Wood-Frame Floor Vibration and Sound Research at FPInnovations -

Forintek Division (FPI), Canada

Lin J. Hu, Research Scientist

FPInnovations – Forintek Division, Canada

To endure occupants comfort, Canada has invested great efforts on research and

development in search for solutions to control excessive vibrations induced by human

normal activities in wood-frame floors and sound transmission in wood-frame buildings.

This presentation describes the research efforts covering the entire spectrum of

mechanical wave motion in wood-frame buildings from low to high frequency such as

floor vibration, airborne and impact sound transmission, and low frequency footstep

impact sound transmission in wood-frame floors.

This presentation first provides an overview of the complete story on the development of

a vibration controlled design method for wood-joisted floors through a cross-Canada field

survey to assess occupants comfort and field tests to record floor dynamic performance

signatures. A brief summary of the development of predictive tools for the signatures and

the design criterion, i.e. correlation between occupants comfort and the predicted

signatures of wood-frame floors is also given. The methods to assess human comfort in

field and in laboratory, the test methods to determine floor static deflections, frequencies,

damping ratios and dynamic responses to an impulse and walking, and a FEM software

and simple equations to predict the static deflection and frequency are also described.

A brief summary of the more than 10-year testing program at National Research Council

of Canada (NRC) to rate the fire resistance and sound transmission class (STC RW) of

floors and walls, and impact insulation class of floors (IIC=110-Ln,w) is given. This

resulted in the implementation of the rating results of hundreds of floors and walls in

2005 National Building Code of Canada. The software to predict the STC of joisted

floors and studded walls, and the IIC of joisted floors developed by NRC based on the

empirical equations derived from test data is also demonstrated. Four types of wood

toppings developed at FPInnovations – Forintek Division are illustrated to show the

potential of using wood topping to replace conventional concrete topping to optimize

wood-frame floor vibration and acoustic performance.

Finally, unresolved issues associated with low frequency footstep noise in wood-frame

floors are discussed, and a new research project of FPInnovations to address this issue is

introduced. A new project to address acoustic and vibration issues of cross-laminated-

timber floors is presented. A brief introduction of a new project to address the vibrations

in wood-frame tall building is given. The presentation is concluded with the remarks that

stress the need to achieve optimum design and construction solutions that take into

account all performance attributes and avoid some of the conflicting performance issues.

www.fpinnovations.ca

One vision.Global competitiveness.p

NEW VALUE FOR A

CHANGING MARKETPLACE

www.fpinnovations.ca

Wood-Frame Floor Vibraitonand Sound Research at FPInnovations-ForintekDivision, Canada

Lin HuResearch Scientist – Building Systems

Quebec Lab.

Wood-Frame Floor Vibration and Sound

Human Activities

Vibrate Air Vibrate Floors

> 50Hz< 25 Hz

>25 Hz

Occupants feel(movement or

vibration)

Occupants hear(Airborne sound)

Occupants hear (impact sound)

Overview of Wood-Frame Floor Vibration and Sound Research at FPInnovations – Forintek Division

Conventional

north America

wood-frame

floor construction

Floor Vibration (<25Hz)

(after S. Ohlsson, 1984,

"Springness and human

induced floor vibration –

A design guide")

Wood-Frame Floor Vibration Research at FPI:- Objectives

• To control vibrations induced by human

normal activities in wood-frame floors

• To ensure occupants comfort

Through Development of

1.vibration controlled design method

2 construction solutions2.construction solutions

Field FloorPerformance Testing

Consumer Survey

Development of Vibration Controlled Design Method:- Approaches

FEM Modelling,

Simple Equation

Laboratory Testing

Floor PerformanceFloor PerformanceIndicators:Indicators:

D, F, A, V, dampingD, F, A, V, damping

Occupants'Occupants'ComfortComfort

Correlation between occupant comfort and

Correlation between occupant comfort and

Predict Predict PerformancePerformance

IndicatorsIndicators

Verify Verify PredictivePredictive

ToolsTools

Predicted PerformanceIndicators

Predicted PerformanceIndicators

measured performance indicators

measured performance indicators

IndicatorsIndicators

Vibration Controlled Design

Method: Design criterion and predictive tools

Development of Vibration Controlled Design Method:- Occupants’ Comfort Assessment

Field Survey Highlights (Across-Canada)

• 1 H. survey with 80 questions

• Typical consumer survey questions:

– When did you first notice any effect related to floor motion?

– Do you know if the floor moves because of some thing you hear,

you feel, or you see, or some combination of these effects?

– What acceptable rating would you assign to this floor

performance?

Development of Vibration Controlled Design Method:- Occupant's Comfort Assessment

Laboratory Subjective Evaluation Highlights• Evaluator first walked on the

floor, then sat while other walkedfloor, then sat while other walked

on the floor, finally answered

questions.

• Typical subjective evaluation

questions:

– Could you feel the floor move or bounce while you were walking?

– Could you feel the floor move or bounce while other was walking?bounce while other was walking?

– Were you annoyed by the movement?

– What acceptable rating would you assign to this floor performance?

Performance Tests:- 1kN Static Deflection Test

Field Laboratory

1 kN Static Loading

Deflection measurement

Performance Tests:- Modal Test to Determine F and Damping

Field Lab.

Performance Tests:- Ball Drop Test to Determine A, V, Dis.

Ball drop impulse

Floor acc. response

Performance Tests:- Response to Normal Walking

Measured loadMeasured load--

time histories time histories

of two footsteps of two footsteps

from one person from one person

walking walking

1

1.5

Floor acc. response to walking

(Ebrahimpour(Ebrahimpour

et al in 1994)et al in 1994)

The Fourier

Transform

spectrum of the

-1.5

-1

-0.5

0

0.5

0 0.5 1 1.5 2 2.5 3

Time (Second)

Ac

ce

lera

tio

n (

g) Load-time

history of a person

walking

( Rainer and Pernica

in 1986)

Performance Indicators Well-Correlated to Human ComfortPerformance Indicators Well-Correlated to Human Comfort

Point Load Deflection

Fundamental Natural Frequency

Peak Acceleration

Initial Velocity

Point Load Deflection + Mass

+

Root-Mean-Square Acceleration

Peak Acceleration

(7 Hz < Frequency < 30 Hz)

2.50

3.00

F/d^0.39 >15.3 Correlation

Unacceptable Floor

Example: Correlation between Occupants’ Comfort and the Combination of Measured Frequency and DeflectionExample: Correlation between Occupants’ Comfort and the Combination of Measured Frequency and Deflection

1.00

1.50

2.00

Mea

sure

d 1

KN

sta

tic

Defl

ect

ion

(m

m)

Unacceptable Floor

Acceptable Floor

.00

.50

5.0 10.0 15.0 20.0 25.0 30.0

Measured Fundamental Natural Frequency (HZ)

Development of Vibration Controlled Design Method:- Predictive ToolsDevelopment of Vibration Controlled Design Method:- Predictive Tools

FEM software to predict fundamental natural

Frequency and 1kN-point load deflection

Measured deflection Measured deflection = 1.04 mm, Predicted deflection = 1.00 mm

Measured frequency Measured frequency = 18.8 Hz, Predicted frequency = 19.5 Hz

Development of Vibration Controlled Design Method:- Predictive Tools

FEM software to predict fundamental natural

Frequency and 1kN-point load deflection

Measured deflection Measured deflection = 1.19 mm, Predicted deflection = 1.61 mm

Measured frequency Measured frequency = 17.3 Hz, Predicted frequency = 19.4 Hz

Development of Vibration Controlled Design Method:- Predictive Tools

Simple equations to predicted fundamental natural

Frequency and 1kN-point load deflection (Dr. Chui, UNB)

= =

++

=

..5,3,1 ..5,3,142441

4

14

m n

yxyx

kN

Db

nD

ab

mnD

a

mab

Pd

πin m

424111π

1

114

1

2++=

bD

abD

aDf yxyx

ρ

π in Hz

1f 2721f

Vibration Controlled Design Method:- Design CriterionVibration Controlled Design Method:- Design Criterion

Where:

d1kN = computed 1 kN static deflection of a bare floor

7.18)( 44.0

1

1>

kNd

for

27.211 )

7.18(

fd kN <

f1 = computed fundamental natural frequency of a bare floor

3

3.5

on

(m

m) Design criterion of f/d^0.44>18.7

Acceptable floors by occupants

Unacceptable floors by occupants

Verify the Design Method using 106 Field Wood-Frame FloorsVerify the Design Method using 106 Field Wood-Frame Floors

0 5

1

1.5

2

2.5

ate

d 1

kN

Sta

tic

Def

lect

io

0

0.5

0 10 20 30 40

Calculated Fundamental Natrual Frequency (Hz)

Ca

lcu

la

Floor Sound Insulation ( > 50 Hz)

Impact sound

Source: Presentation “Airborne Sound Transmission” of National Research

Council of Canada (NRC) “Building Science Insight” seminar series in 2002

Sound Insulation in Wood-Frame Buildings( > 50 Hz)

• Minimum Canadian code requirement:

STC = 55 (Rw STC), IIC = 50 (Ln,w 110-IIC)

• Institute for Research in Construction (IRC) of• Institute for Research in Construction (IRC) of

National Research Council of Canada (NRC) tested

hundreds floors (>700) and walls for their STC and IIC

• Results were implemented in 2005 National Building

Code of Canada (NBCC)

• IRC’s study of flanking transmission in multi-family

dwellingsdwellings

• FPI’s role – develop construction solutions for sound

insulation of wood-frame buildings

Sound Transmission Tests in Acoustic Chamber at IRC of the NRCSound Transmission Tests in Acoustic Chamber at IRC of the NRC

IRC Predictive Tools to Estimate STC and IIC of Floors and WallsIRC Predictive Tools to Estimate STC and IIC of Floors and Walls

http://www.alfwarnock.info/sound/socindex.html

FPI Development of Solutions for Sound Insulation

Acoustic Performance of Conventional North America Wood-Frame Floors

STC = 55

IIC = 49

• Min. 38x235 mm lumber joists or 241 mm deep wood I-joists spaced at max.

600 mm o c600 mm o.c.

• 15.5 mm thick plywood or OSB sub-floor

• Cavity filled with sound absorptive materials

• Two layers of 15.9 mm gypsum boards supported on

• Resilient metal channels at 600 mm o.c.

- National Building Code of Canada 2005

FPI Development of Wood Topping 1: 50 mm Cross-Laminated Wood Panel (CLT)

FPI Development of Wood Topping 2: 38 mm Three-Layer Raft

• Top – 12.5 mm Plywood

• Core – 12.5 mm Gypsum boardCore 12.5 mm Gypsum board

• Bottom – 12.5 mm Particleboard

• Between layer – 2 mm polyester foam

• Bonding – 41 mm screws at 150 mm o.c. along

the edge and 305 mm o.c. in the field

FPI Development of Wood Toppings 3 and 4

: 15 5 mm OSB boards: 15.5 mm OSB boards

: 38 x 38 mm lumber sleepers on joists

: 2 mm-thick insulation layers

: 33 mm-thick wood fiber board for topping 3 and sand for topping 4

5-10: Components of 1 h. fire rated reference floor for wood topping evaluation

Performance of Wood-Frame Floor with Wood Toppings

Topping Type 38 mm Concrete

50 mm-Wood Panel

38 mm 3-Layer Wood Raft

Wood Topping 3

Wood Topping 4

Area Weight (kg/m2)

79.9 20.9 22.7 22.8 66.9

Stiffness(kN-m)

100.6 99.2 3.9 >3.9 >3.9

Cost (C$/m2) 36.6 44.2 37.5 33.5 33.5

Performance Attributes of Wood-Framed Reference Floor with the Toppings:

STC 70 65 63 64 67

IIC 46 56 55 55 60

Creep (mm) 20.3 Negligible Negligible Negligible 6.6p ( ) 20.3 Negligible Negligible Negligible 6.6

Vibration PerformanceRating, from 1 to 5(1)

2.6 3.6 3.9 3.8 3.1

(1) 1-5 five point rating system with 5 as excellent and 1 as very poorThe reference floor without topping was rated as 3.7

- the boundary is unknown, not necessary between25 Hz to 50Hz, can be lower than 25 Hz

low boundary frequency overlap with wood frame floor

25Hz - 50Hz Low Frequency Footstep Impact Sound in Wood-Frame Floors - FPI New Project

Low frequency impact noise, drum effects

- low boundary frequency overlap with wood-frame floorvibrations frequency

- confusion about vibration or sound insulation problem?

- unique problem in wood-frame floors?

- almost no research effort and attention- no understanding- no guidance given in codes and standards- no guidance given in codes and standards- no construction solutions developed

- complaints- no practical applicable and favorable to wood

construction solutions for remedy on-site

FPI New Study – Acoustic and Vibration Performance of Cross-Laminated Timber Floors

Static deflections under

joint and floor centre

Modal test

FPI New Project - Wind Induced-Vibration Control for Tall Wood-Frame Buildings

• Challenge:1. Lack of data of fundamental

natural frequencies andnatural frequencies and

damping ratios of tall wood-

frame buildings for wind

induced-vibration controled

design check required by

NBCC2005

2. Lack of knowledge and g

understanding of wind-induced

vibration performance of tall

wood-frame buildings

Final Remark

• Use systems approach to develop optimum

design and construction solutions for vibration

and sound transmission in wood-frame

buildings to ensure that such solutions are not

in conflict with other optimum solutions

specified for other performance attributes.

www.fpinnovations.cawww.forintek.ca

Creating forest sector solutions