• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.5
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• pp.233-241
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• 2020

This paper is to investigate the retrofitting effect for a non-seismic reinforced concrete frame strengthened by perimeter steel moment frames with indirect integrity, which ameliorates the problems of the direct integrity method. To achieve this, first, full-scale tests were conducted to address the structural behavior of a two-story non-seismic reinforced concrete frame and a strengthened frame. The non-seismic frame showed a maximum strength of 185 kN because the flexural-shear failure at the bottom end of columns on the first floor was governed, and shear cracks were concentrated at the beam-column joints on the second floor. The strengthened frame possessed a maximum strength of 338 kN, which is more than 1.8 times that of the non-seismic specimen. A considerable decrease in the quantity of cracks for the strengthened frame was observed compared with the non-seismic frame, while there was the obvious appearance of the failure pattern due to the shear crack. The lateral-resisting capacity for the non-seismic bare frame and the strengthened frame may be determined per the specified shear strength of the reinforced columns in accordance with the distance to a critical section. The effective depth of the column may be referred to as the longitudinal length from the border between the column and the foundation. The lateral-resisting capacity for the non-seismic bare frame and the strengthened frame may be reasonably determined per the specified shear strength of the reinforced columns in accordance with the distance to a critical section. The effective depth of the column may be referred to as the longitudinal length from the border between the column and the foundation. The proposed method had an error of about 2.2% for the non-seismic details and about 4.4% for the strengthened frame based on the closed results versus the experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.801-804
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• 2006

The purpose of this paper is to investigate the stability of stepped cantilever columns with a tip mass of rotatory inertia and a translational spring at one end. The column model is based on the Bernoulli-Euler theory which neglects the effects of rotatory inertia and shear deformation. The governing differential equation for the free vibration of columns with stepwise variable cross-section and subjected to a subtangential follower force is solved numerically using the corresponding boundary conditions. And the bisection method is used to calculate the critical divergence/flutter load. The frequency and critical divergence/flutter load for the stepped column with a single step are presented as functions of various non-dimensional system parameters: the segmental length parameter, the section ratio, the subtangential parameter, the mass, the moment of inertia of the mass, and the spring parameter.

• Asian Journal for Public Opinion Research
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• v.4 no.4
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• pp.246-259
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• 2017

The purpose of this study is to evaluate the effects of critical friends on self-esteem and the academic oral presentation ability of undergraduate students. A pretest was conducted in the first week of the semester. A pre-academic oral presentation preparation was held from the second week to the seventh week and followed by pedagogical speech activities from the eighth week to the eleventh week. The research instruments are Academic oral presentation behavior and self-esteem evaluation forms. The samples were 37 third year undergraduate students, who were purposively selected from the educational technology class at the Chulalongkorn University. The statistics used for analyzing quantitative data are frequencies, means, standard deviations, one sample t-tests, and Pearson's Product-Moment Correlations. It was found that the 37 third year undergraduate teacher students had higher self-esteem at the statistically significant level of .05 and academic oral presentation scores after the activity were statistically significant at the .05 level.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.1
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• pp.111-116
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• 2015

There has been a string of negligent accidents at the seaside. In addition, there is a shortage of professional equipment to deal with these negligent accidents at present. The purpose of this paper is to assess the development of a rescue lift using a structural analysis. The critical load of a support pipe on the rescue lift is investigated in this paper. The stability of the rescue lift is also determined in a structural analysis. In the critical load analysis, the effects of variations in the pipe length and the ratio of the moment of inertia are investigated. The total weight of the developed rescue lift is approximately 20.7kg, and the lift passed the load tests.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.8
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• pp.862-869
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• 2007

The compressive and torsional buckling behavior of carbon nanotube bundles at room temperature is examined with classical molecular dynamics simulation. The critical compressive load and stiffness of a single carbon nanotube in the bundle are found to be similar to those of individual carbon nanotubes. However, the critical torsional moment and stiffness of a single carbon nanotube in the bundle are found to be higher than those of individual carbon nanotubes. In addition, this study demonstrates that van der Waals interactions between the nanotubes in the bundle significantly affect the critical compressive load of the nanotube bundle.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.763-769
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• 2012

We investigated the width (N) dependence on the magnetization of N-ZSiC NR with electron and hole doping on the basis of systematic DFT calculations. The critical values of the upper and down critical concentration to give the maximum and zero magnetic moment at edge Si/C atoms by electron/hole doping ($x_{up,e}$, $x_{down,e}$, $x_{up,h}$, and $x_{down,h}$) depend on the width of N-ZSiC NR. Moreover, due to $x_{up,e}\;{\neq}\;x_{up,h}$ and $x_{down,e}\;{\neq}\;x_{down,h}$, the electron and hole doping effect are asymmetry, i.e, the critical electron doping value ($x_{down,e}$) is smaller than the critical hole doping value ($x_{down,h}$) and is almost independent of the width of NZSiC NR though the other critical values of the electron and hole doping that influence the magnetization of N-ZSiC NR depend on the width. It was also found that at $x_{down,e}$ or $x_{down,h}$ doping, the N-ZSiC NR turns into unusual non-magnetic metallic state. The magnetic behavior was discussed based on the band structures and projected density of states (PDOS) under the effect of electron/hole doping.

• Structural Engineering and Mechanics
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• v.46 no.1
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• pp.39-51
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• 2013

An extremum method is presented to predict the wrinkling characteristics of the inflated cone in bending. The wrinkling factor is firstly defined so as to obtain the wrinkling condition. The initial wrinkling location is then determined by searching the maximum of the wrinkling factor. The critical wrinkling load is finally obtained by determining the ratio of the wrinkling moment versus the initial wrinkling location. The extremum method is proposed based on the assumption of membrane material of beam wall, and it is extended to consider beam wall with thin-shell material in the end. The nondimensional analyses show that the initial wrinkling location is closely related to the taper ratio. When the taper ratio is higher than the critical value, the initial wrinkles will be initiated at a different location. The nondimensional critical wrinkling load nonlinearly increases as the taper ratio increases firstly, and then linearly increases after the critical taper ratio. The critical taper ratio reflects the highest load-carrying efficiency of the inflated cone in bending, and it can be regarded as a measure to optimize the geometry of the inflated cone. The comparative analysis shows fairly good agreement between analytical and numerical results. Over the whole range of the comparison, the mean differences are lower than 3%. This gives confidence to use extremum method for bending-wrinkling analysis of inflated conical cantilever beam.

• English Language & Literature Teaching
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• v.16 no.4
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• pp.71-90
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• 2010

This study suggests that English literature educators need to be eclectic and flexible in applying theories and methods, not simply adhering to one or two for all situations and occasions. They need to be available to go with the flow and particularly employ whatever is needed at any given moment of class time. There is a current trend emphasizing English literature as merely a language resource rather than the study of English literature as an end in itself. Without much attention given to literary analysis and criticism, students tend to lack creative and critical thinking abilities. Given the current imbalance, it would seem important to address the issue, and create English class programs that maintain a balance between teaching the study of English literature to improve students' critical thinking abilities, and its use as a language resource. To fulfill this goal, thorough preparation is required. Indeed, we can direct our intelligence more effectively when we are well prepared and we are familiar with the basic methods and mechanics of teaching our subject. The greatest achievement of the English literature class I taught was that the students showed unexpectedly remarkable creative and critical appreciation of the novel we studied, in addition to improving their English language skills.

• Structural Engineering and Mechanics
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• v.11 no.1
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• pp.35-48
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• 2001

The objective of this study is to investigate the stability behavior of steel cable-stayed bridges by comparing the buckling loads obtained by means of finite element methods with eigen-solver. In recent days, cable-stayed bridges dramatically attract engineers' attention due to their structural characteristics and aesthetics. They require a number of design parameters and present a high degree of static indetermination, especially for long span bridges. Cable-stayed bridges exhibit several nonlinear behaviors concurrently under normal design loads due to the individual nonlinearity of substructures such as the pylons, stay cables, and bridge deck, and their interactions. The geometric nonlinearities arise mainly from large displacements of cables. Strong axial and lateral forces acting on the bridge deck and pylons cause structural nonlinear behaviors. The interaction is among the substructures. In this paper, a typical three-span steel cable-stayed bridge with a variety of design parameters has been investigated. The numerical results indicate that the design parameters such as the ratio of $L_1/L$ and $I_p/I_b$ are important for the structural behavior, where $L_1$ is the main span length, L is the total span length of the bridge, $I_p$ is the moment of inertia of the pylon, and $I_b$ is the moment of inertia of the bridge deck. When the ratio $I_p/I_b$ increases, the critical load decreases due to the lack of interaction among substructures. Cable arrangements and the height of pylon are another important factors for this type of bridge in buckling analysis. According to numerical results, the bridges supported by a pylon with harp-type cable arrangement have higher critical loads than the bridges supported by a pylon with fan-type cable arrangement. On contrary, the shape of the pylon does not significantly affect the critical load of this type of bridge. All numerical results have been non-dimensionalized and presented in both tabular and graphical forms.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.345-356
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• 2010

An alternative design method for interior flat plate-column connections subjected to punching shear and unbalanced moment was developed. Since the slab-column connections are severely damaged by flexural cracking before punching shear failure, punching shear was assumed to be resisted mainly by the compression zone of the slab critical section. Considering the interaction with the flexural moment of the slab, the punching shear strength of the compression zone was evaluated based on the material failure criteria of concrete subjected to multiple stresses. The punching shear strength was also used to evaluate the unbalanced moment capacity of the slab-column connections. For verification, the proposed strength model was applied to existing test specimens subjected to direct punching shear or combined punching shear and unbalanced moment. The results showed that the proposed method predicted the strengths of the test specimens better than current design methods in ACI 318 and Eurocode 2.