Mechanical Properties of Reinforcing Steel in R/C: Uncertainty Analysis and Proposal of a New Material Factor

Although the statistical parameters of basic reliability variables such as concrete and reinforcing steel should be determined and its uncertainty sources should be quantified for the reliability analysis, the related studies were carried out about 30-40 years ago. In spite of the upgradation of criteria of reinforced concrete practice and steel production techniques from the past till the present in the world, the material (partial) factor for reinforcing steel is still the same (1.15). To the best knowledge of the author, there is no published work in the literature on this specific work. The main aim of this study is examining the variations in the mechanical properties of reinforcing steel bars, to carry out an uncertainty analysis with the quantification of these variations and proposing a new material factor for reinforcing steel bars based on the uncertainty analysis. In addition to this, considering the mean values and variations of the yield strength, ultimate strength and elongation, and their conformity with the relevant standards, the quality of reinforcing steel bars is investigated from a statistical point of view. The test results consisting 79133 S420a reinforcing steel bar specimens sizing from 8 to 32 mm are evaluated. At the end of this study, it is observed that variations in the mechanical properties are high and the quality of these bars has increased compared to the previous years. In addition, a new material factor (gamma(S) = 1.05) for reinforcing steel bars is proposed.