| Fiber-Reinforced Polymer (FRP ) have received significant attentions for use in civil infrastructure due to their unique properties, such as the high strength-to-weight ratio and stiffhess-to-weight ratio, corrosion and fatigue resistance, and tailorability. It is well known that FRP wraps increase the load-carrying capability and the ductility of reinforced concrete columns. However, the behavior of FRP wrapped RC columns is not yet fully understood, and the design code is still not available at this time. This study is intended as a step towards improving this status. It is consist of six parts:1. When circular concrete column is confined effectively by lateral pressure, its strength and ductility can be greatly enhanced. It is convenient and reliable to confine concrete by bonding GFRP sheets. In practical design, an appropriate analytic model should be given to assure reliable results. Previous models generally lead to overestimate of the strength of FRP and result in unsafe design. In this paper, experiments on 27 (9 groups) concrete circular columns are conducted. Based on reported test results, a bilinear stress-strain relationship model is provided, and good agreement is achieved between test results and theoretical ones.2. When square concrete columns are strengthened with bonding GFRP sheets, lateral pressure of core concrete is not uniform. Pre-failure of GFRP sheets often occur because of stress concentration on the corner of columns. So strength and ductility is lower than that of confined circular columns, and its calculation and analysis are more troublesome than that of circular ones. In this paper, experiments on 51 (17 groups) square columns are conducted. Based on reported test results for GFRP-conflned concrete, a simplified analytic method and a two-stage stress-strain relationship model is provided, and good agreement between test and theoretical results is achieved.3. Almost all previous experimental study and theoretical analysis focused on concrete columns subjected axial loading, but study on concrete columns under eccentric loading is scarce. In engineering practice, almost all columns subject eccentric loading. In order to know the behavior of FRP jacketed reinforced concrete columns under eccentric loading, it is essential to do some special study on it. In this paper, experiments on 10 full size rectangular reinforced concrete columns strengthened with glass fiber-Reinforced Polymer are conducted. In this test, various design parameters, such as eccentricity ratio, quantity of unidirection continuous glass-fiber sheets, space of straps and loading history, are been considered. Based test results and applicable codes,authors provide an analysis method and good agreement between test and theoretical result is achieved.4. The effectiveness of bonding GFRP sheets to retrofit reinforced concrete columns for enhanced shear strength is described in this paper. Ten reinforced concrete columns were tested under cyclic shear and constant axial load. Two columns were tested in the "as built" condition to investigate the shear failure modes of columns under deferent degree of axial load. Eight other columns were pre-damaged and tested after retrofitted with bonding GFRP sheets. The as built columns suffered shear failure at low strength and displacement ductility. Shear strength and hysteretic responses of the retrofitted columns were improved significantly. Based on reported test results for GFRP-confmed concrete, one calculation method is provided, and good agreement between test and theoretical results is achieved.5. The effectiveness of bonding GFRP sheets to retrofit reinforced concrete columns for enhanced flexural strength is described in this paper. Eleven reinforced concrete columns were tested under cyclic lateral load and constant axial load. Three columns were tested in the "as built"' condition to investigate the failure modes of columns under deferent degree of axial load. Eight other columns were pre-damaged and tested after...
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