• Title, Summary, Keyword: 긴장력 손실

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Vibration-Based Monitoring of Prestress-Loss in PSC Girder Bridges (PSC 거더교의 진동기반 긴장력 손실 모니터링)

  • Kim, Jeong-Tae;Hong, Dong-Soo;Park, Jae-Hyung;Cho, Hyun-Man
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.21 no.1
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    • pp.83-90
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    • 2008
  • A vibration-based monitoring system is newly proposed to predict the loss of prestress forces in prestressed concrete (PSC) girder bridges. Firstly, a global damage alarming algorithm is newly proposed to monitor the occurrence of prestress-loss by using the change in frequency responses. Secondly, a prestress-loss prediction algorithm is selected to estimate the extent of prestress-loss by using the change in natural frequencies. Finally, the feasibility of the proposed system is experimentally evaluated on a scaled PSC girder model for which acceleration responses were measured for several damage scenarios of prestress-loss.

Design of Additional Tendon Force and Evaluation of Resistant Moment for Prestressed Concrete Composite Section (프리스트레스트 콘크리트 합성단면에 도입되는 추가 긴장력 설계와 저항모멘트 평가)

  • Yon Jung-Heum;Kim Do-Goon
    • Journal of the Korea Concrete Institute
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    • v.16 no.3
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    • pp.335-344
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    • 2004
  • A general composite section of precast and cast-in-place concrete with prestressed and nonprestressed reinforcements was analyzed to calculate residual stresses and loss of prestressing force caused by internal constraints of concrete long-term deformation. From the analytical results, equations to design additional prestressing force and to evaluate resistant moment of the composite section were proposed. The equations shows that the additional prestressing force can be over-estimated if the loss rate of the first prestressing force is over-estimated from the lumped sum of a design code. The analytical procedure with the proposed equations has been applied to a composite section using the AASHTO Type 5 girder. The loss rates of the additional prestressing force appling to the precast concrete girder was less than those appling to the composite girder. However, the resistant moment of the additional prestressing force on the composite girder was much larger than that on the precast concrete girder. The additional prestressing force appling to the composite section was very effective for strengthening of the prestressed concrete composite girder.

Measurement of Lateral Prestress Force of UHPC Cross Beam using the Smart Tendon (스마트강연선을 이용한 UHPC 가로보의 횡방향 긴장력 계측)

  • Kim, Hyun-Woo;Kim, Jae-Min;Kim, Young-Jin;Kim, Young-Sang
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.178-181
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    • 2011
  • 본 연구에서는 광섬유센서를 내장한 스마트강연선을 이용하여 초고성능콘트리트로 제작된 하이브리드 사장교 세그먼트의 횡방향 도입 긴장력을 계측하고 세그먼트 내부의 프리스트레스를 계측하여 즉시손실에 해당하는 정착장치 활동에 의한 손실과 마찰손실을 도로교설계기준(2005)의 설계 마찰손실과 비교하였다. 제작된 2개의 UHPC 사장교 세그먼트는 횡방향 길이 16.7m, 종방향 길이 1.75m, 높이 1.5m이며 각 시험체의 1/4, 1/2, 3/4지점에 긴장력을 계측하기 위해 3개의 FBG센서를 배치하였다. 긴장력은 유압잭을 이용하여 5개의 강연선에 동시에 순차적으로 도입되었으며, 단부에서 최대 도입 긴장력은 세그먼트 1은 734kN, 세그먼트 2는 639kN이었다. 도로교설계기준에 제시된 마찰계수의 중간값(파상마찰계수=0.00405, 곡률마찰계수=0.20)을 사용하여 FBG센서 위치에서 계산된 긴장력은 계측치와 5% 이내의 차이를 보였으며, 정착장치 활동에 의한 순간손실은 긴장단에서 최대 12.8%로 계측되었다. 이로부터 이 연구에서 제시하는 긴장력계측방법의 적용성을 입증할 수 있었으며, 향후 이 방법은 프리스트레스트 콘크리트 교량의 설계기준 마찰계수 개정을 위한 연구에 좋은 도구로 활용될 수 있을 것으로 기대된다.

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Reduction of Prestress Loss in PSC (Prestressed Concrete) Continuous Girder by Employing Block-out Method (지점부 블록아웃 공법으로 연속화된 프리스트레스트 콘크리트 거더의 긴장력 손실 저감)

  • Shin, Kyung-Joon;Kim, Yun-Yong;Kim, Seung-Jin;Choo, Tae-Heon;Lee, Hwan-Woo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.4
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    • pp.77-83
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    • 2014
  • Prestressed concrete girder bridge has been one of the most widely used bridges in the world because of its excellent construction feasibility, economic efficiency, serviceability, and safety. In certain situations, the prestressing tendon is supposed to be bent by the construction error and the radius of curvature at the continuous joint of PSC girders, and this leads to the loss of prestressing force. However, this kind of prestress loss is not considered in the design and construction processes. This study proves that the prestress loss occurs at the continuous joint due to the local bending of tendon by the construction error or the radius of curvature. Also, a method that can reduce this type of prestress loss is proposed, and proved by the experiment. The result shows that maximum 10% of prestress loss occurs at the continuous joint and the proposed block-out method can reduce the prestress loss ratio by maximum 5%, approximately. This means that the block-out method can enhance the prestressing efficiency of continuous PSC girder bridges.

Development of Visual Confirmation Device for Anchor Tensile Force (앵커 긴장력 상시확인을 위한 육안확인장치 개발)

  • Yoon, Hwan Hee;Lee, Yong Joo;Oh, Dong Wook;Kim, Dong Hyun;Jung, Hyuk Sang
    • Tunnel and Underground Space
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    • v.28 no.5
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    • pp.493-511
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    • 2018
  • This paper deals with visual confirmation device for tensile force verification in order to cope with tensile force loss of ground anchor. Ground anchors are constructed to ensure the stability of social infrastructure facilities, but continuous loss of tensile force is seriously concerned about safety of the facilities. This requires the maintenance of the anchors, but the current measuring of residual tensile force is done by sampling, taking into account economic aspects, which limits precision. In this paper, conducted a conceptual design, tensile experiment, and field test for the purpose of developing an anchor tensile force visual device to check the tensile force of the anchors.

Evaluation on the Lost Prestressing Force of an External Tendon Using the Combination of FEM and HGA: I. Theory (FEM과 HGA의 조합을 이용한 외부 긴장재의 손실 긴장력 평가: I. 이론)

  • Park, Taehyo;Jang, Hang-Teak;Noh, Myung-Hyun;Park, Kyu-Sik
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.13 no.5
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    • pp.109-120
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    • 2009
  • This paper introduces a new method to estimate the loss of prestressing force for the externally prestressing tendon. The proposed method that combines of HGA and FEM is able to identify the lost tensile force of a externally prestressed tendon. The identification variables of the proposed method is a exteranlly prestressed tendon of tension, effective nominal diameter, mass per unit length and Rayleigh damping coefficients. First of all, a finite element model system is constructed to consider the effect of damping, and these variables are identified using inverse analysis technique - updating algorithm. Finally, throughout total 3 cases of numerical tests, the numerical propriety of the proposed method is verified. Here, it is seen that the errors in the estimated variables by the proposed method are about 1% except in the case of Rayleigh damping coefficients.

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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    • 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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Evaluation on the Lost Prestressing Force of an External Tendon Using the Combination of FEM and HGA: II. Experimental Verification and Field Applications (FEM과 HGA의 조합을 이용한 외부 긴장재의 손실 긴장력 평가: II. 실험적 검증 및 현장적용)

  • Jang, Hang-Teak;Noh, Myung-Hyun;Park, Kyu-Sik;Park, Taehyo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.13 no.5
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    • pp.121-132
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    • 2009
  • This paper introduces an experimental verification and a field application of the proposed technique using the combination of FEM and HGA about the loss prestressing force of an exteranl tendon by above same authors. The vibration tests have been conducted by using a laboratory models and the externally prestressed tendon at the field and the natural frequencies are extracted from the vibration tests. The proposed technique based on the extracted natural frequencies is applied. It is seen that the errors in the tension and lost prestressing force by proposed technique are about 4% from a laboratory model test. For the model verification at field, exact modeling has beem made with Rayleigh damping. It is seen that the error in the tension by proposed technique is less than 1% and the estimated lost prestressing force converges less than the exact value.

Prestressing Loss Management for PSC Girder Tendon Based on EM Sensing (EM센서를 활용한 PSC 텐던 긴장력 손실 관리)

  • Kim, Junkyeong;Park, Jooyoung;Zhang, Aoqi;Lee, Hwanwoo;Park, Seunghee
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.4
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    • pp.369-374
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    • 2015
  • In this paper, an EM sensing based prestressing force estimation method is proposed, in which it can estimate tensile force of PS tendon for PSC girder. The PSC girder has more improved performance than the general concrete girder by introducing the prestressing to the concrete. Thus the PSC girder bridge is widely constructed due to its high performance and low cost. However, the prestressing force has not been managed nevertheless it is major factor for the maintenance of the PSC girder bridge. The prestressing force was just measured during construction using jacking device and after that, it can not be managed. For this reason, this paper proposes a tensile force estimation method of PS tendon based on EM sensor. The permeability of ferroelectric material is changed according to the induced stress to the material, in which it can be measured using EM sensor. To measure the permeability of PS tendon, the EM sensor was fabricated and verified by performing the MTS test. The test was performed using 7-wire steel tendon under the 0, 40, 80, 120, 160, 200 KN of tensile force. The permeability of PS tendon was gradually decreased according to the increasement of tensile force. The regression method was used to find the relation between permeability and stress. As a result, the permeability has linear relation with the tensile force of PS tendon and the pre-stressing force can be estimated by the derived estimation equation.

FE-Model Update for Prestress-Force Monitoring of Prestressed Concrete Girders (프리스트레스트 콘크리트 거더의 긴장력 모니터링을 위한 유한요소모델 개선)

  • Ho, Duc-Duy;Hong, Dong-Soo;Kim, Jeong-Tae;Yun, Chung-Bang
    • 한국방재학회:학술대회논문집
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    • pp.39.2-39.2
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    • 2010
  • 본 논문에서는 프리스트레스트 콘크리트 거더 구조물의 긴장력 손실을 검색하기 위한 유한요소모델 개선기법을 제시하였다. 먼저, 유한요소모델개선 기법의 이론적 배경을 제시하였다. 두 번째로, 다수의 긴장력 조건하의 모형 PSC 거더에 대한 모드파라메터들을 측정하기위해 진동실험을 수행하였다. 세 번째로, 유한요소모델의 구조파라메터 개선을 통해 실험결과와 유사한 고유진동수를 얻기 위한 진동기반 구조식별을 수행하였다. 마지막으로, 다수의 긴장력 조건하에서 실험을 통해 측정된 고유진동수와 수치적으로 식별된 고유 진동수를 이용하여 모델개선 기법의 적합성을 검증하였다.

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