Residual load-bearing capacity of corroded reinforcing steel bars subjected to dynamic loads

• Applicant: Professor Dr.-Ing. Michael Raupach
• Subject Area: Construction Material Sciences, Chemistry, Building Physics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 502259457

Reinforced concrete structures subjected to fatigue loads, such as bridges, are often exposed to environmental conditions that promote corrosion. Probably the most common type is chloride exposure (de-icing salt on bridge structures, tidal areas in offshore constructions). Since reinforced concrete structures in State II contain cracks, there is a possibility that, especially in combination with dynamic loading and the resulting movement of the cracks, corrosion-promoting substances, e.g. chlorides, can be transported through the crack to the reinforcement and damage it on a local level. The preliminary work as well as the current literature has shown that the fatigue strength of concrete steels is reduced by the simultaneous effect of fatigue and corrosion. However, there is still a lack of fundamental knowledge on the influences of different diameters and exposures on the fatigue resistance. Closely related to this is the influence of the corrosion pit geometry. The aim of the project is therefore to quantify the influence of the corrosion of the reinforcing steel on its fatigue resistance for the exposure classes XC and XD/XS.For this purpose, corrosion pits are generated on different steel diameters in cracked reinforced concrete specimens using different exposure solutions in order to investigate the correlation between the amount of charge flowed and corrosive deterioration in different exposures. In fatigue tests, the correlation between the existing residual cross-section in combination with the morphology of the corrosion pit and the fatigue behavior of bare steel as well as composite specimens is determined. For a closer look at the critical geometric characteristics that reduce fatigue strength, morphologically precisely defined deteriorations are also applied to reinforcing steel bars. By means of the experimental program, mitigation factors for S-N-curves of different diameters and exposures are to be derived.

• DFG Programme: Research Grants