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

Behavior of Steel Frame with Thin Steel Infill Plate or Steel Bracing Under Cyclic Loading-Comparative Study

Braced frames and steel plate shear walls (SPSWs) have both been shown to be useful in the seismic retrofit of buildings. While both these systems have merit, no guidance exists to determine which of the two approaches is preferable in terms of providing maximum displacement ductility and energy dissipation per cycle for a given strength. This paper describes and compares results from numerical evaluation using FEM, in which the nonlinearity of materials and the nonlinear effects of the large displacement was included for tow frames. The results of numerical study was identical to the experimental tests, then a barometric study was achieved by changing the thickness of infill plate then the area of the cross sections of braces, after that the width of the frame was modified. The result shown that using steel infill plate is preferable when the dimension of bay is three times the height, while using braces is more adequate for frames in which the dimension of bay is less than three times the height.