• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.647-650
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• 2003

Under sustained loads, the deformation of a structure gradually increase with time and eventually may be much greater than its instantaneous value, This inelastic and time-dependent deformation causes increase in deflection and curvature, redistribution of stress and internal action, In this paper, time-dependent analysis with creep and shrinkage of uncracked and cracked partially prestressed concrete flexural members is presented.

• Structural Engineering and Mechanics
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• 제61권3호
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• pp.317-323
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• 2017

This work presents a new strategy to model stress dependent relaxation process in large deformation. The strategy is relied on the fact that in some particular soft materials undergoing large deformation, e.g., elastomers, rubbers and soft tissues, the relaxation time depends strongly on stress levels. To simplify the viscoelastic model, we consider that the relaxation time is the function of previous elastic deviatoric stress state experienced by materials during loading. Using the General Maxwell Model (GMM), we simulate numerically conditions with the constant and the stress dependent relaxation time for uniaxial tension and compression loading. Hence, it can be shown that the proposed model herein not only can represent different relaxation time for different stress level but also maintain the capability of the GMM to model hysteresis phenomena.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.605-606
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• 2008

• 지질공학
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• 제18권2호
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• pp.207-214
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• 2008

점토함량에 따른 미고결 이암의 시간 의존적 변형을 비교하기 위해 측방변형이 구속된 상태에서의 일축압밀시험을 수행하였다. 미고결 이암의 변형은 응력의 증가에 따른 즉각적인 변형과 일정한 응력 하의 크리프 변형으로 구분되었다. 응력 증가분이 동일한 경우에 시간 의존적 변형은 거의 일정한 크기로 발생하였으며 응력 증가분이 증가할수록 크리프변형의 크기도 증가하여 선형점성변형의 특성을 보였다. 점토함량이 증가함에 따라 시간 의존적 변형은 증가하는 경향을 보여 점토가 이암의 시간 의존적 변형 발생에 중요한 역할을 하는 것으로 사료된다. 크리프 변형은 시간에 따라 지수함수 형태를 보여 크립 모델 중 하나인 power-law 모델로 잘 예측될 수 있었다.

• 국제초고층학회논문집
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• 제6권1호
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• pp.83-89
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• 2017

Due to the time-dependent properties of materials, structures, and loads, accurate time-dependent effects analysis and precise construction controls are very significant for rational analysis and design and saving project cost. Elevation control is an important part of the time-dependent construction control in supertall structures. Since supertall structures have numerous floors, heavy loads, long construction times, demanding processes, and are typically located in the soft coastal soil areas, both the time-dependent features of superstructure and settlement are very obvious. By using the time-dependent coupling effect analysis method, this paper compares Shanghai Tower's vertical deformation calculation and elevation control scheme, considering foundation differential settlement. The results show that the foundation differential settlement cannot be ignored in vertical deformation calculations and elevation control for supertall structures. The impact of foundation differential settlement for elevation compensation and pre-adjustment length can be divided into direct and indirect effects. Meanwhile, in the engineering practice of elevation control for supertall structures, it is recommended to adopt the multi-level elevation control method with relative elevation control and design elevation control, without considering the overall settlement in the construction process.

• 한국지반공학회지:지반
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• 제5권2호
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• pp.57-77
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• 1989

본고는 팽장성 암석들의 시간의존적변형의 측정을 위한 실험장치와 실험고과에 관해서 설명한다. 새로운 실험장치들은 개선된 일축벽축하의 팽난시험, 일축 인장하의 인창시험과 이축 응력하의 팽 복시험을 위해서 제작하였다. 본 실험장치들은 암반파착시 지반에 작용하는 단순화된 헌력상태하에 있는 암반의 시간의존적 변형을 제 수직방향에서 측정한다. 지난 몇년간에 걸쳐서 얻은 실험결과에 의하면 본 실험장치들은 세공적으로 작동하는 것으로 나타났다. 실험결과로 보면, 퀸스톤 체일(Queenston shale)의 자유변형조건하에서의 시간의존적 변형 거동은 층리면과 수직인 방향에서는 층리면과 평행인 방향에서보다 약간 더 많은 역접이 일어나는 이방성적 거동을 보인다. 한 방향에 응력을 받을 때에는 응력이 작용하는 방향은 물론 그와 수직되는 방향의 역장성변형이 억제된다.

• International Journal of Concrete Structures and Materials
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• 제18권3E호
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• pp.161-164
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• 2006

Cellulose fiber reinforced cement(CFRC) pipe has been gradually introduced in the pipe market as a replacement of previously popular asbestos cement pipes. Since CFRC pipe is still relatively unknown in the pipe market, there are great concerns for the design and application in practice related to the time-dependent behavior of CFRC under long-term sustained loading. This paper presents an experimental investigation of the time-dependent behavior of cellulose fiber reinforced cement(CFRC) pipe. A total of six CFRC pipes were tested under various loading levels, and their vertical deformation was recorded to understand the characteristics of the time-dependent behavior. Based on the test results, a factor of safety(FS) of 1.82 is proposed, and a regression factor(R) of 1.88 is estimated for the application of CFRC pipes in practice.

• 한국건축시공학회지
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• 제15권5호
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• pp.457-464
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• 2015

지속적으로 증가하고 있는 이산화탄소 배출량을 저감시키기 위한 국제사회의 노력과 더불어 건설업계, 특히 시멘트 산업에서 알칼리 활성화제를 첨가한 알칼리 활성 슬래그를 활용하고자 하는 연구가 다수 수행되고 있다. 연구결과로 알칼리 활성 슬래그 모르타르의 고강도화 가능성이 밝혀지면서 초고층 구조물에 대한 적용가능성이 검토되고 있다. 그러나 초고층 구조물의 부재로 사용되기 위해서는 시간의 존 변형 거동에 관한 연구가 중요함에도 불구하고 굉장히 미흡한 실정이다. 따라서 본 연구에서는 OPC와 AAS를 이용한 콘크리트 시험체를 제작하여 크리프와 건조수축을 측정하고 도출된 결과값을 ACI 209R-92, CEB-FIP(1990)의 예측모델을 이용한 비선형 회귀분석을 통해 시간의존 변형 특성을 분석하였다. 각각의 열분석 및 SEM촬영을 통해 변형 발생 메카니즘을 규명하고자 하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.5-8
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• 2006

In this study, various fundamental experiments including durability and time-dependent deformation are performed to compile a database for a utilization of high-strength concrete for PSC bridges. In the mix design, concrete strength at early age when prestressing forces are introduced to the PSC member and slumpflow suitable for pumping of concrete are considered to make a concrete fit for PSC bridges. The main parameters investigated are the kinds and replacement ratios of mineral admixtures and low-heat cement. Experimental tests on durability include penetration of chloride ions, freezing-thawing, combined deterioration, and simple adiabatic temperature rise test. In addition, time-dependent deformation such as creep, drying and autogenous shrinkage, which is particularly important factor in the design and construction of PSC bridges, is tested and analyzed.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1990년도 PROCEEDINGS OF THE FIRST KOREA-JAPAN JOINT GEOTECHNICAL SEMINAR ON EXCAVATION and TUNNELING IN URBAN AREAS
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• pp.35-50
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• 1990

This paper describes the importance of incorporating the titre-dependent deformation behaviour in the design and construction of tunnels in swelling rocks. Two tunnel projects, in which authors got involved in Canada, are chosen to demonstrate the importance. In diversion tunnels for Oldman River Dan Projects time-dependent deformation characteristics of the mudrocks obtained from teat tunnel program were neglected in the design and construction of the tunnels and several sectional of concrete lining in tunnels were cracked extensively. In SABNGS No.3 Projects an extensive experimental program was carried out to study time-dependent deformation behaviour of highly swelling Queenston shale, with the air of establishing the constitutional relationship for the rock-structure time interaction analysis.