• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.668-676
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• 2002

Especially, when orthotropic material such as uni-dierectionally woven Carbon Fiber Sheet, resisting only the unidirectional tension, is used to strengthening bridge deck, the direction and width of the strengthening material should be considered very carefully. Thus, analysis of the failure characteristics and the premature failure mechanism of the strengthened decks based on the test results are required. In this study, the premature failure due to the interface debonding of strengthening material of the strengthened deck slab are inquired into failure mechanism through both experiments results and analyses with prototype strengthened deck specimens using carbon fiber sheet. From the test results, interface debonding of strengthening material is occured at the crack face

• Coupled systems mechanics
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• v.9 no.4
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• pp.359-379
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• 2020

Due to susceptibility of bridges in the past earthquakes, vulnerability assessment and strengthening of bridges has gained a particular significance. The objective of the present study is to employ an analytical method for the development of fragility curves, as well as to investigate the effect of strengthening on the RC box-girder bridges. Since fragility curves are used for pre-and post-earthquake planning, this paper has attempted to adopt the most reliable modeling assumptions in order to increase the reliability. Furthermore, to acknowledge the interaction of soil, abutment and pile, the effect of different strengthening methods, such as using steel jacketing and FRP layers, the effect of increase in the bridge pier diameter, and the effect of vertical component of earthquake on the vulnerability of bridges in this study, a three-span RC box-girder bridge was modeled in 9 different cases. Nonlinear dynamic analyses were carried out on the studied bridges subjected to 100 ground motion records via OpenSEES platform. Therefore, the fragility curves were plotted and compared in the four damage states. The results revealed that once the interaction of soil and abutment and the vertical component of the earthquake are accounted for in the calculations, the median fragility is reduced, implying that the bridge becomes more vulnerable. It was also confirmed that steel jackets and FRP layers are suitable methods for pier strengthening which reduces the vulnerability of the bridge.

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.213-220
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• 2004

This paper deals with an enhanced structural capacity of reinforced concrete bridge deck strengthened with carbon fiber rod (CFR) which is subjected to monotonic and cyclic loads. Strengthening variables considered in this test were evenly and unevenly strengthening type. To evaluate strengthening capacity for these two strengthening types, load-carrying capacity and crack and failure pattern from the failure test were analyzed and fatigue response were examined. According to the test results, all the strengthened specimens showed punching shear failure as a result of premature failure of bonding interface between mortar and concrete. In the case of strengthening capacity, it was observed that the strengthened specimens was more effective in strength, stiffness and fatigue endurance limit than the unstrengthened specimen. In addition, the unevenly strengthening method (CR-UE) was more effective than the evenly strengthening method (CR-E).

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.555-564
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• 2013

An effective method was proposed in this study which can improve the strengthening effect of continuous girder bridges by external tendons. The improvement of the proposed strengthening method in comparison with conventional methods was analyzed by applying equivalent load concept. In order to verify the strengthening effect, the enhancement of load-carrying capacity achieved by external prestressing was investigated through the test of continuous beams that were or were not strengthened by the external prestressing. The continuous beams were fabricated by making the deck slab continuous according to general construction practice of an actual concrete girder bridge. The test results showed that the deflections and strains of the strengthened beam were significantly reduced when comparing with those of the non-strengthened beam for the same level of external loads, and the stiffness of the member increased by strengthening. In particular, it was verified that the proposed method can effectively reduce the tensile stresses of the deck caused by negative moment at the intermediate supports of a continuous bridge.

• 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.

• PNF and Movement
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• v.19 no.3
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• pp.321-329
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• 2021

Purpose: The abdominal drawing-in maneuver (ADIM) is an exercise that selectively strengthens deep abdominal muscles. It is reported to be effective in strengthening those muscles when using a pressure biofeedback unit. However, multiple factors of bridge exercise seem to bring exercise result of ADIM without stabilizer as they influence execution of ADIM. Therefore, the purpose of this study was to compare changes in the thickness of deep abdominal muscles through the ADIM exercise incorporating either a stabilizer or the bridge exercise. Methods: Thirty healthy adults who had voluntarily given their consent were selected as the subjects. A diagnostic sonograph was used to measure the thickness of the subjects' transverse abdominis, internal oblique, and external oblique muscles. First, the thickness of the subjects' deep abdominal muscle was measured while maintaining the ADIM using the stabilizer. After three minutes of rest, the thickness was measured again while the subjects maintained the ADIM with the bridge exercise. Results: In both exercises, the thickness of the transverse abdominis showed a statistically significant increase, with a more significant increase while executing the ADIM using the bridge exercise. In both exercises, the thickness of the internal oblique showed a statistically significant increase, with a more significant increase while executing the ADIM using the bridge exercise. The thickness of the external oblique showed a statistically significant increase only in the ADIM using the bridge exercise. Conclusion: Though strengthening is not as selective as the ADIM using a stabilizer, the ADIM using the bridge exercise has a more increased thickness of the transverse abdominis and the internal oblique than that of the internal oblique. Based on the outcome of this study, the ADIM using the bridge exercise without a stabilizer can selectively strengthen deep abdominal muscles even more.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.827-832
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• 1998

Recently, Carbon Fiber Sheets(CFS) have been used for strengthening the deteriorated RC beams and bridge decks because of its resistant capacity of corrosion and easy repairing works. In this study, the static test tare performed on RC bridge decks strengthened with CFS. Test results show that ultimate strength of specimens strengthened with CFS is increased as 15~26% comparing to the control specimen.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.3
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• pp.39-51
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• 1983

Increasing of load on the highway bridge necessitate the strengthening of load capacity of bridge by some method. The method of strengthening is the usage of pre-stressing high tensile steel line. Having finished pre-stressing work, line is anchored both end, then it composed a member of bridge structure when loading. This paper includes the method and mechanism of strengthening of I-beam span(same originality of plate girder), could be summerized as following; (a) Simple girder, 2 span and 3 span continuous girder increasing the load capacity by more than 80 % for concentrated load. (b) For uniformly distributed load, when all span loaded, load capacity is increase more than 80% to 100% except 3 span continuous.

• Magazine of the Korea Concrete Institute
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• v.7 no.6
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• pp.38-49
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• 1995

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.383-386
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• 2000

In this study, strengthening effect of the deteriorated reinforced concrete T type bridge with epoxy-bonded glass fiber reinforced plates(GFRP) is experimentally investigated. This test make a comparison between before strengthened and after strengthened with GFRP structural behavior experimentally in the field. the results generally indicate that the flexural strength of strengthened RC T-type bridge is increased.