Abstract:
Among other things, a load bearing wall structure for a building is disclosed. The load bearing wall structure includes frameless modular wall panels with each frameless wall panel having spaced skins of fiber reinforced cement sheet separated by a core of expanded in situ high density polyurethane foam bonded to inner faces of the spaced skins. Each frameless wall panel also has formed in upright edges a recessed channel forming, together with a recessed channel of an edge-abutting wall panel, a hollow aperture extending between top and bottom surfaces of the abutting frameless wall panels. A lower panel edge locating channel member securable to a building support base is also included. Further included is an upper panel edge locating channel member and a tensionable element extending via each hollow aperture between an anchor member secured to the base and the upper panel edge locating channel member.

Description:
CLAIM OF PRIORITY  
       [0001]     This is a Continuation-In-Part application of U.S. patent application Ser. No. 10/473,913, filed on Oct. 5, 2003, the entire contents of which are hereby incorporated by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     The following disclosure relates to building structures. In particular, the disclosure relates to building structures employing modular frameless load bearing structural panels and also to an improved construction system for assembling such modular panels to form a load bearing structure.  
       BACKGROUND  
       [0003]     The prior art is replete with modular building structures and associated construction methods, many of which suffer from a variety of problems. Amongst such problems are included the complexity and labour intensity of assembling elaborate framing systems to which modular panels are attached, the inconvenience attendant the use of plural individual fasteners to fix structural panels to one another, and the inferior load bearing capacity of many modular structures.  
         [0004]     An example of a prior art modular construction arrangement which employs a plurality of fasteners is U.S. Pat. No. 4,858,398 which discloses a structure using proportionally sized panels secured together by turn-lock fasteners inserted through aligned openings in adjacent sides of panels.  
         [0005]     A further exemplary prior art construction arrangement is that disclosed in French Patent Document Number 2 389 724. This document discloses a modular building using panels having adjacent vertical sides of complementary shapes. The panels are joined together by screws and are reinforced with metal plates at the location of the joints.  
         [0006]     Generally speaking, modular wall construction systems incorporating interfitting or interlocking panel systems may be classified as load bearing or non-load bearing.  
         [0007]     Examples of non-load bearing modular wall constructions are disclosed in U.S. Pat. Nos. 3,511,000; 3,512,819; 4,031,675; 5,094,053 and 6,679,021 which are limited either to internal partitioning or dividing walls or otherwise require a load bearing framework to support a roof structure or the like thereon.  
         [0008]     U.S. Pat. Nos. 5,007,222 and 5,640,824 describe load bearing modular wall structures. In U.S. Pat. No. 5,007,222, there is described an energy efficient load bearing wall construction comprising foamed plastic panels having load bearing studs located between or formed integrally with upright joints between adjacent panels. U.S. Pat. No. 5,640,824 discloses a fire resistant modular wall panel having corrugated or ribbed metal sheets separated by a plurality of bridge girt assemblies in the form of elongate brace members with non-combustible, thermally insulating spacers connecting the webs of the brace members to effect a compound metal/ceramic structure wherein structural loads are borne substantially by the exterior metal rib skin. The outer skins are secured to the brace members by rows of self-drilling/self-tapping screws and the interior cavity may be an air space or it may include a mineral wool-type insulating medium.  
         [0009]     Australian Patent 118357 discloses a modular building construction utilizing cored precast concrete wall panels with an upper channel to receive a horizontally tensionable member over the length of the wall. A truss-like frieze frame sits atop the wall panels.  
         [0010]     Australian Patent Application No 71777/74 describes a lightweight modular panel system comprising a foamed plastics core between decorative sheet styrene skins. These panels include spaced vertical cavities within the core and recessed channel-like apertures on all edges to receive steel reinforcing rods and poured concrete to form a load bearing panel with a steel reinforced concrete framing there within.  
         [0011]     U.S. Pat. No. 6,754,999 discloses a modular system comprising a plurality of metal framed load bearing walls fabricated from C-shaped studs and roof trusses connected by welding or self-tapping screws. Inner and outer walls may be finished with gypsum wallboard and weather resistant plywood respectively.  
         [0012]     Another building system for constructing lightweight preformed wall and roof panels for small dwellings and mobile homes is disclosed in U.S. Pat. No. 3,898,779. This system incorporates interlocking panels having a high density polyurethane core between decorative skins such as styrene sheets with decorative finishes. Although the wall panels are secured under compression by tensioned tie bolts extending through spaced cast-in tubes between a contoured upper tie bar and a base structure, the load bearing capacity of the panels is contributed by the provision of flat load bearing surfaces in the upper and lower edges of the panel members.  
         [0013]     U.S. Pat. No. 5,687,956 describes a reinforced fence and building wall construction with lightweight sandwich panels supported at their ends between spaced upright tubular posts.  
         [0014]     A method and apparatus for manufacturing foamed plastics laminated panels for modular building applications is disclosed in the applicant&#39;s Australian Patent No. 620338, the disclosure of which is incorporated herein by reference. Panels manufactured in the manner described therein are an example of those suitable for use with the present disclosure. One particular advantage of the applicant&#39;s previously disclosed method is that the panels may be conveniently fabricated at the building site.  
       SUMMARY  
       [0015]     Techniques related to a building structure and modular construction method are disclosed.  
         [0016]     In one aspect, a load bearing wall structure for a building includes frameless modular wall panels, with each frameless wall panel having spaced skins of fiber reinforced cement sheet separated by a core of expanded in situ high density polyurethane foam bonded to inner faces of said spaced skins. In addition, each frameless wall panel also has formed in upright edges thereof a recessed channel forming, together with a recessed channel of an edge-abutting wall panel, a hollow aperture extending between top and bottom surfaces of said abutting frameless wall panels. The load bearing wall structure also includes a lower panel edge locating channel member securable to a building support base. Further, the load bearing wall structure includes an upper panel edge locating channel member and a tensionable element extending via each hollow aperture between an anchor member secured to said base and said upper panel edge locating channel member whereby, in use, vertical loads applied to said wall structure are distributed substantially evenly through said spaced skins of said frameless modular wall panels.  
         [0017]     Implementations can optionally include one or more of the following features. The upper panel edge locating channel member can include a load transfer member. Also, the load transfer member can also include the upper panel edge locating channel member and a compression member, in use, acting in unison. In addition, one or more of the frameless wall panels can each include an elongate hollow aperture extending between upper and lower edges of said one or more frameless panels intermediate side edges thereof. Further, the elongate hollow aperture can extend adjacent a normally upright edge of the one or more frameless wall panels to accommodate a tensionable element. Also, the load bearing wall structure can further include a ribbed edge locating member securable to a face of a frameless wall panel to engage a recessed channel of a further frameless wall panel to form a 90° junction between the frameless wall panel and the further frameless wall panel. The ribbed edge locating member can include a channel-like recess behind a projecting rib extending longitudinally of the ribbed edge locating member, the channel-like recess, in use, being adapted to accommodate a tensionable element therein. Also, the ribbed edge locating member can include a mounting flange extending longitudinally thereof. Further, in use, a roof structure can be secured directly to the upper panel edge locating channel member to form an integrally coupled building structure.  
         [0018]     According to another aspect of the invention there is provided a building structure incorporating the load bearing wall structure as hereinbefore described, the building structure having a roof structure mechanically coupled to said base via said tensionable elements.  
         [0019]     The subject matter described in this specification provides many advantages. For example, a building structure employing load bearing frameless modular panels which overcomes or ameliorates at least some of the problems associated with the prior art are provided.  
         [0020]     Other features, objects, and advantages will be evident from the following description, drawings and from the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1A  is a front elevation view of an exemplary building structure;  
         [0022]      FIG. 1B  is an end elevation view of the building structure of  FIG. 1A ;  
         [0023]      FIG. 1C  is a schematic plan view of the building structure of  FIGS. 1A and 1B  showing the arrangement of frameless modular panels comprising the walls;  
         [0024]      FIG. 2A  is an enlarged partial sectional view of a base structure showing the junction of the floor structure with an outer wall;  
         [0025]      FIG. 2B  is an enlarged sectional view of the portion of  FIG. 2A  in the circle;  
         [0026]      FIG. 3A  is an exploded isometric view illustrating the erection of frameless, modular panels to form a wall, wherein the top load transfer member is an upper panel edge locating member;  
         [0027]      FIG. 3B  is an exploded isometric view illustrating the erection of frameless modular panels to form a wall, wherein the top load transfer member comprises an upper panel edge locating member and a compression member;  
         [0028]      FIG. 3C  is an enlarged detail view of an optional arrangement for locating the bottom edges of the frameless modular panels;  
         [0029]      FIGS. 4A and 4B  are enlarged sectional plan views of the aligned panels showing the configuration of the positive positioning profiles on the frameless modular panels;  
         [0030]      FIG. 5  is an enlarged partial sectional view of the roof area showing an arrangement of the fascia;  
         [0031]      FIG. 6A  is an end elevation of a modular roof panel;  
         [0032]      FIG. 6B  is an enlarged detailed view of the showing the positioning profiles on the roof panels; and  
         [0033]      FIG. 7  is an exploded isometric view showing the arrangement of corner junctions and tee-junctions of the walls. 
     
    
       [0034]     Like reference symbols and designations in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0035]     In general,  FIG. 1  shows a building structure  1  in the nature of a small dwelling which may be constructed. The structure includes a base  2 , a number of walls  3  and a roof  4 . The walls, whether external or entirely internal, are composed of modular panels  5 . The modular panels are fabricated to a typical module size of 900 mm wide by 3.0 m high. In some situations larger panels may be used, particularly to accommodate the pitch of a roof. The modular panels are secured to the base by tensionable tie rods (described later) which are disposed along the walls at 900 mm centres  6 . Additional tie rods are disposed at the sides of openings in the walls  7  and at the corners  8  of the building structure.  
         [0036]     The wall panels may be erected on a concrete slab or timber floor structure or, as illustrated in  FIG. 2A , on a floor structure comprising a panel support frame supported by screw-in foundations. In the latter arrangement, the walls  3  are supported in locating channels  12  by an inverted T-shaped frame member  10  mounted on screw-in foundations  11 .  
         [0037]     Floor panels  9  are also mounted on the inverted T-shaped member  10  and the floor panels  9  are generally attached via screws  17 A extending into a transverse support flange of member  10 .  
         [0038]      FIG. 2B  is an enlarged view of the region of wall support encircled in  FIG. 2A  and shows a lower panel edge locating channel  12 , in the form of a C section member, mounted on the outer support flange of the inverted T-shaped member  10  with the modular wall panels  5  located therein. Threaded studs  13 , for securing respective tie rods  14 , are fastened to the horizontal face of the outer flange of the inverted T-shaped member  10  by welding, screwing or the like and protrude via apertures  17  through the wall locating channel  12  into an upright hollow aperture  16  formed at the abutting edge junctions of adjacent panels  5  for engagement with a nut  15  fastened to the end of each tensionable tie rod  14 .  
         [0039]     The overall arrangement of the load bearing wall structure may be better understood by reference to the exploded views shown in  FIGS. 3A and 3B . Individual wall panels  5  are erected and aligned such that abutting recessed panel edge channels  16   a  together define hollow apertures  16  which align with studs  13  and co-operating apertures  17  in the wall locating channel  12 .  
         [0040]     Each tie rod  14  with attached joining nut  15  is inserted into a respective longitudinal aperture  16  and engaged with a respective stud  13  anchored in base  2 . A top member in the form of an inverted channel  19  locates the upper portions of panels  5  in edge to edge alignment and also functions as a load transfer member for vertically applied loads. Apertures  22  in the top member  19 , are sized to accommodate the shaft of the tie rods  14  and are spaced so as to correspond to the spacing of studs  13  whereby the upper ends of the rods  14  protrude through apertures  22  in the top member  19  when it is positioned over the modular wall panels. The upper end of the tie rods  14  is screw-threaded and engageable with a nut  23  to facilitate the tensioning thereof. The nuts  23  are engaged with the rods and tightened against the top member  19  to place the wall structure into compression to a desired degree.  
         [0041]      FIG. 3B  illustrates the partial completion of a wall, similar to that of  FIG. 3A , but wherein the top member comprises, in combination, an upper panel edge locating channel  20  and a compression member  21 . The compression member  21  is located over channel member  20 . Apertures  22  and  22 A in both the channel member  20  and compression member  21  respectively, are sized to accommodate the shaft of the tie rods  14  and are spaced so as to correspond to the studs  13 .  
         [0042]     As with the embodiment of  FIG. 3A , nuts  23  are engaged with the rods and tightened against the compression member  21  whereby the channel member  20  and the compression member  21  act in unison to impart a predetermined degree of compression into the wall structure.  
         [0043]      FIG. 3C  is an enlarged view of the manner in which panel edge channel  16   a  is aligned with aperture  17  in the lower panel edge locating channel  12  to allow the tie rods  14  to be anchored to the base  2  via studs  13  (not shown). In an alternative embodiment (not illustrated), the tie rods are externally screw threaded at both lower and upper ends thereof. The lower end engages with an internally screw threaded stud adapted, for example, for friction fitting in holes drilled into a concrete slab floor.  
         [0044]     For ease of description, the subsequent embodiments will describe the top member comprising an upper panel edge locating member and a compression member although it should be understood that the top channel-shaped member  19  will function alone as a load bearing member.  
         [0045]     The use of tie rods, preferably of high tensile strength, can overcome problems with fasteners, such as screws or the like, being pulled out of the modular panels in high wind load conditions.  
         [0046]     The capacity of wall structures arises by the ability of the wall panels to distribute vertical loads substantially evenly throughout the panel skins spaced by the foam polyurethane core. While cementitious products such as fibre reinforced cement sheeting show superior strength in compression, they exhibit poor tensile and flexural load capacity. When a relatively thin sheet of fibre reinforced cement of about 4 mm to 6 mm in thickness is subjected to a compressive load via opposed edges, it rapidly fractures due to a buckling mode of failure whereby as it buckles, one face of the sheet resists a compressive load but the other face is unable to resist a tensile load. By forming the core within a closed mould containing the spaced sheet skins, the liquid polyurethane is able to partially penetrate the porous sheet material as it undergoes foaming under pressure whereby the bond between the core material and the skins is maximized. The panel structure is thus analogous to an I-beam in that the fully supported but otherwise fragile outer skins are separated by a “web” of foam material which resists buckling of the outer skins when vertical compression loads are applied and also resists lateral deformation under load.  
         [0047]     Vertical static loads tests conducted on a 75 mm thick×900 mm wide panel with outer skins of 6 mm thick fibre reinforced cement sheeting and a cast in mould core of high density polyurethane having a density of 50 kg per metre 3  showed the panels easily supporting a load of 10 tonnes distributed over the width of the panel. Compression failures were noted at about 15 tonnes or greater. For 100 mm thick panels having 6 mm thick outer skins, a safe compressive load of 25 tonnes was achieved with about a 50% safety margin.  
         [0048]     Compared with low density foamed plastics panels wherein the outer skins are secured to the foam core by adhesives, the panels utilized have a load capacity of 4-5 times that of the laminated low density panels having a core density typically of about 15 kg metre 3 .  
         [0049]     The load bearing wall structures are thus readily able to resist both vertical and lateral wind loads due to the combination of the panel structure and the manner in which the wall structures are anchored to the base under compression via the upper load transfer members which act together in a unitary structure.  
         [0050]      FIG. 4A  shows in plan, a schematic view of one form of the upright edge abutment of frameless wall panels  5  having recessed channels  16   a  formed in the upright edge faces of panels  5 . The core  25  is typically 65-85 mm thick whilst the skins are between 4.5 mm and 6 mm in thickness. At the butt join between adjacent panels  5 , a hollow aperture  16  is formed from the two recessed channels  16   a  in the facing edges of the panels.  
         [0051]     When the panels are abutted, see  FIG. 4B , an upright hollow aperture  16  is formed to accommodate tensionable tie rod  14 . If required, additional hollow apertures or recesses (not shown) may be provided immediately under the panel skins for accommodating building services such as electrical wiring.  
         [0052]     As shown in  FIG. 4B , the upright joint between adjacent panels  5  may be enhanced by the location within hollow aperture  16  of a thin rectangular section steel or plastics tube  18  which not only assists in maintaining edge to edge alignment of wall panels from top to bottom but also provides additional reinforcement against lateral wind loads. Typically, the abutting ends of wall panels  5  will be coated with a gap filling flexible polymeric adhesive to maximise the insulating properties of the wall structure and otherwise to accommodate any minor movement due to thermal expansion and contraction of the panels. Where the rectangular tube  18  is located in the hollow aperture  16  between adjoining panels, it too may be secured with adhesive but it need not extend completely between the upper and lower channels  12 , 20  as it is not needed as a structural load bearing member, rather a key to maintain channels  16   a  in alignment. It readily will be apparent to a skilled addressee that the panel edge joints, whether reinforced with tube  18  or not are thermally efficient as there is no conductivity path from one side of a wall structure to the other.  
         [0053]     A first embodiment of a roof for the building structure is illustrated in  FIG. 5 . In this embodiment the roof  4  has a minimum pitch, typically of from 3 to 10 degrees, and is supported directly by the external load bearing walls  30  and by the internal load bearing walls  31 . The roof may also be comprised of modular panels as discussed in more detail below in relation to  FIG. 6A .  
         [0054]     The roof panels  33  are secured at one end to the external walls  30  by screws  34  which pass through the roof panels  33 , compression member  21  and upper panel edge locating channel member  20  before terminating inside the core of modular wall panel  5 . In this manner, the roof panels are mechanically coupled via the engagement between screws  34  and the combination load transfer member  20 ,  21  and thence via the rods  14  to base  2  to form a unitary structure.  
         [0055]     At the other end of the roof panel, near the ridge, the screws  34  securing the roof panels engage with the load transfer members atop internal walls  31  in the same manner as with the external walls  30 . The peak portion of the roof panels is covered by ridge capping  36  which extends over the roof panel securing screws  34 , which capping is secured to the roof panels by further screws  36 A.  
         [0056]     As shown in  FIG. 6A , the modular roof panels  33  in this embodiment include a 0.42 mm ribbed steel outer skin  37  and an injected polyurethane foam core  38  which has a 0.42 mm ribbed steel inner skin  39 , the panel is typically 100 mm thick, The underside of the roof panel is lined ( 39 A). The roof lining ( 39 A) may be 4.5 mm fibre-cement board, 10 mm plasterboard, random grooved ply or a timber ceiling screwed directly onto the ribbed steel inner skin. Suitably the roofing panel is hi-tensile sheet ribbed roofing profile. Wooden support blocks  40  are embedded in the core at spaced locations along one end and one side of the roof panel to provide mounting points for the fascia panel  41 , shown in  FIG. 5 .  
         [0057]     The floor panels described in  FIG. 2  may also be made of a similar panel construction as the roof panels described above and in reference with  FIG. 6 . The floor panels are also formed from hi-tensile ribbed steel decking and may be lined with either composite flooring, waterproof ply or a timber floor applied directly onto the sheeting by screws or gluing.  
         [0058]     The use of hi-tensile ribbed steel decking for roof and floor panels has the advantage of having high strength, light weight, and being able to span up to 7 metres, thereby providing ease of construction whilst reinforcing the building strength without the need for roof trusses, bearer and joist floor constructions or the like.  
         [0059]     The enlarged detail view of the roof panel joint in  FIG. 6B  shows the arrangement of a projection  42  and cooperating recess  43  formed in the sides of the foam core  38  of a roof panel  33 . The enlargement shows a ridge  37 A of the outer roof skin extending laterally past the core such that, when two cooperating roof panels are engaged, the extended ridge  37 A clips over the ridge nearest the side of an abutting roof panel. The core may also be undercut in the vicinity of the projection so as to produce a longitudinal cavity  44  when the roof panels are clipped together. This cavity may accommodate building services in the same manner as the subsidiary cavities provided in the wall panels.  
         [0060]     Returning to  FIG. 5 , the outer roof skin is turned-up  45  at the peak end edge thereof to minimise any leakage. The roof skin also extends past the foam core  38  and coplanar embedded wooden blocks  40 , so as to overhang the guttering  46  at the fascia end  47 . The wood or metal fascia panel  41  is suspended under the valleys of the overhung roof skin by screws  48  and attached to the embedded support blocks  40  by a further series of screws  49 . The screws which are sunk into the fascia support blocks also pass through gutter brackets  50  which brackets in turn support the guttering  46 .  
         [0061]      FIG. 5  is also generally illustrative of one way of forming a multi-story building structure. Instead of securing roof panels  33  over the tops of wall panels  30  as shown, floor panels  9  ( FIG. 2 ) as described above may be secured over the tops of wall panels  30  with threaded ends of tie bolts  14  protruding there through. Additional base locating channels  12  are then aligned on the upper face of the floor panels  9  over tie bolts  14  and further wall panels may then be erected thereon as if the floor panels  9  together form a base  2  equivalent to that shown in  FIG. 1A . Upper edge locating channels are then secured over the upper edges of the upper wall structure and tensionable tie bolts  14  are inserted into the apertures  16  formed between adjacent wall panels  30  to tie the top and bottom walls to the base  2  via the tie bolts  14 . Typically, a ground floor wall panel will be 100 mm thick while an upper floor panel is 75 mm thick. Additional rigidity is given to the building structure by the lateral bracing by the floor panels mounted between the upper and lower wall panels as well as a roof structure secured to upper load bearing channels secured over the upper edges of the upper wall panels.  
         [0062]      FIG. 7  shows the arrangement of the corners and tee-junctions of walls, in particular, the alternative arrangements of the upper edge locating channels and compression members at these junctions. A completed outer wall  30  is shown in place upon the base  2 , with an upper channel member  20  and compression member  21  on the top side thereof engaged by tie rod nuts  22 . The wall junctions commonly include positioning profile members  51  which are attached upright to the completed wall  30  at selected positions by screws  52 . Lower panel edge locating channels  12  are fixed upon the floor surface or base  2  to locate the modular panels making up the walls.  
         [0063]     An outer wall panel  53  is shown ready to be positioned at the corner of the structure, whereby the recess  53 A in the upright side of the outer wall panel cooperates with the rib  51 A of the positioning profile member. At a corner the upper edge locating channel  20  will have about 75 mm removed from the inner flange of the C channelling. The remaining web and outer flange of the C channelling member then run to the outer edge of the corner. The upper edge locating channel  20  on the joining wall simply adjoins or overlaps the other upper edge locating channel with a flange partially removed. The compression members  21  at the corner joint are machined to half thickness for the length of the corner joint, thus forming half thickness tongues. These half thickness tongues are arranged so that the compression members interlace or overlap, resulting in an even thickness of the compression members at the corner. One of the frameless modular panels forming the corner join has an additional longitudinal hollow aperture, capable of receiving a tie rod  14 . This additional longitudinal cavity is located so as to be at the centre of the corner join. Apertures  55  and  55 A are provided on the upper edge locating channels  20  and compression members  21  to facilitate fixing the members together and corresponding to the additional longitudinal cavity of the modular panel, thereby contributing to the structural integrity of the building.  
         [0064]      FIG. 7  also shows the tee-junction arrangement of an internal wall where a tie rod in an intersecting wall is not in immediate proximity, but is provided at the intersecting end of the internal wall. The internal wall panel  57  (shown in fragmentary form) engages with the respective positioning profile member  51  thereby defining a longitudinal hollow aperture behind rib  51 A. The upper edge locating channel  58  and compression member  59  include apertures  60  &amp;  60 A at their extremities. The upper edge locating channel  58  and compression member  59  are then disposed on the top side of the internal wall comprised of like panels  57 . The tie rod  14 , provided for the end of the internal wall, may then be inserted through the apertures  60  and  60 A and down into the cavity for securing the internal wall  57 .  
         [0065]     Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.