Challenges and opportunities in performance-based design of structures under earthquake loads

Performance-based design of structures differs from the conventional prescriptive approach mainly in two technical aspects. One is to relate the design to structural performance directly, and the other is to design a structure for multiple performance objectives. Due to load and strength uncertainties, however, it is impossible to design a structure for specific performance objectives with complete assurance. In this paper, a framework involving structural control and system identification emerging technology is proposed to reduce the load and strength uncertainties, and to introduce a new design concept for the optimized balance of the load and strength under multiple performance objectives. It involves four main components: new definition of design earthquakes to minimize the variability of ground motions, bounded control on the seismic responses of a structure for further reduction of the variation of seismic load, on-line system identification of hysteretic behavior for reduction of the strength uncertainty, and damping-enhanced strengthening methodology for the optimal performance of the structure. The needs and approaches to develop these concepts are discussed, and some of the preliminary results are presented towards their development with a simple structure.