Seismic Performance-Based Layout Optimization of Outrigger System using Modified Dolphin Echolocation algorithm for Steel Tall Buildings

Towers and tall buildings have been considered since the beginning of human civilization and providing the suitable stiffness and especially the lateral stiffness is one of the basic factors in the design of these structures. In this matter outrigger systems are very effective in reducing the response of the structure to lateral loads. Also, the occurrence of earthquakes and its destructive effects in recent years has increased the importance of applying the behavior and performance criteria to control the distribution of resistance and deformation in structural components. Therefore, it is necessary to provide an optimal design with economic justification capability, the main purpose of which is to achieve a reliable level of safety and performance against natural hazards. In this research, in two structures with 24 and 36 floors, using modified dolphin echolocation metaheuristic algorithm (MDE), the performance based design of steel structures equipped with outrigger system while layout optimization of the brace has been done. All performance design constraints are considered in accordance with FEMA regulations. The results indicate the appropriate behavior of structures with outrigger, the effect of outrigger position on its performance and the process of achieving optimal structure. as the 36-story structure in the optimal position of the outrigger installation, the weight of the structure has decreased by about 3.9% compared to the installation position at equal height distances. In both structures, the criterion of story drift and axial length change of bracing members prevails and the necessity to consider the effects of higher modes in studying the behavior of the structure is emphasized so that by increasing the number of floors and higher modes influence, the optimal position of outrigger is shifted to the upper floors.