A simple and straightforward method of analysis is presented for the design of semi-rigidly connected steel frames. The procedure may be adopted for use within either traditional manual, or computerised elastic or plastic analytical techniques including commercially available software programs. The method is a simplification of the author's more rigorous beam to column connection, quadlinear, moment-rotation relationship approach to frame design, within a linear accumulative and summation matrix analysis1. This simplified method producesslightly more conservative results at frame collapse than the original procedure, yet still provides fabrication responsive, economic and efficient solutions. All of this can be achieved from modified conventional analytical techniques, or should a computerbased solution be preferred, the method may be converted into an established programmable numerical procedure without too much difficulty. Alternatively, the bi-linear parameters associated with this method, namely elastic rotational stiffness and plastic moment capacity, may be introduced into commercially available software where elastic spring stiffness and plastic moment plateau modelling facilities exist. In addition, the assumed simplified bilinear behaviour is also compatible with conventional shakedown analyses, where variable repeated loads are more critical than permanent static loads.
John Graham, PhD, BSc, CEng, FIStructE
Scape System Build Ltd, Nottingham