• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.675-682
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• 2015

Current design codes such as AASHTO LRFD or Korean Highway Bridge Design Code recommend of using static force for designing bridge column against vehicle collisions. However, there was an accident that the bridge was collapsed shortly after vehicle impact on bridge pier in Nebraska(near Big Spring, 2003). It was found that the second largest cause of bridge collapse is collision after hydraulic causes. It can be thought that the possibility of truck-bridge collision are getting increasing as the size of truck increases and traffic condition are becoming improved. However, dynamic behavior under the impact loading seldom considered in bridge design procedure due to computational cost and time. In this study, in order to reduce the computational cost for dynamic impact analysis, model reduction method was developed. Obtained results of residual displacement were compared with the results of direct impact simulations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.145-152
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• 2015

In the study, the effects of damping devices on damping ratio increase and wind-load reduction were investigated based on the computational platform, which is one of the parametric modeling methods. The computational platform helps the designers or engineers to evaluate the efficacy of the numerous alternative structural systems for irregular Super-Tall building, which is crucial in determining the capacity and the number of the supplemental damping devices for adding the required damping ratios to the building. The inherent damping ratio was estimated based on the related domestic and foreign researches conducted by using real wind-load records. Two types of damping devices were considered: One is inter-story installation type passive control devices and the other is mass type active control devices. The supplemental damping ratio due to the damping devices was calculated by means of equivalent static analysis using an equation suggested by FEMA. The optimal design of the damping devices was conducted by using the computational platform. The structural element quantity reduction effect resulting from the installation of the damping devices could be simply assessed by proposing a wind-load reduction factor, and the effectiveness of the proposed method was verified by a numerical example of a 455m high-rise building. The comparison between roof displacement and the story shear forces by the nonlinear time history analysis and the proposed method indicated that the proposed method could simply but approximately estimate the effects of the supplemental damping devices on the roof displacement and the member force reduction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.73-85
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• 2014

The CFT (Concrete Filled steel Tubes) column-footing connection is cast-in-place embedded type which provides simple construction procedure, low cost, and superior structural performance. In this study, CFT column-footing connection of modular pier is proposed and structural performance is evaluated by experimental tests. To evaluate structural performance of the CFT column-footing connection, a series of experimental tests were performed for the 4 specimens with different embedded depth. As a result of the quasi-static test, the specimen with 0.6D (0.6 times the outside diameter of steel tube) embedded depth showed relatively low ductility than other specimens with larger embedded depth due to cone failure of base concrete occurred during the lower loading step. On the contrary, cone failure of the base concrete was not observed in the specimens with larger embedded depth than 0.9D, but typical flexural failure in lower part of CFT column was observed. With the analyses of force-displacement curve, displacement ductility, and energy dissipation capacity, it is concluded that the rational range of embedded depth of the CFT column-footing connection is from 0.9D to 1.2D in view of good seismic performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.1
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• pp.31-40
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• 2017

Absolute nodal coordinate formulation was developed in the mid-1990s, and is used in the flexible dynamic analysis. In the process of deriving the equation of motion, if the order of polynomial referring to the displacement field increases, then the degrees of freedom increase, as well as the analysis time increases. Therefore, in this study, the primary objective was to reduce the analysis time by transforming the dimensional equation of motion to a non-dimensional equation of motion. After the shape function was rearranged to be non-dimensional and the nodal coordinate was rearranged to be in length dimension, the non-dimensional mass matrix, stiffness matrix, and conservative force was derived from the non-dimensional variables. The verification and efficiency of this non-dimensional equation of motion was performed using two examples; cantilever beam which has the exact solution about static deflection and flexible pendulum.

• Journal of Korean Society of Steel Construction
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• v.26 no.6
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• pp.523-535
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• 2014

According to the capacity design concept underlying current steel seimsic provisions, the braces in concentrically braced frames should dissipate seismic energy through cyclic tension yielding and compression buckling. On the other hand, the beams and the columns in the braced bay should remain elastic for gravity load actions and additional column axial forces resulting from the brace buckling and yielding. However, due to the difficulty in accumulating the yielding and buckling-induced column forces from different stories, empirical and often conservative approaches have been used in design practice. Recently a totally different approach was proposed by Cho, Lee, and Kim (2011) for the prediction of column axial forces in inverted V-braced frames by explicitly considering brace buckling. The idea proposed in their study is extended to X-braced seismic frames which have structural member configurations and load transfer mechanism different from those of inverted V-braced frames. Especially, a more efficient rule is proposed in combining multi-mode effects on the column axial forces by using the modal-mass based weighting factor. The four methods proposed in this study are evaluated based on extensive inelastic dynamic analysis results.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.3
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• pp.222-228
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• 2011

Purpose: The purposes of this study were to evaluate the stress distributions and the displacements of obturator for edentulous maxillectomy patients and to compare them with those of complete denture using three-dimensional finite element analysis. Materials and methods: Based on the CT image of edentulous patient, three-dimensional finite element model of edentulous maxillae was constructed. Three-dimensional finite element model of edentulous maxillae with palatal defect was also fabricated. On each model, complete denture and obturator prosthesis were created. Vertical static force of 200 N was applied on the left maxillary premolar and molar region. The von Mises stress values and the displacements of models were analyzed using three-dimensional finite element analysis. Results: Maximum von Mises stress values were recorded in the cortical bones of both models. The von Mises stress value in the complete denture model was 2.73 MPa and 2.69 MPa in the obturator model. High von Mises stress values were also observed on the tissue surface of prosthesis. The maximum value of the displacement in the obturator was higher than that of complete denture. Conclusion: The obturator showed a worse result in terms of stress distribution and displacement than complete denture. In the prosthodontic rehabilitation of edentulous maxillectomy patient accurate impression procedure based on patients'anatomy and application of prosthodontic principle should be considered.

• International Journal of Costume and Fashion
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• v.11 no.1
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• pp.15-33
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• 2011

The late $19^{th}$ and early $20^{th}$ centuries of Korea were the times when the Confucianism (牲理學) ideology was shaken heavily under the influences of modernism and capitalism by Western and Japanese military and political-economic forces. Under such circumstances, alteration of clothing was much influenced by ideologies than changes in social structure or technological advance. In this study, an ideology was defined as "the force which drives people into a particular social order". Ideologies were postulated as an ongoing process of socialization with dialectic features rather than being a static state. Comparative analyses on conflict structures and different clothing patterns symbolizing the ideologies of the Ruling (支配) and the Opposition (對抗) were conducted. Investigating dresses as representations of ideologies is to reconsider the notion of dichotomous confrontation between the conservatives (守舊派) and the progressives (開化派) and a recognition of Koreans' passively accepting modernity during the Japanese occupation. This may also have contributed to enlightening Koreans about modernization. Here are the results. First, the theoretical review found that ideologies were represented by not only symbols of discourse, but also dresses, and that dresses embodied both physical and conceptual systems presenting differences between ideologies and their natures, Second, during the late 19th century Korea, conflict between conservatives' Hanbok (韓服) and progressives' Western suits (洋服) was found. Moderate progressives showed their identity by "Colored Clothing" (深色衣), and radical progressives by black suits with short hair (黑衣斷髮) or by western suits (洋服). The ultimate goal of both parties was a "Modern Nation". With these efforts, pale jade green coats and traditional hats symbolizing the nobleman class was eliminated within 30 years from 1880 to 1910, and then simple robes and short hair emerged. However, the powerful Japanese army had taken over the hegemony of East Asia, and Korea was sharply divided into modernization and pro-Japanese camps. Third, during the time of Japanese colonial rule, the dress codes having set by the modernization policies during the time of enlightenment were abandoned and colonial uniforms for the colonial system was meticulously introduced. During this period, Western or Japanese-style uniforms were the symbol of the ruling ideology. In the mean time, Hanbok, particularly "White Clothing (白衣)", emerged as a representation of the opposition ideology. However, due to Japan's coercive power and strong zeal for "Great orient (大東亞)", white clothing remained as a mere symbol. Meanwhile, Reformists (實力養成論者) movement toward improving quality of life followed a similar path of the Japanese policies and was eventually incorporated into the ruling ideology. Fourth, dresses as representations of ruling ideologies were enforced by organizational powers, such as organizations and laws, and binding policies, and changes in such dresses were more significant when the ruling ideologies were stronger. Clothing of the opposition ideology was expressed as an aggregation of public consciousness. During the period, the subjects of ruling ideology and the objects who were granted modernization benefits were different although their drives for colored clothing with short hair (色衣斷髮) for modernization were similar.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7134-7147
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• 2014

This study examined one of the contemporary issues that may be interesting to academics and practitioners regarding the driving force of the growth rate for the firms belonging to the chaebols in the Korean capital markets. With respect to the empirical results obtained from two hypothesis tests, the first hypothesis was to identify any financial determinants on the growth rate by applying both dynamic panel data and static panel data models. The debt ratios relevant to the book- and market-value showed their positive relationships with the DV of GROWTH1, along with other significant IDVs such as one-period lagged DV of GROWTH_1, SIZE1 and FOS with statistical significance. Second, by employing conditional quantile regression (CQR) analysis, the control variables, such as ROA, SMARKET, time dummy variable of F2010 and F2011, and the industry dummies of IND3 and IND10, provided evidence of their significant influences on DV of GROWTH1.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.595-602
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• 2006

An experimental study was conducted to investigate seismic behaviour of post-tensioned(PT) exterior slab-column connections used for the purpose to resist gravity loads only. For these, 2/3-scale, two PT post-tensioned exterior connections with two different tendon arrangement patterns and one conventional reinforced concrete(RC) exterior connection was tested under quasi-static, uni-directional reversed cyclic loading. During the lateral testing, gravity forces transferred to the column were kept constant to closely simulate a moment to shear ratio of a real building. One of the objectives of this study was to assess the necessity and/or the quantity of bottom bonded reinforcement needed to resist moment reversal which would occur under significant inelastic deformations of the adjacent lateral force resisting systems. The ACI 318 and 352 provisions for structural integrity were applied to provide the bottom reinforcement passing through the column for the specimens. Prior test results were also collected to conduct comparative studies for some design parameters such as the tendon arrangement pattern, the effect of post-tensioning forces and the use of bottom bonded reinforcement. Consequently, the impact of tendon arrangement on the seismic performance of the PT connection, that is lateral drift capacity and ductility, dissipated energy and failure mechanism, was considerable. Moreover, test results showed that the amount of bottom reinforcement specified by ACI 352. 1R-89 was sufficient for resisting positive moments arising from moment reversal under reversed cyclic loads. Shear strength of the tested specimens was more accurately predicted by the shear strength equation(ACI 318) considering the average compressive stress over the concrete($f_{pc}$) due to post-tensioning forces than that without considering $f_{pc}$.

• Geotechnical Engineering
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• v.7 no.1
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• pp.41-52
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• 1991

A study of the effects of dynamic pile-soil-structure interactions on the response of super- structures, supported by group piles, are presented in this paper. The dynamic impedance functions of single pile generated by soil-pile interactions are obtained and compared among others using the methods proposed by Novak, Gazetas, and Kuhlemeyer, and using the equivalent cantilever method. Group pile effects are also considered by the following approaches : neglecting interaction effects : group efficiency ratio concept : static interaction approach . and dynamic interaction approach. The responses of a nuclear containment structure are obtained by using the elastic half-space analysis, based on the impedance functions mentioned above. Main conclusions drawn from this study are as follows : 1. The numerical results of the impedance functions calculated by each method were quite different : the Novak's was the smallest, and the Kuhlemeyer's the highest. Considering group effects, similar values in each approach were obtained for the stiffness : the difference was very big for the damping. 2. The top displacement of the structure was reduced by 20% or more by pile installations. However, the base shear force, the base moment, and the resonance frequency were increased by more than two times due to stiffening effect of the ground by pile installations. 3. Whether frequency dependant impedence functions or frequency independant functions were used, the responses of the structure were not so much affected by the choice of the impedance functions. 4. The reduction effect of the top displacement increased with the increase of the maximum ground acceleration.