EP0646683A1

EP0646683A1 - Structural building components

Info

Publication number: EP0646683A1
Application number: EP94630055A
Authority: EP
Inventors: Aloth Usher Stratford
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-09-21
Filing date: 1994-09-21
Publication date: 1995-04-05

Abstract

Combination of prefabricated, preferably pre-cast concrete stringers (12) and treads (13) which can be employed in any particular application to provide either a staircase of any required inclination, a horizontal walkway or a ramp of a required inclination. In all these applications the same standardised stringers (12) and treads (13) can be effectively used. Stanchions can be added as required. Further embodiments can be used for providing ladders and providing seating for grand stands or theatres.

Description

BACKGROUND OF THE INVENTION

Field of the Inventon

This invention lies in the field of construction and one embodiment of the invention, for example, relates to a stringer and tread combination for use in the construction of a staircase, ramp or walkway. The scope of the invention extends to the stringer and the tread and to a method of establishing a staircase, ramp or a walkway.
Another embodiment of invention, however, is also useful in creating seating structures, in particular which are applicable for the manufacture of grand stands or seating arrangement for theatres, both open air and indoor although primarily the former.
The concept of the invention can be further extended to the application of creating ladders or very steep staircases or step ways. The steepest staircase allowed by official building regulations is inclined at approximately 40° to the horizontal and at angles of inclination greater than 40° the structure can conveniently be referred to either as a very steep staircase or preferably referred to as a ladder.
This invention provides structural building components which may be precast and applied in all of these areas.

Survey of the Art

Staircases present many on-site problems for the builder. Floor-to-floor heights vary as do riser and tread dimensions. Typically, skilled carpenters set out and build the shuttering with extensive propping and specially designed reinforcing being required before the concrete is poured. Not only is space needed for storing reinforcing and shuttering material but concrete spills resulting from bleeding and kicking shuttering and careless barrow-handling add to the general mess and congestion in the very place where easy access to upper floors would enhance efficiency and project completion.
Proposals for prefabricated staircases have been made and examples can be found in the French Patent 90 10433, Publication number 2665920 and United States Patent 3986579.
The former patent describes a stringer and tread construction for a staircase in which the stringers have a substantially conventional stepped construction for supporting a tread on each step characterised by a radius of curvature on the upper surface of each step matched by a similar radius of curvature on the underneath of each tread by which only a very limited amount of adjustment of the tread so as to be perfectly level can be achieved. It is apparent from the drawings that the teaching of the French patent is confined to the idea that only limited adjustment of the treads for the purpose of levelling them is facilitated by the invention.
Rather similarly the U.S. patent also teaches only the possibility for accurately levelling the steps at the job site after the stringers have been installed. Angular rotation is taught to be quite limited as is shown in the view of figure 3 where a bolt 8 must move within a slotted hole 41 of limited dimension.

SUMMARY OF THE INVENTION

By contrast the present invention has the object that the same stringers and treads can be used to provide not only a staircase of any angle of inclination but even down to horizontal, that is to serve as a walkway and all other angles between horizontal and normal maximum for a staircase of about 40° inclination. The system can also be used to produce ramps, that is providing a smooth surface that rises on an incline.
Special embodiments of the invention can be extended to provide also very steep staircases or ladders.
This underlying principle of the invention can also be applied to provide seating ramps for theatres and stadiums.
In accordance with the present invention there is provided a stringer and tread combination in which the stringer is lengthwise provided with successive integrally formed scallops each of which has a lengthwise shape conforming to the arc of a circle each of which scallops can accommodate at least part of an underside of a tread which underside has a co-acting shape to that of the scallops.
By "integrally" it is meant that the scallops and the stringer form one component in that the scallops have not been separately added to the stringer.
It is a characteristic of this invention that each scallop begins and ends on the same longitudinal line of the stringer, or substantially so.
The transverse shape of each scallop may be linear.
It is an important feature of the invention that the same stringer and tread can be used in the manufacture of a stairway, walkway and ramp.
Generally two stringers will support a plurality of treads; in an embodiment of the invention in which the scallops are provided in the top surface of the stringer this allows a single stringer to be employed in the creating of a walkway, ramp or staircase using treads having suitable lengths.
In another embodiment of the invention in which the combination comprises two opposed, spaced apart and generally parallel stringers each stringer on its inner side surface includes scallop shaped corbels for supporting the end portions of the treads. A single projection constituting a plurality of corbels may be provided. Alternatively, a plurality of projections each of which constitute a corbel may be provided.
Preferably, the treads are manufactured of precast concrete, and preferably, the stringers are also manufactured of precast concrete.
Generally, the pitches of the scallops must be constant in order to comply with good practice and official building regulations.
In a preferred embodiment an underside or at least part of the underside of each tread is secured in a scallop by means of glue. Glues which may be employed include those of the epoxy type and of the poly-sulphide type. The applicant has found that the epoxy type of glues provide a rigid joint whereas the poly-sulphide types provide a more flexible joint which is preferred for staircases where only the rear portion of the tread forms an overlap with the stringer and the front portion a cantilever which is stepped on during use and provides a better impact strength. Alternative ways of securing the treads to a stringer are envisaged which includes mechanical keys, for example dove-tail joints and employing bolt and nut connections. The dove-tail joint may include an aluminium extrusion suitably cast into the stringer.
In order to render the treads more resistant to tensile stresses the treads may be provided with reinforcements, for example metal bars cast into the treads, especially in the overlap mentioned above.
To reduce the mass of a stringer it may be provided with holes extending from side to side which holes are open to the outside. The holes also facilitate transportation of the stringers as a means, for example a crowbar or a sling, can be located there through. The holes also facilitate fixing the stringers, e.g. to columns, etc.
The stringer may be provided with inner reinforcements rendering the stringer more resistant to tensile stresses. The reinforcements are preferably located between the holes and the top surface and between the holes and the bottom surface of the stringer. Metal bars cast into the stringers are preferred.
An advantage of the invention is that in the construction of a staircase the scallops allow the stringers to be raked to any suitable angle. After having raked the stringer(s) to the required angle, the treads are located in the scallops and the upper tread surfaces levelled. Alternatively, the treads can be simultaneously raised with the stringers after treads have been rotated and secured in the scallops so that the upper tread surfaces become level when the stringers have been raised.
Preferably, each tread has a generally flat upper surface.
The scallops in the stringers allow for the treads to be secured parallel to the stringer or stringers for creating a walkway or a ramp.
An end portion of the stringer may be provided with half a scallop. Two stringers having such end portions can be mated in an end to end configuration which will provide a full scallop. The applicant has found that such stringers can be used where a change in the direction of a walkway or a ramp is desired. It will be appreciated that where the change in direction occurs a gap is generated between the two successive treads. A suitable landing may be used to fill this gap.
An end portion of the tread may be adapted for mounting a stanchion. For example, the end portion may be provided with a suitable hole preferably formed during casting. Stanchions may alternatively be secured to stringers.
It will be appreciated that the invention provides a versatile stringer and tread combination.
The scope of the invention extends to the stringer alone, the tread alone and to methods of manufacturing the stringer and tread each of which methods preferably includes a step of casting the stringer or tread using a suitable concrete.
Each tread may have added to it a riser which, preferably, depends from the front underside of the tread. The tread and the riser may be integrally cast of concrete. Alternatively, the riser is a separate component which fits into a groove provided in the front underside of the tread. Otherwise the risers may be open.
In accordance with the present invention there is provided a method of establishing a staircase or a ramp which staircase or ramp comprises using the stringer and tread combination of the invention.
The method includes a step of raking the stringer(s) to a required angle and a step of securing at least part of an underside of each tread in a scallop after the stringer(s) has been raked to the required angle and the upper tread surfaces levelled in the case of the staircase and in the case of a ramp or walkway after the upper tread surfaces have been arranged so that they are generally located in a plane.
The scope of the invention extends to a method of establishing a horizontal walkway comprising using the stringer and tread combination.
The method includes a step of arranging the stringer(s) in a horizontal position.
The method further includes a step of securing at least part of an underside of each tread in a scallop after the stringer(s) has been arranged horizontally and the upper tread surfaces levelled.
The stringers will, of course, be designed (e.g. in suitable steel reinforced concrete) to serve as end-supported beams, in most cases. They can also be bedded for their lengths in soil or concrete to provide staircases, ramps or walkways on soil or concrete ramps or beds.
This basic structure can also be applied to the manufacture of grand stands since in simple form they are conceptually equivalent to a large scale staircase where the riser height in staircases corresponds to the height of the seat and the tread in staircases corresponds to the seat itself, in grandstand applications preferably with sufficient space behind a seated person for the feet of the next user to gain access to the next seating place.
The principle is thus also applicable to providing seating in theatres and similar buildings and also stepped surfaces in theatres and similar buildings for the provision of conventional seating rows on such stepped surfaces in theatres.
In a typical grand stand application seat heights may vary from 300 mm to 500 mm high, outside which the comfort zone will be exceeded. A suitable seat including access behind, should be in the order of 800 mm wide, or in the range between 780 mm to 850 mm.
The invention can be implemented in materials other than concrete, for example, timber and plastic. The aesthetic possibilities inherent in the invention can, for example be realised with particular attractiveness in timber. Technological adaptations of the principle to timber would include the possibilities that the treads would be glued and screwed to the stringers.
Furthermore a corbel could in the case of timber be separately fabricated and fastened to the stringer by nailing, screwing and/or gluing, for example. A further interesting possibility which is perhaps particularly apt with the use of timber is to raise the angle of the staircase towards 90° when it becomes tantamount to a ladder. This application could, of course, also be implemented in concrete and other materials.
The application of the invention in plastics materials could be employed by techniques in which the tread is extruded. The stringers could be manufactured in modular form and then assembled and fibre re-inforcement techniques of the plastic could be useful both in the case of the stringers and in the case of the treads.
In the application of the invention to grand stands and similar applications as discussed herein the scale of the modular component such as the stringers and seats or seating platforms may well result in the components having to be placed in situ on a building site by means of suitable cranes, in contrast to the application for staircases where the components can, in many cases, be small enough to be manhandled into place.
The principle of the invention can furthermore be extended as has been stated to provide ladders or very steep staircases, that is at angles greater than is conventionally permitted, for example by standard building regulations for staircases, around 40° or 45°.
Prior art proposals have been made for stringer and tread combinations in which even if the tread is given a hemi-cylindrical under surface the stringers do not have merely circular scallops but instead more complicated indentations, notches or other formations for receiving the treads, thus giving them support on steeper angles of inclination. The shortcoming of these proposals is that such stringers cannot be used over a wide range of angles of inclination from the horizontal, indeed only over a very small range of variation of a few degrees, for example, and certainly not to the point where the stringer and tread combination can be used to provide a walkway or ramp. For these purposes these proposals of which the inventor is aware are quite unsuitable.
A further object of this invention is therefore to further extend the concepts described thus far in such a manner as to allow the stringer to be used at any angle between horizontal and an angle very close to vertical.
In accordance with this invention the essential feature is that the scallop diameter is less than the pitch between treads and the arc of the scallops is close to a semi-circle. In the preferred embodiment this will be accommodated by means of short straight portions parallel to the length of the stringer between scallops.
A secondary effect of this approach is that the treads have a relatively deep profile which can, of course, be an advantage for bending strength in the cases of long spans or in canti-lever arrangements for the tread.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of various examples with reference to the accompanying drawings in which:

Figure 1 is a partial side view of a stringer and tread combination in accordance with the present invention;
Figure 2 is a partial side view of a staircase comprising the combination shown in figure 1;
Figure 3 is a cross-section of the combination along III - III in figure 1;
Figure 4 is a partial side view of another stringer and tread combination in accordance with the present invention;
Figure 5 is a partial side view of a staircase comprising the combination shown in figure 4, but with three different types of treads;
Figure 6 is a cross-section of the combination along IV - IV in figure 4 and a tread is shown having a mirror image to that of the tread shown in figure 4; and
Figure 7 is used to show how a pitch of the scallops can be calculated.
Figure 8 is a side elevation showing grand stand seating.
Figure 9 is a side view on a tread,
Figure 10 is a side view on a stringer,
Figure 11 is a side view on treads and stringers of the kind shown to provide a steep staircase at 45°,
Figure 12 shows the treads and stringers combined to provide a ladder at 60°, and
Figure 13 shows the tread and stringers combined to provide a ladder at 80°.
Figure 14 is a plan view showing a walkway landing,
Figure 15 is a side elevation showing a capital and support column,
Figure 16 is a side elevation from the other side showing the capital and support column,
Figure 17 is a front elevation of the capital and support column,
Figure 18 is a side view of the capital and support column supporting an alternative stringer,
Figure 19 is a side view from the other side showing the capital and support column and stringer shown in figure 18,
Figure 20 is a front elevation of a stanchion with hand rail and knee rail attached to a stringer,
Figure 21 is a side elevation of the same stanchion showing alternative angles of inclination of the stringer,
Figure 22 is a front elevation showing a stanchion with hand rail and knee rail attached to a tread,
Figure 23 is a side elevation showing the stanchion of figure 22 attached to a tread, the stringers at various angles, and
Figure 24 is an enlarged detail showing connection between a hand rail and stanchion, and
Figure 25 shows a collage of applications of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In figure 1 the reference numeral 10 generally indicates a stringer and tread combination in accordance with a first embodiment of the present invention. The stringer and tread combination 10 comprises a precast concrete stringer 12 and a plurality of precast concrete treads 13 each having an upper tread surface 14.
The top surface 15 of the stringer 12 is lengthwise provided with successive scallops 16. Lengthwise the shape of each scallop 16 conforms to the arc of a circle as shown in figure 1. In the transverse direction the shape of each scallop 16 is linear. A gap 18 is provided between each scallop 16. Figure 1 shows that the underside of each tread 13 has a co-acting shape to that of the scallops 16. Every scallop begins and ends on the same longitudinal line 200, that is to say, the arc of each scallop; this "line" is an imaginary line, of course.
Figure 3 shows that the stringer 12 has a trapezium shaped cross-section which the applicant has found to be advantageous for casting and for removal of the stringer 12 from a mould after having been cast. The shape is useful in providing a greater width at the top to bear compressive stress, tensile stress at the bottom being born by steel re-inforcing, in beam loading.
The stringer 12 is provided with a plurality of side to side holes 20 extending through the stringer 12. The holes 20 reduce the mass of the stringer 12 and facilitate transportation thereof. Crowbars can be located through the holes 20 thus enabling the stringer 12 to be carried. For raising the stringer 12 a sling and crane can be used with the string located through the hole 20 and fastened to the stringer 12.
Each tread 13 can be secured parallel with the stringer 12 as shown in figure 1. More specifically the upper tread surface 14 is generally parallel with the bottom surface 23 of the stringer 12. This embodiment of the combination 10 can thus be used to construct a horizontal walkway or a ramp.
In order to establish a horizontal walkway, a ramp or a staircase the stringer(s) 12 can simply be laid onto a surface or with the bottom surface 23 of the stringer 12 embedded in the ground. Overhead walkways and ramps can be constructed by using supports, for example poles or columns, which may be secured to the stringers 12 via the respective holes 20. After having located the stringer(s) 12 as aforementioned the treads 13 are located in the scallops 16 and the upper tread surfaces 14 levelled when a walkway or staircase is constructed. For a ramp the upper tread surfaces 14 are arranged so that they are generally located in a plane. The treads 13 are then secured to the stringer(s) 12 by gluing their undersides to their respective scallops 16.
An end portion 24 of the stringer 12 is provided with half a scallop 25 which allows for two stringers 12 to be mated in an end to end configuration. The mated end portions 24 will thus provide a full scallop akin to the scallop 16 into which a tread 13 can be located. A walkway or a ramp having a change in direction can also be constructed using a plurality of the stringers 12. Viewing such a walkway or ramp from above will show that a gap is formed between the two successive treads 13 where a change in direction occurs. A suitable landing can be used to fill this gap (see figure 14).
Figure 2 shows a staircase 30 which has been constructed using the same stringer and tread combination 10 shown in figure 1. The staircase 30 has been established by raking the stringer 12 to an angle of 30 degrees. The treads 13 have been rotated in the scallops 16 to render the upper tread surfaces 14 level. After having been levelled, the underside of each tread 13 which is in contact with the scallops 16 is secured to the stringer 12 in the scallops 16 by means of gluing. Setting up of the staircase 30 may be accomplished by, preferably, first raking the stringer 12 to the required angle and then locating the treads 13 in their respective scallops 16. Alternatively, the treads 13 can be simultaneously raised with the stringers 12 after the treads 13 have been rotated and secured by means of gluing in the scallops 16 so that the upper tread surfaces 14 become level when the stringers 12 have been raised.
It will be appreciated that the walkway, ramp and staircase 30 may comprise one or more stringers 12 for supporting the treads 13. Referring to figure 3 a cross-section is shown of a ramp or walkway using only one stringer 12. This type of stringer 12 which passes beneath the treads 13 allows the treads 13 to form cantilevers as is evident from figure 3.
Figures 1, 2 and 3 show that the stringer 12 and tread 13 have been provided with cast in re-inforcements in the form of metal bars 26, 27, 28. The bar 26 is located between the holes 20 and the top surface 15 of the stringer 12 while the bar 27 is located between the holes and the bottom surface 23 of thestringer 12. The bars 28 are provided in the overlap 29 of each tread 13 to render the treads 13 more resistant to tensile stresses during stepping onto the upper tread surface 14 of the overlap 29.
Figure 4 shows another embodiment of a stringer and tread combination which is generally indicated by the reference numeral 50. The stringer and tread combination 50 comprises a precast concrete stringer 52 and a plurality of precast concrete treads 54 each having a generally flat upper tread surface 55.
The stringer 52 is provided with a single projection constituting a plurality of corbels 56. Each corbel 56 is provided with a scallop 58 having the same shape as that of the scallops 16 shown in figures 1 and 2. A gap 60 is provided between each scallop 58. Figure 4 shows that the underside of each tread 54 has a co-acting shape to that of the scallops 58.
The stringer 52 is further provided with a plurality of holes 61 serving the same purpose as the holes 20 of the first embodiment stringer 12.
The combination in figure 4 can be used to construct a horizontal walkway, a ramp or a staircase. At least two stringers must be employed, the one being the stringer 52 and another stringer 62 having the mirror image of the stringer 52. These stringers 52, 62 are used in pairs, as shown in figure 6, with the stringers arranged opposite, spaced apart and generally parallel to one another. As for the stringer(s) 12 the mentioned pairs of stringers 52, 62 can simply be laid onto a surface or with the bottom surface 63 embedded in the ground. Overhead walkways and ramps can also be constructed by using supports, for example poles or columns which may be secured to the stringers via the respective holes 61. After having located the stringers 52, 62 as aforementioned, the end portions 63 are located in the respective scallops 58 and the upper tread surfaces 55 levelled when a walkway or staircase is constructed. For a ramp the upper tread surfaces 55 are arranged so that they are generally located in a plane. The treads 54 are then secured to the stringers 52 by gluing their undersides at their end portions 63 to their respective scallops 58.
An end portion 64 of the stringer 52 is provided with half a scallop 65 which serves the same purpose as the half scallop 25 discussed previously.
A staircase can be constructed by using the stringer and tread combination 50 shown in figure 4 together with a stringer 62 shown in figure 6. The staircase is established by raking the stringers 56, 62 to a required angle, for example 30 degrees as shown in figure 5, and arranging them opposite one another, suitably spaced apart and generally parallel to one another. The end portions 63 of the treads 54 are located in their respective scallops 58 and the upper tread surfaces 55 levelled. The underside of each portion 63 which is in contact with the scallops 58 is then secured to the respective stringers 52, 62 in the scallops 58 by means of gluing. Figure 5 shows a partial view of a staircase 70.
The treads 54 are re-inforced in the same way as the treads 13 using metal bars 28 in the overlap 72. A metal bar re-inforcement 74 is further provided in the stringer 52, 62.
Figure 5 shows that the staircase 70 comprises three different types of treads 54, 76, 78. Each of the treads 76, 78 has added to it a riser 80, 82 which depends from the front underside of the tread 76, 78. The tread 76 and riser 80 has been integrally cast using concrete. The riser 82 is a separate concrete casting which fits into a groove 84 in the underside of the tread 78.
In order to have comfortable stairs the Neufert formula in which twice the riser plus the tread width equals 600 to 650 mm is applied. Using a riser of 200 mm and a tread width of 250 mm which is the steepest stair allowed by official building regulations in R.S.A. and applying the Neufert formula we get (2 x 200) + 250 = 650 mm which satisfies the criterion for comfortable stair design. Figure 7 shows the riser 89 of 200 mm and the tread width of 250 mm which tread width is the distance between the point 90 and the nose 92 of the tread 13.
Referring to figure 7 and applying Pythagoras' theorem a diagonal distance of 320 mm is generated from tread nose 92 to tread nose 94. The pitch of the scallops 16, 58 is taken as 320 mm.
The tread width 96 shown in figures 1 and 4 is 310 mm when the stringer 12, 52 is horizontal and with the upper tread surfaces 14, 55 level or with the stringer 12, 52 inclined and with the upper tread surfaces 14, 55 generally located in the same plane. The gap 18, 60 is taken as 10 mm.
Using the dimensions above, the minimum required overlap 98 (fig. 7) is obtained when the rake comes down to 27 degrees with the riser being 147 mm.
It will be appreciated that the riser 89, the tread width and the overlap 98 will vary with a change in the rake.
The view in Figure 8 of the drawings is a side elevation of a stringer 90 and seat 100 supported on it in a grandstand. The stringer is at 30° which is appropriate for grand stand seating and the stringer is provided with scallops on a 750 mm radius which is matched, of course, by the underneath surfaces of the seats. The scallops are placed on the stringers with a 900 mm pitch along the length of the stringers and a clear width of each seat, that is which is not overlapped by the next succeeding seat is 774 mm in this arrangement. The height between seats is 460 mm. These features are indicated on the sketch. Holes in the stringer are of some interest for aesthetic and/or lightness advantages.

With these considerations in mind the inventor has suggested a choice of a pitch (measured along the length of the stringer) in the region of 900 mm for the scallops and with this choice the following range is covered :

SEAT HEIGHT	SEAT WIDTH	ANGLE
300	849	19.4
310	844	20.1
320	811	20.8
330	837	21.5
340	833	22.1
350	829	22.8
360	825	23.5
370	820	24.3
380	816	24.9
390	811	25.6
400	806	26.3
410	801	27.1
420	796	27.8
430	791	28.5
440	785	29.2
450	779	30.0
460	774	30.7
470	767	31.4
480	761	32.2
490	754	32.9
500	748	33.7

The radius used for the scallops is determined by the following factors :

1. The structural depth required for the seat.
2. The length of interface between beam and tread required to give an adequate bond of seat to beam.
3. The need for seats to overlap slightly in plan. The larger the radius the thinner the structural depth of the seat segment and the smaller the bond interface at steeper angles.

A radius of 750 m would probably optimise these criteria.
As reflected in the above table typical angles for grand stand seats are somewhat lower than is typical for staircases, for example in the range of 20° to 30° measured to the horizontal.
As shown in figure 9 the typical tread 101 has an under surface 102 which is hemi-cylindrical, the upper surface 103 being flat for stepping on. The surface 102 has a radius of curvature 104 which by way of example is 130 mm. This can be contrasted with the fact that the pitch 105 between treads is in this example 320 mm. The width 106 of the tread in this example is 230 mm.
Thus the stringer 107 shown in figure 10 for use with these treads has scallops 108 which have a radius of curvature 109 exactly equal to the radius of curvature 104 of the under surface of the treads, namely in this example 130 mm. Thus the diameter of the scallops (and of course of the under surface of the treads) is 260 mm, thus smaller than the pitch 105 of 320 mm between the treads in the assembled stairs or ladder,as can be seen in figure 102 the pitch 105 is the length of the pattern which is successively repeated along the length of the stringer.
Holes 110 are shown in the stringer as a lightening or attachment convenience. At the ends of the stringer a half scallop 111 is provided which means that the stringers can be joined end to end for the provision of walkways.
A staircase made with these treads and stringers is shown in figures 11 and 12 where the same numerals are used for the various features discussed with reference to figures 9 and 10. In figure 11 the angle is 45° and in figures 12 and 13, 60° and 80° respectively, thus the former can be described as a very steep staircase and the latter two as ladders.
Another important feature of the invention which is preferably adopted is that the centre 112 on which the circular shape of each scallop is generated is in line with the upper edge 113 of the stringer so that a full semi-circular scallop is available for placing the tread in position. This means that the canti-lever portion of the tread is quite reduced and as will be seen with reference to the following figures 12 and 13 still within acceptable limits even on the steepest use of the tread and stringer combination of this invention. The short straight portions 114 between scallops could be reduced by increasing the diameter of the scallops, but not to a diameter greater than the pitch 105 between scallops. This would have the advantage that if the stringer is placed horizontally to make a walkway then the edges or the treads will be contiguous to provide a walkway without gaps.
As shown in figures 12 and 13 this tread and stringer combination is amenable to very steep inclinations, as shown for example in figures 12 and 13 of 60° and 80° respectively.
Figure 14 shows a landing 150 to accommodate a change of direction of a walkway, having half scallops 151 and 152 to mate with co-acting half scallops at the abutting ends of stringers (e.g. as shown in figure 1 the half scallop 25) to carry a tread.
Figures 15 to 17 show the use of a capital and column type support for walkways and staircases. The capital comprises cylindrical body 120 with a groove for carrying a pin 121 which passes through a hole 122 of the stringer 123. A face 124 of the capital is cut away to make it possible for the stringer 123 to be mounted at an inclination in this example of up to 38°. After installation grout is applied in the spaces visible in the view of figure 16.
The use of the same capital for the type of stringer in which the scallops are placed in the upper surface of the stringer is shown in figures 18 and 19, the same reference numerals have being used. With the arrangement shown, left hand and right hand capitals are provided for alternate sides of the stringers.
Figures 20 and 21 show the mounting of a stanchion 125 by means of a flange 128 on to the side of a stringer 129. Hand rail 126 and knee rail 127 are carried by the stanchion. The detail in figure 24 shows how the hand rail 126 is fixed to the top of the stanchion 125 by means of a steel rod of mild steel 130 which can be bent on site to the required angle thus co-operating in this way with the flexibility of the system in being able to adopt any suitable angle of rake.
Figure 22 and 23 show a stanchion 131 carrying a hand rail 132 and knee rail 133, the stanchion, however, in this case being mounted at its base 134 to a tread 135 which is provided with a suitable hole 136 for this purpose. A bolt projects from the lower end of the stanchion 131 at its flange 134, passes through the hole 136 and is bolted in position.
Figure 25 shows at 120 a staircase structured using two stringers and a plurality of treads and also showing hand rails fixed to the treads.
The feature at 121 shows two stringers in this case with the scallops formed on inwardly facing corbels on each stringer and with the treads showing an integrally formed riser depending from each tread so as to close the space between treads.
The feature at 122 shows a horizontal ramp using the same stringers and treads as shown in the previous drawings, illustrating the versatility of the apparatus.
The feature at 123 shows again the same stringers and treads forming an inclined ramp.
The Neufert formula leads to the possibility to make a selection of the pitch distance between the noses of the treads and accordingly the pitch distance of the scallops in the stringers. Thus in accordance with the invention a preferred pitched distance is 320 mm or it lies between, for example 290 and 330 mm. Standardising on this dimension of pitch for the scallops in the stringers allows a system for staircases, walkways and ramps to be offered to the public which can be employed in all the different ways described in this invention. In the installation of a staircase a fixed dimension is the pitch of say 320 mm. This allows the variation of the rise dimension, the tread dimension or the angle of the staircase in any particular application.
Most frequently, because the floor to floor height for a particular staircase is pre-determined by the building, a riser height must be chosen as the starting point. The following example illustrates how the method is then applied :

Example: Given a floor to floor height of 2 635 mm

1. Choose the number of risers (say 14) $2 635/14 = 188,214 mm riser$
2. The tread length by Pythagoras
(using 320 for the hypotenuse) will be $T = 320²-188,214² = 258,796$
3. The angle by cosine will be $258,796/320 = ,809 = 36°$
4. The going distance in true plan will be: $13 treads @ 258,796 = 3 364$

A tabulation of the various options available to the designer, again it must be stressed using the same stringers and treads of the invention can be illustrated in the following tabulation
As can be seen the angles of staircases using the apparatus for this invention are infinitely variable between 0° and 40° or even 45°.
A system of stringers and treads with other dimensions can be provided for very steep staircases or ladders above 45°, as described.

Claims

A stringer and tread combination in which the stringer is lengthwise provided with successive integrally formed scallops each of which has a lengthwise shape conforming to the arc of a circle each of which scallops can accommodate at least part of an underside of a tread which underside has a co-acting shape to that of the scallops and in which the scallops begin and end on the same longitudinal line of the stringer.
A stringer and tread combination as claimed in claim 1, in which the combination comprises two opposed, spaced apart and generally parallel stringers each stringer on its inner side surface includes scallop shaped corbels for supporting the end portions of the treads.
A stringer and tread combination as claimed in claim 1, in which the end portion of each stringer is provided with half a scallop so that two stringers having such end portions can be mated in an end to end configuration which will provide a full scallop.
A stringer and tread combination as claimed in claim 3, provided also with a landing adapted to fill a gap between two sets of stringers and treads, the landing having mating half scallops on two of its edges.
A stringer and tread combination as claimed in claim 1, in which each tread incorporates a riser which depends from the front underside of the tread.
A stringer and tread combination as claimed in claim 1, for ladders, in which the scallop diameter is less than the pitch between treads and the arc of the scallops is close to a semi-circle and in which the centre on which the circular shape of each scallop is generated is in line with the upper edge of the stringer.
A stringer and tread combination as claimed in claim 1, in which the end portion of each tread is adapted for mounting a stanchion.
A stringer and tread combination as claimed in claim 7, provided in combination also with stanchions having handrail supports of bendable material allowing a handrail to adopt an angle equal to the angle of the staircase or walkway or ramp.
Stringers for a stringer and tread combination as claimed in claim 1 which stringer is lengthwise provided with successive integrally formed scallops each of which has a lengthwise shape conforming to the arc of a circle each of which scallops can accommodate at least part of an underside of a tread in which the scallops begin and end on the same longitudinal line of the stringer.