Optimal shapes are found for a reduced beam section of a cantilever H-beam subjected to forced cyclic displacement at the free end. The beam is discretized to finite elements, and a commercial software package called ABAQUS is used for elastoplastic analysis. The numerical results are first compared with experimental results to verify the accuracy. The objective function to be maximized is the dissipated energy throughout the loading history. The constraint is given for the maximum equivalent plastic strain at the welded section. Global optimal solutions are searched for by a heuristic approach called simulated annealing, which is successfully combined with ABAQUS. It is shown that the energy dissipation capacity is significantly improved by optimizing the flange shape. (c) 2009 Elsevier Ltd. All rights reserved.