• Steel and Composite Structures
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• 제30권5호
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• pp.443-456
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• 2019

Although numerous researchers demonstrated the significant difference in performance between the various beam-to-column connection types, most of the previous studies in the area of infilled steel frames focused on the behaviour of frames with welded connections. Therefore, there is a need for conducting studies on infilled steel frames with other common connection types (extended endplate with and without rib stiffeners, flush endplate and shear connections). In this paper, firstly, a two-dimensional finite-element model simulating the cyclic response of infilled steel frames was presented. The infill-frame interaction, as well as the interactions between connections' components, were properly modelled. Using the previously-validated model, a parametric study on infilled steel frames with five different beam-to-column connection types, under cyclic loading, was carried out. Several parameters, including infill material, fracture energy of masonry and infill thickness, were investigated. The results showed that the infilled frames with welded connections had the highest initial stiffness and load-carrying capacity. However, the infilled frames with extended endplate connections (without rib stiffeners) showed the greatest energy dissipation capacity and about 96% of the load-carrying capacity of frames with welded connections which indicates that this type of connection could have the best performance among the studied connection types. Finally, a simplified analytical model for estimating the stiffness and strength of infilled steel frames (with different beam-to-column connection types) subjected to lateral cyclic loading, was suggested.

• 분석과 대안
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• 제5권2호
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• pp.39-76
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• 2021

本研究通过高层梯队理论和人力资本理论探究中国民营企业首席执行官的政治关系为企业所带来的影响。首席执行官的个人特征对企业的战略决策产生直接或间接的影响,同时可作为企业特有的优势,为企业的可持续发展发挥着人力资本的作用。对此,本研究通过实证探究中国民营企业的首席执行官所拥有的政治关系是否对企业的人力资本企业绩效产生积极影响。另外,本研究将政治关系的直接对象-- 中国地方政府分为不同阶层,考察政治关系的人力资本价值和影响力的差异,而且预测政府补贴可以在这一关系中起到中介的作用。为了验证这一论点,以2008年至2016年间在中国上海和深圳证券交易所上市的1,451个企业的共9,849个观测值为对象进行分析,结果确认首席执行官的政治关系对企业绩效产生正向(+)的影响。另外,从各阶层的地方政府来看,只有与作为最高层地方政府的省级地方政府有政治关系时,才能对企业绩效产生积极影响；同时,只有在首席执行官拥有的人力资本的价值和影响力与省级地方政府有关联时才能发挥上述的积极影响。另外,政府补贴的中介效应在与地级地方政府有政治关系时,会具备完全中介的属性,进而对企业经营成果产生积极影响。可以说,地方政府在政府补贴支付中起到核心作用,因此经营者的政治关系常被运用为企业的非市场战略。

• 분석과 대안
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• 제7권2호
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• pp.111-145
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• 2023

본 연구는 중국 상장기업의 정치적 연계(political connections)가 기업의 사회적 책임(Corporate Social Responsibility, CSR) 활동에 미치는 영향을 확인하고 있다. 기업은 정치적 연계를 '비시장 전략(non-market strategy)'으로 인지하여, 이를 통해 획득한 다양한 혜택을 경영 활동에 적극적으로 활용하고자 한다. 반면에 이러한 정치적 연계를 활용하고자 하는 기업은 그 혜택에 대한 대가로 정부의 사회 정책적인 의무를 수행해야 할 필요성이 제기된다. 특히, 중국 정부는 기업이 CSR 활동을 통하여 산재되어 있는 사회문제를 적극적으로 해소해주기를 원하고 있다. 이에 따라 정치적 연계를 통하여 정부로부터 경영상의 혜택을 획득하고자 하는 기업은 적극적인 CSR 활동을 통하여 정부의 요구를 수용하고 있다는 신호를 보낼 필요성이 제기된다. 이러한 환경에서 본 연구는 기업의 정치적 연계가 정부가 요구하는 CSR 활동을 수행하는 요인으로 작용하는지를 2013년부터 2019년까지 중국 전체 상장기업을 대상으로 실증적인 검증을 한다. 분석 결과, 중앙정부와 정치적 연계를 지닌 기업을 중심으로 CSR 활동에 긍정적인 영향을 주는 것을 보여준다. 또한, 이러한 관계에서 정부 보조금이 매개효과로 작용하면서, 중앙정부와 정치적 연계가 있는 기업은 정부로부터 혜택을 얻는 것과 동시에 정부의 사회 정책적인 의무를 모두 수행하고 있는 것을 의미한다.

• Earthquakes and Structures
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• 제24권2호
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• pp.81-90
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• 2023

The maximum drifts are important to the seismic evaluation of steel buildings and connections, but the information can hardly be obtained from the post-earthquake field investigation. This research studies the feasibility of using the loss rate of bolt pretension as an earthquake damage predictor. Full-scale tests were made on four steel connections using bolted-web-welded-flange details. One connection was unreinforced (UN), another was reinforced with double shear plates (DS), and the other two used reduced beam sections (RBS). The preinstalled strain gauges were used to control the pretensions and monitor the losses of the high-strength bolts. The results showed that the loss rate of bolt pretension was highly related to the damage of the connections. The pretensions lost up to 10% in all the connections at the yield drifts of 0.5% to 1%. After yielding of the connections, the pretensions lost significantly until fracture occurred. The UN and DS connections failed with a maximum drift of 4 %, and the two RBS connections showed better ductility and failed with a maximum drift of 6%. Under the far-field-type loading protocol, the loss rate grew to 60%. On the contrary, the rate for the specimen under near-fault-type loading protocol was about 40%. The loss rate of bolt pretension is therefore recommended to use as an earthquake damage predictor. Additionally, the 10% and 40% loss rates are recommended to predict the limit states of connection yielding and maximum strength, respectively, and to define the performance levels of serviceability and life-safety for the buildings.

• Steel and Composite Structures
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• 제46권6호
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• pp.773-791
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• 2023

Connections with damage concentrated to pre-selected components can enhance seismic resilience for moment resisting frames. These pre-selected components always yield early to dissipate energy, and their energy dissipation mechanisms vary from one to another, depending on their position in the connection, geometry configuration details, and mechanical characteristics. This paper presents behaviour insights on two types of beam-to-beam connections that the angles were designed as energy dissipation components, through the results of experimental study and finite element analysis. Firstly, an experimental programme was reviewed, and key responses concerning the working mechanism of the connections were presented, including strain distribution at the critical section, section force responses of essential components, and initial stiffness of test specimens. Subsequently, finite element models of three specimens were established to further interpret their behaviour and response that were not observable in the tests. The moment and shear force transfer paths of the composite connections were clarified through the test results and finite element analysis. It was observed that the bending moment is mainly resisted by axial forces from the components, and the dominant axial force is from the bottom angles; the shear force at the critical section is primarily taken by the slab and the components near the top flange. Lastly, based on the insights on the load transfer path of the composite connections, preliminary design recommendations are proposed. In particular, a resistance requirement, quantified by a moment capacity ratio, was placed on the connections. Design models and equations were also developed for predicting the yield moment resistance and the shear resistance of the connections. A flexible beam model was proposed to quantify the shear resistance of essential components.

• 한국학교수학회논문집
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• 제15권3호
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• pp.395-410
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• 2012

수학 교수학습 관련 자료를 개발하거나 수업을 계획할 때에는 지도 내용 간의 위계나 연계를 고려하여 내용이나 순서를 적절하게 변화시켜 재구성해야 한다. 또한 교사는 학생들이 수학적 개념을 독립적이고 단절적으로 이해하는 것이 아니라 관계적이고 반영적으로 이해할 수 있도록 지도해야 하며 이를 위한 철저한 준비가 필요하다. 이를 위하여 본 연구는 수학적 연결성에 대한 선행연구를 메타적으로 분석하여 외적 내적, 내용적 형식적으로 분류하였으며 수학 외적 연결성과 수학 내적 연결성이 형식적 측면에서 유사성과 비경계성이 존재함을 확인하고 이를 바탕으로 수학 내적 연결성에 관한 형식적 측면의 원리를 정의하고 구체적인 사례를 제시하였다.

• Steel and Composite Structures
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• 제18권6호
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• pp.1405-1421
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• 2015

Semi-rigid connections are the actual behavior of beam-to-column connections in steel frames. However, the behavior of semi-rigid connections is not taken into account for the simplicity in the conventional analysis and design of steel frames. A computer-based analysis and design has been studied for the three-dimensional steel frames with semi-rigid connections. The nonlinear analysis which includes the effects of the flexibility of connections is used for this study. It is designed according to the buckling and combined stress constraints under the present loading after the joint deformations and the member end forces of the space frame are determined by the stiffness matrix method. The semi-rigid connection type is limited to the top and bottom angles with a double web angle connection. The Frye-Morris polynomial model is used to describe the non-linear behavior of semi-rigid connections. Various design examples are presented to demonstrate the efficiency of the method. The results of design and analysis of unbraced semi-rigid frames are compared to the results of unbraced rigid frames under the same design requirements.

• Structural Engineering and Mechanics
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• 제64권1호
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• pp.109-120
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• 2017

The behavior of moment resistant steel structures depends on both the beam-column connections and columns foundations connections. Obviously, if the connections can meet the adequate ductility and resistance against lateral loads, the seismic capacity of these structures will be linked practically to the performance of these connections. The shape memory alloys (SMAs) have been most recently used as a means of energy dissipation in buildings. The main approach adopted by researchers in the use of such alloys is firstly bracing, and secondly connecting the beams to columns. Additionally, the behavior of these alloys is modeled in software applications rarely involving equivalent torsional springs and column-foundation connections. This paper attempts to introduce the shape memory alloys and their applications in steel structural connections, proposing a new steel column-foundation connection, not merely a theoretical model but practically a realistic and applicable model in structures. Moreover, it entails the same functionality as macro modeling software based on real behavior, which can use different materials to establish a connection between the columns and foundations. In this paper, the suggested steel column-foundation connection was introduced. Moreover, exploring the seismic dynamic behavior under cyclic loading protocols and the famous earthquake records with different materials such as steel and interconnection equipment by superelastic shape memory alloys have been investigated. Then, the results were compared to demonstrate that such connections are ideal against the seismic behavior and energy dissipation.

• Steel and Composite Structures
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• 제6권1호
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• pp.33-53
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• 2006

The rotational behaviour of bolted extended end plate beam-to-column connections is evaluated in the context of the component method. The full moment-rotation response is characterized from the force-deformation curve of the individual joint components. The deformability of end plate connections is mostly governed by the bending of the column flange and/or end plate and tension elongation of the bolts. These components form the tension zone of the joint that can be modelled by means of "equivalent T-stubs". A systematic analytical procedure for characterization of the monotonic force-deformation behaviour of individual T-stub connections is proposed. In the framework of the component method, the T-stub is then inserted in the joint spring model to generate the moment-rotation response of the joint. The procedures are validated with the results from an experimental investigation of eight statically loaded extended end plate bolted moment connections carried out at the Delft University of Technology. Because ductility is such an important property in terms of joint performance, particularly in the partial strength joint scenario, special attention is given to this issue.

• 한국지진공학회논문집
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• 제3권4호
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• pp.23-32
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• 1999

본 연구에서는 반복하중을 받는 H형강보 접합부의 거동을 실험적인 방법으로 조사하였다. 본 연구의 목적은 H형강보 접합부의 이력거동에 강제의 특성과 스캘럽의 형태가 주는 영향을 조사하는 것이다 5개의 접합부 시험체를 제작하여 반복하중을 재하면서 실험을 수행하였다. 보 접합부에서의 하중-회전변형 곡선을 얻었으며 접합부의 변형능력과 에너지 소산능력을 상호 비교하였다. 강재가 SS400인 시험제는 충분한 변형능력과 에너지소산능력을 보였으나 강재가 SM490인 시험체는 취성적인 파괴를 보였으며 변형능력이 작았다. 접합부 스캘럽의 형태는 접합부의 거동에 영향을 주지않았다.