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Journal of Civil Engineering and Architecture 11 (2017) 455-467 doi: 10.17265/1934-7359/2017.05.006
Study on Improvement of Seismic Performance of
Transmission Tower Using Viscous Damper
Masayuki Matsumoto1, Akira Kasai2, Taiji Mazda3, Nobuyuki Ishida4 and Yuki Ito5
1. Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan;
2. Associate Professor, Department of Civil Engineering, Kumamoto University, Kumamoto 860-8555, Japan;
3. Professor, Department of Civil Engineering, Kyushu University, Fukuoka 819-0395, Japan;
4. Japan Steel Tower Co., Ltd., Tokyo 136-0075, Japan;
5. Japan Steel Tower Co., Ltd., Fukuoka 808-0023, Japan
Abstract: The earthquake resistance of transmission tower has been often discussed from the viewpoint of reinforcing the foundation of steel tower, but there are also few studies considering the damping characteristics of the tower. This paper focuses on the viscous damper which has been adopted for seismic reinforcement of bridges in recent years. The purpose of this study is to improve the seismic performance of steel tower by giving the high damping to the tower. We construct a single tower model considering the influence of transmission line, and then simulate the vibration characteristics and seismic behavior of the tower by the eigenvalue analysis and the dynamic response analysis. The results show that the transmission tower with viscous damper can reduce its own response effectively and drastically. This research concludes that it is necessary to consider the extreme increase of steel tower’s response depending on the seismic wave and the collapse of steel tower can be avoided by using the optimum damper in the design of the transmission tower.
Key words: Dynamic analysis, earthquake, response reduction, seismic damper, transmission tower.
1. Introduction
The power supply system is mainly composed by
power plant, power transmission, transformation, and
distribution facilities. It is a necessary condition that
the functions of all these facilities work well together
for stable supply of electric power. Maintaining the
functions of these systems is an extremely important
issue in order to stabilize the power supply that
supports city life.
Currently, the design of power transmission towers
in Japan is mainly based on “Design Standard on
Structures of Transmission (The Institute of Electrical
Engineers of Japan)” (hereinafter referred to as
JEC-127) [1]. When the first Muroto Typhoon hit the
Kansai region in September 1934, and Ise Bay
Typhoon hit the Nagoya region in September 1959 and
Corresponding author: Masayuki Matsumoto, master;
research fields: earthquake engineering, and seismic engineering. E-mail: [email protected].
the Osaka region in September 1961, respectively,
transmission facilities were seriously damaged.
Consequently, these facilities designed by replacing
the wind and snow load as the static load have been
considered to be sufficiently safe for the seismic load.
Because the seismic load may exceed the wind load
only for special structures, JEC-127 has seismic design
based on the seismic intensity method and dynamic
response analysis. The Ji-Ji Earthquake occurred in
September 1999, and the collapses of power
transmission towers were reported in many cases, so
the transmission tower suffered unprecedented damage
by the earthquake. Despite the fact that the design
specification of transmission towers in Taiwan is
slightly severer than that of Japan, many damages of
steel towers have been reported in central Taiwan. That
resulted in extensive damages to Taiwan’s power
supply system. In addition, the 2011 off the Pacific
Coast of Tohoku Earthquake occurred in March 2011,
steel towers close to the Fukushima Daiichi Nuclear
D DAVID PUBLISHING
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
456
Power Plant collapsed. And that caused serious
damage to steel towers around the Tohoku region.
After the collapse was reported to be caused by tsunami
and slope collapse, the risk of destruction of
transmission tower was reconfirmed again.
Studies [2-4] conducted in the past focused on that
steel towers collapsed, even Taiwan’s design
specification was slightly stricter than that of Japan.
And the importance of seismic performance
evaluation of steel towers was pointed out. In previous
study [5], the effects of ground differential settlement
to seismic performance of transmission towers were
confirmed by using a single tower model. And the
influence of adjacent transmission towers was
clarified in the past study [6]. The previous study [7]
described the development of simplified model for the
transmission tower considering the effects of
transmission lines and viscous dampers. Dynamic
response analysis was conducted by using some types
of models. Differences of dynamic behavior between
each model were compared. In this research, the
evaluation on the earthquake resistance of steel tower
will be examined based on the seismic waves observed
at the Southern Hyogo Prefecture Earthquake (referred
to as the Hyogo Earthquake) and at the 2011 off the
Pacific Coast of Tohoku Earthquake (referred to as the
Tohoku Earthquake). In this paper, we focus on the
viscous damper adopted for seismic reinforcement of
bridges in recent years. Our study will examine to
improve the seismic behavior of steel tower with
viscous damper by giving the high damping.
2. Analysis Model and Conditions
2.1 Target Structure and Analysis Model
In this research, the modeling was carried out based
on the structural data of transmission tower which has
been generally adopted in Japan. The transmission
tower as the target structure was the suspension type of
equal angle steel tower (220 kV), and the structural
diagram of analysis model is shown in Fig. 1. This
model is the steel tower that four legs were equal in
length (the number of nodes is 245, and that of
elements is 672). Here, the characters from A to D in
the figure represent the position of principal members,
and the numbers in the figure represent the panel
number. In addition, assuming the situation which
the same steel towers were arranged continuously and
Fig. 1 Suspended steel tower.
xy
z
AB C D
38.4(
m)
5.7(m)
Transversal
Longitudinal
Vertical
Small number side
Larger number side
12
345
6789
1011
12
13
14
15
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
457
linearly, the length of span between steel towers was
supposed to be 350 m on both sides. All of principal
members, diagonal members, horizontal members, and
other auxiliary members were modeled as the linear
materials of three dimensional beam elements
(Young’s modulus: 205.9 GPa, Poisson’s ratio: 0.3).
In this model, transmission lines were approximately
modeled by single degree of freedom mass and spring
in each direction. The mass was calculated by the
length of transmission lines based on distance of
adjacent towers. And, the spring constant was
determined from the vibration period of transmission
lines. Regarding the damping of materials as the equal
angle steel, it was known that the value of 1.7% was
obtained when the amplitude was small and the value
of 3.3% to 3.8% when the amplitude was large by the
Sawabe’s vibration test of steel tower. Therefore, in
previous studies, it was assumed to be 2%. Based on
these assumptions, it was set to 2% in this study as
well. Referring to the damping constant of
transmission line, it was concluded that it was 0.4%
from the result of Iwama’s vibration test. The
modeling of transmission line was conducted based on
the previous research. Fig. 2 shows the conceptual
diagram of modeling the transmission lines and the
suspended insulators. The total of two armrests
attaching the ground lines were on the left of tower
top and on the right of tower top, and the rest armrests
were attached to the power line. The mass in the
longitudinal direction was directly attached to each
armband, and the one in the transversal and vertical
direction was attached to each armrest together with
the spring.
2.2 Outline of Analysis Conditions
In the previous research, there were no differences of
responses between the case in which the base of tower
was fixed and the case which was modeled including
the foundation ground. Therefore, in this study, the
foundation was modeled as completely fixed. The
structural analysis program T-DAP III was used as an
analysis software. As the method of eigenvalue
analysis, subspace method was applied. And we
calculated the required degree under the judgment of
Fig. 2 Conceptual figure of modeling transmission line.
mx
mx
mx
mx
mx
mx
mx
mx
mz
mz
mz
mz
mz
mz
mz
mz
my
my
my
my
my
my
my
my
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
458
effective mass ratio. As the dynamic analysis method,
the direct integration method based on the Newmark β
method (β = 0.25) was applied, and the time interval of
integration was 0.002 s. Furthermore, Rayleigh
damping was defined from the principal modes in
which the effective mass ratio obtained by eigenvalue
analysis was high. The combination of primary natural
frequency and 50 Hz was adopted so that the
combination of the first reference frequency and the
second reference frequency did not show excessive
damping. The input seismic waves were strong motion
records observed at the Hyogo Earthquake and at the
Tohoku Earthquake. And these seismic waves were
input as a single one in the longitudinal direction.
Fig. 3 shows the time history of acceleration.
Based on the method above and the vibration mode
as the result of eigenvalue analysis, four types of
analysis model considering the effect of viscous
dampers were investigated. Figs. 4a-4d show the
models with viscous dampers in each analysis.
Dampers were assembled under the lowest arm
considering deformation of vibration mode of the
tower. Damper used here was velocity dependent type.
Fig. 4e shows the nonlinear model with the -th
power of velocity. The “VL” drawn by the shaded
area in this figure means the limited velocity of elastic
behavior. Eq. (1) shows the characteristics of damping
force in the nonlinear region. The capacity of damping
Fig. 3 Time history of input seismic waves: (a) Jmakobe NS (The Hyogo Earthquake); (b) Tsukidate NS (The Tohoku Earthquake); (c) Hirono (The Tohoku Earthquake).
-1500
-1000
-500
0
500
1000
1500
0 5 10 15 20
Acc
eler
atio
n (
gal)
Time (sec)
JMAKOBE NS------------------------Max = 817.8(gal)
-3000
-2000
-1000
0
1000
2000
3000
0 30 60 90 120 150
Acc
eler
atio
n(g
al)
Time (sec)
TSUKIDATE NS--------------------Max = 2,699.9(gal)
-1500
-1000
-500
0
500
1000
1500
0 30 60 90 120 150
Acc
eler
atio
n(g
al)
Time (sec)
HIRONO NS-----------------------Max = 1,115.9(gal)
(a) JMAKOBE NS (The Hyogo Earthquake)
(b) TSUKIDATE NS (The Tohoku Earthquake)
(c) HIRONO NS (The Tohoku Earthquake)
(a)
(b)
(c)
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
459
Fig. 4 Analysis model with viscous damper: (a) Model A-1; (b) Model A-2; (c) Model B-1; (d) Model B-2; (e) characteristics of damping force.
force of each damper is 100 kN: ∙ (1)
where: : damping force (kN);
: damping coefficient (kN/(kine)α);
: velocity (kine);
: 0.1
3. Results of Dynamic Response Analysis
Table 1 shows the result of eigenvalue analysis for
model without damper, and Fig. 5 shows the main
mode diagrams of principal vibration in the
longitudinal direction. In addition, Fig. 6 shows the
Fourier amplitude spectrum of response acceleration
at the tower top of principal member A.
Focusing on the peak frequency by the comparison
between Table 1 and Fig. 6, the tower is controlled
only by the primary mode in case of Jmakobe NS,
only the secondary mode is excited in case of
Tsukidate NS, and the vibrations of both modes are
excited in case of Hirono NS. Thus, depending on the
(a) Model A-1 (b) Model A-2
(c) Model B-1 (d) Model B-2
: Damper
h =
15.
5(m)
10
11
12
10
11
12
10
11
12
10
11
12
-VL
VL
Linear
Nonlinear
Nonlinear
-100
-75
-50
-25
0
25
50
75
100
-15 -10 -5 0 5 10 15
Dam
ping
for
ce(kN
)
Velocity (kine)
Damping force Velocity Curve
(e) Characteristics of damping force
(a) (b)
(c) (d)
(e)
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
460
Table 1 Natural period by eigenvalue analysis (without damper model).
Mode Period (s) Frequency (Hz) Effective mass ratio (%)
Transversal
Line 1st 7.576 0.132 25
Tower 1st 0.505 1.980 30
2nd 0.143 7.000 15
Longitudinal Tower 1st 0.725 1.380 64
2nd 0.187 5.360 24
Vertical Line 1st 7.519 0.133 36
Tower 1st 0.057 17.500 38
Fig. 5 Vibration mode in the longitudinal direction: (a) 1st mode 1,380 Hz; (b) 2nd mode 5,360 Hz.
difference of input seismic wave, the vibration mode
of steel tower differs. When the seismic wave
Jmakobe NS is input, the vibration is controlled only
by the primary mode. This means that the response of
steel tower increases.
Fig. 7 shows the time history of displacement at the
tower top of principal member A in case of model
without damper. Although the maximum values of
input accelerations in cases of Tsukidate NS and
Hirono NS are larger than those of Jmakobe NS, the
maximum value of response displacement of Jmakobe
NS is about three times of the value of Tsukidate NS
and about four times of the value of Hirono NS. These
results can be estimated from the above relationship
between the result of eigenvalue analysis and that of
Fourier amplitude spectrum. This indicates that the
target structure was sensitively affected in case of the
Hyogo Earthquake than in case of the Tohoku
Earthquake.
Figs. 8-10 show the time history of displacement at
the tower top in the model with damper. From the
results of Jmakobe NS, the responses of tower top are
extremely reduced in Model A-1 and Model B-2
comparing with the model without damper. On the
other hand, the reduction effects of response by
dampers are relatively small in Model A-2 and Model
B-1. Furthermore, the early convergence of tower’s
response is recognized in model with damper. This is
one of the features of reduction effect by the viscous
damper. As the results of Tsukidate NS, the responses
are reduced in Model A-1, Model A-2 and Model B-2,
comparing with the model without damper. However,
the reduction effect of response by dampers is
relatively small in Model B-1. About the results of
Hirono NS, the responses are reduced in Model A-1,
Model B-1 and Model B-2, comparing with the model
without damper. The reduction effect by dampers is
small in Model A-2. Referring to the response
displacement of tower top, it is revealed that the effect
of reducing the response is great in Model A-1 and
Model B-2 for seismic waves.
Fig. 11 shows relationship between maximum
(a) 1st mode 1.380Hz (b) 2nd mode 5.360Hz(a) (b)
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
461
Fig. 6 Fourier amplitude spectrum of response acceleration (without damper model): (a) Jmakobe NS; (b) Tsukidate NS; (c) Hirono NS.
Fig. 7 Time history of tower top displacement (without damper model): (a) Jmakobe NS; (b) Tsukidate NS; (c) Hirono NS.
1.367(Hz)
0
1000
2000
3000
4000
5000
6000
7000
8000
0 1 2 3 4 5 6 7 8 9 10
Four
ier
am
plitu
de s
pect
rum
(gal・s
ec)
Frequency (Hz)
(a) JMAKOBE NS
5.365(Hz)
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
0 1 2 3 4 5 6 7 8 9 10
Four
ier
am
plitu
de s
pect
rum
(gal・s
ec)
Frequency (Hz)
1.385(Hz)
0
1000
2000
3000
4000
5000
6000
0 1 2 3 4 5 6 7 8 9 10
Four
ier
am
plitu
de s
pect
rum
(gal・s
ec)
Frequency (Hz)
(b) TSUKIDATE NS (c) HIRONO NS
-50
-25
0
25
50
0 5 10 15 20
Dis
plac
emen
t (c
m)
Time (sec)
JMAKOBE NS----------------Max = 46.1(cm)
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
TSUKIDATE NS--------------Max = 15.5(cm)
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
HIRONO NS-----------------Max = 12.0(cm)
(a) JMAKOBE NS
(b) TSUKIDATE NS (c) HIRONO NS
(a)
(b) (c)
(a)
(b) (c)
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
462
Fig. 8 Time history of tower top displacement (with damper model/Jmakobe NS): (a) Model A-1; (b) Model A-2; (c) Model B-1; (d) Model b-2.
Fig. 9 Time history oftowertop displacement (with damper model/Tsukidate NS): (a) Model A-1; (b) Model A-2; (c) Model B-1; (d) Model B-2.
-50
-25
0
25
50
0 5 10 15 20
Dis
plac
emen
t (c
m)
Time (sec)
Model A-1/JMAKOBE NS------Max = 15.9(cm)
Without Damper
With Damper
-50
-25
0
25
50
0 5 10 15 20
Dis
plac
emen
t (c
m)
Time (sec)
Model A-2/JMAKOBE NS------Max = 39.7(cm)
Without Damper
With Damper
-50
-25
0
25
50
0 5 10 15 20
Dis
plac
emen
t (c
m)
Time (sec)
Model B-1/JMAKOBE NS------Max = 29.0(cm)
Without Damper
With Damper
-50
-25
0
25
50
0 5 10 15 20
Dis
plac
emen
t (c
m)
Time (sec)
Model B-2/JMAKOBE NS------Max = 19.0(cm)
Without Damper
With Damper
(a) Model A-1 (b) Model A-2
(c) Model B-1 (d) Model B-2
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
Model A-1/TSUKIDATE NS----Max = 11.0(cm)
Without Damper
With Damper
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
Model A-2/TSUKIDATE NS----Max = 10.3(cm)
Without Damper
With Damper
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
Model B-1/TSUKIDATE NS----Max = 13.8(cm)
Without Damper
With Damper
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
Model B-2/TSUKIDATE NS----Max = 11.4(cm)
Without Damper
With Damper
(a) Model A-1 (b) Model A-2
(c) Model B-1 (d) Model B-2
(a) (b)
(c) (d)
(a) (b)
(c) (d)
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
463
Fig. 10 Time history of towertop displacement (with damper mode/Hiponons): (a) Model A-1; (b) Model A-2; (c) Model B-1; (d) Model B-2.
compression axial force of principal member A and
the height of tower. The red line shows yield axial
force of principal members, and the blue line shows
allowable axial force. Regarding the result of model
without damper, because the steel tower vibrates in
primary mode, the axial force is large at the bottom in
case of Jmakobe NS. Similarly, because the steel
tower is controlled by the secondary mode, the axial
force decreases in the middle part of the tower in case
of Tsukidate NS. Furthermore, in case of Jmakobe NS,
as same as the result of Fig. 8, the axial forces of
principal members are extremely reduced in Model
A-1 and Model B-2, comparing with the case of
model without damper. Axial forces of principal
members in Model A-2 are as the same as the case of
model without damper. The reduction effect of
response by dampers is not recognized in this case. In
case of Tsukidate NS, the response is reduced in all
models, and Model B-2 has the largest reduction in
particular. As the results of Hirono NS, responses of
all models decrease. Especially, Model A-2 which had
a low effect of reducing the response displacement at
the top even shows the reduction effect.
The damping effect is evaluated by changing the
resistive force of viscous damper from reference force
(100 kN) to 50 kN and 150 kN. As the representative
of four models, the result about Model A-1 is notable.
Fig. 12 shows the hysteresis curve of viscus damper
which is relationship between velocity and damping
force for each model in case of Jmakobe NS. Fig. 13
shows the hysteresis curve drawn from the
relationship between displacement and damping force.
The estimated hysteresis curve is obviously drawn. In
the model with resistive force of 100 kN, a solution
diverges when the time interval of integration was
0.002 s, and a stable solution was obtained at the time
interval of 0.0004 s. In the case of 150 kN, that was
obtained when the time interval was 0.000005 s.
Therefore, these models are highly nonlinear.
Table 2 shows the maximum displacement at the
tower top and the reduction rate for each model in the
case of Jmakobe NS. The model with resistive force of
100 kN shows the higher reduction rate than that of
50 kN. The response displacement is reduced even with
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
Model A-1/HIRONO NS--------Max = 8.3(cm)
Without Damper
With Damper
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
Model A-2/HIRONO NS-------Max = 11.0(cm)
Without Damper
With Damper
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
Model B-1/HIRONO NS--------Max = 7.1(cm)
Without Damper
With Damper
-20
-10
0
10
20
0 30 60 90 120 150
Dis
plac
emen
t (c
m)
Time (sec)
Model B-2/HIRONO NS--------Max = 7.2(cm)
Without Damper
With Damper
(a) Model A-1 (b) Model A-2
(c) Model B-1 (d) Model B-2
(a) (b)
(c) (d)
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
464
Fig. 11 Relationship between maximum axialforce and height of tower: (a) Jmakobe NS; (b) Tsukidate NS; (c) Hirono NS.
0
5
10
15
20
25
30
35
40
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Hei
ght
(m)
Maximum axial force (kN)
JMAKOBE NS
Allowable axial force
Yield axial force
Without Damper
Model A-1
Model A-2
Model B-1
Model B-2
0
5
10
15
20
25
30
35
40
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Hei
ght
(m)
Maximum axial force (kN)
TSUKIDATE NS
Allowable axial force
Yield axial force
Without Damper
Model A-1
Model A-2
Model B-1
Model B-2
0
5
10
15
20
25
30
35
40
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Hei
ght
(m)
Maximum axial force (kN)
HIRONO NS
Allowable axial force
Yield axial force
Without Damper
Model A-1
Model A-2
Model B-1
Model B-2
(a) JMAKOBE NS
(b) TSUKIDATE NS
(c) HIRONO NS
(a)
(b)
(c)
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
465
Fig. 12 Hysteresis curve of viscous damper (relationship berweet velocity and damping force): (a) damping force 50 kN; (b) damping force 100 kN; (c) damping force 150 kN.
Fig. 13 Hysteresis curve of viscous damper (relationship between displacement and damping force): (a) damping force 50 kN; (b) damping force 100 kN;(c) damping force 150 kN.
Table 2 Maximum response displacement and reduction rate in each model.
Model Damping force (kN) Displacement (cm) Reduction rate (%)
Without damper - 46.1 -
Model A-1
50 21.5 53
100 15.9 65
150 17.1 63
Model A-2
50 40.6 12
100 39.7 14
150 41.4 10
Model B-1
50 32.6 29
100 29.0 37
150 26.6 42
Model B-2
50 26.5 43
100 19.0 59
150 19.1 59
-150
-100
-50
0
50
100
150
-30 -20 -10 0 10 20 30
Dam
ping
for
ce(k
N)
Velocity (kine)
-150
-100
-50
0
50
100
150
-30 -20 -10 0 10 20 30
Dam
ping
for
ce(k
N)
Velocity (kine)
-150
-100
-50
0
50
100
150
-30 -20 -10 0 10 20 30
Dam
ping
for
ce(k
N)
Velocity (kine)
(a) Damping force 50kN (b) Damping force 100kN (c) Damping force 150kN
-150
-100
-50
0
50
100
150
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2
Dam
ping
for
ce(k
N)
Displacement (cm)
-150
-100
-50
0
50
100
150
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2
Dam
ping
for
ce(k
N)
Displacement (cm)
-150
-100
-50
0
50
100
150
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2
Dam
ping
for
ce(k
N)
Displacement (cm)(a) Damping force 50kN (b) Damping force 100kN (c) Damping force 150kN
(a) (b) (c)
(b) (a) (c)
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
466
Fig. 14 Relationship between maximum axialforce and height of towe: (a) Model A-1; (b) Model A-2; (c) Model B-2.
the model of resistive force of 150 kN, but the
reduction rate shows less than or equal to the value of
model with 100 kN. Therefore, when the resistance
force of damper is designed, it is presumed that an
optimum value of the damping force exists around
100 kN.
Fig. 14 shows the relationship of maximum
compression axial force and height of tower for each
model. Although the response is reduced as the
resistance force of the damper increases in all models,
0
5
10
15
20
25
30
35
40
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Hei
ght
(m)
Maximum axial force (kN)
Model A-1
Allowable axial force
Yield axial force
Without Damper
F=50kN
F=100kN
F=150kN
0
5
10
15
20
25
30
35
40
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Hei
ght
(m)
Maximum axial force (kN)
Model A-2
Allowable axial force
Yield axial force
Without Damper
F=50kN
F=100kN
F=150kN
0
5
10
15
20
25
30
35
40
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Hei
ght
(m)
Maximum axial force (kN)
Model B-2
Allowable axial force
Yield axial force
Without Damper
F=50kN
F=100kN
F=150kN
(a) Model A-1
(b) Model A-2
(c) Model B-2
Study on Improvement of Seismic Performance of Transmission Tower Using Viscous Damper
467
it is conceivable that an optimum force exists around
100 kN. From the result, the maximum axial force in
the model without damper exceeds the allowable axial
force, it is confirmed that the damping effect is large
particularly in Model A-1 and Model B-2, and it is
relatively small in case of Model A-2.
Comprehensively, as the resistance force of viscous
damper increases, reduction effect of steel tower’s
response tends to be greater.
4. Conclusions
In this study, the tower that was generally adopted in
Japan has been the target structure. The tower used here
was the simplified single tower (220 kV) considering
the effects of transmission lines and viscous dampers.
In the previous paper, it was considered that the
models could accurately simulate the dynamic behavior
of the steel tower during the earthquake. The
differences of dynamic behavior were made clear by
dynamic response analysis using the past earthquake
waves. Especially, the reduction effect of steel tower’s
response with dampers was clarified. As the result, the
viscous dampers of velocity dependent type can reduce
the response of steel tower effectively and drastically.
The main results from this study are listed as follows:
(1) As the result of dynamic analysis using the
seismic waves at the Hyogo Earthquake and at the
Tohoku Earthquake, the response especially at the
tower top in the case of the Hyogo Earthquake was
extremely large;
(2) From the study of models with different setting
conditions of viscous damper, it became clear that it is
possible to reduce the response displacement at the top
by the dampers;
(3) As the result of evaluating the maximum axial
force of principal members, it was confirmed that the
model with low effect of response reduction also
definitely showed the reduction effect;
(4) There was an optimum resistance force of the
viscous damper for each target structure, and the great
reduction effect of tower’s response could be
obtained by optimally designing the performance of
dampers.
Acknowledgments
We thank the National Research Institute for Earth
Science and Disaster Resilience (NIED) for providing
us with the strong motion records of K-NET.
References
[1] The Institute of Electrical Engineers of Japan, Electrical Standards Committee. 1979. Design Standard on Structures of Transmission (JEC-127-1979), Denkishoin.
[2] Japan Society of Civil Engineers. 1999. The 1999 Ji-Ji Earthquake, Taiwan—Investigation into Damage to Civil Engineering Structures.
[3] Mazda, T., Otsuka, H., Uchida, H., and Ikeda, S. 2001. “A Study on Earthquake Responses of Steel Tower with Additional Damping.” ASME PVP 428-2: 43-8.
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