The present work addresses modelling issues in the inelastic analysis of steel frames with reduced beam sections (RBSs), and proposes two simple one-dimensional structural models based on detailed three-dimensional finite-element analysis (FEA) and published testing behaviour of RBSs. The study begins with the FEA of a beam–column assembly with a reduced the beam section, which is compared with test results. More FEA models of RBS assemblies are generated with different configurations so that moment demand at column faces is in the range 80 to 100 per cent of the plastic moment capacity of the original beam section. The study extends to investigate the effect of panel zone when bilinear model is used in the simple structural model. The structural model of the RBS based on the combined FEA and test results captures the prevailing elastic and inelastic behaviour of the RBS assemblies, and correlates very well with the actual performance observed during testing. Copyright © 2001 John Wiley & Sons, Ltd.