en Optimal design Optimal design پژوهشي Research <p dir="ltr">Due to several uncertainties &nbsp;which &nbsp;affect structural responses of Reinforced concrete (RC)&nbsp;frames, &nbsp;it is sensibly required &nbsp;to &nbsp;apply &nbsp;a vulnerability analysis tool such as fragility curve.&nbsp;To &nbsp;construct an analytical fragility curve, the incremental dynamic analysis (IDA) method&nbsp;has been extensively used as an applicable seismic analysis tool. To employ the IDA method&nbsp;for constructing fragility curves of RC frames, &nbsp;it is important &nbsp;to know &nbsp;how many records&nbsp;will &nbsp;be &nbsp;adequate &nbsp;to &nbsp;assess &nbsp;seismic &nbsp;risk &nbsp;analysis &nbsp;properly? &nbsp;Another &nbsp;issue &nbsp;is &nbsp;to &nbsp;know &nbsp;how&nbsp;many IDA steps &nbsp;are &nbsp;required for developing an accurate fitted fragility function? For this&nbsp;purpose, &nbsp;two 3D RC frames &nbsp;called &nbsp;3STRCF and 5STRCF have been nonlinearly modeled&nbsp;and 200 2-componets actual records have been considered for &nbsp;the &nbsp;IDA. The results &nbsp;reveal&nbsp;that at least 15 IDA steps &nbsp;are &nbsp;required &nbsp;to &nbsp;reduce &nbsp;fragility function error to less than 5% and&nbsp;10 &nbsp;IDA &nbsp;steps &nbsp;are &nbsp;required &nbsp;to &nbsp;yield &nbsp;less &nbsp;than &nbsp;10% &nbsp;error. &nbsp;In &nbsp;addition, &nbsp;it &nbsp;is &nbsp;revealed &nbsp;that &nbsp;a&nbsp;selection of 100 records is completely adequate to be certain &nbsp; to have &nbsp;an accurate fragility&nbsp;curve. It is concluded that at least 25 records are required to decrease fragility curve error to&nbsp;less than 5% and 15 records to &nbsp;have &nbsp;less than 10%. The closeness of fragility curve error&nbsp;variation for two models and in all limit states show that these results can be generalized to&nbsp;other RC frames.</p> Analytical fragility curve, Incremental dynamic analysis, Error estimation, Reinforced concrete frames. 611 627 http://ijoce.iust.ac.ir/browse.php?a_code=A-10-66-120&slc_lang=en&sid=1 H. A. Tavazo 180031947532846001045 180031947532846001045 Yes A. Ranjbaran 180031947532846001046 180031947532846001046 No