ABSTRACT
Abstract The evaluation of global ductility by means of the use of the q-factor is now-a-day a comun practice in the new generation seismic codes. But, there are still many incongruicies in the codification, which must be eliminated in the next revisions. Some proposals for improving the existing provisions are give in this paper. Keywords: Global Ductility, Q-Factor, Collapse Mechanism
1. Introductive remarks on the existing codification
The goal of any codification is to provide design provisions which ensure public safety, i.e. to safeguard against major failure and loss of live, with limitation of damage for maintenance of the function and permission for easy repair. Based on this premise, the design methods must provide criteria for behaviour control of structures during the seismic action. The design philosophy is based on the concept that during severe earthquakes the energy input is dissipated through inelastic deformations. Due to this dissipation, the design forces can be reduced by means of the behaviour factor, namely q-factor. The exact evaluation of this factor requires several dynamic analyses for different ground motions and this is a very cumbersome and expensive way. The possibility to evaluate the q-factor by means of some simple methods adequate to be insert in a code represents an urgent need. But we have to recognize that this requirement is very difficult to be achieved, because the energy dissipation depends both on the
486 Gioncu and Mazzolani
local and global ductility. For both ductilities, the buckling phenomena in plastic field of deformations play a fundamental role.
