EFFECT OF SOFT FLOOR ON STRUCTURAL BEHAVIOR OR RESPONSE CORRECTION FACTOR

Structural behavior or response correction factor, is a quantity assigned to inelastic performance of the structure, and demonstrates its reserve stability in inelastic stage. Equivalent static force is obtained on the basis of the behavior factor (R-factor) in majority of the regulations. This factor leads to several folds of decrease in lateral forces generated by earthquake. To obtain the structural behavior factor, the structure must undergo nonlinear static analysis (pushover). The parameters required for calculation of the structural behavior are acquired by bilinearization of the curve of relative story drift versus base shear of the structure. We created 6 models and analyzed them in SAP2000 software including; A five-story structure without a soft floor, with soft ground floor, with soft first floor, with soft second floor, with soft third floor, and with soft fourth floor. Following creating and analysis of these models, obtaining the pushover curve and calculating their behavior factor, it was observed that: 1) With the presence of a soft floor in the structure, the behavior factor decreases considerably. 2) This decrease is more remarkable with higher soft floors. 3) The maximum decrease in the behavior factor takes place in soft middle floors.