Advances in Seismic Design Methodologies - Earthquake Engineering for Structural Design - page 428

428 Earthquake Engineering for Structural Design

Figure 9.27 Interstory drifts determined using dynamic and push-over analyses
(after Pinho et al, 2005)

The traditional push-over procedure is confronted with many criticisms, mainly
concerning:
(i) The load pattern with which the push-over analysis is carried out, based only
on the fundamental vibration mode of the elastic system;
(ii) The ignorance of structural rigidity changing due to higher vibration modes,
and consequently, the changing of load pattern features.
Due to these weaknesses of the traditional push-over procedure, some new
methodologies were developed in the last time.
Multimode load pattern of push-over procedure. A methodology to determine the
structure response by combination of the vibration modes using different participation
factors is presented in Section 9.5.4 for elastic analysis. The same idea is extended for
static inelastic push-over method, by a combination of push-over values determined for
each vibration mode using different participation factors. The dynamic behavior of the
majority of the structures is only affected by a small number of vibration modes. This
procedure can be reduced to the determination of a load pattern by the combination of
the ones corresponding to each vibration mode, obtained from a linear elastic analysis
of the structure, using the different participation factors (Almeida and Caneiro-Barros,
2003). This procedure considers the lateral loads in predetermined pattern of the most
important vibration mode, but ignores the redistribution of inertia forces due to