Abstract A scheme of optimal retrofit under the alternate loading condition of a plane linear-elastic frame is presented. Retrofit is used for an overload or a more restricted drift. Optimization is then used for minimum change of objective function subjected to the behavioral and side constraints of retaining the member sizes of the given design, as far as possible. The latter constraints are met by performing analysis for sensitivity to change of member sizes under overload conditions. The method is illustrated with examples and an overall flow diagram of the operation involved is also presented.