• 국제초고층학회논문집
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• 제2권4호
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• pp.355-365
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• 2013

The paper reports results of recent studies on the effects of column support conditions on the lateral displacements of moment frames at incipient collapse. The article presents a number of exercises in the plastic theory of structures that lead to useful design formulae. It has been shown that Drift Shifting (DS) is caused due to differences in the stiffnesses of adjoining columns, and that changes in drift ratios are more pronounced at first level column joints in both fixed as well as pinned base frames. In well proportioned moment frames, DS in the upper levels could be minimized, even reduced to zero. It has been demonstrated that DS can be eliminated in properly designed fixed and grade beam supported (GBS) moment frames. Several examples, including symbolic P-delta effects, have been provided to demonstrate the validity and the applications of the proposed ideas to the design and drift control of moment frames. The proposed methodology is exact within the bounds of the theoretical assumptions and is well suited for preliminary design and teaching purposes.

• Structural Engineering and Mechanics
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• 제64권3호
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• pp.301-310
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• 2017

For further development of passive control systems to dissipate larger seismic energy and prevent the structures from earthquake losses, this paper proposes an innovative two-level control system to improve behavior of chevron braced steel frames. Combining two Knee Braces, KB, and a Vertical Link Beam, VLB, in a chevron braced frame, this system can reliably sustain main shock and aftershocks in steel structures. The performance of this two-level system is examined through a finite element analysis and quasi-static cyclic loading test. The cyclic performances of VLB and KBs alone in chevron braced frames are compared with that of the presented two-level control system. The results show appropriate performance of the proposed system in terms of ductility and energy dissipation in two different excitation levels. The maximum load capacity of the presented system is about 30% and 17% higher than those of the chevron braced frames with KB and VLB alone, respectively. In addition, the maximum energy dissipation of the proposed system is about 78% and 150% higher than those of chevron braced frames with VLB and KB respectively under two separate levels of lateral forces caused by different probable seismic excitations. Finally, high performance under different earthquake levels with competitive cost and quick installation work for the control system can be found as main advantages of the presented system.

• Architectural research
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• 제2권1호
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• pp.61-69
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• 2000

This research focused on the hysteretic energy performance of 12 steel moment-resisting frames, which were intentionally designed by three types of design philosophies, strength control design, strength and drift control design, and strong-column and weak-beam control design. The energy performances of three designs were discussed In view of strength increase effect, stiffness increase effect, and strong-column and weak-beam effects. The mean hysteretic energy of the 12 basic systems were statically processed and compared to that of single-degree-of-freedom systems. Hysteretic energy was not always increased with an increase of strength and stiffness in the steel moment-resisting frames. Hysteretic energy between strong-column and weak-beam design and drift control design with the same stiffness was not sensitive each other for these types of mid-rises of steel moment-resisting frames.

• 한국강구조학회 논문집
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• 제12권4호통권47호
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• pp.397-406
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• 2000

본 연구는 수평하중을 받는 고층철골가새골조의 횡변위를 정량적으로 제어하는 효율적인 최적화 기법을 제시한다. 이를 위해 철골가새골조의 거동특성에 근거한 변위 민감도를 구성하고 수학적계획법의 일반성을 유지하면서 규모가 큰 문제도 효율적으로 다를 수 있는 근사화 개념이 도입된다. 아울러 단면 재선정시 상용화된 표준철골단면을 이용하는 이산형 최적화 방안도 고려한다. 제시된 기법의 효율성을 검토하기 위해 세 가지 종류의 12층 철골가새골조와 30층의 가새보강된 철골조 모델이 고려된다.

• 재활복지공학회논문지
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• 제5권1호
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• pp.17-25
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• 2011

본 논문은 전동 보행보조기의 편의성 향상을 위한 최적의 제어 이득을 찾고 제어 알고리즘을 설계하였다. 최근 노인의 인구가 의료 기술의 발달로 급속히 증가되고 있으며, 다양한 이동형 보행보조기구는 삶의 질을 개선하기 위해 개발되고 있다. 이러한 이동형 제품 중 수동형 보행보조기는 노인의 보행의 힘을 도와주는 전동모터를 가지고 있지 않아 노인들이 충분한 근력이 없기 때문에 경사로 및 문의 문턱 등 고르지 않는 지형에서 이동하는데 제안사항이 있다. 이러한 상황을 극복하기 위해 전동타입의 보행보조기를 개발하였다. 전동형 보행보조기는 수동형과 다르게 사용자가 조작을 해야 모터가 구동되는 구조이다. 이러한 구조는 사용자가 조작을 잘못 하였을 경우 상당한 불편함을 사용자에게 준다. 이러한 전동형 보행보조기를 수동형 보행보조기와 비교하여 조작의 편의성을 판단하고 기준을 만들어 사용자의 편의성에 대하여 제어 값을 변경하면서 사용자 편의성을 개선하였다. 본 논문에서는 보행의지를 인식하고 편의성의 성능을 측정할 수 있는 방법인 햅틱 센서를 소개하며 편의를 개선하는 제어 알고리즘을 제안한다. 또한 편의성의 평가는 COV(Center of Vehicle)와 사용자의 COP(Center of Position)과의 차이의 변화를 통해 상대적인 편의성을 평가하였다. 전동 타입 보행보조기와 새로운 측정방법을 도입하여 모든 과정을 실험을 통하여 확인 하였다.

• Steel and Composite Structures
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• 제19권2호
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• pp.467-484
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• 2015

Seismic performances of dual steel moment-resisting frames with mixed use of rigid and semi-rigid connections were investigated to control of the base shear, story drifts and the ductility demand of the elements. To this end, nonlinear seismic responses of three groups of frames with three, eight and fifteen story were evaluated. These frames with rigid, semi-rigid and combined configuration of rigid and semi-rigid connections were analyzed under five earthquake records and their responses were compared in ultimate limit state of rigid frame. This study showed that in all frames, it could be found a state of semi-rigidity and connections configuration which behaved better than rigid frame, with consideration of the base shear and story drifts criterion. Finally, some criteria were suggested to locate the best place of the semi-rigid connections for improvement of the seismic performance of steel moment-resisting frames.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권4호
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• pp.1877-1891
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• 2016

In video coding, the goal of rate control (RC) is not only to avoid the undesirable fluctuation in bit allocation, but also to provide a good visual perception. In this paper, a novel frame-level rate control algorithm for High Efficiency Video Coding (HEVC) is proposed. Firstly a model that reveals the relationship between bit per pixel (bpp), the bitrate of the intra frame and the bitrate of the subsequent inter frames in a group of pictures (GOP) is established, based on which the target bitrate of the first intra frame is well estimated. Then a novel frame-level bit allocation algorithm is developed, which provides a robust bit balancing scheme between the intra frame and the inter frames in a GOP to achieve the visual quality smoothness throughout the whole sequence. Our experimental results show that when compared to the RC scheme for HEVC encoder HM-16.0, the proposed algorithm can produce reconstructed frames with more consistent objective video quality. In addition, the objective visual quality of the reconstructed frames can be improved with less bitrate.

• Steel and Composite Structures
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• 제52권6호
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• pp.657-662
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• 2024

In the present analysis, the buckling behavior of smart beams integrated into racket frames for enhancing player control was examined by numerical solutions and sinusoidal shear deformation theory. The smart beam under consideration is subjected to an external voltage in the thickness direction. The integration of this smart material into the structure of the racket should optimize performance, improving the racket's stability and responsiveness during play. In this, an accurate representation of complex shear effects is made by using a sinusoidal shear deformation theory, while the solution of the resulting governing equations is made by numerical methods. The critical buckling loads and the characteristics of deformation obtained through the analysis provide insight into some design parameters controlling and influencing stability. Obtained results are validated with other published works. The length and thickness of the beam, elastic medium, boundary condition, and influence of external voltages have been represented for buckling load in the structure. These results will help in designing smart racket frames using smart beams to provide more precision and control for the players in an intelligent way.

• Earthquakes and Structures
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• 제1권3호
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• pp.307-326
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• 2010

This paper is concerned with the optimal seismic design of added viscous dampers in yielding plane frames. The total added damping is minimized for allowable values of local performance indices under the excitation of an ensemble of ground motions in both regular and irregular structures. The local performance indices are taken as the maximal inter-story drift of each story and/or the normalized hysteretic energy dissipated at each of the plastic hinges. Gradients of the constraints with respect to the design variables (damping coefficients) are derived, via optimal control theory, to enable an efficient first order optimization scheme to be used for the solution of the problem. An example of a ten story three bay frame is presented. This example reveals the following 'fully stressed characteristics' of the optimal solution: damping is assigned only to stories for which the local performance index has reached the allowable value. This may enable the application of efficient and practical analysis/redesign type methods for the optimal design of viscous dampers in yielding plane frames.

• Steel and Composite Structures
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• 제4권5호
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• pp.403-418
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• 2004

Lateral sway is most likely to control the design of semi-rigid steel frames where the frame arrangements do not include any form of bracing. This paper investigates the sway behaviour of semi-rigid regular steel frames i.e., frames having the same arrangement of beam and column sections at all levels, and hence proposes some design charts for the prediction of sway that eliminate the need for doing any numerical modelling. Schueller's equation has also been modified to incorporate connection flexibility in addition to its original rigid frame considerations. All the proposed methods have been validated using results obtained from numerical analysis.