• Steel and Composite Structures
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• 제19권2호
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• pp.405-416
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• 2015

We proposed the concept of nominal rigidity of a long-span V-shaped rigid frame composite arch bridge, analyzed the effects of structural parameters on nominal rigidity, and derived a theoretical nominal rigidity equation. In addition, we discussed the selection of the arch-to-beam rigidity ratio and its effect on the distribution of internal forces, and analyzed the influence of the ratio on the internal forces. We determined the delimitation value between rigid arch-flexible beam and flexible arch-rigid beam. We summarized the nominal rigidity and arch to beam rigidity ratios of existing bridges. The results show that (1) rigid arch-flexible beam and flexible arch-rigid beam can be defined by the arch-to-beam rigidity ratio; (2) nominal rigidities have no obvious differences among the continuous rigid frame composite arch bridge, V-shaped rigid frame bridge, and arch bridge, which shows that nominal rigidity can reflect the global stiffness of a structure.

• 아태비즈니스연구
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• 제10권4호
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• pp.137-151
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• 2019

Using Korean Labor and Income Panel Study data, this paper estimates nominal wage rigidity in Korea by industry from 2005 to 2017 and evaluates the level of inefficiency of Korean labor market. And, after estimating employment volatility by industry using the Labor Force Survey at Establishments data for Korea, we combine the nominal wage rigidity and the employment volatility estimates and analyze the effect of nominal wage rigidity on employment volatility in Korea from 2011 to 2017. If the level of wage rigidity is high, it may be hard for the labor market to be in the equilibrium, and therefore, the market may have inefficiency. We find that the inefficiency of the labor market in Korea have increased from 2005 to 2017 and the industry of accommodation and food service activities has the highest level of inefficiency over the period. We also find that one-percent-point increase in wage rigidity increases employment volatility by 2.3-2.9 percent and the positive effect is bigger for workers with part-time and temporary jobs. The result implies that firms may adjust their labor costs by changing the number of casual workers, rather than permanent workers, when the labor market suffers from a high level of wage rigidity.

• 노동경제논집
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• 제37권2호
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• pp.1-47
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• 2014

한국노동패널 자료에 나타난 개인임금 자료를 1998년부터 2012년 기간에 대해 분석한 결과 명목임금은 매우 유연한 것으로 나타났다. 프로빗 분석 결과 명목임금이 삭감될 확률은 인플레이션이 낮을수록 그리고 실업률이 높을수록 높게 나타났으며, 다양한 경제 인구학적 집단에 따라 다르게 나타났다. 한편 고용노동부의 사업체 조사와 한국노동패널 조사 자료를 비교 분석한 결과 실질임금은 매우 경기순행적이며, 그 경기변동 상 유연성은 인플레이션의 역할이라기보다는 명목임금 자체가 경기순행적이기 때문인 것으로 나타났다. 이상의 발견들은 임금경직성을 예측하거나 혹은 임금경직성 가정에 의존하여 실업변동을 설명하고자 하는 모형들의 현실 설명력을 반감시킨다. 추가적으로 본고는 임금 및 근로시간 변수에 나타난 측정오차의 문제를 다루고 있다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.161-164
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• 2005

The flexural behavior of a strengthened beam, that is a reinforced. concrete beam with externally bonded fiber sheets, was theoretically and experimentally investigated. The effects of the amount of glass fiber sheets varying from 1 to 4 plies on the flexural capacity of the strengthened beam are also examined. The flexural rigidity of the strengthened beam was enhanced compared with RC beam. In addition, the failure mode and load-deflection relationship for the strengthened beam and the comparison of analysis with experiment are extensive investigated. Finally, the determination of the nominal moment capacity $M_n$ of the strengthened beam will be discussed

• 한국공간구조학회논문집
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• 제22권3호
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• pp.65-72
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• 2022

A typical low and medium-sized neighborhood living facility in reinforced concrete building secures a high floor and pursues an efficient module plan(long span). Accordingly, research on the development of new hybrid beams that can innovatively reduce labor costs such as on-site installation and assembly while securing strength and rigidity is ongoing. In order to verify the structural performance of the U-flanged truss composite beam with newly developed shape, Experiments with various variables are required. Based on the results, this study is to evaluate the strength of U-flanged truss hybrid beam through the flexural strength of the Korea Design Code and experimental values. It was evaluated that nominal flexural strength was 110% to 135% higher than the experimental value.

• Structural Engineering and Mechanics
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• 제32권3호
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• pp.383-398
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• 2009

Applying nonlinear statistical analysis methods in estimating the performance of structures in earthquakes is strongly considered these days. This is due to the methods' simplicity, timely lower cost and reliable estimation in seismic responses in comparison with time-history nonlinear dynamic analysis. Among nonlinear methods, simplified to be incorporated in the future guidelines, Modal Pushover Analysis, known by the abbreviated name of MPA, simply models nonlinear behavior of structures; and presents a very proper estimation of nonlinear dynamic analysis using lateral load pattern appropriate to the mass. Mostly, two kinds of connecting joints, 'hinge' and 'rigid', are carried out in different type of steel structures. However, it should be highly considered that nominal hinge joints usually experience some percentages of fixity and nominal rigid connections do not employ totally rigid. Therefore, concerning the importance of these structures and the significant flexibility effect of connections on force distribution and elements deformation, these connections can be considered as semi-rigid with various percentages of fixity. Since it seems, the application and implementation of MPA method has not been studied on moment-resistant steel frames with semi rigid connections, this research focuses on this topic and issue. In this regard several rigid and semi-rigid steel bending frames with different percentages of fixity are selected. The structural design is performed based on weak beam and strong column. Followed by that, the MPA method is used as an approximated method and Nonlinear Response History Analysis (NL-RHA) as the exact one. Studying the performance of semi-rigid frames in height shows that MPA technique offers reasonably reliable results in these frames. The methods accuracy seems to decrease, when the number of stories increases and does decrease in correlation with the semi-rigidity percentages. This generally implies that the method can be used as a proper device in seismic estimation of different types of low and mid-rise buildings with semi-rigid connections.

• 대한기계학회논문집A
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• 제22권2호
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• pp.416-427
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• 1998

Unidirectional commingled-yarn-based carbon fiber(CF)/polyamide(PA) 6 composite was fabricated under molding pressures of 0.4, 0.6 and 1.0 MPa to study its flexural deformation and fracture behavior. Fiber/matrix interfacial bonding area became larger with an increase of molding pressure from 0.4 to 0.6 MPa. For molding pressures .geq. 0.6 MPa, good flexural performance of similar magnitudes was attained. For the fracture test, four kinds of notch direction were adopted : edgewise notches parallel (L) and transverse (T) to the major direction of fiber bundles, and flatwise notches parallel(ZL) and perpendicular(ZT) to this direction. Nominal bend strength for L and ZL specimens exhibited high sensitivity to notching. ZL specimens revealed the lowest values of the critical stress intensity factor $K_c$ which was slightly superior to those of unfilled PA6 matrix. Enlargement of the compression area for T specimens was analyzed by means of the rigidity reduction resulting from the fracture occurrence.

• Journal of Mechanical Science and Technology
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• 제18권4호
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• pp.630-639
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• 2004

The Stewart platform manipulator is a closed-kinematics chain robot manipulator that is capable of providing high structural rigidity and positional accuracy. However, this is a complex and nonlinear system, so the control performance of the system is not so good. In this paper, a new robust motion control algorithm is proposed. The algorithm uses partial state feedback for a class of nonlinear systems with modeling uncertainties and external disturbances. The major contribution is the design of a robust observer for the state and the perturbation of the Stewart platform, which is combined with a variable structure controller (VSC). The combination of controller and observer provides the robust routine called sliding mode control with sliding perturbation observe. (SMCSPO). The optimal gains of SMCSPO, which is determined by nominal eigenvalues, are easily obtained by genetic algorithm. The proposed fitness function that evaluates the gain optimization is to put sliding function. The control performance of the proposed algorithm is evaluated by the simulation and experiment to apply to the Stewart platform. The results showed high accuracy and good performance.

• 경제분석
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• 제26권4호
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• pp.39-64
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• 2020

전형적인 경기변동모형의 경우 노동시간 선택 문제만을 고려하여 노동시장의 주요 거시 변수인 고용과 실업을 명시적으로 설명하지 못하는 어려움이 있다. 본 논문에서는 뉴 케인지안 유형의 가격 경직성 모형에 노동시장의 탐색 및 매칭 마찰을 도입하고 이를 베이지안 방법으로 추정하여 우리나라 고용 및 실업의 움직임을 전체 경기변동의 움직임에 비추어 살펴보았다. 추정 결과 우리나라 실업률은 노동공급 충격과 더불어 노동수요 측면인 기술충격에 의하여 많은 부분 설명되는 것으로 나타났다. 아울러 노동시장 변동에서 기업과 노동자 간의 임금 협상에서 기인하는 협상력 충격도 상당 부분 중요한 것으로 나타났는데 협상력 충격은 경기 및 고용에 부정적인 영향을 미치므로 이에 대하여 주의를 기울일 필요가 있다.

• 국제초고층학회논문집
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• 제6권3호
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• pp.249-259
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• 2017

The use of high-strength steels in construction of highrise and mega building structures can bring about many technological advantages from fabrication to erection. However, key design criteria such as local and lateral stability in current steel design specifications were developed based on tests of ordinary steels which have stress-strain characteristics very different from that of high strength steels. A series of tests on 800 MPa tensile strength steel (HSA800) members are summarized in this paper which were conducted to investigate the appropriateness of extrapolating current ordinary-steel based design criteria to high strength steels. 800 MPa I-shape beam specimens designed according to flange local buckling (FLB) criteria of the AISC Specification developed a sufficient strength for elastic design and a marginal rotation capacity for plastic design. It is shown that, without introducing distinct and significant yield plateau to the stress-strain property of high-strength steel, it is inherently difficult to achieve a high rotation capacity even if all the current stability limits are met. 800 MPa I-shape beam specimens with both low and high warping rigidity exhibited sufficient lateral torsional buckling (LTB) strength. HSA800 short-column specimens with various edge restraint exhibited sufficient local buckling strength under uniform compression and generally outperformed ordinary steel specimens. The experimental P-M strength was much higher than the AISC nominal P-M strength. The measured residual stresses indicated that the impact of residual stress on inelastic buckling of high-strength steel is less. Cyclic seismic test results showed that HSA800 members have the potential to be used as non-ductile members or members with limited ductility demand in seismic load resisting systems. Finally, recent applications of 800 MPa high strength steel to highrise and mega building structures in Korea are briefly presented.