A drift-correlated ground motion intensity measure: Application to steel frame buildings

Estimations of seismic risk in urban areas should include quantifications of the expected damage to civil structures subjected to earthquakes. In buildings, this quantification depends on the maximum inter-story drift (MIDR), among other aspects. In this study, the correlation between several intensity measures (IMs) and the maximum inter-story drift of steel structures was investigated. Three steel frame buildings of 3, 7 and 13 stories were used as a testbed. These buildings were modelled as 2D framed structures. For the seismic hazard, forty strong ground motion pairs were selected (80 individual horizontal components) from the Italian database. These records were scaled to a specific peak ground acceleration (PGA) and matched to a design spectrum from Eurocode 8. Nonlinear dynamic analysis was used to estimate the seismic response of the structures. Thus, 720 nonlinear dynamic analyses (NLDA) were performed [3 structures x (80 as recorded accelerograms + 80 scaled records + 80 matched records)]. Preliminary results indicate that PGA and MIDR show the worst correlation. A higher correlation was observed for peak ground velocity, root-mean-square velocity and specific energy density intensity-based measures. Finally, a new IM, which is highly correlated with MIDR, is proposed. This IM is called I Delta-PGV and considers both the PGV and the significant duration.