Weibull modeling of the fatigue life for steel rebar considering corrosion effects

Abstract

Corrosion of steel rebar is one of the most severe causes in the deterioration of RC (reinforced concrete) structures. This paper studies the influences of corrosion on fatigue life of steel reinforcement in RC structures. First, a Weibull model of the C-S-N (Corrosion S-N) relationship for steel rebar is proposed in this research. The corrosion degree and stress range are regarded as the input variables for the proposed Weibull model. The expectation–maximization (EM) algorithm is used to deal with parameter estimation considering the censored data. Fatigue data are collected from experiments reported in the literature for three types of corroded steel rebar, considering different corrosion processes. These data are then used to establish and validate the proposed model, and the influence of corrosion on fatigue life is illustrated and discussed in detail. The proposed multi-parameter phenomenological Weibull model can be used to evaluate the fatigue life of steel rebar for both natural corrosion and artificially accelerated corrosion, which establishes quantitative influences of corrosion degree on fatigue life for steel rebar. In particular, the results indicate that the influence of corrosion on fatigue life is not the same for different kinds of steel rebar. For example, the model shows that the fatigue life of Grade 500 MPa steel rebar, which is used widely in modern structures, is shown to be sensitive to corrosion; fatigue life decreases sharply once corrosion initiates. Moreover, the effect is more pronounced at lower stress ranges. Therefore, to prevent premature fatigue induced failures, avoiding corrosion in Grade 500 MPa steel rebar during the structural service period is crucial.