Seismic reliability of steel framed buildings

This study evaluates the seismic reliability of eccentrically braced frame (EBF) and buckling-restrained braced frame (BRBF) systems in comparison with that of moment-resisting frame (MRF) systems. In detail, a series of three-dimensional nonlinear time-history analyses was carried out for six example buildings. The effectiveness of braced frames was assessed in 6- and 20-story steel office buildings. Two ensembles of ordinary and near-source earthquake ground motions were evaluated with a vector-valued intensity measure. The results show that the effectiveness of braced frames can vary significantly with ground motions and building rises. The added braced frames help to reduce story drifts, decreasing the probability of failure against ordinary ground motions. The effect is particularly obvious for low-rise buildings. On the other hand, the pulse-like feature of near-source ground motions decreases the drift demands on MRF systems but increases the drift demands on EBF and BRBF systems. As a result, the added braced frames can help to resist near-source ground motions, but only to a limited extent. (C) 2009 Elsevier Ltd. All rights reserved.