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This paper concentrates on investigating the seismic behaviours of vertically irregular steel special moment frame (SMF) buildings by comparison with the regular counterpart. All buildings in this study were assumed to be located in Los Angeles, and subjected to 20 earthquake ground motions with a seismic hazard level of 2% probability of exceedance in 50 years. The beam–column connections of the buildings were modelled to consider the panel zone deformation. In addition, a ductile connection model accompanied by strength degradation was incorporated to the analysis programme in an effort to obtain more accurate response results. Three types of irregularities (mass, stiffness and strength irregularity) specified as vertical irregularities in the IBC 2000 provisions were imposed to the original building. Nonlinear static and dynamic analyses were performed, and the confidence levels of which the performance objective will be satisfied were calculated as well. The effects of different irregularity types and levels on the seismic behaviours of the buildings were investigated and discussed in terms of the height‐wise distribution of storey drifts, maximum storey drift demands, global collapse storey drift capacities and confidence levels. Copyright © 2010 John Wiley & Sons, Ltd.

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This article presents the results of a research project aimed at investigating the seismic performance criteria of beam-column connections in reinforced concrete (RC) moment frames. A total of 112 RC beam-column connection tests were examined in detail. All the test specimens were qualified as either special moment frame (SMF) or intermediate moment frame (IMF) connections, based on the design and detailing requirements of ACI 318-08 [2008, Ch. 21]. The performance acceptance criteria, originally defined for steel moment frame connections in the 1997 edition of the AISC Seismic Provisions, were employed to evaluate the seismic performance of the RC connection specimens. Most of the specimens that satisfied the ACI 318 design requirements applying for SMFs were found to be ductile up to a plastic drift of 3% without any major degradation in strength, which satisfied the AISC performance acceptance criteria. This is most likely attributed to the stringent ACI 318-08 requirements for joints in SMFs. On the other hand, more than 40% of the IMF connections were not satisfactory based on the AISC criteria applying for steel IMF connections. Joint shear stress level showed more significant effect on their seismic performance than the column-to-beam flexural strength ratio. It is believed that inadequate joint detailing prevented these connections from developing their full beam flexural capacity, which resulted in premature strength deterioration and subsequent failure. Based on the findings, it is recommended that design requirements for beam-column connections in RC IMFs should be revisited and enhanced; otherwise, the R-factor assigned for RC IMFs should be somewhat reduced to accommodate their smaller ductility than intended by the ACI 318 requirements.