AU2005201848A1 - A decking sheet - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): ONESTEEL REINFORCING PTY LTD Invention Title: A DECKING SHEET The following statement is a full description of this invention, including the best method of performing it known to me/us: -2- A DECKING SHEET C The present invention relates to decking sheets and to composite slabs that include the decking sheets as part of the construction of the slabs.

00 00 A major, although not the only, end use application of the decking sheets is in the construction of composite slabs that form floors in buildings (which Sterm includes car parks).

Another, although not the only other, end use application of the decking sheets is in the construction of composite slabs that form vertical wall panels.

Decking sheets, which are typically roll-formed from steel strip, can serve a dual function when used in the construction of composite steel/concrete floor slabs spanning between steel or concrete beams.

One function of decking sheets is as structural formwork that supports wet concrete of composite floor slabs until such time that the concrete hardens and develops sufficient compressive strength.

Another function of decking sheets is that the decking sheets can act as main reinforcement by interacting with the concrete that has reached sufficient compressive strength. When decking sheets act as main reinforcement, the decking sheets will normally continue to do so for the remainder of the life of the building.

In general terms, decking sheets include: a pan that includes one, or more than one, lengthwise extending rib, hereinafter H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 3 referred to as an "intermediate rib"; and lap joints on opposed lengthwise extending c sides of the pan to enable adjacent decking O 5 sheets to be positioned in side-by-side overlapping relationship with the lap 00 joints on adjacent sides of adjacent sheets 00 engaged together.

Decking sheets may be manufactured in a range of lengths, typically 2500-9000 mm, and a range of widths, C( typically 250-900 mm.

Decking sheets may be used on a construction site as propped sheets or as unpropped sheets.

In situations where decking sheets are used as propped sheets, typically the spacing between props is in the range of 900-2400 mm corresponding to the spacing between bearer pairs in standard falsework frames.

The present invention provides a decking sheet of the type described above that includes one or more than one of a number of features determined by the applicant in the course of research and development work and is an improvement over currently available decking sheets as a consequence of the feature or features.

One such feature is that the lap joints should provide the main mechanical interlock of the decking sheet and concrete when concrete that forms part of a composite slab with the decking sheet hardens on the decking sheet.

The term "main mechanical interlock" is understood herein to mean that the lap joints provide at least 80% of the total mechanical interlock between the decking sheet and the hardened concrete of the composite H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 4 Sslab.

tPreferably the lap joints provide at least 90% of the mechanical interlock with concrete when concrete of a O 5 composite slab that includes the decking sheet hardens on the decking sheet.

00 00 Another feature is that the lap joints should be relatively shallow, ie small in height. In this I 1 0 connection, it was a surprise to the applicant that relatively shallow lap joints could develop strong c1 mechanical interlock between the decking sheet and concrete in a composite slab to resist longitudinal slip and vertical separation of the decking sheet from the concrete.

Preferably the height of the lap joints above a base plane of the pan is less than 25 mm.

More preferably, the lap joint height is in the range of 10-25 mm.

More preferably, the lap joint height is less than 20 mm.

Another feature is that the lap joints should be an open structure.

Preferably each lap joint includes an open structure in the form of a dovetail profile that includes: a side wall extending upwardly and inwardly from a side edge of the pan at an angle of less than 90 degrees relative to the base plane of the pan, a top flange extending outwardly from an H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 5 upper edge of the side wall, and a flange downturn extending downwardly and inwardly from an outer edge of the top O 5 flange and terminating in an out-turned lip.

00 Preferably each lap joint further includes a 00 plurality of reinforcing dimples or other suitable reinforcing elements formed in the top flange at spaced intervals along the length of the lap joint.

1 Preferably the height of the dimples or other suitable reinforcing elements is greater than 3 mm above a plane of the top flange.

Preferably the width of the lap joint mid-height is less than 15 mm.

More preferably the width of the lap joint midheight is less than 10 mm.

Preferably there is a gap of at least 5 mm between the base plane of the pan and the lowermost part of the flange downturn to ensure that, in use, when the lap joint is positioned in overlapping relationship with the lap joint of an adjacent decking sheet, concrete can flow into the gap.

Other features are that the intermediate rib or ribs should be relatively shallow, ie small in height, and, moreover, be shallower than the height of the lap joints.

Preferably the height of the intermediate rib or ribs is less than 10 mm above the base plane of the pan.

The selection of relatively shallow lap joints H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 6 and shallow intermediate ribs means that the lap joints and intermediate ribs have little or no impact on the performance of shear studs that may be used to connect the composite slab using the decking sheet to an underlying steel support structure.

00 Another feature is that the intermediate rib or 00 ribs should be relatively wide compared to the overall width of the decking sheet to control or prevent local buckling or deformation of the decking sheet which can Soccur when the decking sheet is in compression, for 1 example when propped.

Another feature, although possibly more accurately described as a consequence of a number of the above features, is that the mechanical resistance of the decking sheet in a composite slab is at least 200 kN per sheet length (in m) and per sheet width (in m) for the practical range of sheeting thicknesses, e.g. 0.6 to mm.

Preferably the mechanical resistance is at least 300 kN/m/m.

According to the present invention there is also provided a composite slab that includes a plurality of the above-described decking sheets positioned side-by-side with the lap joints in overlapping relationship and a layer of hardened concrete on the decking sheets.

Preferably the composite slab further includes reinforcement, for example in the form of bars and mesh, embedded in the concrete.

The present invention is described further by way of example with reference to the accompanying drawings, of which: H:\GRM\Keep\Speci\Oneteel\A DECKING SHEET draft.doc 2/05/05 7 SFigure 1 is a transverse section of one embodiment of a decking sheet in accordance with the present invention; and Figure 2 is a transverse section of a composite slab that includes a plurality of the decking sheets shown 00 in Figure 1 in overlapping relationship.

00 The decking sheet 1 shown in Figure 1 is typically roll-formed from steel strip and is 2.5 to 9 m Sin length.

The decking sheet 1 includes a central pan 3 and lap joints 5a and 5b on opposite lengthwise-extending sides of the decking sheet.

In addition, the pan 3 includes two intermediate ribs 7 extending from a base plane X-X of the pan 3 along the length of the decking sheet 1.

The intermediate ribs 7 are parallel to each other and to the lap joints 5a, The lap joints 5a, 5b are dovetail-shaped and are complementary in that, as can best be seen in Figure 2, a lap joint 5b of one decking sheet 1 can fit over and engage a lap joint 5a of an adjacent decking sheet 1. In this context, the lap joint 5b is an overlapping lap joint and the lap joint 5a is an underlapping lap joint.

The lap joint 5b includes a side wall or web 9 that extends upwardly and inwardly from the pan 3 at an angle of less than 90 degrees to the base plane X-X of the pan 3, a top flange 11 that extends outwardly from an upper edge of the side wall 9 parallel to the base plane X-X of the pan 3, and a flange downturn 13 that extends downwardly from an outer edge of the top flange 11.

H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 8 The flange downturn 13 includes an out-turned lower lip 31 that contributes to forming a suitable mechanical interlock with concrete in a composite slab and assists with assembling decking sheets 1 together on a building site to construct a composite slab.

00 00 The lap joint 5b also includes a plurality of dimples 15 embossed on the top flange 11 and spaced apart along the length of the lap joint.

c( The lap joint 5a is generally similar in shape to the lap joint 5b. The main differences are, apart from being opposite handed, that the lap joint 5a does not include the out-turned lower lip 31 and the dimples With reference to Figure 2, the composite slab includes a plurality of the decking sheets 1 shown in Figure 1 in side by side overlapping relationship, a layer of concrete 17 on the decking sheets 1, and reinforcement mesh or bars 19 embedded in the concrete.

The nominal dimensions of the decking sheet 1 are shown in Figure i.

The lap joints 5a, 5b have an overall height of only 20 mm above the base plane X-X of the pan 3 and midheight width of less than 15 mm. The width of the decking sheet 1 is 250 mm between the centre lines of the lap joints 5a, 5b. The height of the two intermediate ribs 7 is 8 mm. The intermediate ribs 7 are both 60 mm wide with a flat central region of the same width.

In overall terms, in comparison with currentlyavailable decking sheets, the heights of the lap joints 5b are very low.

H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 9 The dovetail-shaped lap joints 5a, 5b make it possible to form an essentially leak-proof joint between adjacent decking sheets 1 that can simply be assembled by c fitting one decking sheet 1 down onto another decking sheet 1 without having to rotate the decking sheet 1 about its longitudinal axis.

00 00 The out-turned lip 13 of the lap joint 5b also makes assembly of adjacent decking sheets 1 straightforward, even when the decking sheets 1 are of a maximum length.

The shallow, ie small in height, open dovetailshaped lap joints 5a, 5b have a re-entrant shape that keys the decking sheets 1 into a concrete underside of the composite slab shown in Figure 2, thus preventing vertical separation from the concrete and making the decking sheet 1 suitable for use in the longest propped spans possible in steel-frame and concrete-frame buildings.

The decking sheets 1 in the composite slab develop strong, ductile mechanical resistance with concrete to resist longitudinal slip, allowing the decking sheets to be used effectively as main tensile reinforcement in the soffit of the composite slab.

The shallow lap joints 5a, 5b also mean that there is minimal intrusion of the decking sheets 1 into two-way reinforced concrete and prestressed concrete slabs. Thus, it is possible to position reinforcement lower in the slab and maximise concrete cover above the reinforcement. This is an important issue particularly in situations where the composite slabs are exposed to a corrosive environment and it is important to minimise contact of the corrosive environment with the reinforcement.

H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 10 The flat central region of the pan 3 of the decking sheet 1 between the intermediate ribs 7 is 60 mm wide, making it ideally suited to welding standard 19 mm diameter stud shear connectors (not shown) through the decking sheets 1 on site.

The design of the decking sheet 1 means that the studs may be treated as if in a solid concrete slab when determining their design shear capacity. Thus, the maximum possible strength is obtainable without detrimental effects of rib punch-through failure.

Due to the low height of the intermediate ribs 7, horizontal Type 4 longitudinal shear surfaces arising due to possible rib-shearing failure of concrete ribs do not have to be reinforced.

Many modifications may be made to the embodiment of the decking sheet described above without departing from the spirit and scope of the present invention.

H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05

Claims (19)

1. A decking sheet including: O 5 a pan that includes one, or more than one, lengthwise extending intermediate rib; and 00 00 lap joints on opposed lengthwise extending sides of the pan to enable adjacent decking sheets to be positioned in side-by-side overlapping relationship with the lap C( joints on adjacent sides of adjacent sheets engaged together.

2. The decking sheet defined in claim 1 wherein the lap joints provide the main mechanical interlock, as described herein, of the decking sheet and concrete when concrete that forms part of a composite slab with the decking sheet hardens on the decking sheet.

3. The decking sheet defined in claim 2 wherein the lap joints provide at least 90% of the mechanical interlock of the decking sheet and concrete when concrete that forms part of the composite slab with the decking sheet hardens on the decking sheet.

4. The decking sheet defined in any one of the preceding claims wherein the lap joints are relatively shallow, ie small in height.

The decking sheet defined in any one of the preceding claims wherein the height of the lap joints above a base plane of the pan is less than 25 mm.

6. The decking sheet defined in claim 5 wherein the lap joint height is in the range of 10-25 mm. H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 12

7. The decking sheet defined in claim 5 or claim 6 wherein the lap joint height is less than 20 mm.

8. The decking sheet defined in any one of the preceding claims wherein the lap joints are an open structure. 00 00

9. The decking sheet defined in any one of the preceding claims wherein each lap joint includes an open structure in the form of a dovetail profile that includes: c a side wall extending upwardly and inwardly from a side edge of the pan at an angle of less than 90 degrees relative to the base plane of the pan, a top flange extending outwardly from an upper edge of the side wall, and a flange downturn extending downwardly and inwardly from an outer edge of the top flange and terminating in an out-turned lip.

The decking sheet defined in claim 9 wherein each lap joint further includes a plurality of reinforcing dimples or other suitable reinforcing elements formed in the top flange at spaced intervals along the length of the lap joint.

11. The decking sheet defined in claim 10 wherein the height of the dimples or other suitable reinforcing elements is greater than 3 mm above a plane of the top flange.

12. The decking sheet defined in any one of claims 9 to 11 wherein the width of the lap joint mid-height is less than 15 mm. H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 13

13. The decking sheet defined in any one of claims 9 to 12 wherein there is a gap of at least 5 mm between the base plane of the pan and the lowermost part of the flange downturn to ensure that, in use, when the lap joint is positioned in overlapping relationship with the lap joint 00 of an adjacent decking sheet, concrete can flow into the 00 gap. 1 0

14. The decking sheet defined in any one of the Spreceding claims wherein the intermediate rib or ribs are C be relatively shallow, ie small in height, and/or (b) are shallower that the height of the lap joints.

15. The decking sheet defined in any one of the preceding claims wherein the height of the intermediate rib or ribs is less than 10 mm above the base plane of the pan.

16. The decking sheet defined in any one of the preceding claims wherein the width of the intermediate rib or ribs is wide compared to the overall width of the decking sheet to control or prevent local buckling or deformation of the decking sheet which can occur when the decking sheet is in compression, for example when propped.

17. The decking sheet defined in any one of the preceding claims wherein the mechanical resistance of the decking sheet in a composite slab is at least 200 kN per sheet length (in m) and per sheet width (in m).

18. A composite slab that includes a plurality of the decking sheet defined in any one of the preceding claims positioned side-by-side with the lap joints of adjacent decking sheets being in overlapping relationship and a layer of hardened concrete on the decking sheets. H:\GRM\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05 14

19. The composite slab defined in claim 18 includes reinforcement, for example in the form of bars and mesh, embedded in the concrete. 00 00 H:\GRl4\Keep\Speci\OneSteel\A DECKING SHEET draft.doc 2/05/05