• Title/Summary/Keyword: 프리텐션

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Evaluation & Development of Strengthening Method by External Post-tension (외부 포스트텐션 보강공법의 개발 및 평가)

  • Lim, Jae-Hyung;Moon, Jeong-Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.5
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    • pp.91-100
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    • 2008
  • A technique strengthened to the reinforced concrete members using the external post- tensioned method offers the advantages in speed and simplicity of installation over other, established, strengthening techniques. But this technique has many unreasonable facts. This paper are analyzed an unreasonable facts of the previous external post-tension technique. The purpose of this paper proposed Bow system as the new technique strengthened to the reinforced concrete members. The Bow system which is better technique than the previous technique was introduced with the experimental/analytical data.

Behavior of Post-Tensioned Prestressed Concrete Pavement under Prestress Application (포스트텐션드 콘크리트 포장의 프리스트레스 도입 시 거동 분석)

  • Park, Hee-Beom;Kim, Seong-Min;Kim, Dong-Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.137-138
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    • 2009
  • This study was conducted to analyze the behavior of PTCP (Post-Tensioned prestressed Concrete Pavement) under tensioning by performing field tests when the experimental PTCP slab was being constructed.

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Prediction of Transfer Lengths in Pretensioned Concrete Members Using Neuro-Fuzzy System (뉴로-퍼지 시스템을 이용한 프리텐션 콘크리트 부재의 전달길이 예측)

  • Kim, Minsu;Han, Sun-Jin;Cho, Hae-Chang;Oh, Jae-Yuel;Kim, Kang Su
    • Journal of the Korea Concrete Institute
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    • v.28 no.6
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    • pp.723-731
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    • 2016
  • In pretensioned concrete members, a certain bond length from the end of the member is required to secure the effective prestress in the strands, which is defined as the transfer length. However, due to the complex bond mechanism between strands and concrete, most transfer length models based on the deterministic approach have uncertainties and do not provide accurate estimations. Therefore, in this study, Adaptive Neuro-Fuzzy Inference System (ANFIS), a Neuro-Fuzzy System, is introduced to reduce the uncertainties and to estimate the transfer length more accurately in pretensioned concrete member. A total of 253 transfer length test results have been collected from literatures to train ANFIS, and the trained ANFIS algorithm estimated the transfer length very accurately. In addition, a design equation was proposed to calculate the transfer length based on parametric studies and dimensional analyses. Consequently, the proposed equation provided accurate results on the transfer length which are comparable to the ANFIS analysis results.

Dynamic Behavior of Pretensioned Prestressed Members for Releasing Methods (긴장력 도입 방법에 따른 프리텐션 부재 단부의 동적 거동에 관한 연구)

  • Lee, Seung-Jung;Zi, Goang-Seup;Moon, Do-Young;Kim, Kyu-Sun;Kim, Jang-Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.139-140
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    • 2009
  • In this paper, the dynamic behavior of pretensioned concrete structures was investigated experimentally during detensioning for two different releasing methods: flame-cutting and hydraulic-jacking. According to the experimental results of strain changes, although detensioning time of hydraulic-jacking is shorter than that of fame-cutting, the prestressing force loss of fame-cutting is larger than that of hydraulic-jacking.

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The Effect of Mild Tensile Reinforcement and Effective Prestress on the Flexural Performance of the Prestressed Lightweight Concrete Beams with Unbonded Tendons (비부착 프리스트레스트 경량 콘크리트 보의 휨 거동에 대한 부착 철근과 유효 프리스트레스의 영향)

  • Mun, Ju-Hyun;Yang, Keun-Hyeok;Byun, Hang-Yong
    • Journal of the Korea Concrete Institute
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    • v.23 no.5
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    • pp.617-626
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    • 2011
  • Seven post-tensioned lightweight concrete (LWC) beam specimens were tested under a symmetrical two-point top loading system. The parameters investigated were the amounts of mild longitudinal reinforcement and effective prestressing. The design compressive strength and dry density of the LWC tested were 30 MPa and 1,770 $kg/m^3$, respectively. Similar to post-tensioned normal weight concrete (NWC) beams, the crack propagation and stress increase of the unbonded tendons were significantly affected by the amounts of mild longitudinal reinforcement and effective prestressing. With the increase in the amounts of mild longitudinal reinforcement and effective prestressing, the serviceability and flexural capacity of the beams were enhanced whereas the stress increase in the unbonded tendons decreased. To control the crack width in post-tensioned LWC beams, a minimum amount of mild longitudinal reinforcement specified in ACI 318-08 provision is required. The flexural behavior of post-tensioned LWC beams and stress increase of the unbonded tendons could be rationally predicted by the proposed non-linear two-dimensional analysis. On the other hand, ACI 318-08 flexure provision was too conservative about the post-tensioned LWC beams.

Measurement of Transfer Length for a Seven-Wire Strand with FBG Sensors (FBG 센서를 이용한 강연선 전달길이 측정)

  • Lee, Seong-Cheol;Choi, Song-Yi;Shin, Kyung-Joon;Kim, Jae-Min;Lee, Hwan-Woo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.6
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    • pp.707-714
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    • 2015
  • In this paper, an experimental program has been conducted to investigate transfer length in high strength concrete members pretensioned through a seven-wire strand with FBG sensors. To measure transfer length, five members were fabricated, which had a length of 3 m and a cross-section of $150{\times}150mm$. It was measured that the concrete compressive strength was 58MPa at pretensioning. Test results indicated that more precise and reliable measurement on the transfer length was attained with FBG sensors than conventional gauges attached on concrete surface. Through comparing the measured transfer length and predictions, applicability of several transfer length models in literature was investigated. This paper can be useful for relevant research field such as investigation on the bond mechanism of a seven-wire strand in concrete members.

Parameter Analysis for Design of Pretension Girder Bridge for Urban Maglev Transit (도시형 자기부상열차 프리텐션 거더교의 설계변수 분석)

  • Lee, Jae-Ho;Kim, Do-Hak;Kim, Seung-Hyun;Kim, Sung-Il
    • Journal of the Korean Society for Railway
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    • v.19 no.4
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    • pp.515-525
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    • 2016
  • Parameter analysis of a pretension girder bridge for urban maglev transit was performed to identify the main design parameters and their effect. Girder deflection at mid-span is the most important design criteria of urban maglev transit. Therefore, concrete compressive strength, girder height, girder length, and unbonded tendon length were selected as the design parameters that relate to girder deflection. In addition, tendon layout and unbonded tendon ratios were also considered as design parameters to control the top stress of the pretension girder section at the support. The analysis results show that both the girder height and length are dominant design parameters governing girder deflection, more important than compressive strength and unbounded tendon length. And, sensitivity analysis makes this study suggest design weight value. In terms of stress, a tendon layout that can satisfy the unbounded tendon rule requires an additional tendon or rebar at the upper section to control the tensile stress on top of the section. Therefore, to improve feasibility and constructability in the future, an enhanced unbonded tendon rule considering the load characteristics of the urban maglev system should be studied.

Flexural Strength Estimation of Half-Depth Precast Concrete Composite Slab Manufactured by the Long-Line Method (롱라인 공법으로 제작한 반단면 프리캐스트 콘크리트 합성 슬래브의 휨강도 평가)

  • Choi, Jin-Woo;Seo, Su-Hong;Joo, Hyung-Joong;Yoon, Soon-Jong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.4
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    • pp.48-56
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    • 2013
  • Prestressed concrete (PSC) members are readly available in civil engineering applications due to the convenience of construction and easy of quality control in the manufacturing process of the member. Especially, half-depth precast concrete composite slab, which is one of the PSC flexural members is developed recently using the long-line method. The half-depth precast concrete composite slabs are composed of the precast concrete and the in-situ concrete placed at the site. In this paper, we present the results of experimental investigations pertaining to the pretensioning efficiency and the flexural behavior of half-depth precast concrete composite slab which is made of precast PSC manufactured by the long-line method. In the long-line method, the pretensioned precast member is manufactured simultaneously, by tensioning tendons at once. In addition, we suggest the equation that can estimate the flexural strength of half-depth precast concrete composite slab reasonably by considering the effects of rebar embedded in the precast PSC flexural member.