ABSTRACT
This work presents reliability analysis of optimally designed reinforced concrete frames in accordance with Eurocode 2 (2004). A computer program in MATLAB (2004) was developed to analyze the frames based on direct stiffness method. The mathematical models of the design optimization problem were formulated and computer programs developed to obtain economical cross sectional dimensions and the corresponding amount of reinforcing steel using optimization process. MATLAB optimization tool box, was employed to perform the optimization. Reliability analysis based on the First-Order Reliability Method of analysis as in FORM5 (Gollwitzer, et al., 1988) was employed to determine reliability levels of optimized frame elements. The results showed that optimum design resulted in cost savings of 5.1% in beams and 3.2% in columns. The reliability indices of the critical beam in flexural failure mode were3.96 and 3.43 for deterministic and optimum designs respectively. The results of column axial failure mode gave reliability indices of 5.83 and 5.04 for deterministic and optimum designs respectively. The results of system reliability analysis gave system reliability index value of 3.33 as against the minimum component reliability index of 3.43 for the critical member. The optimally designed reinforced concrete frames resulted in cost savings but the component and system reliability indices were both lower than the reliability indices of the deterministic design.