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• 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. [ABSTRACT FROM AUTHOR]

Abstract Prestressed concrete girders and piles with steel strands are used in construction of bridges in North America, due to their economy of design, fabrication, and installation. However, they are often exposed to harsh environments, which results in rapid degradation. Therefore, carbon fiber reinforced polymer (CFRP) tendons have successfully been introduced as prestressing reinforcement for pile applications. This paper presents a study on the physical characterization, microstructural analysis, and durability performance of unstressed and stressed carbon-fiber composite cables (CFCCs) for prestressing applications. This is achieved through testing 120 CFCC specimens, subjected to stress levels of about 40% and 65% of their guaranteed strength, and 51 specimens without sustained load under tension. Moreover, prediction models were introduced to assess the long-term performance and retentions of CFCC strands. The models included Arrhenius model, Fick's law, Fib Bulletin (40) model, and a developed approach that incorporates the effects of temperature, design life, and relative humidity of exposure into the environmental reduction factor. Based on the predication model, the tensile strength retention (C E) for CFCC strands, is predicted to retain over 0.95 and 0.84 of ultimate tensile strength for a relative humidity (RH) < 90% and a moisture saturated environment (RH = 100%), respectively, after 100 years of service life with elevated temperature and sustained load. Highlights • Carbon fiber Composite Strands. • Sustained Load. • Durability of Carbon Fiber. • Long-Term performance of CFRP. [ABSTRACT FROM AUTHOR]