• Title/Summary/Keyword: prestressed tendon

Search Result 193, Processing Time 0.029 seconds

An Experimental Study on The Frictional Loss of Stress in The Prestressing Tendons (PS 긴장재의 마찰손실량에 관한 실험적 연구)

  • 정배근;한경봉;박선규
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2000.04a
    • /
    • pp.417-422
    • /
    • 2000
  • In prestressed concrete structures, determining serviceability and safety it is important to exactly calculate effective prestress force acting on structures. for the determination of effective prestress force, friction loss of the prestressing tendon should be decided exactly, but it is very difficult to measure the exact prestress force on the site and there is no actual field data. Therefore the friction loss coefficient recommended by the specification is not verified. in this paper, the friction loss standard PSC-Beam will be investigated, and is will be found what kind of relationship between the specification and the site. The results from this study can be summarized as follows. For jacking at both ends, actual intial prestress force in the center section of PCS-Beam was about 1.61% larger than theoretical initial prestress force and for hacking at one end, actual initial prestress force was approximate 4.9% lower than theoretical initial prestress force. Thus, for the exact calculation of friction loss, friction coefficient should be modified according to jacking methods.

  • PDF

Application of Amplitude Demodulation to Acquire High-sampling Data of Total Flux Leakage for Tendon Nondestructive Estimation (덴던 비파괴평가를 위한 Total Flux Leakage에서 높은 측정빈도의 데이터를 획득하기 위한 진폭복조의 응용)

  • Joo-Hyung Lee;Imjong Kwahk;Changbin Joh;Ji-Young Choi;Kwang-Yeun Park
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.27 no.2
    • /
    • pp.17-24
    • /
    • 2023
  • A post-processing technique for the measurement signal of a solenoid-type sensor is introduced. The solenoid-type sensor nondestructively evaluates an external tendon of prestressed concrete using the total flux leakage (TFL) method. The TFL solenoid sensor consists of primary and secondary coils. AC electricity, with the shape of a sinusoidal function, is input in the primary coil. The signal proportional to the differential of the input is induced in the secondary coil. Because the amplitude of the induced signal is proportional to the cross-sectional area of the tendon, sectional loss of the tendon caused by ruptures or corrosion can be identified by the induced signal. Therefore, it is important to extract amplitude information from the measurement signal of the TFL sensor. Previously, the amplitude was extracted using local maxima, which is the simplest way to obtain amplitude information. However, because the sampling rate is dramatically decreased by amplitude extraction using the local maxima, the previous method places many restrictions on the direction of TFL sensor development, such as applying additional signal processing and/or artificial intelligence. Meanwhile, the proposed method uses amplitude demodulation to obtain the signal amplitude from the TFL sensor, and the sampling rate of the amplitude information is same to the raw TFL sensor data. The proposed method using amplitude demodulation provides ample freedom for development by eliminating restrictions on the first coil input frequency of the TFL sensor and the speed of applying the sensor to external tension. It also maintains a high measurement sampling rate, providing advantages for utilizing additional signal processing or artificial intelligence. The proposed method was validated through experiments, and the advantages were verified through comparison with the previous method. For example, in this study the amplitudes extracted by amplitude demodulation provided a sampling rate 100 times greater than those of the previous method. There may be differences depending on the given situation and specific equipment settings; however, in most cases, extracting amplitude information using amplitude demodulation yields more satisfactory results than previous methods.

A Study on the Static and Fatigue Behavior of Steel-Confined Prestressed Concrete Girder (강재로 구속된 프리스트레스트 콘크리트 합성거더의 정적 및 피로거동)

  • Kim, Jung Ho;Park, Kyung Hoon;Hwang, Yoon Koog;Lee, Sang Yoon
    • Journal of Korean Society of Steel Construction
    • /
    • v.16 no.6 s.73
    • /
    • pp.725-736
    • /
    • 2004
  • A new type of girder, called steel-confined prestressed concrete girder (SCP girder), has been developed, which maximizes the structural advantages of concrete, steel, and PS tendon, and improves on the shortcomings of steel plate girder, PSC I-girder, and preflex girder bridge for use in the construction of middle- or long-span bridges. To verify the propriety of design, structural safety, and applicability of this girder, a static load test was carried out (Kim et al.., 2002). Since the main damage typically sustained by steel bridges results from the fatigue caused by the repetition of traffic loads, fatigue safety must therefore be guaranteed in applying the SCP girder in the construction of real bridges. In this study, a fatigue test was carried out to investigate fatigue behavior and provide basic data for fatigue design. Based on the fatigue test, the fatigue safety of the girder was estimated. For the fatigue test, 10-m specimens were designed for a standard-design truckload (DB-24). A static load test was also performed before the fatigue test to analyze the structural behavior of the specimens. After the fatigue test, outer steel plates were removed to observe the condition of the concrete in the girder.

Prediction Model of Unbonded Tendon Stresses in Post-Tensioned Members (포스트텐션 부재에서 비부착긴장재의 응력 거동 예측 모델)

  • Kim, Kang-Su;Lee, Deuck-Hang;Kal, Gyung-Wan
    • Journal of the Korea Concrete Institute
    • /
    • v.21 no.6
    • /
    • pp.763-771
    • /
    • 2009
  • As the demand on long span structures increases more in recent years, the excessive deflection, in addition to the ultimate strength, in horizontal members becomes a very important issue. For this reason, as an alternative method to effectively solve the deflection problems, the application of post-tensioned structural system with unbonded tendon increases gradually. However, most of the existing researches on post-tensioned members with unbonded tendons (UPT) focused on the ultimate flexural strength, which would be impossible or improper to check serviceability such as deflections. Therefore, this study aims at proposing a stress prediction model for unbonded tendons that is applicable to the behavior of UPT members from the very initial loading stages, post-cracking states, and service to ultimate conditions. The applicability and accuracy of the proposed model were also evaluated comparing to the existing test results from literature. Based on such comparison results, it was verified that the proposed model provided very good predictions on tendon stresses of UPT members at various loading stages regardless their different characteristics; wide range of reinforcement index, different loading patterns, and etc. The proposed model especially well considered the effect of various loading types on stress increases of unbonded tendons, and it was also very suitable to apply on the over-reinforced members that easily happened during strengthening/repairing work.

The Structural Integrity Test for a PSC Containment with Unbonded Tendons and Numerical Analysis I (비부착텐던 PSC 격납건물에 대한 구조건전성시험 및 수치해석 I)

  • Noh, Sanghoon;Jung, Raeyoung;Kim, Sung-Taek;Lim, Sang-Jun
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.28 no.5
    • /
    • pp.523-533
    • /
    • 2015
  • A reactor containment acts as a final barrier to prevent leakage of radioactive material due to the possible reactor accidents into external environment. Because of the functional importance of the containment building, the SIT(Structural Integrity Test) for containments shall be performed to evaluate the structural acceptability and demonstrate the quality of construction. An initial numerical analysis was performed to simulate the results obtained from the SIT for a prestressed concrete(PSC) structure. But the analysis results by the initial model expected smaller displacements than the measured ones by 30% at some locations. Accordingly, the research and development to improve the initial model to corelate the measured results of the SIT more properly have been performed. In this paper, the effects of the loss of concrete due to duct for tendons and the contact of duct and tendons in un-bonded tendon system are mainly evaluated based on the preliminary analysis results. In addition, the importances of the proper definition of mesh connectivity among structural elements of concrete, liner plates, rebars and tendons are discussed.

Estimation of Friction Coefficient Using Smart Strand

  • Jeon, Se-Jin;Park, Sung Yong;Kim, Sang-Hyun;Kim, Sung Tae;Park, YoungHwan
    • International Journal of Concrete Structures and Materials
    • /
    • v.9 no.3
    • /
    • pp.369-379
    • /
    • 2015
  • Friction in a post-tensioning system has a significant effect on the distribution of the prestressing force of tendons in prestressed concrete structures. However, attempts to derive friction coefficients using conventional electrical resistance strain gauges do not usually lead to reliable results, mainly due to the damage of sensors and lead wires during the insertion of strands into the sheath and during tensioning. In order to overcome these drawbacks of the existing measurement system, the Smart Strand was developed in this study to accurately measure the strain and prestressing force along the strand. In the Smart Strand, the core wire of a 7-wire strand is replaced with carbon fiber reinforced polymer in which the fiber Bragg grating sensors are embedded. As one of the applications of the Smart Strand, friction coefficients were evaluated using a full-scale test of a 20 m long beam. The test variables were the curvature, diameter, and filling ratio of the sheath. The analysis results showed the average wobble and curvature friction coefficients of 0.0038/m and 0.21/radian, respectively, which correspond to the middle of the range specified in ACI 318-08 in the U.S. and Structural Concrete Design Code in Korea. Also, the accuracy of the coefficients was improved by reducing the effective range specified in these codes by 27-34 %. This study shows the wide range of applicability of the developed Smart Strand system.

Reduced Model of the PC Segmental Multispan Bridge Constructed by Free Cantilever Method for Investigation of Deflection and Member Force (캔틸레버공법 PC 세그멘탈 다경간 교량의 처짐 및 단면력 검토를 위한 축소모델에 관한 연구)

  • Lee, Jae Hoon;Lee, Myeong-Jae
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.13 no.4
    • /
    • pp.1-13
    • /
    • 1993
  • In design of prestressed concrete structures, structural analysis is performed normally several times for selection of adequate sectional dimension and tendon amount. Especially for precast segmental multi-span bridges. time consuming structural analysis process due to time dependent material properties and structural system change could be effectively reduced by use of a reduced-span bridge model. 5-span and 3-span bridges are selected as reduced-span models for the 10-span full bridge to investigate the acceptability in practical design. The analytical results of deflection, total moment, statical moment, and ultimate moment of the reduced span-models are compared with those of the 10-span full bridge. Application of the load factors to structural analysis for ultimate moment calculation in prestressed concrete is reviewed and a rational method is proposed.

  • PDF

Development of Optimum Design Program for PPC Structures using DCOC (이산성 연속형 최적성 규준을 이용한 PPC 구조의 최적설계프로그램 개발)

  • 한상훈;조홍동;이상근
    • Computational Structural Engineering
    • /
    • v.10 no.4
    • /
    • pp.315-325
    • /
    • 1997
  • This paper describes the application of discretized continuum-type optimality criteria (DCOC) and the development of optimum design program for the multispan partially prestressed concrete beams. The cost of construction as objective function which includes the costs of concrete, prestressing steel, non-prestressing steel and formwork is minimized. The design constraints include limits on the maximum deflection, flexural and shear strengths, in addition to ductility requirements, and upper and lower bounds on design variables as stipulated by the design Code. Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables-effective depth, eccentricity of prestressing steel and non-prestressing steel ratio. The prestressing profile is prescribed by parabolic functions. The self-weight of the structure is included in the equilibrium equation of the real system, as is the secondary effect resulting from the prestressing force. An iterative procedure and computer program for updating the design variables are developed. Two numerical examples of multispan PPC beams with rectangular cross-section are solved to show the applicability and efficiency of the DCOC-based technique.

  • PDF

Transverse Stress of Slabs due tp Longitudinal Prestressing in Prestressed Concrete Box Girders (프리스트레스트 콘크리트 박스 거더의 종방향 프리스트레싱에 의한 슬래브의 횡방향 응력)

  • Yang, In-Hwan
    • Journal of the Korea Concrete Institute
    • /
    • v.15 no.5
    • /
    • pp.679-688
    • /
    • 2003
  • For box girders in which the longitudinal tendon is profiled in the inclined webs, longitudinal prestressing force will induce transverse effects as well as longitudinal ones. In this paper, the method to estimate transverse effects induced by longitudinal prestressing is proposed. The concept of transverse equivalent loading which is calculated through longitudinal prestressing analysis is developed. The transverse stress in slabs of box girders due to longitudinal prestressing are investigated. The comparison of numerical results of the proposed method and those of folded plate method represents that the method is reasonable. Numerical analyses are carried out depending on the parameters such as web inclination and ratio of girder length to tendon eccentricity. Analysis results show that when only prestressing are considered the magnitude of transverse stress in slabs of box girder is not so large. However, if the other stresses due to dead and live load et al. are superposed on these stresses, it may be that the longitudinal prestressing effects are significant.

Development of Long-Span Railway Bridges Design Using IPC Girder (IPC 거더를 이용한 장지간 철도교 설계에 관한 연구)

  • Jang, Won-Seok;Park, Jun-Myung;Park, Sun-Kyu
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.7 no.4
    • /
    • pp.149-158
    • /
    • 2003
  • It is customary that tendons and sectional dimensions are calibrated and tendon forces are applied at once at the initial stage to keep the subsequent stresses occuring at different loading stages within the allowable stresse in prestressed concrete (PSC) bridge design. However, this traditional tensioning method usually results in a too conservative sectional depth in view of ultimate capacity of a girder. A new design method which can realize the reduction of sectional depth of PSC girder is theoretically suggested in this study. Tendons are tensioned twice at different loading stages: the initial stage and the stage after fresh slab concrete is cast. It can be shown that according to this technique, sectional depth can be significantly reduced and larger span can be realized compared to traditional ones. In this paper, there is an example about the design of bridge by means of new PSC design theory, having a longer span than a existing railway bridge. Also, a new method by continuous tendon profiles is presented to be continuous a IPC bridge.