AU782222B2 - Improved structural decking - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Application Number: Class Int. Class Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: Applicant: STRAMIT CORPORATION LIMITED Chatswood NSW 2067 AUSTRALIA 'T -er OF\C- PHILLIPS ORMONDE FITZPATRICK 367 Collins Street MELBOURNE VICTORIA 3000 Tel: (03) 9614 1944 Fax: (03) 9614 1867 Attorney Code: PO Address for service in Australia: Complete Specification for the invention entitled: "IMPROVED STRUCTURAL DECKING" Our Ref: IRN 639981 The following statement is a full description of this invention, including the best method of performing it known to applicant: 1 fonms alronncapfonns.doc IMPROVED STRUCTURAL DECKING The present invention relates generally to improvements in structural decking for formwork, and more specifically to decking made from profiled steel on which concrete is poured to form a composite slab.

In a composite slab metal decking serves the purpose of formwork to hold the concrete until the latter has set. The decking also serves as tensile reinforcement for the concrete in the formed slab. This form of construction, commonly used to provide flooring between successive levels of a multi-storey building, eliminates or generally reduces the amount of steel reinforcement bar otherwise necessary in concrete slabs formed with temporary formwork.

Typically the profile decking has a basal surface on which the concrete layer is applied, and includes spaced apart stiffening elements which upstand oooo from the basal surface and which are designed to be embedded in the concrete layer. The decking is formed typically from metal sheet and the stiffening 15 elements are produced in the deck profile by a roll forming operation, although other modes of construction may be used such as folding or pressing processes.

The stiffening elements may take the form of ribs which extend along the decking intermediate its ends, or be in the form of upstanding flanges which are S 20 formed along the side margins. The decking may also be profiled to have a combination of ribs and upstanding side margins.

The purpose of the stiffening elements is to strengthen the decking in bending and to also act as internal reinforcement to the composite slab. The bending strength of the decking is critical to its ability to act as formwork prior to curing of the concrete layer and therefore largely determines the thickness of the concrete layer that may be applied to the decking as well as the resulting span lengths of the composite structure.

Incorporating the upstanding side margins of the decking has the additional advantage that they may also be used to interlock the panel with an adjacent panel to form a continuous decking structure as well as provide a stiffening element, thereby obviating the need for separate fasteners at the side regions. In this application, the flange of one side of the panel includes a laterally disposed web which mates with a complementary shaped web located IRN639981- improved structural decking.doe at the other side of a like profiled panel. The interlocked webs of adjacent panels are securely held together on pouring of the concrete layer as they become fully embedded in that layer. A profile of this type is used by the applicant in its CONDECK HP decking.

An aim of the present invention is to provide improvements to the performance of a profiled deck. A particular aim of the invention is to provide a profiled deck which has enhanced performance and is able to accommodate differing design loading thereby improving its functionality and ease of use.

Accordingly, the present invention provides a decking system for use as concrete formwork, the system including a profiled panel, and a reinforcing element, the profiled panel including a basal surface operative to act as formwork for supporting a layer of concrete applied thereto, and at least one upstanding portion upstanding from said basal surface, the profiled panel being :oo•.operative to be interconnected with a like profiled panel with the upstanding portion forming at least part of a stiffening element of said system, and wherein the reinforcing element is operative to be connected to said stiffening element which when connected, improves the load carrying capacity of said deck.

An advantage of the present invention is that the reinforcing element of the decking system may be located on selective ones of the stiffening elements 20 of the profiled panel and/or discrete parts of the individual stiffening elements.

In this way, the inclusion of the reinforcing element may be used to increase the loading that can be applied to the decking. Further by incorporating the reinforcing elements on the existing stiffening elements, the increase in the localised loading performance of the decking system is improved both under construction loading where the concrete is in an unhardened state, as well as under live loading where the deck and the hardened concrete act as a composite slab.

The decking system of the present invention has particular application where the profiled panel includes upstanding side margins such as that used in the applicant's profile CONDECK HP and other commercially available profiles.

In that application, the interconnection of one upstand with a upstand of an adjacent like panel, enables the upstands to operate as a single unit and therefore may be regarded as a single stiffening element in the resulting decking.

IRN639981- improved stnlctural decking.doc 3 In that application, the stiffening element formed by the interconnected side margins includes an upstanding flange and a laterally disposed web.

When connected, the reinforcing element functions with the stiffening element as a compound structure. In a particularly preferred form of the invention, which is applicable where the stiffening element is non-symmetrical, the reinforcing element is specifically shaped so that the compound structure has a geometry which minimises torsional loading induced on the stiffening element.

In this application, the reinforcing element may increase the performance of the decking by both reducing the loading on the stiffening element and, if so designed, increase the actual stiffness or strength of the stiffening element.

In a particularly preferred form, the reinforcing element includes a body section operative to be connected to the stiffening element, and a web which extends outwardly from the body section, wherein when the body section is connected to the stiffening element, the web extends outwardly from the 15 stiffening element in a direction opposite to the laterally disposed web of the stiffening element.

The stiffening element in the decking of the above type is asymmetric by virtue of its laterally disposed web. The web is included primarily to allow for interconnection of the profiled panel with an adjacent panel and to "key" the 20 panel into the concrete to thereby prevent it separating from the concrete once it has cured. The web also provides tensile reinforcement in the composite slab o" and in fact, may constitute the reinforcement required for a fire rated composite slab, where the metal reinforcement of the exposed parts of the deck is discounted.

Under construction, the profiled deck is laid over supports and the concrete layer is applied to the upper surface. The weight of the concrete applies a loading across the decking which acts in effect as a shallow beam. In particular, over the supports, the web of the stiffening elements is placed in tension. By virtue of it's asymmetric configuration, these tensile forces induce a torsional loading to the stiffening element which biases it to collapse by rotation about the junction between the stiffening element and the basal surface of the panel.

Incorporation of the reinforcing element with the web which opposes the laterally disposed web of the stiffening element, is designed to create a new 1 RN639981- improved structural decking.doc 4 geometry which will minimise the torsional loading induced on the stiffening element. By reducing this torsional loading, the profile is able to carry greater loading across the deck.

To minimise this torsional loading induced on the stiffening element, preferably the geometry of the compound structure has a shear centre which is more aligned with the line of action of the resulting lateral load acting through the stiffening element which is induced by loading of the deck. This line of action is generally very close to or aligned with the stiffening element flange.

The shear centre is in fact the centre of the internal shear force system acting in the decking. In a beam having asymmetric cross section, the shear centre will fall on its axis of symmetry. In a preferred form of the invention, the reinforcing element is configured so that when connected to the stiffening element, the geometry of the resulting compound structure is designed to be roughly symmetrical with its axis of symmetry aligned with the flange of the 15 stiffening element.

The body section of the reinforcing element may take various forms. In its simplest form, the body section may incorporate a shortened flange which is designed to extend parallel to the flange of the stiffening element and which is typically secured to the flange of the stiffening element by fasteners such as tek screws or the like. In another form, the body section includes a flange which is designed to extend parallel to the flange of the stiffening element and a base part which is designed to abut the basal surface of the profiled panel. Again typically the reinforcing element is secured to the profiled panel by fasteners such as tek screws or the like. In one form, fasteners are applied both through the flanges of the web and stiffening element and also through the base part of the stiffening element and into the basal surface of the profiled panel. The benefit of this latter arrangement is that the reinforcing element also improves the rigidity of the stiffening element flange thereby further improving the capacity to resist torsional loading.

In a preferred form, the web of the reinforcing element is designed to be generally aligned with the web of the stiffening element. However, it is to be appreciated that the web of the reinforcing elements may extend outwardly at a height which is different to that of the stiffening element web. Under this latter configuration, the reinforcing element still has the facility to reduce the torsional IRN639981- improved structural decking.doc loading induced on the stiffening element by the change of geometry of the resulting compound structure.

In an alternative form, the profiled panel may include stiffening elements having other configurations such as intermediate ribs or the like. In that application, the reinforcing element may still be beneficially incorporated to provide flexibility in the design loading parameters of the panel. When used in profiled panels of this type, preferably the reinforcing element is in the form of a channel section which locates over the apical portion of the rib thereby increasing the stiffness and strength of the rib.

In a further aspect, the present invention provides a reinforcing element for use on a decking system, the decking system including a basal surface °i operative to act as formwork for supporting a layer of concrete applied thereto, and at least one stiffening element upstanding from said basal surface, the stiffening element including an upstanding flange and a laterally disposed web, 15 wherein the reinforcing element includes a body portion which is operative to be connected to said upstanding flange, and a web which extends outwardly from said body section.

In yet a further aspect, the present invention relates to a method of installing formwork decking, the method including the steps of: providing a decking surface having a basal surface operative to act as formwork for supporting a layer of a concrete applied thereto, and at least one stiffening element which is operative to extend upwardly from said basal surface; and (ii) connecting a reinforcing element to said stiffening element along discrete sections of said stiffening element.

In a preferred form, connection of the reinforcing element to the stiffening element reduces the torsional loading induced on the stiffening element at the discrete sections under construction loads.

It will be convenient to hereinafter describe embodiments of the present invention with reference to the accompanying drawings. It is to be appreciated that the particularity of the drawings and the related description is to be understood as not superceding the generality of the preceding description of the invention.

In the drawings: I RN639981- improved structural decking.dnc 6 Figure 1 is a side elevation of a decking for a composite slab comprising inter-connecting profile panels; Figure 2 is the decking of Figure 1 including a reinforcing element; Figures 3A to 3D are alternative forms of the reinforcing elements; Figure 4A to 4C are schematic plan views using the decking of Figure 2; Figure 5 is an alternative form of decking to that illustrated in Figure 1; and Figure 6 is a reinforcing element for use with the decking of Figure Turning firstly to Figure 1, a metal decking 10 is disclosed which is used in composite slab construction. The composite slab incorporates a layer of concrete which is poured on to the decking 10. In this way the decking 10 is designed to act as formwork to hold the concrete until the latter has set and also to act as tensile reinforcement once the concrete is in its formed state. The profile illustrated in Figure 1 is sold by the applicant under the name CONDECK

HP.

The decking 10 consists of plurality of laterally adjacent panels 11 of ":0•"similar form. Each panel 11 at respective sides has an upturned male side margin 12 and a female side margin 13. The arrangement is such that the successive panels 11 interfit at adjacent sides. Considering each interfitting S...i margin 12, 13 as a unit 14, the latter is provided to act as a stiffening element which increases the strength of the decking 10 in bending and also provides internal reinforcement to the composite slab construction. The stiffening bases' element 14 includes an upstanding flange 14A, and at an upper edge of that flange, a laterally disposed web 14B having an outer downturned lip 14C. The panels 11 include a basal surface 15 intermediate the side margins 12, 13 which provide the formwork surface for the concrete slab (not shown).

Now turning to Figure 2, a reinforcing element 16 is incorporated into the decking 10 and is used in conjunction with stiffening element 14. The purpose of the reinforcing element is to increase the strength of the stiffening element in sections of the decking where it may be required in view of the anticipated loading on the decking.

The reinforcing element 16 is shaped to complement the shape of the stiffening element 14 and includes a base part 17 and in a similar manner to the stiffening element 14, an upstanding flange 18 and a laterally disposed web 19.

IRN639981- improved stnlctlra! deckingd-c 7 In the version of Figure 2, the reinforcing element 16 is cut from the CONDEK HP sheet and therefore also includes a downturned lip The reinforcing element 16 is coupled to the stiffening element 14 and is positioned so that its web extends in the opposite direction to the web 14B of the stiffening element 14. The reinforcing element 16 is secured by fasteners 21, 22, such as tek screws or the like. One of the fastener 21 couples the flange 14A web of the stiffening element 14 to the flange 18 of the reinforcing element 16 whereas another fastener 22 secures the base part 17 of the reinforcing element to the basal surface 15 or the decking The connecting of the reinforcing element 16 to the stiffening element 4 significantly improves the performance of decking 10. The reinforcing element provides additional internal steel to the resulting composite slab thereby improving the strength of the composite slab in bending under live loading. The reinforcing element 16 also improves the performance of the deck whilst under construction load (ie prior to setting of the concrete layer) as it enables the decking 10 to accommodate considerably more compressive loading. This operates in two ways. Firstly, the reinforcing element 16 increases the overall stiffness or compressive strength of the stiffening element 14 by virtue of its connection to the stiffening element flange 14A. Secondly, by virtue of its complementary shape, the reinforcing element 16 when coupled to the stiffening element, causes the resulting structure to have a shear centre which is more aligned with the flange 14A. This significantly improves the ability of the stiffening element to accommodate compressive loading as it reduces the amount of torsional loading applied to the stiffening element when the deck is under load.

In construction, the profiled deck is laid over supports and the concrete layer is applied to its upper surface. The weight of the concrete applies a loading across the decking which acts in effect, as a shallow beam. In particular, over the supports, the web 14B of the stiffening elements 14 are placed in tension. By virtue of their asymmetric configuration, these tensile forces induces a torsional loading to the stiffening element which biases it to collapse by rotation about the junction between the stiffening element 14 and the basal surface 15 of the deck. By incorporating the reinforcing element 16 to the stiffening element 14, the resulting compound structure has a different IRN639981- itnpiuvud strucurai decking.doc 8 geometry where the shear centre of the compound structure is more aligned with the flange 14A of the stiffening element. This reduces considerably the torsional loading applied to the stiffening element and provides a much more stable structure. As a result, the decking is able to accommodate greater loading without causing collapse of the stiffening elements.

Figures 3A to 3D illustrate variations of the reinforcing element 16 of Figure 2. In each case, the reinforcing is generally of complementary shape to the stiffening element and therefore improves the performance of the decking in a manner similar to that described above with reference to the arrangement of Figure 2. In the version illustrated in Figure 3A, the reinforcing element 16 has a similar shaped profile as the stiffening element, although in this arrangement it is independently roll formed rather than cut from the CONDECK HP sheet. The version illustrated in Figure 3B, the reinforcing element 16 profile is somewhat different to the profile of the stiffening element 14 although again it operates in a similar manner and in particular provides the counterbalancing moment to the stiffening element under compressive loading.

In the arrangement of Figure 3B the reinforcing element is formed from a simple folding process.

Figures 3C and 3D illustrate different forms of profiled panel 11.

However, in each case, the panel operates in a similar principal to that disclosed in Figure 1. In particular each panel includes the upstanding side margins which interlock to form the stiffening web 14. Similarly, each stiffening web includes the flange 14A and the web 14B. Further in a similar arrangement to that disclosed previously, the reinforcing element 16 is provided to complement the shape of the stiffening element in a manner that produces a compound structure which is designed to reduce the torsional loading applied to the stiffening element when the deck is under load by more closely aligning the shear centre of the compound structure with the flange 14A of the stiffening element 14.

Figures 4A to 4C illustrate schematic views of decking plans incorporating a plurality of the reinforcing element 16. As can be seen, the reinforcing elements are applied only in selected areas where the tensile loading on the stiffening elements are higher by virtue of the loading applied to the decking 10. In Figure 4A, the reinforcing is used where there are variable IRN639981- improved structural decking.doc 9 span lengths with the reinforcing element being incorporated in sections of longer span. In figure 4B, the reinforcing elements are used in the end spans which are subject to higher loading, and in Figure 4C the reinforcing elements are used in sections where there is increasing slab thickness to accommodate for heavier loading zones.

Figures 5 and 6 illustrate a further alternative to the decking 10. In this arrangement, the decking includes individual profiled panels which incorporate trapisoidal ribs 51 and troughs 52. Whilst the figures only illustrate a single panel, typically the decking is made up from a plurality of similar panels which are interfitted at adjacent sides.

In the embodiment of Figure 6, the reinforcing element 53 is in the form of a channel section which fits over the trapisoidal rib and is secured in place by a series of fasteners 54, 55. In alternative form not shown, the reinforcing element 53 may be held in place through other arrangements such as by interengaging the outer surface of the stiffening element to which it is connected. In that form, preferably the side walls of the stiffening rib includes re-entrant :*portions, and the reinforcing element includes an inturned portion which engages these re-entrant portions to provide a snap fit connection between the reinforcing element and the stiffening element.

In a similar manner as to the previous embodiment, the reinforcing element 53 is designed to be used to increase the structural properties of the decking at selected points. Further, the reinforcing element increases the performance of the resulting composite slab by virtue of increasing the internal reinforcement in the composite slab. In addition, the reinforcing element increases the stiffness of the individual ribs thereby increasing the construction loading which may be applied to those ribs.

Accordingly, the present invention provides a decking system for composite slab construction which provides improved performance over existing systems. In particular, the selective use of the reinforcing element allows the decking to be designed with variable strength characteristics. Further, in preferred applications, the reinforcing element changes the geometry of the resulting compound structure to minimise torsional loading on the stiffening element thereby improving the performance of the deck under construction loading induced on the deck.

IRN639981- improved structural decking.doc Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the construction and arrangements of parts previously described without departing from the spirit or ambit of the invention.

1RN63991i- imiipruved structural decking.doc 11

Claims (18)

1. A decking system for use as concrete formwork, the system including a profiled panel, and a reinforcing element, the profiled panel including a basal surface operative to act as formwork for supporting a layer of concrete applied thereto, and at least one upstanding portion upstanding from said basal surface, the profiled panel being operative to be interconnected with a like profiled panel with the upstanding portion forming at least part of a stiffening element of said system, and wherein the reinforcing element is operative to be connected to said stiffening element which when connected, improves the load carrying capacity of said deck.

2. A decking system according to claim 1, wherein the profiled panel includes upstanding portions at each of its side margins, the upstanding side margins of the panel being operative to be interconnected with respective opposite ones of the side margins of a like panel, and wherein each of said interconnected upstanding side margins form a said stiffening element.

3. A decking system according to either claim 1 or 2, wherein the stiffening element is non symmetric and the reinforcing element is shaped so that the compound structure formed on connection of said reinforcing element and said stiffening element has a geometry that reduces torsional loading induced on the stiffening element under construction loads where a layer of a concrete is applied to said decking system.

4. A decking system according to claim 3, wherein as compared to the stiffening element, the geometry of the compound structure has a shear centre which is more aligned with the line of action of the resulting lateral load acting through the stiffening element induced by the construction loads.

A decking system according to any preceding claim, wherein the reinforcing element is operative to increase the strength and stiffness of said stiffening element.

6. A decking system according to any preceding claim, wherein the stiffening element includes an upstanding flange and a laterally disposed web, and wherein the reinforcing element includes a body section operative to be connected to the stiffening element, and a web which extends outwardly from the body section, and wherein when the reinforcing element is connected to the IRN639981- improved structural dccking.dcc stiffening element, the reinforcing element web extends outwardly in a direction opposite to the laterally disposed web of the stiffening element.

7. A decking system according to claim 6, wherein the body section of the reinforcing element includes a flange which is designed to extend generally parallel to the flange of the stiffening element, and a base part which is designed to abut the basal surface of the profiled panel.

8. A decking system according to claim 7, wherein the reinforcing element is connected to the stiffening element by a first fastener connecting the flange of the body section to the flange of the stiffening element, and a second fastener connecting the base part to the basal surface of the profiled panel.

9. A decking system according to any one of claims 6 to 8, wherein the web of the reinforcing element is designed to be generally aligned with the web of the stiffening element.

10. A decking system according to any preceding claim, wherein the stiffening element is in the form of a rib located intermediate the side margins of the profiled panel, and wherein the reinforcing element is operative to locate S-over the apical portion of the rib to thereby increase the compressive strength of the rib.

11. A reinforcing element when used in a decking system according to any preceding claim.

12. A reinforcing element for use on a decking system, the decking system including a basal surface operative to act as formwork for supporting a layer of concrete applied thereto, and at least one stiffening element upstanding from said basal surface, the stiffening element including an upstanding flange and a laterally disposed web, wherein the reinforcing element includes a body portion which is operative to be connected to said upstanding flange, and a web which extends outwardly from said body section.

13. A method of installing formwork decking, the method including the steps of: providing a decking surface having a basal surface operative to act as formwork for supporting a layer of a concrete applied thereto, and at least one stiffening element which is operative to extend upwardly from said basal surface; and IRN63991- improved structural decking.doc 13 (ii) connecting a reinforcing element to said stiffening element along discrete sections of said stiffening element.

14. A method according to claim 13, urther including the step of reducing the torsional loading induced on said stiffening element at said discrete sections under construction loads where concrete is applied to said decking system by connection of said reinforcing element to said decking element.

A method according to claim 14, where the torsional loading induced on the stiffening element is reduced by forming a compound structure with the connection of the reinforcing element to said stiffening element which has a shear centre which is more aligned with the line of action of the resulting lateral load acting through the stiffening element induced under construction loads.

16. A decking system substantially as herein described with reference to the accompanying drawings. o

17. A reinforcing element substantially as herein described with reference to the accompanying drawings.

18. A method of installing a decking system substantially as herein described with reference to the accompanying drawings. DATED: 5 April 2001 PHILLIPS ORMONDE FITZPATRICK Attorneys for STRAMIT CORPORATION LIMITED il IRN639981- improved structural decking.doc 14