the results obtained by the numerical integra-tion technique. Simulated results show good agreement with experimental data. The computer simulation model presented here has been extremely useful not only in understanding the has been extremely useful not only in understanding the basic cushioning but also in evaluating different designs.

• Structural Engineering and Mechanics
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• v.22 no.5
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• pp.575-597
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• 2006

Enhanced three-dimensional finite elements for geometrically nonlinear analysis of cable-supported structures are presented. The cable element, derived by using the concept of an equivalent modulus of elasticity and assuming the deflection curve of a cable as catenary function, is proposed to model the cables. The stability functions for a frame member are modified to obtain a numerically stable solution. Various numerical examples are solved to illustrate the versatility and efficiency of the proposed finite element model. It is shown that the finite elements proposed in this study can be very useful for geometrically nonlinear analysis as well as free vibration analysis of three-dimensional cable-supported structures.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.967-969
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• 2003

It is difficult to realize the complicate SUM which is applied vector control system, but widely used in AC motor vector motor control system or servo control system because of its high performance in current control. In this paper, we use the dynamic characteristic analyzing methode that can calculate efficiently the end effect by using equivalent circuit methode in the operating SLIM system modeling and doing simulation of output characteristics of vector controller.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.1-8
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• 2001

Seismic design forces for bridge components may be determined by modifying elastic member forces of design earthquakes using appropriate response modification factors according to the national design code of bridges Modeling technique of pile foundation system is one of the important parameters which greatly affects the results in the process of the elastic seismic analysis of a bridge system with pile foundation. In this paper, a approximate and simplified modeling technique of a pile foundation system for the practical purposes is presented. The modeling technique is based on the stiffnesses of pile foundation during earthquake. The horizontal stiffnesses are determined from the resistance-deflection curves derived from the results of dynamic field tests using cyclic loads and the vertical stiffness includes the effects of the end bearing capacities and side friction of piles as well as the pile compliances under the expected vertical load level. The applicability of the proposed technique has been validated through the some example bridge analyses.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.469-476
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• 2023

Soil plasticity models for cyclic and dynamic loads are essential in non-linear numerical analysis of geotechnical structures. While a single yield surface model shows a linear behavior for cyclic loads, J₂-bounding surface plasticity model with zero elastic region can effectively simulate a nonlinearity of the ground response with the same material properties. The radius of the yield surface inside the boundary surface converged to 0 to make the elastic region disappear, and plastic hardening modulus and dilatancy define plastic strain increment. This paper presents the stress-strain incremental equation of the developed model, and derives plastic hardening modulus for the hyperbolic model. The comparative analyses of the triaxial compression test and the shallow foundation under the cyclic load can show stable numerical convergence, consistency with the theoretical solution, and hysteresis behavior. In addition, plastic hardening modulus for the modified hyperbolic function is presented, and a methodology to estimate model variables conforming 1D equivalent linear model is proposed for numerical modeling of the multi-dimensional behavior of the ground.