Note: Descriptions are shown in the official language in which they were submitted.
CA 02308254 2000-OS-OS
SEISMIC AND FIRE-RESISTANT HEAD-OF-WALL STRUCTURE
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a system for creating a seismic-resistant and
fire-
resistant head-of wall structure for a nonload-bearing wall within a building.
Description of the Prior Art
Seismic and fire resistance has become of increasing concern in building
construction. In the construction of buildings the framework for the walls of
a building is
1o formed of horizontal sill members at the floor, at the ends of which
vertical corner posts
support horizontal beams at the ceiling level. Between the corner posts there
are upright
supports, called studs, laterally spaced, usually at uniform intervals, to
provide the
necessary interior structural support for the wall.
Historically, the framework of a building wall was formed entirely of wooden
15 members, including wooden studs. In recent years, however, the use of metal
studs has
gained increased acceptance, especially in the construction of commercial
buildings, such
as office buildings, schools, and hospitals. Metal building studs are
typically formed of
ten to twenty gauge galvanized steel. For ease of fabrication the metal studs
are formed
of sheet metal bent into a generally "C-shaped" cross section. A relatively
broad central
2o web is flanked by a pair of narrower side walls that are bent at right
angles to the web or
base. The edges of the side walls of the metal stud are normally bent over
into a plane
parallel to and spaced from the plane of the web.
In the conventional construction of an interior building wall an overhead beam
having a U-shaped configuration extends along the tops of the studs. The
overhead beam
25 is formed with a horizontally disposed web from which a pair of side walls
depend
vertically on opposite sides of the web. The side walls embrace the sides of
the vertical
studs so that the upper extremities of the studs extend in a perpendicular
manner into the
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concave, downwardly facing channel formed by the overhead beam. The spacing of
the
studs along the length of the beam is typically either sixteen or twenty-four
inches.
One problem which occurs in any building during an earthquake is that the
seismic ground motion from an earthquake introduces both horizontal and
vertical
undulations in the building. Because of their elongated, vertical lengths, the
metal studs
in building wall construction are limber enough to flex sufficiently in a
lateral direction
and thereby resist inelastic deformation during an earthquake. However,
vertical
undulations that vary the distance between the floor and ceiling in a room
during an
earthquake are likely to destroy, or at least damage the integrity, of rigid
structural joints
1o between vertical metal studs and horizontal sill and overhead beam members
between
which the studs extend in a building.
Another problem which may occur is the spread of fire from room to room within
a building. While the structure of interior building walls is largely formed
of fire-
resistant gypsum board sheet, fire can pass between the upper edges of the
gypsum board
and the ceiling. Fire paths are particularly likely to develop if the joints
between the
metal studs in the walls and the ceiling above have been damaged by prior
seismic
activity.
To alleviate these problems a seismic and fire resistant wall structure and
method
was devised. This system is described in U.S. Patent No. 5,127,203. According
to this
2o system the overhead, downwardly facing, U-shaped beam that extends across
the top of
the upright studs is provided with fire-retardant material on its underside
and with
vertical sides that have vertically elongated slots defined thereon. These
vertically
elongated slots are longitudinally spaced at intervals to accommodate the
positions of
studs within a vertical, nonload-bearing wall. Fasteners extend through the
vertically
elongated slots in the overhead beams and into the sides of the metal studs.
The
fasteners, typically sheet metal screws, are tight enough to provide lateral
stability at the
joints between the studs and the overhead beam, but are not so tight as to
prevent relative
vertical motion therebetween.
Preferably, standoff washers are provided at the elongated slots. The standoff
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washers have faces against which the heads of the screws bear and short legs
or flanges
which project through the vertically elongated slots in the side walls of the
overhead
beams. These flanges bear against the sides of the studs. The standoff washers
function
in the manner depicted and described in U.S. Patent No. 5,467,566, with
specific
reference to Fig. 8 of that patent.
As vertical undulations from an earthquake are transmitted through the
structural
components of a nonload-bearing wall as described in U.S. Patent No.
5,127,203, the
elongated, vertical slots through which the stud fasteners extend permit
vertical,
oscillatory motion to occur between the upper extremities of the studs and the
overhead
1o beams of the nonload-bearing walls. As a result, the stud fasteners
maintain structural
integrity so that the wall remains undamaged and does not require repair
following an
earthquake.
In a nonload-bearing wall the web of the beam is preferably secured to the
ceiling
above by screws that extend vertically upwardly through longitudinally
elongated slots in
15 the web of the beam and into the structure of the ceiling above. These
screws also
preferably employ standoff washers of the type described in U.S. Patent No.
5,467,566 so
that the head-of wall structure can accommodate limited interstory drift
during an
earthquake.
A problem which continues to exist in building construction is the difficulty
in
2o making a nonload-bearing wall adequately fire resistant. In a typical
building
construction a ceiling is formed by galvanized steel, fluted decking atop
which a layer of
concrete is poured to form the floor above. The fluted steel decking may, for
example, be
fabricated of eighteen gauge galvanized steel. The flutes, or concave,
downwardly facing
channels defined in the underside of the decking, are typically about three
inches deep
25 and about six inches wide.
Interior, nonload-bearing walls often pass transversely across the flutes. The
beams at the tops of such walls are attached to the underside of the decking
where the
decking projects downwardly between the hollow flutes. Openings having cross-
sectional areas equal to the areas of the flutes are thereby formed above the
beams that
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are located at the top of nonload-bearing, interior walls. These openings form
transverse
passageways across the tops of the walls through which fire can travel.
To prevent the spread of fire through the flutes formed by the decking above
nonload-bearing, interior walls, fire-resistant insulation is packed in the
flute openings
created at the tops of the walls by the flutes. This fire-resistant insulation
may be applied
by spraying it into the flute openings from each side of the wall. When the
insulation
dries and congeals it clogs the flute openings at the top of the wall.
As long as the insulation remains in the flute openings, they remain blocked
and
the insulation prevents the spread of fire across the top of the wall.
However, when a fire
1o is burning within a building, it generates a considerable amount of smoke
which is heated
and expands. The smoke causes a great pressure within a room where a fire is
burning.
It is known that the pressure of smoke from a fire burning within a room
literally blasts
the fire insulation out of the flute openings atop the wall. When this occurs
the fire can
thereupon spread to an adjacent room over the top of the wall through the
flute openings.
15 According to present building construction practice fire insulation is held
within
the tunnel cavities defined by the flutes of the decking by hand cutting the
upper edges of
the gypsum board wall panels to follow the corrugations of the decking. The
wallboard
panels forming the sides of the nonload-bearing walls provide a series of
projections that
block the flute tunnels from the opposite sides of the wall and thereby hold
the insulation
2o in place. However, this system for holding the insulation in position is
extremely time
consuming, laborious, and expensive.
Hand cutting of the upper region of the wall to follow the convolutions of the
corrugated, fluted decking is extremely labor intensive. The labor cost in
creating a
scalloped upper edge at the top of the wallboard adds significantly to the
cost of
25 construction of the wall. Moreover, even if a template is used the hand
cuts result in
significant gaps remaining which must then be caulked. The process of caulking
is also
an extremely laborious, labor intensive process, particularly when it is
necessary to
follow the convolutions of the underside of the fluted decking.
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Moreover, conventional caulking is not seismic resistant. That is, even if the
caulking originally provides an effective burner to air currents, if the
building structure
subsequently is subjected to seismic activity, the caulking crumbles and gaps
that allow
the passage of air currents are opened. When this occurs the wall no longer
offers its
original resistance to the spread of fire. As a result, it has not heretofore
been possible to
provide both seismic resistance and fire resistance in interior building walls
that will meet
the stringent building codes applicable to structures such as schools and
hospitals.
While the system of U.S. Patent No. 5,127,203 does allow limited vertical
cycling
at the head-of wall structure, it does not provide any means for retaining the
insulation
within the flutes of decking above the downwardly facing overhead channel-
shaped
beams. Also, slotted beams must be stocked having webs of the various
different sizes
that are used in different building head-of wall structures. That is, the webs
are typically
provided in about six different widths varying between two and a half and
eight inches.
SUMMARY OF THE INVENTION
15 According to the present invention, a system has been devised which
accommodates both vertical and horizontal seismic movement, as in the system
of U.S.
Patent No. 5,127,203, but which also retains the insulation in the flutes of
the decking
above interior walls. In addition, the system of the present invention uses a
single size,
angle-shaped structure to accommodate walls of all different thicknesses.
2o Elongated, angle-shaped sheet metal strips are provided outside of the
vertical
studs on both sides of the wall. Each sheet metal strip has a vertical leg
which is slotted
in the manner depicted in U.S. Patent No. 5,127,203. The other leg of each
angle strip is
turned outwardly from the studs and bears against the underside of the
decking. Also, the
horizontal, outwardly projecting leg of each angle strip is cut periodically
with diverging
25 slits to form pop-up tab structures at periodic intervals along the length
of the angle strip.
The pop-up tabs are formed by slits cut into the outer edges of the horizontal
legs of the
angle strips so that the shape of the pop-up tabs conforms to and is
substantially the same
as the cross-sectional area of the sheet metal decking flutes. In addition,
longitudinal
score lines are formed across the bases of the pop-up tabs to facilitate
bending these tabs
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upwardly.
The slotted angle strips are secured to the vertical studs with sheet metal
screws
and preferably also standoff washers. The screws project through the vertical,
slotted
legs of the angle strips and into the vertical sides of the metal studs. The
standoff
washers permit limited vertically reciprocal movement between the vertical
slotted legs
of the angle strips and the upright studs.
Longitudinally elongated slots are also preferably formed in the outwardly
projecting, horizontal legs of the angle strips between the pop-up tabs. Sheet
metal
screws used in conjunction with standoff washers project upwardly through the
slots in
to the horizontal angle legs and into the portions of the fluted decking that
make contact
therewith. Thus, the system accommodates horizontal, interstory drift, or
relative
movement between the horizontal legs of the angle strips and the fluted
decking
thereabove.
Once the screws have been used to attach the vertical legs of the angle strips
to
15 the upright studs and the horizontal legs of the angle strips to the fluted
decking above,
insulation batts are inserted into the flutes above the webs of bridge members
that are
formed as short channel-shaped sections that are secured between the angle
strips at the
flutes. The webs of these short, channel-shaped bridge sections support the
insulation
batts from beneath. Once the insulation batts are in position, the pop-up tabs
between the
2o slits in the horizontal legs of the angle strips are bent upwardly to a
generally vertical
orientation, thereby holding the insulation batts in position in the cavities
in the flutes
above the channel-shaped bridge sections therebeneath.
In the building construction industry the structure at the intersection
between the
top of an interior building wall and the ceiling deck of the floor above is
referred to as a
25 head-of wall. There are a number of regulatory building code requirements
specified for
head-of wall structures.
A principal object of the present invention is to provide an interior building
wall
construction that will meet both stringent seismic and stringent fire
resistance code
CA 02308254 2000-OS-OS
standards. For example, the UL (Underwriter's Laboratory) Standard 2079
requires that
joints in metal stud framing withstand twenty cycles of a one-half inch linear
movement
of the structures joined together. The wall system of the present invention
successfully
withstands cycling of one hundred cycles of one full inch of linear movement.
Also, UL Specification 2079 additionally requires the joints of a wall to
remain
fire resistant for a full hour, in the case of some interior walls, and for
two hours in the
case of others. After subjecting the wall to fire, the wall joint and the
insulation in the
cavities of the flutes atop the wall must withstand the pressure applied by a
stream of
water directed thereon from a firehose to simulate the pressure produced
within a
1o building due to fire. Specifically, water under a pressure of forty psi in
a two inch
diameter hose is fired at the insulation pockets in the flutes of the ceiling
from a distance
of twenty feet for twenty seconds.
In conventional building construction systems the blast from the fire hose
readily
dislodges the insulation from the cavities created by the flutes above the
wall beam unless
15 the wallboard has been cut to follow the undulations of the ceiling flutes
and thereby
protect the insulation. However, the system of the present invention employs a
unique
technique for anchoring the insulation in position in the flute cavities above
the wall so
that it is entirely unnecessary to cut the wallboard to match the undulations
of the ceiling
flutes.
20 In testing building wall systems for fire resistance, the joints are
expanded to the
maximum joint opening width for which the system is intended to function.
Thus, it is
evident that conventional design features that tend to enhance seismic
resistance tend to
reduce fire resistance. That is, if there is considerable play in the joints
between upright
metal studs and overhead metal beams to which the studs are attached, openings
are
25 created which reduce resistance to the passage of fire. On the other hand,
if joints are
closed and locked immovably together, they are likely to fail when subjected
to seismic
activity. Thus it has heretofore not been possible to provide an interior
building wall
construction system which meets both the maximum standards for fire resistance
and the
maximum standards for resistance to seismic movement as well. However, the
system of
CA 02308254 2000-OS-OS
the present invention easily surpasses the most stringent fire and seismic
resistance code
specifications that are currently in use.
Another primary object of the present invention is to provide a fire and
seismic
resistant wall construction that maintains its resistance to fire even after
being subjected
to seismic activity. The system of the present invention employs a unique
system for
providing a head-of wall structure with seismic resistance and also for
anchoring batts of
insulation in position in the flute cavities of a ceiling above a line of
vertical sheet metal
studs that form the structural support for an interior, nonload-bearing wall.
Unlike prior systems, there is no necessity for a concave, downwardly facing
1o channel-shaped beam to be positioned atop the upper ends of the studs and
secured both
to the ceiling and to the studs. To the contrary, in place of such a channel-
shaped beam,
the system of the present invention employs a pair of elongated, sheet metal
angle strips.
Each angle strip is of an inverted L-shaped cross section having both a
vertical leg and a
horizontal leg. The angle strips are positioned at to extend horizontally
along the line of
15 the upper ends of vertically oriented sheet metal studs with the vertical
legs of the angle
strips in contact with the upper ends of the sides of the studs. The
horizontal legs of the
angle strips are directed outwardly, away from the vertical legs and away from
the studs.
The horizontal legs reside in contact with the underside of the sheet metal
deck forming
the ceiling.
2o The angle strips are preferably secured to the upper ends of the metal
studs with
seismic fasteners that accommodate limited relative vertical movement between
the studs
and the ceiling. Similarly, the horizontal legs of the angle strips are
preferably secured
with seismic-resistant fasteners to the underside of the metal deck so as to
accommodate
limited horizontal movement, or interstory drift, between the vertical studs
and the ceiling
25 deck thereabove.
The horizontally disposed legs of the angle strips have outer edges, remote
from
the vertical legs and remote from the upright metal studs. The horizontal legs
of the
metal strips are scored or slit so as to define pop-up tabs at spaced
intervals along the
lengths of the angle strips equal to the spaced intervals of the flutes in the
metal deck
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located thereabove. When the wall is oriented perpendicular to the flutes in
the metal
deck of the ceiling, the pop-up tabs can be bent out of the original
horizontal plane of the
horizontal legs of the angle strips upwardly into the downwardly facing
flutes. The pop-
up tabs are of a size and shape so as to extend substantially across the
entire width and
throughout the entire depth of the flutes, thereby forming metal barriers in
the flutes.
Scoring of the horizontal leg can be performed either by creating a continuous
slit
entirely through the sheet metal structure, or by discontinuous cutting
leaving only
narrow regions of uncut metal. Preferably the slits are continuous and extend
inwardly
toward the vertical legs from the outside edges of the horizontal legs of the
angle strips to
to create the pop-up tabs.
According to the system of present invention, the overhead channel-shaped beam
with slotted sides atop the studs is eliminated. Preferably, short sections of
unslotted,
sheet metal, channel-shaped, bridge members are fastened to the angle strips
by screws
that extend through the slots in the vertical legs of the angle strips beneath
the open flutes
15 in the decking thereabove.
Before bending the metal pop-up tabs out of the planes of the horizontal legs
of
the angle strips in which they are formed, batts of insulation are first
positioned in the
flutes directly above the line of upright studs where the flutes pass across
the line of
studs. The batts of insulation are preferably supported from beneath by the
insulation
2o supporting bridges. These insulation supporting bridges each have a flat,
horizontally
disposed web equal to the width of the webs of the studs with downwardly
projecting
channel sides. The channel sides are secured by sheet metal screws to the
vertical legs of
the angle strips so that the webs of the insulation supporting bridges form
platforms
directly beneath the batts of insulation located in the flute. Once the pop-up
tabs of the
25 pair of angle strips are bent into a generally vertical disposition, the
batts of insulation are
thereby entrapped within the flute directly above the line of upright studs
from beneath
by the insulation supporting bridges, and at both sides of the wall by the pop-
up tabs.
In one broad aspect the present invention may be considered to be an
improvement in a building interior head-of wall structure for a nonload-
bearing wall in
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which a plurality of vertical metal wall studs are arranged in a straight
horizontal line and
project upwardly and terminate beneath a ceiling formed of a metal deck having
an
exposed undersurface that defines a plurality of mutually parallel, downwardly
facing
flutes. The improvement of the invention is comprised of a pair of sheet metal
angle
strips that join the wall studs to the ceiling deck. The angle strips each
include a vertical
leg secured to the metal wall studs and a horizontal leg having an outer edge
remote from
the vertical leg. The horizontal leg is scored toward the vertical leg at
longitudinally
spaced intervals along the outer edge to define a plurality of pop-up tabs
that are
bendable to project upwardly into and block the flutes on both sides of the
line of metal
studs.
Quite often in the construction of interior building walls, the flutes of the
sheet
metal ceiling deck extend transversely across the line of metal studs. In such
a situation,
butts of fire-resistant insulation are located in each of the flutes directly
above the line of
wall studs. The pop-up tabs of the pair of angle strips are bent upwardly into
a generally
vertical disposition within the flutes. The pop-up tabs thereby block any
longitudinal
movement of the butts of insulation along the lengths of the flutes.
To support the insulation butts from beneath, short, channel-shaped bridge
members are provided to serve as insulation supports. These bridge members
have
downwardly depending legs that are secured to the pair of angle strips beneath
each of
2o the butts of insulation. The enclosures thus formed are thereby are
confined on all sides
by the insulation supports beneath, the fluted decking material above, and the
pop-up tabs
at opposite ends of the enclosures. The butts of insulation within the
enclosures formed
in the flutes are supported from beneath by the webs of the insulation
supporting bridges
above the line of metal studs. As a consequence, if a fire occurs within a
room on one
side of the wall, the resultant pressure cannot force the butts of insulation
out of their fire
blocking positions atop the wall within the ceiling flutes.
In a typical building installation, the downwardly facing flutes in the sheet
metal
ceiling deck have a trapezoidal configuration. The horizontal legs of the
angle strips are
therefore scored with slits diverging from the outer edges thereof to create
the pop-up
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tabs in a trapezoidal shape corresponding to the cross-sectional shape of the
flutes.
To facilitate bending of the pop-up tabs into a vertical disposition, the pop-
up tabs
are partially scored above the vertical legs of the angle strips and in a
direction parallel to
the line of studs. Scoring may be formed by a line of intermittent
perforations or by a
continuous line of weakness in the metal parallel to the line of studs. The
scoring is
significant enough to allow the pop-up tabs to be bent upwardly using a
hammer, but is
not so pronounced that the pop-up tabs are likely to separate from the angle
strips in
which they are formed.
To accommodate limited interstory drift, ceiling fastener openings are defined
in
1o the horizontal angle legs between the pop-up tabs. The ceiling fastener
openings are
elongated in a direction parallel to the line of metal wall studs. Preferably
a ceiling
fastener slip washer is located in at least some of the ceiling fastener
openings and ceiling
fastening screws extend through the ceiling fastener slip washers to attach
the horizontal
legs of the pair of angle strips to the metal deck.
1 s To accommodate limited vertical movement between the wall studs and the
ceiling above that results from seismic events, vertically elongated stud
fastener openings
are defined in the vertical angle legs. Stud fastener slip washers are located
in at least
some of the stud fastener openings at each of the studs. Stud fastening screws
extend
through the stud fastener slip washers and into the studs to attach the
vertical legs of the
2o pair of angle strips to the vertical studs.
In another aspect the invention may be considered to be a new combination of
elements including a building ceiling, a line of sheet metal wall studs, and a
pair of
elongated angle strips. The building ceiling is formed of a metal deck having
an
undersurface that defines a plurality of mutually parallel, concave downwardly
facing
2s flutes. A plurality of upright, channel-shaped metal wall studs are
arranged in a straight,
horizontal line. Each wall stud has a vertically disposed web between a pair
of opposing
sides. The wall studs are located beneath and extend proximate to the
undersurface of the
metal deck. Each of the angle strips has a vertical leg and a horizontal leg.
11
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The vertical legs of the angle strips are formed with vertically elongated
stud
fastener openings therein, while the horizontal legs are formed with
horizontally
elongated ceiling fastener openings therein. The angle strips are respectively
arranged
against the opposing sides of the wall studs with their vertical legs in
contact therewith
and with their horizontal legs projecting outwardly therefrom away from each
other. The
horizontal legs of the angle strips have outer edges and are slit from the
outer edges in
toward the vertical legs to define pop-up tabs.
The pop-up tabs so defined have lines of bending parallel to the vertical
legs.
Stud fasteners extend into the metal studs through at least some of the stud
fastener
openings to secure the vertical legs of the angle strips to the stud walls
while permitting
limited relative vertical movement therebetween. Ceiling fasteners extend into
the
ceiling through at least some of the ceiling fastener openings to secure the
horizontal legs
of the angle strips to the ceiling, while permitting limited relative
horizontal movement
therebetween.
In still another aspect the invention may be considered to be a seismic and
fire-
resistant interior head-of wall structure. The head-of wall structure of the
invention is
installed between a ceiling formed of a metal deck with an exposed
undersurface that
defines a plurality of mutually parallel, concave downwardly facing flutes,
and a plurality
of vertical metal studs extending upwardly and arranged in linear alignment
with each
other. The vertical studs terminate near the ceiling beneath the undersurface
thereof.
According to the invention a pair of elongated sheet metal angle strips are
provided. Each angle strip has a vertical leg and a horizontal leg and is
positioned
beneath the undersurface of the ceiling. The vertical legs of the angle strips
depend from
the horizontal legs thereof and reside in contact with the metal studs. The
horizontal legs
of the angle strips are directly outwardly away from the metal studs and
reside in contact
with the undersurface of the metal deck.
The angle strips are formed with a plurality of vertically elongated stud
fastener
openings defined in the vertical legs of the angle strips. A plurality of
horizontally
elongated ceiling fastener openings are defined in the horizontal legs of the
angle strips.
12
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The ceiling fastener openings extend parallel to the alignment of the studs
relative to each
other. Stud fasteners extend through at least some of the stud fastener
openings and into
the metal studs to secure the vertical legs of the angle strips to the
vertical studs. This
permits relative vertical movement between the angle strips and the vertical
studs, limited
by the lengths of the stud fastener openings.
Similarly, ceiling fasteners extend through at least some of the ceiling
fastener
openings and into the metal deck to secure the horizontal legs of the angle
strips to the
metal deck. This permits limited horizontal movement between the ceiling and
the angle
strips. This movement is limited by the lengths of the ceiling fastener
openings.
Slits are formed in the horizontal legs of the angle strips. These slits
define pop-
up tabs in the horizontal legs which are of a size that fit into and extend
transversely
across the downwardly facing flutes.
The invention may be described with greater clarity and particularity by
reference
to the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is an exploded perspective view illustrating a seismic and fire-
resistant
interior head-of wall structure according to the invention.
Fig. 2 is a sectional elevational view illustrating the head-of wall structure
of the
invention installed beneath a ceiling in which the flutes of the ceiling deck
extend
2o perpendicular to the line of metal studs forming the wall.
Fig. 3 is a sectional elevational view taken along the lines 3-3 of Fig. 2.
Fig. 4 is a sectional elevational view taken along the lines 4-4 of Fig. 2.
DESCRIPTION OF THE EMBODIMENT
Fig. 1 illustrates a portion of a building having a floor. A ceiling 10 is
formed
about nine feet above the floor. The ceiling 10 is formed of an expansive
corrugated
13
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metal deck member 12 on the underside of which a plurality of concave,
downwardly
facing, channel-shaped flutes 14 are formed. Each of the flutes 14 is of
generally
trapezoidal cross section about six inches in maximum width and about three
inches in
depth. The expansive metal deck member 12 is preferably formed of eighteen
gauge W3
galvanized steel fluted decking. The ceiling 10 also includes a layer of
reinforced
concrete 16 poured thereatop to a minimum thickness of about two and a half
inches.
The concrete 16 is normal weight and has number four steel reinforcement rods
17
therein.
Beneath the ceiling 10 there is a seismic and fire-resistant, interior head-of
wall
1o structure indicated generally at 20. The wall culminating in the head-of
wall structure 20
is installed between the floor beneath and the ceiling 10. That wall is formed
of a
plurality of vertical, metal studs 22, each about one hundred seven and a half
inches in
height. The metal studs 22 terminate near the underside of the metal ceiling
deck 12.
Each of the metal studs 22 is formed three and five-eighths inches in width
from 0.019
15 inch thick galvanized steel. The metal studs 22 are located in a straight,
horizontal line,
no less frequently than twenty-four inches on center, maximum. The studs 22
are more
typically spaced at sixteen inch intervals.
Each of the studs 22 is formed from a single sheet metal structure bent into a
configuration having stud side walls 24 and 26 of uniform width. The stud side
walls 24
2o and 26 are bent perpendicularly out from a relatively broad, central web
28. The edges of
the side walls 24 and 26 remote from the web 28 are turned over to form
marginal lips 30
which enhance the structural rigidity of the studs 22. The studs 22 thereby
have a
generally "C-shaped" cross-section, as illustrated.
The top of the head-of wall 20 is formed by a pair of angle strips 32 and 34
25 fabricated from a minimum of sixteen gauge galvanized steel. The angle
strips 32 and 34
are of identical construction. Each angle strip 32 and 34 is of an inverted L-
shaped cross-
sectional configuration and includes a flat, vertically oriented leg 36 and an
flat,
horizontally oriented leg 38. Each of the angle strips 32 and 34 is formed
from a flat strip
of sheet steel that is bent at right angles to form an apex 40 that serves as
a delineation
14
CA 02308254 2000-OS-OS
between the vertical leg 36 and the horizontal leg 38. The vertical legs 36
depend from
the horizontal legs 38 of the angle strips 32 and 34.
The vertically oriented angle legs 36 are fabricated with vertically elongated
stud
fastener openings 42 defined therethrough. The stud fastener openings 42 are
each
preferably about one-quarter inch in width and are spaced longitudinally from
each other
at regular one and one-half inch intervals. The stud fastener opening slots 42
are centered
within the vertical legs 36 between the apex 40 of the angle strips 32 and 34
and the
lower edge 43 of the vertical legs 36. Each vertical leg 36 is preferably two
and one-half
inches in height as measured between the apex 40 and the lower edge 43
thereof.
to The horizontal legs 38 of the angle strips 32 and 34 project outwardly in
opposite
directions from each other and away from the vertical legs 36 thereof and from
the studs
22. The horizontal legs 38 are also initially flat throughout their length and
have an outer
edge 45 remote from the vertical legs 36 and the apices 40.
The horizontal legs 38 are scored by slits 50 and 52 that extend entirely
through
the thickness of the sheet steel forming the horizontal legs 38. The slits 50
and 52
diverge from each other from the outer, horizontal leg edge 45 and terminate
at the apex
40. The slits 50 and 52 extend across the width of the horizontal leg 38 from
the outer
edges 45 in toward the vertical legs 36 to define trapezoidal-shaped pop-up
tabs 54. The
size and shape of the trapezoidal pop-up tabs 54 corresponds closely to and is
just slightly
2o smaller than the cross-sectional size and shape of the flutes 14.
Elongated, longitudinally extending ceiling fastener openings 58 are defined
in
the horizontal angle legs 38 between the pop-up tabs 54. The ceiling fasteners
openings
58 are elongated in a direction parallel to the line of metal studs 22.
In assembling the head-of wall structure 20, the vertical legs 36 of the angle
strips
32 and 24 are positioned in contact with the sides 24 and 26, respectively, of
the metal
studs 22. The horizontal legs 38 of the angle strips 32 and 34 are directed
outwardly
away from the metal studs 22 and are pressed into contact with the
undersurface of the
metal deck 12.
CA 02308254 2000-OS-OS
Seismic-resistant connections allowing limited vertical movement are provided
between the vertically disposed legs of the angle strips and the sides of the
upright studs.
Seismic-resistant connections between the horizontal legs of the angle strips
permit
limited, interstory drift between the metal decking of the ceiling and the
upright studs
therebeneath.
Standoff washers 39 are provided for each of the elongated ceiling fastener
slots
58. The structure and use of the standoff washers 39 is illustrated and
described in U.S.
Patent No. 5,467,566, which is incorporated herein by reference. Each standoff
washer
39 is a flat, preferably rectangular structure having an elongated slot 41
defined therein.
to The standoff washers 39 are preferably about seven-eighths of an inch in
width and about
three-quarters of an inch in length. The longitudinal slot 41 is preferably
about three-
eighths of an inch in length.
In the formation of the slots 41, the structure of each standoff washer 39 is
deformed so as to provide a pair of ribs or lips that extend out from the
otherwise planar
15 structure of the standoff washer 39 a distance of about one-sixteenth of an
inch. The lips
extend longitudinally along the sides of the elongated slots 41.
A standoff washer 39 is positioned in each of the ceiling fastener slots 58
such
that the lips thereof extend up through the horizontal legs 38 and protrude a
very short
distance therebeyond. Ceiling fasteners 46, which may be no. 10 powder
actuated
2o fastening screws, are fired from beneath the horizontal angle legs 38 and
extend up
through the standoff washers 39 positioned at the ceiling fastening slots 58,
through the
steel deck 12, and into the concrete 16. The ceiling fasteners 46 may be
installed at eight
or twelve inch intervals along the length of the horizontal angle legs 38,
depending upon
the spacing of the flutes 14 in the deck 12.
2s The heads of the fasteners 46 bear against the standoff washers 39 to hold
the
horizontal angle legs 38 up against the metal deck 12 of the ceiling 10.
However, since
the lips of the standoff washers 39 on both sides of the slots 41 therein
contact the surface
15 of the deck 12, and since the slots 58 are greater in length than the
length of the lips of
the standoff washers 39, a certain amount of longitudinal movement is
permitted between
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CA 02308254 2000-OS-OS
the deck 12 and the horizontal angle legs 38 when the head-of wall 20 is
subjected to
seismic activity.
The lower ends of the studs 22 are secured to a floor sill track in a
conventional
manner. The upper extremities of the studs 22 are fastened to the vertical
angle legs 36
of the angle strips 32 and 34 using standoff washers 39 and sheet metal
framing screws
44. The function of the standoff washers 39 and the stud fastening slots 42
are described
in U.S. Patent No. 5,467,566 and in U.S. Patent No. 5,127,203, respectively,
both of
which are hereby incorporated by reference.
A standoff washer 39 is positioned at the center of each slot 42 that is
aligned
1o with a stud 22. The standoff washer 39 is centered within the slot 42 and
placed
thereagainst so that the lips on each side of the standoff washer slot 41
project through
the structure of the vertical angle legs 36 of the angle strips 32 and 34. The
standoff
washer lips project slightly beyond the thickness of the twenty-gauge stock
forming the
angle strips 32 and 34 so as to reside in contact with the side walls 24 and
26 of each stud
15 22.
The stud fastening screws 44 are then power driven through the standoff washer
slots 41 into the structure of the stud side walls 24 and 26 therebeyond,
thereby forming
stud fastener openings 31 therein. By securing angle strips 32 and 34 to the
studs 22 in
this manner, the angle strips 32 and 34 are securely fastened to the studs 22.
2o Nevertheless, the standoff washers 39 and the vertically elongated slots 42
permit a
limited amount of relative vertical movement between the studs 22 and the
angle strips 32
and 34, thereby providing resistance to seismic activity.
The head-of wall structure 20 is further comprised of channel-shaped sections
of
insulation supporting bridges 62. Each bridge 62 has a flat, horizontally
disposed web 64
25 from the edges of which channel legs 66 and 68 depend downwardly. The width
of the
insulation supporting bridges 62 between the depending legs 66 and 68 is
substantially
equal to the width of the studs 22 between the sides 24 and 26 thereof. The
length of
each insulation supporting bridge 62, as measured between the transverse edges
70 and
72 thereof is at least a great as the maximum width of the flutes 14. The webs
64 of the
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CA 02308254 2000-OS-OS
insulation supporting bridges 62 thereby form platforms that span the flutes
14 where the
flutes 14 cross the horizontal line of studs 22.
The vertical side walls 66 and 68 of the insulation supporting bridges 62
reside in
contact with the vertical legs 36 of the angle strips 32 and 34. The vertical
side walls 66
and 68 of the insulation supporting bridges 62 are secured to the vertical
legs 36 of the
angle strips 32 and 34 by means of one-half inch length, pan head, self
drilling or self
tapping no. 6 sheet metal screws 44 that extend through the vertically
elongated openings
42 that lie directly beneath the flutes 14.
The portions of the flutes 14 that pass transversely across the line of studs
22 and
1o the angle strips 32 and 34 located thereatop form cavities in the form of
transverse
tunnels. These cavities or tunnels are filled with batts 80 of an insulation
material above
the line of studs 22. In conventional interior building wall construction the
cavities in the
flutes above the nonload-bearing interior wall beams are filled with Monokote
MK-
6/CDF insulation as a fire insulating substance. Although Monokote is
resistant to fire, it
15 is somewhat brittle even when installed, and becomes more brittle as it
ages. As a
consequence, if the building is subjected to seismic activity, the metal
decking in a floor
above a nonload-bearing wall and the wall structure will move relative to each
other.
This movement causes the Monokote to be crushed in the flute cavities and to
crumble
and dissipate.
2o Preferably a superior insulating material is utilized to form the
insulation batts 80.
The insulation batts 80 are preferably formed of a compressible, nonflammable,
mineral
fiber insulation called safing. This mineral fiber substance is a fireproof
material that is
produced as a by-product of slag. It is heated and spun and resembles spun
fiberglass in
texture, although it is dark brown in color. More importantly, it is a spongy,
resiliently
25 compressible material that does not become brittle with age, nor with
exposure to
temperature extremes. Furthermore, it is extremely low in cost.
The mineral fiber insulation batts 80 are preferably cut slightly larger than
the
width of the insulation support 62 as measured between the vertical sides 66
and 68
thereof. Also, the insulation batts 80 are preferably initially cut to a
height greater than
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CA 02308254 2000-OS-OS
the depths of the flutes 14.
Once the insulation batts 80 have been positioned atop the insulation supports
62,
the pop-up tabs 54 are bent upwardly into a generally vertical orientation.
Preferably, the
demarcations between the vertical legs 36 and horizontal legs 38 of the angle
strips 32
and 34 are partially scored along the portions 82 of the apices 40 between the
slits 50 and
52 beneath the flutes 14. Once the insulation batts 80 have been positioned in
the cavities
or tunnels formed by the flutes 14 where they cross the insulation supporting
bridges 62,
an installer strikes each of the trapezoidal areas of the pop-up tabs 54
delineated by the
die cuts 50 and 52. The hammer blows are delivered from beneath the undersides
of the
l0 horizontal legs 38 of the angle strips 32 and 34. Since the portions 82 of
the apices 40 are
weakened by partial scoring, the forces from the hammer blows inelastically
bend the
pop-up tabs 54 upwardly and inwardly in toward each other about the lines of
bending
formed by the partially scored portions 82 of the apices 40. The pop-up tabs
54 may
thereby be bent upwardly into a generally vertical orientation, generally
parallel to the
15 vertical legs 36 of the angle strips 32 and 34 and in substantially
coplanar relationship
therewith.
When the pop-up tabs 54 have been bent up into a vertical position, they
extend as
transverse blocking partitions substantially across the entire width of each
flute 14. An
enclosure 84 is thereby formed within which each insulation batt 80 is
confined. The
2o upper portions of the enclosures 84 are formed by that portion of the sheet
metal deck 12
forming the top and inclined walls of the trapezoidal-shaped flutes 14. The
bottom of the
enclosures 84 are formed by the web 64 of the insulation supporting bridges
62. The
ends of the enclosure 84 are formed by the pop-up tabs 54 of the angle strips
32 and 34,
respectively.
25 As is evident from Fig. 4, the insulation batts 80 are encapsulated within
the
enclosures 84 and cannot be dislodged even by high pressure on either side of
a wall
formed at the line of studs 22. Once the head-of wall structure 20 is
completed as
depicted in the drawings, wallboard sheets are mounted against the opposite
sides 24 and
26 of the vertical studs 22. The wallboard sheets are conventional three-
quarter or five-
19
CA 02308254 2000-OS-OS
eighths inch thick type "X" gypsum board panels, indicated in phantom at 86 in
Figs. 3
and 4. The wallboard panels 86 are attached to the studs 22 in a conventional
manner by
self tapping screws.
The wall forming the head-of wall structure 20 was then subjected to a hose
test.
Water under pressure was fired at the pop-up tabs 54 to see if the insulation
batts 80
could be dislodged therefrom using water pressure. Water under a pressure of
forty psi in
a two inch diameter fire hose was fired from a distance of twenty feet to
impact directly
against the pop-up tabs 54. The water pressure was selected so as to simulate
the
pressure of smoke in a room at the fire stop level.
1o Unlike comparable wall sections in which the unique construction of the
head-of
wall 20 was not employed, the wall section 20, in accordance with the
invention, easily
passed the hose stream test. The pop-up tabs 54 prevented dislodgement of any
sort of
the mineral fiber batts 80 from the enclosures 84 formed in the flutes 14
above the
insulation supporting bridges 62.
1s The use of elongated angle strips mounted at the upper extremities of the
sides 24
and 26 of the studs 22 in place of a downwardly facing sheet metal channel
spanning the
sides of the studs has several advantages. Specifically, a single size of
elongated angle
strip may be utilized in any interior head-of wall installation. The widths of
studs does
vary in building construction. There are currently six different stud widths
in use in
2o present-day building construction which vary between two and a half and six
inches in
width. In conventional practice this requires the availability of channel
beams having six
different widths. In contrast, the same size angle strip may be utilized in
constructing a
head-of wall according to the present invention regardless of the width of the
studs
employed. This eliminates the need for different dies and sheet metal bending
setups in
25 the fabrication of the structural materials utilized to connect the studs
to the sheet metal
decking above.
A pair of angle strips are significantly lighter in weight than a channel beam
of
the same length. Also, the angle strips of the invention can be installed one
at a time.
The angle strips employed in the head-of wall construction according to the
invention are
CA 02308254 2000-OS-OS
thereby far easier to manipulate than a channel beam of the same length.
Therefore, they
can be installed much more rapidly, thus reducing both the time and expense of
fabrication of a head-of wall structure.
Undoubtedly, numerous variations and modifications of the invention will
become readily apparent to those familiar with fire retardant and seismic
resistant
building wall construction. For example, the dimensions of the angle strips,
fastener slot
openings, and the size and selection of sheet metal stock and fasteners may be
varied.
Accordingly, the scope of the invention should not be construed as limited to
this specific
embodiment depicted and described herein.
21
