Einfluss der Oberfläche und Festigkeit auf das Spannungsrisskorrosionsverhalten von Spannstählen

The role of surface condition and strength in stress corrosion cracking of prestressing steel

Numerous bridges in Germany are currently classified as “in need of reservation”. In these structures, not only reinforcing steel but also prestressing steel is used as reinforcement. The latter is particularly susceptible to stress corrosion cracking, a brittle material failure triggered by the ingress of hydrogen. To investigate the influencing factors, constant load tests (CLTs) were carried out on three different prestressing steel grades and examined using state of the art methods. The test program was divided into component testing, testing on prestressing steels as received, and material testing, testing on machined and polished test specimens made from prestressing steels. This procedure was used to identify the influence of the surface against stress corrosion cracking. Furthermore, it was found that higher strengths resulted in a decrease in service life. Treatment of the surface by polishing had a positive effect on the service life of the test, particularly in the case of low strength classes. By reducing the load by 10 %, a median increase in duration of 126 % was achieved at the same strength class. In notch stress analyses using finite element modeling on digital twins of prestressing steel, the influence of the surface condition was highlighted. Hydrogen analyses conducted following the constant load test showed an increase in diffusible hydrogen content with rising material strength in both component and material testing.