• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.441-455
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• 1997

The need for rehabilitation of the existing bridges is a growing concern in many countries and has been emphasized in various research reports and publications. Many bridges constructed between 1960s and 1970s in Korea were designed for relatively light traffic volumes, speeds and the weight, thus they are inadequate for the present traffic conditions. This together with some design deficiencies, has resulted in deficiencies of various degrees of many bridges. One strengthening method which has significant advantages is the application of external post-tensioning tendons. This paper presents an example of three span continuous composite bridge strenghtened by application of external post-tensioning.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.483-490
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• 2007

Traditional external post-tensioning method using either steel bars or tendons is commonly used as a retrofitting method for concrete bridges. However, the external post-tensioning method has some disadvantages such as stress concentration at anchorages and inefficient load carrying capability regarding live loads. Thermal prestressing method is a newly proposed method for strengthening and rehabilitation of concrete girder bridges. Founded on a simple concept of thermal expansion and contraction of steel, the method is a hybrid method of external post-tensioning and steel plate bonding, combining the merits of two methods. In this paper, basic concepts of the method are presented and an illustrative experiment is introduced. From actual experimental data, the thermal prestressing effect is substantiated and the FEM approach for its analysis is verified.

• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.238-241
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• 2006

The needs for strengthening and rehabilitation of the concrete bridges are a growing concern in many countries and has been emphasized in various researches and papers. Traditional external post-tensioning method using either steel bars or tendons is commonly used as a strengthening method. However, the method has some disadvantages such as stress concentration at the anchorages. Multi-stepwise thermal prestressing method is a newly proposed method for strengthening and rehabilitation of concrete girder bridges. Founded on a simple concept of thermal expansion and contraction of steel, the method is a hybrid method of external post-tensioning and steel plate bonding, combining the merits of two methods. In this paper, basic concepts on strengthening and rehabilitation of concrete girder are presented and an illustrative experiment is introduced.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.157-163
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• 2003

Recently, the number of Prestressed Concrete(PSC) bridges needed repair and retrofit because of the increase of heavy traffic loads and aging of concrete materials. But there are a few related researches about strengthening PSC bridges. In this study, the practicability of strengthening methods for PSC beam were studied by the static experimental method. PSC beams in length of 6m were made with concrete slabs. Glass fiber sheeting and external post-tensioning methods were used for strengthening PSC beams. Some beams were strengthened after cracks to investigate the applicability for cracked bridges. As a result, there strengthening methods were efficient at increasing the cracking loads and the failure load, to decrease deflection and prevent cracks. In the case of using glass fiber retrofit methods, it should be careful in the anchorage problems for preventing the bonding failure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.165-172
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• 2003

The fatigue problem of Prestressed Concrete(PSC) bridges are more serious than the other type of concrete bridges, because the cross sectional area and self weight of PSC bridges are smaller. The endurance of strengthening methods for PSC bridges are tested in this study. Glass fiber sheeting and external post-tensioning methods were applied. 1/5 scale PSC beams were made for fatigue test, same as static test. The range of repeated load is from 10% to 80% of yielding load with sine curve. The experimental results show that the failure cycle of strengthened members are increased compare to non-strengthened members. The members strengthened with glass fiber show better enhancement in fatigue problem than the members strengthened with external post-tensioning method, though the adhesion of glass fiber and concrete is failed, as increase of crack. With these experimental results, it can be said that the strengthening methods used in this study are efficient at extending the life time of aged PSC bridges.

• Proceedings of the KSR Conference
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• 2006.05b
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• pp.594-604
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• 2006

• 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.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.717-726
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• 2006

Traditional external post-tensioning method using either steel bars or tendons is commonly used as a retrofitting method for steel composite bridges. However, the method has some disadvantages such as stress concentration at anchorages and inefficient load-carrying capability of live loads. Multi-stepwise prestressing method using thermal expanded coverplate is a newly proposed prestressing method, which was originally developed for prestressing steel structures. A new retrofitting method for steel girder bridges founded on a simple concept of thermal expansion and contraction of cover plate, the method is a hybrid of and combines the advantages of external post-tensioning and thermal prestressing. In this paper, basic concepts of the method are presented and an illustrative experiment is introduced. From actual experimental data, the thermal prestressing effect was substantiated and the FEM approach for its analysis was verified. The retrofitting effects ofa single-span bridge were analyzed and the feasibility of the developed method was examined.

• KCI Concrete Journal
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• v.12 no.1
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• pp.17-22
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• 2000

This Paper deals with the analysis of both unstrengthened and strengthened prestressed concrete girder bridges. Finite element method is utilized to perform the analysis of superstructures. Based on the grillage method of analysis. emphasis is Placed on the modeling techniques for structures. The conventional grillage method of analysis is modif'=ed so that the interaction between the slab and gilder behaviors can be taken into account in the analysis A Prototype of simply supported prestressed I-type girder bridge is selected for the analysis. The results of numerical analyses are compared with those of load test. The results of analysis indicate that the proposed method of analysis gives more realistic response of bridges than the conventional grillage method.