Behavior of Slipped Bolted Steel Frames Consisting of Cold-Formed Steel Sections under Cyclic Loading

After passing through the allowable stresses stage Cold Formed Steel Frames fail under instability secure, these frames are designed to resist loads in the elastic stage [7]. Many efforts are being made to increase their performance by using special bolted or welded connections [13], such as rigid connections or plastic connections, stiffened and built-up sections [1] could be used to increase the sections resistance. In rigid connections [11], stiffeners are added to insure the flexural behavior of these connections [10] while the plastic deformation occurs at the Horizontal Boundary Element (beam) and far from the face of the column, such as stiffened bolted Apex connection. In plastic connections, the cold formed steel frame will produce high ductility performance through the nonlinear behavior by reaching the maximum bearing capacity of the bolts. Depending on this principle we should insure the elastic behavior of the boundary elements, and avoid local buckling by using high strength cold formed profiles and slipping bolted connections, the rotation of this slotted connection in certain angle after reaching the bearing capacity, will act as a plastic hinge that absorbs the extra stresses which will affect the steel frame due to the lateral loads such as Cyclic forces