Arkansas Shelter/Safe Room

siennatearfulUrban and Civil

Nov 25, 2013 (3 years and 7 months ago)

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Arkansas Shelter/Safe Room
Program


This state program assists Arkansas home
-
owners who choose to install a shelter or safe
room on their property. The program covers up
to 50 percent of the cost and installation not to
exceed$1,000. The statewide rebate program
applies to persons who have installed safe
rooms or in
-
ground shelters at their primary
residence on or after Jan. 21, 1999. Safe room
installation must meet FEMA Publication 320 or
National Performance Criteria for Tornado
Shelters standards.

Arkansas Tornadoes by County

Tornadoes in Arkansas


The state has experienced 1,681
tornadoes between 1950 and 2007,with
239 tornadoes that were F3 and higher.


State of Arkansas ranked fourth in the
nation in deaths and fifth in injuries.


Average of nearly 30 tornadoes


annually.

Tornadoes in Arkansas


On the afternoon of Feb. 5, 2008 a weather
system moved across the State of Arkansas,
resulting in severe thunderstorms, tornadoes
and flooding across the state. According to the
National Weather Service, this was the deadliest
severe weather event in the state since March 1,
1997. One of the tornadoes tracked 123 miles,
which is the longest track on record in Arkansas
since 1950. The tornadoes claimed the lives of
13 people.

Map showing the 2008 tornado track


Safe rooms in residences


A residential safe room
costs anywhere between
$3,000 and $10,000. it is
mandatory for the safe
room to meet the
requirements established
by FEMA 320 or meet the
National Performance
Criteria for Tornado
Shelters.

Safe Rooms in Residences


A safe room is a
reinforced room built in a
new or existing above
-
ground structure that can
provide protection during
storms. A safe room is
often a closet or


bathroom that has been
modified to provide
occupant protection in the
event of a tornado


Commercially
-
Manufactured Shelters


An alternative to the in
-
home safe room is a
commercially
-
manufactured shelter that,
depending on the type, can be installed above
-
ground, below ground or partially below
-
ground.
In
-
ground safe rooms have no state regulations;
however, they must meet local codes. They cost
between $1,200 and $4,500. They must be
constructed of a waterproof material, properly


ventilated, and contain doors that meet the
National Performance Criteria for Tornado
Shelters.

Commercially
-
Manufactured Shelters

Continuous Load Path


Structural systems that provide a continuous
load path are those that support all loads acting
on a building: laterally and vertically (inward and
outward, upward and downward). A continuous
load path can be thought of as a “chain” running
through a building. The “links” of the chain are
structural members, connections between
members, and any fasteners used in the
connections (e.g., nails, screws, bolts, welds, or
reinforcing steel).


Continuous Load Path

LOAD PATH FAILURE

Wood 2x4 launched at 100 mph

Windborne Debris (Missile) Impacts

Windborne Debris (Missile) Impacts


Walls, doors, and other surfaces inclined
30 degrees or more from the horizontal
are tested at the design missile speed of
100 mph.


Those surfaces inclined 30 degrees or
less from the horizontal are tested at 67
mph.

Debris Impact Criteria



Underground shelters or portions of them with less than
12 inches of soil cover should be able to meet the same
criteria as if the surfaces were exposed.



Impact Resistance


Wood Systems:
Must be attached using AFG
-
01
adhesive and #8 wood screws penetrating at least 11/2”
and spaced not more than 6” apart.


Sheet Metal:
14
-
gauge steel sheet can resist
perforation only when it is used as the last layer on the
non
-
impact face on the interior (shelter side) of the wall.
If sheet metal alone is relied on for missile impact
protection, it should be 12 gauge or heavier
.


Composite
Wall:6
-

and 8
-
inch
-
thick concrete


masonry unit (CMU) walls that are fully grouted with
concrete and reinforced with #4 reinforcing steel (rebar)
in every cell can withstand the impact of a 15
-
lb 2x4
wood

Wood Systems

Sheet Metal Systems

Composite Wall Systems

Composite Wall Systems

Reinforced Concrete Wall

Roof Systems


Based on the observed behavior of roof
specimens, it is believed that roof designs
that incorporate a uniform thickness (i.e.,
flat slab of at least 4” with #4 rebar)
provide a more uniform level of protection
from large debris impacts, than a waffle
slab, or ribbed slab.

Single
-
Door Systems Less Than 36
Inches Wide


Steel doors with exterior skins of 14 gauge or
thicker. The minimum hardware reinforcement
should be 12 gauge.


Lighter
-
skinned steel doors may be used with
modification. The modification is the addition of a
14
-
gauge steel sheet to either side of the door
using 1/4X1 ¼ inch self
-
tapping screws 6” OC.


No wood door has ever passed the missile test.


However, by adding a layer of 14 gauge steel
sheathing on either side the door will pass the
test.

Door Frames


Sixteen
-
gauge steel
door frames in either
a welded or
knockdown style are
known to be adequate
to carry design wind
and impact loads on a
single door

Welded Door Frame

Knock Down Style Frame

Door Hardware


Steel doors with supplemental latching
mechanisms near the top and the bottom are
required to carry design wind loads and to
prevent an inward
-
swinging door from being
knocked open with a well
-
placed missile.


Three latching mechanisms and 3 hinges are
required (6 pts of attachment) so that, if debris
impacts close to one and destroys it, two will be
left to carry the wind loads.


Door Hardware


Doors with two additional mortised, cylindrical dead bolts
(with solid 1/2
-
inch
-
thick steel throw bolts with a 1
-
inch
throw into the door jamb) above and below the original
latch would meet the requirement of the wind pressure
and missile impact tests. Deadbolts that are operable
from the inside shall be keyed from the outside.

Door Systems


A three
-
point latching
system operated with
a single
-
action lever,
built with heavy duty
steel with a 1” solid
bolt with a 1” throw,
that activates two 1
3/8” solid hook
-
bolts
will also pass the
missile test

Windows


Testing indicates that glass
windows in any configuration
are undesirable for use in
tornado shelters. It is therefore
recommended that glazing units
subject to debris impacts not be
included in shelters or that they
be covered with material that
meets the standards for doors.

Ventilation


Passive ventilation is required
for all residential shelters. This
is defined as the non
-
powered
air flow into and through the
shelter envelope by way of
openings that provide air for
breathing. Openings must be a
minimum of 4” OD and be
protected to prevent intrusion
of wind
-
borne debris.

Flood Hazard Considerations


The lowest floor of the shelter must be elevated 1
foot above the base flood elevation from any of
the flooding sources. All utilities or services
provided to the shelter must be protected from
flooding as well.



Don’t site shelters where the


possibility of flooding is present.


Other Hazard Considerations


Hazardous materials



Power lines



Gas mains



Fire

References


FEMA Pub. 361 ( Design and Construction
Guidance for Community Shelters)


FEMA Pub. 320 ( Taking Shelter from the
storm: Building a safe room in your home)


To request a copy of this publication, call 1
-
800
-
480
-
2520


National Performance Criteria For Tornado
Shelters


Association Standard for the Design,
Construction, and Performance of Storm
Shelters