f.a Hejazi - Department of Civil and Enviromental Engineering, Amirkabir University of Technology, Tehran, Iran
M. - Department of Civil and Enviromental Engineering, Amirkabir University of Technology, Tehran, Iran

Experience in recent earthquakes such as Loma Prieta and Northridge shows that the existing seismic design codes are relatively reliable in avoiding life-threatening damage. But the economic losses of these earthquakes lead to use of higher performance levels with lower losses. This new requirement for better performance has led to the development of the performance-based seismic design methodology. Performance-based optimum design of reinforced concrete buildings is a relatively new field of research. The performance criteria which are imposed as constraints, affect the initial construction cost that has to be minimized. Based on this approach, perhaps the first effort to combine the contemporary concept of performance-based design with structural optimization came from Ganzerli. They proposed an optimization methodology for seismic design, considering the performance-based constraints. Lagaros proposed an automated procedure for minimizing the eccentricity between the mass center and the rigidity center in RC structures. Furthermore the optimal decision model of the target value of performance-based structural system reliability of RC frames is established according to the cost-effectiveness criterion. This paper presents an effective computer-based pushover analysis technique for the performance-based design of concrete frames to predict post-elastic seismic demands under equivalent static earthquake loading. Using an energy approach, the performance-based optimization of concrete moment resisting frames is evaluated for the so-called operational, immediate occupancy, life safety and collapse prevention performance levels. Three objective criteria are identified for the performance-based seismic design, which include the least structural weight, uniform ductility demands and also uniform earthquake energy for all the stories. The results obtained for a five-story concrete moment frame and compared with the dynamic behavior of these buildings. Considering the results, it can be concluded that the optimized frame under weight-energy function have the best behavior in comparison with the other frames under earthquake loadings.

Optimization, Performance-based design, Uniform energy, Concrete moment frames