Target Displacement
The fundamental question in the execution of the
pushover analysis is the magnitude of the target displacement at which seismic
performance evaluation of the structure is to be performed. The target
displacement serves as an estimate of the global displacement of the structure
is expected to experience in a design earthquake. It is the roof displacement
at the center of mass of the structure. In the pushover analysis it is assumed
that the target displacement for the MDOF structure can be estimated as the
displacement demand for the corresponding equivalent SDOF system transformed
to the SDOF domain through the use of a shape factor. This assumption, which
is always an approximation, can only be accepted within limitations and only
be accepted within limitations and only if great care is taken in
incorporating in the predicted SDOF displacement demand all the important
ground motion and structural response characteristics that significantly
affect the maximum displacement of the MDOF structure. Inherent in this
approach is the assumption that the maximum MDOF displacement is controlled by
a single shape factor without regards to higher mode effects.
Under the Non-linear Static Procedure, a model directly incorporating
inelastic material response is displaced to a target displacement, and
resulting internal deformations and forces are determined. The mathematical
model of the building is subjected to monotonically increasing lateral forces
or displacements until either a target displacement is exceeded, or the
building collapses. The target displacement is intended to represent the
maximum displacement likely to be experienced during the design earthquake.
Adaptabitility of computer programs
It is well known fact the distribution of mass
and rigidity is one of the major considerations in the seismic design of
moderate to high rise buildings. Invariably these factors introduce coupling
effects and non-linearities in the system, hence it is imperative to use
non-linear static analysis approach by using specialized programs viz.,
SAP2000,STAADPRO2005,ETABS,IDARC,NISA-CIVIL,etc., for cost-effective seismic
evaluation and retrofitting of buildings.
Non-Linear Static Analysis for Buildings
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