GB2433078A

GB2433078A - Structural Member

Info

Publication number: GB2433078A
Application number: GB0623763A
Authority: GB
Inventors: John O'neill
Original assignee: ARENA EVENT SERVICES GROUP Ltd
Current assignee: ARENA EVENT SERVICES GROUP Ltd
Priority date: 2005-12-09
Filing date: 2006-11-28
Publication date: 2007-06-13
Anticipated expiration: 2026-11-28
Also published as: GB0525152D0; GB0623763D0; GB2433078B

Abstract

A modular bearer 34 for a space frame of a grandstand has a plurality of weight bearing supports 42 arranged one above another so as to permit fine variation of deck height. The bearer 34 allows construction of a grandstand having a progressively increasing rake to the rear, allowing people seated at the rear to have an unobstructed view.

Description

1 2433078 Structural Member This invention relates to a structural

member for use in building, and is particularly concerned with a structural member of a space frame.

Space frames generally comprise a plurality of inter linked structural members and typically form a sub-structure upon which other building elements are mounted. Such space frames may for example form the supporting structure of a roof, or a stage, or of seating. These structures may be permanent or semi-permanent, but most usually are temporary and are provided for the duration of a public event.

A characteristic of this kind of space frame is that it is typically assembled on site from a few common components, and is adapted to local site conditions. Thus the sub-structure may accommodate variations in ground level and be shaped to suit the site footprint, to the intent that upon removal the site is returned to its previous state.

For reasons of labour cost, it is generally paramount that the sub-structure can be erected speedily with a minimum of custom parts, and be dismantled speedily with maximum re-use of components. These components should be readily adaptable to different sites, and be inexpensive to produce and to transport. The space frame should be capable of being assembled by unskilled labour, yet meet acceptable standards of safety and appearance.

One kind of space frame system comprises steel scaffolding. However scaffolding requires specialist construction, and tends to be unsightly because of protruding pole ends and the large number of individually affixed clamps.

Other kinds of space frame have been developed for specialist use, such as for demountable grandstand seating. Typically such seating is in modular form, and is available with a low or with a high fixed rake; large grandstands may have a low rake at the front, and a high rake at the back. However such systems do not approach the ideal parabolic rake, by which a person of average height will have substantially the same

field of view in every seating position.

What is required is an improved structural member which can provide greater variation for space frame construction, and particularly better height adjustability so as to accommodate the required variations in deck height.

According to a first aspect of the invention there is provided a modular upright of a space frame, said upright comprising opposite sides, and each side having a plurality of weight bearing supports arranged thereon one above another.

Such an upright or bearer can accommodate variations in deck height according to the pitch of the supports. Typically uprights according to the invention are arranged on or as part of a sub-structure and are spaced by ledgers or ties of the sub-structure. The ledgers or ties may extend between opposite supports, and are preferably of a common kind, and preferably substantially identical. The ledgers preferably determine the fore and aft spacing of the uprights.

Preferably the supports are at a common pitch on one, and preferably both sides. A common pitch ensures that each upright has a defined distance between each support and its neighbour(s), and this facilitates design and construction of a space frame.

In a preferred embodiment the supports of one side are non-symmetrical with respect to the centreline. This arrangement allows an upright to be turned through 1800 so as to present a support to a ledger at a different height. For example the supports on one side may be offset by a half pitch with respect to the centreline which thus permits half-pitch height variability of the supports.

In a preferred embodiment the upright is an extrusion, preferably of aluminium or an aluminium alloy, and said weight bearing supports extend along the length of the extrusion. Such an arrangement allows ledgers to extend between uprights at any lateral location, and in a number to suit the requirements of the space frame. Thus for example certain portions of a space frame may have single spaced ledgers whereas others may have double or triple ledgers placed adjacently to suit loadings.

Furthermore the spacing of ledgers may vary according to the space frame design, so that for example the spacing may be reduced where higher loadings are anticipated, such as at the stairways of temporary grandstands.

In a preferred embodiment the upright is a hollow extrusion, thus combining low mass with comparatively high stiffness and strength.

Each support is preferably in the form of a recess having an upwardly facing lip with which to engage a depending limb of a ledger. The lip may be of a shape and size determined by the requirements for strength and durability. The depending limb and lip are preferably adapted for close engagement by sliding via the open end of the extrusion. In this way the uprights and bearers may be self-supporting during assembly.

A particular problem with space frames for temporary grandstands is that of providing adequate leg room and seat spacing. Hitherto, the design of such grandstands has relied upon rows of uprights arranged in the fore and aft direction so that each tier is at a fixed distance from its neighbours. Lateral bearers extend between these rows to support seats. This arrangement fixes fore and aft seat spacing and thus leg room at the design stage, and accordingly a different design may be required for persons of large average stature (e.g. USA) from persons of small average stature (e.g. the Far East). It would be preferable for a single design to be adaptable to different seat spacing so as to avoid such complexity, and to permit a user to select an appropriate leg room on demand. In practice an increase in fore and aft spacing of the rows of prior art uprights is accompanied by a change in rake because the height of prior art uprights is fixed. This is a substantial disincentive to increasing leg room because lines of sight are adversely affected.

According to a second aspect of the invention, there is provided a modular space frame of a grandstand, and comprising parallel rows of extruded upright, each upright comprising continuous weight bearing supports at the front and rear sides, and a & plurality of ledgers extending between and supported on respective supports of adjacent rows.

In such a space frame the spacing between rows of seats, and hence the leg room, can be selected according to the length of the ledgers. Thus the space frame may be customized to suit the intended use by variation of a relatively simple and inexpensive component. Furthermore, height adjustability of the uprights ensures that lines of sight can be optimized for all leg rooms, thus avoiding the prior art disadvantage of an inevitable change of fixed rake.

Other aspects of the invention will be apparent from the following description of a preferred embodiment of the invention shown by way of example only in the accompanying drawings, in which:-Fig. I is a schematic side sectional view of a conventional grandstand of low rake.

Fig 2 is a schematic side sectional view of a conventional grandstand of higher rake.

Fig. 3 is a schematic side sectional view of a grandstand incorporating the present invention.

Fig. 4 is a cross section through a bearer extrusion of the invention; Fig. 5 is a cross section through a bearer with floor board positions illustrated; Fig. 6 is a cross section through the bearer of Fig. 5 in the upturned condition; Figs. 7 & 8 illustrate an upstand for the bearer of Figs. 5 & 6.

A

Fig. 9 is a schematic side section of a grandstand according to the invention, with walkways.

Fig. 10 is an alternative bearer extrusion.

With reference to Fig. 1, a conventional arena grandstand 10 comprises a lateral array of trusses 11, of which one is shown, connected by a plurality of lateral bearers (not shown) which bridge adjacent trusses. The grid thus formed presents an angled planar deck onto which can be mounted suitable stepped flooring 12 and seats 13. In the example of Fig. 1, 28 rows of seats are provided at a vertical pitch of 152 mm.

Typically the grandstand 10 will be temporarily assembled from parts for the duration of an event, and subsequently disassembled. It will be appreciated that whilst the rake of the grandstand is fixed, the length and depth can be varied to suit requirements.

Such a fixed rake grandstand employs a large number of common parts but has the disadvantage that a fixed point 14 is progressively obscured for those sitting towards the rear of the stand since the eye-line is determined by the height of the person in the preceding row of seats. Assuming an average head height, and thus a fixed downward viewing angle, it will be seen that the rear most eye-line 15 is much higher than the front eye-line 16, and thus action close to the grandstand is obscured.

Conventionally, visibility of a seat is indicated by a C' valve, a minimum of C90 being desirable for good view. In the example of Fig. I a person in the front row has a view of C=98, but at half height the view has deteriorated to C35, and at the rear to C=23 or less.

Fig. 2 shows that matters may be improved by increasing the rake of the stand 20, but more complex trusses 21 are required because of the additional height and weight of the structure, and a complete solution is not provided.

In the case of Fig. 2, the second seat row provides C188; at half height C=68, and at the rear C44 or less. It will be appreciated that if the ledgers of Fig. I are used at the rake of Fig. 2, leg room is reduced. Thus a different length of ledger is desirable, but with the additional costs and reduced commonality of parts.

What is required is a parabolic profile, but such an arrangement cannot be obtained with standardized parts because, for example, the spacing of truss uprights reduces as the ledgers between them increase in angle. This means that either multiple length ledgers are required, or the leg room is progressively reduced towards the rear. Neither is acceptable as a compromise.

Fig. 3 illustrates the present invention as applied to an arena grandstand 31. In place of a lateral array of spaced trusses, a grid-like array of legs 32 are connected by standard ledgers 33 each having a fixed rake angle, but arranged stepwise at each leg 32 at a convenient height.

As illustrated, each leg 32 is at double the seat pitch, and thus each ledger 33 is arranged to support a seat row at the mid-point. The legs 32 and ledgers 33 define an uneven angled grid, unlike the constant angled grid of the prior art, and each leg is assembled from standard length struts connected in any suitable manner. Ledgers may support more rows of seats if the design permits, i.e. the legs 32 may be further apart.

At the top of each leg 32 and at the mid-point of each ledger 33 is provided a laterally extending bearer 34 in the form of a hollow extruded alloy box-section 35. As will become apparent, the bearer is of standard form but provides for fine adjustment of the vertical pitch of each succeeding seat row in the fore and aft direction, thus permitting a very close approximation to an ideal eye-line for each seat.

The bearers 34 may act as the sole spacing between laterally adjacent legs 32 allowing rapid construction of a temporary structure. Preferably however other means are provided to space the legs laterally, since this avoids a requirement to link the bearers end to end. Suitable cross bracing is introduced in any suitable manner using conventional techniques.

Any suitable means may be used for attaching the bearers to the legs 32 and ledgers 33; one means being shown in Figs. 7 & 8 in relation to the preferred embodiment of bearer shown in Fig. 4.

Each bearer 34 comprise extruded alloy section of generally oblong box-like form with recesses 42 along both long sides. On the left side as viewed, six identical recesses 42 are bounded on one respective side by a plain wall portion 43 so that a plain portion precedes an indentation in the vertically downward direction. Each recess 42 is rectangular and comprises a narrow lateral mouth defined by symmetrical upper and lower lips 44. It will be appreciated that if turned through 1800, the recesses 42 are at respective heights which are intermediate those illustrated in Fig. 4, thus permitting 12 different support heights for the same base height, at a pitch of e.g. 34 mm.

On the right side, as viewed, identical recesses 42 are provided at the upper and lower extremities, and symmetrically therebetween are located two larger recesses 45 again of generally rectangular form with symmetrical upper and lower lips 46. If the beam is turned through 180 , the relative positions of the right-side end recesses and larger recesses 42,4 5 are unchanged.

Orthogonal partition walls 47 are provided adjacent each left-side recess 42 in order to add strength and stiffness to the extrusion, and as illustrated extend from the mid point of each recess.

Figs. 5 and 6 illustrate how the vertical pitch of each successive seat row can be varied.

Fig. 5 shows the bearer 34 can support on the left side a floor panel 51 at six different heights with respect to a floor panel 51 located in the top recess at the right side. Each floor panel is of standard section and comprises a board 52 having an extruded alloy hook 53 attached thereto. As illustrated the hook comprises a box-section portion 54 on which is provided an upward facing flange 55, and a C' shaped portion 56 adapted to tightly engage over the board edge.

Each hook 53 is typically engaged in a suitable recess 42 by sliding from one open end so as to provide a highly engaged assembly. Four typical board positions are shown in Fig. 5.

Fig. 6 shows how half pitch board positions can be obtained by rotating the bearer 34 through 1800. In the preferred embodiment, 12 different heights at 34 mm pitch are obtainable, allowing very fine adjustment of the height of each succeeding seat row.

Figs. 5 and 6 illustrate an insert 61 in the shape of an apertured plate which is slidably located in each recess 45. The aperture 62 provides the means by which the bearer 34 is supported on each leg 32 and ledger 33.

Figs. 7 and 8 show an upstand 71 comprising a tubular plug 72 adapted to be inserted into the open upper end of a tubular leg 32. A plate 73 limits insertion depth and has an upstanding flange 74 provided with four hooks 75. These hooks are insertable into apertures 62 of the inserts 61 and engage the side walls thereof by gravity and/or wedge action. The hooks are offset to one side of the axis of the plug 72 so that in use, the centre of the bearer 34 lies immediately over the associated legs 32.

In use a space frame is assembled by constructing legs 32 of an appropriate height from modular sections, and spacing those legs in fore and aft direction by use of the ledgers 33. Because the ledgers are at a constant angle, the leg room is the same for all seat positions.

Suitable lengths of bearer 34 (for example 3m) are provided laterally, and may be connected together to form long lengths as the space frame is constructed. Endwise connection is not necessary where other means of laterally spacing the legs is provided.

Floor boards are fitted at the appropriate height and seats attached.

in the example of Fig. 3, 28 rows of seats are illustrated. The first four rows have a fixed riser of 136 mm. In these rows the C' valve progressively reduces, and at a minimum acceptable level, the riser is increased by adopting different recess 42. Thus for the next eight rows a riser of 170 mm is provided, and the riser is increased as the C' valve approaches the selected minimum. In the example shown, the rearmost groups of eight rows have respective risers of 204 mm and 236 mm which gives a C' valve at the rear of the stand of about C=l00.

Fig. 9 illustrates how a temporary grandstand 81 can be constructed using the same modular components, but with horizontal walkways 82 at the front, middle and rear; such a necessary feature is very difficult to achieve with the prior art systems of Figs. I and 2.

Fig. 10 illustrates an alternative bearer extrusion 90 having a succession of equispaced indentations 42a at one side and corresponding to the left side indentation of Fig.6.

These indentations are offset from the centreline to permit a half pitch variation of floor board position if the extrusion is rotated through 180 .

On the right side, end indentations 42b are provided at the extremities, and corresponding to the right side indentations of Fig.6. Partition walls 47 are provided to stiffen the extrusion.

Between the indentations 42b is provided a channel 45a having opposed lips 48 and adapted to receive endwise a sliding inset (not shown) corresponding injunction to the inset 61 of Figs.5 and 6. By providing a single inset, the extrusion is somewhat simplified.

The insets of Figs. 5, 6 and 10 may be laterally secured in any suitable way, for example by adhesive or mechanical fixings such as rivets. If of compatible material welding may be used.

The insert of Fig. 10 is adapted for fixing to a suitable upstand, such as that illustrated in Figs.7and8.

Thus the invention can provide a mixture of flat, fixed rake and variable rake surfaces in combination, and from a standardized range of components. Although the invention has been described in relation to temporary grandstands, it will be appreciated that it is applicable to other kinds of structure, such as stages.

Claims

Claims 1. A modulator upright of a space frame, said upright comprising

opposite sides, and each side having a plurality of weight bearing supports arranged thereon one above another.

2. An upright according to claim I wherein on one said side the supports are at a common pitch.

3. An upright according to claim 2 wherein said supports are non-symmetrical with respect to the centre of said upright.

4. An upright according to claim 3 wherein said supports are offset by a half pitch about said centre.

5. An upright according to any of claims 2-4 wherein on the other side the supports are symmetrical about the centre of said upright.

6. An upright according to any preceding claim wherein each of said supports comprise a mouth having an upwardly facing lip adapted to receive and retain a hooked member.

7. An upright according to claim 6 wherein each of said mouths comprises an upwardly and a downwardly facing lip, and said lips are symmetrical about the centreline of said mouth.

8. An upright according to any preceding claim and comprising a hollow extrusion, said supports extending along the extrusion axis and being integrally formed.

9. An upright according to claim 8 and defining six equispaced supports at one side, and two supports at the other side.

10. A modular upright substantially as described herein with reference to the accompanying drawings.