Introduction

Abstract

Modern codes for seismic design of buildings, bridges, and other civil engineering structures offer to the designer the choice between elastic and inelastic analysis methods, i.e. 'Traditional' methods wherein design is based on the results of a series of elastic analyses that provide linear action effects (moments, shears, axial loads) which are reduced by a global force reduction factor (q-factor in Europe, R-factor in the US) that depends on the overall ductility and overstrength capacity of the structure. Displacement and/or deformation based methods, wherein inelastic deformation demands in the structure are estimated for a given level of the earthquake action (typically expressed in terms of the displacement of a control point of the structure) with the aid of a series of inelastic (i.e. material nonlinear) analyses of either the static or dynamic type. These demands are then checked against the corresponding deformation capacities of the critical structural elements.