• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.230-237
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• 2000

The purpose of this study is to evaluate the dynamic behavior of highway bridge due to moving vehicle load, considering the effect of laminated rubber bearing. Dynamic behaviors of bridge considering the effect of bearings are studied with 3-dimensional bridge and vehicle models. To analyze the effect of bearings on the dynamic behaviors of superstructures of bridges, laminated rubber bearing is modeled as 3-dimensional frame element with equivalent stiffness and damping, and the models are included in the bridge analysis model. The results from the analytical models with laminated rubber bearing show a significant effects on dynamic responses and more complex vibration characteristics compared with the results from the bridge with pot bearings. Generally, larger dynamic amplification factors are obtained in the case of laminated rubber bearing, which is mainly due to the smaller torsional stiffness of the bridge with laminated rubber bearing. It can be recommended that were careful consideration on the vibration of bridges and dynamic load allowance in design are needed when adopting laminated rubber bearing.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1630-1638
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• 2001

Partial rotor rub occurs when an obstacle on the stator of a rotating machinery disturbs the free whirling motion of the rotor, which is more common than full annular rub among the cases of rubbing in rotating machinery. The intermittent contacts and friction during partial rotor rub makes the phenomenon complex. The several nonlinear phenomena of superharmonics, subharmonics, and jump phenomenon are demonstrated for the partial rub using an experimental apparatus in this study. The orbit patterns are also measured experimentally. In order to explain the phenomena of partial rotor rub, the analytical model for the contact between the rotor and stator should be chosen carefully. In this respect, a piecewise-linear model and a rebound model using the coefficient of restitution are investigated on the basis of the experimental observations. Also, Numerical simulations for the two models of contact are done for the various system parameters of clearance, contact stiffness, and friction coefficient. The results show that the piecewise-linear model for partial rotor rub is more plausible to explain the experimental observgations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.277-282
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• 2001

Partial rotor rub occurs when an obstacle on the stator of a rotating machinery disturbs the free whirling motion of a rotor, which is more common than full annular rub for the cases of rubbing in rotating machinery. The nonlinearity due to the intermittent contacts and friction during partial rotor rub makes the phenomenon complex. The several nonlinear phenomena of superharmonics, subharmonics, and jump phenomenon are demonstrated for the partial rub using an experimental apparatus in this study. A piecewise-linear model and a rebound model using the coefficient of restitution are investigated on the basis of experimental observations in order to adopt as an analytical model of the contact between the rotor and stator during whirling motion. The contact stiffness, coefficient of restitution, and friction coefficient for the contact during partial rub are calculated from the comparison between the numerical simulation and the experimental results. Also, the numerical simulations for the model of partial rub are done for the various system parameters of clearance, contact stiffness, and friction coefficient in order to find the nonlinear behavior of partial rotor rub.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.169-175
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• 1997

Recently it is increased by degrees to produce complex and large lattice structures such as bridge, tower, crane, and space structures. In general, in order to analyse these structures we have used finite element method(FEM). In this method, however, it is necessary to use a large amount of computer memory and to take long computation time. For overcoming this problem, the Authors have developed the transfer dynamic stiffness coefficient method(TDSCM) which consists on the concept of the substructure synthesis method and transfer influence coefficient method. In this paper, the new free vibration analysis method for large type lattice structure is formulated by the TDSCM. And the results obtained by TDSCM are compared with those obtained by FEM, transfer matrix method and experiment. And it is confirmed for TDSCM to be the numerical high accuracy and high speed structure analysis method.

• Nuclear Engineering and Technology
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• v.30 no.5
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• pp.387-395
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• 1998

In general, the laminated rubber bearing (LRB), a composite structure laminated with the elastic rubber and steel plates, has a complex hysteretic nonlinear characteristics in relationships between the restoring force and shear deflection. The representative nonlinear characteristics of LRB include the change of hysteresis loop with cyclic shear deflections and the hardening effects at large shear deflection regions. Changes of the hysteresis loop of LRB with cyclic shear deflections affect the horizontal stiffness and the damping characteristics. The hardening behavior of LRB in large shear deflection region results in an increased horizontal stiffness and therefore, has a great impacton the seismic responses. In this paper, the seismic response analysis is carried out using the modified hysteretic bi-linear model of LRB, which takes into account the hysteresis loop change and the hardening behavior with cyclic shear deflection. The results on seismic responses are compared with those obtained using the widely used hysteretic hi-linear model. The new model is found to reveal the greater amount of peak acceleration response.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2236-2241
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• 2008

To predict the dynamic behaviour of railway vehicle, the complex vehicle structure has been described by mathmatical model such as mass, spring and damper. Air-spring has played a major role to improve dynamic characteristics, vibration isolation and ride comfort. The mechanical behaviour of air spring is very complicated. The behaviour is based on fluid and thermodynamic mechanisms. The main parameters of air spring are stiffness due to compression of the air in the spring and surge reservoir, change of area stiffness and orifice damping. In this paper, we have studied an air-spring modeling method and compared the difference between calculation and test.

• Structural Engineering and Mechanics
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• v.8 no.1
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• pp.1-18
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• 1999

Procedures are investigated by which nonlinear finite element shell analysis algorithms can be simplified to provide more cost effective approximate analyses of orthogonally-reinforced concrete flat plate structures. Two alternative effective stiffness formulations, and an unbalanced force formulation, are described. These are then implemented into a nonlinear shell analysis algorithm. Nonlinear geometry, three-dimensional layered stress analyses, and other general formulations are bypassed to reduce the computational burden. In application to standard patch test problems, these simplified approximate analysis procedures are shown to provide reasonable accuracy while significantly reducing the computational effort. Corroboration studies using various simple and complex test specimens provide an indication of the relative accuracy of the constitutive models utilized. The studies also point to the limitations of the approximate formulations, and identify situations where one should revert back to full nonlinear shell analyses.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.386-391
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• 2001

In this paper, the vibration characteristics of IHTS(Intermediate Heat Transfer System) piping system of LMR(Liquid Metal Reactor) conveying hot liquid sodium are investigated to eliminate the pipe supports for economic reasons. To do this, a 3-dimensional straight pipe element and a curved pipe element conveying fluid are formulated using the dynamic stiffness method of the wave approach and coded to be applied to any complex piping system. Using this method, the dynamic characteristics including the natural frequency, the frequency response functions, and the dynamic instability due to the pipe internal flow velocity are analyzed. As one of the design parameters, the vibration energy flow is also analyzed to investigate the disturbance transmission paths for the resonant excitation and the non-resonant excitations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.575-580
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• 2000

Recently it is increased by degrees to construct complex and large lattice structure such as bridge, tower and crane structures. It is very important problem to know dynamic properties of such structures. Authors presented new dynamic response analysis algorithm for rectilinear structure already. This analysis algorithm is combined transfer stiffness coefficient method with Newmark method. Presented method improves the computational accuracy remarkably owing to advantage of the transfer stiffness coefficient method. This paper formulates dynamic response analysis algorithm for plane lattice structure expanding rectilinear structures.

• Coupled systems mechanics
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• v.4 no.2
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• pp.191-209
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• 2015

Hybrid girders can be constructed in different geometrical forms and from different materials. Selection of beam's effective constellation represents a complex process considering the variations of geometrical parameters, changes of built in material characteristics and their mutual relations, which has important effect on the behavior of the girder. This paper presents the theoretical and experimental research on behavior of the timber-steel hybrid girders' different geometrical constellation with external prestressing and in different conditions of timber moisture. These researches are based on linear elastic analysis, and further refine by using the plasticity and damage models.