On Thursday, July 3 ICLR conducted a webinar entitled ‘What can we do to mitigate tornado damage: Observations from the Angus tornado.’ The session was led by Dr. Greg Kopp, Professor in the Faculty of Engineering, Western University. At approximately 5:20 p.m. June 17, an EF2 tornado tore through a subdivision in the town of Angus, Ontario, located just west of Barrie. According to media reports 102 houses were damaged, many severely. First thing the morning of June 18, Western University engineering’s Storm Damage Assessment Team, led by Dr. Kopp, was on the ground to work with Environment Canada to assess and rate the tornado. The team also worked to map the storm track and document damage to 85 homes, 11 of which had complete roof failures. The team found several code deficiencies in Angus, including missing toe-nails and, in some cases, missing wall-to-floor connections. Dr. Kopp led a discussion on the team’s findings and presenting on how tornado damage to homes can be mitigated.

1. Observa(ons
from
the
Angus
Tornado,
2014
June
17

2. Observa(ons
from
the
Angus
Tornado,
2014
June
17
Gregory
A.
Kopp
Boundary
Layer
Wind
Tunnel
Laboratory,
Faculty
of
Engineering,
Western
gakopp@uwo.ca
@gregoryalankopp

3. Objec(ves
of
Presenta(on
• Overview
of
damage
in
Angus
• PaCerns
of
damage/EF-­‐Scale
raGngs
• Comparisons
with
damage
observaGons
from
the
2009
Vaughan
Tornadoes
• Discussion
about
miGgaGng
tornado
damage

4. Damage
track
of
the
Angus
Tornado
Preliminary
track
courtesy
of
Environment
Canada
Most
of
the
damage
was
in
this
neighbourhood

5. Summary
of
Damage
to
Houses
101
houses
with
damage
were
iden(fied
in
Angus:
The
bulk
of
the
damage
was
down
2
streets;
worst
debris
was
in
the
backyard
between
the
streets.

6. Summary
of
Damage
to
Houses
101
houses
with
damage
were
iden(fied
in
Angus:

7. Summary
of
Damage
to
Houses
…views
from
the
backyards,
between
these
two
streets

8. Summary
of
Damage
to
Houses
Red
=
houses
with
roof-­‐to-­‐wall-­‐connecGon
failures
(ie,
roof
is
gone)
Green
=
roof
sheathing
(ie,
small
part
of
roof
is
gone)
Yellow
=
everything
else.
The
bulk
of
the
damage
was
along
two
streets;
however,
the
major
structural
roof
damage
(~22
houses)
was
along
only
one
street

9. Summary
of
Damage
to
Houses
–
Structural
Roof
Failures

10. Summary
of
Damage
to
Houses
–
Structural
Roof
Failures
Angus….7
houses
in
row!
Internal
pressures
do
not
seem
to
have
played
the
same
role
as
they
did
in
the
two
2009
Vaughan
tornadoes
because
of
the
wind
direcGons
involved.

11. Imagine
turning
a
house
upside
down…
hanging
weights
off
the
roof…
and
shaking
it…
WHAT
DOES
THE
WIND
DO
TO
A
HOUSE:

12. Wind
Induced
Pressures
on
the
Roof
of
a
House

13. Internal
Pressuriza(on
oWen
leads
to
roof
failures
Peak
internal
pressures
depend
on
several
parameters…basically
the
posiGve
wall
pressure
is
transferred
into
the
interior
volume

14. Large
windward
wall
opening
–
internal
pressurizaGon
–
roof
failure
VAUGHAN,
2009

15. These
were
the
correct
nails…
but
there
are
only
2,
not
3
VAUGHAN,
2009

16. The
neighbour’s
house…
very
minor
shingle
damage
VAUGHAN,
2009

17. Summary
of
Damage
to
Houses
–
Structural
Roof
Failures
Incorrect
toe-­‐nailed,
roof-­‐to-­‐wall-­‐connecGons
were
prevalent

18. Full-­‐scale
tests
at
the
“3
LiCle
Pigs”
project

19. Summary
of
Damage
to
Houses
–
Structural
Roof
Failures
Lab
tests
of
toe-­‐nailed
connecGons
!
!
!
!
!
!
!
!
!
4../!2$#55!
4../!2$#55!
!
!
!
6!2.)7('%+)8!&.(()&2%.(!
1'/2)$!0%298$'0'+!/$.:!
2.,!,+'2)!%(!+';!2)523<!
!
-9)!;#%+8%(=!&.8)!
$)>#%$)5!?!('%+5!2.!
&.(()&2!)'&9!$../!2$#55!
2.!29)!2.,!,+'2)!./!29)!
0'++5<!
-.,!./!0'++!12.,!,+'2)3!
Our
preliminary
analysis
suggests
that
2
missing
nails
per
connec(on
reduces
the
failure
inducing
wind
speed
by
about
40%

20. !
!
!
!
!
"#$$%&'()!*+%,!
!
!
!
!
-.,!./!0'++!12.,!,+'2)3!
4../!2$#55!
Summary
of
Damage
to
Houses
–
Structural
Roof
Failures
In
contrast,
inexpensive
hurricane
clips
roughly
double
the
capacity.
Our
analysis
of
the
Vaughan
Tornado
suggests
that
these
would
have
kept
the
roofs
on
in
these
events.
We
are
s(ll
analyzing
the
wind
speeds
that
may
have
caused
these
failures.

21. Barrie
Tornado,
1985
2-­‐storey,
hip
roof
2-­‐storey,
gable
roof
Analysis
of
Roof
Damage

22. Looking
at
this
Barrie
photo...
• Peak
coefficient
for
hip
roof
is
about
0.8.
For
a
two
storey
gable
it
is
about
1.2
(50%
larger)
• Hip
roofs
have
larger
capacity
due
to
connecGons
on
all
4
walls,
compared
to
two
walls
for
gable.
• These
two
factors
lead
to
about
a
40%
difference
in
failure
wind
speed,
all
else
being
equal.
Analysis
of
Roof
Damage
…
although
the
damage
is
clearly
DOD-­‐6,
we
are
s(ll
analyzing
the
wind
speeds
that
may
have
caused
the
Angus
roof
failures.

23. EF-­‐Scale
and
Degrees
of
Damage
(DOD)
for
Houses

24. Summary
of
Damage
to
Houses
–
Cladding
Red
=
shingles;
Green
=
siding;
Yellow
=
everything
else

25. Summary
of
Damage
to
Houses
–
Cladding

26. Summary
of
Damage
to
Houses
–
Cladding

27. EF-­‐Scale
and
Degrees
of
Damage
(DOD)
for
Houses

28. Vehicles
–
the
overturned
U-­‐Haul
truck
Vehicles
are
not
included
in
the
EF-­‐Scale
…but
they
were
in
the
original
Fujita
Scale
Correla(ons
of
damage
–
shingles,
garage
doors,
sheathing

29. Damage
observa(ons
near
overturned
U-­‐Haul
truck
RepeGGve
shingle
damage
(>
20%
of
roof)
Some
garage
doors
blown
in

30. Damage
observa(ons
near
overturned
U-­‐Haul
truck
RepeGGve
shingle
damage
(>
20%
of
roof)
Some
garage
doors
blown
in
Roof
sheathing
–
1
or
2
panels
LOOKING
IN
OTHER
DIRECTION

31. Damage
observa(ons
near
overturned
U-­‐Haul
truck
Vehicles
are
not
included
in
the
EF-­‐Scale…
but
they
were
in
the
original
Fujita
Scale
(Fujita,
1981)
120
–
180
km/h
180
–
250
km/h

32. The
overturned
U-­‐Haul
correlates
with
DOD-­‐4:
130
–
187
km/h

This
falls
into
the
EF-­‐1
range
Damage
observa(ons
near
overturned
U-­‐Haul
truck

33. Wind
tunnel
tests
of
U-­‐Haul
trucks
Range
is
about
140
–
200
km/h,
but
most
likely
to
be
at
lower
range
because
of
wind
direc(on.
This
is
remarkably
consistent
with
DOD-­‐4…but
perhaps
lucky,
given
the
uncertain(es!

34. Wind-­‐borne
debris
Goderich,
ON,
F3,
August
2011

35. Wind-­‐borne
debris

36. Wind-­‐borne
debris

37. Large
opening
in
envelope
–
internal
pressure
–
roof
failure
OPENINGS
IN
THE
WALL
VAUGHAN,
2009

38. DEBRIS
IMPACTS
-­‐
Neighbour’s
garage
roof
landed
on
this
house
VAUGHAN,
2009

39. Wind-­‐Borne
Debris
Impacts
ROOF

40. Wind-­‐Borne
Debris
Impacts
ROOF

41. Wind-­‐Borne
Debris
Impacts
Holding
the
roof
structure
on
houses
will
reduce
the
damage
at
adjacent
houses

42. Wind-­‐Borne
Debris
Impacts
Red
=
debris
impacts;
Yellow
=
everything
else.

43. Wind-­‐Borne
Debris
Impacts
Preliminary
analysis:
Red
=
debris
impacts;
Yellow
=
everything
else.
Debris
impact
damage
is
strongly
correlated
with
Structural
Roof
Damage

44. Wall
Failures
This
type
of
“uncharacterisGc”
failure
indicates
issues
with
construcGon

45. Wall
Failures
This
type
of
“uncharacterisGc”
failure
indicates
issues
with
construcGon

46. For
Want
of
a
Nail
For
want
of
a
nail
the
shoe
was
lost.
For
want
of
a
shoe
the
horse
was
lost.
For
want
of
a
horse
the
rider
was
lost.
For
want
of
a
rider
the
message
was
lost.
For
want
of
a
message
the
baCle
was
lost.
For
want
of
a
baCle
the
kingdom
was
lost.
And
all
for
the
want
of
a
horseshoe
nail.
Ques(ons?
gakopp@uwo.ca
@gregoryalankopp

47. Acknowledgements
ICLR
&
NSERC:
for
providing
funding
for
this
research,
and
for
on-­‐going
support
Environment
Canada:
Dr.
David
Sills,
Peter
Kimball,
Mitch
Meredith
UWO
research
team/students:
Sarah
Stenabaugh,
Emilio
Hong,
Chieh-­‐Hsun
Wu,
Derek
Stedman