Results of experimental research of vibration
acceleration levels on the ground surface of construction site became initial
data in the current study. It was found that train traffic creates three
degrees of motion: horizontal X and Y, and vertical Z – in octave bands with
centre frequency 31,5 (70…92 dB) and 63 Hz (73…96 dB). Vibration level in
octave bands with centre frequency 2, 4, 8, 16 Hz does not exceed background
effects. Therefore, summed vibrations are high-frequency. Vibration
acceleration levels caused by trains’ traffic in the building area exceed
permitted value for domestic premises by 6…15 dB. It is known that in case of vibration
distribution from a ground surface to a building part level may vary: in
footing parts it decreases, in concrete floor slabs and walls it increases. As
a result vibration and noise levels may grow.
Vibration control in the source of vibration, in the
underground tunnels, is the most effective way of vibration isolation in
buildings. Alternative way of vibration isolation (its decrease in the vibration
channel) involves using an elastic layer of vibro-proofing material under a
base slab, and also between an underground part of building and the surface.
Analysis of vibration acceleration levels expected in
slabs where residential and non-residential premises are located was performed
for two kinds of vibration isolation materials:
- polyurethane vibration control pads Sylomer AG5004 by Getzner (Austria);
- elastomeric vibro-proof materials Nowelle® mod. 1.10 for general purposes (Russia)
For this analysis researches used a CAE system called
LIRA SAPR: the building model was completed with plate finite elements that had
all properties of vibration isolating materials and with additional loading
that could have been caused by vibration when spectrums of dynamic loadings
were applied to plate finite elements of elastic restraints and were transferred
to element nodes of plate finite elemets.
The researches took into account a non-steadiness of vibration
distribution in building parts in order to ensure the highest credibility of
the predicted results, and to that effect, they digitally processed test
measurements’ dynamics and plotted the vibration-time accelograms during train
traffic in tunnels going in both directions.
Train traffic interval t=20 s was chosen as an estimated integration time interval.
Train traffic interval t=20 s was chosen as an estimated integration time interval.
Transition from levels of vibration acceleration to mean square value of
vibration acceleration was done according to:
a – QM of amplitude vibration acceleration, m/s2
1∙10-6 – reference value, m/s2
According to GOST (technical standards) time interval of averaging vibration
acceleration amplitudes is not less than 1 s; estimated time step ∆t sets to
the semiperiod of maximum analyzed frequency:
In case of sinusoidal vibrations with the constant amplitudes, amplitude
QM equals to the amplitude. Vibrations are caused by train traffic that
transfers through the soil. They are nonsinusoidal polyharmonic vibrations with
combined spectrum and amplitudes that are less than a second; there is no
simple relation between vibration properties. When you transfer amplitudes’ QM of vibration
acceleration to instantaneous amplitudes, it is customary:
,
K is the peak-factor that is accepted into the calculation of √2 = 1.41.
Spacial FE model results show value changes in time of vibration
acceleration with time step ∆t=0,01 under frequency loading at 2, 4 , 8, 16, 31,5
63 Hz that is within the rated frequency range. Reference points that are
located in the model sites the slabs were selected as the most adverse to occurrence
of vertical vibrations.
Storey
|
Direction
|
Sylomer
|
Nowelle
|
Vibration
levels difference of Sylomer and Nowelle
|
Slab
|
X
|
91
|
92
|
-1
|
Y
|
94
|
94
|
0
|
|
Z
|
90
|
90
|
0
|
|
12
|
X
|
87
|
89
|
-2
|
Engineering storey
|
Y
|
94
|
93
|
1
|
Z
|
91
|
89
|
2
|
|
11
|
X
|
89
|
90
|
-1
|
Y
|
92
|
93
|
-1
|
|
Z
|
90
|
90
|
0
|
|
10
|
X
|
89
|
89
|
0
|
Y
|
90
|
93
|
-3
|
|
Z
|
89
|
89
|
0
|
|
9
|
X
|
89
|
88
|
1
|
Y
|
96
|
96
|
0
|
|
Z
|
89
|
92
|
-3
|
|
8
|
X
|
90
|
88
|
2
|
Y
|
94
|
97
|
-3
|
|
Z
|
91
|
91
|
0
|
|
7
|
X
|
94
|
90
|
4
|
Y
|
97
|
99
|
-2
|
|
Z
|
93
|
91
|
2
|
|
6
|
X
|
88
|
89
|
-1
|
Y
|
99
|
97
|
2
|
|
Z
|
91
|
92
|
-1
|
|
5
|
X
|
94
|
94
|
0
|
Y
|
90
|
90
|
0
|
|
Z
|
87
|
89
|
-2
|
|
4
|
X
|
94
|
93
|
1
|
Y
|
91
|
89
|
2
|
|
Z
|
89
|
90
|
-1
|
|
3
|
X
|
92
|
93
|
-1
|
Y
|
90
|
90
|
0
|
|
Z
|
90
|
89
|
1
|
|
2
|
X
|
90
|
94
|
-4
|
Y
|
89
|
89
|
0
|
|
Z
|
89
|
88
|
1
|
|
1
|
X
|
95
|
95
|
0
|
Y
|
89
|
92
|
-3
|
|
Z
|
90
|
88
|
2
|
Absolute instant peaks are within limit:
- polyurethane vibration control pads Sylomer AG5004 by Getzner;
- elastomeric vibro-proof materials Nowelle® mod. 1.10.
After comparing the estimated vibration levels, elastomeric vibro-proof
materials Nowelle® mod. 1.10 for general purposes prove to
be as good as polyurethane
vibration control pads Sylomer AG5004 by Getzner for isolation
purposes.
Using
of vibration isolation of elastomeric vibro-proof material Nowelle®
mod. 1.10 for general purposes will give an opportunity for cost
reduction in 2,1 times (according to the price of March, 2015). 
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