Carbon Fiber Sheet Reinforcement Damage The Concrete Frame Of The Test

Structural security and viability were depressed by engineering snag engendered by vice or error at aspect of reconnoiter,design,construction and use ,as well as structure aging caused by climate acting and chemical etching.In order to ascertain a structural security and viability whether to meet the challenge, the structural reliability need to be estimated by means of inspection and appraisal. Then its reliability and service life can be improved by repairing and strengthening. From 1990s, the reinforced concrete structures strengthened with CFRP (Carbon Fiber Reinforced Polymer) have been studied in China, and many achievements and abundant datas have been accumulated through experiments. But the aim of above researches is the behavior of individual component such as simply supported beams, overhanging beams and columns by CFRP, and there were little researches on the RC framework as a whole. Therefore, the experiments of damaged RC frame structures strengthened with CFRP would be studied.The experimental studys of three damaged RC framework components are made in this paper. First of all, security appraisal and reliability appraisal of the damaged frames are carried on by measuring section dimensions and crack widths, assessing the intensity of concrete and steel bar, and analyzing its theoretical bearing capacity. As a result, all the three components need to be strengthened. According to "Technical specification for strengthening concrete structures with carbon fiber reinforced polymer laminate", the reinforcing schemes are designed and the members were strengthened. Finally, the experiments on two reinforced members under vertical loads and a reinforced member under low-cycle repeated loads are made.The test results under vertical loads indicate that the cracks around the primary fracture appeared easily and developed slowly when the damaged cracks were filled into the structural adhesion and the member was strengthened for bending and shearing resistance together. Then the filled cracks re-fracture with loading. Finally the fail mode of the test-structures is characterized by beam hinge institution, while the steel bar strain and CFRP strain on the column is smaller. The ultimate anti-bending bearing capacity of the member strengthened only for bending sections would be increased drastically, and the tension is taken on mainly by CFRP after the steel bar yields, but the shear failure of beam support section is occurred easily. Whereas the member is strengthened for bending and shearing together, the shear bearing capacity of the member is increased and the flexural failure of beam commonly is occurred.Based on the test under low-cycle repeated loads, the curves such as load-displacement hysteresis curve, load-skeleton curve, the steel bar and CFRP hysteresis curve of beam and column are drawn out. The results indicate that the displacement hysteresis curve of the damaged frame structure submits linear type, the residual deformation is small before the steel bar yields. Then the hysteresis circle area becomes obviously aggrandized, the better ability of energy dissipation is shown. The ductility factor reaches 4.5, which shows that the structure possess favorable anti-seismic behavior. The rigidity degenerated law of the frame structure is that the rigidity of the structure degrades very fast from adding loads to cracking of the member, thereafter slows down. After the steel bar yield, the rate of rigidity degradation get wane because of the CFRP restraint action. From the degenerated curve of bearing capacity, bearing capacity fall less in company with displacement aggrandizement after bearing capacity of the member achieve maximization, thus it is show that the frame construction strengthened with CFRP posses relative strong ability to resist repeated loading. The steel bar hysteresis circles on the beam and column sections indicate that the hysteresis circles aggrandize obviously after yielding load, that is, the steel bars poss better energy dissipation ability. The CFRP hysteresis curve is the same as that of the steel bar on the beam section, but the CFRP hysteresis circle area is smaller in comparison with the steel bar's on column section, the residual deformation is small. Meanwhile, the strain of CFRP is farther less than its ultimate stretching strain until the frame structure is damaged. So the structure strengthened at CFRP meets the seismic need of Strong-column with weak-beam.