Safety of reinforced concrete members designed following ACI 318 building code

The safety level of reinforced concrete members designed following the 1995 edition of ACl 318 building code using both Chapter 9 and Appendix C load combinations and strength reduction factors is investigated. Safety is evaluated in term of the reliability index, since load and resistance are random variables. The strength limit states considered in the study include flexure, shear, and combined axial compression plus flexure. The effect of low and:high reinforcement ratios for beams in flexure is taken into account. Beams with minimum stirrups and with normal shear reinforcement are also considered. For the case of columns subjected to axial load plus flexure, both compression and tension failures are included. The load variables considered in the limit states are dead load, live load, and wind effect. The reliability of typical members is determined for a range of live-to-dead load ratios and for two extreme ratios of wind-to-dead load. The results of the study indicate that designs based on Appendix C can result in more uniform safety than current designs based on Chapter 9. Further, structural safety of designs based on Appendix C matches, and often slightly exceeds, the safety of designs based on Chapter 9. (C) 1997 Elsevier Science Ltd.