Evaluation of the Effect of Connection Stiffness on the Failure Probability of Zipper Bracing Frames under the Near- and Far-Fault Earthquakes, Performance Levels Approach

Vertical elements between the beams can be used to control the failure on the chevron braces due to the post-buckling behavior. Zipper bracing is a new bracing system which expected to recover chevron bracing defects. By applying the vertical element to the chevron bracing and converting it to a zipper frame, it improves frame resistance, ductility and energy absorption. In this thesis, the seismic behavior of zipper brace frames is investigated for different percentages of beam-to-column connection stiffness under near- and far-field earthquakes. For this purpose, two types of pre-designed 4 and 8 story steel frame with 0, 25,75 and 100 stiffness percentages are analyzed using IDA method in OpenSEES. Finally, the fragility curves are compared at 4 performance levels. According to the results obtained from IDA analysis and the fragility curves, the effect of different stiffness percentages under near-fault earthquakes is more noticeable than far-fault earthquakes, which decreases the percentage of structural collapse by articulation the retention and articulation of joints. This probability also depends on the height of the frame. On the other hand, it can be obtained that the rigidity of the connections does not significantly changes the structural capacity and performance levels.