• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.950-953
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• 2006

The floor impact noise of concrete structures in apartments buildings is affected from the flexural wave propagation characteristics. Accordingly, the measurement of wave propagation characteristics is required for suggestion of efficient method to reduce the impact noise. The purpose of this article is to propose an experimental technique to measure dynamic properties of concrete structures. The method was proposed using the flexural wave propagation characteristics. Wave speeds, bending stiffness and their loss factors are estimated from which the vibration dissipation capabilities are investigated. Several different concrete beam structures were custom-built for measurement. The damping treatments using viscoelastic materials for reducing noise generation are also tested. The beam transfer function of the damped beam is predicted using the compressional damping model from which the mechanism of the vibration energy dissipation is investigated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.11 s.104
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• pp.1255-1261
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• 2005

The dynamic contact model of a beam that contacts to a rigid wall in a reactor core was studied. The gap between the beam and contact wall results in dynamic contact accompanying inequality constraints. The inequality constraints can be relieved to an equality constraint problem by introducing a convex Penalty function. In this work, a beam with contact condition is formulated using quasi-convex penalty function and numerically solved. General coordinate solution is adopted to raise computational efficiency. Also nonlinearity is examined In the beam contacting to a rigid wall.

• Structural Engineering and Mechanics
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• v.9 no.5
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• pp.449-467
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• 2000

The natural frequencies and the corresponding mode shapes of a non-uniform beam carrying multiple point masses are determined by using the analytical-and-numerical-combined method. To confirm the reliability of the last approach, all the presented results are compared with those obtained from the existing literature or the conventional finite element method and close agreement is achieved. For a "uniform" beam, the natural frequencies and mode shapes of the "clamped-hinged" beam are exactly equal to those of the "hinged-clamped" beam so that one eigenvalue equation is available for two boundary conditions, but this is not true for a "non-uniform" beam. To improve this drawback, a simple transformation function ${\varphi}({\xi})=(e+{\xi}{\alpha})^2$ is presented. Where ${\xi}=x/L$ is the ratio of the axial coordinate x to the beam length L, ${\alpha}$ is a taper constant for the non-uniform beam, e=1.0 for "positive" taper and e=1.0+$|{\alpha}|$ for "negative" taper (where $|{\alpha}|$ is the absolute value of ${\alpha}$). Based on the last function, the eigenvalue equation for a non-uniform beam with "positive" taper (with increasingly varying stiffness) is also available for that with "negative" taper (with decreasingly varying stiffness) so that half of the effort may be saved. For the purpose of comparison, the eigenvalue equations for a positively-tapered beam with five types of boundary conditions are derived. Besides, a general expression for the "normal" mode shapes of the non-uniform beam is also presented.

• Transactions of Materials Processing
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• v.22 no.7
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• pp.383-388
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• 2013

Metal flow of the beam blank during H-beam rolling was examined in order to correlate the rolling defects with the beam blank configuration. For this purpose, H-beam rolling was performed on the beam blank where stainless steel bolts were inserted as the marker at the web and flange. The positional variation of the marker was monitored at each rolling pass, and the result was compared with the 3D FEM simulation employing the point tracking function. The simulation results were reasonably agreed with the experimental within the error of 0.5~1mm on both web and flange of the H-beam. It is anticipated that the 3D FEM simulation employing the point tracking function provides the guidance information on analyzing the correlation between the rolling defects and the beam blank configuration in H-beam rolling.

• Structural Engineering and Mechanics
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• v.63 no.1
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• pp.11-21
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• 2017

In this paper, the efficiency and the accuracy of classical (CE) and high order (HE) beam element are improved by introducing two novel techniques. The first proposed element (FPE) provides an alternative for (HE) by taking the mode shapes of the clamped-clamped (C-C) beam into account. The second proposed element (SPE) which could be utilized instead of (CE) and (HE) considers not only the mode shapes of the (C-C) beam but also some virtual nodes. It is numerically proven that the eigenvalue problem and the frequency response function for Euler-Bernoulli beam are obtained more accurate and efficient in contrast to the traditional ones.

• Computers and Concrete
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• v.24 no.4
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• pp.313-327
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• 2019

The purpose of the present study is to present a new approach to designing and selecting the details of multidimensional continuous RC beam by applying all strength, serviceability, ductility and other constraints based on ACI318-14 using Teaching Learning Based Optimization (TLBO) algorithm. The optimum reinforcement detailing of longitudinal bars is done in two steps. in the first stage, only the dimensions of the beam in each span are considered as the variables of the optimization algorithm. in the second stage, the optimal design of the longitudinal bars of the beam is made according to the first step inputs. In the optimum shear reinforcement, using gradient-based methods, the most optimal possible mode is selected based on the existing assumptions. The objective function in this study is a cost function that includes the cost of concrete, formwork and reinforcing steel bars. The steel used in the objective function is the sum of longitudinal and shear bars. The use of a catalog list consisting of all existing patterns of longitudinal bars based on the minimum rules of the regulation in the second stage, leads to a sharp reduction in the volume of calculations and the achievement of the best solution. Three example with varying degrees of complexity, have been selected in order to investigate the optimal design of the longitudinal and shear reinforcement of continuous beam.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.111-112
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• 2007

The spatial coherence function of laser beam was measured by using a Sagnac interferometer and self referencing technique. For laser beam passing through a narrow slit, absolute value of measured spatial coherence function becomes more symmetric as the slit size is reduced. For diverging beams, the spatial coherence function shows fast oscillations in its real and imaginary parts. We explain this by using a Gaussian Schell-model. One can use this measurement method to study and characterize the property of light field coming out of small sample.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.507-510
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• 2004

Oblique ion-induced secondary electron emission coefficient(${\gamma}$) with low energy ..and work function ${\phi}_{\omega}$(${\theta}$ = 0 and ${\theta}$ = 20) of the MgO thin film in AC-PDPs has been measured by ${\gamma}$-FIB system. The MgO thin film has been deposited from sintered material under electron beam evaporation method. The energy of $He^+$ ions used has been ranged from 50eV to 150eV. Oblique ion beam has been chosen to be 10 degree, 20 degree and 30 degree. It is found that the higher secondary electron emission coefficient(${\gamma}$) has been achieved by the higher oblique ion beam up to inclination angle of 30 degree than the perpendicular incident ion beam.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.5
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• pp.123-130
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• 2001

The purpose of this paper is to reduce the level of idling vibration on a steering wheel. In some cases, vibration on steering wheel is amplified due to the resonance between the first natural frequency of T-beam and engine idling speed. Using SDM(structural dynamic modification) technique, T-beam is redesigned to reduce its vibration. This paper used FRF(frequency response function) synthesis technique which is entirely dependent on experiment. But this method requires lots of test efforts to enhance its reliability of design. While combining this method with an analytic method. the experimental burden, the major drawback of FRP synthesis method, can be considerably relieved. Using ana1ytic sensitivity analysis, some effective modification regions are preliminarily chosen as candidate Positions where SDM can be applied to modify T-beam\`s dynamic characteristics.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.474-478
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• 1992

The non-rational transfer function of a Bernoulli-Euler beam, as an important component of a flexible structure, is analyzed. The true pattern of zeros of that transfer function is investigated as a function of sensor and actuator seperation. Translational displacement sensors are used for two cases in which a force input and a moment input are seperately applied. When the displacement sensor is located at a certain point, the first pair of zeros on the real axis of the s-plane arrive at the origin and cancel the rigid-body mode. The location of the translational displacement sensors on the beamat which the rigid-body mode of the beam is unobservable is analyzed as the center of percussion and is uniquely located for each case. If sensor is moved beyond such a point, a pair of zeros appear on the imaginary axis and move away from the origin along the imaginary axis of the s-plane.