Active-mass-damper control of traffic vibration of a four-story
steel-framed building
Masayasu Miwa1, Shinji Nakata1, Shin-ichi Kiriyama1,
Yukio Tamura2, and Akihito Yoshida2
1
Housing Division
Asahikasei Homes Corporation. Japan
2
Dept. of Architectural Engineering
Tokyo Polytechnic University. Japan
1. Abstract
Demand for middle-rise buildings in urban areas have been
growing in recent years, and three or four-story houses built on
soft ground near vibration sources such as railways and
expressways have increased. Conducting traffic vibration well,
soft ground often causes building vibration. This study focuses on
a four-story steel-framed building constructed on soft ground near
an expressway, a site where a vibration problem is likely to be
encountered. In this study, the vibration characteristics of the
building were investigated at each stage of construction. This
paper reports on the case involving an active mass damper
(AMD) system installed on the roof of the building.
40
m
Building site
2. The building and measurement
Highway
Expressway
Figure 1 shows the location of the building. Figure 2 shows the
plan of each floor, the locations of the acceleration pickups, and
the location of the AMD system. The building is located about 40
m from a Metropolitan Expressway. The bearing capacity of the
ground at the site is such that N-values are mostly not greater
Table-1
Measurement day
Fig-1 Location map
Maximum vibration level
Measurement
stage
1998/4/24 Before construction
1998/11/26 Foundation complete
Main frame complete
1999/1/20
(without interior wall )
1999/3/23 Completion of construction
1999/3/24 Nighttime measurement
2000/3/30 After one year of occupancy
Nighttime measurement
(with AMD)
Expressway
traffic condition
X
Ground
Y
Z
X
1st floor
Y
Z
Smoothly flowing
0.25 0.16 0.56 Somewhat congested 0.13 0.14 0.50 0.20 0.13 0.20
Smoothly flowing
Highly congested
-
-
-
0.13 0.14 0.50 0.22 0.18 0.32 2.24 2.51
0.56
0.10 0.11 0.32 0.10 0.13 0.18 1.41 1.00 0.25
- 0.22 0.20 - 3.55 1.78 -
1
(cm/sec2)
4th floor
X
Y
Z
-
-
0.3
0.3
-
0.9
0.7
-
than 3, and the bearing layer underlying a thick layer of soft soil is at a depth of 35 m from the ground surface.
From the planning stage, therefore, there was concern about the possibility of vibration induced by expressway
traffic. The building is a four-story rigid steel frame structure with steel deck and concrete floors and autoclaved
lightweight concrete (ALC) exterior walls. The weight of the building is about 130 tons, the eaves height is 12.5 m,
and the total floor area is 340 m2. Because the ground is weak and the building was to be constructed near the
expressway, there has been concern, from the initial stages of design, about possible adverse effects of traffic
vibration. It was decided, therefore, to go with a mat foundation supported by cast-in-place bearing piles. The first
and second floors of the building are used as offices, and the third and fourth floors are used as dwelling. On the
roof floor, a 100-kilogram AMD was installed in each of two horizontal directions (X, Y). Vibration acceleration was
measured with vibration level meters before construction, upon completion of the foundation, upon completion of
the main structural frame, upon completion of the building, and after one year of occupancy. The measurement
conducted upon completion of the
(Hz)
Natural frequency at each stage
building included nighttime vibration Table-2
MeasureMeasurement
Ground
4th floor
measurement.
The
"before
X
Y
X
Y
ment day
stage
construction" measurements were
taken at a point on the roadside
1998/4/24 Before construction
3.07 3.07
asphalt surface. The measurement
1998/11/26 Foundation complete
3.03 3.04
upon completion of the main
1999/1/20 Main frame complete
3.09 2.99 2.59 3.17
structural frame was conducted by
(without interior wall )
the roadside in front of the building,
and the measurement points were
1999/3/23 Completion of construction
4.26 3.02 2.89 3.71
located on each floor of the building.
2000/3/30 After one year of occupancy 3.01 3.39 2.83 3.66
Controller
Ball screw
AC-Servomotor
Active
mass
AMD
Acceleration
sensor
Controller
Driver
Y Unit
Roof
Acceleration
sensor
Acceleration
pick-up
X Unit
Fig-3 Active vibration control system for low-rise building
Reaction:MaXa
4st floor
Displacement
of building:Xs
3rd floor
Acceleration pick-up
on the ground
u
Actuator
Active mass:
Ma
Mass of a building：Ms
Driver
Controller
Acceleration
sensor
Damping
2nd floor
Cs
Spring
constant:
Ks
50
91
1st floor
Mass displacement:Xa
793
0
Ground
Fig-2 Outline of the building
Fig – 4 Outline of AMD
2
Traffic
vibration
3. Active vibration control system
Since the building to be controlled is a house, it was decided to use an AMD system. And that needs to be
lightweight, compact and inexpensive. Figure 3 shows the basic configuration of an AMD. The AMD units,
controller and acceleration sensor were installed on the roof of the building. An AMD is a mechanism for controlling
an added mass by using a ball screw and servomotor system. The mass of an AMD is 100 kg in each direction,
and the AMD system installed on the building consists of two AMD units (for the vibration control in the X and Y
directions), one placed on top of the other. Designed to control the fundamental natural mode of vibration, the AMD
system uses the so-called "skyhook control" algorithm, which needs to control vibration by detecting the velocity of
the roof. Figure 4 illustrates the concept of vibration control performed by the AMD. Skyhook control requires
velocity detection. Since, the AMD system described in this paper uses acceleration sensors, acceleration signals
need to be integrated so that they can be used. In a case like this, it is usually necessary to use low-pass filters to
remove noise components, integrators, and high-pass filters to eliminate origin displacement due to integration
errors. For the purpose of cost reduction, however, the frequency range to be controlled was limited to 1 Hz to 10
Hz, and only band-pass filters to cause a 90-degree phase delay in this frequency range were used, and other
means of integration such as integrators were not used.
4. Measurement results
0.014
0.012
0.01
0.008
0.006
0.004
0.002
0
Acc. cm/sec 2
Hw y traffic condition
Smooth
1998/5/28
Somew hat congested
1998/11/26
Highly congested
1999/3/23
0
10
15
Frequency （ Hz)
20
0.012
Ground
Foundation
0.01
0.008
0.006
0.004
0
5
10
Frequency （ Hz)
15
20
0.002
0
0
(a) X direction
0.016
Hw y traffic condition
Smooth
1998/5/28
Somew hat congested
1998/11/26
Highly congested
1999/3/23
0.012
0.01
0.008
5
10
15
Frequency （ Hz)
20
(b) Y direction
0.03
Ground
Foundation
0.025
Acc. cm/sec 2
0.014
Acc.　cm/sec 2
5
(a) X direction
Acc. cm/sec 2
0.018
0.016
0.014
0.012
0.01
0.008
0.006
0.004
0.002
0
Ground
Foundation
Acc. cm/sec 2
Table 1 and Table 2 show measured values of
maximum acceleration and natural frequency,
respectively, at different stages of construction, along
with the state of expressway traffic at each stage.
Figure 5 shows acceleration Fourier spectra of the
ground. Measurements before construction and after
0.02
0.015
0.006
0.004
0.01
0.005
0.002
0
0
0
5
10
Frequency　（Hz)
15
20
0
5
10
15
Frequency （ Hz)
20
(c) Z direction
(b) Y direction
Fig-6 Fourier spectra of ground and foundation
Fig-5 Fourier spectra of ground
3
Amplification
Amplification
Amplification
Amplification
Amplification
Amplification
Amplification
Amplification
completion of the foundation were conducted at the same time in the two horizontal directions (X, Y) and the
vertical direction (Z). After completion of the main frame ,building vibration in the X and Y directions was measured
separately. Vibration characteristics of the ground vary considerably depending on the state of traffic on the
expressway. During traffic congestion, vibration is small because vehicles move slowly. While the road is not
congested, vibration is strong because vehicle speed is high. Considerable differences occur at around 3 Hz to 4
Hz, which are dominant frequencies of vibration of the ground. Figure 6 shows acceleration Fourier spectra of the
ground and the foundation measured upon completion of the foundation. As can be seen from comparison of the
acceleration Fourier spectra in the horizontal directions shown in Figure 6(a) and (b), vibrations of the ground and
the foundation in the horizontal directions do not show significant differences. As Figure 6(c) shows, however,
vibration of the foundation in the
25
25
vertical
(Z)
direction
is
Y direction
X direction
significantly smaller than that of
20
20
the ground.
15
15
Figure
7
shows
the
10
10
ground-to-fourth-floor transfer
function. The state of the
5
5
building after completion of the
0
0
main frame shown in Figure
0
2
4
6
8
10
0
2
4
6
8
10
7(a) was such that the floors
Frequency　（Hz)
Frequency　（Hz)
and ALC exterior walls had just
(a) Main frame complete (without inner wall)
been completed, but the interior
25
25
walls had not yet been
X direction
Y direction
constructed. In this condition,
20
20
the natural frequencies of the
15
15
building were 2.59 Hz in the X
direction and 3.17 Hz in the Y
10
10
direction. Since the exterior
5
5
walls on the first floor are
0
0
unevenly distributed, torsional
0
2
4
6
8
10
0
2
4
6
8
10
peaks appear at 3.8 Hz. As
Frequency　（Hz)
Frequency　（Hz)
shown in Table 1, measured
(b) Completion of construction (without live load)
accelerations
of
building
vibration after completion of the
25
25
Y direction
X direction
main structural frame at the
20
20
fourth floor were 2.24 cm/sec2
15
15
in the X direction, 2.51 cm/sec2
in the Y direction and 0.56
10
10
cm/sec2 in the vertical direction.
5
5
Thus, vibrations in the horizon
directions were strong. At the
0
0
time of the measurement
0
2
4
6
8
10
0
2
4
6
8
10
Frequency　（Hz)
Frequency　（Hz)
conducted upon completion of
(c) One year progress (without AMD)
the building, there was no live
load, such as furniture, acting
25
25
on the building. In this condition,
X direction
Y direction
20
20
as shown in Figure 7(b), the
natural frequencies of the
15
15
building were 2.89 Hz in the X
10
10
direction and 3.71 Hz in the Y
5
5
direction. Thus, the natural
frequencies in the horizontal
0
0
directions were 0.3 Hz and 0.5
0
2
4
6
8
10
0
2
4
6
8
10
Frequency　（Hz)
Frequency　（Hz)
Hz higher than those observed
upon completion of the main
(d) AMD control
structural frame. This is thought
to be due to the stiffness of the
Fig-7 Ground-to-fourth-floor transfer function
interior walls of the building. As
4
shown in Table 1, accelerations of building vibration measured upon completion of the building were 1.41 cm/sec2
in the X direction and 1.00 cm/sec2 in the Y direction. As the measurement upon completion of the building was
conducted during the evening rush hours, the accelerations of vibration of the ground and the building were low
because of traffic congestion on the expressway. The acceleration of building vibration, therefore, was measured at
nighttime, too. As shown in Figure 8, during this nighttime measurement, the maximum vibration acceleration of
3.55cm/sec2 was observed at three in the midnight. Vibration acceleration was low during evening hours and after
seven o'clock in the morning. Between three and six o'clock in the morning, vibration acceleration was high,
frequently exceeding 2.00 cm/sec2.This is thought to be due to the traffic conditions on the expressway: during the
high-traffic hours in the morning and evening, heavy traffic causes congestion on the expressway, and during the
low-traffic hours in the early morning, fully loaded trucks travel fast on the expressway.
As shown in Figure 7(c), the natural frequency of the building after one year of occupancy of the building was
2.84 Hz in the X direction and 3.66 Hz in the Y direction. Figure 9 shows changes in the natural frequency of the
building after the main structural frame was completed. Upon completion of the interior walls after the main frame
was completed, the natural frequency of vibration of the building increased by 0.3 Hz to 0.5 Hz. Later, under the
influence of live loads, the natural frequency decreased but only by about 0.1 Hz. As a next step, the AMD system
was installed as a means of the vibration response control, and the vibration control effect of the system was
evaluated. As shown in Figure 7(d), response peaks at around 3 Hz were reduced by the AMD system to less than
one-third, indicating that the AMD system is very effectiveness. Figure 8 shows the results of the nighttime
measurement of vibration acceleration. As shown, although the vibration input levels on the first floor are
essentially the same in the AMD-on case and the AMD-off case, the vibration accelerations on the fourth floor of
building vibration in the AMD-on case were smaller than 1.00 cm/sec2. Thus, vibration acceleration of building was
reduced to levels that are acceptable to human occupants.
5. Conclusion
Vibration surveys of a four-story steel-framed building located near an expressway were conducted from the
construction stage to one year after the building began to be occupied. The findings of the surveys are as follows:
(1) Ground vibration measurement revealed that the dominant frequency of vibration of the ground is 3 Hz to 4 Hz,
and that the amplitudes of the components of ground vibration varied considerably depending on traffic
conditions on the expressway.
(2) Cast-in-place bearing piles were used as a foundation-related means of reducing adverse effects of soft
ground. Vertical vibration was reduced by laying a foundation.
Peak values measured every 15 minutes of acceleration (X direction)
4
3
2
Acc. (cm/sec )
3.5
AMD off
2.5
2
1.5
1
AMD on
0.5
0
20:00
22:00
0:00
2:00
4:00
6:00
8:00
Time
Fig-8 Comparison of acceleration of vibration
5
AMD on
4th floor
1st floor
AMD off
4th floor
1st floor
Measurement
1999.3.23
2000.3.30
Natural frequency （Hz）
4
3.5
3
2.5
X direction
Y direction
2
Steel frame
construction
complete
After one year of
occupancy
fig-9 Changes in natural frequency over time
(3) Environment vibration measurements conducted before and after the construction of the interior walls revealed
that the natural frequency of vibration of the building rose by 0.3 to 0.5 Hz as a result of the interior wall
construction. The amount of change in the natural frequency of vibration due to live loads was as small as
about 0.1 Hz.
(4) Since the dominant frequency of vibration of the ground and that of the building was close, considerable
vibrations of the building were observed depending on the traffic conditions on the expressway in cases where
the vibration control system was not active.
(5) During nighttime measurement, strong vibrations due to speeding trucks were observed at around dawn.
(6) The AMD system installed on the roof of the building proved effective, reducing response peaks near the
natural frequency of vibration of the building to less than one-third.
6