A SENSITIVITY ANALYSIS FOR ENHANCING IDA EFFICIENCY IN FRAGILITY ANALYSIS OF 3D REINFORCED CONCRETE FRAMES

Due to several uncertainties which affect structural responses of Reinforced concrete (RC) frames, it is sensibly required to apply a vulnerability analysis tool such as fragility curve. To construct an analytical fragility curve, the incremental dynamic analysis (IDA) method has been extensively used as an applicable seismic analysis tool. To employ the IDA method for constructing fragility curves of RC frames, it is important to know how many records will be adequate to assess seismic risk analysis properly? Another issue is to know how many IDA steps are required for developing an accurate fitted fragility function? For this purpose, two 3D RC frames called 3STRCF and 5STRCF have been nonlinearly modeled and 200 2-componets actual records have been considered for the IDA. The results reveal that at least 15 IDA steps are required to reduce fragility function error to less than 5% and 10 IDA steps are required to yield less than 10% error. In addition, it is revealed that a selection of 100 records is completely adequate to be certain to have an accurate fragility curve. It is concluded that at least 25 records are required to decrease fragility curve error to less than 5% and 15 records to have less than 10%. The closeness of fragility curve error variation for two models and in all limit states show that these results can be generalized to other RC frames.