AU643360B2 - Structural member - Google Patents

Description

Llr 7yj/ Y) \cgulation 3.2

AUSTRALIA

Patents Act 1952 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

om o Name of Applicant: BORAL AUSTRALIAN GYPSUM LIMITED Actual Inventor(s): WILLIAM GILBERT POYNTER GRAEME ALEXANDER BROWN Address for Service: Invention Title: DAVIES COLLISON CAVE, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

STRUCTURAL MEMBER Details of Associated Provisional Application(s): No(s): The following statement is a full description of this invention, including tile best method of performing it known to me/us: -1- The present invention relates to a structural member comprising a column or beam, which may or may not be load bearing, and cladding for the column or beam.

Cladding for beams and columns has various applications, for example for decoration. However, it is particularly .o used in the building industry to provide fire protection for steel beams or columns which, in the event of a fire, 25 effectively begin to lose strength at about 550 0 C and, 25 ultimately, may no longer support a load and may collapse.

oo"o The fire resistance of the cladding is measured by a fire rating which gives an indication of the duration for which the cladding will provide protection.

Structural members of other materials, which may require cladding in the building industry, include reinforced concrete, prestressed concrete, concrete encased steel, steel encased concrete and timber and wood based members.

The column or beams may have any one or more of a plurality of shapes and structures including I-shaped members, box members, hollow members, solid members, rectangular 930903,PHHSPEO11,baratspc,2 -3- (including square), round and oval.

Steel columns and beams are currently protected against fire by spraying them with, for example, cement or gypsum based mixtures which are then allowed to dry.

It has also been proposed to provide fire protection by cladding with one or more layers of fire resistant boards, such as plasterboard, but problems have arisen relating to the attachment of the boards to the column or beam, especially with respect to the gripping of screws in side edges of the plasterboard or similar material. It is necessary that the boards be screwed together to give adequate strength or life to the cladding in use, but it is not possible with plasterboard and similar material to Ssecure adjacent boards together by passing a screw fastener through the thickness of one into a side edge of the other.

Many proposals exist for overcoming this problem using metal studs or angle members which underlie the boards at the corners and into which the screw fasteners engage through the boards, or using external beads at every corner in every layer of the boards which are pinned to the respective underlying boards with every layer being secured 4 by wire which surrounds the cladding. The latter proposal is not suitable for beams where the cladding does not o. s extend wholly around them. Additionally many of these

I

proposals are very labour intensive, requiring in some cases substar .ial frameworks to support the angle members, which makes the proposals commercially disadvantageous.

Furthermore, in all known proposals using u°iderlying studs and angle members, the screw fasteners extend through the boards at positions somewhat removed from the edge portions thereof, requiring an external metal angle or bead to prevent the possibility of the edges of the b6ards curling during a fire or under other conditions.

920120,PHI-SPEO I1,boralspe,3 -4- The present invention attempts to alleviate the above mentioned disadvantages. The invention has particular application for situations requiring fire protection, and will hereinafter be so described, but is not restricted solely to that application. Thus, the cladding may, for example, be provided primarily for decorative purposes.

Boards to which the present invention is applicable include plasterboard, fibre reinforced cement and gypsum boards, vermiculite (exfoliated) and calcium silicate boards, particle board, plywood and fibreboards.

According to the present invention there is provided a structural member comprising a column or beam and cladding for the column or beam in the form of at least one layer of board members overlying exposed sides of the column or beam to define a multi-sided casing in which adjacent board members in said at least one layer overlying respective sides of the column or beam overlap at the side edges of the casing, and wherein said overlapping adjacent board members in the or each layer are secured together by at leasit one elongate angle member having a respective leg [secured by screw fastening means to an inner face of each of the adjacent board members, and further wherein one of the legs of said at least one angle member extends between the inner face of one of the adjacent board members and a side edge of the other of the adjacent board members and towards the adjacent side edge of the one adjacent board member.

30 The term "exposed sides" refers to any sides or aspect of :the beam or column for which cladding may be required.

Thus, for example, if a four-sided beam supporting a floor is disposed immediately adjacent a wall, the casing in accordance with the invention may comprise board members overlying only two sides of the beam. The beam will then he encased by the wall, the floor structure and the board 930903,PHHSPEO11.bomaspe,4 members. The beam or column may be round or oval and the term "sides" should be construed accordingly.

By the present invention, the screw fastening means, preferably self tapping screws, which extend through the one board member to engage with the one leg of the angle member may be disposed immediately adjacent a side edge of said one board member to alleviate curling of the board member adjacent the side edge without the screw fastening means having to engage the side edge of the other board member. No framework is necessary for the cladding.

Advantageously, the one leg of the angle member extends only partway to the adjacent side edge of the one adjacent board member so as to minimise exposure of the angle member to external heat.

0 One angle member may extend along substantially the length of the adjacent board members so as to facilitate their alignment and attachment. Alternatively, a plurality of shorter angle members may be used, in which case, it is preferable that adjacent angle members overlap or abut so as to provide a continuity of them along the length of the boards. Alternatively, in some cases, the shorter angle members may be spaced apart.

4 The angle members are preferably light gauge mild steel, which may be galvanized or otherwise surface treated, which do not require predrilling to receive the screw fastening means. Alternatively, any other suitable material may be used.

Advantageously, each side of the casing is spaced from the respective side of the column or beam by a plurality of packing members which are spaced apart along the column or beam.

920120,PH~1SPSO1I ,P0 -6- The spacing between the column or beam and the casing provides additional insulation to the beam or column in the event of a fire, without an additional layer of, board members, as heat is not readily transferred across the spacing.

The packing members may be held in place by the location of the casing about the column or beam or may be bonded or fastened to the board members orly or to the column or beam only or to both. Preferably, the board members are screw threadedly fastened to the packing members.

In the event any side of the casing requires a plurality of board members, for example when the board members are too short to extend along the full length of the column or beam, it is advantageous that a packing member underlies each joint between longitudinally adjacent board members.

Such a packing member provides a backing for the joint which may be used to facilitate the construction of the 20 casing. If the cladding is used as fire protection for the beam or column, a packing member underlying a joint between longitudinally adjacent board members may provide a seal whicah helps insulate the beam or column from heat passing through the joint. In such a case it is accordingly preferable that fire rated material be used for the packing member.

The provision of the spacing between the casing and the column or beam and/or the provision of a packing member at each joint between longitudinally adjacent board members may alleviate stress on the cladding caused by movement of the beam or column. For optimum stress relief it is thus preferable that there be a plurality of board members along each exposed side.

Where two or more layers of board members form the casing 9M 120,PHHSPE.O H boratspe,6 -7each overlying layer may either be directly in contact with the preceding layer or be spaced therefrom by further packing members. The or each subsequent layer of board members may have adjacent board members connected in accordance with the invention in which case it may not be necessary to secure adjacent layers together.

Alternatively, each additional layer may be attached directly to the preceding layer.

Two embodiments of the invention will now further be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view f one embodiment of the invention showing a structural member comprising a column and cladding for the column; Figure 2 is a view similar to Figure 1 but showing a second embodiment of the invention; and Figure 3 is a perspective view from below of the embodiment of Figure 2 showing packers for the cladding in dotted outline.

S Referring now to Figure 1, there is shown a structural member 10 comprising a column 1 formed from a steel I-beam and a single-layer of fire protective cladding for the column 1. The I-beam has four sides defined by the opposed I outer faces of the flanges 2 thereof and between the distal 30 edges 2a of the flanges parallel to the web 4. The cladding comprises boards 3 overlying the respective sides o .of the column to define a box-like four sided casing 6.

.The boards 3 are spaced from the column 1 by packers Adjacent boards overlying respective adjacent sides of the column overlap at the side edges 8 of the casing 6 and are held together by angle members 7 as will hereinafter be 930903,PHHSP.O11.borLspe,7 I I I -8described in detail.

The boards 3 and the packers 5 are of the same fire resistant material such as fire rated plasterboard which is most conveniently about 25 mm .thick.

The boards 3 are attached to the packers 5 by threaded fasteners 9. The packers 5 are relatively short (along the length of the column) and each exposed side of the column 1 is provided with a plurality of packers 5 each of which extends transversely across the respective side of the column in a spaced apart manner from an adjacent packer on the same side. The packers 5 may be attached to the column 1 by bonding prior to the attachment of the boards 3, using for example stud or cornice adhesives, or by fasteners such as screws or clips, but generally will not be attached at all so that they are held in place only by the casing 6.

The packers 5 are arranged to underlie the joints between abutting boards where a plurality of boards overlie one exposed side of the column 1, with intermediate packers as necessary. Those packers underlying the joints may then provide a sealing surface behind the joints which, in the event of a fire, may help insulate the column 1 from the flames or heat.

If the boards 3 are relatively rigid the provision of plural abutting boards along each exposed side of the 6" 4 column 1, as well as packers 5 underlying the joints between the abutting boards and the spacing provided between the boards and the column, assists in reducing stress in the boards caused by movement of the column. The fasteners 9 should allow sufficient flexibility of the boards at the joints. Instead of or in addition to the fasteners 91,' the boards may be attached to the packers 5 by bonding wiitlh a flexible adhesive.

930903,PHHSPEO11.boralspe,8 In addition to the fire protection afforded to the column 1 by the boards 3, the spacing between the column 1 and the boards defined by the packers 5 provides additional insulation as heat is not as readily or quickly transferred from the boards to the column as when the boards are placed in direct contact with the column.

Turning now to the connection of the boards 3 to each other, angle members 7 are provided at the side edges 8 of the casing to connect the boards 3 on adjacent sides of the column or beam. To facilitate the alignment of the boards, only one elongate angle member extending substantially along the length of the boards may be used at each side edge for each pair of adjacent boards. Alternatively, a plurality of shorter elongate angle members may be used for each pair of adjacent boards at the side edges, and, in this instance, it is preferable that there be some overlap between any adjacent shorter angle members such that there is effective continuity of the angle members along the length of the boards. The angle members 7 are of light gauge mild steel.

The manner in which the boards are held together will now 25 be described with reference to one angle member 7 between adjacent boards 3a and 3b. The attachment of other adjacent board members is achieved in like manner as can clearly be seen.

30 The angle member 7 is disposed such that each leg thereof lies along an inner face of a respective one of the adjacent boards 3a and 3b, that is a face which is directed towards the column 1. One of the legs 11 of the angle member 7 extends between the boards 3a and 3b. The boards 3a and 3b are secured to the angle member 7 by self-tapping screws 13 which extend through the thickness of the boards 930903,PHHSP.O11,boLspe,9 and screw-threadedly engage the legs of the angle member 7 without predrilling. None of the fasteners need. extend into a side edge of either of the boards 3a and 3b to secure the boards to the angle member.

The leg 11 of the angle member 7 extends between the boards 3a and 3b only partway to the outer surfaces of the boards so that, in the event of a fire, the angle member 7 has only a reduced exposure to the flames or heat. Thus for boards having a thickness of 25 mm, the width o2 the leg 11 may be about 20 mm. For convenience the width of leg 12 is greater.

Using boards having a greater thickness than has hithereto been proposed, say about 25 mm, may enable only one layer to be used for a particular fire rating when plural layers would otherwise be necessary. The fire rating of a structural member increases with each additional layer of boards, but, the cost in labour and materials also increases with each additional layer of cladding required.

It is thus desirable that a specific fire rating be achieved with as few layers of board as possible.

If a higher fire rating is required than is provided by one layer of boards in the casing 6, one or more further layers of boards, generally denoted by 15 and shown in dashed lines, may be added. The attachment of the boards no each •additional layer is the same as described hereinbefore witch reference to the first layer. Alternatively, additional 30 layers of boards may be attached directly to the initial layer. The layer 15 of boards is shown attached to the first layer of boards with no intermediate packers but :these may be provided if desired.

Referring now to Figures 2 and 3, there is shown a structural member comprising a beam 20 supporting a 930903.PH HSPOl0LborLspe, W -11concrete floor 22, so that only three sides of the beam are exposed, and cladding for the exposed sides of \ie beam comprising rigid boards 24 which are connected to form a casing 25 and are spaced from the beam 20 by spaced packers 26.

Adjacent boards 24 are held together at the side edges of the casing 24 in the same manner as hereinbefore described with reference to Figure 1. Likewise, the attachment of the packers 26 to the beam and the attachment of the boards to the packers is the same as in Figure 1 and will thus not be repeated. The angle members 7 are not shown in Figure 3, for clarity reasons.

The attachment of the casing 25 to the concrete floor 22 will be described for convenience with reference to only one of the boards 24.

4 Once packer 26a has been attached to the beam, leg 29 of an 20 angle member 27 is attached to the concrete floor 22 by fastener 30 and/or adhesive such that leg 28 of the angle member 27 lies along the outer surface of the packer 26a.

The associated board 24 is then attached to the packer 26a by means of a screw fastener 34 extending through the board and through the leg 28 of the angle member 27 and further screw fasteners extending through the board into the pacler 26a. The angle member 27 is identical to the angle member 7.

Any gap between the edge of the board 24 and the concrete floor 22 is sealed with a caulking material 32 such as cornice adhesive to assist in the insulation of the beam Alternatively, the angle member 27 may be secured first to the floor 22, in spaced apart manner from the beam 20, and 920120,PHHSPE.Ohl,boraLspe,II -12the board 24 may then be secured to the angle member. The packer 26a may then be introduced between the beam and board 24 and be secured to the board.

One or more further layers of boards which may also be fire rated plasterboard, generally denoted by 35 and shown in dashed lines, may be provided to increase the fire rating of the cladding if required. The attachment of each additional layer may be the same as the attachment of the first layer, except that each additional layer may be attached directly to a preceding Layer of boards rather than via packers. Alternatively, the or each additional layer of boards may be secured directly to a preceding layer or to intervening packers without the use of angle members.

As in the first embodiment, it is preferable that a plurality of boards overlie each exposed side of the beam and that packers underlie the joints between adjacent board members on that side so as to accommodate stress exerted on the board members at least to some degree and to improve the fire rating. Joints between adjacent board members may be filled or taped, or may be left dry.

The fire rating will also depend on the thickness of the boards and packers and the material constituting the boards and packers and the number of layers of boards will vary accordingly. Various factors, such as the size of the beam or government regulations, will influence such a choice.

The invention has been described by way of example only and modifications are possible within the scope of the following claims.

920120,PHHSPE.O01,boraLspe,12

Claims (2)

13- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A structural member comprising a column or beam and cladding for the column or beam in the form of at least one layer of board members overlying exposed sides of the column or beam to define a multi-sided casing in which adjacent board members in said at least one layer overlying respective sides of the column or beam overlap at the side edges of the casing, and wherein said overlapping adjacent board members in the or each layer are secured together by at least one elongate angle member having a respective leg secured by screw fastening means to an inner face of each of the adjacent board members, and further wherein one of the legs of said at least one angle member extends between the inner face of one of the adjacent board members and a side edge of the other of the adjacent board members and towards the adjacent side edge of the one adjacent board member. 2. A structural member according to Claim 1 wherein the one leg of said at least one angle member extends only partway to the adjace nt side edge of the one adjacent board member. 3. A structural member according to Claim 1 or Claim 2 wherein one angle member extends along substantially the length of the adjacent board members. S' 4. A structural member according to Claim 1 or Claim 2 30 wherein a plurality of angle members extend along substantially the length of the adjacent board members, adjacent ones of said plurality of angle members overlapping or abutting end-to-end. 5. A structural member according to any one of the preceding claims wherein the or each elongate angle member

930903.PHHSPE.O11,barLspe,13 -14- is formed of light gauge metal which is not predrilled to receive the screw fastening means. 6. A structural member according to any one of the preceding claims wherein each side of the casing is spaced from the column or beam by a plurality of packing members which are spaced apart along the column or beam. 7. A structural member according to Claim 6 wherein the board members are screw threadedly fastened to the packing members. 8. A structural member according to Claim 6 or Claim 7 wherein at least one side of the casing comprises a plurality of longitudinally adjacent board members and a respective one of the packing members underlies each joint between the longitudinally adjacent board members. 9. A structural member according to any one of the preceding claims wherein the casing comprises a plurality of layers of board members and each layer has the adjacent board members secured together as defined in Claim 1. *a 10. A structural member according to any one of the 25 preceding claims wherein the board members in the at least one layer comprise plasterboard having a thickness of about mm. 11. A structural member substantially as herein described 30 with reference to the accompanying drawings. DATED this 3rd day of September, 1993. BORAL AUSTRALIAN GYPSUM LIMITED By its Patent Attorneys DAVIES COLLISON CAVE 930903,PHHSPaO11,bo~raispe,14