Papers by Author: S.K. Cho

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Authors: Seok Goo Youn, S.K. Cho, Eun Kyum Kim
Abstract: There is currently a need to evaluate the non-destructive techniques that are used to detect the fracture of stressed steel wires in grouted post-tensioned concrete bridges. Although continuous acoustic emission (AE) monitoring technique has been developed to detect wire breaks in unbonded tendons, it is not established as the on-site monitoring tools for grouted post-tensioned concrete bridges. In this study, AE measurements were conducted to detect corrosion-induced wire fractures inside a grouted post-tensioned beam. The test beam was drilled with 5mm drill bit to expose individual wires and a reservoir filled with corrosive solution of NaCl and NaOH was formed on the side of the beam. During the experiment, the corrosion site was anodically polarized to + 200mV using a potentiostat and it was continuously monitored and the data obtained were processed with an AE monitoring system. The outcome of this research shows that the continuous AE monitoring system successfully identified and located an individual corrosion-induced wire fracture in a fully grouted post-tensioned concrete beam.
Authors: Seung Sik Lee, Soon Jong Yoon, S.K. Cho, Jong Myen Park
Abstract: Pultruded fiber reinforced polymer (FRP) structural members have been used in various civil engineering applications. T-shapes are commonly used for chord members in trusses and for bracing members. In these cases, T-shapes are mainly subjected to axial forces, and stability of a member is one of the major concerns in the design. Due to the monosymmetry existing in the cross-section of T-shapes, T-shapes are likely to buckle in a flexural-torsional mode. An energy solution, using the Ritz method, to the buckling problem of a pulturuded T-shape under uniform compression is derived based on a composite thin-walled beam theory developed by Bauld and Tzeng. The solution accounts for the bending-twisting and bending-extension coupling effects. The derived energy solutions are compared to the experimental results of buckling tests conducted on seventeen pultruded T-shapes. It is found that the ratios of the experimental to analytical results are in the range of 1.00 to 1.32.
Authors: Jeong Hun Nam, Seung Sik Lee, Soon Jong Yoon, Won Sup Jang, S.K. Cho
Abstract: FRP composite materials are widely applicable in the construction industries as a load-bearing structural element or a reinforcing and/or repairing materials for the concrete. In this paper, we presented the flexural behavior of steel reinforced concrete beams reinforced with FRP re-bars manufactured by different fibers but the same vinylester resin. Experimental investigation pertaining to the load-deflection and load-strain characteristics of steel reinforced concrete beams reinforced with FRP re-bars with garnet coated surface is presented and the theoretical prediction is also conducted. In the investigation, the effects of FRP re-bar reinforcement in addition to the steel reinforcement are estimated. The experimental results are compared with theoretical predictions. Good agreements are observed.
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