Topology optimization of multiple-rocking concentrically braced frames subjected to earthquakes.

This paper presents a topology optimization approach for the seismic design of multiple-rocking self-centering concentrically braced frames (SC-CBFs). SC-CBFs have been recently developed as damage-free seismic lateral load-resisting systems. In these systems, rocking sections are potentially designed in several locations over the height due to several modes. The design of multiple-rocking SC-CBFs is a demanding task due to their highly non-linear behavior. The vertical irregularity, caused by the non-continuous stiffness over the height of these systems, makes the prediction of their behavior a challenging task, especially when subjected to dynamic ground accelerations. In this paper, an efficient and general design approach for these systems is developed utilizing gradient-based topology optimization. An optimization problem is formulated such that the construction cost of the SC-CBF is minimized while simultaneously considering the topology of the frame, cables, energy dissipation (ED) material, and the location of the rocking sections. The performance of the building is limited to acceptable limits by formulating the constraints of the optimization problem based on the results obtained from non-linear time history analysis (NLTHA). An efficient numerical integration scheme based on the mixed lagrangian formalism (MLF) was adopted to conduct the NLTHA. The proposed method was used for the design of 5- and 10-story buildings. The results show that efficient designs could be achieved with a reasonable number of iterations using a personal computer. This makes the proposed approach desirable for the design of multiple-rocking SC-CBFs by researchers and engineers. [ABSTRACT FROM AUTHOR]