Structural glass assemblies

A structural glass assembly in which one or more glass plates are secured by an attachment device to an adjacent element, the attachment device comprising a plate member partially overlying an edge region of the glass plate on one side only thereof and extending parallel to the plane of the plate so as to form a connection between the glass plate and the adjacent element, the plate member being spaced from the glass plate and secured to the edge region of the plate so as to permit the edge region to flex inwardly or outwardly when subjected to load.

BACKGROUND OF THE INVENTION 
The present invention relates to structural glass assemblies including, for 
example, suspended glass assemblies and fittings therefor. 
One type of structural glass assembly is known as a suspended glass 
assembly. A suspended glass assembly may consist of a matrix of specially 
processed and tempered glass plates bolted together at their corners by 
means of small metal fittings. The joints between the glass plates are 
usually sealed with a silicone sealant and tempered glass stabilisers are 
used at each vertical joint to provide lateral stiffness against wind 
loading. The assembly is usually constructed in situ suspended from a 
building structure by hangers bolted along its top edge and can be sealed 
to the building in peripheral channels. 
Hitherto it has been considered necessary to use fittings comprising spaced 
metal plates which overlap in parallel relationships so as to clamp the 
corners of four adjacent glass plates in the assembly between the metal 
plates, the overlapping area of glass and metal serving to support the 
glass plates. Typically known fittings include a flat brass plate which 
can be bolted to four corner regions of adjacent glass plates with the 
flat brass plate lying flat against the outerside of the glass assembly. 
At the same time, two substantially L-shaped plates are located on the 
other side of the glass assembly one limb of each L-shaped plate being 
bolted to the corner regions on the inner side of the adjacent glass 
plates while the other limbs of each L-shaped plate are arranged to 
sandwich between them a glass stabiliser which extends perpendicular to 
the face of the suspended assembly. 
We have found that whilst such known types of fitting apparently support 
the corners of the glass plates and strengthen the structure, stronger 
glass assemblies, whether they be suspended or otherwise, can be produced 
by avoiding sandwiching the corners of the glass plates between metal 
plates. The sandwiching of the corners of the glass plate may restrict the 
extent to which the corners can flex when high wind loads act on the glass 
assembly. Such restriction can cause high stress in the corners of the 
glass plates and this can give rise to constraints on the areas of glass 
plates which can be safely used in such glass assemblies. 
SUMMARY OF THE INVENTION 
The present invention provides a structural glass assembly in which a glass 
plate is secured by means of an attachment device to an adjacent element 
which is spaced from an edge of the glass plate, said attachment device 
comprising a plate member partially overlying an edge region of the glass 
plate on one side only thereof and extending parallel to the plane of the 
glass plate so as to form a connection between the glass plate and the 
adjacent element, said plate member being spaced by spacer means from said 
one side of the glass plate and secured to the edge region of the glass 
plate so as to permit the edge region to flex inwardly or outwardly 
relative to the plate member when the glass plate is subjected to load. 
Preferably the plate member is flexible so as to minimise resistance to 
flexing of the edge region of the glass plate when subjected to load. The 
degree to which the glass plate will flex relative to the flexible plate 
member is dependent on the relative flexibility of the glass and flexible 
plate member. 
The invention is particularly applicable to a structural glass assembly in 
the form of a suspended glass assembly comprising a matrix of suspended 
glass sheets. 
Normally suspended glass assemblies comprise glass plates that are coplanar 
and joined together at their corners. They may include stabilising members 
comprising vertically extending glass plates lying perpendicular to the 
plane of the matrix and having vertical edges adjacent vertical junctions 
in the matrix. 
In a suspended glass assembly the aforesaid adjacent element may comprise 
one or more glass plates in the matrix of glass plates. 
Alternatively the adjacent element may comprise part of a frame or other 
building structure to which the glass plate is attached. In this case the 
supporting structure is not generally made of glass but can be of any 
structural material, for example, brick or concrete, having sufficient 
strength to take the reactive load from the glass plate. 
The invention includes a suspended glass assembly in which two coplanar 
glass plates are joined together by an attachment device comprising a 
plate member partially overlying an edge region of each glass plate on one 
side only if the glass plates and extending parallel to the glass plates 
and forming a connection between them, the plate member being spaced by 
spacer means from the said one side of the glass plates and secured to the 
edge regions of the glass plates so as to permit the edge regions to flex 
inwardly or outwardly relative to the plate member when the glass plates 
are subjected to wind load. 
The invention includes a suspended glass assembly as aforesaid in which 
four adjacent coplanar glass plates are arranged with one corner of each 
of the glass plates forming a common junction with the other three plates, 
said four glass plates being similarly joined together by the said plate 
member. 
The suspended glass assembly may include more than four coplanar glass 
plates, each junction of four plates being provided with an attachment 
device as aforesaid. 
Preferably the plate member used in the present invention is secured to the 
adjacent glass plate or plates by bolts passing through holes in the plate 
member and in the edge regions, usually the corners, of the glass plates. 
The attachment device preferably includes means for attaching the plate 
member to stabilising means for stabilising the matrix of glass plates in 
a direction perpendicular to the plane of the matrix. 
The stabilising means may comprise one or more glass plates extending 
perpendicular to the plane of the matrix. 
Preferably the means for attaching the plate member to the stabilising 
means comprises a link member having means for attachment to an edge of a 
stabilising glass plate and means for attachment to the plate member at a 
position intermediate the connections of the plate member to each of the 
glass plates in the matrix. Preferably the means for attachment to an edge 
of a stabilising glass plate comprises two plates bolted together on 
opposite sides of the stabilising glass plate. 
Preferably the link member is attached to the centre of the plate member. 
Conveniently the glass plates in the matrix are bolted to the plate member 
and non-metallic gaskets and bushes are inserted to prevent metal to glass 
contact. 
The plate member is preferably sufficiently flexible to allow the glass 
plates to flex so as to avoid undue concentration of stresses in the 
corner portions of the glass plates. On the other hand the flexible plates 
must be made of a material that has dimensions with sufficient strength to 
resist the wind loading forces. 
Preferably the flexible plate member is manufactured from a material which 
when tested in accordance with the procedure set out in a publication 
issued by the British Standard Institution entitled "BS18 "Tensile Testing 
of Metals: Part 2-Steel": 1971", has a lower yield stress greater than 350 
MN/m.sup.2. Some suitable materials may not exhibit a lower yield of 
stress and when tested in accordance with the procedure set out in the 
above publication exhibit a 0.5% total elongation proof stress which is 
greater than 350 MN/m.sup.2. Conveniently the material used for the 
flexible plate is steel, preferably a steel of grade 080A52 as specified 
in the publication "BS970 "Specification for Wrought Steels": Part 5 
"Carbon and Alloy Springs Steels for the Manufacture of hot Formed 
Springs": 1972" as issued by the British Standard Institution. 
Advantageously the steel of grade 080A52 is quenched and tempered prior to 
use so as to increase its lower yield stress to over 1000 MN/m.sup.2. The 
steel can, for example, be quenched from 840.degree. C. and tempered at 
400.degree. C. 
Advantageously the thickness of the flexible plate member is less than 12 
mm as thicknesses above 12 mm tend to restrict the flexibility of the 
plate. 
The present invention also provides an attachment device for use with glass 
assemblies, in which the device comprises a flexible plate manufactured 
from a material having a lower yield stress or a 0.5% total elongation 
proof stress, greater than 350 MN/m.sup.2, means for connecting the 
flexible plate to the corner portion or portions of a glass plate or 
plates and means for connecting the flexible plate to a supporting 
structure. 
Conveniently the device has means which can be fitted to the centre of the 
flexible plate and which is adapted to receive an edge region of a glass 
stabilising plate. The attachment is so adapted that the glass stabiliser 
can be arranged in a plane which passes through the vertical joints 
defined between glass plates in a suspended glass assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The example of FIGS. 1 and 2 relates to a suspended glass assembly of the 
type in which a matrix of tempered glass plates is hung from a building 
structure and sealed together to form a glass facade. In such an assembly, 
the matrix may include many glass plates forming a plurality of vertical 
and horizontal rows of glass plates. The glass plates are arranged so that 
the corners of four adjacent plates meet at a common junction as is shown 
in FIG. 1. The plates are coplanar and spaced apart by a small distance, 
for example 5 mm. The corners of each plate of a set of four which meet at 
a common junction are secured together by an attachment device and FIGS. 1 
and 2 illustrate the construction and attachment of such a device at one 
junction in the assembly. It will be understood that similar attachment 
devices may be coupled at other junctions of the glass plates in the 
assembly. 
In the arrangement shown in FIG. 1, four tempered glass plates 11, 12, 13 
and 14 meet at a common junction where they are secured together by an 
attachment device in the form of a flat rectangular plate 15. The plate in 
this example comprises a 6 mm thick flexible planar plate manufactured 
from spring steel having a lower yield stress greater than 350 MN/m.sup.2. 
The plate partially overlies an edge region of each glass plate and is 
formed with four bolt holes 16 each arranged to overlie a corner region of 
one of the glass sheets. The plate is also formed with a central aperture 
17. The plate 15 is arranged to lie parallel to the inner face only of the 
matrix of glass plates and no similar attachment device is provided on the 
outer surface of the matrix of glass plates. In FIG. 1, the plate 15 is 
shown in position but not yet attached to the glass plates. The manner of 
attachment is shown fully in FIG. 2. 
The plate 15 is bolted to each of the glass plates 11, 12, 13 and 14 by a 
bolt 18 passing through the respective aperture 16 in the plate 15 and 
through an aligned hole in the corner region of the associated glass 
plate. An aluminium washer or boss 19 is located between the plate 15 and 
each of the glass plates. A further aluminium washer or boss 20 is 
inserted between each of the glass plates and the head 21 of each of the 
bolts on the outer face of the matrix of glass sheets. A gasket 22 of 
rubber, plastics material, or other non-metallic material is inserted 
between each of the washers 19 and 20 and the adjacent glass surfaces so 
as to prevent metal to glass contact. 
Also a bush (not shown) is located around the central portion of each bolt 
18 to separate that bolt 18 from the glass plate through which it passes. 
As the four corner regions are held together by only the one flexible plate 
15, the corner portions of the glass plates are substantially free to flex 
when the matrix of glass plates is subjected to wind load. 
It is customary in suspended glass assemblies to provide stabilisers in the 
form of glass sheets which extend vertically along a vertical junction in 
the matrix of glass sheets. The sstabilising glass sheets are arranged 
perpendicular to the plane of the matrix so that they resist deflection of 
the matrix in a direction perpendicular to its plane. Such a stabilising 
glass plate is indicated by the reference numeral 25 in FIG. 2. It will be 
understood that a number of such stabilising plates may be provided in the 
suspended glass assembly at suitable vertical junctions in the matrix. 
FIG. 2 shows the manner in which the stabilising plate 25 is secured to 
the plate member 15. The plate 25 is sandwiched between two metal plates 
26 and 27. The plates 26 and 27 are bolted together by means of bolts 28 
passing through apertures in the plates 26 and 27 as well as an aligned 
aperture in the glass plate 25. Gaskets 29 made of rubber, plastics 
material or other non-metallic material are inserted between the plates 26 
and 27 so as to prevent glass to metal contact. Bushes (not shown) located 
around bolts 28 separate the bolts 28 from the plate 25. The plates 26 and 
27 have at their ends adjacent the plate member 15, coupling members 30 
each having a recess 31. A hollow aluminium extrusion 32 is located 
adjacent the central part of the plate member 15 and is secured thereto by 
a doubleheaded bolt 33 which passes through the central aperture 17 in the 
plate member 15. The aluminium extrusion 32 carries a projecting member 34 
the outer ends of which engage the recesses 31. In this way, the plates 26 
and 27 are attached to the plate member 15. The glass stabiliser 25 will 
normally be secured to a supporting structure at some position along its 
height to resist displacement when the suspended glass assembly is 
subjected to wind load. 
FIG. 3 shows an alternative embodiment in which a glass plate 40 is secured 
to a frame member 41 forming part of an adjacent building structure which 
may be made of any suitable building material. In this case, an upper edge 
region of the plate 40 is secured to the frame member 41 by an attachment 
device in accordance with the present invention. The attachment device 
includes a plate member 42 similar to the plate member 15 already 
described with reference to FIGS. 1 and 2. The flexible plate member 42 is 
bolted to the frame member 41 by a bolt 43. The lower edge of the plate 
member 42 has an aperture aligned with a corresponding aperture in the 
upper edge of the plate 40. A bolt 44 passes through the aligned apertures 
and thereby secures the upper edge of the glass sheet 40 to the plate 
member 42. An aluminium washer 46 is located between the glass sheet 40 
and the plate member 42 and a similar aluminium washer 46 is located 
between the outer head of the bolt 44 and the outer face of the glass 
sheet 40. Gaskets 47 of rubber, plastics, or other non-metallic material 
are inserted between the washers 46 and opposing faces of the glass sheet 
40 so as to prevent metal to glass contact. Bushes (not shown) separate 
the glass sheet 40 from the region of the bolt 44 which passes through the 
glass sheet 40. 
The attachment device shown in FIG. 3 is similar to that referred to in 
FIGS. 1 and 2 in that the use of a single flexible plate member on one 
side only of the glass sheet enables the glass sheet to flex under wind 
load. The plate member 42 is formed of similar materials to those already 
referred to. It will be appreciated that in the arrangement shown in FIG. 
3, the plate member 42 may be attached to any suitable edge region of the 
glass sheet 40 and may again be used adjacent corner regions when desired. 
It may also be used to attach a glass plate to any adjacent building 
structure with various relative orientations of both the glass sheeet and 
the adjacent building structure. 
The invention is not limited to the details of the foregoing examples. For 
instance, the aluminium washers referred to in both the examples may be 
replaced by stainless steel, mild steel or brass washers. The shape of the 
washers can be rectangular, circular or of any other desired shape.