U.S. patent application number 10/533745 was filed with the patent office on 2006-07-06 for composite beam.
Invention is credited to Mark Patrick.
Application Number | 20060144000 10/533745 |
Document ID | / |
Family ID | 28795835 |
Filed Date | 2006-07-06 |
United States Patent
Application |
20060144000 |
Kind Code |
A1 |
Patrick; Mark |
July 6, 2006 |
Composite beam
Abstract
A composite beam is disclosed. The beam includes an internal
horizontal beam (5), a composite slab that is positioned on and
supported by the beam, and a plurality of shear connectors (15),
embedded in the cast concrete and welded to the beam and connecting
the composite slab to the beam. The beam is characterised by a
reinforcing component (19) that is positioned so that reinforcing
elements (61, 63) of the reinforcing component intersect a
conical-type failure surface around the shear connectors in at
least two different, preferably perpendicular, directions.
Inventors: |
Patrick; Mark; (Springwood,
AU) |
Correspondence
Address: |
HAMRE, SCHUMANN, MUELLER & LARSON, P.C.
P.O. BOX 2902-0902
MINNEAPOLIS
MN
55402
US
|
Family ID: |
28795835 |
Appl. No.: |
10/533745 |
Filed: |
November 4, 2003 |
PCT Filed: |
November 4, 2003 |
PCT NO: |
PCT/AU03/01452 |
371 Date: |
November 3, 2005 |
Current U.S.
Class: |
52/334 |
Current CPC
Class: |
E04C 5/04 20130101; E04C
3/294 20130101; E04C 5/07 20130101; E04C 5/0645 20130101; E04B 5/40
20130101 |
Class at
Publication: |
052/334 |
International
Class: |
E04B 5/18 20060101
E04B005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 2002 |
AU |
2002952445 |
Claims
1. A composite beam which includes: (a) a horizontal beam; (b) a
composite slab that is positioned on and supported by the beam; and
(c) a plurality of shear connectors, typically in the form of
headed studs, embedded in the cast concrete and welded to the beam
thereby to connect the composite slab to the beam; and wherein the
composite slab includes: (i) profiled metal sheeting having pans
and parallel ribs, with the sheeting positioned so that the ribs
extend transversely to the longitudinal axis of the beam; (ii)
concrete cast on the sheeting; and (iii) a reinforcing component
embedded in the cast concrete, the reinforcing component including
a plurality of reinforcing elements, with the reinforcing component
being positioned so that the reinforcing elements intersect the
conical-type failure surface or surfaces as described herein in at
least two different directions.
2. The beam defined in claim 1 wherein the reinforcing elements
extend a sufficient distance on both sides of each intersection
point so that the elements are sufficiently well-anchored to
develop tensile forces to prevent shear failure around the
conical-type failure surface or surfaces.
3. The beam defined in claim 1 wherein the reinforcing elements
extend a sufficient distance on both sides of each intersection
point so that a similar failure surface cannot occur further away
from the shear connectors.
4. The beam defined in claim 1 wherein the reinforcing component
includes line wires and cross wires connected together at the
intersections of the wires, with the line wires and the cross wires
forming the reinforcing elements, and with the reinforcing
component being positioned so that there are line wires and cross
wires that have multiple points of intersection with the
conical-type failure surface around each shear connector or groups
of shear connectors in a pan.
5. The beam defined in claim 1 wherein the reinforcing component is
in the form of a mesh that includes line wires and cross wires that
are connected together at the intersections of the wires, with the
line wires and the cross wires forming the reinforcing
elements.
6. The beam defined in claim 4 wherein the reinforcing component is
in the form of a mesh formed from line wires and cross wires that
are connected together at wire intersections, with the line wires
and the cross wires forming the reinforcing elements, with the line
wires having a zig-zag or "waveform" shape with peaks and troughs
along at least part of the length of the line wires, and with the
mesh positioned in relation to the ribs and pans of the profiled
metal sheeting so that the cross wires are parallel to the ribs and
are positioned in the pans and extend through the conical-type
failure surface or surfaces, the peaks of the waveform line wires
are positioned above the ribs, the troughs of the waveform line
wires are positioned in the pans, and sections of the waveform line
wires between the peaks and the troughs extend through the
conical-type failure surface or surfaces.
7. The beam defined in claim 1 wherein the reinforcing component is
in the form of a bar chair designed to be positioned to protrude
through the conical-type failure surface at multiple points.
8. The beam defined in claim 1 wherein the reinforcing component is
positioned so that a substantial part of the transverse
reinforcement is located between 10% and 75% of the height of the
adjacent ribs.
9. The beam defined in claim 1 wherein the ribs are open ribs.
Description
[0001] The present invention relates to composite beams for the
construction industry.
[0002] The term "composite beam" is understood herein to mean a
beam, preferably formed from steel, and a composite slab that are
interconnected by the shear connection to act together to resist
action effects as a single structural member.
[0003] The term "shear connection" is understood herein to mean an
interconnection between a beam and a composite slab which enables
the two components to act together as a single structural member
under the action effect of bending which causes longitudinal shear
forces to develop.
[0004] In conventional composite beams, typically, the shear
connection includes shear connectors, slab concrete, the profiled
steel sheeting, and transverse reinforcement.
[0005] The term "shear connector" is understood herein to mean a
mechanical device attached to a beam (typically to a top flange of
the beam) which forms part of the shear connection.
[0006] The present invention relates particularly, although by no
means exclusively, to composite beams of the type which include:
[0007] (a) a horizontal beam (typically steel and supported at each
end); [0008] (b) a composite slab that is positioned on and
supported by the beam and includes: [0009] (i) profiled metal
(typically steel) sheeting having pans and parallel ribs, with the
sheeting positioned so that the ribs extend transversely to the
longitudinal axis of the beam; [0010] (ii) concrete cast on the
sheeting; and [0011] (iii) reinforcement embedded in the cast
concrete; and [0012] (c) a plurality of shear connectors, typically
in the form of headed studs, embedded in the cast concrete and
welded to the steel beam thereby to connect the composite slab to
the steel beam.
[0013] The term "profiled metal sheeting" is herein understood to
include a plurality of sheets of profiled metal deck that have side
edge formations that allow the sheets to be positioned in side by
side overlapping relationship.
[0014] The present invention is concerned with overcoming a major
problem identified by the applicant that occurs with composite
beams of the type described above, and particularly with the
above-described composite beams that include profiled steel decking
having open ribs.
[0015] The term "open ribs" is understood herein to mean ribs that
have a gap of at least 5=n between adjacent sides of the ribs,
measured at the mid-height of the ribs.
[0016] The problem is a complex type of premature rib pull-off
failure mode that has been observed by the applicant in research
work on composite beams that include profiled steel decking having
open ribs.
[0017] The applicant has previously carried out research work in
relation to particular edge composite beams and found that the
beams failed prematurely by longitudinal shear failure mode
involving horizontal splitting between the tops of the ribs of the
profiled steel sheeting that were adjacent the pans in which the
shear connectors were located. The applicant anticipated that there
would be a similar failure mode and profile for the failure surface
of other edge composite beams and for internal composite beams.
[0018] However, subsequent research work carried out by the
applicant has indicated that failure mode and the actual profile of
the failure surface of other edge composite beams and for internal
composite beams is quite different to that of the particular edge
composite beams tested previously and that the reinforcement
requirements are different.
[0019] Specifically, the applicant has found that the profile of
the failure surface of other edge composite beams and for internal
composite beams is characterised by tapered or conical surfaces
that extend over the shear connectors and down to the pans of the
profiled metal sheeting. This failure surface is hereinafter
referred to as "the conical-type failure surface" and is
illustrated in the drawings and is described further in relation to
the drawings.
[0020] In relation to edge beams, the applicant has found that as
the outstand of the composite slab from the nearest shear
connectors increases there is greater likelihood of premature rib
pull-off failure mode. Consequently, there are different
reinforcement requirements for edge beams depending on the extent
of the slab outstand of the beam.
[0021] The applicant has recognised that the premature rib pull-off
failure mode needs to be suppressed by a suitable reinforcing
component that ties the concrete cone around shear connectors to
the more massive portion of the slab around the conical-type
failure surface.
[0022] With the above in mind, according to the present invention
there is provided a composite beam of the general type described
above which is characterized by a reinforcing component that is
positioned so that reinforcing elements of the reinforcing
component intersect the above-described conical-type failure
surface in at least two different, preferably perpendicular,
directions.
[0023] More particularly, the present invention provides a
composite beam which includes: [0024] (a) a horizontal beam; [0025]
(b) a composite slab that is positioned on and supported by the
beam; and [0026] (c) a plurality of shear connectors, typically in
the form of headed studs, embedded in the cast concrete and welded
to the beam thereby to connect the composite slab to the beam; and
wherein the composite slab includes: [0027] (i) profiled metal
sheeting having pans and parallel ribs, with the sheeting
positioned so that the ribs extend transversely to the longitudinal
axis of the beam; [0028] (ii) concrete cast on the sheeting; and
[0029] (iii) a reinforcing component embedded in the cast concrete,
the reinforcing component including a plurality of reinforcing
elements, with the reinforcing component being positioned so that
the reinforcing elements intersect the above-described conical-type
failure surface in at least two different directions.
[0030] The applicant has found that the reinforcing component
improves dramatically the resistance to the above-described
premature rib pull-off failure mode of composite beams,
particularly in situations in which the composite beams include
profiled steel decking having open ribs.
[0031] Relevant factors in the selection of the reinforcing
component include the following factors. [0032] The reinforcing
elements of the reinforcing component, e.g. mesh line wires and
cross wires, bars, wires, straps, etc. must intersect the
conical-type failure surface that forms around the shear connectors
in at least two directions, preferably perpendicular directions. In
any given situation, it is necessary first to identify the likely
location of the conical-type failure surface and then to select the
design of the reinforcing component that best suits that particular
failure surface. [0033] The reinforcing elements at the multiple
direction intersection points must be sufficient to the the
concrete within the conical-type failure surface to the portion of
the slab outside the conical-type failure surface. This would
normally entail positioning reinforcing elements to pass through at
least two opposed faces of the conical-type failure surface.
[0034] Preferably, however, the reinforcing elements pass through
two perpendicular pairs of opposed faces of the conical-type
failure surface.
[0035] Preferably the reinforcing elements extend a sufficient
distance on both sides of each intersection point so that the
elements are sufficiently well-anchored to develop tensile forces
to prevent shear failure around the conical-type failure surface,
noting that such tensile forces create a clamping force across the
failure surface which causes friction to develop which resists
shear failure around the surface.
[0036] Preferably the reinforcing elements extend a sufficient
distance on both sides of each intersection point so that a similar
failure surface cannot occur further away from the shear
connectors, which would also lead to a concrete pull-out failure,
albeit at a higher level of shear force.
[0037] Preferably the reinforcing elements are connected together
to form a single unit to simplify installation during construction.
Depending on the design of the component, the connections between
the reinforcing elements may be strong (e.g. welded-wire mesh) or
weak (e.g. bars tack-welded or wire-tied together).
[0038] Preferably the reinforcing component does not clash with
other reinforcement required in the composite slab.
[0039] Preferably there is sufficient concrete cover to the top of
the slab for durability, etc.
[0040] Preferably the reinforcing component includes line wires and
cross wires connected together at the intersections of the wires,
for example by welding and/or wire-tying, with the line wires and
the cross wires forming the reinforcing elements, and with the
reinforcing component being positioned so that there are line wires
and cross wires that have multiple points of intersection with the
above-described conical-type failure surface around each shear
connector or group of shear connectors.
[0041] Preferably the reinforcing component is in the form of a
mesh that includes line wires and cross wires that are connected
together, for example by welding and/or wire-tying, at the
intersections of the wires, with the line wires and the cross wires
forming the reinforcing elements.
[0042] In one, although not the only, arrangement the reinforcing
component is in the form of a mesh formed from line wires and cross
wires that are connected together, for example by welding and/or
wire-tying, at wire intersections, with the line wires and the
cross wires forming the reinforcing elements, and with the line
wires having a zig-zag or "waveform" shape with peaks and troughs
along at least part of the length of the line wires. With this
arrangement, preferably the mesh is positioned in relation to the
ribs and pans of the profiled metal sheeting so that the cross
wires are parallel to the ribs and are positioned in the pans and
extend through the conical-type failure surface or surfaces, the
peaks of the waveform line wires are positioned above the ribs
(preferably 30-40 mm), the troughs of the waveform line wires are
positioned in the pans, and sections of the waveform line wires
between the peaks and the troughs extend through the conical-type
failure surface or surfaces.
[0043] The applicant has found that in the above arrangement the
cross wires are very important in terms of reinforcing the
composite beam at the conical-type failure surface.
[0044] Types of the reinforcing component other than mesh include,
by way of example, reinforcing bars or wire, steel strapping
(possibly holed), light steel sections, and high-strength
plastics.
[0045] One particular design of the reinforcing component is in the
form of a bar chair designed to be positioned to protrude through
the conical-type failure surface at multiple points.
[0046] It is preferred that the reinforcing component be positioned
so that a substantial part of the transverse reinforcement of the
component is located between 10% and 75% of the height of adjacent
ribs.
[0047] It is preferred that the beam be a steel beam.
[0048] It is preferred that the profiled metal sheeting be profiled
steel sheeting.
[0049] The ribs of the profiled metal sheeting may be open or
closed ribs. The present invention is applicable particularly to
profiled metal sheeting having open ribs because composite slabs
with open ribbed profiled metal sheeting are more susceptible to
the premature rib pull-off failure mode described above.
[0050] The beam may be supported at opposite ends and at one or
more locations along the length of the beam.
[0051] It is preferred that the shear connectors be headed
studs.
[0052] The shear connectors may be of any other suitable form such
as a structural bolts or channels or shot-fired connectors.
[0053] According to the present invention there is also provided a
reinforcing component for the above described internal composite
beam.
[0054] The present invention is described further by way of example
with reference to the accompanying drawings of which:
[0055] FIG. 1 is a perspective view which illustrates, in
simplified form, an embodiment of a composite beam (without a layer
of concrete that forms part of the beam) in accordance with the
present invention which illustrates the location of the reinforcing
component of the beam in relation to the shear connectors of the
beam and which also illustrates the location of the conical-type
failure surface that the reinforcing component reinforces in the
beam;
[0056] FIG. 2 is an elevation of the composite beam shown in FIG. 1
(with the layer of concrete illustrated in the Figure) in the
direction of the arrow A in FIG. 1;
[0057] FIG. 3 is a perspective view of the reinforcing component of
the embodiment of the composite beam in accordance with the present
invention that is shown in FIG. 1.
[0058] The preferred embodiment of the composite beam 3 in
accordance with the present invention that is shown in the Figures
is in a simplified form to illustrate the composite beam 3 more
clearly. It is noted that the composite beam may be an edge beam or
an internal beam.
[0059] With reference to the Figures, the composite beam 3
includes: [0060] (a) a horizontally extending hot-rolled or
fabricated steel beam 5 which is supported at each end, and
optionally at least one location along the length of the beam so
that the beam extends across multiple spans between the beam
supports; [0061] (b) a composite slab including: [0062] (i)
profiled steel sheeting 7 in contact with a top flange 9 of the
steel beam 5, the sheeting 7 including a plurality of parallel
steel open ribs 11 separated by pans 13 and positioned so that the
ribs 11 extend in a direction that is transverse (in the
illustrated embodiment--perpendicular) to the longitudinal axis of
the beam 5; and [0063] (ii) a layer 29 of concrete cast on the
sheeting 7 and having an upper surface 31 (shown in FIG. 2 only);
[0064] (c) two pairs of shear connectors 15 in the form of headed
studs that extend through the sheeting 7 and are welded to the top
flange 9 of the beam 5 at spaced intervals along the length of the
beam 5; and [0065] (d) a reinforcing component generally identified
by the numeral 19 embedded in the concrete slab for preventing
premature rib pull-off failure mode of the composite beam 3.
[0066] The beam 5 and the composite slab may be of any suitable
dimensions and construction. Typically, the composite slab has a
thickness of at least the height of the ribs 11 and 50 mmmm,
typically 50-100 mm, above the rib height.
[0067] In addition, whilst the sheeting 7 shown in the Figures has
open ribs, the ribs may be closed ribs.
[0068] As is indicated above, the purpose of the reinforcing
component 19 is to intersect in at least 2 directions the
conical-type failure surface that forms around the shear
connectors. As is described hereinafter, in the described
embodiment, the reinforcing component 19 intersects the
conical-type failure surface in two perpendicular directions.
[0069] In any given situation, it is necessary first to identify
the likely location of the conical-type failure surface and then to
design the reinforcing component accordingly.
[0070] In addition, in any given situation, there must be
reinforcement at the intersection points that is sufficient to tie
the concrete within the conical-type failure surface to the portion
of the slab above the conical-type failure surface. This would
normally entail positioning reinforcing elements through at least
two opposed faces of the conical-type failure surface. However,
preferably the reinforcing elements of a reinforcing component pass
through two pairs of opposed faces of the conical-type failure
surface.
[0071] FIGS. 1 and 2 illustrate in diagrammatic form the shape of a
conical-type failure surface that the applicant found in push-off
tests. Specifically, the Figures illustrate the concrete that
remained around the shear connectors 15 after the tests. The
surface of the remaining concrete, which is the conical-type
failure surface, is identified by the numeral 41 in FIGS. 1 and
2.
[0072] The reinforcing component 19 shown in the Figures comprises
a sheet of mesh having four parallel line wires 61 and ten parallel
cross wires 63 that are welded together at the intersections of the
wires and the line wires 61 are formed into a generally sinusoidal
waveform with peaks and troughs along the length of the line wires
61. The line wires 61 and the cross wires 63 form reinforcing
elements of the reinforcing component 19.
[0073] Typically, the line wires 61 and the cross wires 63 are
formed from plain or deformed wire having a diameter of 6-8 mm. The
main requirement for the line wires 61 and the cross wires 63 is
that they be capable of acting as reinforcement. Typically, there
is a spacing of 150 mm between the line wires 61--thus making 450
mm the nominal width of the reinforcing component 19.
[0074] The reinforcing component 19 is formed with regard to the
height of the ribs 11 and the height of the shear connectors 15 and
the location of the conical-type failure surfaces 41 shown in the
Figures so that when the reinforcing component 19 is positioned as
shown in FIGS. 1 and 2 the longitudinal wires 61 and the lower
cross-wires 63 intersect the conical-type failure surfaces 41 at
multiple locations in two perpendicular directions. In the
arrangement shown, the reinforcing component 19 is positioned so
that the cross wires 63 are parallel to the ribs 11 and the peaks
of the longitudinal wires 61 extend over the ribs 11 (with 30-40 mm
clearance) and the troughs of the longitudinal wires 61 extend into
the pans 13. Furthermore, in the arrangement shown, the cross wires
63 that are in the pans 13 that have the pairs of shear connectors
15 are positioned approximately half way up the height of the ribs
11. The applicant has found that positioning the reinforcing
component 19 so that the cross wires 63 are between 10 and 75%,
more preferably between 25 and 75%, of the height of the ribs 11
provides particularly effective reinforcement.
[0075] When a structural composite beam 3 of the basic type shown
in the Figures is loaded, longitudinal slip is induced between the
composite slab and the steel beam 5 which is resisted by the shear
connection between these components.
[0076] In a conventional structural composite beam (without the
reinforcing component 19) the shear connection includes: [0077] (a)
the shear connectors 15; [0078] (b) concrete cast in a slab; [0079]
(c) profiled steel sheeting 7; and [0080] (d) conventional
horizontal reinforcement (not shown) in the vicinity of the shear
connectors 15 and at the level of the top of the sheeting ribs.
[0081] However, in accordance with the present invention, the shear
connection also includes the reinforcing component 19.
[0082] Many modifications may be made to the preferred embodiment
of the present invention described above without departing from the
spirit and scope of the invention.
* * * * *