• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.701-708
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• 1998

The application of additional post-tensioning tendons has recently been widely considered and requires very little interference with the existing structure. Several bridges on the national roadway designed as the second class were strengthened by external post-tensioning for the capacity enhancement purpose, but much of that strengthening work was not verified analytically as well as experimentally. This paper examines experimentally the behavior of simple composite steel-concrete beams designed as the second class(DB-18) When they are strengthened with external post-tensioning tendon. Test results show that external post-tensioning increases the ultimate load and the magnitude of tendon force increases the yield load but not the ultimate load.

• 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.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6A
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• pp.587-596
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• 2009

This study analyzes the lateral distribution behavior of external post-tensioning force and evaluates the possibility of strengthening the servicing composite girder bridge by adopting the external post-tensioning force to the parts of the bridge girder. From the results of experiments and analyses, it is founded that the composite girder bridge can be strengthened by applying the external post-tensioning force to the parts of the bridge girder. It is also proved that bracing improve the lateral distribution behavior of post-tensioning force. The lateral distribution behavior of post-tensioning force which influenced by stiffness ratio, girder spacing and span length is changed by the bridge type and the location of tensioned girder. From the results of analyses, set up an equation which can predict the lateral distribution behavior of external post-tensioning force and evaluate the rationality.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.1-6
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• 2021

Concrete structures gradually age due to deterioration of materials or excess loads and environmental factors, and their performance decreases, affecting the usability and safety of structures. Although external tension construction methods are widely used among the reinforcement methods of old bridges, it is insufficient to identify the effects and effects of reinforcement depending on the level of aging. Therefore, in this study, a four-point loading experiment was conducted on the subject with the non-reinforced and external tensioning method to confirm the reinforcement effect of the external tensioning method, assuming the aging of the structure as a reduction in the compressive strength and tensile reinforcement of concrete, to analyze the behavior of the reinforcement and confirm the reinforcement effect. As a result of the experiment, it was difficult to identify the amount of reinforcement in the extreme condition due to early elimination of the anchorage. Therefore, compliance with the regulations on anchor bolts is required when applying the external tension reinforcement method. Crack load and yield load increased depending on whether external tension was reinforced, but before the crack, the stiffness before and after reinforcement was similar, making it difficult to confirm the reinforcement effect.

• 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.

• Computational Structural Engineering
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• v.13 no.4
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• pp.33-41
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• 2000

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.169-178
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• 2010

In this study, the optimal strengthening by micro genetic algorithm(${\mu}$-GA) method is proposed for improvement of load-carrying capacity of RC hollow slab bridges using external prestressing. The Qeen-post type and King-post type are considered for the optimal strengthening. The type for optimal strengthening, deviator, areas of tendons and the number of anchor are calculated by ${\mu}$-GA. The objective function is constituted with dimensionless cost of tendon and steel for optimal strengthening. The constraints are formulated by design specification for bridges and anchors. The validity of this study is presented by analysis of the results after the optimal strengthening of the RC hollow slab bridge.

• 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.9 no.3
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• pp.178-186
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• 2005

In this study, the PSC girder bridge retrofitted with external tendons is tested to verify the strengthening effects. We measure the variations of the displacement and strain at mid-span of each beam as external tendons are removed in sequence. The structural behavior of the bridge are examined using controlled truck load tests for the systems before and after all external tendons were removed. From the test results, the characteristics of structural behavior of the bridge do not change significantly, but the natural frequency is decreased after the external tendons are removed. The strengthening effects of bridges can be exactly estimated by analytical methods some extent. As a result of this study, when a PSC girder bridge is deteriorated, the bridge can be retrofitted effectively by External Prestressing Strengthening Method, and the strengthening effects can be predicted through accurate structural analysis.