Three-level performance-based optimization method of steel frames

Abstract This paper describes a three-level performance-based optimization model and an estimate method of residual top displacement for steel frames at three earthquake levels. The steel frames are supposed to be elastic at frequent earthquake, inelastic and hardening at occasional and rare earthquakes, respectively. The estimate formula is derived and estimate procedure is given in detail. The estimate method only needs to use (only) one pushover analysis until steel frames yield. The yield point is obtained automatically in the proposed method. The estimate method is able to make optimization process uninterrupted. Optimal design of a 3-story 2-bay steel frame is demonstrated to validate the proposed method.