• 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.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.675-682
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• 2011

Recently, in retrofit of RC structures using FRP (Fiber Reinforced Polymer), researches about Near-Surface-Mounted Rertofit (NSMR) method have been widely performed. In NSMR, FRP bar is normally inserted in the slit formed in the cover concrete and then bonded by using epoxy mortar. In this paper, the bond characteristic of NSMR using FRP plate instead of bar was studied experimentally. Fracture behavior is observed from bond test using the parameters of embedment length, shear key, and FRP plate layer. In addition, an equation to predict the splitting strength of NSMR using FRP is proposed using the test result. The results showed that when the longer embedment length and more layers of FRP are used, the higher bond strength is achieved. There was a good co-relationship between the test and calculated results using the proposed equation.

• Magazine of the Korea Concrete Institute
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• v.3 no.2
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• pp.115-121
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• 1991

Slippage of beam longitudinal reinforcement at beam-column connections is an important cause of damage to reinforced concrete frames under static and dynamic loads, This paper summarizes the results of an experimen¬tal study on the effects of confinements and compressive strength of concrete on the local bond stress-slip cha¬racteristics of deformed bars. I t is concluded from experimental results that, as far as the bond splittmg cracks are restrained by the vertical column reinforcement, confinement of concrete by transverse reinforcement has insignigicant direct effect on the local bond behavior. The ultimate bond strength, however, Increases pro¬portionally with the square root of concrete compressive strength. An empirical model was developed for local bond st ressslip relationslip of deformed bars in confined concrete of different compressive strengths.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.431-438
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• 2006

The determination of the depth of deteriorated concrete is one of the main problems in the structural assessment of concrete structures that have been subjected to a fire. This information is particularly important in order to optimize the future operations of repair/strengthening, or in decision-making concerning a possible demolition. The purpose of this study is to propose evaluation technique of damaged depth of concrete exposed at high temperature. In order to evaluate damaged depth of core picked at member under fire, the 24 specimens have been made with variables of concrete strength(20 MPa, 40 MPa, 60 MPa) and heating exposure condition in 600 and 800 for 2 hours. Color change analysis and water absorption after heating have been measured and split tensile stress test was performed to ka the residual compressive strength against the depth of specimen. The results show that the deeper of the depth from heating face, water absorption ratio is smaller and residual stress ratio is larger and the color of heated face is changed to red color. Using this technique at damage evaluation of fired structure, We evaluate damaged depth of member under fire and determine the reasonable strengthening range.