Study of Structural Safety of Reinforced Concrete Flexural and Compression Members

This paper summarizes the assumptions and analyses used for developing the reliability-based design of reinforced concrete flexural and compression members. Based on data on the variability of concrete and reinforcing steel physical and dimensional properties, estimates were made of the variability of strength of reinforced concrete beams and columns. These data, plus statistical descriptions of loadings, were used in a first-order, second-moment probabilistic analysis to compute resistance factors. Two sets of resistance factors for reinforced concrete members subjected to flexural or combined axial load and flexure are discussed: (a) resistance factors compatible with the current American Concrete Institute (ACI) load factors specified in ACI 318-95 Section 9.2; and (b) resistance factors compatible with the American Society of Civil Engineers (ASCE) Standard 7-95 (ANSI A58-1) load factors included in ACI 318-95 Appendix C. This paper provides a direct comparison between the two sets of load and resistance factors that are now part of the ACI 318 safety criteria.