3D time history analysis of RC structures versus common methods with attention to the modeling of floor slabs and near versus far-fault earthquakes

摘要

Commercial softwares such as ETABS and SAP, commonly used for the analysis of apartmentrnbuildings, assume the slabs as a rigid or semi-rigid membrane and only roughly allow for the slab’s flexuralrnstiffness using the concept of effective width. These assumptions when further simplified adopting a 2D framernmethod that ignores the torsional effects may produce results that are very different to the full 3D finite elementrnmodeling in particularwhen time-history nonlinear dynamic behavior is sought.The errors could be larger in nearfaultrnearthquakes that often excite higher vibration modes. Recent major earthquakes (Northridge 1994, Kobern1995, Chi-chi 1999 and Bam 2003, etc.) have shown that many near-fault ground motions possess prominentrnacceleration pulses that result in different structural responses for common medium to high-rise buildings.rnIncorrect incorporation of the flexural stiffness of slabs can in some cases underestimate the lateral stiffness. Itrnis shown in the current paper that in a wall-frame structure subjected to near-fault earthquakes, the full 3D timernhistory modeling can significantly vary the analysis results and as such is an important consideration in design.