Experimental Study On Behavior Of CFRP-high Strength Concrete Columns

Carbon Fiber Reinforced Plastic(CFRP) has been widely used in the retrofitting, repairs and strengthening of existing concrete structures due to its excellent features, such as high strength to weight ratio, superior corrosion resistance and simplicity in the application and so on. Nowadays most research interests are mainly placed on the normal concrete strengthened by CFRP. High-strength concrete strengthened by CFRP, however, should deserve much attention since high-rise, even super high-rise buildings have developed so quickly in recent years. For the sake of building techniques, mechanical properties of high-strength concrete columns strengthened by CFRP were systematically and experimentally investigated, thereafter its corresponding strengthening design method was developed. The main research work is summarized as follows.1. The application and development of technique for FPR-strengthening concrete were reviewed and summarized after much literature review from both at home and abroad.2. Mechanical properties of CFRP-strengthened high-strength concrete columns under eccentric compression were studied. For that purpose,16columns enhanced with either transverse or longitudinal CFRP were fabricated and tested to consider the influences of the eccentricity, reinforcement rate and type as well as loading history. Consequently, a computation method for enhancement was developed in accordance with the current pertinent codes.3. Mechanical properties of normal section of CFRP-reinforced concrete column under low-cycle fatigue loading were analyzed. In this study,13columns were fabricated with CFRP attached transversally or longitudinally in the tensile region and tested under tension or compression. Ultimate resistance, strain evolution and hysteretic behavior observed in the test elucidated the increase in the ultimate load of transversally confined column under tension loading. CFRP sheet longitudinally installed in tension region has preferable performance in tension failure. Nevertheless, the fact that anchorage length is not enough prohibits the full use of the tensile strength of CFRP sheet.4. Seismic behavior of high-strength concrete columns experiencing normal section failure was studied. The quasi-static experiments were undertaken on8high-strength concrete columns fully wrapped in continuous CFRP under low-cycle fatigue loading. In the meantime, other7reference columns transversally confined were used for coMParisons. In this work, several parameters were studied, the most significant being axial compression ratio, the rate and type of fiber sheet as well as the loading history. The results show that for the large eccentric compressive columns, the gain in load is rather limited, but increase in ductility and energy dissipation is obvious. For small eccentric compressive columns, however, both load and ductility gains are noticeable.5. Seismic behavior of high-strength concrete columns experiencing inclined section failure was studied. The quasi-static and low-cycle fatigue tests were conducted on11 high-strength concrete columns reinforced with CFRP sheet transversally installed, where three axial compression ratios, different reinforcement types, and damages of columns were considered. The results show a substantial increase in both resistance and ductility. Finally, one calculation formula for load-carrying capacity is recommended.6. The fatigue performance of CFRP-reinforced concrete columns was modeled using finite element analysis. CoMParison with the experiment data shows favorable agreement.