Influence of uncertainties on the seismic performance of steel moment resisting frames

The present paper investigates the probabilistic assessment of the seismic performance of steel MRFs designed according to Eurocodes. The considered MRFs are three-and five-storey high and are analysed by the multiple stripe method of analysis by means of sets of earthquake ground motions that depend in frequency content, energy and duration on the value of the selected seismic intensity measure. Additional uncertainties are related to the mechanical properties of steel, dead and live loads and equivalent viscous damping ratio. Different criteria are defined to assess the performance at the achievement of different limit states, in terms of interstorey drifts and damage indexes. To reach a synthetic evaluation of the seismic performances, the mean annual frequency of exceedance of the assigned limit state condition is also reported. Based on a Monte Carlo simulation the paper evaluates the effects of the single uncertainties on the seismic performances and suggests proper modifications to the simplified approach included in FEMA documents to mime the results of a full probabilistic approach