دانلود Friction damper dynamic performance in seismically excited knee braced steel frames

Abstract

High  performance  and  reliability  of  refurbish  able  knee  braced  steel  frames  has  been  confirmed  in  previous  researches  trying  to  get  an  optimal  design  for  its  configuration.  Buckling  of  diagonal  member  which  affects  the  hysteretic  behavior  of  KBF under cyclic loadings has not been foreseen in previous evaluations of this system. This deficiency can be improved by utilization  of  adjustable  rotary  friction  damper  device  (FDD)  as  knee  element.  Diagonal  element  buckling  can  be  prevented  considering a suitable value for FDD sliding threshold moment Mf. Lower values of Mf Lower energy dissipation rate in FDD and this  leads  to  an  optimization problem. Nonlinear  time  history  analyses  have  been performed in addition  to  lateral  cyclic loading analyses to  evaluate the  response of single  story KBF  subjected to  seismic excitation. Optimal Mf in FDD has  been chosen according to these analyses results. Roof displacement and acceleration, base shear and diagonal element’s buckling status have been compared in optimally designed KBF and FDD utilized KBF (FKBF) with different configurations. Nonlinear dynamic  analyses  have  been  performed  for  one,  four,  eight  and  twelve  story  frames  under  different  seismic  records  with several PGAs. More than 60% displacement response reduction has been earned for the FKBF without considerable increase in base shear.