Dependency of building fragility to source mechanisms of records selected for incremental dynamic analysis
Incremental Dynamic Analysis (IDA) is a computational procedure that allows a thorough assessment of seismic demand and capacity by using a series of non-linear dynamic analyses using suitably scaled earthquake records. An IDA curve for a particular earthquake record is developed by choosing a suitable engineering demand parameter (EDP) and intensity measure (IM), then scaling the record to a range of IM values, conducting non-linear dynamic analyses and plotting the IM vs. EDP curve. Previous research on IDA has used a suite of medium intensity earthquake records scaled from 0.1- 2.0g PGA. In scaling the records, the acceleration amplitude is multiplied by the scaling factor. Hence, the duration and frequency content of the scaled records are unchanged. Nevertheless, using the medium suite of earthquake records does not account for the smaller time duration and higher frequency content observed in high intensity excitations. Hence, rather than using one set of records to represent all possible ranges of earthquake intensity, it is more logical to use different records which are more representative of the scaled intensity range. In this study, IDA of a multi-storey concrete building is conducted by using two different suites of ground motions recorded during earthquakes originating from (1) near source and (2) medium source mechanisms. Results show that using a single suite of medium source records can potentially lead to conservative predictions of behavior.