• Title/Summary/Keyword: prestress

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A Study on the Determination of the Optimal Parameter for the Evaluation of the Effective Prestress Force on the Bonded Tendon (부착식 텐던의 유효 긴장력 평가를 위한 최적의 매개변수 결정에 관한 연구)

  • Jang, Jung Bum;Lee, Hong Pyo;Hwang, Kyeong Min;Song, Young Chul
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.2A
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    • pp.161-168
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    • 2010
  • The bonded tendon was adopted to the reactor building of some operating nuclear power plants in Korea and the assessment of the effective prestress force on the bonded tendon is being issued as an important pending problem for continuous operation beyond their design life. The sensitivity analysis of various parameters was carried out to evaluate the effective prestress force using the system identification technique and the optimal parameters were determined for SI technique in this study. The 1/5 scaled post-tensioned concrete beams with the bonded tendon type were manufactured and in order to investigate the relationship of the natural frequency and the displacement to the effective prestress force, impact test, SIMO sine sweep test and bending test using the optical fiber sensor and the compact displacement transducer were carried out. As a result of tests, both the natural frequency and the displacement show the good relationship with the effective prestress force and both parameters are available for the SI technique to estimate the effective prestress force.

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
    • KSCE Journal of Civil and Environmental Engineering Research
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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.

Flexural Vibration Characteristics of Prestressed Concrete Girders due to Changes in Prestress Forces (프리스트레스트 콘크리트 거더의 긴장력 변화에 따른 휨 진동 응답 특성)

  • Lee, Jung-Mi;Kim, Jeong-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.13 no.4 s.56
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    • pp.137-147
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    • 2009
  • In this study, several flexural vibration characteristics of prestressed concrete girders due to changes in prestress forces are experimentally analyzed. In order to achieve the objective, the following approaches are implemented. First, several methods to extract vibration response features from output-only signal are selected. Next, a large-scaled prestressed concrete girder model is constructed to analyze relation between the prestress forces and the vibration features in the prestressed concrete girder. Then acceleration responses are measured from the girder for several prestress force scenarios. Finally, vibration characteristics of the prestressed concrete girder due to change in prestress force are experimentally analyzed. The values of features extracted by the selected methods are reduced due to prestress-loss. Especially, the value of features are linearly reduced in the early prestress-loss.

Analysis of key elements of single-layer dome structures against progressive collapse

  • Zhang, Qian;Huang, Wenxing;Xu, Yixiang;Cai, Jianguo;Wang, Fang;Feng, Jian
    • Steel and Composite Structures
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    • v.42 no.2
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    • pp.257-264
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    • 2022
  • The analysis of the progressive collapse resistance of structures is a well-known issue among structural engineers. Large-span reticulated dome structures are commonly utilized in large public buildings, necessitating research into their progressive collapse resistance to assure user safety. The most significant part of improving the structural resilience of reticulated domes is to evaluate their key elements. Based on a stiffness-based evaluation approach, this work offers a calculating procedure for element importance coefficient. For both original and damaged structures, evaluations are carried out using the global stiffness matrix and the determinant. The Kiewitt, Schwedler, and Sunflower reticulated domes are investigated to explore the distribution characteristic of element importance coefficients in the single-layer dome structures. Moreover, the influences of the load levels, load distributions, geometric parameters and topological features are also discussed. The results can be regarded as the initial concept design reference for single-layer reticulated domes.

A Suggestion of New Approach for Measurement of Remaining Prestress (잔존프리스트레스 측정을 위한 새로운 접근법 제안)

  • 이창수;김승익;김현겸
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.835-840
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    • 2001
  • The new approach is a kind method of restoring temporary defect. Here, it is important for the defect not to occur problems of both local effect and global system. A basic concept is that it measures remaining prestress of PSC structures during the defect is restored. This study suggested new approach for measurement of remaining prestress. Two important results are obtained. First, safety problems, local stress concentration and global system, are very satisfied. Second, measurement value exists within error bound $\pm$ 1% in comparison with known value.

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A Study on the Design Meghod for PSC I Girders with additional Prestress (프리트스레스를 단계적으로 도입하는 PSC I형 거더의 설계에 관한 연구)

  • 한만엽;김양현;진경석
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.04a
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    • pp.375-380
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    • 1999
  • It is required efficient section shape like bulb-tee girders with high strength concrete to construct long span bridges economically. However, the trpical design method for PSC I-girders include bulb-tees, the concrete girder prestressed only one time at same time. But in this paper, new design method prestress increases as each load-stress stage. The incrementally prestressed concrete (IPC) girders can reduce the required area of grider section and extend span length by additional prestress. So it is able to construct long span bridges economically by using IPC girders.

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Local dynamic characteristics of PZT impedance interface on tendon anchorage under prestress force variation

  • Huynh, Thanh-Canh;Lee, Kwang-Suk;Kim, Jeong-Tae
    • Smart Structures and Systems
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    • v.15 no.2
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    • pp.375-393
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    • 2015
  • In this study, local dynamic characteristics of mountable PZT interfaces are numerically analyzed to verify their feasibility on impedance monitoring of the prestress-loss in tendon anchorage subsystems. Firstly, a prestressed tendon-anchorage system with mountable PZT interfaces is described. Two types of mountable interfaces which are different in geometric and boundary conditions are designed for impedance monitoring in the tendon-anchorage subsystems. Secondly, laboratory experiments are performed to evaluate the impedance monitoring via the two mountable PZT interfaces placed on the tendon-anchorage under the variation of prestress forces. Impedance features such as frequency-shifts and root-mean-square-deviations are quantified for the two PZT interfaces. Finally, local dynamic characteristics of the two PZT interfaces are numerically analyzed to verify their performances on impedance monitoring at the tendon-anchorage system. For the two PZT interfaces, the relationships between structural parameters and local vibration responses are examined by modal sensitivity analyses.

PCA-based filtering of temperature effect on impedance monitoring in prestressed tendon anchorage

  • Huynh, Thanh-Canh;Dang, Ngoc-Loi;Kim, Jeong-Tae
    • Smart Structures and Systems
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    • v.22 no.1
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    • pp.57-70
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    • 2018
  • For the long-term structural health monitoring of civil structures, the effect of ambient temperature variation has been regarded as one of the critical issues. In this study, a principal component analysis (PCA)-based algorithm is proposed to filter out temperature effects on electromechanical impedance (EMI) monitoring of prestressed tendon anchorages. Firstly, the EMI monitoring via a piezoelectric interface device is described for prestress-loss detection in the tendon anchorage system. Secondly, the PCA-based temperature filtering algorithm tailored to the EMI monitoring of the prestressed tendon anchorage is outlined. The proposed algorithm utilizes the damage-sensitive features obtained from sub-ranges of the EMI data to establish the PCA-based filter model. Finally, the feasibility of the PCA-based algorithm is experimentally evaluated by distinguishing temperature changes from prestress-loss events in a prestressed concrete girder. The accuracy of the prestress-loss detection results is discussed with respect to the EMI features before and after the temperature filtering.

Improved prediction of residual effective prestress force of Railway bridge PSC beam (철도교 PSC Beam의 잔류유효긴장력 추정 개선방안 연구(I))

  • Lee, Seong-Won;Lee, Ki-Seong;Lee, Won-Chang
    • Proceedings of the KSR Conference
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    • 2003.10b
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    • pp.538-543
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    • 2003
  • This study is the developed prediction of residual effective prestress force of prestressed concrete beam bridges. Developed prediction method is based on the center camber of prestressed concrete beam, structural design. report of various PSC beams, construction reference materials of PSC beams. Evaluation of residual effective prestress force by developed method is compared with evaluation by structural design. This comparison results shows that this developed method is very effective method. Therefore prediction of residual effective prestress force by this developed method will be used for evaluation of the rating of various PSC beam bridges(road bridges and railway bridges).

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Prediction of Prestress Foce Losses by Nonlinear Regression (비선형 회귀분석에 의한 프리스트레스 하중의 사간에 따른 소실 예측)

  • 오병환;양인환;홍경옥;채성태
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.04a
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    • pp.347-352
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    • 1998
  • The purpose of this paper is to present and establish a procedure to predict the prestress forces during the service life of the structure. The statistical approach of this procedure is using the in-situ measurement data of the post-tensioning system to develop a nonlinear regression analysis. The method of least squares is used to fit a certain function a set of data. Use of a nonlinear model is achieved by its logarithmic transformation and sunsequent use of linear-regression theory. The regression analysis result can be used to check the prestress force during the service life so that the remaining prestress force is equal to or exceeds the design requirement. Results from the measurement data of PSC box girder bridge structure were used to demonstrate the procedures.

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