Posted On : 27.08.2016 11:59 pm

## Chapter: __Civil : Structural dynamics of earthquake engineering__

**Pseudo-spectral acceleration**

The parameters have certain characteristics that are of practical interest.

**Pseudo-spectral
acceleration **

Consider a quantity *A* for a SDOF system

Let *A*/*g* be called
base shear coefficient or lateral force coefficient. It is used in building
codes to represent the coefficient by which structural weight is multiplied to
obtain the base shear. *A* is the peak pseudo-acceleration. A
pseudo-acceleration response spectrum is a plot of *A* as functions of *T*_{n}.

The parameters have certain
characteristics that are of practical interest. The pseudo-spectral velocity *S*_{pv}
is close to spectral velocity *S*_{v} for short period structures
and is almost equal to the intermediate periods but is different for long
period structures. A comparison of the NS component of the Northridge
earthquakes is made in Fig. 17.14 for spectral velocity and spectral
acceleration for *Ï‚* = 0.05.
For zero damping, pseudo-spectral acceleration is identical to spectral
acceleration *S*_{a}. However, for damping other than zero these
two are slightly different. Nevertheless, for damping levels encountered in
most engineering applications the two may be considered to be practically
equal.

Evaluation of spectral displacement *S*_{d} by
the use of Eq. 17.9a after numerical integration of Eq. 17.2 is to be carried
out to obtain the time history response *u*(*t*). The corresponding
pseudo-spectral velocity* S*_{pv} and pseudo-spectral* *acceleration
*S*_{pa} can readily be established from Eq. 17.19 and 17.21.

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Civil : Structural dynamics of earthquake engineering : Pseudo-spectral acceleration |