
The reliability of structure is its ability to achieve its design purpose during a specified time. The reliability index is equivalent to the probability of safety. In this study, the reliability index for the RC slender columns with rectangular cross section is studied. The variable parameters studied include the concrete compressive strength, the reinforcement yield strength, the loads, the reinforcement ratio, the dimensions of concrete cross-section, and the location of steel placement. Risk Analysis program called @Risk (Version 6.0) was used to perform the analytical study. This paper present the effect of the reinforcement ratio and the cross section dimensions on the reliability index of slender reinforced concrete columns. The results of this study indicate that the good quality control has significant effects on decreasing the coefficient of variation for the concrete compressive strength, yield steel strength and the dimension of reinforced concrete sections which in turn improve the performance of slender reinforced columns through increasing the reliability index β.