Kyusan Jung

Prediction of Flexural Capacity of RC Beams Strengthened in Flexure with FRP Fabric and Cementitious Matrix

This paper presents both experimental and analytical research results for predicting the flexural capacity of reinforced concrete (RC) beams strengthened in flexure with fabric reinforced cementitious matrix (FRCM). In order to assess the efficiency of the FRCM-strengthening method, six beams were strengthened in flexure with FRCM composite having different amounts and layers of FRP fabric and were tested under four-point loading. From test results, it was confirmed that the slippage between the FRP fabric and matrix occurs at a high strain level, and all of the FRCM-strengthened beams failed by the debonding of the FRCM. Additionally, a new bond strength model for FRCM considering the slippage between fabric and matrix was proposed, using a test database to predict the strengthening performance of the FRCM composite. The prediction of the proposed bond strength model agreed well with the debonding loads of the test database.

Shear Strengthening Performance of Hybrid FRP-FRCM

The effectiveness of a hybrid fiber reinforced polymer- (FRP-) fabric reinforced cementitious matrix (FRCM) for shear strengthening was investigated though an experimental study. FRP materials of FRCM are usually fabricated in the form of a fabric to enhance the bond strength between the FRP material and the cementitious matrix. The hybrid FRP fabric used in this study consisted of carbon FRP (CFRP) and glass FRP (GFRP) in warp and weft directions, respectively. A total of 11 beams were fabricated and 8 beams among them were strengthened in shear with externally bonded hybrid FRP-FRCM. The number of plies, the bond types, and the spacing of the hybrid FRP fabric were considered as experimental variables. Additionally, a shear capacity model for a FRCM shear strengthened beam was proposed. The values predicted by the proposed model were compared with those by the ACI 549 code and test results. It was confirmed from the comparison that the proposed model predicted the shear strengthening performance of the hybrid FRP-FRCM more reliably than the ACI 549 code did.

Finite element analysis of RC beam strengthened with FOS embedded carbon fiber sheet

The method of reinforcing the structure by attaching the carbon fiber sheet started from the mid 1980s in EMPA in Switzerland. The research has been utilized in reinforcing many structures from 1990. The carbon fiber sheet adhesion reinforcing method is often difficult to completely adhere due to various reasons, and may fall off or peel off with the lapse of time. When reinforcement performance of a structure strengthened with a carbon fiber sheet decreases due to peeling of adhesion. Survey of many damage cases and theoretical study on the effect of detachment or peeling of carbon fiber sheet to the performance of the structure are needed to provide concrete solutions. This study analyzed the relationship between the separation of carbon fiber sheet and the performance of structures reinforced by carbon fiber sheet attachment method.

Experimental investigation on the FOS embedded carbon fiber sheet for bridge sensing and reinforcement

Carbon fiber sheet surface adhesion method is a well-known repair and reinforcement method for concrete structures like bridges and buildings. The method has high tensile strength and durability. However, the attached sheet is easy to detached from the structure during and after the construction because of the method’s labor intensive characteristics. An accurate measurement and evaluation system of damage location needed to identify the type of damages. In this study, a conceptual design of fiber optic sensor embedded carbon fiber sheet was developed to track the measured signal by deflection of the samples using BOTDR. After the analysis of the measured value, it verifies the applicability of the optical fiber embedded carbon fiber sheet to check the state of a reinforced structure.

Flexural Behavior of RC Slabs Strengthened in Flexure with Basalt Fabric-Reinforced Cementitious Matrix

This paper presents both experimental and analytical research results for predicting the flexural capacity of reinforced concrete (RC) slabs strengthened in flexure with basalt fabric-reinforced cementitious matrix (FRCM). A total of 13 specimens were fabricated to evaluate the flexural behavior of RC slabs strengthened with basalt FRCM composite and were tested under four-point loading. The fiber type, tensile reinforcement ratio, and the number of fabric layers were chosen as experimental variables. The maximum load of FRCM-strengthened specimens increased from 11.2% to 98.2% relative to the reference specimens. The energy ratio and ductility of the FRCM-strengthened specimens decreased with the higher amount of fabric and tensile reinforcement. The effective stress level of FRCM fabric can be accurately predicted by a bond strength of ACI 549 and Jung’s model.