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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.
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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.
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