RELIABILITY-BASED OPTIMAL-DESIGN OF REINFORCED-CONCRETE FRAMES

Reliability based optimal design (RBOD) of structures aims at minimiza tion of structural cost constrained by a specified allowable failure p robability. A methodology has been developed for RBOD of reinforced co ncrete frames which considers the failure of structure, both at the co mponent and system level simultaneously, under two different live load and wind load combinations. System failure probability is evaluated b ased on the generated stochastically dominant failure modes which cons ist of collapse mechanism failure modes and rotational failure modes ( arising due to critical sections reaching their permissible inelastic rotation capacities). Optimal values of the moment capacities of criti cal sections are obtained based on the minimization of the total struc tural cost of the frame using the cost functions for member sections a s a function of their moment capacities, which are derived by optimizi ng the member sections. It is observed that designs obtained using RBO D procedure give cost reduction for the chosen target reliability leve l, equal to that inherent reliability in the designs obtained as per t he present Indian standard specifications.