Towards a unified low-cycle fatigue model of steel rebars: A meta-analysis

Low-cycle fatigue (LCF) of longitudinal steel rebars is a critical failure mode of reinforced concrete components subjected to severe seismic loading. While extensive experimental studies have been conducted to understand the LCF behaviours of rebars with and without corrosion, still lacking is a unified fatigue life model that is applicable to rebars in their whole service life from an intact state to a highly corroded one. To fill this gap, the paper presents a four-stage meta-analysis of experimental data gleaned from six laboratories over the world in nine open publications, including those of the authors. An innovative feature of the proposed meta-analysis is the separation and quantification of labs effects that would otherwise prevent the other primary factors from being identified. The regression analysis considered a number of potential predicting factors including the cyclic strain, mass loss percentage, rebar diameter, span length ratio, and yielding strength. Stepwise linear regression technique is employed to select the most effective and parsimonious model. The analysis recommended a unified LCF model for both corroded and uncorroded rebars for a wide range of cases that apply to real-life designs. The results suggested that the abovementioned factors played a statistically significant role in the prediction of LCF life of corroded and uncorroded rebars. Future study should focus on the unexplained lab effects. It is recommended to develop an international standard or guideline for LCF testing in order to reduce the lab effects. The proposed four-stage method was proven to be a useful and effective technique for knowledge discovery from disparate data sources. (C) 2019 Elsevier Ltd. All rights reserved.