26 авг. 2016 г.

Study of vibration isolation used in residential building affected by vibration from underground

The comparative study was conducted in order to examine the vibration impact on a 11-storied residential building with non-residential premises in the ground level and an underground parking located above the underground tunnels, and to compare isolation efficiency of elastomeric vibro-proof materials Nowelle mod.1.10 for general purposes (Russia) with polyurethane vibration control pads Sylomer AG5004 by Getzner (Austria). Gross building area – 1453,3 m2. Depth of tunnel in the construction site – 30 m.
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:
  1. polyurethane vibration control pads Sylomer AG5004 by Getzner (Austria);
  2. 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.






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:

f frequency 63 Hz.
So Δt = 1/(2*63)= 1/126  0,0079  0,01 с.
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.
Peaks of estimated vibration levels on the slabs, dB
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).