seismic evaluation of composite steel moment frames with brace members and rotational friction dampers under near-fault earthquakes

Dampers are employed to improve the cyclic behavior of structures against wind- and earthquake-induced loads. rotational friction dampers (rfds) dissipate energy through reciprocal rotation. the present research investigates the behavior of steel frames with concretefilled columns under three different frames of identical configurations for beams and columns but different positions for the bracing and rfd systems to see the effect of eliminating a part of the bracing member. two loading schemes were considered to study the behavior of the introduced frames. in the first stage, the frames were subjected to vertical loading coupled with a cyclic load at the beam level. in the second stage, however, the cyclic load at beam level was replaced with earthquake acceleration at the structure base. all sample frames were thenmodeled and analyzed in finite-element software. applying the bracing system coupled with the rfd reduced the base shear compared to the structure without the bracing and rfd systems, although the reduction was not the same for all frames with different bracing schemes. moreover, compared to the frame without the rfd, the damper could limit the structural drift in 6 models, though it boosted the drift in 1 model. results showed that rfds can dissipate seismic energy through rotational friction slippage. the dampers could dissipate up to 90% of the energy induced by lateral loads to the structure. also, removing a portion of the bracing member was found to be useful for architectural purposes.