Experimental and Numerical Study of Pyramidal Steel Damper for Use in Frames with Diagonal Bracing

Convergent bracing system has long been considered by structural designers. However, the performance of this system during an earthquake has disadvantages such as high base shear and low energy absorption due to buckling of the braces. Thus, researchers have tried to improve the behavior of the structure by proposing the use of different dampers in the lateral bearing section. Meanwhile, yielding dampers as low-cost dampers with easy manufacturing technology compared to visco-elastic and non-buckling dampers have always attracted the attention of researchers. However, the proposed designs have generally a one-level behavior and the yielding members cause instability of the frame in the case of the failure. Accordingly, in this research, a new type of steel yielding damper with multi-level performance has been introduced, in which the flexural yield of the parallel trapezoidal plates has been used for the energy absorption process. Also, to ensure the stability of the braced frame in severe earthquakes, a simple support system has been included in its design. The damper has a pyramidal core that can be adjusted for stiffness and functional levels based on the seismic requirements of the frame. To perform this research, while performing finite element modeling, the relevant specimens were made and subjected to cyclic loading experimental tests. Also, a comparative nonlinear time history analyses on a seven story CBF frame has been done. The results indicated the appropriate and stable cyclic behavior of the two-level pyramidal damper, tolerance of cumulative displacements of about 2000 mm, absorption of a significant energy of 50 kJ and significant improvement in time history responses. Finally, multi-line behavior curve and a capacity chart of the damper is presented.