Cretu Tulei Ghindea

8/13/2019 Cretu Tulei Ghindea

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Outline

Effect of human activities on building

floors

Vibration limitation in code provisions

Case study

Conclusions


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Effect of human activities on

building floors

Long-span floors

Educational areas Commercial areas Factories

Light materials

strength damping


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building floors

Ordinary buildings:

moderate spans

stiff r. c. floors

f 10 - 14 Hz

Special buildings: long spans

light and flexible composite floors

f f of dynamic actions/human activities

No discomfort to the

building occupants


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building floors

Dance

Walk of people

Malfunction of

electro-mechanicalequipments

Aerobics Disturbing vibrations


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building floors

Jogging: ~ 2.5 Hz

Walk: 1.62.4 Hz

Running: ~3 Hz

Frequencies of equivalent harmonic excitation

1 cycle

(beat of music)

1 second

Group

weight

Fo

rce

Time

Dance


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building floors

10% g: people doing aerobics

0.5% g: sitting/lying persons

2% g: people standing in stores/

sitting near a dance floor

Unacceptable accelerations:

Acceptable accelerations:

Floor vibrations - Occupants comfort


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building floors

steady accelerations > 20% g

Fatigue phenomenon

Floor collapse

Resonance


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Vibration limitation in code

provisions

National Buildings Code of Canada: floor dynamic analysis for f1< 6 Hz

Eurocode 5, Design of timber structures: floors with timber beams in residential buildings

special investigations for f1< 8 Hz

WORKSHOP Eurocodes: Background and

Applications Eurocode 4. Serviceability limitstates of composite beamsHanswille, G., Brussels, 2008: floor dynamic analyses for f1< 7.5 Hz


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provisions


provisions

SSEDTA CD Release 2001: Structural

Steelwork Eurocodes: Development of a Trans-

National Approach, EC3, lecture 03, 2001:

f1> 3 Hz for floors with normal access

f1> 5 Hz for gymnastics and dancing halls

certain stiffness small deflections SLS


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provisions


provisions

Standard ISO10137,

Basis for the Design

of StructuresServiceability of

Buildings against

Vibrations, ISO,Geneva, 1992

0.04

0.2

1

5

25

1 2 4 8 16 32

PeakAcceleration[%Gra

vity]

Frequency [Hz]

ISO Baseline Curvefor RMS acceleration

Offices, Residences

Indoor Footbridges, Shooping

Malls, Dining and Dancing

Rythmic Activities,Outdoor Footbridges


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provisions


provisions

ALLEN, D.E., PERNICA, G., Control of

Floor Vibration, Construction Technology

Update No. 22, National Research Councilof Canada, 1998:

residential and office buildings

floor PGA < 0.5% g


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Case study

r.c. slabthmed= 12 cm

C24/30: Ec= 325 N/mm2

steel beamsHEA450S235

2 m

2 m

14 m

14 mr.c. walls

perimeter beams


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Case study

Analyses results:

natural frequencies;

maximum deflections.

Models of the composite floor:

M1: equalized with a grid of steel beams;

M2: fixed on the boundary;

M3: elastically supported by the perimeter beams

and r.c. walls.


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Case study

M2 M3

fixedfixed


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Case study

M1, M2, M3

Concrete stiffness: non-degraded degraded

Loads: dead load p1= 6.8 kN/m

2

live load p2= 3 kN/m2(rooms)

p2= 4 kN/m2 (corridors)

CE CE==CE CE==*

CE

CE= 0.5

*

CE

CE= 0.5


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Case study

M1, M2, M3

Load combinations (EC1):

SLS:

LC1: q1= p1

LC2: q2= p1+ 0.4 p2 LC3: q3= p1+ p2

ULS:

LC4: q4= 1.35 p1+ 1.5 p2

lk,1,1

n

1j

jk,QG


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Case study

Floor modal shapes M1

dead + live load (q3) /

f1= 10.19 Hz f2= 19.44 Hz

CE CE==CE CE==


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Case study



f1= 10.82 Hz f2= 20.1 Hz

CE CE==CE CE==


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Case study



f1= 7.69 Hz f2= 14.84 Hz

CE CE==CE CE==


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Case study

Maximum deflections of the floor, dmax[mm]

LC q1 q2 q3 q4

Model M1

= 0 6.30 7.40 9.00 12.50

2.60 3.10 3.80 5.20

3.00 3.60 4.30 6.10

Model M22.40 2.79 3.50 4.80

2.50 2.90 3.60 5.00

Model M3

4.32 5.13 6.28 8.80

5.52 6.50 7.95 11.15

CE

CE

*

CE

CE

*

CE

CE

*

CE


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Case study

First natural frequency of the floor, f1[Hz]

q1

q1q1

q1

q1

q1

q1

q2

q2q2

q2

q2q2

q2

q3

q3q3

q3

q3

q3

q3

q4

q4q4

q4

q4

q4

q4

0

2

4

6

8

10

12

14

M1 M1 M2 M3 M1 M2 M3

Frequency[Hz]

Modeltype

Minimumacceptable

frequency [3]

7.5

*

CE0EC CE

Minimumacceptable

frequency [6]

NBCWS-EC4


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Case study

Approximate formula for the first frequency of acomposite floor:

f1limiting >> deformability conditiongenerally applied in floor designing,

M3 ( )

max1d20f

350ldd amax

mm8dmax mm4035014000da

*

CE CE= 0.5*

CE CE= 0.5


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Conclusions

Check of dynamic characteristics is mandatory.

f1 beam depth storey clear height


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Conclusions

Physico-mechanical characteristics of the

materials, especially of the concrete, are different

of those considered in analyses.

Experimental measurements in situ are

absolutely necessary.


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Thank you for your attention!

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Cretu Tulei Ghindea