• Journal of the Korea institute for structural maintenance and inspection
• /
• v.3 no.3
• /
• pp.203-211
• /
• 1999

This study is to examine the feasibility of carbon fiber sheet(CFS), a kind of fiber reinforced plastic(FRP), for a repair and reinforcement of R/C beams. The flexural strength of R/C beams, that were preloaded and then the cracks were repaired, maintains that of the uncracked R/C beams. The flexural strength of R/C beams increases with the reinforcement of CFS. In order to practically apply the repair and reinforcement method, further research is needed for the distribution, amount, and bond of CFS. In this study, an experiment was conducted for R/C beams reinforced with CFS, for various wrapping method and amounts of CFS. Experimental results showed the wrapping method increasing the bond area and amount of CFS layer caused the increase in the strength of the beams. It is found that the strength of CFS should be used as 70% of the maximum strength in retrofitting reinforced concrete beams in evaluating flexural capacity on the basis of ultimate strength design method.

• Journal of the Korea Concrete Institute
• /
• v.17 no.1 s.85
• /
• pp.113-120
• /
• 2005

The purpose of this study is to investigate the strength and ductility improvement of columns retrofitted by steel-fiber composite plate. Test specimens strengthened by three different materials - steel plate(SP), carbon fiber sheet(CF) and fiber-steel composite plate(CP) - were tested under cyclic lateral load with a constant axial load equal to $20\%$ of the axial compression capacity. The structural capacity of composite plate was good or better than that of other retrofitting materials. Test results from all retrofitted specimens showed that considerably higher retrofitting amount was required for strength enhancement. The ductility of retrofitted columns by composite plate was fairly improved. Also, energy ductility ratio was more effective than displacement ductility ratio for ductility estimation of retrofitted column.

• Journal of the Korea Concrete Institute
• /
• v.19 no.6
• /
• pp.795-802
• /
• 2007

Recently, various strengthening methods using carbon fiber sheets (CFS) have been developed for the rehabilitation of structures and applied to the concrete member. However, still research need arises in order to verify the structural capacity of RC member which experienced bond loss between concrete and CFS after strengthening. This is because previous research has focused on the development of design process and evaluation of structural capacity only for retrofit. The appearance of this loss may be initiated at just after retrofit construction. And it will be more serious when the layer number of CFS increases. In order to minimize above mistake in retrofit design using CFS, more exact evaluation process to predict the bond loss of CFS is required. The objective of this research is to study the variation of flexural structural capacity of beam which has experienced bond loss after strengthening using CFS. Experimental and analytical study are performed and evaluation of the previous formula is conducted. Test result showed that the significant strength deterioration was not found until the bond loss of 20%. Overall structural behavior of the beams can be predicted by nonlinear sectional analysis.