• 한국구조물진단유지관리공학회 논문집
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• 제24권5호
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• pp.17-26
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• 2020

이 연구에서는 조적벽체의 내진보강을 위하여 프리스트레스트 강봉 및 유리섬유 망을 이용하여 개발된 비부착 공법의 구조적 효율성을 평가하였다. 주요 실험변수는 강봉 및 유리섬유 망의 개별 보강과 강봉과 유리섬유 망의 복합 보강이다. 실험결과 제안된 보강공법은 조적벽의 내력, 강성 및 연성향상에 효율적이었다. 보강되지 않은 조적벽의 횡하중 내력, 최대내력 이전의 강성 및 에너지소산 능력과 비교할 때, 유리섬유 망으로 보강된 벽체에서의 그 증가비는 각각 110%, 120% 및 360%이며, 프리스트레스트 강봉으로 보강된 벽체에서의 그 증가비는 각각 140%, 130% 및 510%이며, 유리섬유 망과 강봉으로 보강된 벽체에서의 그 증가비는 각각 160%, 130% 및 840%이었다. 제시된 기술로 보강된 조적벽의 횡하중 내력은 Yang et al.의 제안식을 이용한 예측값과 비교적 잘 일치하였다. 즉, 제안된 기술은 조적벽체의 내진보강을 위한 적용성으로서 구조적 잠재력이 높았다.

• Structural Engineering and Mechanics
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• 제48권4호
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• pp.479-500
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• 2013

This paper presents the experimental as well as analytical study conducted on layer-bonded scrap tire rubber pad (STRP) isolators to develop low-cost seismic isolators applicable to structures in developing countries. The STRP specimen samples were produced by stacking the STRP layers one on top of another with the application of adhesive. In unbonded application, the STRP bearings were placed between the substructure and superstructure without fastening between the contact surfaces which allows roll-off of the contact supports. The vertical compression and horizontal shear tests were conducted with varying axial loads. These results were used to compute the different mechanical properties of the STRP isolators including vertical stiffness, horizontal effective stiffness, average horizontal stiffness and effective damping ratios. The load-displacement relationships of STRP isolators obtained by experimental and finite element analysis results were found to be in close agreement. The tested STRP samples show energy dissipation capacity considerably greater than the natural rubber bearings. The layer-bonded STRP isolators serve positive incremental force resisting capacity up to the shear strain level of 150%.

• Earthquakes and Structures
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• 제10권2호
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• pp.409-428
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• 2016

To realise the full benefits of a self-centering seismic resilient system, the designer must ensure that the entire structure does indeed re-center following an earthquake. The idealised flag-shaped hysteresis response that is often used to define the cyclic behaviour of self-centering concrete systems seldom exists and the residual drift of a building subjected to an earthquake is dependent on the realistic cyclic hysteresis response as well as the dynamic loading history. Current methods that are used to ensure that re-centering is achieved during the design of self-centering concrete systems are presented, and a series of cyclic analyses are used to demonstrate the flaws in these current procedures, even when idealised hysteresis models were used. Furthermore, results are presented for 350 time-history analyses that were performed to investigate the expected residual drift of an example self-centering concrete wall system during an earthquake. Based upon the results of these time-history analyses it was concluded that due to dynamic shake-down the residual drifts at the conclusion of the ground motion were significantly less than the maximum possible residual drifts that were observed from the cyclic hysteresis response, and were below acceptable residual drift performance limits established for seismic resilient structures. To estimate the effect of the dynamic shakedown, a residual drift ratio was defined that can be implemented during the design process to ensure that residual drift performance targets are achieved for self-centering concrete wall systems.

• 콘크리트학회지
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• 제9권5호
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• pp.105-114
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• 1997

본 연구는 비부착 긴장재를 갖는 부재에 대한 일련의 연구중 두 번째에 해당한다. 첫 번째 연구(1)에서는 기존연구의 제안식과 현행의 ACI 규준의 문제점을 고찰하고 기존의 총 167개 실험결과와 비교·분석하였다. 본 연구에서는 소성힌지 길이 개념과 변형도 적합조건에 의해서 비부착 긴장재의 응력을 평가할 수 있는 방법에 대한 검토를 통하여, 새로운 설계식을 제안하였다. 이는 이론적인 분석에 의한 변수설정과 기존 실험결과를 이용한 중회귀분석법을 사용하였다. 그리고 제안된 설계식을 기존의 식들과 비교하여 좋은 결과를 얻었으며, 제안된 설계식의 특성을 다음과 같이 설명하였다. (1)비부착 긴장재의 응력산정시 유효프리스트레스, 일반철근의 양, 작용하중의 형태 등은 중요한 변수로 작용할 수 있으므로 설계식에 고려하는 것이 바람직하다. (2)비부착 긴장재의 응력산정식은 현행 ACI 규준식과는 다르게 fc'/ p항의 제곱근과 비례하는 함수관계에 있다. (3)스팬-춤비가 비부착 긴장재의 응력에 미치는 영향은 소성힌지 길이의 개념에 의해서 역학적으로 타당하게 설명할 수 ldT다.

• 한국지진공학회논문집
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• 제13권2호
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• pp.15-27
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• 2009

이 연구는 지진하중을 받는 프리캐스트 세그먼트 PSC 교각의 지진거동을 파악하는데 그 목적이 있다. 사용된 프로그램은 철근콘크리트 구조물의 해석을 위한 RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology)이다. 사용된 부착 또는 비부착 텐던요소는 유한요소법에 근거하며 프리스트레스트 콘크리트 부재의 콘크리트와 텐던의 상호작용을 구현할 수 있다. 그리고 수정된 접합요소는 세그먼트 접합부의 비탄성거동을 예측할 수 있다. 동적 평형방정식의 해는 HHT(Hilber-Hughes-Taylor) 법에 의한 수치적분으로 구하였다. 제안된 해석기법은 수치예제에 대하여 입력지진파에 따른 지진거동을 비교적 정확하게 예측하였다.

• Computers and Concrete
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• 제13권1호
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• pp.1-16
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• 2014

To evaluate the behavior of the advanced unbonded pre-stressed concrete containment vessel (UPCCV) for one typical China nuclear power plant under Japan's March 11 earthquake, five nonlinear time history analysis and a nonlinear static analysis of a 1:10 scale UPCCV structure have been carried out with MSC.MARC finite element program. Comparisons between the analytical and experimental results demonstrated that the developed finite element model can predict the earthquake behavior of the UPCCV with fair accuracy. The responses of the 1:10 scale UPCCV subjected to the 11 March 2011 Japan earthquakes recorded at the MYG003 station with the peak ground acceleration (PGA) of 781 gal and at the MYG013 station with the PGA of 982 gal were predicted by the dynamic analysis. Finally, a static analysis was performed to seek the ultimate load carrying capacity for the 1:10 scale UPCCV.

• 한국전산구조공학회논문집
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• 제23권2호
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• pp.235-243
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• 2010

본 논문에서는 원자로 격납건물의 3차원 해석을 수행할 수 있는 구조해석 시스템을 구축하여 제시하였다. 구조해석 시스템은 고성능 평판 및 쉘 유한요소를 요소 라이브러리로 추가하였고, 비부착식 텐던과 부착식 텐던의 거동을 정확하게 모사할 수 있는 모델링방법을 포함하고 있다. 이러한 기능을 프로그래밍하고 범용 구조해석프로그램 DIANA에 접목시켜 원자로 격납건물의 비선형해석은 물론이고 내압능력 평가가 가능하다. 본 논문에서 제안한 3차원 구조해석 시스템의 신뢰성을 확인하기 위해 중수로형 원자로 격납건물의 구조해석을 수행하여 다른 기관에서 수행한 축대칭 구조해석 결과와 비교분석하였다.

• Structural Engineering and Mechanics
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• 제67권3호
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• pp.255-265
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• 2018

The prestress force effect on the fundamental frequency and deflection shape of Prestressed Concrete I (PCI) beams was studied in this paper. Currently, due to the conflicts among existing theories, the analytical solution for properly considering the structural behavior of these prestressed members is not clear. A series of experiments were conducted on a large-scale PCI beam of high strength concrete with an eccentric straight unbonded tendon. Specifically, the simply supported PCI beam was subjected to free vibration and three-point bending tests with different prestress forces. Subsequently, the experimental data were compared with analytical results based on the Euler-Bernoulli beam theory. It was proved that the fundamental frequency of PCI beams is unaffected by the increasing applied prestress force, if the variation of the initial elastic modulus of concrete with time is considered. Vice versa, the relationship between the deflection shape and prestress force is well described by the magnification factor formula of the compression-softening theory assuming the secant elastic modulus.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.668-673
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• 1998

The specimen of current study has the same type with the 3-span slabs of Burns et al used in the study by Mojtahedi/Gamble, which laid a ground for the revision of the ACI318-77 code to the ACI 318-83 code. But those specimens was failed prematurely before it reached the ultimate strength which the specimen had. The reason is that bonded reinforcements were cut off where there is no need for the flexural reinforcement. As results. the slabs failed ultimately where the reinforcements was cut off. Thus, the tendon stresses of failure may have been much smaller than the values which culd reach if the bonded reinforcements were extended beyond the theoretical cut off points. On the based on the fact mentioned above. the specimens which had the same conditions as the specimens of Burns et al were used in the current study, but in which the reinforcements were distributed in a sequence for the reinforcements not to be cut anywhere in the 3-span. As a results, it was known that the current ACI code, revised by the result of Mojtahedi/Gamble's study, overestimated the effect of span/depth ratio on the members with high span/depth ratio. Thus it was concluded that the effect of span/depth ratio on the ultimate stress of unbonded tendon regulated by the current ACI code must be reconsidered and reevaluated.

• 한국해양공학회지
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• 제2권1호
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• pp.135-149
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• 1988

Friction welding has been shown to have significant economic and technical advantages. However, one of the major concerns in using friction welding is the reliability of the weld quality. No reliable nondestructive test method is available at present for detecting weld quality, particularly in a production environment. Friction welds are formed by the mechanisms of diffusion as well as mechanical interlocking. The severe plastic flow at the interface by forge action of the process brings the subsurfaces so close together that detection of any unbonded area becomes very difficult. This paper presents an attempt to determine the friction weld strength quantitatively using the ultrasonic pulse-echo method. Instead of detecting flaws or cracks at the interface, the new approach calculates the coefficient of reflection based on measured amplitudes of the echoes. It has been finally confirmed that this coefficient could provide the quantitative relationship to the weld quality such as tensile strength, torsional strength, impact value, hardness, etc. So a new nondestructive analysis system of friction weld strength of dissimilar metals using an ultrasonic technique could be well developed.