A GENERALIZED DESIGN-BASED ELASTOPLASTIC ANALYSIS OF STEEL FRAMES BY SECTION ASSEMBLAGE CONCEPT

In the advanced elastoplastic analysis of steel frames, the linear int eraction function for axial force and moment is commonly used for the lump plasticity model in assessing the capacity of a section. This lin ear interactive method is conservative and classified as the simplifie d approach in some national design codes such as BS5950. This paper pr oposes a more rigorous and rational method of analysis by considering the section capacity under moment and axial force via the modelling of an I or a H section by three rectangular strips. It produces a more c onsistent, accurate and rational assessment of section strength. It is convenient: to use as it does not require the modification of the lin ear interaction curve under high or low axial load, in contrast to the load and resistance factor design specification. The analysis output by the proposed method meets the design code requirement for practical design under the catalogue of rigorous approaches in BS5950. Also, th is method considers various effects such as deteriorating stiffness, i nitial imperfection, residual stress and geometrical and material nonl inearities simultaneously. The distinct advantage for the proposed met hod is that it does not use the conservative linear axial force moment interactive formula or its empirically modified form for inelastic an alysis. Instead, it employs a refined technique for the formulation of the full yield surface based solely on the section properties, which is general, rational and produces a more economical design. (C) 1997 E lsevier Science Ltd.