seismic behavior of rbs connections at near and far field earthquakes

moment-resisting frames have extensive usage in earthquake-prone areas and high ability in energy dissipation.after the earthquake in northridge 1994,kobe 1995 fixed connections of steel structures have shown poor performance and generally they were caught brittle fracture of beam flange weld to the column.in order to remedy to avoid similar situations in future earthquakes,researchers introduced connection with reduced beam section in name of rbs(reduced beam section),that stress concentration at the junction can be prevented by reducing the local section of beam in the vicinity column and location of plastic hinge transferred from connection to the distance from the column.  in this research, firstable the three special steel moment-resisting frames of three-dimension 5,10 and 15 story with  seismic compressed sections as rbs was analyzed as time history by using sap software at the near and far field earthquakes with and without considering the effect of vertical component,then a critical connections in each of the frames was modeled by ansys software and it was analyzed as dynamic under obtained loads from each record(in sap). the study results showed that the vertical component put negative effects on the performance of this type of connection in terms of concentration of stress, strain and ductility.it is necessary to say that the negative effect of the vertical component on the connections at near field earthquakes was comparatively more than at far field earthquakes.