U.S. patent number 3,600,868 [Application Number 04/803,222] was granted by the patent office on 1971-08-24 for shear connectors.
This patent grant is currently assigned to Illinois Tool Works Inc.. Invention is credited to Friedrich Karl Knohl, Edgar Clifton Wilson.
United States Patent |
3,600,868 |
Wilson , et al. |
August 24, 1971 |
SHEAR CONNECTORS
Abstract
A shear fastener for securing concrete decking relative to a
supporting structure in a laminar building structure. The fastener
includes a stud, an enlarged means at one end, and a spacer adapted
to enclose the stud shank and isolate it in spaced relation from
the encapsulating concrete to permit bending moments to be applied
to the stud shank rather than a straight shear stress when the
decking shifts relative to the supporting structure.
Inventors: |
Wilson; Edgar Clifton (N/A),
Knohl; Friedrich Karl (N/A, IL) |
Assignee: |
Inc.; Illinois Tool Works
(IL)
|
Family
ID: |
25185938 |
Appl.
No.: |
04/803,222 |
Filed: |
February 28, 1969 |
Current U.S.
Class: |
52/334; 52/336;
411/373 |
Current CPC
Class: |
E04B
5/40 (20130101); E04B 5/29 (20130101); E04B
1/4157 (20130101); E04B 1/41 (20130101); E04B
2005/237 (20130101) |
Current International
Class: |
E04B
5/17 (20060101); E04B 1/41 (20060101); E04B
5/29 (20060101); E04B 5/23 (20060101); E04B
001/48 (); F16B 043/00 () |
Field of
Search: |
;52/334-336,573,699,167,127,704-710,452,454,676,679-684,378,379,521,700
;85/50,53,55,56 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Abbott; Frank L.
Assistant Examiner: Ridgill; James L.
Claims
We claim:
1. A fastening means for use in a laminar building assembly which
includes a supporting structure and a concrete deck superpositioned
thereon wherein the fastener means is arranged to secure the
concrete deck to the supporting structure, said fastener means
comprising associated stud and spacer elements, said stud element
having one end adapted to be secured to the supporting structure
and enlarged means at the opposite end of the stud element adapted
to be embedded in the concrete deck, said spacer element having
integral circumferentially uninterrupted cylindrical and
frustoconical portions both of which surround the stud element, the
cylindrical portion of the spacer element engaging the stud element
adjacent the enlarged means over a predetermined axial height which
is sufficient to continuously center the stud element relative to
the spacer element, the frustoconical portion of the spacer element
diverging outwardly from the cylindrical portion in a direction
away from the enlarged means of the stud element and terminating in
a free end which is adapted to contact the supporting structure,
said frustoconical portion having a predetermined axial height
substantially greater than the cylindrical portion and having its
inner wall surface laterally spaced from the stud element over its
entire axial height by progressively increasing radial dimensions
as the frustoconical portion diverges away from the enlarged means
of the stud element, the spacing of the frustoconical portion form
the stud element in planes taken perpendicular to the axis of the
stud element being substantially equal throughout the entire
circumferential extent of the frustoconical portion, thereby
providing an isolated chamber for the stud element enabling bending
thereof relative to the one end which is secured to the supporting
structure when the concrete deck is shifted relative to the
supporting structure.
2. A fastener of the type claimed in claim 1 wherein said stud and
spacer element includes means for preassembly, said preassembly
means including radially inwardly directed flange means extending
from said spacer and protuberance means on said stud adapted to
cooperate with said radially directed flange means on said spacer
to accomplish axial preassembly of said stud with said spacer but
to permit rotation of said stud relative to said spacer.
3. A fastener of the type claimed in claim 1 wherein said
supporting structure is apertured and said stud is a screw capable
of creating a mating thread in an initially unthreaded aperture in
said supporting structure.
4. A fastener of the type claimed in claim 1 wherein said stud
includes a threaded portion of a predetermined diameter and an
unthreaded portion of a substantial extent adjacent said enlarged
means acting as said cylindrical portion, said spacer including a
radially inwardly directed flange presenting opposed surfaces
acceptable by said unthreaded portion and axially restrained by
said threaded portion whereby said stud is rotatable relative to
said spacer but axially restrained relative thereto.
5. A fastener of the type claimed in claim 1 wherein said stud is a
self-piercing stud adapted to be driven into said supporting
structure and having the axial movement restrained by said spacer
means.
6. A fastener of the type claimed in claim 1 wherein the free end
of said stud spaced from said supporting structure is provided with
screw threads, said enlarged means including nut means
complementary to said screw and mounted thereon for securing said
spacer means in juxtaposition to said supporting member.
7. A fastener of the type claimed in claim 6 wherein said spacer
means includes a threaded portion in the cylindrical portion
integral with its reduced dimension adjacent the upper extremity
for engaging said screw while said opposite enlarged end portion of
said spacer engages said supporting structure, flange means
extending laterally from said cylindrical portion forming said
enlarged means for embedment in said concrete.
8. A fastener of the type claimed in claim 1 wherein said stud and
spacer assembly includes rigid means for contacting said supporting
structure to control the axial compressive stress exerted by said
stud on said spacer.
9. A fastener of the type claimed in claim 8 wherein said means for
contacting said supporting structure includes a laterally extending
shoulder intermediate the axial extremities of said stud to control
the penetration of said stud through said supporting structure.
10. A fastener of the type claimed in claim 8 wherein said means
for contacting supporting structure includes an axially disposed
rigid element from the smaller dimension of said spacer to a point
adjacent to a plane passing through the free end of its enlarged
portion.
11. A fastener of the type claimed in claim 1 wherein said spacer
includes a laterally extending bearing element at the end of the
enlarged portion of said spacer.
12. A fastener of the type claimed in claim 11 wherein said spacing
element includes radially outwardly extending flange adapted to
bear on said supporting structure.
13. A fastener of the type claimed in claim 11 wherein said bearing
element includes a radially inwardly rolled lip adapted to
strengthen the hoop characteristics of said spacer when subjected
to axially disposed compressive forces.
14. A laminar building assembly comprising s supporting structure,
a concrete deck superpositioned thereon and fastening means
extending outwardly from the supporting structure, securing the
concrete deck to the supporting structure, said fastening means
including associated stud and spacer elements, said stud element
having one end secured to the supporting structure and enlarged
means at the opposite end of said stud element embedded in said
concrete deck, said spacer element having integral
circumferentially continuous cylindrical and frustoconical portions
which surround the stud element, the cylindrical portion of the
spacer element engaging the stud element at least at a position
axially spaced from the supporting structure for centering the stud
element relative to the spacer element, the frustoconical portion
of the spacer element diverging outwardly from the cylindrical
portion of said spacer element and terminating in a free end which
contacts the supporting structure, said spacer element at least at
said frustoconical portion being laterally spaced from the stud
element for a predetermined axial distance away from the supporting
structure providing an isolated chamber for the stud element
enabling bending thereof relative to the supporting structure when
the concrete deck is shifted relative to the supporting
structure.
15. A system of the type claimed in claim 1 wherein said supporting
includes a transverse structural member and corrugated sheeting
disposed substantially perpendicularly to said member, said stud
traversing said sheeting and securing same to said member, said
spacer means and said enlarged means projecting upwardly from said
sheeting a substantial distance to insure encapsulation by said
concrete deck.
16. A system of the type claimed in claim 15 wherein said
corrugated sheeting includes ridges and valleys, certain of said
valleys including spaced apertures and having axially extending
integral tapered hubs serving as said spacer means surrounding said
apertures and of such a size as to accept said studs in spaced
relation thereto.
17. A system of the type claimed in claim 15 wherein said stud
element is a screw which includes a drilling point capable of
forming the aperture in said supporting structure at random
locations and forming a mating thread in the aperture so formed.
Description
BACKGROUND
Current building practices for offices, industrial and multiple
dwelling construction have gravitated strongly to various
modifications of concrete structures. Many involve a sequential
fabrication of floor after floor of reinforced concrete, wherein
wooden forms are sequentially erected for each floor and its
supporting columns with steel wire and rod being utilized to absorb
certain stresses which normally would result in a failure of the
concrete. Another type involves the use of prestressed concrete
members which are fabricated either on-site or off-site and erected
in building block style with appropriate connection means.
The type of concrete construction that the present invention is
primarily concerned with is related to the first type mentioned
above except that the basic loads are carried by beams or joists,
generally, the steel bar joist being the preferable form because of
its low weight to load carrying ratio. A corrugated sheet material
which may be steel, reinforce d asbestos type or of other suitable
material is laid transversely to the beam or joist with the troughs
and ridges of the corrugations generally being laid perpendicular
to the beams or joists. A fastener is applied to secure the sheet
to the supporting structure and concrete is then poured onto the
sheet material, which serves as a permanent form, and encapsulates
the fastener which normally projects upwardly from the sheet
material. Fasteners previously utilized for such assemblies have
taken the form of either weld studs or screws. In the case of weld
studs it has been found that the welding operation is complicated
by the fact that most steel corrugated sheet material is galvanized
and this results in a difficult welding operation plus destruction
of the galvanized coating thereby leading to possible corrosion of
the sheeting and joint. The other blind application joints,
utilizing screws, normally must be predrilled and tapped or
alternatively a thread-forming screw used to form its on threads or
a nut applied to the blind end of the screw.
In both forms of fastening, mentioned above, the stud is totally
encapsulated or rigidly captured in concrete from its juncture with
the sheeting to its enlarged head spaced from said juncture. Thus,
during wind loading, seismic shock or any other form of stress
directed to a structure utilizing such fastenings, there is a force
applied which tends to laterally shift the concrete deck. Such a
movement of the concrete transfers a shear load to the stud at its
juncture with the supporting structure and the return of the
structure to its initial position applies a shear load in the
reverse direction. While it is thought that there is some tendency
during such a shifting for a tensile load to be applied to some
fasteners, such tensile loading is minor in comparison to the shear
load.
SUMMARY
The present invention contemplates a shear fastener for use in
laminar building structures subjected to transverse forces by wind
loading, seismic shock and other external stresses where floor and
roof decking has a tendency to shift when the structure is
stressed. Where the prior art rigidly encapsulated the fastening
means used to secure the various strata of the laminate, the
present invention provides means to isolate the stud fastener from
the concrete at least at the juncture of the stud with the
supporting structure and for a substantial portion of its axial
extent whereby shifting of the concrete deck results in the
application of a bending moment to the stud rather than the
application of a shear load.
The invention also contemplates the use of such a fastener assembly
of a stud and spacer or isolating means in a system which includes
a supporting beam or joist, a permanent corrugated decking form and
a concrete deck for use as a floor or roof component in a building
structure.
DESCRIPTION OF DRAWINGS
FIG. 1 is an elevational view in partial section showing system
utilizing a fastener incorporating the teachings of the present
invention;
FIG. 2 is an enlarged elevational view in partial section of a
portion of the system shown in FIG. 1;
FIG. 3 is an elevational view in partial section of a fastening
means of the type contemplated by the present invention;
FIG. 4 is an elevational view in partial section of a preassembled
fastening means;
FIG. 5 is an elevational view in partial section of a modified form
of the teachings of the present invention;
FIG. 6 is an elevational view in partial section of another
embodiment of the present invention;
FIG. 7, 8 and 9 are elevational sectional views of three
modifications to the fastening means wherein stop means are
included;
FIG. 10 is a further modification of the head of the fastening
means of the present invention;
FIGS. 11 and 12 are partial sectional elevational view illustrating
modifications to the spacer means of the present invention;
FIGS. 13 and 14 are elevational views in partial section showing
nonblind type applications of the present invention; and
FIGS. 15, 16 and 17 are elevational views in partial section
showing modifications to the stud element utilized in the present
invention.
DESCRIPTION
Referring now to the drawing wherein similar parts are designated
by similar numerals throughout the description, a laminar
construction of the type contemplated by the present invention
generally includes a supporting structure 20 having a beam 22 and
corrugated sheeting 24; fastening means 26 and a concrete deck
28.
The supporting structure 20 utilizes a beam 22 which can take the
form of an I-beam, a wood beam or preferably a bar joist which
includes an upper and lower runner and connecting bar structure
which because of its geometric relationship to the runner forms a
truss-type structure. It is generally chosen because of its low
weight to load-carrying ratio. The secondary element of the
supporting structure is corrugated sheeting 24 which normally has
its valleys 30 and crests 32 running transverse to the axis of the
beam 22. The corrugated material can be fabricated from galvanized
steel or may also be constructed of a reinforced asbestos type of
material. Other materials will be apparent to those skilled in the
art so long as the material chosen has a fireproof quality since in
this form of construction the supporting structure comprising the
beam and sheeting remains in place throughout the life of the
building and must have this quality of being fireproof.
The fastening means 26 generally includes a stud 40, an enlarged
means or head 42 at one end of the stud 40, means for fastening the
stud to the supporting structure, and an isolating or spacer means
44. In the preferred embodiment shown in FIG. 3 the stud 40 is
provided with threads 46 through a substantial portion of its
length and a washer base 48 on a hex head to provide a maximum
laterally extending engaging means, for purposes best set forth
hereinafter. To facilitate assembly of this screw with the
supporting structure a drill point 48 is provided at the opposite
extremity of the screw. Surrounding a substantial portion of the
axial extent of the threaded shank 46 is an isolating or spacer
means 44. In this preferred embodiments the spacer includes a
substantially frustoconical portion 50 and a cylindrical portion 52
integral with the minor diameter of the conical portion 50. The
internal diameter of the cylindrical portion is equal to or
slightly less than the crest diameter of the thread 46 so that the
stud 40 can be preassembled by an interference fit with the spacer
means 44. The spacer 44 can be a drawn member or in the case of the
present embodiment a rolled split member with the edges of the
split being maintained in abutting relationship. In the present
embodiment a power tool is applied to the hex faces of the head 42
and the drill point 48 is brought into contact with a valley 30 of
the corrugated sheeting 24 when it is positioned in superposed
relation to a beam 22. The rotation of the fastener results in the
drill point 48 creating an aperture through the sheeting 24 and the
beam 22 with the threaded portion 46 forming its own thread. The
fastener assembly 26 progresses axially until such time as the
bottom or major end of the conical portion 50 is brought into
engagement with the upper surface, as viewed in the drawing, of the
valley 30 with the flange 46 being brought into intimate
relationship with the cylindrical portion 52. At this point the
driver torques-out and ceases driving. Thus, the threaded shank 46
is isolated from its surrounding environment by the spacer means 44
through a substantial portion of its axial extent. The screw is
thus sealed at the juncture of the cone 50 with the valley 30 and
the cylindrical portion 52 with the flange 46. Concrete of a
suitable mixture is then poured on top of the supporting structure
and encapsulates the fastening means 26 as well filling the valley
30 and covering the crest 32. Preferably the fastening means 26 has
an axial extent such that the enlarged head 42 is positioned
adjacent to or above a plane passing through the crest 32 of the
corrugated sheet 24 thereby insuring captivation of the enlarged
head 42 within the concrete at or above a shear line falling in the
plane passing through the crest 32. In this fashion any movement in
a vertical direction, as viewed in the drawings, will apply a
tensile load to the fastener stud 40 through the head 42.
Thus, when a transverse load is applied to the concrete deck 28 the
fastening means 26 can bend at its juncture with the supporting
structure as represented by the sheet of material 24 and the beam
or joist 22. As has been previously pointed out the prior approach
was to totally encapsulate the stud and thereby create a pure shear
force to be applied to the fastener at is juncture with the
supporting structure. As can be recognized a bending moment can be
repeated a great number of times without resulting in total fatigue
of the fastener as when compared with the direct application of a
shear load.
It will be recognized that other forms of studs can be utilized for
the fastening means. For example, the sheet and beam can be
predrilled or can be drilled at the site and a thread-forming screw
be utilized as the fastening means. A weld stud can be spot welded
to the joist 22 with a suitable bead weld being provided around an
aperture that is predrilled in the corrugated material 24 to
thereby retain the stud in the position. Still another form could
be a drive stud where a hydraulic or explosive force is applied to
the stud to pierce the corrugated material and the joist with the
spacer or isolating means 44 limiting the axial position of the
stud. Still other forms will be hereinafter described.
Referring now to FIGS. 4 through 17 various forms of isolater or
spacing means 44 will be described in conjunction with stud forms.
While the preferred embodiment disclosed an interference fit
between the cylindrical section 52 and the threaded shank 46 for
preassembly purposes it may be desirable to provide a mechanical
interlock which would restrain the axial relative movement between
the spacer means and the stud while permitting rotative movement
between the two. FIG. 4 discloses a threaded shank 46a having an
unthreaded portion 60 adjacent the head adapted to accept an
inwardly directed flange 62 for preassembly of the screw and
spacer. While a frustoconical form was previously described to
isolate the stud from its surrounding environment it would be
totally feasible to utilize a cylindrical form of spacer 64, as
shown in phantom in FIG. 4, with a plurality of laterally extending
flange means 66 for purposes of engagement with the concrete to
provide attachment therewith and to accept a tensile load.
FIG. 5 discloses a threaded screw 46b having an increased diameter
70 which is greater than the crest diameter of the threads of the
screw to form a shoulder 72 adapted to bear on top of the crest 32b
whereby the enlarged head 42b with its flange 46b can be captivated
within the concrete for fastening purposes. In this case the
corrugated sheeting 24b with its associated crest 32b serves as the
isolating means for the screw 46b which is driven directly through
the crest 32b into the beam 22b.
A further modification of the present invention can be seen in FIG.
6 wherein the valley 30c has a portion of its horizontal extent
dimpled or cupped upwardly to form an integral spacer means 44c to
provide a conical portion 50c and a cylindrical portion 52c which
isolates the stud 40c from the encapsulation by the concrete, not
shown.
As was previously mentioned, the spacer means 44 can be fabricated
at a split sleeve-type member. It will be recognized that if an
excessive axial force is applied to the sleeve the split will tend
to circumferentially open and thereby permit the ingress of
concrete to the screw. To eliminate this possibility one of the
forms shown in FIGS. 7 through 9 can be utilized. In FIG. 7 the
spacer means 44a is provided with an axially extending cylindrical
portion 80 which is a reversely bending extension of the upper
cylindrical portion 52d. It will be noted that the lower extremity
of the tubular member 80 is spaced a small amount from the lower
extremity of the conical portion 50d whereby the portion 50d can be
sprung out to provide resilient takeup before the extremity of 80
will contact the corrugated sheet 24 and stop the axial progression
of the stud 40d. The modification shown in FIG. 8 utilizes a
separate cylindrical member 82 which is substantially coextensive
with the spacer means 44e and which will serve as a stop when it
contacts the sheet. The modification shown in FIG. 9 employs
basically the same technique except that the stop means instead of
being a part of the spacer 44f is an enlarged shank portion 70f
forming a shoulder 72f at its juncture with the threaded shank 46f.
The shoulder 72f forms a stop which limits the axial extent to
which the screw shank 46f can be driven into the supporting
structure 20f thereby limiting the axial stress placed on the
spacer member 44f.
To facilitate bending of the stud 46g it may be desirable in
certain instances, to provide a conical or slightly spherically
clamping surface 86 adjacent the washer face 46g. whereby the head
42g can be shifted relative to the spacer means 44g. Such a
fastener is shown in FIG. 10.
To increase the strength of thinner materials a laterally extending
flange 90 can be provided on a spacer 44h, as seen in FIG. 11. The
flange 90 provides a certain degree of hoop strength to the spacer
and also provides a shoulder or foot for contact with the surface
of the corrugated material to provide frictional resistance against
spreading or splitting of the spacer 44h, if it is a split member.
A similar strengthening means is the inwardly rolled lip 92 at the
lower end of the spacer means 44j, as seen in FIG. 12. Such a
rolled rim increases the hoop strength and provides a line contact
for sealing purposes with corrugated material.
While each of the previously illustrated embodiments have shown the
use of a self-drilling screw it is contemplated as being within the
purview of this invention to make use of other forms of mechanical
fasteners. In FIGS. 13 and 14 the beams 22k and 22m as well as
their associated sheets 24k and 24m respectively are predrilled to
accept a screw-threaded member 100 and 100m which are inserted from
the blind side by axial telescoping through the beam and then the
sheet, as the reverse of the techniques mentioned heretofore. In
FIG. 13 the spacer means 44k is provided with internal threads 102
in the cylindrical portion 52k which are complementary to the
threads of the screw 100. A laterally extending flange 104 is
provided for purposes of encapsulation and tensile engagement with
the concrete to be poured around the fastener. The modification of
of FIG. 14 shows the use of a separate washer face nut element 106
for maintaining the spacer unit 44m in intimate contact with the
corrugated material 24m. The function of both of these is
substantially identical to previously disclosed embodiments in that
they tensilely engage the concrete while permitting bending moments
to be applied to the screws 100 and 100m respectively.
In FIG. 15 the stud 40n is welded as at 110 to the beam 22n. The
enlarged head 42n in this embodiment is in the form of a sphere. It
is contemplated that when the cement encapsulates the enlarged head
it will provide a ball and socket type joint between the enlarged
head and the cement and permit free bending of the stud 40n under
extreme conditions of movement between the various strata of the
laminar structure.
FIG. 16 discloses a weld stud 40p which has its free extremity
welded, as at 110p and has its enlarged head 42p in the form of a
truss head. The function of such a head is similar to the spherical
head to provide a broad face for engagement with the concrete for
tensile purposes. The last embodiment shown in FIG. 17 utilizes a
drive stud 40q having a bullet nose point 120 which when moved
axially under great force, either hydraulic or explosive, will
penetrate the sheet material 24q and the beam 22q with the spacer
44q serving as a stop means to limit the axial movement of the stud
40q to a point where the head 42q has engaged the upper end of the
spacer and the spacer is in engagement with the sheet material 44q
for sealing for isolating purposes, as set forth hereinbefore.
In many of the embodiments in the disclosure hereinabove a
self-drilling screw is utilized as the stud in the fastening means
assembly. Such a screw fastening normally provides a tight fit
between the structures which are drilled and in which a thread is
formed by the screw. It should be recognized, in the present
environment, that such a screw to be functional must be a hardened
screw. Conversely, the corrugated sheet material 24 is a thin soft
material. Thus, when the various strata of the laminar structure
shift relative to one another, the hardened screw which is isolated
by the spacer 44 from the surrounding concrete will tend to
teardrop or tear the soft thin sheet forming the corrugated
material 24, thereby eliminating any shear stresses bought to bear
against the stud at its juncture with the supporting structure and
permit its bending within the confines of the spacer.
Additionally, the stud 40 can be provided with limited case
hardening adjacent its tip or free end which normally is utilized
at its point of fastening to the supporting structure with the
balance of the axial extent being left in a soft or natural
condition which will provide easier bending through greater
ductility when it is in the soft condition. This will facilitate
the desired end result.
Thus, the principle of this invention permits a small diameter,
hardened fastener with a highly tensile value to match the crushing
load of concrete by offering a large cross section via the spacer
44. This distributes the crushing force on the concrete over a wide
area which can be sustained by the concrete whereas when the axial
force is concentrated on a small diameter fastener there is a
positive tendency for the concrete to crush and crumble. Further,
the method of creating a void around the shank of the fastener can
take several shapes, for example, by an axial extension of the
cylindrical portion 52 and a foreshortening of the conical portion
50 it is possible to "tune" the fastener and control the degree of
load deflection by selection of the void configuration. It should
be recognized that while most of the embodiments are indicated as
having a cylindrical portion at the top flaring into a
frustoconical bottom portion, the spacer could be frustoconical all
the way from the top to the bottom with the amount of void created
around the shank being contoured so as to control the deflection
available in the fastener and thereby bringing about the "tuning"
effect.
Other embodiments will be apparent to those skilled in the art but
it is the broad intent of the present invention to provide a spacer
means for purposes of isolating a stud at its juncture with the
supporting structure whereby the stud, as a part of a laminar
structure, can be deflected to meet the load-deflection
requirements as the strata of the structure moves with wind,
seismic and other types of loads. The fastener also, as has been
indicated, provides a large area of contact to preclude crushing of
the concrete and to balance the high tensile strength of the
hardened fastener with the crush rating of the concrete. It is felt
that the various embodiments set forth hereinabove accomplish this
goal and it is our intent to be limited only by the appended
claims.
* * * * *