• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.6
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• pp.463-469
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• 2004

In order to improve the instability of journal bearings, the leaf spring dampers (LSD) are introduced. The effects of LSD on the stability of journal bearings are investigated theoretically The stability of the journal bearing with LSD are compared with the results of the journal bearing without LSD. And the effects of the asymmetry of the stiffness of the leaf spring damper on the stability of rotors are also investigated.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.3
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• pp.37-44
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• 1997

In this paper, the inelastic behavior of an asymmetric tall building is investigated. The asymmetry in rigidity caused by the structural asymmetry induces torsional as well as lateral deformation. The inelastic analysis of such an asymmetric structure is difficult to carry out with a planar model and thus requires a full three dimensional model. In this paper a 102 story unsymmetric tall building is analized by static push-over procedure and its behavior is investigated. The analysis are performed with and without floor rotation to compare the results. According to the results the static behavior of the model building, as expected, turned out to be dependent heavily an the asymmetry of the plan shapes of the building.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.1
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• pp.43-53
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• 2002

Current torsional provisions focus n restricting torsional effect of asymmetric wall structures by proportioning strength of wall based on the traditional assumption that stiffness and strength are independent. Recent studies have pointed out that stiffness of structural wall is dependent on the strength. This implies that actual stiffness of walls can be determined only after torsional design is finished and current torsional provisions may result in significant errors. To overcome this shortcoming, this paper proposes deformation based torsional design for asymmetric wall structures. Contrary to the current torsional provisions, deformation-based torsional design uses displacement and rotation angle as design parameters and calculates base shear for inelastic torsional response directly. Main purpose of deformation based torsional design is not to restrict torsional response but to ensure intended torsional mechanism according to the capacity design concept. Because displacement and rotation angle can be used as performance criteria indicating performance level of asymmetric structures, this method can be applied to the performance based seismic design effectively.

• Journal of Korean Society of Steel Construction
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• v.26 no.3
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• pp.177-189
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• 2014

When floor vibration problems occur in existing buildings, TMD (tuned mass damper) can be a viable alternative to resolving the problem. Only when TMD has been exactly tuned to the natural frequency of the floor, it can control the vibration as intended in design. However, TMD gets inefficient in the situation where the natural frequency changes as a result of the uncontrollable variation of the floor mass weight. This physical phenomenon is often called as TMD-off-tuning. This study proposes asymmetric TMD for enhancing the robustness of floor vibration control against uncertain natural frequencies. The proposed TMD features two asymmetric linear springs such that the floor vibrational energy can be dissipated through both the translational and rotational motion. An easy-to-use graphical optimization method was developed in this study. The asymmetric TMD proposed outperformed in vibration control by 28% compared to that of conventional TMD. The robustness of asymmetric TMD of this study was two times higher than that of conventional TMD.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.941-944
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• 2005

Asymmetry of rotor systems is an important factor for identification of dynamic characteristics including the stability and response of rotors and for condition monitoring. In this work, asymmetry of rotors is identified by applying curve-fitting method to the directional frequency response functions (dFRFs), which are known as a powerful tool for detecting the presence and degree of asymmetry. This method minimizes least square error between analytical and measured dFRFs by iteratively updating physical parameters associated with rotor asymmetry. The effectiveness of the identification method is demonstrated by experiments with a laboratory test rotor.

• Composites Research
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• v.14 no.4
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• pp.1-7
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• 2001

This paper presents the results of an analytical investigation pertaining to the elastic local buckling behavior of asymmetric edge stiffened orthotropic open section structural member under uniform compression. The asymmetric edge stiffener is considered as a beam element neglecting its torsional rigidity. We suggested the analytical model of asymmetric edge stiffeners which is composed of a strip of flange plate, equal width of edge stiffener, and a plate attached at the flange end, and computed the moment of inertia of the stiffener about an axis through the centroid of the ensuing cross-section. Using the derived equation, the local buckling coefficients of asymmetrically edge stiffened orhtotropic I-section columns are predicted and the results are presented in a graphical form.

• Journal of Korean Society of Steel Construction
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• v.28 no.1
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• pp.43-52
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• 2016

A numerical study on required stiffness of the longitudinal stiffener in the webs stiffened with flat plate at one-side of the web was conducted. The longitudinal stiffeners are commonly placed around 0.2D, i.e., 1/5 the web depth due to fabrication convenience although most plate girders for bridges are unsymmetric section. Considering asymmetry of section, aspect ratio of web and the rigidity ratio of longitudinal stiffener(${\gamma}^*$), eigenvalue analysis were performed to evaluate the buckling strength for the webs with a stiffener located at 0.16D~0.24D. Based on the parametric analysis, the required stiffness of the longitudinal stiffener to satisfy the buckling strength specified in AASHTO LRFD specifications was presented.

• Composites Research
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• v.13 no.5
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• pp.18-30
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• 2000

In order to optimize the design of unidirectional fiber reinforced composite C-rings, a viscoelastic load relaxation behavior was analyzed under a point load. Initially, the deflection and bending stiffness were calculated based on the elastic beam theory and the viscoelastic relaxation and creep behaviors were derived from the elastic solution using the correspondence theorem. Besides the orthotropic mechanical properties of the composite, asymmetric mechanical property due to the different tensile and compressive properties were also considered. Except the deviation affected by the relatively large thickness of the specimen compared to the radius, the calculated relaxation showed good agreement with the experimental result.

• Journal of Aerospace System Engineering
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• v.12 no.6
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• pp.41-49
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• 2018

In this study, the theoretical dynamic characteristics of a thin-walled composite beam with a single-cell of chordwise asymmetric cross-section was studied. Mathematical modeling was done by considering the transverse shear effects, the warping restraint effects, the constant taper ratio in the longitudinal direction of the beam, and the geometrical cross-section ratio. The mass coefficients, stiffness coefficients, and Eigen frequencies of the selected section were investigated. In particular, the effects of the taper ratio and cross-section ratio of the model on the Eigen frequencies were analyzed and compared when the asymmetry of the section was considered and the warping function was not corrected.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.681-686
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• 2004

Identification of asymmetry and anisotropy of rotor system is important for diagnosis of rotating machinery. Directional frequency response functions (dFRFs) are known to be powerful tool in effectively detecting the presence of asymmetry or anisotropy. In this paper, an estimation method of dFRFs for rotors is newly developed, when both asymmetry and anisotropy are present. The method transforms the finite degrees-of-freedom time-varying linear differential equation of motion to an infinite degree-of-freedom time-invariant linear one, employing the modulated coordinates. The validity of the method is demonstrated by numerical simulation with a simple rotor model.