U.S. patent application number 10/516280 was filed with the patent office on 2006-10-12 for reinforced structural steel decking.
This patent application is currently assigned to UNIVERSITY OF WESTERN SYDNEY. Invention is credited to Mark Patrick.
Application Number | 20060225374 10/516280 |
Document ID | / |
Family ID | 3836110 |
Filed Date | 2006-10-12 |
United States Patent
Application |
20060225374 |
Kind Code |
A1 |
Patrick; Mark |
October 12, 2006 |
Reinforced structural steel decking
Abstract
A structural steel decking panel for supporting wet concrete and
subsequently reinforcing the concrete after it has hardened is
disclosed. The decking panel includes an elongate profiled steel
sheet having a top side and an underside and a plurality of
elongate reinforcing members connected to the sheet. The decking
panel is characterized in that the strength of the longitudinal
shear connection between the sheet and the reinforcing members is
sufficiently high to resist longitudinal shear failure between the
reinforcing members and the sheet when the decking panel is
subjected to top loading with construction loads and wet
concrete.
Inventors: |
Patrick; Mark; (NEW SOUTH
WALES, AU) |
Correspondence
Address: |
THE WEBB LAW FIRM, P.C.
700 KOPPERS BUILDING
436 SEVENTH AVENUE
PITTSBURGH
PA
15219
US
|
Assignee: |
UNIVERSITY OF WESTERN
SYDNEY
SECOND AVENUE
KINGSWOOD
AU
2747
|
Family ID: |
3836110 |
Appl. No.: |
10/516280 |
Filed: |
May 27, 2003 |
PCT Filed: |
May 27, 2003 |
PCT NO: |
PCT/AU03/00643 |
371 Date: |
April 11, 2006 |
Current U.S.
Class: |
52/336 |
Current CPC
Class: |
E04B 5/40 20130101; E04G
11/46 20130101 |
Class at
Publication: |
052/336 |
International
Class: |
E04B 1/16 20060101
E04B001/16; E04B 1/20 20060101 E04B001/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2002 |
AU |
PS 2546 |
Claims
1-13. (canceled)
14. A structural steel decking panel for supporting wet concrete
and subsequently reinforcing the concrete after it has hardened,
the decking panel comprising: (a) an elongate profiled steel sheet
having a top side and an underside that is rolled-formed from flat
steel strip and has a maximum thickness of no more than 1.6 mm; and
(b) a plurality of elongate reinforcing members connected to the
sheet and selectively reinforcing the sheet, the reinforcing
members extending along the whole length of the sheet or over short
lengths of the sheet; wherein the strength of the longitudinal
shear connection, as defined herein, between the sheet and the
reinforcing members is sufficiently high to resist longitudinal
shear failure between the reinforcing members and the sheet when
the decking panel is subjected to top loading with construction
loads and wet concrete.
15. The decking panel defined in claim 14 wherein there is complete
shear connection, as defined herein, between the sheet and the
reinforcing members.
16. The decking panel defined in claim 15 wherein the shear
connection between the sheet and the reinforcing members is at
least 30% of the complete shear connection, as defined herein.
17. The decking panel defined in claim 16 wherein the shear
connection between the sheet and the reinforcing members is at
least 40% of the complete shear connection.
18. The decking panel defined in claim 14 wherein there is partial
shear connection, as defined herein, between the sheet and the
reinforcing members.
19. The decking panel defined in claim 14 wherein there is complete
interaction, as defined herein, between the sheet and the
reinforcing members.
20. The decking panel defined in claim 14 wherein the reinforcing
members are connected to the underside of the sheet.
21. The decking panel defined in claim 14 wherein the reinforcing
members are welded or glued to the sheet.
22. The decking panel defined in claim 14 wherein the reinforcing
members are elongate members.
23. The decking panel defined in claim 22 wherein the elongate
members extend in a longitudinal direction of the sheet.
24. The decking panel defined in claim 14 wherein the reinforcing
members are in the form of a bar or rod or plate.
25. The decking panel defined in claim 14 wherein the profiled
sheet includes top and bottom flat flanges interconnected by web
elements.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to structural steel decking
panels and in particular to structural steel decking panels
constructed from profiled steel on which concrete is poured to form
composite slabs.
BACKGROUND
[0002] Structural steel decking panels serve a dual function when
used in the construction of composite steel/concrete floor slabs.
The panels act as structural formwork by supporting building
materials and personnel before the concrete hardens. After the
reinforcing steel (bars and/or mesh) has been laid, concrete is
poured on top of the decking panels, and once the concrete reaches
sufficient compressive strength, the decking panels act as main
reinforcement by interacting with the concrete, and continue to do
so for the remainder of the life of a building.
[0003] Structural steel decking panels are roll-formed from flat
steel strip into long panels of uniform cross-section. Decking
panels are principally distinguished by differences in their
cross-sectional shape or profile. The profiles used in the world
today are very varied, for instance trapezoidal decks like Fielders
Steel Roofing Pty Ltd's (Fielders') KF70 and KF225 with "open ribs"
(see FIG. 1) versus decks with "closed ribs" like Fielders' KF57
(see FIG. 2), but they all have one factor in common: the nominal
thickness of the sheeting is constant around the profile perimeter.
Also, roll-forming machines are only designed to roll steel
sheeting up a certain maximum thickness, typically 1.2 mm and
always not exceeding 1.6 mm. This significantly restricts the
maximum flexural stiffness and ultimate strength of a deck with a
set geometry.
[0004] Some decking panel manufacturers modify the decking panels
they produce once the panels have been roll-formed. This is done to
improve their functionality or structural performance.
[0005] Important aspects of structural performance are flexural
stiffness and ultimate strength. Flexural stiffness affects the
magnitude of vertical deflections, in particular under the weight
of wet concrete. The moment capacity and shear capacity of critical
regions affects ultimate strength.
[0006] It is known to modify a roll formed decking panel by
attaching a flat sheet of steel across the entire base of the panel
to form a "cellular deck". This is done to create closed cells for
the passage of sensitive building services, in particular
electrical cabling for computers, thus giving rise to so-called
"electrified floors". However, whilst the flat steel sheets improve
flexural stiffness and ultimate strength, the "cellular decks" do
not provide optimum structural efficiency. Furthermore, in
applications where they are not required for cabling etc, they are
not a cost effective decking.
[0007] It is an object of the invention to provide a decking panel
that has improved structural performance in terms of flexural
stiffness and ultimate strength and avoids at least some of the
problems described above.
SUMMARY OF THE INVENTION
[0008] Broadly, according to the invention there is provided a
structural steel decking panel for supporting wet concrete and
subsequently reinforcing the concrete after it has hardened, the
decking panel including:
[0009] (a) an elongate profiled steel sheet having a top side and
an underside; and
[0010] (b) a plurality of elongate reinforcing members connected to
the sheet, and
[0011] (c) wherein the strength of the longitudinal shear
connection, as described herein, between the sheet and the
reinforcing members is sufficiently high to resist longitudinal
shear failure between the reinforcing members and the sheet when
the decking panel is subjected to top loading with construction
loads and wet concrete.
[0012] The decking panel of the present invention is selectively
reinforced in areas in which there is a need for higher structural
performance in terms of flexural stiffness and ultimate strength,
particularly when the decking panel is subjected to top loading
with construction loads and wet concrete. One of the key features
of the decking panel of the present invention, as described above,
is that the strength of the longitudinal shear connection between
the sheet and the reinforcing members is sufficiently high to
resist longitudinal shear failure between the reinforcing members
and the sheet when the decking panel is top loaded. This is an
important feature because it facilitates higher structural
performance, particularly when the decking panel is subjected to
top loading with construction loads and wet concrete.
[0013] The term "strength of the longitudinal shear connection" is
understood herein to mean the strength of the connection between
connected elements, such as the sheet and the reinforcing members,
to resist longitudinal shear in response to longitudinal shear
force generated by an applied top load and, therefore, is a measure
of the ability of the connection to resist longitudinal shear.
[0014] In some situations it is preferable that there be complete
shear connection, as described herein, between the sheet and the
reinforcing members.
[0015] The term "complete shear connection" is understood herein to
mean a condition in which the moment capacity of a vertical
cross-section of the decking panel is not governed by the strength
of the longitudinal shear connection between the connected
elements.
[0016] In other situations it is sufficient that there be partial
shear connection, as described herein, between the sheet and the
reinforcing members.
[0017] The term "partial shear connection" is understood herein to
mean a condition in which the moment capacity of a transverse
cross-section of the decking panel is governed by the strength of
the longitudinal shear connection between the connected.
[0018] Preferably the shear connection between the sheet and the
reinforcing members is at least 30% of the complete shear
connection.
[0019] More preferably the shear connection between the sheet and
the reinforcing members is at least 40% of the complete shear
connection.
[0020] Preferably there is complete interaction, as described
herein, between the sheet and the reinforcing members.
[0021] The term "complete interaction" is understood herein to mean
a condition in which there is no significant longitudinal slip
along the interface between connected elements, i.e. the sheet and
the reinforcing members, so the connected elements can be
considered to act as a single, reinforced composite element when
determining flexural stiffness and calculating vertical
deflections.
[0022] Preferably the reinforcing members are connected to the
underside of the sheet.
[0023] Preferably the reinforcing members are welded or glued to
the sheet.
[0024] Preferably the reinforcing members are elongate members.
[0025] Preferably the elongate members extend in a longitudinal
direction of the sheet.
[0026] Preferably the reinforcing members are in the form of a bar
or rod or plate.
[0027] Preferably the profiled sheet includes top and bottom flat
flanges interconnected by web elements.
[0028] Specific embodiments of the invention will now be described
in some further detail with reference to and as illustrated in the
accompanying figures. These embodiments are illustrative, and are
not meant to be restrictive of the scope of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0029] Preferred embodiments of the invention are illustrated in
the accompanying representations in which:
[0030] FIGS. 1 and 2 show cross-sectional views of prior art
structural steel decking panels;
[0031] FIG. 3 shows a cross-sectional view of a structural steel
decking panel according to a first embodiment of the invention;
[0032] FIG. 4 shows a cross-sectional view of a structural steel
decking panel according to a second embodiment of the
invention;
[0033] FIG. 5 shows a cross-sectional view of a structural steel
decking panel according to a third embodiment of the invention;
[0034] FIG. 6 shows a cross-sectional view of a structural steel
decking panel according to a fourth embodiment of the
invention;
[0035] FIG. 7 is a diagrammatic side view of the steel decking
panel of FIG. 6 with a support directly under the reinforced area
and the reinforcing members shown diagrammatically to illustrate
the general location (and length) of the members;
[0036] FIG. 8 is a diagrammatic side view of the steel decking
panel of FIG. 5 with the reinforced area between supports and the
reinforcing members shown diagrammatically to illustrate the
general location (and length) of the members;
[0037] FIGS. 9, 10 and 11 show cross-sectional views of further
embodiments of structural steel decking panels according to the
invention;
[0038] FIG. 12 is a plot of applied load versus deflection for test
samples generated during an experimental program to evaluate the
invention; and
[0039] FIG. 13 is a series of spanning curves generated during the
experimental program.
[0040] A first embodiment of the invention is shown in FIG. 3.
[0041] With this embodiment, the structural decking panel 10
comprises a roll formed elongate steel sheet 12 having a top side
14 and an underside 16. The decking panel 10 is profiled and
comprises top flanges 40, bottom flanges 42, interconnecting web
elements 44, and side edge formations 46 that enable adjacent
panels to be positioned side-by-side in an overlapping
relationship.
[0042] The decking panel 10 comprises two discrete elongate
reinforcing members 20, each of which is connected to the underside
16 of the sheet 10 and extend in the longitudinal direction of the
sheet 12. The reinforcing members 20 are connected to the sheet 12
so that there is substantially complete interaction between these
components under normal operating conditions.
[0043] With this embodiment of the invention, the reinforcing
members 20 are cylindrical rods having a circular cross-section.
However, reinforcing members with a wide variety of cross-sectional
shapes may be employed to suit specific manufacturing and design
requirements.
[0044] With this embodiment of the invention, the reinforcing
members 20 are attached to the underside 16 of the sheeting 12 and
are positioned in cavities defined by ribs 48 in the top flanges 40
of the panel 10. The arrangement is such that there is substantial
contact between the sheet 12 and the reinforcing members 20. The
substantial contact contributes to strength of the shear connection
between the reinforcing members 20 and the sheet 12. In addition,
the arrangement is such that the reinforcing members 20 cannot come
into contact with concrete that is poured on top of the panel 10.
This means that there are no potential problems of reduction of the
longitudinal slip resistance of the decking panel after the
concrete hardens. Furthermore, the reinforcing members 20 do not
interfere with any of the normal construction operations undertaken
on the top side 14 of the decking panel such as the placement of
reinforcement and pouring and compaction of concrete.
[0045] In other embodiments of the invention (not shown),
reinforcing members 20 can be attached to selected areas of the top
side 14 of the sheet 12.
[0046] The reinforcing members can be continuous over the whole
length of the panel 12 or alternatively can be localised over short
lengths in selected locations in order to improve economy or to
avoid interference with the passage of vertical building
services.
[0047] Two examples of panels having localised positions and
lengths of reinforcing members 20 are shown diagrammatically in
FIGS. 6, 7 and 8. FIG. 6 is a transverse cross-section that
illustrates the positions of reinforcing members 20 against the web
elements of the panel 12. The reinforcing members 20 extend part
way along the length of the sheet 12. FIG. 7.illustrates an
arrangement in which the positions of the reinforcing members 20 in
the FIG. 6 panel are selected to be over supports 30 for the panel.
FIG. 8 illustrates an arrangement in which the positions (and
length) of the reinforcing members 20 in the FIG. 6 panel are
selected to be between supports 30 for the panel.
[0048] The reinforcing members 20 can be made from a variety of
materials including steel or advanced composite materials.
[0049] The reinforcing members 20 can be attached to the sheet 12
by various means including gluing, welding, screwing, clinching,
and crimping.
[0050] It is preferred that the reinforcing members 20 be welded or
glued to the sheet 12 in order to produce the required
connection.
[0051] Attachment of the reinforcing members 20 to the sheet 12 can
occur after a roll-forming process for forming the profiled sheet
12. Alternatively, the sheet 12 can be reinforced (by attachment of
reinforcing members 20) prior to roll-forming the sheet.
[0052] As is indicated above, the strength of the connection
between the reinforcing members 20 and the sheet 12 is important
when the decking panel is subjected to top loading with wet
concrete. With the embodiments described above and other
embodiments of the invention, complete shear connection or partial
shear connection may exist at a critical cross-section.
[0053] The term "critical cross-section" is understood herein to
mean a transverse cross-section at which the ratio of design
bending moment to design moment capacity (or when designing for
shear, the ratio of design shear force to design shear capacity) is
a maximum. (This is the cross-section from which failure would
emanate.) Longitudinal shear failure can be avoided during the
formwork stage, ie before concrete hardens, by adjusting the design
loads if the critical cross-section is likely to exhibit relatively
low partial shear connection. Assuming that the moment capacity of
the reinforcing members 20 acting alone is small compared with that
of the composite element of the reinforcing members 20 and the
sheet 12 (as is the case for the preferred embodiments of the
invention, but not necessarily for all embodiments of the
invention) then the degree of shear connection required is
reasonably high (about 30% or higher). Otherwise, the reinforcing
members 20 will not make a significant contribution to the moment
capacity of the decking panel 10 during the formwork stage.
[0054] Depending on the situation, the strength of the connection
between the reinforcing members 20 and the sheet 12 may not be as
important during the composite stage, i.e. after the concrete
hardens and a composite slab is formed. In this stage, the
mechanical interlock developed by the decking panel 10 and the
hardened concrete (per unit length of panel) usually becomes a
significant factor in providing flexural stiffness and ultimate
strength of the composite slab. Thus, break-down of glue connecting
together the reinforcing members 20 and the sheet 12 or loss of
effectiveness of other forms of connection between these components
may not be a concern.
[0055] The reinforcing members 20 may be attached in any
combination to selected areas of the top side 14 and the underside
16 of the decking panel. The reinforcing members 20 would normally
be kept away from areas on the top side 14 that develop known,
higher levels of mechanical resistance once the concrete has
hardened (for instance, webs with embossments impressed in them).
Importantly, the strength of the longitudinal shear connection
between the reinforcing members 20 and the sheet 12 should be such
that longitudinal shear failure is avoided during the formwork
stage, as described above.
[0056] Reinforcing members 20 can be placed at various discrete
locations around the steel sheet 12. Examples of different
locations are shown in FIGS. 4, 5 and 6.
[0057] Referring particularly to FIG. 5, the reinforcing members 20
are connected to the flanges 40, 42 of the steel deck to increase
the second moment of area about the major horizontal axis and
therefore the flexural stiffness of the decking panel to vertical
loading.
[0058] The moment capacity of critical regions can also be
increased by changing the distribution of longitudinal compressive
bending stresses that cause premature local buckling of the decking
flanges and/or webs--for instance see FIG. 4, which is a case when
this section is in positive bending.
[0059] Profiles that are asymmetric about the major horizontal axis
can be reinforced to improve the balance between the compressive
and tensile capacities of the flanges. An example of this is shown
in FIG. 3, where it can be seen that reinforcing the narrower top
flange 40 increases the balance between the cross-sectional areas
of the top and wider bottom flanges 40, 42.
[0060] Reinforcing the web elements 44 can also improve shear (and
bending) capacity--refer FIG. 6, which can be particularly useful
in internal support regions.
[0061] A wide variety of profile shapes and reinforcing members 20
can be used so as to meet specific design requirements. Examples
are shown in FIGS. 9, 10 and 11.
[0062] Structural steel decking panels constructed according to the
invention provide some or all of the following advantages. [0063]
More efficient structural design by placement of reinforcement
where it has the most effect. This overcomes a fundamental problem
with roll formed steel decks--that the normal thickness of the
sheets is constant around the profile perimeter. [0064] Longer deck
spans or thicker slabs or beams or greater construction loads. This
increases the range of applications in which a particular deck of
maximum sheet thickness can be used in practice. [0065] Improvement
in economy of roll form decks by combining them with cheaper
reinforcing materials such as hot-rolled reinforcing bars or
plates.
[0066] To prevent the concrete from contacting the reinforcing
members 20, the members may be housed in small additional ribs or
longitudinal stiffeners rolled into the steel decking (refer for
example to FIGS. 3 and 9). The additional longitudinal ribs and
reinforcing members may have the same shape to help with their
attachment (for example refer FIG. 9).
[0067] A feature of the invention is that a suitable structural
steel decking panel can be used with or without additional
reinforcement. This improves economy by allowing the use of
additional reinforcement only when it is required. The embodiments
of reinforced closed rib decking panels shown in FIGS. 10 and 11
illustrate this point.
[0068] The applicant carried out an experimental program to
evaluate the performance of the invention. The results of the
program are reported in FIGS. 12 and 13.
[0069] The experimental program was carried out on the embodiment
of the decking panel shown in FIG. 3 (and FIG. 12). The panel
tested comprised a 1.2 mm thick steel sheet 12 and solid 20 mm
square steel bars as the reinforcing members 20. The performance of
the panel was evaluated in relation to non-reinforced panels.
Specifically, the experimental program tested panels having the
same profile but without the reinforcing members. One panel tested
comprised a 1.2 mm thick steel sheet and the other panel tested
comprised a 1.0 mm thick steel sheet. The profiles of these panels
is shown in FIG. 12.
[0070] The panels were simply supported to form a span of 4.2 m
between the supports. The panels were subjected to a loading that
simulated uniform loading of the panels and the mid-span deflection
of the panels and other properties were monitored.
[0071] FIG. 12 is a plot of applied load versus mid-span deflection
for the 3 panels. FIG. 12 also plots the theoretical
load/deflection for each panel--in the case of the decking panel of
the invention, assuming complete interaction between the sheet 12
and the reinforcing members 20. It is evident from FIG. 12 that the
reinforcing members 20 had a significant impact on the flexural
stiffness and moment capacity of the panel and that the connection
between the steel sheet 12 and the reinforcing members 20 resisted
longitudinal shear very effectively as the deflection
increased.
[0072] FIG. 13 is a series of spanning curves for the decking panel
in accordance with the invention. The spanning curves were
generated by imputing measured and calculated data of moment
capacity, vertical shear capacity, and flexural stiffness from the
deflection and similar tests described above into a spanning curve
model. The spanning curves show that the same deck in accordance
with the invention can be used to support wet concrete and
construction loads during the formwork stage of the construction of
a composite slab as a result of the improvements in flexural
stiffness and moment capacity achieved by the reinforcing members
20 and the form of the connection of the members to the steel
sheet. The line marked "X" is for the 1.2 mm decking panel alone,
based on its strength only, which is the absolute maximum
performance the unreinforced sheet can achieve if deflection of the
panel under the weight of wet concrete is ignored. The numbers 130,
etc indicate that the maximum ponding deflection of the concrete is
the span length of the panel divided by 130, etc. It is clear from
FIG. 13 that the performance of the decking panel in accordance
with the invention has been vastly improved by adding the
reinforcing members 20 and that much longer spans are possible
during construction.
[0073] While the present invention has been described in terms of
preferred embodiments in order to facilitate better understanding
of the invention, it should be appreciated that various
modifications can be made without departing from the principles of
the invention. Therefore, the invention should be understood to
include all such modifications within its scope.
* * * * *