Environmental Engineering Reference
In-Depth Information
c
2
¼
H
þ
2V cos a
L
2
ð
12
:
13
Þ
L
2
¼
2V
þ
A
H
A
V
H
ð
12
:
14
Þ
As described above, the fundamental frequency of TLCD depends on five
geometric variables: V, H, A
V
, A
H
, and a. An increasing mass ratio l causes an
increase in the TLCD efficiency. The geometric factors c
1
and c
2
also influence the
efficiency of TLCD. The damping effect reaches its maximum, if the geometric
factor c
1
scaled by c
2
has its maximum. The interaction force of the structure
acting on TLCD increases, if the geometric factor c
1
also increases. Further, if the
TLCD tank has a short height, the liquid can even slop over. To avoid this, it is
better to keep c
1
as low as possible and compensate the efficiency loss by maxi-
mizing the second geometric factor c
2
.
Calculation of Optimal Parameters of Tuned Liquid Column Damper
The optimal parameters of TLCD can be derived by applying tuning criteria of
mechanical mass dampers, which can be easily adapted through analogy approa-
ches. In order to use these equations with TLCD, the parameters of an equivalent
TMD must be calculated. The analogy can be derived from the equation of motion
of TLCD used by substituting liquid stream deflection u by u* = u/c
1
. The mass
ratio l* of TLCD can then be calculated as in Eq.
12.15
. By using l* in the
equations of Den Hartog or Warburton, the optimum frequency and damping ratio
of TLCD can be found.
lc
1
c
2
1
þ
l
ð
1
c
1
c
2
Þ
l
¼
ð
12
:
15
Þ
As the geometric factors c
1
and c
2
also influence the efficiency of TLCD, it is
better to use an extended optimization approach, which also considers the math-
ematical description of the TLCD geometry within the tuning procedure as
described in [
2
,
4
].
Semiactive Tuned Liquid Column Dampers
Semiactive structural control systems can sense and adapt their dynamic behavior
according to the actual condition of the main structure and environment. These
adaptive devices offer a broad range of new application possibilities, which enable
the trend toward design of economically more efficient and more esthetic struc-
tures. The adaptation of the damper parameters can be achieved by various
methods.
