Optimal Passive Damper Positioning Techniques: State-of-the-Art - Design Optimization of Active and Passive Structural Control Systems - page 87

and a short insight into other damping models is
also presented. In order to investigate the effect
of the different damping models, a comparative
numerical study is also performed. Discussions
on Realism of Linearity Assumption investigates
the validity of the linearity assumption (which is
inherent in most of the previous studies on optimal
positioning of dampers) in a realistic situation.
Finally, the chapter ends with conclusions in the
final section.

optimal positioning; and the second study is carried
out on a twenty storey reinforced concrete frame
emphasizing the relevance of optimal positioning
in more realistic terms.
Figure 1 depicts the response acceleration
reduction obtained as a result of an increase in
the equivalent viscous damping. The solid curve
represents the conventional elastic response spec-
tra obtained with 5% equivalent viscous damping.
The dotted curves represent the reduced equivalent
elastic spectral ordinates obtained with higher
values of equivalent viscous damping.
It could be observed that though there is a
reduction in the peak acceleration response, a
uniform reduction in response is not guaranteed;
an increase in response is observed in some pe-
riod ranges, which could be different for different
earthquakes. This is a clear indication that an
increase in added damping may not always result
in a response reduction.
In order to further emphasize this fact in
quantitative terms, an analytical investigation is
carried out on a twenty storey reinforced concrete

SIGNIFICANCE OF OPTIMAL
DISTRIBUTION

In practice, there is often a belief that an increase
in damping would always result in a better perfor-
mance, which may not always be true. In order to
justify this argument we present two studies; the
first is based on the reduction of elastic response
spectra of a record from the Chi-Chi earthquake
by increasing the equivalent viscous damping
which conceptually illustrates the significance of

Figure 1. Elastic response spectra of a Chi-Chi earthquake ground motion with varying levels of damping