Evaluation of the total ductility in steel structures through a nonconvex energy optimization approach

Steel structures are widely used in regions of high seismic activity due to their excellent performance both in terms of strength and ductility. For d esign purposes, in all modern seismic codes a behaviour parameter is introd uced (the so-called q-factor) which represents the energy dissipation capac ity of the structure and is therefore a measure of total ductility. For the evaluation of total ductility, various methods have been proposed in the l iterature. In this paper a method is proposed for the evaluation of total d uctility in steel structures which takes into account the exact form of the moment-rotation curve, including possible softening branches. This task is accomplished using an effective solution algorithm based on the nonconvex optimization theory. Numerical examples demonstrate the applicability range of the proposed approach. (C) 1999 Elsevier Science Ltd. All rights reserv ed.