Seismic Evaluation of Steel Frames with Different Connection Conditions of X‐braces

Concentric steel X-braced frames are commonly used in steel structures to resist the lateral forces due to wind or earthquake loads. Common assumption for the brace connection is pinned, but in practice the connection of the braces could have partial rigidity, with regard to the details of the connection. In modeling of the X-braced frames, it is assumed that the diagonals at mid-span are crossing without interrupting each other; while, in practice one of the diagonals is discontinuous. On the other hand, the buckling load of the braces is affected by the effective length factor that is affected by the conditions of the end and mid connections [1, 2]. Therefore, changing the conditions of the brace connections affects the buckling load of the brace and consequently the behavior of the frame. In this paper, the behavior of two dimensional X-braced steel frames with different number of stories (3, 5 and 10) and bays (3 and 5) was investigated which were different in connection conditions of braces. The end and midconnections of the braces were modeled in either pinned or rigid extreme states with proportional effective length factors.