• Magazine of the Korean Society of Agricultural Engineers
• /
• v.42 no.6
• /
• pp.122-129
• /
• 2000

The purpose of this study is to investigate both the fundamental and some higher natural frequencies and mode shapes of compressive members resting on the linear elastic foundation. The model of compressive member is based on the classical Bernoulli-Euler beam theory. The differential equation governing free vibrations of such members subjected to an axial load is derived and solved numerically for calculating the natural frequencies and mode shapes. The Improved Euler method is used to integrate the differential equation and the Determinant Search method combined with the Regula-Falsi method to determine the natural frequencies, respectively. In numerical examples, the hinged-hinged, hinged-clamped, clamped-hinged and clamped-clamped end constraints are considered. The convergence analysis is conducted for determining the available step size in the Improved Euler method. The validation of theories developed herein is also conducted by comparing the numerical results between this study and SAP 90. The non-dimensional frequency parameters are presented as the non-dimensional system parameters: section ratio, modulus parameter and load parameter. Also typical mode shapes are presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.25 no.1
• /
• pp.13-23
• /
• 2015

The paper experimentally deals with the radial in-plane vibration characteristics of disk-shaped piezoelectric transducers. The radial in-plane motion, which is induced due to Poisson's ratio in the piezoelectric disk polarized in the thickness direction, was measured by using an in-plane laser vibrometer, and the natural frequencies were measured by using an impedance analyzer. The experimental results have been compared with theoretical predictions obtained by simplified theoretical and finite-element analyses. It appears that the fundamental mode of a piezoelectric disk transducer is a radial mode and its radial displacement distribution from the center to the perimeter is not monotonic but shows maximum slightly apart from the perimeter. The theoretically-calculated fundamental frequencies agree well with the finite-element results for small thickness-to-diameter ratio, and they are accurate within 7 % error for the ratio up to 0.4.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.12
• /
• pp.970-978
• /
• 2002

The differential equations governing free vibrations of the elastic arches with unsymmetric axis are derived in Cartesian coordinates rather than in polar coordinates. in which the effect of rotatory inertia is included. Frequencies and mode shapes are computed numerically for parabolic arches with both clamped ends and both hinged ends. Comparisons of natural frequencies between this study and SAP 2000 are made to validate theories and numerical methods developed herein. The convergent efficiency is highly improved under the newly derived differential equations in Cartesian coordinates. The lowest four natural frequency parameters are reported, with and without the rotatory inertia, as functions of three non-dimensional system parameters the rise to chord length ratio. the span length to chord length ratio, and the slenderness ratio. Also typical mode shapes of vibrating arches are presented.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.45-48
• /
• 2008

This study is for proposing the shape of hollow and evaluating the structural performance of hollow reinforced concrete (RC) half slabs. The two-phase experimental works were carried out, and styrofoam was used for reduction of dead load and vibration. From the Phase I test result, the shape and spacing of the hollow were determined to obtain the high deduction ratio of the concrete and the desirable failure mode of the hollow RC half slabs. In the Phase II test, two slab specimens were tested in flexure to evaluate the flexural capacity of the hollow RC half slabs with the proposed hollow shape. In the result of the test, all the specimens having the proposed hollow shape showed sufficient flexural capacity.

• Journal of the Optical Society of Korea
• /
• v.14 no.2
• /
• pp.137-141
• /
• 2010

We report, for the first time to our knowledge, observation of polarization bistability from 1.55-${\mu}m$ wavelength single-mode VCSELs of a conventional cylinder-shape under control of their driving current, and demonstration of all-optical flip-flop (AOFF) operations based on the bistability with optical set and reset pulse injection at a 50 MHz switching frequency. The injection pulse energy was less than 14 fJ. The average on-off contrast ratio of the flip-flopped signals was about 7 dB. These properties of the VCSELs will be potentially useful for future high-speed all-optical signal processing applications.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.210-213
• /
• 2006

The objectives of this study is to find out the relationship of crack width and residual seismic capacity of Unreinforced Masonry(URM) walls which were damaged by earthquake. Three URM walls which made the shape ratio(1/h, 1.0, 1.5, 2.0)to be a variable were tested for the objective. It was seen that the crack width increased with growing at rotation angle. Also, this study found out that failure mode affects crack type of URM. In other words, horizontal and vertical crack was increased in rocking and sliding failure mode respectively.

• Transactions of Materials Processing
• /
• v.9 no.4
• /
• pp.339-347
• /
• 2000

For the successful forming of tailored blank, it is important to control the deformation of the stretch flange mode, which is strong1y dependent upon the location of weld line and blank shape. In order to investigate the effects of tailored blank design factors on the stretch flange forming, we made the model die which can simulate stretch flange mode. Taguchi method was employed to analyze the sensitivity of blank design factors for the forming of tailored blank. From the results of experiment S/N ratios were calculated and using Variance Analysis, significance of parameters and optimal condition of each factors were extracted. Based on these analyses, the weld line height and the strength ratio and the arc center height were selected as effective parameter. The analysed result was practically applied for Side outer panel stamping process.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1998.04a
• /
• pp.131-138
• /
• 1998

Structural damage is used to be modeled through reductions in the stiffness of structural elements for the purpose of damage estimation of structural system. In this study, the concept of joint damage is employed for more realistic damage assessment of a steel structure. The joint damage is estimated damage based on the mode shape informations using neural networks. The beam-to-column connection in a steel frame structure is represented by a rotational spring at the fixed end of a beam element. The severity of joint damage is defined as the reduction ratio of the connection stiffness with respect to the value of the intact joint. The concept of the substructural identification is used for the localized damage assessment in a large structure. The feasibility of the proposed method is examined using an example with simulated data. It has been found that the joint damages can be reasonably estimated for the case with the measurements of the mode vectors subjected to noise.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.2
• /
• pp.20-27
• /
• 1996

Ice loads can determined by many factors like ice properies and dimension, velocity and type of structures. The magnitude of ice load varies with the failure mode which can be predicted by failure maps if the aspect ratio and strain rate are known. To reduce the ice force, various types of structure have been investigated and it is now known that the identor shape plays an important role in reducing ice load on Arctic offshoe structures. The conical and wedge structures are good applied examples in the Arctic region. In this study, ice forces on single wedge indentors are investigated for crushing failure mode. The ice loads on wedged indentors are compared with those on cylindrical structures. Also the concept of "ice annual"is introduced to verify the ice loads to multi and single wedge structures.tructures.

• Structural Engineering and Mechanics
• /
• v.54 no.3
• /
• pp.419-432
• /
• 2015

The free vibration of rotating Euler-Bernoulli beams with the thickness and/or width of the cross-section vary linearly along the length is investigated by using the Adomian modified decomposition method (AMDM). Based on the AMDM, the governing differential equation for the rotating tapered beam becomes a recursive algebraic equation. By using the boundary condition equations, the dimensionless natural frequencies and the closed form series solution of the corresponding mode shapes can be easily obtained simultaneously. The computed results for different taper ratios as well as different offset length and rotational speeds are presented in several tables and figures. The accuracy is assured from the convergence and comparison with the previous published results. It is shown that the AMDM provides an accurate and straightforward method of free vibration analysis of rotating tapered beams.