Probabilistic assessment of ductility for earthquake resistant design of steel members

An appropriate supply of member ductility is an important ingredient for su ccessful earthquake resistant design since it enables the primary objective of a well controlled dissipative collapse mode to be realised, without exc essive strength requirements being imposed on nondissipative components. As with other performance criteria, uncertainties influence the actual ductil ity supply, with material variability being a key contributor. This paper e xamines the effect of this variability on cantilever tip deflection ductili ty, based on an interactive local buckling model developed for steel member s subjected to large inelastic excursions. Probabilistic models for yield s tress and strain hardening variability are introduced in a FORM reliability analysis, and their influence studied for a wide range of steel beam and c olumn members. The results quantify material variability on member response , and are readily presented for design use through the definition of genera lised parameters involving cross-section properties and material uncertaint y coefficients. (C) 1999 Elsevier Science Ltd. All rights reserved.