• 발명특허
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• v.33 no.7
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• pp.68-71
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• 2008

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.123-134
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• 2007

A method to determine the initial force of external tendon is proposed to improve the load carrying capacity in existing steel-concrete composite bridges. This method is applied to tensioning external tendons prior to and after concrete replacement for strengthening composite girders. A procedure to determine the number of tendon and initial tendon force is described with the proposed rating factor, which considers the increment of tendon force due to live loads. The method is applied to the improvement of rating factor in an existing composite bridge and its validity is confirmed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.102-110
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• 2006

This paper examines experimentally the ultimate behavior of I-type steel beam strengthened with external tendon and cylindrical anchorage and analyzes the strengthening effect on the parameters such as initial tendon force, eccentricity, number of strands, and strand areas. The experiment demonstrated that increasing the number of strands, strand areas and eccentricity is more effective than increasing initial tendon force. The proposed cylindrical anchorage system has advantages in applying these parameters. The results showed that the cylindrical anchorage system is efficient and applicable to strengthen steel beam.

• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.549-558
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• 2000

In strengthening structure, the external post-tensioning method which secure clearness in the structure analysis process is adopted to bridges as well as architecture structure. In this study, to investigate the behavior of composite beam in the process of post-tensioning, the amount of prestress force loss, the amount of prestressed compression stress at the lower flange and the behavior of lower flange connected with anchorage are analyzed by comparing the results of finite element analysis with the measured results of installed strain gauges. After finishing the post-tensioning, the strengthening effect of external post-tensioning method is analyzed by static loading test. It is also investigated that the strengthening effect of shear section in the harped external post-tensioning specimens.

• Magazine of the Korea Institute for Structural Maintenance and Inspection
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• v.18 no.2
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• pp.36-42
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• 2014

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.222-229
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• 2022

The extensive use of external prestressing system with PSC-I beam to strengthen reinforced and prestressed concrete members requires the full understanding of the behavior of the strengthened members. The main approach of this research was to experimentally investigate the flexural performance of the PSC-I beam considering external tendon and an equation was developed which indicated the produced incremental stress in the tendon due to applied load. Further, this equation was verified through performing static loading tests on two experimental specimens considering the presence or absence of external tendon. The test results revealed that, the flexural performance enhanced due to the use of external tendon. Moreover, the magnitude of the estimated flexural strength using proposed stress increasing equation almost coincides with the experimental test results. However, it was the evident of the improvement of the flexural performance of the system by reinforcing with the external tendon and also proved that the proposed equation was valid and effective.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.439-445
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• 2008

This paper suggests a modified bond reduction coefficient considering the average CFRP (Carbon Fiber Reinforced Polymer) strain concept for the unbonded prestressed CFRP plate strengthening system. The strengthened length and the pure bending length were seen to influence the variation of the strain of unbonded CFRP plate. Therefore, a new bond reduction coefficient considering such effect was suggested. Comparison with the experimental data revealed that the analytic results obtained by considering the proposed bond reduction coefficient were effective in estimating the strain of the unbonded CFRP plate in the CFRP plate prestressing system.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.136-149
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• 2011

Large portion of the domestic bridges are slab bridges reflecting the geographical characteristic of the country, where exists lots of inclines and small winding brooks. Many of the slab bridges are damaged and superannuated as they become obsolete. Deterioration is accelerated when the traffic density becomes large and heavy vehicles pass frequently. A strengthening method for deteriorated slab bridges was studied in this work. The examined net-type strengthening method uses both longitudinal and transverse prestressing for strengthening. In this way, the deflection at the center of the slab can be better controlled, and consequently, the slab is more efficiently strengthened. Three slab specimens were fabricated for the experimental test and subjected to three different loading conditions, and the load bearing capacities and deflections of slabs were examined. Flexural stiffness of slabs increased by 30.7~107.3%, and deflection of slabs decreased by 27.6~52.2% after net-type strengthening. The net-type prestressing is efficient to the strengthening for the center of a slab, and its efficiency is also valid under eccentric loadings. Since extra prestress forces can be added in the future, if necessary, the net-type strengthening system is advantagous for the maintenance and repair of slab bridges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3A
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• pp.315-322
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• 2008

The present study applied the external post tensioning reinforcement method for reinforcing a non-ballast steel plate girder railway bridge, and the effects of the strength of tendons and the level of post-tensioning force on the dynamic behavior are experimented and analyzed. According to the results of this study, the natural frequency was increased by the strength of tendons but it was decreased by the rise of post-tensioning force and as a consequence the introduction of post-tensioning force decreased natural frequency slightly. It was analyzed that further study is need to establish the exact relations between post-tensioning force and natural frequency. In addition, it was found that the dynamic displacement, dynamic bending stress and vertical acceleration were decreased by the external post-tensioning. On the other hand, external post-tensioning increased horizontal acceleration by up to 20%, which was around 70% of vertical acceleration. This needs further study.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.685-688
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• 1999

The analysis and design of composite girders prestressed by external tendons involve difficulties related to the position of anchorages and the construction sequences. In this paper, the efficiency of the external tendon profiles and the position of anchorages in examined for the internal and external prestressing of statically indeterminate structures. It is shown that strengthening of a prestressed girder can be accomplished using a variety of methods; bonded external prestressing, tendon replacement and unbonded external prestressing.