Abstract:
This paper presents the results of studies which were conducted to investigate the effects of outrigger brace system on the potential of progressive collapse of tall steel buildings. Structures designed in regions with different seismic risk levels were also compared. Four twenty-storey structures with outrigger brace and tubular systems and different seismic risk levels have been designed in accordance with available standards. Progressive collapse of these structures was evaluated under vertical loading using both the nonlinear dynamic and static analyses. The results showed that the structures designed with more outriggers in higher seismic zones are more resistant to progressive collapse. The potential for progressive collapse in tall steel buildings with an outrigger brace system in low seismic zones was also less compared to the similar buildings designed with a tubular system in a high seismic zone.