• 경영과학
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• 제14권2호
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• pp.69-79
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• 1997

The computational speed of interior point method of linear programming depends on the speed of Cholesky factorization. If the coefficient matrix A has dense columns then the matrix A.THETA. $A^{T}$ becomes a dense matrix. This causes Cholesky factorization to be slow. We study an efficient implementation method of the dense column splitting among dense column resolving technique and analyze the relation between dense column splitting and order methods to improve the sparsity of Cholesky factoror.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.329-332
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• 2002

A theoretical study is made of the steady flow of a compressible fluid in a rapidly rotating finite cylinder. Flow is generated by imposing mechanical and/or thermal disturbances at the rotating endwall disks. Both the Ekman and Rossby numbers are small. A detailed consideration is given to the energy budget for a control volume in the Ekman boundary layer. A combination of physical variables, which is termed the energy contents, consisting of temperature and modified angular momentum, emerges to be relevant. The distinguishing features of a compressible fluid, in contrast to those of an incompressible fluid, are noted. For the Taylor-Proudman column to be sustained, in the interior, it is shown that the net energy transport between the solid disk wall and the interior fluid should vanish. Physical rationalizations are facilitated by resorting to the concept of the afore-stated energy content.

• 콘크리트학회논문집
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• 제29권1호
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• pp.77-84
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• 2017

본 연구에서는 고강도 콘크리트 기둥-일반강도 콘크리트 슬래브 접합부의 구속도, 형상비 (h/c), 강도비 ($f^{\prime}_{cc}/f_{cs}$)에 따른 구조거동 분석하였다. 유한요소해석 프로그램을 통해 해석적 연구가 수행되었으며, 해석 방법의 검증을 위하여 기존의 구조 실험과 동일한 조건의 해석 부재를 제작하여 결과를 비교하였다. 부재의 종류는 내부기둥, 외부기둥, 모서리기둥, 독립기둥으로 분류하였으며 내부기둥에서 가장 높은 극한강도를 보였다. 또한 형상비가 증가할수록 접합부에 작용하는 축방향 응력이 작게 나타났으며 강도비가 증가할수록 부재의 극한강도가 상승하였으나 1.83이후로는 뚜렷한 강도 증진을 나타내지 않았다.

• Advances in concrete construction
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• 제9권3호
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• pp.313-326
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• 2020

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beam-column joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.

• 콘크리트학회논문집
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• 제24권6호
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• pp.753-760
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• 2012

이 연구에서는 고강도 철근콘크리트 내부 보-기둥 접합부의 시공성 및 내진성능을 개선하기 위하여 보-기둥 접합부 영역의 스터럽 및 띠철근 유무에 따라 고인성섬유 복합모르타르를 사용하여 내진성능을 평가하였다. 총 6개의 실험체를 제작하고 실험을 수행하여 내진성능을 평가하였으며, 이 연구의 실험 결과를 근거로 다음과 같은 결론을 얻었다. 기존 고강도 철근콘크리트 내부 보-기둥 접합부의 위험단면 영역을 고인성섬유 복합모르타르로 보강한 결과 재하 전 과정을 통하여 섬유의 가교역할로 인한 균열 분산효과로 인하여 균열 제어 효과가 커서 안정적인 파괴형태 및 내력을 나타내었다. 고강도 철근콘크리트 내부 보-기둥 접합부의 시공성 및 내진성능을 개선하기 위하여 고인성섬유 복합모르타르를 사용하여 보강한 실험체($IJNSP_{1.0}$, $IJNSP_{1.5}$, $IJNSP_{2.0}$)는 스터럽과 띠철근이 제거되었음에도 안정적인 이력거동을 나타내었고, 최대내력이 표준실험체의 96~102.8%, 에너지소산능력은 최대 0.99~1.11배로 표준실험체와 거의 비슷한 에너지소산능력을 나타내었다.

• 콘크리트학회논문집
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• 제25권2호
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• pp.233-240
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• 2013

이 연구에서는 고강도 철근콘크리트 내부 보-기둥 접합부의 내진성능을 개선하기 위하여 보-기둥 접합부 영역을 고성능 배근상세 및 고인성섬유 복합 모르타르를 사용하여 보강하고 내진성능을 평가하였다. 총 5개의 실험체를 제작하고 실험을 수행하여 내진성능을 평가하였으며, 이 연구의 실험 결과를 근거로 다음과 같은 결론을 얻었다. 기존 고강도 철근콘크리트 내부 보-기둥 접합부의 위험단면 영역을 고성능 배근상세 및 고인성섬유 복합 모르타르로 보강한 결과 재하 전 과정을 통하여 안정적인 파괴형태 및 내력을 나타내었다. 고강도 철근콘크리트 내부 보-기둥 접합부의 내진성능을 개선하기 위하여 고성능 배근상세 및 고인성섬유 복합 모르타르를 사용하여 보강한 실험체(IJIR, IJIRS, IJIRP)는 재하 전 과정을 통하여 안정적인 이력거동을 나타내었고, 최대내력이 표준실험체의 114.2~123.5%, 에너지소산능력은 1.55~1.85배로 표준실험체에 비하여 매우 향상되었다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 1996년도 추계학술대회발표논문집; 고려대학교, 서울; 26 Oct. 1996
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• pp.289-292
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• 1996

In Cholesky factorization of the interior point method, dense columns of A matrix make dense Cholesky factor L regardless of sparsity of A matrix. We introduce a method to transform a primal problem to a dual problem in order to preserve the sparsity.

• 한국국방경영분석학회지
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• 제24권1호
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• pp.146-156
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• 1998

Cholesky factorization is known to be inefficient to problems with dense column and network problems in interior point methods. We use the conjugate gradient method and preconditioners to improve the convergence rate of the conjugate gradient method. Several preconditioners were applied to LPABO 5.1 and the results were compared with those of CPLEX 3.0. The conjugate gradient method shows to be more efficient than Cholesky factorization to problems with dense columns and network problems. The incomplete Cholesky factorization preconditioner shows to be the most efficient among the preconditioners.

• Computers and Concrete
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• 제15권5호
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• pp.807-831
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• 2015

In the previous analytical studies on 2D reinforced concrete (RC) beam-column joints, the modified compression field theory (MCFT) and the strut-and-tie method (STM) are usually employed. In this paper, the limitations of these analytical models for RC joint applications are reviewed. Essentially for predictions of RC joint shear behaviour, the MCFT is not applicable, while the STM can only predict the ultimate shear strength. To eliminate these limitations, an improved STM is derived and applied to some commonly encountered 2D joints, viz., interior and exterior joints, subjected to monotonic loading. Compared with the other STMs, the most attracting novelty of the proposed improved STM is that all critical stages of the shear stress-strain relationships for RC joints can be predicted, which cover the stages characterized by concrete cracking, transverse reinforcement yielding and concrete strut crushing. For validation and demonstration of superiority, the shear stress-strain relationships of interior and exterior RC beam-column joints from published experimental studies are employed and compared with the predictions by the proposed improved STM and other widely-used analytical models, such as the MCFT and STM.

• 한국구조물진단유지관리공학회 논문집
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• 제6권1호
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• pp.213-221
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• 2002

This paper presents the experimental result of Reinforced Concrete column-steel beam joint connected by Band Plates(BP). Main parameters in the test are the shape of BP and thickness of plate. Ten interior and exterior RC column-steel beam joint specimens are designed. Cyclic loads are applied to the beam end of eight specimens (four interior specimens and four exterior specimens). To evaluate the cyclic effect, monotonic loads are acted for two specimens. All specimen showed similar failure pattern such as the plate of BP get torn after the large deformation. Even though the specimen with double cross type BP has lower strength than the specimen with single cross type BP, the energy dissipation capacity of the specimen turned out high. Thus, provided the strength of joint with double cross type to be designed to have suitable strength by increasing the thickness of plate, the joint system may show higher seismic capacity.