• Title, Summary, Keyword: 프리스트레스

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Long-Term Prediction of Prestress in Concrete Bridge by Nonlinear Regression Analysis Method (비선형 회귀분석기법을 이용한 콘크리트 교량 프리스트레스의 장기 예측)

  • Yang, In-Hwan
    • Journal of the Korea Concrete Institute
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    • v.18 no.4
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    • pp.507-515
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    • 2006
  • The purpose of the paper is to propose a method to give a more accurate prediction of prestress changes in prestressed concrete(PSC) bridges. The statistical approach of the method is using the measurement data of the structural system to develop a nonlinear regression analysis. Long-term prediction of prestress is achieved using nonlinear regression analysis. The proposed method is applied to the prediction of prestress of an actual prestressed concrete box girder bridge. The present study represents that confidence interval of long-term prediction becomes progressively narrower with the increase of in-situ measurement data. Therefore, the numerical results prove that a more realistic long-term prediction of prestress changes in PSC structures can be achieved by employing the proposed method. The prediction results can be efficiently used to evaluate prestress during the service life of structure so that the remaining prestress exceeds the control criteria.

Determination Method for Longitudinal Initial Prestress in Composite Beams with Precast Decks I: Simply Supported Beams (프리캐스트 바닥판을 사용한 강합성보의 교축방향 초기 프리스트레스 산정방법 I : 단순보)

  • Cho, Sun-Kyu;Lee, Jong-Min
    • Journal of The Korean Society of Civil Engineers
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    • v.28 no.1A
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    • pp.15-24
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    • 2008
  • This paper presents the analytical method for the long-term behavior of simply supported composite beams with precast decks prestressed in the longitudinal direction. The objectives of time-dependent analysis are to estimate losses of prestress on the concrete slab and long-term deflection due to creep and shrinkage of concrete, relaxation of prestressing steel. Also, the time-dependent analysis was carried out using the presented analytical method to evaluate the effects of several parameters on the long-term behavior of composite bridge with precast deck, including geometrical shapes of composite beams, compressive strength of concrete and magnitude of initial prestress. The results of the analysis indicated that, in the effects of geometrical shapes of composite beams, the main parameters affecting the losses of prestress and the long-term deflection were the cross sectional area and the moment of inertia of steel beam, respectively. Finally, the determination method for the required initial prestress was proposed by evaluation of the loss characteristics due to shrinkage and creep of concrete.

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Efficient Modal Analysis of Prestressed Structures via Model Order Reduction (모델차수축소법을 이용한 프리스트레스 구조물의 효율적인 고유진동해석)

  • Han, Jeong-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.10
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    • pp.1211-1222
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    • 2011
  • It is necessary to use prestressed modal analysis to calculate the modal frequencies and mode shapes of a prestressed structure such as a spinning blade, a preloaded structure, or a thermally deformed pipe, because the prestress effect sometimes causes significant changes in the frequencies and mode shapes. When the finite element model under consideration has a very large number of degrees of freedom, repeated prestressed modal analyses for investigating the prestress effects might become too computationally expensive to finish within a reasonable design-process time. To alleviate these computational difficulties, a Krylov subspace-based model order reduction, which reduces the number of degrees of freedom of the original finite element model and speeds up the necessary prestressed modal analysis with the reduced order models (ROMs), is presented. The numerical process for the moment-matching model reduction is performed directly on the full order models (FOMs) (modeled in ANSYS) by the Arnoldi process. To demonstrate the advantages of this approach for performing prestressed modal analysis, the prestressed wheel and the compressor impeller under their high-speed rotation are considered as examples.

Uncertainty and Updating of Long-Term Prediction of Prestress in Prestressed Concrete Bridges (프리스트레스트 콘크리트 교량의 프리스트레스 장기 예측의 불확실성 및 업데이팅)

  • 양인환
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.17 no.3
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    • pp.251-259
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    • 2004
  • The prediction accuracy of prestress plays an important role in the quality of maintenance and the decision on rehabilitation of infrastructure such as prestressed concrete bridges. In this paper, the Bayesian statistical method that uses in-situ measurement data for reducing the uncertainties or updating long-term prediction of prestress is presented. For Bayesian analysis, prior probability distribution is developed to represent the uncertainties of creep and shrinkage of concrete and likelihood function is derived and used with data acquired in site. Posterior probability distribution is then obtained by combining prior distribution and likelihood function. The numerical results of this study indicate that more accurate long-term prediction of prestress forces due to creep and shrink age is possible.

Anchorage Zone Behavior and Analysis of Precast Prestressed Concrete Box-Girder Bridges (프리캐스트 프리스트레스트 콘크리트(PC) 박스거더 교량의 정착부 거동 및 해석)

  • 오병환;임동환;이명규;백신원
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.36-41
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    • 1994
  • 프리캐스트 프리스트레스트 콘크리트 상자형 교량의 정착부에 프리스트레스 힘이 도입되면, 과다한 국부집중 하중으로 인하여 균열이 발행할 수 있으며, 최근 이러한 교량의 건설시 텐던을 따라가며 심각한 균열이 발생한 경우가 있다. 본 논문은 프리캐스트 프리스트레스트 콘크리트 상자형 교량의 정착부에 발생하는 국부집중 응력의 분포 특성을 규명하고, 이를 토대로 파괴기구 고찰함에 목적이 있다. 이를 위하여 정착부 파괴에 직접적인 영향을 미치는 단면의 형상, 텐던의 배치상태, 국부보강 철근의 형태 및 구조보강 철근량 등을 변수로 하는 역학적 거동 실험 및 해석 연구가 수행되었다. 위의 실험 및 해석연구결과 정착부 파괴양상이 규명되었으며, 프리스트레스 정착부의 새로운 파괴기구 개념이 제시되어, 정착부 파괴과정을 적절히 설명하고 있다.

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Design of longitudinal prestress of precast decks in twin-girder continuous composite bridges (2거더 연속강합성 교량의 프리캐스트 바닥판 종방향 프리스트레스 설계)

  • Shim, Chang Su;Kim, Hyun Ho;Ha, Tae Yul;Jeon, Seung Min
    • Journal of Korean Society of Steel Construction
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    • v.18 no.5
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    • pp.633-642
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    • 2006
  • Serviceability design is required to control the cracking at the joint of precast decks with longitudinal prestress in continuous composite bridges. Details of twin-girder bridges are especially complex not only due to their main reinforcements and transverse prestresses for the design of long-span concrete slabs, but also due to the shear pockets for obtaining the composite action. This paper suggests the design guidelines for the magnitude of the effective prestress and for the selection of filling materials and their requirements that would allow for the use of precast decks for twin-girder continuous composite bridges. The necessary initial prestress was also evaluated through long-term behavior analysis. From the analysis, existing design examples were revised and their effectiveness was estimated. When a filling material with a bonding strength higher than the requirement is used in the region of a high negative moment, a uniform configuration of the longitudinal prestressing steels along thewhole span length of continuous composite bridges can be achieved, which would result in the simplification of the details and the reduction of the construction costs.

Experimental Verification of Age-adjusted Effective Modulus Method to Long-Term Behavior Estimation of Prestressed Composite Girders (재령보정 유효계수방법에 의한 프리스트레스트 합성거더의 장기거동 실험 검증)

  • Bae, Doo-Byong;Oh, Chang-Kook;Choi, Sok-Hwan
    • Journal of Korean Society of Steel Construction
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    • v.24 no.5
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    • pp.571-582
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    • 2012
  • Prestressed composite girders provide efficient composite action by applying prestress to the sub-encasing concrete. In this study, an enhanced prestressed composite girder with forms suspended from the steel girder is utilized. Long-term behavior of the prestressed composite girder is estimated using age-adjusted effective modulus method, which is verified experimentally using measurements obtained from an in-service bridge. Then, parametric study is carried out to investigate the influences caused by ambient temperature, humidity, prestressing and concrete casting date.

A Experimental Study on Bending Behaviors of Prestressed Hot-rolled H-Beam (프리스트레스된 압연강재보(H-BEAM)의 휨 거동에 대한 실험적 연구)

  • Yhim, Sung Soon;Jeong, Chan Haek
    • Journal of Korean Society of Steel Construction
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    • v.18 no.2
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    • pp.239-250
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    • 2006
  • In this study, the experimental bending behaviors of an H-secti on-steel-beam-attached high-strength steel plate or steel beam were analyzed. Its structural performance was verified by comparing the results of the experiment and the analysis that were conducted. In fabricating an unprestressed composite beam using two members that have different strengths, the generated slip on the joint in proport problem because of the redistribution of force caused by the lose state of the joint. Therefore, when fabricating composite beams, it is important to load them with prestressed forces. Based on the results of the experiment that was conducted, the prestressed composite-steel-beam-attached steel plate or beam has a higher bending resistance and load-carrying capacit

Behavior of Prestressed Concrete Panels under Blast Load (폭발하중을 받는 프리스트레스트 콘크리트 패널의 거동)

  • Jo, Eunsun;Kim, Min Sook;Park, Jong Yil;Lee, Young Hak
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.27 no.2
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    • pp.113-120
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    • 2014
  • This paper showed the behavior of the material four members under blast load, and are trying to demonstrate the effectiveness of the prestress. The prestressed concrete structures are on the rise, but there is little research in this regard explosion. Concrete panels, Reinforced concrete panels, the prestressed concrete panels, and the prestressed reinforced concrete panels was set variables. TNT 500 kg was an explosion in the distance 3m. Analysis, concrete and reinforced concrete members after an explosion occurred continuously deformed, but the including prestressed panel deformation occurs only at the beginning of the explosion were able to see the results. That is, the including prestressed member is prestressed against blast load cracking and destruction can be seen that control.

Elasto-Plastic Analysis for Flexural Behavior of Externally Prestressed Composite Bridges (외부 프리스트레스트 강합성 교량의 탄소성 휨 거동해석)

  • Chung, Seung In;Ryu, Hyung Keun;Chang, Sung Pil
    • Journal of Korean Society of Steel Construction
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    • v.15 no.1
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    • pp.59-68
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    • 2003
  • Recent application researches on external pre-stressing method of composite structures have been conducted to explore its advantages. An external pre-stress could improve mechanical behavior and maintenance, and is economically efficient. In this paper, the Incremental Deformation Method (IDM) was proposed to analyze the elasto-plastic flexural behavior of externally pre-stressed composite bridge with consideration for the material's nonlinearity. This method was verified with experimental results.