• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.289-297
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• 2012

This study proposes an experimental formula that can estimate the applied tensile stress of a bonded PSC by measuring a longitudinal stress wave velocity of tendon. To develop practical formula, the various bonded PSC specimens are constructed with different levels of prestresses. For all the bonded PSC specimens, the longitudinal impact-echo tests are repeated with various experimental conditions. Considering a few influence factors such as temperature, length and the number of strands, the application of the law of similarity results in a nondemensional experimental formula that could estimate existing tensile stress on tendon by measuring its longitudinal stress wave velocity. Next, a feasibility study of proposed approach has been conducted for a real reactor building containment. The estimated stress levels of two vertical tendons embedded in the nuclear plant are close to their design values.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.419-429
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• 2009

This study focuses on the effect of the cutting order of prestressing strands on the strain change in the strands and on the state of stress of concrete, experimentally and numerically. In the experiment, strain of strands and of transversal reinforcement were measured for three different cutting orders during detensioning process by using flame-cutting procedure. The experimental results were compared with those obtained from the FE analysis. As a results of the experiment, it is confirmed that the cutting order of prestressing strands affected on the strain of strands as well as of transversal reinforcement. The FE analysis gave similar results to those obtained from the experiment. Therefore, the cutting order should be chosen appropriately to when the strands get detensioned.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.151-158
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• 2002

Recently, the externally prestressed unbonded steel I-beam bridges have been increasingly built. The mechanical behavior of prestressed steel I-beams which are with external unbonded tendon is different from that of normal bonded PSC beams in a point of that the slip of tendons at deviators and the change of tendon eccentricity occurs, when external loads are applied in external unbonded steel I-beams. The concept of prestressing steel structures has not been widely considered, in spite of long and successful history of prestressing concrete members. In this study, The field experiment on prestressed steel I-beams has been performed in the various aspects of prestressed I-beam including the tend on type and profile.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.261-267
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• 2011

This study reveals the longitudinal vibration mechanism of tendon embedded in a prestressed concrete. The extensional and torsional displacements of the strand are coupled, and the applied prestress level of tendon affects not only axial rigidity but also torsional rigidity. Measuring the elastic wave velocity of tendon, the applied prestress level of tendon could be evaluated. This is because the elastic wave velocity is a function of extensional and torsional rigidity. Using the experimental results for the six prsteressed concrete beams with different prestress levels, the longitudinal vibration mechanism and the effect of prestress level have been examined. To estimate the system ridigities of tendon, a system identification algorithm has been newly developed. The estimated system rigidities have been compared with the available results of related previous study.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1999.06a
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• pp.163-168
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• 1999

Post-Tensioning System은 강선(Strand)을 긴장하여 콘크리트 부재에 미리 압축력을 주어 응력을 도입시키기 위한 텐던(Tendon)과 정착구(Anchorage)의 조합체계로서 이루어진다. 여기서 텐던이란 와이어, 스트랜드, 바아등의 긴장재의 하나 혹은 여러개의 묶음을 의미하며, 정착구란 긴장된 텐던에 발생된 힘을 지탱하여 그 힘을 콘크리트에 전달해 주는 기계적 장치를 말하며 콘과 Wedge로 구성된다. (중략)

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.165-176
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• 2006

This paper deals with the experiment and construction case of concrete beams strengthened with wire rope using the tightening force of bolts. The mechanical bolting of wire rope for prestressing force is adopted, which is very easy for construction. For the flexural strengthening effect of the proposed method, the experiment was proceeded as follows. The main parameters of specimens, concrete strength is 24MPa, are initial prestressing forces of wire rope and the number of saddle. The flexural strengths of strengthened specimens compared with non-strengthened test piece were increased about 160%. Also, as the initial prestressing forces were increased, the crack and ultimate moments were increased. The number of saddle did not play an important role for the moment capacity. This proposed method as a construction example showed a more competitive method than any others.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.341-344
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• 2008

In this paper, the effect of flame cutting order of tendons on the concrete stress was investigated experimentally. For this, the three slab specimens with 14 tendons were cast and tested. During the detensioning, the longitudinal and transversal strain were measured. Test results showed that the measured strains of transversal stirrups were varied by the cutting order.

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.737-742
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• 2006

Strengthening concrete structures with fiber reinforced polymer materials have grown to be a widely used method over most parts of the world today, which FRP was developed in 1960. A method to apply prestressing force to FRP is developed newly in these days, which can use the maximum performance of FRP materials. This paper presents the results of a study on improvement in flexural capacities of RC beams strenthened with near surface mounted prestressed CFRP rod and plate. Experimental variables include type of CFRP, prestressing level. Tests show that prestressed beams exhibit a higher crack-load as well as a higher steel-yielding load compared to non-prestressed strengthened beams.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.329-336
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• 2010

An experimental study to evaluate bursting behavior in anchorage zone of the standard PSC I girders (span length : 30 m) has been carried out. The arrangement of bursting reinforcement in anchorage zone of the standard PSC I girders is considered to be designed without accurately reflecting the stress flows in the end zone of the PSC I girders caused by presstressing forces of the tendons. Also, due to excessive arrangement of the bursting bars, the workability of the girder is decreased greatly. In this study, three specimens with the same dimensions as the end zone of the standard PSC I girder are prepared and the experiment is carried out by applying PS forces. The bursting reinforcement of each specimen consists of 100 mm, 200 mm, and 300mm spacings, respectively. The experimental results show that the range of the PS forces to cause crack in the anchorage zone of the specimen are more than 1.6 times of the design PS forces. The bursting cracks occur in the vertical direction on the inside of all specimens. After applying 2.7 times of the design PS force, some of the transverse bursting reinforcements only in the specimen reinforced by 300 mm spacing yielded. The experimental results show that the anchorage zone of the standard PSC I girders arranged by 300 mm spacing of the bursting reinforcements which is the maximum spacing allowed in the road bridge design specifications, can be considered safe enough.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.349-352
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• 2008

IPC girder is more prestressed and has smaller sectional area than the conventional PSC-I type girder due to incremental prestressing along the construction process. The continuous IPC girder bridge may have problems in serviceability and stresses at internal supports because it is very flexible. In this paper, The long-term behavior of the continuous IPC girder bridge is studied through long-term structural analysis and monitoring the deflections. The long-term behavior is monitored right before the introduction of 2nd prestressing that is the construction process different from the conventional PSC-I type girder bridge. The total station of high-precision was used in measuring the deflections. According to the monitoring result so far, the continuous IPC girder bridges does not show remarkable long-term behavior like severe camber or deflection and the measured deflections are very similar to the results of long-term structural analysis.