Case Studies: Structural, Fractographic and Mechanical Aspects of the Steels Degradation of the Hyperboloid Gridshell Towers

Abstract

The typical corrosion damages of structural elements of water tower design engineer V. Shukhov in Mykolayiv (Ukraine) were analyzed. The technical state of the old and repair (used for tower renovation) steels after operation during ~110 and 70 years respectively were evaluated. For their validation the metallographic and fractographic investigations and estimation of the mechanical properties such as hardness, strength, plasticity, impact toughness and stress corrosion cracking (SCC) at slow strain rate test (SSRT) were used. Low values of hardness and brittle fracture resistance were typical for both exploited steels. The mechanical characteristics of the old steel obtained in air were worsened compared with the repair one. Moreover, the plasticity characteristics of both steels, determined at SCC tests in synthetic acid rain environment, are lower than in the air. It was suggested that fractography elements had appeared due to hydrogenation effect of steels at the influence of the corrosion environment (the really acid rain) during their long-term operation in the structural elements of the water tower. The whole complex of studies had confirmed a degradation of steels’ characteristics caused by the development of scattering damages during their operation.