Cost optimal design of R/C buildings

A systematic approach is proposed for evaluating the cost-effectiveness of existing or proposed design criteria from the standpoint of life-cycle cost consideration. A series of alternative designs of a model structure representing a class of R/C buildings would be developed following an existing code procedure, except that the code requirements or parameters will be varied for the alternative designs so that a suite of different structures will be obtained each with a different level of safety or reliability. For each of the designed structures, the probability of exceeding the various damage levels under a given earthquake intensity may be calculated. Aggregating and integrating all the cost components with the damage probability density functions for each of the designed structures, as well as with the probabilities of all possible earthquake intensities over a given life will yield the expected life-cycle costs for the respective structures as a function of structural reliability. From these results, the design with the minimum expected life-cycle cost may then be identified; its underlying safety or reliability can also be determined. The approach is illustrated for a class of reinforced concrete buildings under earthquake loading.