1 Rakenteiden Mekaniikka (Journal of Structural Mechanics) Vol. 48, No 1, 2015, pp. 1-17 www.rmseura.tkk.fi/rmlehti/ ©The Authors 2015. Open access under CC BY-SA 4.0 license Performance-based seismic optimization design Qimao Liu 1 and Juha Paavola Summary. Performance-based engineering is to design, evaluate and construct, as economically as possible, the engineering facilities that can meet the uncertain future demands of owner-users and natural hazards. The performance-based design is believed to be the promising method in earthquake engineering, wind engineering and fire engineering. The paper takes the performance-based seismic optimization design as an example to describe the philosophy of the performance-based design method. First, the basic concepts of performance- based seismic design are introduced. Second, how to quantify the uncertain future hazard levels, i.e., to obtain the future demand diagrams, is presented. Third, how to quantify the capability of the structures to resist the future hazard, i.e., to achieve the capability diagram, is in detail. Fourth, how to evaluate the performance of the structures at different future hazard levels, i.e., to catch the performance points, is described. Finally, the optimization modelling is proposed for the performance-based design. The performance-based design of steel frame is demonstrated. The limitations of the current performance-based seismic design method are also discussed. Key words: performance-based design, earthquake engineering, capability diagram, demand diagrams, performance points Received 23 March 2015. Accepted 17 May 2015. Published online 3 June 2015 Introduction Performance-based engineering is to design, evaluate and construct, as economically as possible, the engineering facilities that can meet the uncertain future demands of owner- users and different natural hazards. The performance-based design is broadly believed to be the promising and advanced design method in earthquake engineering, wind engineering and fire engineering. The philosophy of the performance-based design is that the design criteria are expressed using a set of achieving stated performance objectives when the structure is subjected to the different stated hazard levels. For 1 Corresponding author. qimao.liu@aalto.fi