• Steel and Composite Structures
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• v.26 no.2
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• pp.151-161
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• 2018

The application of carbon fiber reinforced polymer (CFRP) composites for rehabilitation of steel structures has become vital in recent years. This paper presents an experimental program and a finite element (FE) modelling approach to study the effectiveness of CFRP patch for repair of notch damaged circular hollow sectional (CHS) steel beams. The proposed modeling approach is unique because it takes into account the orthotropic behavior and stacking sequence of composite materials. Parametric study was conducted to investigate the effect of initial damage (i.e., notch depth) on flexural performance of the notched beams and effectiveness of the repair system using the validated FE models. Results demonstrated the ability of CFRP patch to repair notched CHS steel beams, restoring them to their original flexural stiffness and strength. The effect of composite patch repair technique on post-elastic stiffness was more pronounced compared to the elastic stiffness. Composite patch repair becomes more effective when the level of initial damage of beam increases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.1889-1900
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• 1995

In this study, a large deflection analysis of a plane frame composed of a thin-walled tube in investigated. When bent, a thin-walled tube is usually controlled by local buckling and subsequent bending collapse of the section. So load resistance reaches the yield level in a thin-walled rectangular tube. This relationship can be divided into three regimes : elastic, post-buckling and crippling. In this paper, this relationship is theoretically presented to be capable of describing nonlinearities and a stiffness matrix is derived by introducing a compound beam-spring element. A numerical analysis uses a constant incremental energy method and the solution is obtained by modifying stiffness matrix at elastic/inelastic stage. This analytical results, load-deflection paths show a good agreement with the test results.

• Structural Engineering and Mechanics
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• v.62 no.4
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• pp.431-441
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• 2017

In this article, an analytical-numerical approach is presented in order to determine the dynamic response of thin plates resting on multiple elastic point supports with time-varying stiffness. The proposed method is essentially based on transforming a familiar governing partial differential equation into a new solvable system of linear ordinary differential equations. When dealing with time-invariant stiffness, the solution of this system of equations leads to a symmetric matrix, whose eigenvalues determine the natural frequencies of the point-supported plate. Moreover, this method proves to be applicable for any plate configuration with any type of boundary condition. The results, where possible, are verified upon comparison with available values in the literature, and excellent agreement is achieved.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.103-109
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• 2007

With the increase of track density, high rotational speed and the compatibility for various media in optical disk drives, the effective design to vibration reduction is very important for robust operation. Especially when a slim optical disk drive for a notebook PC is excited by a mass-unbalanced disk, internal vibration and its transmission to external case bring about severer problem than that of conventional one. In this paper a design process of a rubber mount in a slim optical disk drive for vibration reduction is presented. The characteristics of rubbery materials - hyper-elastic and visco-elastic - are measured with standard specimens. The static stiffness of a rubber mount was calculated by FEM and the dynamic stiffness is predicted with the static stiffness and the impedance test data of the standard specimen. The transmissibility tests are performed for the purpose of verification of the design process.

• Tribology and Lubricants
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• v.5 no.1
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• pp.64-68
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• 1989

The dynamic characteristics of the annular pressure seal employed in pump have been theoretically deduced with consideration of the effects of elastic deformation due to the centrifugal stress. The deformation of the shaft is governed by the linear theory of elasticity. The results derived herein considering the elastic deformation are compared with the previously published author's results in the stiffness and damping coefficients.

• Earthquakes and Structures
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• v.12 no.4
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• pp.437-448
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• 2017

Soft or extreme soft storeys in multi-storied buildings cause localized damage (and even collapse) during strong earthquake shaking. The presence of such soft or extremely soft storey is identified through provisions of vertical stiffness irregularity in seismic design codes. Identification of the irregularity in a building requires estimation of lateral translational stiffness of each storey. Estimation of lateral translational stiffness can be an arduous task. A simple procedure is presented to estimate storey stiffness using only properties of fundamental lateral translational mode of oscillation (namely natural period and associated mode shape), which are readily available to designers at the end of analysis stage. In addition, simplified analytical expressions are provided towards identifying stiffness irregularity. Results of linear elastic time-history analyses indicate that the proposed procedure captures the irregularity in storey stiffness in both low- and mid-rise buildings.

• Earthquakes and Structures
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• v.1 no.1
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• pp.21-41
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• 2010

Multi-span steel-concrete composite (SCC) bridges are very sensitive to earthquake loading. Extensive damage may occur not only in the substructures (piers), which are expected to yield, but also in the other components (e.g., deck, abutments) involved in carrying the seismic loads. Current seismic codes allow the design of regular bridges by means of linear elastic analysis based on inelastic design spectra. In bridges with superstructure transverse motion restrained at the abutments, a dual load path behavior is observed. The sequential yielding of the piers can lead to a substantial change in the stiffness distribution. Thus, force distributions and displacement demand can significantly differ from linear elastic analysis predictions. The objectives of this study are assessing the influence of piers-deck stiffness ratio and of soil-structure interaction effects on the seismic behavior of continuous SCC bridges with dual load path, and evaluating the suitability of linear elastic analysis in predicting the actual seismic behavior of these bridges. Parametric analysis results are presented and discussed for a common bridge typology. The response dependence on the parameters is studied by nonlinear multi-record incremental dynamic analysis (IDA). Comparisons are made with linear time history analysis results. The results presented suggest that simplified linear elastic analysis based on inelastic design spectra could produce very inaccurate estimates of the structural behavior of SCC bridges with dual load path.

• The KSFM Journal of Fluid Machinery
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• v.16 no.3
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• pp.5-9
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• 2013

In this study, operational vibration experiment and analysis have been conducted for the 4-blade small vertical-axis wind turbine (VAWT) including the effect of tower elastic behavior. Computational structural dynamics analysis method is applied to obtain Campbell diagram for the VAWT with elastic tower. An open type wind-tunnel is used to change and keep the wind velocity during the ground test. Equivalent elastic tower is used to support the VAWT so that the effect of elastic stiffness of the tower can be considered in the present vibration experiment. Various excitation conditions with wind loads are considered and the dominant operating vibration phenomena are physically investigated in detail.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3185-3194
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• 1994

In this study, an impact model and impact response analysis method was suggested for the impacts between arbitrary shaped bodies. Unlike the impacts between geometrically simple structures, there is no rules to analyze the impacts between general elastic structures First of all, it has been attempted to explain the impoot between arbitrary elastic structures as the elastic deformation of a virtual contact spring in the vicinity of contact points. The contact stiffness and the exponent are determined from the Hertz's contact theory and F. E. analysis. In order to evaluate the validities and limitations of the proposed methods, an impact tester and the miniature of container, missile and isolators have been provided and tested experimentally. All the experiments were performed with various impact conditions. The results obtained by the proposed methods were directly compared with the measured values in terms of maximum contract force, contact duration, the shape of contact force and the structure responses. The computed contact force and responses, using this proposed methods, were very close to the measured results, unless any plastic deformations were presented.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1744-1748
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• 2007

In this study, the Johnson-Kendall-Roberts (JKR) theory was combined with the instrumented indentation technique (IIT) to evaluate work of adhesion and modulus of elastomeric polymer. Indentation test was used to obtain the load-displacement data for contacts between Tungsten Carbide indenter and elastomeric polymer. And the JKR contact model, contrived to take viscoelastic effects of polymer into account, was applied to compensate the contact area and the elastic modulus which Hertzian contact model would underestimate and overestimate, respectively. Besides, we could obtain the thermodynamic work of adhesion by considering the surface energy in this contact model. In order to define the relation between JKR contact area and applied load without optical measuring of contact area, we used the relation between applied load and contact stiffness by examining the correlation between JKR contact area and stiffness through dimensional analysis with 14 kinds of elastomeric polymer. From this work, it could be demonstrated that the interfacial work of adhesion and elastic modulus of compliant polymer can be obtained from a simple instrumented indentation testing without area measurement, and provided as the main algorithm of compliant polymer characterization.