• Structural Engineering and Mechanics
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• 제38권3호
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• pp.261-281
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• 2011

A new method of formulation of a class of elements that are immune to mesh distortion effects is proposed here. The simple three-noded bar element with an offset of the internal node from the element center is employed here to demonstrate the method and the principles on which it is founded upon. Using the function space approach, the modified formulation is shown here to be superior to the conventional isoparametric version of the element since it satisfies the completeness requirement as the metric formulation, and yet it is in agreement with the best-fit paradigm in both the metric and the parametric domains. Furthermore, the element error is limited to only those that are permissible by the classical projection theorem of strains and stresses. Unlike its conventional counterpart, the modified element is thus not prone to any errors from mesh distortion. The element formulation is symmetric and thus satisfies the requirement of the conservative nature of problems associated with all self-adjoint differential operators. The present paper indicates that a proper mapping set for distortion immune elements constitutes geometric and displacement interpolations through parametric and metric shape functions respectively, with the metric components in the displacement/strain replaced by the equivalent geometric interpolation in parametric co-ordinates.

• 한국의류학회지
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• 제23권5호
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• pp.745-756
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• 1999

The purpose of this study is to investigate the characteristics of the clothing consumption expenditures by the business cycles in Korea during the period of first quarter of 1979 to second quarter of 1998. Business cycles were examined using data GNP from the National Accounts published by the Bank of Korea and clothing expenditures from the monthly statistics of Korea published by the National Statistical Office of Korea. Data were analyzed by regression analysis standard deviation sample cross-correlation coefficient and skewness statistics. The main results are as follows. 1. During the period of 1979.I-1998.II GNP and per-person consumption expenditures for clothing and shoes have continuously increased except during 1980 and the recent depression of the national economy. Clothing expenditures dropped severely during the two recent depression of the national economy. Clothing expenditure dropped severely during the two depression periods. Clothing expenditures were the highest in the fourth quarter and the lowest in the third quarter of the year. 2. According to the results of the regression analysis the business cycles had a significant influence on the clothing expenditures. the volatility of the clothing expenditure was 2.60 times higher than that of the business cycles. 3. Clothing expenditures displayed procyclical fluctuation and coincident movement to the business cycles. Also clothing expenditures showed an unsymmetric behavior over the expansion phases and contraction phases of the business cycles. That is the clothing expenditures increased slowly in the expansion phases and decreased quickly and severely in the contraction phases of the business cycles.

• 한국소음진동공학회논문집
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• 제18권12호
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• pp.1293-1300
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• 2008

This paper presents an active vibration control of cantilever beams under disturbances by a primary force. A direct velocity feedback control using a pair of PZT actuator and a velocity sensor is considered. Variation of the stability and performance with the locations of the sensor/actuator pair is investigated. It is found that the maximum gain varies with the locations of the sensor/actuator pair significantly. The maximum gain shows a symmetric distribution along the beam length with respect to the center point, although the boundary condition of the beam is unsymmetric. The control performance is affected by the location of the primary force as well as the location of the sensor/actuator pair. The active control system can more effectively reduce the vibration when the primary force is located close to the fixed boundary.

• Bulletin of the Korean Chemical Society
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• 제18권6호
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• pp.653-656
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• 1997

The new unsymmetric $N_6$ ligand 1-amino-13-(2-pyridyl)-3,6,9,12-tetraazatridecane (aptatd) containing one pyridyl group has been synthesized and characterized by EA, IR, and NMR. Its proton association constants $(log K_H^n)$ and stability constants $(log K_{ML})$ for Co(Ⅱ), Ni(Ⅱ), Cu(Ⅱ), and Zn(Ⅱ) ions were determined at 298.1 K and ionic strength 0.100 mol $dm^{-3}$ (KNO₃) in aqueous solution by potentiometry: log $K_H^1$=8.80, log $K_H^2$=8.49, log $K_H^3$=6.84, log $K_H^4$=4.17, log $K_H^5$=3.47; log $K_{ML}(Co^{2+})$=18.00, log $K_{ML}(Ni^{2+})$=21.31, log $K_{ML}(Cu^{2+})$=23.62, log $K_{ML}(Zn^{2+})$=15.60. The X-ray structure of its nickel(Ⅱ) complex [Ni(aptatd)]$(ClO_4)_2$ are reported: orthorhombic space group Pbca, a=15.715(1) Å, b=14.280(2) Å, c=19.443(2) Å, V=4363.4 (9) ų with Z=8. The geometry around nickel is a distorted octahedron with the pyridine nitrogen atom being cis to the nitrogen atom of the terminal primary amine.

• 한국지진공학회논문집
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• 제23권1호
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• pp.31-42
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• 2019

In this study, the results of an analytical investigation on the seismic behavior of two residential 4-story bearing wall buildings with pilotis, each of which has symmetric or unsymmetric wall arrangement at their piloti level, are presented. The dynamic characteristics and lateral resistance of the piloti buildings were investigated through linear elastic and nonlinear static analyses. According to the results, the analytical natural period of vibration of the piloti buildings were significantly shorter than the fundamental period calculated in accordance with KBC 2016. In the initial elastic behavior, the walls resisting in-plane shear contributed to the lateral stiffness and strength, while the contribution of columns resisting flexural moments in double curvature was limited. However, after the shear cracking and yielding of the walls occurred, the columns significantly contributed to the residual strength and ductility. Based on those investigations, design recommendations of low-rise bearing wall buildings with piloti configuration are given.

• 한국전산구조공학회논문집
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• 제34권3호
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• pp.121-128
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• 2021

본 연구에서는 비틀림비정형성과 수직비정형성을 가진 RC 필로티 건축물의 지진동에 대한 거동을 층강성을 적용하여 간단하게 모델링하는 선형 동적해석 프로그램을 개발하고자 한다. 개발된 동적 해석 프로그램을 적용하여 필로티 건축물의 동적 거동 및 필로티층 각 기둥의 전단력을 분석하고, 필로티층에 전단벽 또는 가새를 보강하였을 때 보강효과를 평가하고자 한다. 모서리코어가 있는 필로티 건축물에서 필로티층의 코어 반대편 모서리를 전단벽이나 K형 가새로 보강하였을 때 변위와 기둥 전단력이 크게 감소하는 것으로 나타났으며, 모서리 양면을 K형 가새로 보강하는 것보다 한 면을 전단벽으로 보강하는 것이 보강효과가 큰 것으로 나타났다.

• Steel and Composite Structures
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• 제43권1호
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• pp.67-77
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• 2022

In the current study, ordinary design of Represstessed Pre-Flex (RPF) girder by classical beam theory and numerical model taking buckled shape into consideration were compared with field-survey data to find imperfections on the RPF girder before prestressing and after preflexion. It should be noted that the ordinary design do not consider deformed shape of steel girder in RPF beam. The deformed shapes of steel girder due to the incomplete fabrication that could be caused by self-weight, preflexion misalignment, existence of lateral bracing at mid-span and stiffness of reaction frame were found using a newly developed model which was verified against a deformation survey conducted on actual RPF girder in the field. The final observed deformed shapes of RPF after concrete shrinkage and before prestressing were classified into W, C and Unsymmetric shapes in regard to both survey and analytical results. The deformation survey showed negligible amount of unwanted deformation compared to the large size of the RPF girders. The shallower width of the bottom flange of steel girder caused amount of lateral torsional buckling under self-weight and preflexion thereby affecting the unwanted final overall shape of the RPF girders. However, it was found that the unwanted deformation of RPF girders by fabrication errors even though it is negligible compared to the size of the girder, caused unsymmetrical stress contours in concrete and additional tensile stress and raise some safety issues.

• 한국항만학회지
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• 제12권1호
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• pp.95-104
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• 1998

Water pollution in a semi-enclosed sea area such as a bay due to stagnancy of water has been a serious water environmental problem. Recently, some kinds of new methods to activate the tidal exchange between an inner bay and an outer sea area by control of a tidal residual current have been proposed. However, these methods have several problems, that is, I). deterioration in a natural view due to building of huge structures, II). increase of risk of navigation in case of a submerged structure, III). limition of sea area where a tidal current can be controlled and IV). difficulty in removing those structures in case of occurrence of an unexpected impact on water environment. In this paper, a new method is proposed, which can solve all the above problems, to purify water quality in a semi-enclosed bay by creation and control of a pattern of a tidal residual current. The tidal residual current is controlled by unsymmetric structures, which change the properties of resistance according to the direction of flow, arranged on the sea bottom. In this study, several numerical and hydraulic experiments of tidal current and particle-tracking for various arrangements of bottom roughness in a semi-enclosed model bay were carried out. As a result of experiments, it becomes clear that it is possible to generate a new tidal residual current and to activate a tidal exchange by only operation of bottom roughness arrangement.

• Steel and Composite Structures
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• 제49권5호
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• pp.547-570
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• 2023

In the present work, a comparative study has been carried out between power, exponential, and sigmoidal sandwich FGM plates for free vibration conditions under hygro-thermal conditions. Rules of mixture is used to determine effective material properties across the thickness for power-law and sigmoid sandwich FGM plates. Exponential law is used to plot effective material properties for exponentially graded sandwich FGM plates. Temperature and moisture dependent material properties were used during the analysis. Free vibration analysis is carried out using recently proposed finite element based HOZT. Present formulation satisfies interlayer transverse stress continuity conditions at interfaces and transverse shear stress-free conditions at the plate's top and bottom surfaces. The present model is free from any penalty or post-processing requirements. Several new results are reported in the present work, especially for unsymmetric sandwich FGM plates and exponential and sigmoidal sandwich FGM plates.

• 한국항만학회지
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• 제13권1호
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• pp.123-132
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• 1999

It is very important to quantitatively assess the movement of sea water and pollutant dispersion before or after constructing shore structures such as breakwater considering marine environment and long-term utilization of those structures. This assesment is possible through the use of simulation models designed to predict water movement and pollutant dispersion in a certain area. In this study the numerical computations were carried out to predict the sea water quality in the Ilgwang Harbor located at the east coast of Pusan. The flow patters were investigated before and after the development of Ilgwang Harbor. The computational models adopting ADI Method (Alternating Direction Implicit Method) were used here and were already verified from the previous studies. As a results of this study the tidal exchange in Ilgwang Harbor after development proved to be worse due to the increased semi-enclosed at the harbor limit. In order to improve the water quality of this area after development a new method was proposed to improve water quality in the semi-enclosed bay by creation and control of tidal residual currents. For this purpose the unsymmetric structures so called bottom roughness were introduced in this study. The simulation was carried out on the basis of the study by Komatsu et. al. and Gug and we made a conclusion that it is possible to generate a new tidal residual current and to increase the tidal exchange by application of bottom roughness arrangement.