Experimental and numerical investigation of rotational friction dampers with multi units in steel frames subjected to lateral excitation

Performance of rotational friction dampers with two and three units was evaluated experimentally because of a lack of research data on performance of these dampers with multi units. Results of multi-unit dampers were compared with the results of one-unit damper. Increasing trend in dissipating energy was observed. Then, the behavior of these dampers in frames of 3, 7 and 12 stories was studied by modeling the damper directly. Nonlinear time history dynamic analysis was used. It was observed that by increasing the number of stories in the buildings, dampers with multi units should be used to perform properly against earthquake. The equivalent damping method was also investigated to consider the effects of this damper without direct modeling of the damper. Effective damping of the frames equipped with this type of damper was estimated and used in nonlinear time history dynamic analysis and it was observed that the responses of these structures with dampers can be approximated by the responses of moment resisting frames without damper but with damping equal to the effective damping due to rotational friction damper.