Comparison of the Seismic Performance of Braced Steel Frames with Suspended Zipper Element and CBF with the possibility of Rocking Motion

Zipper bracing system is one of these types of braces. The zipper bracing members transfer the unbalanced tensile forces created in a floor to its upper floor, and this process continues until there is an increase in lateral load and causes the braces of the higher floors to buckle. In this article, the dynamic behavior of the braced structure with zipper under the influence of earthquake records with rocking component and without rocking movement has been studied. SAP2000 software was used for modeling. Seven accelerometer pairs have been utilized for nonlinear dynamic analysis. The studied frames are 6-, 9- and 12- floors with a floor height of 3 meters. In all the studied models, the joint in the bracing part has been damaged. In this part, most of the damages have been at the level of continuous usability, and in the 9- and 12-story structures, the damage is a little wider and at the level of life safety performance. In the structures where rocking movement has been applied in the foundation part, it has caused the movement and shearing of the foundation of the structure to be reduced by 20 to 35 percent because it absorbs some of the earthquake force. Examining the results related to the displacement of the roof of the structure, it has been observed that the displacement of the roof in the structure with CBF bracing was about 10 to 25% less than the structure with zipper bracing.