• 한국구조물진단유지관리공학회 논문집
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• 제27권1호
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• pp.86-94
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• 2023

본 연구에서는 강재 슬릿댐퍼를 대상으로 하여 면외 변형을 구속할 수 있는 보완상세를 제시하고, 제안상세 적용 유무와 댐퍼의 형상비를 변수로 하여 일정진폭 가력실험을 수행하였다. 실험결과에 따라 제안상세가 적용된 슬릿댐퍼의 반복이력은 설정된 변수 범위에서 모두 안정적인 방추형의 이력거동을 나타내었으며 종국거동까지 댐퍼의 면외변형은 관찰되지 않았다. 누적변형각 분석을 통해 제안상세가 적용된 댐퍼 시스템은 대조군에 비해 월등히 큰 소성변형능력을 확보할 수 있음을 확인하였다. 이러한 구조적 효과(구속패널효과)는 슬릿댐퍼의 형상비가 작을수록 크게 나타났다. 관련 국외기준을 참고하여 제안상세 적용유무에 따른 슬릿댐퍼의 피로곡선을 작성하고 예측곡선 제시를 위한 매개변수를 도출하였다. 본 연구의 결과를 토대로 향 후 다양한 종류의 제진장치의 구조성능에 대한 정량적인 비교가 가능할 것으로 판단된다.

• Elastomers and Composites
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• 제54권4호
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• pp.299-307
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• 2019

Rubber friction properties include adhesion friction characteristics of the interface, hysteresis friction characteristics originating from repeated rubber deformations, and cohesion friction characteristics due to wear and tear. Cohesion friction is generally sufficiently small (< 3%) that it can be ignored, whereas adhesion friction has a relatively large contribution of 15%, but has not been investigated thoroughly. Therefore, through an adhesion friction study, the adhesion mechanism was examined and the relationship between friction characteristics and adhesion friction on dry surfaces was derived. The wet grip characteristics of tread rubber are fully described by the hysteresis characteristics of tires, but friction characteristics on dry roads are difficult to determine without adhesion factors. The results presented herein demonstrate that the combination of hysteresis and adhesion properties in the tread rubber sufficiently explained the characteristics of the dry grip. Based on the results of this study, technologies will be developed to determine the key factors governing adhesion friction characteristics and improve dry tire braking performance.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2005년도 동계학술연구발표회 및 2차 아시안포럼
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• pp.80-81
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• 2005

The resilience of the exchange bias ($H_{EX}$) in ferromagnet / antiferromagnet bilayers is generally studied in terms of repeated hysteresis loop cycling or by protracted annealing under reversed field (training and long-term relaxation respectively). The stability of $H_{EX}$ is fundamental for practical application of exchange bias systems. In this paper we report measurements of training and relaxation in FeNi films coupled with the antiferromagnet FeMn. We show that $H_{EX}$ suppressed both by training and relaxation was partially recovered as soon as a field cycling for consecutive hysteresis loop measurement was stopped or the magnetization of the ferromagnet was switched back to the biased direction.

• 한국터널지하공간학회 논문집
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• 제12권5호
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• pp.399-405
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• 2010

동결융해과정이 지속적으로 반복되면서 발생되는 응력이력현상으로 인해 암반내의 피로현상이 누적되면서 암반내 누적 변위가 증가할 뿐 아니라 강도 역시 지속적으로 감소된다. 동결융해로 인한 응력의 hysteresis 현상은 대기온도의 영향에 의한 것으로, 일반적으로 점탄성 거동을 하게 된다. 그러므로, 이상물체를 이용한 암반해석을 위해, 일반적으로 점탄성 거동해석에 사용되는 Kelvin 모델을 적용할 수 있다. 또한 다공질암의 동결융해에 따른 열화 과정을 정량적으로 파악하기 위한 새로운 지표를 설정하고자 동결-융해 실험을 실시하였다. 본 연구에서는 다공성 응회암을 이용 동결-융해 실험을 실시 암석의 열화과정의 분석을 시도하였다. 실내실험 결과, 공극률의 변화를 정량화하여 열화특성을 설명하였다. 탄성계수 및 일축압축강도 등 암석의 물성변화를 공극률을 이용 열화 특성 함수로써 표현하였다.

• 대한건축학회논문집:구조계
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• 제34권1호
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• pp.33-39
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• 2018

This study performed experimental validation of the hysteretic steel slit damper's basic and dependent characteristics, which should be considered for the design. The basic characteristic of the steel slit damper is used for determining design properties of non-linear analysis, such as yielding strength, yielding displacement, elastic stiffness and post-yielding stiffness. In order to evaluate dependent characteristics of the hysteretic steel slit damper, repeated deformation capacity with respect to the displacement, velocity and aspect ratio of the damper was evaluated. In this study, steel slit damper, which is widely used in Korea, was considered. The slit dampers with 55kN and 240kN of yielding strength were produced and tested. It was concluded that the slit damper's hysteresis behavior was affected by the dependent characteristics: displacement, velocity and aspect ratio. In other words, the steel slit damper's behavior was stable within limit displacement, and aspect ratio of the strut affected repeated deformation capacity of the damper subjected to large deformation. In addition, it was observed that the repeated deformation capacity abruptly decreased at the high speed range (${\geq}60mm/sec$). Furthermore, the experimental results were evaluated with the criterion of the damping device specified in ASCE7-10.

• Structural Engineering and Mechanics
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• 제84권5호
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• pp.699-706
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• 2022

Settlement control techniques are critical for the safety of shield tunnel constructions, especially for facing complex situations. In this study, the shield tunnel structure from Huaita east road station to Heping Road station in Xuzhou metro No.3 line (China) is taken as engineering background, which has various complex problems of the upper-soft and lower-hard composite stratum conditions, twin curve shield tunnels, and underpass the foundation of the piled raft. The deformation characteristics of shield tunnelling passing through buildings are explored. Subsequently, comprehensive research methods of numerical simulation and field measurement are adopted to analyzing the effectiveness of settlement control by using the top grouting technique. The results show that the settlement of the buildings has obvious spatial characteristics, and the hysteresis effect can be obviously observed in soil deformation caused by shield construction. Meanwhile, the two shield constructions can cause repeated disturbances, reducing the soil deformation's hysteresis effect. Moreover, the shield tunnel's differential settlement is too large when a single line passes through, and the shield construction of the outer curve can cause more significant disturbance in the tunnel than the inside curve. Notably, the proposed process control parameters and secondary topgrouting method can effectively control the deformation of the shield tunnel, especially for the long-term deformation.

• Structural Engineering and Mechanics
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• 제88권5호
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• pp.501-519
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• 2023

This paper introduces a new hybrid structural connection joint that combines shear walls with section steel beams, fundamentally resolving the construction complexity issue of requiring pre-embedded connectors in the connection between shear walls and steel beams. Initially, a quasi-static loading scheme with load-deformation dual control was employed to conduct low-cycle repeated loading experiments on five new connection joints. Data was acquired using displacement and strain gauges to compare the energy dissipation coefficients of each specimen. The destruction process of the new connection joints was meticulously observed and recorded, delineating it into three stages. Hysteresis curves and skeleton curves of the joint specimens were plotted based on experimental results, summarizing the energy dissipation performance of the joints. It's noteworthy that the addition of shear walls led to an approximate 17% increase in the energy dissipation coefficient. The energy dissipation coefficients of dog-bone-shaped connection joints with shear walls and cover plates reached 2.043 and 2.059, respectively, exhibiting the most comprehensive hysteresis curves. Additionally, the impact of laminated steel plates covering composite concrete floors on the stiffness of semi-rigid joint ends under excessive stretching should not be disregarded. A comparison with finite element analysis results yielded an error of merely 2.2%, offering substantial evidence for the wide-ranging application prospects of this innovative joint in seismic performance.

• 마이크로전자및패키징학회지
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• 제25권4호
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• pp.129-135
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• 2018

신축성 기판은 신축성 전자소자의 신축성, 공정성, 내구성을 결정하는 매우 중요한 소재로서 신축성 전자소자를 개발함에 있어서 우선적으로 고려해야 된다. 특히 현재 사용되는 신축성 기판은 히스테리시스가 존재하여 센서 및 기타 응용에 많은 어려움이 있다. 본 연구에서는 신축성 소재 기판으로 사용되는 PDMS와 Ecoflex를 혼합한 PDMS-Ecoflex 하이브리드 신축성 기판을 제작하여 신축성과 히스테리시스 특성을 향상하고자 하였다. 인장 시험을 통하여 신축성 하이브리드 기판의 기계적 거동을 관찰하였으며, 투과도 측정을 통하여 투과도를 평가하였다. Ecoflex의 함량이 증가할수록 하이브리드 신축성 기판은 더 유연해지며, 탄성계수는 감소한다. 또한 PDMS 기판은 270% 변형률에서 파단이 발생한 반면, PDMS-Ecoflex 하이브리드 기판은 500%의 변형률까지 파단되지 않으며 우수한 신축성을 갖는 것을 알 수 있었다. 반복 인장시험에서 PDMS와 Ecoflex의 혼합비를 2:1로 제작된 기판은 히스테리시스가 발생하였다. 반면 1:1의 혼합비로 제작된 기판의 경우 50%, 100%의 변형률에서는 히스테리시스가 발생하지 않았다. 결론적으로 500% 이상의 신축성을 갖으면서 히스테리시스가 없은 기판을 제작하였다. 기판의 혼합비에 따른 광투과도 측정 결과, Ecoflex 기판의 투과도는 68.6% 이였으나, PDMS-Ecoflex 함량이 2:1, 1:1인 하이브리드 기판의 경우, 각각 78.6%, 75.4%의 투과율을 보이며, 향후 투명 신축성 기판으로서 개발 가능성을 보여주었다.

• Earthquakes and Structures
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• 제9권5호
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• pp.957-981
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• 2015

Earthquakes occur as a cluster in many regions around the world where complex fault systems exist. The repeated shaking usually induces accumulative damage to affected structures. Damage accumulation in structural systems increases their level of degradation in stiffness and also reduces their strength. Many existing analytical tools of modeling RC structures lack the salient damage features that account for stiffness and strength degradation resulting from repeated earthquake loading. Therefore, these tools are inadequate to study the response of structures in regions prone to multiple earthquakes hazard. The objective of this paper is twofold: (a) develop a tool that contains appropriate damage features for the numerical analysis of RC structures subjected to more than one earthquake; and (b) conduct a parametric study that investigates the effects of multiple earthquakes on the response of RC moment resisting frame systems. For this purpose, macroscopic constitutive models of concrete and steel materials that contain the aforementioned damage features and are capable of accurately capturing materials degrading behavior, are selected and implemented into fiber-based finite element software. Furthermore, finite element models that utilize the implemented concrete and steel stress-strain hysteresis are developed. The models are then subjected to selected sets of earthquake sequences. The results presented in this study clearly indicate that the response of degrading structural systems is appreciably influenced by strong-motion sequences in a manner that cannot be predicted from simple analysis. It also confirms that the effects of multiple earthquakes on earthquake safety can be very considerable.

• International Journal of Concrete Structures and Materials
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• 제10권4호
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• pp.435-450
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• 2016

Experimental studies were conducted on 36 grouted splices to investigate their mechanical performance under four loading schemes: (1) incremental tensile loading, (2) repeated tensile loading, (3) cyclic loading at high stress, and (4) cyclic loading at large strain. Load-deformation responses of the grouted splices under cyclic loadings were featured with pinching effect and stiffness degradation compared to those responses under tensile loadings. The shape of the hysteresis loops of load-deformation curves was similar to that under incremental tensile loading. For the purpose of structural analysis, stress-strain relationships were presented for grouted splices under various loadings.