The impact of using scaled ground motion records for seismic capacity assessment

Abstract eng:
Incremental Dynamic Analysis (IDA) is a powerful method that involves performing a series of nonlinear response history analyses with a multiply scaled suite of ground motion records. The well-known limitation of the IDA is that the suite of ground motion records is incrementally scaled-up until the structure collapses. This practice usually results to unrealistic scale factors introducing bias on the structural performance estimation, especially for medium-to-large seismic intensity levels. Scaling is often adopted due to the lack of natural records for large magnitudes and/or small distances from the fault rupture location. After an extensive survey of the available online ground motion databases, a large set of natural and synthetic accelerograms is used to investigate the structural response and assess the bias IDA introduces. Broadband ground motion simulations are next conducted for rupture scenaria of weak, medium and large magnitude events (Mw=5÷7.5). A three-storey and a nine-storey steel moment resisting frame with beam hinges are used as the testbed for our investigations. Using appropriate nonlinear regression techniques estimates of the capacity curve are obtained and compared to that of IDA.

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