Saeed Kia Darbandsari - Ph.D. Student, Department of Civil Engineering, South Tehran Branch, Islamic Azad University, Tehran ,Iran
Mahmood Hosseini - Associate Professor, Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran

Vertical growth of cities, has become a challenging issue in the building industry, due to the heavy urbanization and population growth. Bracing, is a highly efficient and economical method in order to achieve resistance against lateral loads in a tall building with steel structure. In order to improve the structural efficiency of tube-type skeletons in tall buildings, a new structural system, known as hexagrid, is investigated in this paper. In comparison with the diagrid system, the hexagrid, consists of multiple hexagonal grids on the periphery of the building. This investigation quantifies three seismic performance factors, including over-strength factor (Ω0), period-based ductility (μT) and response modification coefficient (R) for hexagrid, diagrid and tube systems. The present study involves the 30- and 50-story of peripheral hexagrid and diagrid bracing systems compared with the tubular system. The structures were evaluated using nonlinear static and dynamic analyses. According to the results, the hexagrid system has a better response modification coefficient (R). Nonlinear static and IDA analyses are conducted using Open Sees software. The structures’ behavior under 7pairs of ground motion records have been investigated by nonlinear time history analysis utilizing PERFORM-3D software. The maximum inter-story drift for the studied models was determined and compared with the life safety and collapse prevention performance limits, as recommended by FEMA P695.

Hexagrid systems, Diagrid Systems, High-rise buildings, nonlinear analysis, inter-story drift