3D time history analysis of RC structures versus commercial Me thods with attention to the modeling of floor slabs near versus far-fault earthquakes

commercial softwares as ETABS and SAP commonly used for the analysis of apartment building assume the slabs as a rigid or semi rigid membrane and only rough1 a1-low for the slab's flexural stiffness using the concept of effective sidth. These assumptions when further simplified adopting a 2D frame method that ignores the torsional effects may produce results that are very different to the full 3D finite element modeling in particular when time -history nonlinear dynamic behavior is sough . the errors could be larger in near fault earthquakes that often excite higher vibration modes. recent major earthquales northiridge 1994, kobe 1995 , chi-chi 1999 and bam 2003 , etc. have shown that many near fault ground motions possess prominent acceleration pulses that results in different structural responses for common medium to high -rise buildings.