Effects of FRP Repair on Static Strength
Figure 4 (a) and (b) show the normalized yield load vs. mass loss and normalized ultimate load vs. mass loss for the corroded-no load, corroded under load and CFRP repaired specimens. The normalized load is taken relative to the control specimen (at 0% mass loss). Corrosion of the steel reinforcement up to a 5.5% theoretical mass loss while the beam is unloaded resulted in a 10% and 9% reduction in the yield and the ultimate loads, respectively compared to those of the virgin uncorroded beam. The reduction in the yield and the ultimate capacity increased to 13% and 13.2%, respectively when the corrosion occurred under sustained load. A 12% theoretical mass loss of the steel reinforcement caused 16% and 11% reductions in the yield and the ultimate loads, respectively when corrosion occurred without load. Loading the beam with a 12% mass loss increased the reductions in yield and ultimate load to 22% and 17%, respectively compared to the virgin uncorroded specimen.
When CFRP external reinforcement was added there was an increase in the load carrying capacity. Compared with the uncorroded virgin beam, the uncorroded-strengthened beam exhibited a 30% and a 49% increase in the yield and the ultimate load, respectively. When a beam is corroded before the application of the CFRP laminates it doesn’t reach the same strength as a strengthened uncorroded beam. The yield and the ultimate loads of the corroded-repaired beam at a 5.5% theoretical mass loss were 85% and 97%, respectively of that of the uncorroded-strengthened beam but they were higher than those of the virgin control beam by 11% and 43%, respectively. Increasing the level of corrosion damage to a 12% theoretical mass loss before repair reduced the yield strength to 77% of that of the uncorroded-strengthened beam while the ultimate strength remained at 97% of that of the uncorroded – strengthened beam. The yield load of the beam repaired after corrosion to a 12% theoretical mass loss was almost the same as that of the virgin control beam while the ultimate strength was still higher than that of the virgin beam by 43%. It is interesting to note that the ultimate strengths of the cor – roded-repaired beams were very close to that of the uncorroded-strengthened beam. This means that while corrosion of the steel reinforcement reduces the ability of the CFRP repair to increase the yield load its effect on the ultimate strength gained by repairing the beam with CFRP laminate is minimal.
a) yield strength
b) ultimate strength