WO1998057010A1

WO1998057010A1 - Staircase form

Info

Publication number: WO1998057010A1
Application number: PCT/AU1998/000446
Authority: WO
Inventors: Margaret Burnside; Timothy Michael Peters
Original assignee: Stairform Designs Pty. Ltd.
Priority date: 1997-06-11
Filing date: 1998-06-11
Publication date: 1998-12-17

Abstract

A staircase form includes two or more stringers (12, 13), and, extending between the stringers, a plurality of risers (16). A network (20) of reinforcement rod, bar or plate for concrete is disposed below the risers. This network includes at least one elongate element (22) extending longitudinally of the form below the risers, and successive loops (26) linking the risers to the elongate element(s). The loops (26) are fixed to the rears of the risers (16), and also to the elongate element(s) (22) at respective locations coincident with or in proximity to the corresponding fixing locations of the next successive loops.

Description

STAIRCASE FORM

Field of the Invention

This invention relates generally to staircase forms and in particular provides a staircase form which may be utilised for the in situ construction of a concrete staircase without an underlying supporting framework.

Background Art

A known approach to the construction of stairs in larger buildings, especially high rise office buildings, is to install a prefabricated steel staircase form and then to cast the staircase in situ by pouring concrete into the form.

Examples of such forms are to be found in Australian registered designs 88285, 88308 and 132042, and in British registered design 1009616. Such staircase forms typically include a pair of stringer plates linked by a succession of risers. The form may be wholly open or may include a soffitt plate to support the poured concrete. With either of these alternatives, the staircase form is conventionally mounted on an underlying framework to provide the necessary structural support for the form and the concrete. The need to pre-erect this framework, normally made up from lengths of timber, increases both the materials and labor costs of the installation. A further contributor to cost is the conventional practice of drilling the concrete after it is set, to fix hand-rail mounting brackets.

Disclosure of the Invention

It is an object of the invention to provide a staircase form which at least in part alleviates one or more of the aforementioned cost disadvantages. This object is met by providing a novel reinforcement framework in a staircase form which allows the staircase to be in cast in situ without need for the conventional underlying support framework. It is known to provide reinforcement rods in staircase forms but these have been conventional grids laid adjacent the soffitt plate and were insufficient to avoid the need for a backing framework. The invention is a significant advance on this conventional practice.

The invention accordingly provides a staircase form including two or more stringers, and, extending between the stringers, a plurality of risers, wherein a network of reinforcement rod, bar or plate for concrete is disposed below the risers, and wherein the network includes at least one elongate element extending longitudinally of the form below the risers, and successive loops linking the risers to the elongate element(s), which loops are fixed to the rears of the risers, and also to said elongate element(s) at respective locations coincident with or in proximity to the corresponding fixing locations of the next successive loops.

Said loops are preferably inverted angled elements, and preferably consist of two substantially straight arms. One of the arms is preferably substantially parallel to but extends transversely of the respective riser to which the respective loop is fixed. Preferably, this arm is fixed, e.g. by welding, to the riser at at least two spaced locations.

The staircase form preferably further includes soffitt means arranged so that the network of reinforcement rod including said at least one elongate element is disposed between the risers and the soffitt means. In this case, the elongate element is displaced sufficiently clear of the soffitt means for freshly poured concrete to flow under the element.

Preferably, the respective ends of each loop are fixed to the soffitt means.

Advantageously, the successive loops are arranged substantially in a one or more rows and essentially these rows define respective planes which lie at spaced intervals between and parallel to the stringers substantially at right angles to the soffitt means. For example, for a staircase of about one metre width, there are preferably three or four such rows or planes of loops. Preferably, the successive loops overlap adjacent and/or between the soffitt means and the elongate element.

The soffitt means is preferably a soffitt plate substantially forming a floor for the space between the stringers. Alternatively, the soffitt means may comprise e.g. multiple spaced strips extending transversely or longitudinally between the stringers.

Where there is a plurality of said elongate elements extending longitudinally of the form below the risers, these elements are preferably linked by a plurality of longitudinally spaced cross members. These can be fixed to the respective longitudinally extending elongate elements, e.g. by being welded.

In an embodiment, the staircase form includes two sets of elongate elements. In this embodiment, the elongate elements previously described form a set of lower elongate elements and the staircase form includes an additional set of upper elongate elements. The upper elongate elements extend longitudinally of the form and are positioned below the risers and above the lower elongate elements. The upper elongate elements may be connected to the loops in the same manner as the lower elongate elements. Each of the upper elongate elements is preferably formed as a steel rod that is continuous in length, thereby connecting successive loops. Alternatively, the upper elongate elements may be formed by short pieces of rod in the upper half of each loop connected to each leg of the said loop.

Preferably, one or both of the stringers is provided internally with a hand-rail mounting bracket secured to the stringers on the soffitt side of the plane joining the outer or front edge of a riser to the inner or rear edge of the riser above.

Preferably, the form is such as to comprise a truss able to support a reinforced concrete stairway without supporting structural framework below the form. For some applications, the form may further include, at one or each end, projecting structure for linking the form to a landing support. This structure is preferably of a load bearing design adapted to cantilever the form from the landing support.

Brief Description of the Drawings

The invention will be further described , by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is an isometric view of a staircase form according to an embodiment of the invention, the form being a truss for enclosing a reinforced concrete stairway cast in situ in the form;

Figure 2 is a view from below the form, better showing the upper end;

Figure 3 is a representative fragmentary cross-section in a plane between and parallel to the stringer plates;

Figure 4 is a cross-section of an alternative design of riser; Figure 5 is a view similar to Figure 1 of a modified staircase form having an additional upper set of longitudinal rods and projecting structure at its lower and for linking the form to a landing support beam; and

Figure 6 is a view similar to Figure 3 of the staircase form of Figure 5.

Preferred Embodiments

The staircase form 10 illustrated in Figures 1 to 4 is constructed from steel plate and steel rod and is designed as a truss for enclosing and supporting a reinforced concrete staircase cast in situ in the form.

Form 10 includes a pair of spaced parallel stringer plates 12,13 linked at their longitudinal rear edges by a soffitt plate 14, and at spaced intervals above soffitt plate 14 by multiple risers 16. Extending the length of the staircase between soffitt plate 14 and risers 16 is a reinforcement network 20 of steel rod detailed further below.

Soffitt plate 14 terminates at top and bottom at respective bent landing plates

15a, 15b with strengthening angle beams 19 at each side. It will be appreciated that stringer plates 12,13, soffitt plate 14, risers 16 and landing plates 15a,15b would typically be formed from similar steel plate stock, e.g. of gauge 0.5 to 5mm. A particularly convenient gauge is 1.9 to 3.0 mm. The plates are welded together at their edge interfaces and to the extent of these components the form is of substantially known construction. The gauge may vary with the location and size of the staircase to be installed.

The profile of risers 16 is uniform and is best seen in Figure 3. They are substantially planar save for oppositely overturned outer and inner edge lips 17a, 17b. Outer edge lip 17a lies in a transverse plane parallel to the soffitt plate and the top edges of stringer plates 12, but displaced a little from the latter. Inner edge lip 17b is similarly inclined but located about midway between the plane of outer edge lip 17a and soffitt plate 14. When the form is in its correct orientation, as depicted in Figure 3, the free edge of lip 17b lies substantially horizontally to the rear of the free edge lip 17a of the next riser below in the staircase. This plane is marked at 25 in Figure 3 and will be the level of the successive steps in the eventual staircase. The main plane of each riser can be tilted back nearly 20° to partially overlie the adjacent step.

An alternative riser design 16' is shown in Figure 4. In this case, edge lips 17a', 17b' are differently profiled, while outer edge lip 17a' carries a stainless steel non- slip step plate 18. Plate 18 is in the general form of an inverted channel, which embraces and is welded to edge lip 17a'.

Reinforcement network 20 includes three laterally spaced longitudinally extending rods 22 linked transversely by longitudinally spaced cross rods 24. Rods 24 lie on top of and are welded to rods 22 and the resultant grid structure is disposed sufficiently clear of soffitt plate 14 for freshly poured concrete to flow under, and fill the space between, the rods 22,24 and the soffitt plate. The longitudinally extending rods 22 each support an aligned row 27 of successive loops 26. Each loop consists of an angled rod bent at an off-centre position 28 to define two straight arms 30,32 that depend from bend 28 and are welded at their free ends 31,33 onto the face of soffitt plate 14. Each angled rod or loop 26 lies in a plane that extends substantially at right angles from soffitt plate 14. The included angle at bend 28 is of the order of 60°.

The arrangement is such that there is one angled rod or loop 26 in each row 27 for each riser and the shorter arm 32 of each angled rod abuts and is parallel to the rear of the respective riser. This arm 32 is welded to the rear face of the riser at two well spaced positions 36,37 : the position 36 is nearer to outer edge lip 17a than to the inner edge lip

17b, and the bend 28 in loop 26 lies under and is spaced from outer edge lip 17a.

The dimensions are such that loops or angled rods 26 slightly overlap, in that the longer arm 30 of each loop just overlaps the shorter arm 32 of the next loop above, slightly out from soffitt plate 14. The rods are not fixed together at this cross-over point 38 but would typically be substantially in contact. The exact distance of the cross-over point 38 from soffitt plate 14 is not critical, so as not to impose excessive tolerance requirements on manufacture, but would typically be located between the longitudinally extending rod 22 and the soffitt plate 14. Angled rods 26 are not welded to each other at their cross-over point 38 but they are welded at both legs to longitudinally extending rod 22 at their respective points of contact or cross-over 40,41.

At the top end of the staircase form, angled rod 26' has its longer arm 30' bent more sharply to lie behind the cut outs 45 which accommodate the upper landing structure.

It will be seen from Figure 3 that the spacing of longitudinally extending rods 22 from soffitt plate 14, referred to earlier, is determined by the positions of weld points 40,41, and that the rows 27 of loops 26 define respective planes which lie at spaced intervals between and parallel to stringer plates 12.

The modified embodiment 10' shown in Figures 5 and 6, in which like integers are indicated by like primed reference numerals, includes an additional set of upper longitudinally extending rods 60. With particular reference to Figure 6, the rods 60 are connected to each of the loops 26' at weld points 62,63 below the risers 16' (just below inner edge lips 17b') and above the existing lower elongate rods 22'. The upper rods 60 enhance the load carrying capacity of the form, thereby resisting deflection when flowing concrete is placed inside the form. The upper rod 60 is shown as a continuous rod extending through successive loops 26. This arrangement provides optimum strength, results in even transfer of load and lessens the need for additional mid-span support beneath the form. Alternatively, however, the rods 60 may be formed as short rods (not shown) that are contained within each loop and do not join successive loops.

In the arrangement shown in Figure 6, the two sets of elongate rods, at respective upper and lower levels (in which the rods are preferably co-planar), substantially strengthens the loops so that it may be possible to decrease some material sizes or quantities, or to increase the concrete load applied to the form.

The modified embodiment 10' of Figures 5 and 6 is also fitted, at its lower end, with projecting structure 70 for linking the form to a landing support beam. Structure 70 is of a load bearing design adapted to cantilever the form from the landing support beam, ie. the only support for structure 70 in situ is a beam under its outer end. To this end, structure 70 includes a soffitt base plate 72 which is welded to and extends from main soffitt plate 14', larger cross-section angle beams 74 at each side edge of base plate 72, and intermediate smaller cross-section angle beams 75. Angle beams 74 are welded to and aligned with the respective stringer plates 12', 13', while angle beams 75 are aligned with and welded (eg. at 60a) to respective pairs of rods 22', 60. The end rows of loops 26' also terminate at a weld at 26a onto the respective beam 75. Angle beams 74 are slotted at 78 to provide a passage for reinforcing bars in a landing slab poured onto the structure 70.

When the illustrated form 10 or 10' is fixed in position in a stair well, concrete may be poured in through the spaces between the risers. This body of freshly poured flowable concrete builds up and is supported by the soffitt plate. The space is sufficiently filled and the concrete trowelled so that it wholly fills the region above the soffitt plate, behind the riser plates 16 and below the aforementioned plane 25. The concrete exposed at these latter planes between the riser edges becomes the steps of the staircase when the concrete sets. As is normal for concrete pour and casting practice, voids must be minimised or preferably eliminated, and flow should be substantially complete about and between all of the reinforcement rods and between the rods and the soffitt plate. The whole structure of the form containing the concrete is self supporting both during curing and subsequently, and does not require an underlying supporting framework. It will be appreciated that the form is thus in the nature of a truss able to define and subsequently provide a reinforced concrete staircase.

It will be appreciated that the exact number of the rows of angled rods or loops 26, 26' and their spacing will be a function of a variety of parameters of the form. Significant parameters include, for example, the gauge of the steel plate employed for the stringer and soffitt plates and for the risers, and the diameter and material of the various rods. As already mentioned, a convenient plate gauge is 1.9mm to 3.0 mm. A convenient rod is 10mm mild steel rod, which has good strength while being relatively easy to bend. With these materials, it is believed that the spacing between the longitudinally extending rods 22, 22' and their associated rows of angled rods 26, 26' is no greater than about 300mm. For an exemplary staircase of 1 metre width, there are three or four rows of angled rods 26 at equal spacings from each other and from the stringer plates of about 250 or 200mm respectively.

The form 10, 10' may also advantageously be fitted with hand-rail mounting brackets 50 positioned so that they are cast in situ by the concrete pour. These are located at spaced locations along one or both of the stringer plates and, for example, the illustrated eight-step form has three along each stringer plate - at top and bottom and one in the middle region. Each bracket (best seen in Figure 3) is a pair of threaded rods 52 carried by a plate 54 by which they are lightly welded to the surface of the stringer plate clearly below a respective step plane 15. Each threaded rod projects through respective apertures in the stringer plate to expose respective threaded studs 52a to which hand-rail posts may be attached. At the interior, threaded rods 52 project substantially further from the stringer plates so as to be cast into the poured concrete. They are sufficiently separated to ensure that concrete flows between them, and the threads further enhance the keying engagement. In an alternative embodiment, soffitt plate 14, which in the above-described embodiment forms a floor for the space between the stringer plates 12,13, is replaced by a number of soffitt strips extending longitudinally or transversely between the stringer plates. For example, the strips may be simply thin strips located under and parallel to the rods 22 and welded to the ends of loops 26. With this embodiment, a timber soffit would need to be built in situ to at least initially support the poured concrete.

Claims

1. A staircase form including two or more stringers, and, extending between the stringers, a plurality of risers, wherein a network of reinforcement rod, bar or plate for concrete is disposed below the risers, and wherein the network includes at least one elongate element extending longitudinally of the form below the risers, and successive loops linking the risers to the elongate element(s), which loops are fixed to the rears of the risers, and also to said elongate element(s) at respective locations coincident with or in proximity to the corresponding fixing locations of the next successive loops.

2. A staircase form according to claim 1 wherein said loops are inverted angled elements.

3. A staircase form according to claim 2 wherein each said angled element consists of two substantially straight arms.

4. A staircase form according to claim 3 wherein one of said arms is substantially parallel to but extends transversely of the respective riser to which the respective loop is fixed.

5. A staircase form according to claim 4 it wherein said one arm is fixed, e.g. by welding, to the riser at at least two spaced locations.

6. A staircase form according to any preceding claim further including soffitt means arranged so that the network of reinforcement rod including said at least one elongate element is disposed between the risers and the soffitt means, said elongate element(s) being displaced sufficiently clear of the soffitt means for freshly poured concrete to flow under the element(s).

7. A staircase form according to claim 6 wherein the respective ends of each said loop are fixed to the soffitt means.

8. A staircase form according to any preceding claim wherein the successive loops are arranged substantially in one or more rows and these rows essentially define respective planes which lie at spaced intervals between and parallel to the stringers substantially at right angles to the soffitt means.

9. A staircase form according to claim 6, 7 or 8 wherein the successive loops overlap adjacent and/or between the soffitt means and the elongate element.

10. A staircase form according to any one of claims 6 to 9 wherein said soffitt means is a soffitt plate substantially forming a floor for the space between the stringers.

11. A staircase form according to any one of claims 6 to 9 wherein said soffitt means comprises multiple spaced strips extending transversely or longitudinally between the stringers.

12. A staircase form according to any preceding claim wherein there is a plurality of said elongate elements extending longitudinally of the form below the risers and these elements are linked by a plurality of longitudinally spaced cross members fixed to the respective longitudinally extending elongate elements.

13. A staircase form according to any preceding claim, including two sets of said elongate elements, including a set of upper elongate elements that extend longitudinally of the form and are positioned below the risers and above the lower elongate elements.

14. A staircase form according to claim 13 wherein each of said upper elongate elements is formed as a steel rod that is continuous in length, thereby connecting successive loops.

15. A staircase form according to claim 13 wherein said upper elongate elements are formed by short pieces of rod in the upper half of each said loop connected to each leg of the loop.

16. A staircase form according to any preceding claim wherein one or both of the said stringers is provided internally with a hand-rail mounting bracket secured to the stringers on the soffitt side of the plane joining the outer or front edge of a riser to the inner or rear edge of the riser above.

17. A staircase form according to any preceding claim wherein said form is such as to comprise a truss able to support a reinforced concrete stairway without supporting structural framework below the form.

18. A staircase form according to any preceding claim further including, at one or each end, projecting structure for linking the form to a landing support.

19. A staircase form according to claim 18 wherein said structure is of a load bearing design adapted to cantilever the form from the landing support.

20. A staircase form according to claim 18 or 19 wherein said structure includes, for the or each said elongate element of the network, a beam aligned with and connected to the respective elongate element.

21. A staircase form according to claim 18, 19 or 20 wherein said structure includes angle beams at each side connected to the respective said stringers.