Fatigue Behaviors Of Reinforced Concrete Beams Strengthened With Carbon Fiber Sheets After Creep

Carbon Fiber Reinforced Plastics,having the merits of high strength,light weight, corrosion resistance and fatigue resistance, superadded handy constructing and decline of price ,are wildly used in the field of structure reinforcing. At the present time, the studies about the structure strengthened with CFRP sheet mostly focus on the aspects of static characteristics of bending resistance and shearing resistance etc. while studies about fatigue performance are in a starting phase and those of fatigue performance after creep are even blank. Aiming at these actualities, this paper studies mainly following several aspects:(1) Having made contrastive fatigue tests of strengthened beams which had crept, those had not and girders which had crept but hadn't been strengthened. Tests showed that the developing speed of concrete strain of strengthened beams which had crept in the front 200,000 times was slower than that of strengthened beams which had not crept, while the developing speed of the strain of steel bars was in direct contradiction; in the process of fatigue tests, concrete's and steel bars'strains fluctuated; for the ultimate strains of concrete and that of steel bars after fatigue tests which happened in the static destroy period, the strengthened beams which had crept were less than that of strengthened beams which had no crept, while for CFRP sheet's strain in static destroy, the former was largely greater than the later; after fatigue tests the limit deformation ability of strengthened beams which had crept was not as good as the no-crept; the strengthened beams which had crept had no better deformation abilities than the strengthened beams which had not crept, but their static bearing capacity was 1.4 times than that of the strengthened beams which had not crept. In the process of fatigue tests, cracks mainly developed in the front 200,000 times.(2)Having studied on the developing rules of materials'residual strains of strengthened beams which had crept and that of strengthened beams which had not crept in the process of fatigue tests. The analysis of test data showed: the development of concrete residual strain was basically in accord with concrete fatigue distortion three phases rules; the development of steel bars'residual strain was basically in accord with ratchet effect of ductile materials and threshold effect theory; carbon fiber sheet's residual strain developed as a result of the development...