Variability of mechanical properties of steel rebars in North America and its effects on the seismic fragility of reinforced concrete columns

•Mill source has a significant contribution to the variability of mechanical properties of steel rebars.•The effect of bar size and weight per meter has an insignificant contribution to rebar mechanical property variation.•A total of 0.12% of the tensile test data fall below the minimum ASTM standard requirements.•Beta distribution better represents the distributions of yield strength and ultimate tensile strength.•The effect of variation in mechanical properties of rebars on the seismic fragility of reinforced concrete columns is presented. This study examines the variation in mechanical properties of reinforcing steel bars and its impact on the seismic design of reinforced concrete (RC) bridge columns. The variation of mechanical properties of rebar as per American Society for Testing and Materials (ASTM) A615 and ASTM A706 is studied using 685,351 and 950,000 tensile testing results obtained between the years of 2009 and 2019 from various mills across North America. An analysis is performed using classification and regression trees (CART) to identify parameters with the highest relative influence considering source mill, bar size, and weight per meter. Probability distribution functions are developed for yield and ultimate tensile strength data. The beta distribution shows better agreement with the distributions of yield strength and ultimate tensile strength. Results show that 0.12% of the tensile test data fall below the minimum ASTM standard requirements. In addition, the study also examines the effect of the variability of yield strength of longitudinal rebars on the seismic response of circular bridge columns using fragility analysis.