Environmental Engineering Reference
In-Depth Information
Table 13.3 EOG input: peak
response of the FB structure
and of the SA case using the
2VAR controller
Case max|r| max|x|
Fixed base 51 MPa 39 mm
Semi-active 2VAR 36 MPa 45 mm
FB ? SA
-29 % +15 %
Percentage variation from the first to the second condition
will be subjected to high velocity wind buffeting, which is herein referred to as
''parking'' (PRK) load case.
The equivalent base acceleration time history in Fig.
13.16
has been considered
to assess the effectiveness of both SA control strategies, reproducing such input
signal by the shaking table. In the following, the results obtained with the CLES
controller first, then with the 2VAR control logic, are discussed. Since the long
duration of the input (more than 2 min), a 10 s time window has been chosen to
plot the response time-histories, not to lose their readability and to show in a
clearer manner how the controllers worked.
For the PRK load case, the control activity resulted to be higher than in the
EOG case. The control algorithms switched on or off the MR devices many more
times, making them able to better dissipate the input energy. From this perspective,
the higher acceleration demand (value and number of peaks) corresponding to the
PRK load case justifies the better response reduction achieved by the same SA
system if compared to the EOG input.
13.6.2.1 CLES Controller: Response Reduction Under the PRK
Load Case
Figure
13.19
shows the results in terms of base stress, top displacements, com-
mand voltage, and forces, respectively desired and actually exerted by MR
dampers, within the selected 10 s time window. Also in this case, the controller
has been able to drive MR dampers to react similarly to the ideal device, i.e., the
one that would exactly output the desired control force u(t). With reference to
the assumed sample time window, Fig.
13.19
clearly shows that the CLES con-
troller lead to a strong reduction of the base stress, without significantly altering
the response in terms of displacement. Confirming this finding, Table
13.4
shows
peak values, over the entire input duration, of base stress and top displacement and
their percentage variation in respect to the FB case. The peak base stress results to
be reduced of 48 %, while the peak top displacement did not change appreciably.
