• Steel and Composite Structures
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• 제39권4호
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• pp.383-399
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• 2021

In the study, three 1:3-scale unequal span steel-concrete composite substructures with top-seat angle and double web angle connection were designed and identified as specimens GTSDWA-0.6, GTSDWA-1.0, and GTSDWA-1.4. Pseudo-static tests and refined numerical model analysis were conducted to examine the anti-progressive collapse performance of a semi-rigid steel-concrete composite substructure. The results indicated that the failure modes of the three specimens revealed that the fracture occurred in the root of the long leg of the top/seat angle in tension at the connection. With increases in the span ratio of the left and right composite beams, the bearing capacities of the composite substructures decreased, and the corresponding displacement increased. With respect to GTSDWA-0.6 and GTSDWA-1.4, the resistance due to the short composite beam corresponded to 62% and 60%, respectively, and the total resistance provided by the short composite beam exceeded that of the long composite beam. With respect to GTSDWA-1.0, the resistance due to the left and right composite beams was similar. All three specimens underwent the flexure mechanism and flexure-axial mixed mechanism stages. They resisted the external load mainly via the flexure mechanism. Moreover, the addition of stiffeners on both sides of the top and seat angles is advantageous in terms of improving the collapse resistance and ductility of unequal span composite substructures.

• 한국구조물진단유지관리공학회 논문집
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• 제24권6호
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• pp.59-66
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• 2020

축소모형 팔각형 기둥 실험체 2개를 제작하여 일정한 축력 하에서 반복 횡하중을 가력하는 실험을 수행하였다. 실험체는 중실단면과 중공단면이고 모든 실험체의 횡방향 나선철근 체적비는 0.00206의 값을 갖는다. 실험체들은 휨-전단 파괴거동을 보였다. 본 논문에서는 실험결과에 따른 파괴거동과 내진성능을 분석하였다. 실험결과, 중공 실험체는 초기강성, 초기 균열양상, 에너지 소산능력 등의 구조성능이 중실 실험체와 유사한 거동을 보였으나, 중공 실험체의 경우에는 3% 변위비 이후에 횡력, 극한변위, 에너지소산능력이 현저하게 감소되었다.

• 한국정밀공학회지
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• 제26권7호
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• pp.127-133
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• 2009

We present a $3-{\underline{P}}RS$ compliant parallel manipulator actuated by PZTs. The motion ranges are $400-{\mu}m$ translation to the z-direction and 5.7-mrad rotation about any axis on the x-y plane. A mechanical amplifier whose advantage is approximately 5.5 is designed and integrated with flexure revolute and spherical joints in a monolithic way. We evaluated the performance of the system: kinematic and dynamic characteristics. In kinematic point of view, the flexures play the roles of conventional mechanism but any nonlinearity such as dead-zone and backlash, which make it possible to achieve the steady-state resolution less than $0.1{\mu}m$. The system shows resonance near 86 Hz with high magnitude and, therefore, poor transient response. But the settling is faster when the flexures are strained higher.

• Steel and Composite Structures
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• 제26권4호
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• pp.407-420
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• 2018

Experiments were performed to explore the hysteretic performance of steel reinforced concrete (SRC) cross-shaped columns. Nine specimens were designed and tested under the combined action of compression, flexure, shear and torsion. Torsion-bending ratio (i.e., 0, 0.14, 0.21) and steel forms (i.e., Solid - web steel, T - shaped steel, Channel steel) were considered in the test. Both failure processes and modes were obtained during the whole loading procedure. Based on experimental data, seismic indexes, such as bearing capacity, ductility and energy dissipation were investigated in detail. Experimental results suggest that depending on the torsion-bending ratio, failure modes of SRC cross-shaped columns are bending failure, flexure-torsion failure and torsion-shear failure. Shear - displacement hysteretic loops are fuller than torque - twist angle hysteretic curves. SRC cross-shaped columns exhibit good ductility and deformation capacity. In the range of test parameters, the existence of torque does not reduce the shear force but it reduces the displacement and bending energy dissipation capacity. What is more, the bending energy dissipation capacity increases with the rising of displacement level, while the torsion energy dissipation capacity decreases.

• 한국생산제조학회지
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• 제20권6호
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• pp.756-760
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• 2011

This paper proposed an alignment stage driven by piezo actuators for alignment process of a contact-type lithography. Among contact-type lithography processes, an UV-curable nanoimprint process is an unique process to be able to align patterns on upper and lower layers. An alignment stage of the UV-curable nanoimprint process requires nano-level resolution as well as high stiffness to overcome friction force due to contact moving. In this paper, the alignment stage consists of a compliant mechanism using flexure hinges, piezo actuators for high force generation, and capacitive sensors for high-resolution measurement. The compliant mechanism is implemented by four prismatic-prismatic compliant chains for two degree-of-freedom translations. The compliant mechanism is composed of flexure hinges with high stiffness, and it is directly actuated by the piezo actuators which increases the stiffness of the mechanism, also. The performance of the ultra-precision stage is demonstrated by experiments.

• Earthquakes and Structures
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• 제16권1호
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• pp.41-54
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• 2019

Reinforced Concrete (RC) shear walls are widely used in Nuclear power plants as effective lateral force resisting elements of the structure and these may experience nonlinear behavior for higher earthquake demand. Short shear walls of aspect ratio less than 1.5 generally experience combined shear flexure interaction. This paper presents the results of the displacement-controlled experiments performed on six RC short shear walls with varying aspect ratios (1, 1.25 and 1.5) for monotonic and reversed quasi-static cyclic loading. Simulation of the shear walls is then carried out by Finite element modeling and also by macro modeling considering the coupled shear and flexure behaviour. The shear response is estimated by softened truss theory using the concrete model given by Vecchio and Collins (1994) with a modification in softening part of the model and flexure response is estimated using moment curvature relationship. The accuracy of modeling is validated by comparing the simulated response with experimental one. Moreover, based on the experimental work a multi-linear hysteretic model is proposed for short shear walls. Finally ultimate load, drift, ductility, stiffness reduction and failure pattern of the shear walls are studied in details and hysteretic energy dissipation along with damage index are evaluated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1860-1863
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• 1997

Transfer alignement is the process of initializing attitude of slave INS using the data of master INS. This paper presents the performance analysis of transfer alignment at sea using convariance analysis method. Velocity & angle matching and angular rate & acceleration matching are used for analysis, and the performance of two matching methods are compared. We propose a new method for angular rate & acceleration matching. Under the assumption of accurate modeling of ship flexure, the performance of transfer alignment time and accuray is improved very much for the new method.

• 한국강구조학회 논문집
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• 제21권4호
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• pp.403-411
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• 2009

본 연구에서는 1995년 고베 지진에 의해 손상을 입은 강 거더 교량에 대해 비선형 지진해석을 수행하였다. 해석수행을 위해 휨-축력 및 휨-전단-축력간의 상호작용을 모사할 수 있는 이력모델을 제안하였다. 제안된 이력모델은 힌지모델 형태로 구조해석 프로그램에 조인트 요소로 연결한 후, 힌지모델 사용한 간편한 해석기법을 교량 교각에 적용하였다. 휨-축력 상호작용을 고려한 해석결과는 상세한 화이버 요소 해석결과와 비교하였고, 좋은 상관관계를 나타내었다. 또한, 휨-축력-전단 상호작용을 고려한 해석결과는 지진하중을 받는 교각의 변위 요소별 검토가 가능하여 교각의 전체 변위성능 분석에 유용하게 사용할 수 있을 것으로 판단된다.

• 콘크리트학회논문집
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• 제21권4호
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• pp.523-530
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• 2009

콘크리트를 설계하기 위해 설계자는 설계의 효율성을 위하여 일축휨강도에 기초한 설계를 하고 있지만, 포 장체 및 바닥판과 같은 실제 구조요소의 응력상태는 재료전반에 작용하는 이축응력이 발생하게 된다. 따라서 콘크리트 의 이축휨시험은 사용하중상태에서 콘크리트의 거동을 평가할 수 있는 중요한 설계인자로서 사용될 수 있다. 이 연구 에서 저자들은 콘크리트 이축휨강도를 평가할 수 있는 BFT 시험법의 최적 구성을 제안하였다. 이 기법은 세라믹 또는 바이오 재료 분야에서 사용되어온 링온링 시험법을 콘크리트 재료에 적합하도록 수정, 제시한 것이다. 이를 위하여 유 한요소해석과 정밀해에 대한 분석을 통하여 시험체의 형상과 시험법을 제시하였다. 제안된 방법에 의한 실험 결과, 이 축휨실험을 통하여 콘크리트 재료의 휨강도를 충분히 판정할 수 있는 것을 증명할 수 있었다.

• 한국지진공학회논문집
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• 제10권2호
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• pp.1-10
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• 2006

형상비가 상대적으로 작은 철근콘크리트 교각에 지진작용으로 인한 반복 횡하중이 작용하면 초기단계와 중간단계의 변위에서는 휨 거동을 보이다가 최종변위단계에서는 전단에 의해 파괴되는 휨-전단 거동을 보인다. 휨-전단 파괴거동을 보이는 교각은 휨 파괴거동을 보이는 교각에 비하여 연성능력이 저하되므로, 내진설계 또는 내진성능평가에서 극한변위를 해석적으로 결정하기 위해서는 휨성능곡선과 함께 전단성능곡선 모델을 적용하여야 한다. 본 논문에서는 원형교각에 대한 기존 모델을 수정한 전단성능곡선 모델을 제안하였고, CALTRANS 모델, Aschheim등의 모델, Priestley 등의 모델, 제안모델의 특징을 비교하였다. 또 국내에서 수행된 실물크기 기둥 실험체를 대상으로 전단성능곡선 모델을 평가하였다. 제한된 범위의 소수 실험결과에 대한 적용으로서 일반화하기는 어려울 것이지만, 실험결과와 비교 검토한 결과 제안모델이 파괴형태의 예측과 변위성능 예측의 정확도에서 매우 우수한 것으로 평가되었다.