Mechanical Behavior Of FRP Reinforced Concrete Structure

The new materials of Fiber Reinforced Plastic (FRP) has good prospects in civil engineering due to the excellent properties of high tensile strength(about3000MPa), lightweight(about1/8of steel’s weight), easy installation and nocorrosion. At present, the researchs about creep behavior and fatigue performance of concrete structures strength by FRP sheets, and behavior of concrete beams prestressed with external tendons is limitedAn experimental study and the corresponding theory analysis are conducted to investigate the behavior of concrete structures strength with FRP sheet. This dissertation involves the following work:(1) the behaviors of8RC beams strengthened with externally bonded FRP sheets have been studied. The primary parameters are different stregthed FRP materials (CFRP、GFRP、CFRP/GFRP) and different initial stress levels(zero applied load,50%ultimate load and25%ultimate load unloaded from50%ultimate load). The experimental results show that behavior of FRP and beams depend on the carcking patterns. The rising ratio of ultimate bear capacity for these FRP sheets is FRP、 CFRP/GFRP、GFRP, respectively, and the dunctily of beams sterenghed with CFRP/GFRP is the best. The beams strengthed with FRP sheets have an excellent behavior in rack distribution.(2) Long-term test on10concrete columns were tested. The primary parameters are three different surface treatment of coat free, epoxy coated and CFRP sheet wrapped. The results showed that the creep coefficients in CFRP-confined concrete columns and in epoxy-coated concrete columns are almost same, but the creep coefficients values are about29.0%、26.9%higher to normal concrete columns.(3) Long-term test on12concrete beams were tested. The results showed that thelong-term deformation can desrease due to the effect of CFRP sheet. The higher unload values can decrease the long term deformation of beams. When beams are of the same ratio values of stress to strenght, the long-term deformation of beams with the14th day load time is higher than that of28th day load time. The long-term deformation of beams with100days creep time ia about60.0%～72.8%of that of650days creep time. The long-term deformation of beams strenghted with CFRP sheet are6%～16.5%of that normal conrete beams. (4) Fatigue tests of8strengthened beams which had/had not crept were completed. The behavior of crept beams with stregthed with FRP sheet after fatigue is better than that crept beams without stregthed with FRP sheet after fatigue. The beams strengthed with CFRP sheets have an excellent behavior in rack distribution. The ultimate capacity of beams with stregthed with FRP sheet is1.35times of that beams without stregthed with FRP sheet. It is shown that the reinforced concrete beams strengthened with carbon fiber sheets have better fatigue behavior.(5) The calculating formula for the flexural ultimate capacity, and searviceability of RC beams strengthened with externally bonded FRP sheets have been developed, which verifies that the computed values are precise.(6) The computed method of load capacity for beams strenghted CFRP/GFRP sheet were similar with that of beams strenghted CFRP sheet. And it is verified that the predicted results from the model presented are in good agreement with the test ones.(7) The computed method of long-term deformation for beams strenghted with CFRP sheet according to the effect modulas is develpoed. And it is verified that the predicted results from the model presented are in good agreement with the test ones.(8) The full analysis of fatigue is presented based on the residual strain、fatigue elastic and fatigue strength degradation, which verifies that the computed values are precise.(9) The numerical analysis based on the nonlinearly program is presented. And the program analysis of behavior of concrete structures strength by FRP are studied.