floor vibrations in practice and research classification

Floor vibrationsin Practice and Research

Classification of human induced floor vibrations

T i T ttiTomi Toratti

VTT

Fl Vib tiFloor VibrationsFloors are the interface between people and the buildings they useFloors are the interface between people and the buildings they use

Floors are the only type of structural sub-system that users of buildings cannot avoid having physical contact withbuildings cannot avoid having physical contact with

Requirements set on floors:Vibration performance, p ,Acoustic performance, Static stiffness, Safety for collapse, y pFire safety, Visual and economic performance.

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Springiness is associated with the sensation of

Useful distinctions:

Springiness is associated with the sensation of self-generated floor deflection and vibration froma single footstep during the time of contact betweena single footstep during the time of contact between the foot and floor surface.

Vibrational disturbances are caused by footfalls ona floor that are associated with motion induced by persons other than the observer.

Sven Ohlsson (1988)

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Floor types

1. Low frequency floorsnatural frequency < 8 Hz span normally over 10 mnatural frequency < 8 Hz, span normally over 10 mWeight over 300 kg/m2

2. High frequency floorsg q ynatural frequency > 8 Hz, weight less than 300 kg/m2

3. Floating floorsg- These may increase local deformations+ These may distribute point loads to several floor bbeams

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Floor natural frequency [Hz]

EI )(π 2 tm

EIl

f l)(2 20π

= 2 support, one way action

bl EIllEIf )(21)( 42

0 ⎥⎤

⎢⎡

⎟⎞

⎜⎛+⎟

⎞⎜⎛+⋅=

π 4 supports, two way action

lEIbbmlf

)(21

2 20⎥⎥⎦⎢

⎢⎣

⎟⎠

⎜⎝

+⎟⎠

⎜⎝

+

0 111f = Two supporting beam structures togehter

2,0

2,0

11Ll ff

+

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F [Hz]

V [m/s]

1 5

Slow walk 1,7 1,1

Normal alk 2 0 1 5

Walking force1.5

1 2

Normal walk 2,0 1,5

Slow run 2,5 3,3

0 9

1.2

3.0

Force [kN]

0 6

0.9

1.0

2.0

)0.3

0.6

-1.0

0.0

Acc

eler

atio

n (g

)

0.0

0.3

-3.0

-2.0

Free vibrationForcedib ti

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Time [s]3.00.0 0.5 1.0 1.5 2.0 2.5 3.0-4.0

0 50 100 150 200 250 300

Time (ms)

vibration

VTT

1000

1200

800

1000

[ ]765

)2sin(1)(3

1

NQ

tfnQtFn

n φπα

=

⎥⎦

⎤⎢⎣

⎡++= ∑

=

400

600

orce

[N]

[ ]

2,06.0,6,3

2,2.0,4,2

0,4.0,2,1765

Hzfn

Hzfn

HzfnNQ

n

n

n

πφα

πφα

φα

====

====

=====

0

200

Fo )10137(2

ISO

-200

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Time [s]-400

Time [s]

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Vibration on floors

• Low frequency, f < 9 Hzweight over 300 kg/m2

• High frequency floors, f>9 Hzweight below 300 kg/m2

Span usually over 10 m

• Resonance vibrations

Span usually below 10 m

• Shocks induced on floorsResonance vibrations

• Limitation on acceleration of ib ti

Shocks induced on floors

Li it ti th t ti d fl tivibrations • Limitation on the static deflection (velocity response of a unit impulse)

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According to Eurocode 5: f0 > 8 Hz

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Resonance vibrationDeformation (dynamic/static)

tFxKxCxM ωcos0=++ &&&

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Frequency ratio (Load frequency/ natural frequency of the floor)

VTTASL1(E=0.012) , 60 mm betoni

0.05

-0.11

-0.06

-0.010.0 0.5 1.0 1.5 2.0 2.5 3.0Time [s]

ent [

mm

]

0 mm305 mm610 mm915 mm

-0.31

-0.26

-0.21

-0.16

Dis

plac

eme 915 mm

1220 mm1525 mm

-0.36

ASL1 , 60 mm betoniAskelkuorma

1200

200

300

400

500

600

m/s

2]800

1000

1200

N]

-200

-100

0

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Acc

eler

atio

n [m

m

0 mm305 mm610 mm200

400

600

Voim

a [N

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-500

-400

-300

Time [s]

915 mm1220 mm1525 mm0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Aika [s]

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Laataston reunat vapaatp

200

250

50

100

150

Aika [s]

[mm

/s2]

-100

-50

00.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Kiih

tyvy

ys [

-250

-200

-150Askeltaajuus 120 per min

Askeltaajuus 100 per min

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100

Heel impact (walking)

aoW lki ib ti

10Walking vibration

Walking vibration(12% damping)

Continuous vibrationWalking vibration(3% damping)

Walking vibration(6% damping) ANNOYING

1Continuous vibration(10 t 30 l )

ao

(3% damping)

(10 to 30 cycles)(average peak accel.)

ACCEPTABLE

Frequency of Motion (Hz)

102 4 61 200.1

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Frequency of Motion (Hz)

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Table 1. The vibration classification of floors based on the intensity of the vibration.

Body perception Vibration of articles

A The vibrations are 1 The clinking of glassware and the leafA The vibrations are usually imperceptible.

1 The clinking of glassware and the leaf movements of a plant are usually imperceptible.

B The vibrations are barely 2 The clinking of glassware is usuallyB The vibrations are barely perceptible.

2 The clinking of glassware is usually imperceptible and the leaf movements are barely perceptible.

C The vibrations are 3 The clinking of glassware is barely perceptibleC The vibrations are perceptible. Base class

3 The clinking of glassware is barely perceptible. The leaf movements perceptible

D The vibrations are 4 The clinking of glassware the leaf movements areD The vibrations are clearly perceptible.

4 The clinking of glassware the leaf movements are clearly perceptible.

E The vibrations are strongly perceptible.

5 The clinking of glassware and the leaf movements of a plant are strongly perceptible

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strongly perceptible. movements of a plant are strongly perceptible

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Table 2. Proposal for vibration classes in office and residential buildings.Table 2. Proposal for vibration classes in office and residential buildings.

A1 Normal class for vibrations transferred from another apartment.pSpecial class for vibrations inside one apartment.

B2 Lower class for vibrations transferred from another apartment.Higher class for vibrations inside one apartment

C3, Normal class for vibrations inside one apartment.base class

D4 Lower class for vibrations inside one apartment. For example attics d h lidand holiday cottages.

E5 Class without restrictions.

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Table 3. Tentative acceptance limits for vibration classes.p f

Emphasised forEmphasised for high-frequency floors,

floating floors andAll floors tops (this part concerns floating floorEmphasised for

low-frequency floors

floating floors andraised floors

concerns floating floor and soft toppings and is

not well defined yet)

Vibration values GlobalDeflection

Local deflection

Class arms2)

[ / 2]vmax

2)

[ / ]vrms

2)

[ / ]|umax|2)

[ ]δ0 1)

[ /kN]δ1 1)

[ /kN][m/s2] [mm/s] [mm/s] [mm] [mm/kN] [mm/kN]

AB

≤0.03≤0.05

≤4≤6

≤0.3≤0.6

≤0.05≤0.1

≤0.12≤0.25

≤0.1≤0.2

CDE

≤0.075≤0.12>0.12

≤8≤10>10

≤1.0≤1.5>1.5

≤0.2≤0.4>0.4

≤0.5≤1.0>1.0

≤0.5≤1.0>1.0

1) Design criteria (load: 1 kN for u and w) to be used in design,2) Dynamic test criteria (load: walking person) to be used in testing

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Dynamic test criteria (load: walking person) to be used in testing

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2.00

acceptednot accepted

1.50

mm

]

1.00

n du

e to

1 k

N [m

δ + w < 1.0 mmBase class C3

0.50

Def

lect

ion

δ < 0.5 mm

0 000.000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Fundamental frequency [Hz]

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Vibration transfer to the neighboring apartment

Measurement Source of

|umax| vrms arms Rate of transfer to the neighboring

vibration

apartment

mm mm/s m/s2

Fl ) F ll tFloor a) Fully cutIn the same room Walking 0,025 0,32 0,037

Vibration to neighbor Walking 0,010 0,044 0,0047 13 %

In the same room Washing 0,0080 0,14 0,016

Vibration to neighbor Washing 0,0078 0,039 0,0040 25 %

Floor b) ContinousFloor b) ContinousIn the same room Walking 0,018 0,176 0,020

Vibration to neighbor Walking 0,0059 0,060 0,0053 26 %

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In the same room Washing 0,016 0,12 0,011

Vibration to neighbor Washing 0,011 0,065 0,0071 64 %

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Conclusions on floor vibration classification

• A classification of floor quality is proposed based on vibration properties

• Benefits: consumers know what they are buying and producers what they are selling

• Different quality levels are possible:• Different quality levels are possible: - high quality apartments, B - normal apartments, C - single houses, D- summer houses D or E

• The limit values may need adjustments as more experience• The limit values may need adjustments as more experience is gained.

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Conclusions on vibration performance of timberConclusions on vibration performance of timber floors

D i f f fl i l i• Dynamic performance of floors is a complex issue: a contribution of a) excitation, b) response, c) acceptability

• Design procedures are limited• Design procedures are limited• Avoidance of resonance is a prime issue

To increase the vibration performance increase stiffness in• To increase the vibration performance increase stiffness in 2-directions (increase acoustic insulation increase ’softness’)(increase acoustic insulation increase softness )

• Timber-concrete composite floors have performed well based on experimental experiencep p

• Vibration of floors is a common complaint of the occupant

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Vibration serviceability of timber floors is a complex and important issue but has largely been ignoredand important issue, but has largely been ignored.

Care must be exercised to define the dynamic system.

Modern construction materials and methods can exacerbate vibration problemsp

improved strength efficiency can mean lessened serviceability.

Problem floors cannot be avoided reliably using existing (simplistic) design ‘rules’e st g (s p st c) des g u es

is no international agreement as yet about how to handle the issue in design codes

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floor vibrations in practice and research classification

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