Abstract:
Fibre linear tensile elements  2  are strung between the floor slab  11  and the roof  12  of a building  1.  Each fibre linear tensile element has a structural core  21  of polymeric fibres or filaments which can accommodate the tensioning of the fibre linear tensile element. The core  21  is covered by a sheath  22  of polymeric material. The fibre linear tensile elements  2  carry clamping devices  3  which enable glass panels  4  to be secured in position. Each clamping device  3  clamps in position the corners of four adjacent panels  4  at a particular connection node of the glass wall  80,  as shown in FIG.  6.  Gaskets  78  are applied to fill the inter-panel joints.  
     Each fibre linear tensile element  2  may include a central optical fibre  23  for detecting any reduction in the tension during use. The tension of the fibre linear tensile elements  2  is monitored by a monitoring device 81 which can produce an appropriate alarm signal.  
     Because of the polymeric structural nature of the fibre linear tensile elements  2,  they will permit the curtain wall  80  to flex to some extent and their tensioning will only vary slightly in response to changes in ambient temperature. The polymeric material is also good at resisting surface corrosion.  
     The fibre linear tensile elements  2  with the clamping devices  3  prefitted are delivered to site on pallets  71,  so as to reduce the amount of work required on site. A laser level  74  may be used to ensure that the clamping devices  3  are positioned at their correct heights, before the glass panels  4  are fitted.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a panel system which may be installed in a building to form, for example, a curtain wall.  
         [0002]     The invention also relates to a building incorporating a panel system, a kit of parts for installing a panel skin in or on a building, and a method of installing in or on a building such a kit of parts.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is popular for a building to have a curtain wall of glazing panels in order to create a light, environmentally-controlled enclosed space for greater public amenity and security. For example, the facade of an office building may be two or more storeys high, and may be given an exterior curtain wall of glazed panels. The glazed panels are usually rectangular and abut against one another and are formed into rows and columns. They need to be supported in position. A metal framework of tensioned steel cables or rods, quite often incorporating bracing cables, is frequently positioned behind the glazed panels and forms a network extending vertically and horizontally, and also has a significant depth perpendicular to the glazed panels in order to be able to resist bowing or flexing of the glazed panels such as may be caused by wind pressure. The front face of the structural framework has clamps or feet which project forwards and are fastened through or bonded to the wall of glazed panels.  
         [0004]     Considering a rectangular array of rectangular glazed panels, the vertical and horizontal joints between the panels will resemble a grid, and it is usual for the structural framework to support the glazed panels at or near to the intersections or nodes of the grid.  
         [0005]     Usually, the weight of each glazed panel is individually transferred back to the structural framework, so that the bottommost panel in a particular column of the glazed panels does not have to bear the weight of the entire column.  
         [0006]     A structural framework of this general type is the Pilkington Planar (TM) system produced by Pilkington Plc.  
         [0007]     Such structural framework can be visually intrusive particularly if it is linked together horizontally as well as vertically and if trusses are incorporated.  
         [0008]     More recently, more compact structural support apparatus has been proposed. For example, U.S. Pat. No. 6,658,804 discloses a self-bearing flexible curtain wall system. A glass curtain wall comprises rectangular glass panels arranged as a matrix or array of columns and rows. The weight of the glass panels is transferred down through the stack of panels in a particular column. Structural stability is provided by positioning a plurality of vertical metal cables behind the glass curtain wall. The feet of the metal cables are secured into the sill of the building, and the tops of the cables are secured to the frame of the building. The metal cables are tensioned. Each metal cable carries a plurality of anchor fixtures which are free to slide up and down the cable. Each anchor fixture projects forwards into the glass wall at a node of the grid of the glass wall where a vertical joint between the panels intersects a horizontal joint. In this way, the anchor fixtures provide stability to the glass wall in the direction perpendicular to the plane of the glass wall without actually carrying the weight of the glass panels.  
         [0009]     The glass panels can flex relative to one another in a vertical direction and a horizontal direction, and the metal cables and their anchor fixtures can move backwards and forwards in order to accommodate this flexing.  
       SUMMARY OF THE INVENTION  
       [0010]     According to a first aspect of the present invention, there is provided a panel system comprising:  
         [0011]     an array of panels positioned side by side to form a panel skin;  
         [0012]     a plurality of fibre linear tensile elements which are generally parallel and extend from a first periphery to a second, opposite periphery of the panel skin; and  
         [0013]     a plurality of clamping devices which are clamped to the fibre linear tensile elements and are fixed to the panel skin.  
         [0014]     By using fibre linear tensile elements rather than metal cables, there is the benefit that, in use, there will be less variation in the tension of the supporting structure (the fibre linear tensile elements) resulting from thermal expansion and contraction. This is because of the lower coefficient of linear expansion of the fibre linear tensile elements.  
         [0015]     In the case of glazed panels, the fibre linear tensile elements will not damage (e.g. abrade or chip) the panels if they come into contact with them during installation of the panel system in a building.  
         [0016]     Fibre linear tensile elements made of polymeric material are non-conductive compared with steel alloy rods or cables, and thus electrolytic corrosion or surface oxidation of the fibre linear tensile elements will not occur.  
         [0017]     With the panel system of the present invention, the clamping devices are supplied clamped into position onto the fibre linear tensile elements. The clamping devices will usually be made of metal but, because of the resilient nature of the material of the fibre linear tensile elements, the clamping devices will not permanently produce localised damage at the clamping positions on the fibre linear tensile elements. This means that, if during installation of the panel system it is necessary to adjust the positioning of some of the clamping devices before the panels are fitted, there will be no significant, aesthetically-unattractive marking of the surface of the fibre linear tensile elements at the old positions of the clamping devices. Metal clamping devices for clamping onto a metal cable are known to leave permanent markings (indentations) at the old clamping positions.  
         [0018]     When installed, the panel skin may undergo a visibly-noticeable amount of flexing when, for example, it is exposed to wind loading. For example, an observer standing in front of a glass curtain wall which is glazing an atrium may easily notice the flexing caused by wind loading because the reflected images (of distant objects) in the glazed panels will appear to vary in a noticeable way. The degree of this flexing can be increased or reduced depending on the tension applied to the fibre linear tensile elements and on their fibre construction.  
         [0019]     The panel system is an architectural building system, and it may be used to provide a roof for a building, in addition to the more usual likely use of providing a wall for a building. The wall will often be planar, but the wall could be curved. This may be achieved by arranging for the curvature of the wall to occur in a direction transverse to the direction of the mutually-parallel fibre linear tensile elements. In relation to the panels, instead of having the usual planar configuration, the panels may be bowed so that each matches the local curvature of the curved wall. Thus, each panel may be convexely or concavely curved in one direction (the direction of the width of the wall). If the wall is sinuous or serpentine, some panels will be convex, some panels will be concave, and some panels might even be convex and concave at respective sides of a particular panel.  
         [0020]     We expect that the most commercially-popular form of the invention will be for the panels to be glazing panels, such as double-glazed units for an exterior curtain wall, or single-glazed units for an interior wall or ceiling such as in an office or hotel atrium.  
         [0021]     The fibre linear tensile elements and the clamping devices function together to act as a support structure for the panel skin, and they will usually be positioned behind the panel skin rather than in front of the panel skin, in relation to what is the usual viewing direction.  
         [0022]     It will usually be desirable for the fibre linear tensile elements to be as close as possible to the panel skin, so as to make less visually-intrusive the way in which the panel skin is supported. The clamping devices serve to space the fibre linear tensile elements from the panel skin, and a desirable spacing distance between each fibre linear tensile element and the adjacent surface of the panel skin is a gap size of 0.5 to 6 cm (more preferably, 0.5 to 5 cm, or 0.5 to 4 cm, or 0.5 to 3 cm, or 0.5 to 2 cm). Instead of the lower limit of the gap size being set at 0.5 cm, it could be set at a slightly bigger value such as 1, 1.5 or 2 cm for practical reasons, such as facilitating cleaning of the panels.  
         [0023]     Each fibre linear tensile element may have a structural core of (polymer) filaments with the core usually being surrounded by a protective sheath. The core may be formed by starting with a textile yarn of parallel filaments. A plurality of the yarns are twisted to make a wire and then a plurality of the wires are laid to make a strand. Then a plurality of the strands are laid in layers to make the core. As an alternative to this stranded or wire-lay construction, the core might be formed by braiding the filaments or by positioning the filaments to be generally parallel to the longitudinal axis of the fibre linear tensile element.  
         [0024]     The sheath may be braided or woven and may be of a different polymer material to that of the structural core. The sheath can serve to protect the structural core from the clamping forces applied by the clamping devices, because the material of the sheath is likely to be more resilient than the material of the core. Thus, if a clamping device needs to be unclamped, moved to a new position and then reclamped, the sheath material at the old clamping position will resiliently spring back to its original shape without leaving any significant visual indication of the old clamping position.  
         [0025]     The panel system will, in use, have a natural damping characteristic that depends on the tensioning of the fibre linear tensile elements. It will also depend on the characteristics of the particular plastic (polymeric) material used for the structural component of each fibre linear tensile element and its diameter. A panel skin that is oscillating will also be damped by air resistance in proportion to its surface area.  
         [0026]     It will be usual for each fibre linear tensile element to carry a plurality of the clamping devices forming an array of connection nodes between the fibre linear tensile elements and the panel skin. The panel skin may be scaled in size and shape in order to suit the particular commercial application.  
         [0027]     With the panel system of the present invention, the clamping devices are supplied clamped in their correct positions onto the fibre linear tensile elements. Done away from the building site, in the clean and controlled conditions of for example a factory, operatives can be trained to be highly skilled, and can accurately position the clamping devices on the fibre linear tensile elements. This saves time on the building site, and removes the element of uncertainty of having to rely on the installers at the building site to position the clamping devices with the risk that time and effort might be consumed in their having to repeatedly adjust the positions of the clamping devices during the installation process.  
         [0028]     Usually, each panel is generally rectangular. Quite often, the panels will be of the same size. More complicated alternatives to rectangular panels can be envisaged, such as a panel skin formed by tessellating hexagonal, pentagonal or square panels, or by tessellating combinations such as octagonal panels with square panels.  
         [0029]     In the preferred embodiment, the panels are positioned in a matrix-like formation to form the panel skin, with columns of panels and rows of panels which are generally perpendicular to the columns of panels; and the fibre linear tensile elements are generally parallel to the columns of panels. By positioning the fibre linear tensile elements in this way, it is easier to make them less visible compared with alternative possibilities such as the fibre linear tensile elements extending diagonally across the columns.  
         [0030]     Preferably, the fibre linear tensile elements extend along respective joints between adjacent columns of the panels. For example, the fibre linear tensile elements can be made less noticeable by filling the joints between the panels with sealant, particularly a sealant of a dark colour such as black, and by positioning the fibre linear tensile elements in close alignment with the sealant. In relation to a panel skin forming a curtain wall, the sealant may be of the weatherproof type.  
         [0031]     The fibre linear tensile elements may be given a particular colour and/or texture, e.g. they may be coloured black to be less visible. Thus the black colour of the fibre linear tensile elements may supplement the black colour of the sealant, in order to assist in making the fibre linear tensile elements less visible.  
         [0032]     In the preferred embodiment, each clamping device is fixed to at least two adjacent panels of the panel skin. For example, four panels may be clamped by gripping respective panel corners at a junction point (connection node) of the panel array.  
         [0033]     We expect that the most popular use of the panel system will be when the panel skin is a wall, such as an (exterior) curtain wall.  
         [0034]     In the preferred embodiment, each clamping device has a bracket which projects into the panel skin between the panels and has an upwardly-facing seat on which sit one or more of the panels.  
         [0035]     Thus, the weight of the panel(s) above the clamping device is carried by the clamping device, and transferred to the fibre linear tensile element to which the clamping device is clamped. The weight is not carried (or is only minimally carried) by the panel(s) below the clamping device in the wall. Thus the wall is not of the self-bearing weight type, and individual panels may be removed without compromising the surrounding skin structure.  
         [0036]     There is no need to provide each panel with a structural frame around its perimeter for the purpose of transferring the weight of the overlying panels to the underlying panels. Thus, for a glazed panel, the glazed area right up to the perimeter of the panel remains visible. Thus, the viewer of a curtain wall made of glazed panels will be presented with a wall of glazing, rather than a wall which is disfigured by unsightly structural frames incorporated in the panels.  
         [0037]     Preferably, two of the panels sit on the seat of the clamping device. For example, the bracket has an upwardly projecting divider splitting the seat into two seat portions on which respective panels sit. Thus, at a particular connection node in a curtain wall, the bottom right-hand corner of the left upper panel may sit on one seat portion, and the bottom left-hand corner of the right upper panel may sit on the other seat portion.  
         [0038]     Preferably, the bracket has a downwardly-facing guide which locates a top edge portion of the or each of one or more of the panels.  
         [0039]     The bracket may comprise a flange, and the upper surface of the flange may provide the seat and the lower surface of the flange may provide the guide, with the thickness of the flange defining the desired gap size of the horizontal joint between the upper and lower panels held in position by the clamping device.  
         [0040]     Preferably, two of the panels are located in position in the panel skin by the guide. For example, the bracket has a downwardly-projecting divider splitting the guide into two guide portions which locate respective panels. The top right-hand corner of the left lower panel at a particular connection node of the wall, and the top left-hand corner of the lower right panel, may be located respectively against the two guide portions.  
         [0041]     The upper and/or lower divider may define the desired gap size of the vertical joint between the left panels and the right panels held in position by the clamping device.  
         [0042]     In the preferred embodiment, the clamping device has a back plate at the rear of the bracket and a removable front plate at the front of the bracket, and the front plate is secured in position by releasable fastener(s) and clamps a plurality of the panels between the front and back plates.  
         [0043]     The fastener(s) enable a sufficiently large clamping force to be applied to securely hold the panels in position at the connection node provided by the clamping device. Gaskets may be interposed between the front and back plates and the panels.  
         [0044]     During installation of the wall, the front plates may initially be left off the clamping devices. The installer may face the generally vertically-positioned and fully tensioned fibre linear tensile elements and may present up the panels. After a particular clamping device has received all of its panels and any necessary corrections have been made to their alignment, its front plate may be fitted to securely clamp the panels in position. In this way, the panel wall may be built up, usually working upwards from the bottommost row of panels.  
         [0045]     Usually, the or each fastener will be adjustable (e.g. a bolt) so that the clamping force is variable and may be set at a desired value.  
         [0046]     In the preferred embodiment, the front and back plates are wider than the bracket, and the fasteners are located beyond respective lateral edges of the bracket and preferably extend from the back plate forwardly into releasable engagement with the front plate.  
         [0047]     This enables the bracket (e.g. flange) to be made substantially the same thickness as the shank of each fastener (e.g. bolt) as there is no need to provide an aperture in the bracket for the fastener which would require bracket material to be left above and below the aperture in order to avoid weakening the seat (and guide) of the bracket.  
         [0048]     In the preferred embodiment, the clamping device includes locking arms which project through the panel skin adjacent to the bracket for holding the panels in position in the absence of the front plate.  
         [0049]     For example, during installation of the curtain wall, the locking arms may be used to gently hold the panels in place until they are clamped in position by fitting the front plate.  
         [0050]     The locking arms are usually positioned above and below the back plate (e.g. two above and two below) so that there is one locking arm for each of the four panels usually fixed to the clamping device when building up the curtain wall.  
         [0051]     Each locking arm may be detachable from the rest of the clamping device so that, when the front plate has been clamped into position, the locking arms may be removed before sealant is applied to the inter-panel joints.  
         [0052]     Each locking arm may comprise a shank and a head at the distal end of the shank. Preferably, the head is rotatable (e.g. relative to the shank, or the shank and head are integral and rotate together relative to the part of the clamping device into which the shank is inserted) so that the head can be aligned along the inter-panel joint when offering up a panel to the clamping device, and the head can then be rotated to extend over the front face of that panel to hold it in position.  
         [0053]     In the preferred embodiment, each clamping device has a duct through which passes one of the fibre linear tensile elements, and the duct includes means for clamping the fibre linear tensile element.  
         [0054]     For example, the clamping means is releasable for unclamping the clamping device from its fibre linear tensile element. The releasable nature of the clamping means permits adjustment of the positioning of the clamping devices on the fibre linear tensile elements during the installation process in a building, e.g. to ensure that all clamping devices in a particular row are aligned prior to fitting the panels.  
         [0055]     In the preferred embodiment, the duct comprises first and second duct portions, the clamping means is provided on inner surfaces of the duct portions, and the duct portions are adjustable relative to one another to permit the clamping means to release the fibre linear tensile element.  
         [0056]     For example, wedge- or cam-like projections may be provided on the inner surfaces which engage with the fibre linear tensile element and prevent the clamping device from moving in either direction along the fibre linear tensile element. By unclamping and then reclamping, it is possible to adjust the grip position. The duct will usually be split longitudinally to form the duct portions.  
         [0057]     In the preferred embodiment, the first duct portion comprises a channel portion and the second duct portion comprises a cover plate which closes the channel portion and is releasably secured to the channel portion by fastener(s). The first duct portion may have a generally U-shaped duct cross-section. This duct portion may be integral with the back plate or bracket mentioned above.  
         [0058]     A plurality of the fasteners (e.g. two on each side of the cover plate) may be tightened up until the cover plate abuts against the channel portion, so that a predetermined maximum clamping force cannot be exceeded by over-tightening the fasteners.  
         [0059]     In order to reduce unwanted twisting of the clamping device on the fibre linear tensile element, the length of the duct is preferably at least twice (preferably at least three times) the height of the back plate (measured along the direction of the fibre linear tensile element).  
         [0060]     Also, the width of the back plate may be plus or minus 30% (or 20%, or 10%) of the length of the duct, so that the clamping device has a cross-like appearance when viewed from in front of or behind the panel skin.  
         [0061]     In the preferred embodiment, the panel system further comprises first and second termination devices at respective ends of each fibre linear tensile element for securing the fibre linear tensile element to static building components.  
         [0062]     For example, one termination device may be fitted into a floor slab at the bottom of a wall and the other may be fitted to a structural frame at the top of the wall.  
         [0063]     Preferably, each termination device comprises a static anchor portion, a movable portion secured to the respective end of the respective fibre linear tensile element, and an adjustment mechanism for adjusting the position of the movable portion relative to the static anchor portion along an adjustment axis generally aligned with the fibre linear tensile element.  
         [0064]     One or both of the termination devices may be used to tension up the fibre linear tensile element. The two termination devices may then be operated in synchronism in order to adjust the positioning of the clamping devices of that fibre linear tensile element without altering its tension. This may be necessary, for example, when installing a curtain wall, because it may be apparent after the initial tensioning up of all of the fibre linear tensile elements that a particular fibre linear tensile element&#39;s clamping devices are not aligned correctly with those of the neighbouring fibre linear tensile elements.  
         [0065]     For example, a laser line may be projected along a particular row of clamping devices in order to check whether they are levelly aligned.  
         [0066]     In the preferred embodiment, at least one of the fibre linear tensile elements includes a longitudinal monitoring filament which is connectable to monitoring apparatus arranged to monitor the tensile loading of the or each such fibre linear tensile element.  
         [0067]     The monitoring filament may be embedded along the core (rather than in any sheath) of the fibre linear tensile element, preferably along the central axis. It can be used to raise an alarm if the originally-set tension drops below a threshold value.  
         [0068]     In the preferred embodiment, the longitudinal monitoring filament is an optical fibre.  
         [0069]     The optical fibre may be incorporated at the time of manufacture of the fibre linear tensile element. The monitoring apparatus may shine a light along the optical fibre and monitor for characteristic changes as the tension applied to the fibre linear tensile element (and thus to the embedded linear optical fibre) varies during use.  
         [0070]     Preferably, each fibre linear tensile element includes such a longitudinal monitoring filament.  
         [0071]     For example, the monitoring filaments could be connected together in series by the monitoring apparatus. Preferably they are connected in parallel to the monitoring apparatus so that the apparatus can individually monitor each fibre linear tensile element. Thus an alarm signal may identify any fibre linear tensile element where a change has occurred.  
         [0072]     Each monitoring filament will usually run the full (tensioned) length of the fibre linear tensile element. For example, there may be untensioned end portions above and/or within the top termination device holding the fibre linear tensile element and below and/or within the bottom termination device, and these end portions may be unpicked to expose the optical fibre embedded at the centre of the core of the fibre linear tensile element. The exposed ends of the optical fibre can be connected to the monitoring apparatus to form an optical monitoring circuit.  
         [0073]     In some embodiments, where it is desirable for there to be less flexing of the panel skin, elongate structural supports are fixed to the clamping devices and extend transversely between the fibre linear tensile elements. Thus, the fibre linear tensile elements are given additional stability for limiting deflection of the panel skin. The structural supports may be stiffening spars or other rigid elongate members.  
         [0074]     In many such installations, the structural supports are generally parallel to the rows of panels. For example, the structural supports extend along respective joints between adjacent rows of the panels.  
         [0075]     Conveniently, the structural supports are connected to rear portions of the clamping devices. For example, the connection may be to the duct and/or back plate of the clamping device.  
         [0076]     According to a second aspect of the present invention, there is provided a building incorporating a panel system according to the first aspect of the present invention, wherein the fibre linear tensile elements are secured to static components of the building and are tensioned. In most applications, there will be uniform tensioning of the set of fibre linear tensile elements.  
         [0077]     In many installations, the panel system is positioned such that the panel skin is a curtain wall.  
         [0078]     According to a third aspect of the present invention, there is provided a kit of parts for installing a panel skin in or on a building, comprising:  
         [0079]     a plurality of panels positionable side by side as an array to form the panel skin;  
         [0080]     a plurality of fibre linear tensile elements each having a length sufficient to extend from a first periphery to a second, opposite periphery of the panel skin; and  
         [0081]     a plurality of clamping devices which are clampable to the fibre linear tensile elements and are configured to receive and fix in position the panels of the panel skin.  
         [0082]     Preferred aspects are as discussed above in relation to the first aspect of the present invention.  
         [0083]     Usually, the panel skin is a rectangular array made up of rectangular panels. For an array of X columns and Y rows of panels, where the fibre linear tensile elements are to be aligned with the columnar grid lines of the array, there will usually be (X−1), X or (X+1) fibre linear tensile elements depending on whether both, 1 or 0 respectively of the outer side edges of the outermost columns of the panel skin are fixed to the building rather than to respective fibre linear tensile elements.  
         [0084]     Usually, there will be (Y−1), Y or (Y+1) clamping devices clamped to each fibre linear tensile element depending on whether both, 1 or 0 respectively of the top and bottom edges of the top and bottom rows of the panel skin are fixed to the building rather than to the fibre linear tensile elements.  
         [0085]     Each clamping device is a panel mounting node of the grid of the panel array. The clamping devices along the periphery of the grid will grip two panels (if on an edge of the grid) or one panel (if at a corner of the grid). The clamping devices inside the periphery will each grip four panels.  
         [0086]     In many building installations, the pattern of spacing of the clamping devices along a fibre linear tensile element will be the same for all the fibre linear tensile elements. If the panels are of a uniform size, the spacing will be uniform along each fibre linear tensile element.  
         [0087]     According to a fourth aspect of the present invention, there is provided a method of installing in or on a building a kit of parts in accordance with the third aspect of the present invention, the method comprising:  
         [0088]     securing the fibre linear tensile elements at their ends to static components of the building and tensioning the fibre linear tensile elements, such that the fibre linear tensile elements are generally parallel; and  
         [0089]     fixing the panels to the clamping devices as an array forming a panel skin.  
         [0090]     Preferably, the panel skin is planar and, prior to fixing the panels, alignment of the clamping devices into rows transverse to the fibre linear tensile elements is checked by projecting a laser along each row and any clamping device in that row that is out of alignment is unclamped from its fibre linear tensile element and reclamped at an improved alignment position. Alternatively, all clamps on a particular fibre linear tensile element may be repositioned by simultaneous adjustment of its top and bottom terminations.  
         [0091]     Alternatively, a laser level may be used to check the height of individual clamping devices.  
         [0092]     In the preferred embodiment, for a predetermined desired deflection in response to a predetermined loading of the panel skin, the actual deflection under the predetermined loading is measured and the tensioning of the fibre linear tensile elements is adjusted until the actual deflection substantially equals the desired deflection. The deflection may be measured at a point of envisaged maximum deflection (e.g. the centre of the panel skin) in response to a loading that, for example, simulates a predetermined wind loading.  
         [0093]     In practice, we have found that the tensioning necessary to keep the deflection below an acceptable threshold value has the effect of making the panel system naturally damped (self damped) in terms of amplitude and frequency. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0094]     Preferred non-limiting embodiments of the present invention will now be described with reference to the accompanying diagrammatic drawings.  
         [0095]      FIG. 1  is a perspective view of a building showing an early stage of a method in accordance with the present invention of installing a panel system on the building.  
         [0096]      FIG. 2  is a perspective view showing a later stage of the installation method.  
         [0097]      FIG. 3  is a perspective view showing, broken at the middle, a fibre linear tensile element of the panel system of  FIG. 1  with its upper and lower termination devices.  
         [0098]      FIG. 4  is a perspective view of the fibre linear tensile element of  FIG. 3  showing it installed at its upper end.  
         [0099]      FIG. 5  is a perspective view of the fibre linear tensile element of  FIG. 3  showing it installed at its lower end.  
         [0100]      FIG. 6  is a rear perspective view of a connection node of the installed panel system of  FIG. 2 .  
         [0101]      FIG. 7  is an exploded front perspective view of a clamping device shown in  FIG. 6 .  
         [0102]      FIG. 8  is an exploded rear perspective view of the clamping device of  FIG. 7 .  
         [0103]      FIG. 9  is an exploded view similar to  FIG. 7  but omitting the front plate, gaskets and fasteners.  
         [0104]      FIG. 10  is a front elevational view of the clamping device of  FIG. 9 , showing it installed on its fibre linear tensile element.  
         [0105]      FIG. 11  is a perspective view of a building showing an early stage of a method in accordance with the present invention of installing a second embodiment of a panel system in a building.  
         [0106]      FIG. 12  is a perspective view showing the completion of the installation method of  FIG. 11 .  
         [0107]      FIG. 13  is a perspective view of a building showing a third embodiment, wherein two panel systems in accordance with the present invention are installed spaced apart to provide a thermal buffer therebetween.  
         [0108]      FIG. 14  is a perspective view of a building incorporating a fourth embodiment of a panel system in accordance with the present invention and showing how the condition of the panel system may be remotely monitored.  
         [0109]      FIG. 15  is a perspective view of a panel system in accordance with a fifth embodiment of the present invention wherein the panel system is provided as a roof of a building. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0110]     In relation to the first embodiment of the present invention shown in  FIGS. 1-10 , a building  1  comprises floor slab  11 , a roof  12  and intermediate floors  13  supported on columns  14 . The illustrated front face of the building is flat and is having a panel system in accordance with the present invention fitted thereto. The end objective is to fit a glazed curtain wall  80  to the front face of the building.  
         [0111]     The panel system comprises fibre linear tensile elements  2 , clamping devices  3  and glazing panels  4 . Additionally, each fibre linear tensile element  2  has upper and lower termination devices  5 ,  6  to enable it to be attached to the building  1 .  
         [0112]     As shown in  FIGS. 3-5 , each termination device  5 ,  6  comprises an anchor bracket  51 ,  61  which is fixed to the building  1  and an end termination  52 ,  62  which is fixed to the end of the fibre linear tensile element  2 . An adjustment nut  53 ,  63  enables the position of the end termination  52 ,  62  to be varied relative to the static position of the anchor bracket  51 ,  61 .  
         [0113]     The front face of the building has been designed to receive a rectangular matrix of square glazing panels  4  arranged into rows and columns. The fibre linear tensile elements  2 , clamping devices  3 , and upper and lower termination devices  5 ,  6  provide a support structure for the glazing panels  4 .  
         [0114]     The design is such that a fibre linear tensile element  2  is to be positioned behind each inter-panel joint between adjacent vertical columns of the panels, and also at the left end and right end of the curtain wall.  
         [0115]     In a factory away from the building site, the appropriate number of fibre linear tensile elements  2  are produced with the correct lengths based on the vertical separation between the floor slab  11  and the roof  12 . Each fibre linear tensile element  2  also has fitted to it the appropriate number of clamping devices  3  at the correct positions along its length, and the end terminations  52 ,  62  of the upper and lower termination devices  5 ,  6 .  
         [0116]     The pre-prepared fibre linear tensile elements  2  are then delivered to the building site, such as on the pallet  71  illustrated in  FIG. 1 .  
         [0117]     The anchor brackets  51  are fitted under the front lip of the roof  12  along the front face of the building. The regular spacing between the anchor brackets  51  corresponds to the width of the glazing panels  4 .  
         [0118]     Similarly, the lower anchor brackets  61  are fitted along the front edge of the floor slab  11  with a uniform spacing corresponding to the width of the panels  4 .  
         [0119]     Note that, for the sake of clarity, not all of the anchor brackets  51 ,  61  are individually labelled in the figures.  
         [0120]     Then, starting at the right-hand end of the curtain wall as shown in  FIG. 1 , the pre-prepared fibre linear tensile elements  2  are erected. In  FIG. 1 , most of the erection operation has taken place. In relation to the leftmost fibre linear tensile element  2 A, it is shown being lifted using an electric winch  72  which has its winch cable  73  attached to the upper end termination  52 . The end termination  52  is fixed to the anchor bracket  51  by using nut  53 . At the bottom end, the end termination  62  is fitted to its anchor bracket  61  by using the nut  63 . Thus the fibre linear tensile element  2 A is installed in position, next to the already-installed fibre linear tensile element  2 B.  
         [0121]     As shown for fibre linear tensile element  2 B, the height of the first clamping device  3 B 1  is checked with a laser level  74 . If necessary, the adjustment nuts  53 ,  63  at the top and bottom ends are used to move the fibre linear tensile element  2 B up or down, as required, to position the clamping device  3 B 1  at the correct height for the curtain wall. Then, the adjustment nuts  53 ,  63  are used to tension up the fibre linear tensile element  2 B without significantly altering the height of the clamping device  3 B 1 .  
         [0122]     Now referring to  FIG. 2 , the installation method continues with upper and lower glazing profiles  75 ,  76  being installed just in front of the anchor brackets  51 ,  61  along, respectively, the undersurface of the front lip of the roof  12  and the front edge of the floor slab  11 .  
         [0123]     The glazing panels  4  are brought to site and are installed in position using an installation vehicle  77  which has an articulated arm at the end of which are glazing suction pads. Each glazing panel  4  is a double-glazed unit of two glass sheets with a perimeter gasket and a (front) finishing plate. For a particular column of the curtain wall, the bottommost glazing panel  4  is inserted into position with its lower edge fitted into the lower glazing profile  76 . The two upper panel corners are gripped by the first clamping devices  3 A 1 ,  3 B 1  of the adjacent two fibre linear tensile elements  2 A and  2 B using the clamping technique that will be described in more detail hereinafter. The next panel  4  in the column is then lifted into position, and its bottom corners are fixed to the clamping devices  3 A 1 ,  3 B 1  and its top corners are fixed to the clamping devices  3 A 2  and  3 B 2 . The process is then repeated until all of the panels  4  in the particular column have been installed, with the top edge of the topmost panel being fitted into the upper glazing profile  75 .  
         [0124]     Vertical and horizontal rear gaskets are then installed along the inter-panel joints. A workman is shown in  FIG. 2  installing a rear vertical gasket  78 . A workman  79  then injects sealant into the inter-panel joints of the front face of the completed curtain wall  80 .  
         [0125]     If the (maximum) deflection of the curtain wall  80  out of its plane exceeds a predetermined threshold value under a particular (wind) loading, the tensioning of the fibre linear tensile elements  2  may be increased using the adjustment nuts  53 ,  63  until the deflection has been reduced to an acceptable value.  
         [0126]     Referring now to  FIGS. 3-5 , the fibre linear tensile element  2  is shown as having a cylindrical core  21  of polymer filaments or fibres which provide the structural or tensile strength. Exemplary materials include aramid, LCP (such as Vectran™) or PBO (such as Zylon™).  
         [0127]     The fibre linear tensile element  2  includes a cover or sheath  22  which is made of, for example, polyester and which may be coloured or patterned to suit the particular installation requirements.  
         [0128]     Additionally, a further cover (not shown) could be applied at local positions along the length, or along the full length of the fibre linear tensile element, and could comprise a steel mesh co-extruded in a polymer and/or additional fireproofing materials.  
         [0129]     Running along the central axis of the fibre linear tensile element  2  is an optical fibre  23  which performs a monitoring function, as will be described later. The upper end termination  52  comprises a clamp portion  521  which receives and is securely clamped onto the upper end of the fibre linear tensile element  2 . Above this is a threaded portion  522 . Similarly, the lower end termination  62  comprises a clamp portion  621  and a threaded portion  622 .  
         [0130]     Within the clamp portion  521 , the upper end of the fibre linear tensile element  2  spreads apart, enabling the optical fibre  23  to be led out the side of the clamp portion  521 . Similarly, at the bottom end, the optical fibre  23  is freed from within the cylindrical core  21  and sheath  22  and is led out through the side of the lower clamp portion  621 . Thus the optical fibre  23  may be connected into a monitoring circuit, as will be described later.  
         [0131]     Considering  FIGS. 4 and 5 , the thread of the upper adjustment nut  53  cooperates with the threaded portion  522  to permit longitudinal adjustment of the position of the clamp portion  521  relative to the anchor bracket  51 . At the other end of the fibre linear tensile element  2 , the adjustment nut  63  may be rotated on the threaded portion  622  in order to adjust up and down the position of the clamp portion  621  relative to the anchor bracket  61 . One or both of the adjustment nuts  53 ,  63  may be operated to increase or reduce the tension of the fibre linear tensile element  2 . By careful synchronised adjustment of the two nuts  53 ,  63 , it is also possible to maintain the existing tension of the fibre linear tensile element  2  whilst adjusting up or down the position of the fibre linear tensile element  2  and the clamping devices  3  that it carries.  
         [0132]     A representative clamping device  3  will now be described with reference to  FIGS. 6-10 . At the rear of the clamping device is a two-part duct  31  comprising a channel portion  311  and a removable cover plate  312 . The fibre linear tensile element  2  passes through the bore of the duct  31  and is securely gripped by clamping structure  313  inside the duct. Four releasable fasteners  314  secure the cover plate  312  to the channel portion  311 , and produce a size and configuration of the bore through the duct such that the clamping structure  313  securely clamps the clamping device  3  onto the fibre linear tensile element  2 .  
         [0133]     In front of the duct  31  is a clamping arrangement for clamping the corners of four panels  4 . This clamping arrangement comprises a back plate  32 , a bracket  33 , a front plate  34  and two gaskets  35  which are interposed between the front and back plates  32 ,  34 .  
         [0134]     The back plate  32  and bracket  33  are most clearly shown in  FIGS. 9 and 10 .  
         [0135]     All of the structural components of the clamping device  3  are fabricated from metal, and the back plate  32  is molded to be integral with the channel portion  311 . The bracket  33  is molded integrally with the back plate  32  and projects forwards from the front face thereof. The bracket  33  comprises a horizontal flange  331  at the middle of which are an upper divider  332  and a lower divider  333 . The top face of the flange  331  is split into left and right seat portions  334 ,  335  by the upwardly-projecting divider  332 . The bottom face of the flange  331  is split into left and right guide portions  336 ,  337  by the downwardly-projecting divider  333 .  
         [0136]     The left seat portion  334  with the upper divider  332  and the back plate  32  define a recess or socket for receiving a corner of a panel  4 . Similarly, the right seat portion  335  with the upper divider  332  and the front face of the back plate  32  define another recess or socket.  
         [0137]     Again, each one of the left and right guide portions  336 ,  337  with the lower divider  333  and the back plate  32  define a respective recess or socket.  
         [0138]     In use, the clamping device  3  is positioned at a connection node of the panel skin of the curtain wall, and the four recesses or sockets receive respective corners of the four panels at the connection node. The two upper panels will sit on the left and right seat portions  334 ,  335 . The tops of the two lower panels will touch or be positioned close to the left and right guide portions  336 ,  337 .  
         [0139]     The thickness (vertical height) of the flange  331  defines the size of the inter-panel gap between the two upper panels and the two lower panels.  
         [0140]     The common thickness (horizontal width) of the upper and lower dividers  332 ,  333  defines the size of the inter-panel gap between the two left panels and the two right panels.  
         [0141]     The front plate  34  is releasably fastened onto the front face of the bracket  33  by two fasteners  36  each of which extends through a smooth aperture  321  in the back plate  32  and then through smooth apertures  351  in the two gaskets  35  before threadedly engaging with a threaded aperture  341  in the rear face of the front plate  34 .  
         [0142]     The correct positioning of the front plate  34  is ensured by two studs  342  which project into respective sockets  338  in the front face of the flange  331 .  
         [0143]     When the panels  4  are being installed, the front plate  34  and the frontmost one of the two gaskets  35  are initially left off. Of the four panels at the connection node defined by the clamping device  3 , the top right-hand corner of the lower left panel is located by the left guide portion  336  and the lower divider  333 . The top left-hand corner of the lower right panel is located by the right guide portion  337  and the lower divider  333 . The two lower panels are then temporarily held in position by locking arms (not shown) which are fitted into apertures  315  aligned along the vertical inter-panel joint.  
         [0144]     The two upper panels of the group of four panels  4  are then fitted. The bottom right-hand corner of the upper left panel is located against the left seat portion  334  and the upper divider  332 . The bottom left-hand corner of the upper right panel is located against the right seat portion  335  and the upper divider  332 . The two upper panels may then be temporarily held in position by further locking arms (not shown) inserted into respective ones of apertures  316  in the upper part of the front face of the duct  31 .  
         [0145]     The frontmost one of the two gaskets  35  is then positioned on the bracket  33  against the front faces of the four panels  4 . The front plate  34  is then fitted onto the bracket  33 , with the studs  342  locating in the sockets  338 . The two fasteners  36  are then inserted through the apertures  321 ,  351  and engage with the threaded apertures  341  in the rear of the front plate  34  in order to clamp the front plate  34  in position, and thereby resiliently clamp the four panels  4  between the gaskets  35 . The temporary locking arms may then be removed from the apertures  315 ,  316  and sealant applied to the inter-panel joints. The end result is as shown in  FIG. 6 .  
         [0146]     As shown in  FIG. 10 , the length Y 1  of the duct  31  is at least three times the height Y 2  of the back plate  32  in order to reduce unwanted twisting of the clamping device  3  on the fibre linear tensile element  2  about the axis perpendicular to the plane of the paper of  FIG. 10 .  
         [0147]     Also, the width X 1  of the back plate  32  is about 80% of the length Y 1  of the duct  31 . As may be seen in  FIG. 10 , this gives the clamping device  3  a cross-like appearance.  
         [0148]     The front plate  34  and the two gaskets  35  are substantially the same shape and size as the back plate  32 . The generally cross-like appearance as shown in  FIG. 10  means that the major components of the clamping device  3  are aligned either generally along a vertical inter-panel joint (in the case of the duct  31 ) or generally along a horizontal inter-panel joint (in the case of the back plate  32 , front plate  34  and gaskets  35 ). This helps to make the clamping device less visually intrusive.  
         [0149]     The front plate  34  and the back plate  32  are each wider than the bracket  33 . Consequently the two apertures  321  in the back plate  32  are positioned laterally outwardly of the left and right ends of the flange  331  of the bracket  33 , rather than in the flange  331  itself. Consequently, the thickness of the flange  331  is substantially the same as the diameter of the shanks of the fasteners  36 . This enables the thickness of the horizontal inter-panel joint to be kept fairly small (and thus visually attractive) compared with the thicker joint that would be needed if the apertures  321  were to be provided in the flange  331 . As it is the bracket  33  that projects through the panel skin, it is the dimensions of the bracket which determine the thicknesses of the vertical and horizontal inter-panel joints. Generally speaking, these thicknesses should be kept fairly small, as long as the bracket  33  is not made so thin as to become structurally too weak.  
         [0150]      FIGS. 11 and 12  show a second embodiment of the present invention. Similar reference numerals are used in the second embodiment as for the first embodiment, in order to avoid repetition.  
         [0151]     The second embodiment differs from the first embodiment mainly in that the curtain wall  80  is curved, in that it is sinuous along its length.  
         [0152]     The individual square panels  4  are still planar because the curvature along the curtain wall  80  is gentle enough to permit planar panels to be used.  
         [0153]     As shown in  FIG. 11 , the second embodiment includes a monitoring device  81  connected to form monitoring circuits with the optical fibres  23  of the fibre linear tensile elements  2 . The optical fibres  23  are connected in parallel, so that any fall-off in tension of a particular fibre linear tensile element  2  may be detected and that particular fibre linear tensile element  2  identified.  
         [0154]     With regard to the third embodiment shown in  FIG. 13 , there are two curtain walls each using the panel system of the present invention. There is the outer curtain wall  80  and an inner curtain wall  82 . Each wall uses glass panels  4 , so it is possible to see through both of the walls. Struts  83  extend between the two walls  80 ,  82  in order to maintain the spacing between the two walls. The struts could also support a walkway positioned in the gap between the two walls, or components (such as lighting, blinds etc.) could be attached to the struts  83  in order to be positioned in the gap between the walls.  
         [0155]     There is an air entrance (not shown) leading into the gap and an air exit (not shown) for ducting air out of the gap, so that overall the gap between the two walls  80 ,  82  can function as a flue. This may be useful when, for example, the two walls  80 ,  82  are south-facing because the flue will help to maintain a cool climate within the building in the summer. In other words, the two walls act as a thermal buffer between the external environment and the interior  84  of the building. The gap between the two walls functions as a convection-ventilated flue.  
         [0156]     Perhaps if the struts  83  are not present, or else are capable of permitting some variation in their length, flexing of the outer wall  80  relative to the inner wall  82  could be used to some extent at least to “pump” the air through the flue. It may usually be necessary to supplement this pumping with a conventional fan that can be controlled by the building&#39;s control system.  
         [0157]     For a pair of walls extending along the long facade of a building, there will usually be a plurality of air entrances into the flue and a plurality of air exits, spaced at positions along the building facade.  
         [0158]     With regard to the fourth embodiment shown in  FIG. 14 , this illustrates how the optical fibre monitoring device  81  may output the information regarding the state of the tensioning of the fibre linear tensile elements  2 . It could output information, such as an alarm signal indicating that a particular fibre linear tensile element  2  has an unacceptably-low tension, directly to a computer  85  over a wireless link  86 . The computer  85  could be elsewhere in the building or elsewhere on the site, and might be part of the overall building control system for managing the functioning of the building (e.g. heating and lighting).  
         [0159]     Alternatively or additionally, the information output from the monitoring device  81  could be transmitted over the internet  87  to a computer  88  which could be anywhere in the world.  
         [0160]     We expect that most commercial embodiments of the present invention will involve the panel system providing a panel skin which is a wall, as shown in the embodiments of FIGS.  1  to  14 . Alternatively, the panel skin could be provided as the roof of a building as shown in  FIG. 15 . For the fifth embodiment of  FIG. 15 , the same reference numerals are used as for the analogous components of the preceding embodiments. The main difference is that the fibre linear tensile elements  2  extend between a pair of generally parallel roof beams  15 ,  16 . Instead of glazing profiles  75 ,  76  being used (as in the earlier curtain wall embodiments), the roof  89  formed by the panel skin has its longitudinal edges supported on and sealed by longitudinal strips  17 ,  18  which space the roof  89  slightly above the top surfaces of the roof beams  15 ,  16 . The arrangement of fibre linear tensile elements  2  and the longitudinal strips  17 ,  18  may be such as to impart a slight slope to the roof  89 , e.g. for water drainage.  
         [0161]     It will be appreciated that the above description is non-limiting and refers to the currently-preferred embodiments of the invention. Many modifications may be made within the scope of the invention. Although features believed to be of particular significance are identified in the appended claims, the applicant claims protection for any novel feature or idea described herein and/or illustrated in the drawings, whether or not emphasis has been placed thereon.