ON THE USE OF BEAM-COLUMN INTERACTION FORMULAE TO DESIGN AND SAFETY CHECK MEMBERS INTEGRATED IN STEEL FRAME STRUCTURES

摘要

The application of the so-called Level 1 and Level 2 beam-column interaction formulae to members integrated in plane frame structures is presented and discussed. Issues concerning the role played by the appropriate choice of buckling length and "equivalent moment factor" values, both in terms of safety and accuracy, are addressed. In addition, an alternative methodology to use the above formulae is proposed, which is based on genuine second-order results. The concepts and procedures dealt with in the paper are illustrated by means of their application to two simple (two-bar) structural systems. For several geometry/loading combinations, different approaches to the use of the interaction formulae are considered and the values provided by each of them are discussed and compared with "exact" results, obtained from frame second-order plastic zone analyses (including member imperfections) performed by the FEM code ABAQUS. On the basis of this comparative study, a number of conclusions are drawn concerning the proper use, accuracy and validity of both interaction formulae and, in particular, it is shown that the proposed alternative methodology consistently yields accurate and conservative results.