Analysis and modelling of the seismic behaviour of high ... - Ingegneria

2. DUCTILITY AND SEISMIC RESPONSE OF STRUCTURES
Figure 2.10. Process for simplified demand estimation Gupta
and Krawinkler (2000)
However, such satisfactory predictions of seismic demands are mostly restricted to
low- and medium-rise structures in which the inelastic action is distributed
throughout the height of the structure (Krawinkler and Seneviratna, 1998; Gupta
and Krawinkler, 2000). None of the invariant force distributions can take into
account the contributions of higher modes to response, or for a redistribution of
inertia forces because of structural yielding and the associated changes in the
vibration properties of the structure. To overcome these limitations, several
researchers have proposed adaptive force distributions that attempt to follow more
closely the time-variant distributions of inertia forces [Fajfar and Fischinger, 1988;
Gupta and Kunnath, 2000]. While these adaptive force distributions may provide
better estimates of seismic demands, they are conceptually complicated and
computationally demanding for routine application in structural engineering
practice. Attempts have also been made to consider more than the fundamental
vibration mode in pushover analysis.
2.4.2 Non-linear dynamic procedure (NDP)
Under the non-linear dynamic procedure (NDP), design seismic forces, their
distribution over the height of the building, and the corresponding internal forces
and system displacements are determined by using an inelastic dynamic analysis
(IDA). The concept was mentioned as early as 1977 by Bertero, and has since
been cast in several forms in the work of many researchers. Recently, it has also
31