Fatigue Test Of Reinforced Concrete Beams With Corrosion Main Reinforcement

Many reinforced concrete (RC) structures, such as railroad bridges, highway bridges, viaducts and production platforms, are subjected to not only static loads but also repeated fatigue loads from vehicles, waves and so on. Corrosion of reinforcing steel bars embedded in concrete causes the deterioration in fatigue of RC bridges, and leads to the reduction in useful service-life of RC bridges. This paper presents fatigue test results of8natural corrosion reinforcing steel bars and5corroded RC beams supported by the Shandong Province Young and Middle-Aged Scientists Research Awards Fund (NO.BS2011SF013) and the Natural Science Foundation of China (NO.51008182). The paper mainly includes four parts.Firstly, comparative analysis is conducted on the corrosion morphology and fatigue performance of natural corrosion steel bars and accelerated corrosion steel bars. It is found that there are many corrosion pits on the surface of natural corrosion steel bars, and the outside near concrete cover corrodes more seriously. However, uniform corrosion occurs for accelerated corrosion steel bars. The degeneration in fatigue life of natural corrosion steel bars is greater than that of accelerated corrosion steel bars under the similar stress range and level of corrosion.Secondly, axial tensile fatigue tests are conducted on8naturally corroded reinforcing steel bars. The fatigue life of corroded reinforcing steel bars is studied. The fracture mechanism in fatigue is explored by using the electron scan microscope. It is showed by the results of tensile fatigue tests, that fatigue life of naturally corroded reinforcing steel bars is very discrete. Stress amplitude and corrosion level have great effects on the fatigue performance of corroded reinforcing steel bars. Stress concentration at corrosion pits make the fatigue life of reinforcing steel bars reduce greatly.Thirdly, constant amplitude fatigue tests are conducted on5corroded reinforced concrete beams. On the basis of the test results, their failure forms, crack distributions, fatigue life, deflection, reinforcement strain and concrete strain are studied. The results indicate that corroded reinforced concrete beams have obvious shear cracks under fatigue loading; shear fatigue failure occurs for most of the corroded RC beams; the fatigue life of corroded RC beams reduces greatly; changes of deflection can be divided into three stages, up-stability-up; with the increase on cyclical numbers, maximum strain and minimum strain of corroded reinforcing steel bars increase slightly, but the strain amplitude does not change; the maximum strain and minimum strain of concrete increase obviously.Finally, the fatigue life of corroded RC beams and corroded reinforcing steel bars subjected to tensile fatigue loads are comparatively analyzed. Results indicated that the fatigue life of corroded RC beams is much longer than that of corroded reinforcing steel bars.