Year: 1886

page_text: I, GEORGE GATTON MELHUISH HARDINGHAM, of 191 Fleet Street, in the County
of Middlesex, Civil Engineer and Patent Agent, do hereby declare the nature of
this invention as communicated to me from abroad by La Société Anonyme de
Sclessin, of Sclessin, in the Kingdom of Belgium, Iron Manufacturers and Con-
structors, to be as follows:-
This invention has for its objects to simplify the construction of iron and similar
bridges of the lattice or open girder type, and to afford facilities for the transport
and erection of such bridges, as also for their dismounting and removal.
The invention consists primarily in constructing the girders, as also the piers,
for such bridges of elements which are of peculiarly simple construction, are
practically repetitions of one another as regards design, and which are adapted for
being employed in conjunction with one another according to the number required
to form girders and piers of the required lengths and to withstand the strains to
which they may be subjected.
An element such as above referred to consists of a series of identical sub-elements,
each of which is in the form of an equilateral triangle and which may be composed
of bars or angle irons, or several angle irons fastened together, or angle irons in
conjunction with bars, according to the degree of strength and rigidity deemed
appropriate. The sub-elements of equilateral form when arranged with their
apices alternately upwards and downwards and fastened together side by side
constitute an element; suitable lengths of such elements being in turn arranged
longitudinally with one another and fastened together, as hereinafter more fully
explained, to form the girders or piers of the bridge. In order to provide a rect-
angular extremity to such an element, the terminal sub-element may be modified
by bisecting the base of the triangle representing the sub-element in its normal
condition and connecting its opposite apex with the point of bisection.
In forming tubular girders, two elementary girders of the kind above described
are arranged parallel to one another and at a distance apart equal to their height.
Two similar clements, placed at the same distance apart but arranged horizontally,
are then respectively connected with the bottom and top edges of the vertical

page_text: elements; and a tubular girder of equilateral and rectangular cross section results.
Such a girder possesses great rigidity and is advantageous as regards manufacture
in consequence of none of the diagonals, crossing one another. To further insure
such a girder maintaining its proper form when subjected to severe strains, it may
be internally braced by cross-ties connecting its diagonally opposite angles. Such
diagonal braces may be formed of single angle-irons, or may be built up as pre-
viously mentioned with reference to the construction of the elements constituting
the four sides of the tubular girder; and the said braces may be readily disposed
in such a manner as to avoid one another at the points of their intersection.
All the sub-elements being identical in design, or nearly so, it results that the
preparation of the materials for a bridge constructed on the system described is a
matter of simplicity, economy, and expedition; and that even these parts may be
manufactured beforehand and kept in stock.
I have described how elements for girders are formed from sub-elements, and
how these elements are employed with one another, as also in the constitution of
tubular girders; but it may be desirable further to point out that the tubular
girders themselves may be employed in lateral conjunction with one another to
form compound girders for use as piers, or for spanning the spaces intervening
between piers.

page_text: I, GEORGE GATTON MELHUISH HARDINGHAM, of 191, Fleet Street, in the County
of Middlesex, Civil Engineer and Patent Agent, do hereby declare the nature of
this invention and in what manner the same is to be performed, as communicated
to me from abroad by La Société Anonyme de Sclessin, of Sclessin, in the Kingdom
of Belgium, Iron Manufacturers and Constructors, to be particularly described and
ascertained in and by the following statement:-
To render this invention readily intelligible, I will describe it with reference to
the annexed drawings.
Figure 1 shows an equilateral triangle. By grouping together a certain number
of equilateral triangles, in the manner shown in Figure 2, an outline of a rigid
girder is obtained which may be of any desired length. If moreover an equilateral
triangle equal to any of the triangles in Figure 2 be bisected (by letting fall
a perpendicular from any of its angles to the subtending side, see Figure 3) two
rectangular triangles, such as shown in Figure 4, are obtained. These triangles in
juxtaposition with the equilateral triangles at the ends allow the outline of the
girder, shown in Figure 2, to be finished off by right-angles, if desired. If more-
over it be assumed that the sides of the triangular "links are made of angle-irou,
it is easy to unite there with in a variety of ways either other angle-irons (see
Figures 5 to 8) or flat pieces of iron (see Figures 9 to 15) so as to vary the sectional
area of the elements in each "link" according to the strain to be borne thereby
and in accordance with the direction of such strain.
"
If now two girders of equal height be placed in parallel vertical planes, as
shown by way of example in Figures 16 and 17, the horizontal distance between
the two parallel planes being equal to the height common to the two girders (the
girder shown by Figure 17 being in front of that corresponding with Figure 16)
then it will be permissible to connect the two girders by ties in the upper and the
lower horizontal planes respectively occupied by the top and bottom of said girders
and this can be effected by diagonals equal to those of the girders themselves
and arranged in the same manner as those of said girders. (If Figures 16 and 17
be regarded as plans, instead of elevations, then Figure 16 becomes a diagram of
the arrangement of ties in the upper horizontal plane, and Figure 17 a diagram
of the arrangement of ties in the lower horizontal plane). It follows that if on a
plan be laid off the four faces of the tubular girder of square transverse section,
such as shown in Figure 18, a network of triangles is obtained such as represented
by Figure 19; that is to say, a network of triangles all joining one another by
their apices. (To obtain this Figure 19 one must assume the tubular girder to be
opened out from the edge which separates the lower and rear sides of said girder).
A remarkable feature of the solution which we have above described is that
absolute rigidity is afforded on the four sides of the girder without any one of the
diagonals crossing any other, and no other system of "links" (not formed by
equilateral triangles) possesses this property.
:
It may be added that the tubular girder of square transverse section hereinbefore
described becomes absolutely unalterable in shape, within the limits of resistance
of its elements, if it be provided with cross diagonals placed transversely, as
a

page_text: indicated in the end view Figure 20. This may be easily accomplished and these
transverse diagonals may be the same angle-irons or groups of angle-irons as used
for the faces of the girder, and the corner braces can readily be arranged for this
purpose. It may be here noted that two of these transverse diagonals cannot be
placed in the same plane if they are to terminate, as they should, at the points of
union in the trellis. By referring to Figure 19 it will be understood that if the
four faces are folded again so as to reform the tubular girder of square section,
there will be only two points of union in a diagonal line on a given transverse
plane; but this is of little consequence, on the one hand, because the transverse
diagonals being angle-irons or groups of angle-irons, a single diagonal will be
sufficient to insure permanency of shape, and on the other hand, because it is easy
to place the second diagonal crosswise to the first half a "link" behind the latter
as will be hereinafter seen.
From what has been stated it will be perceived that in this system angle-iron
and flat bars of uniform dimensions only will require to be used; these being
pierced with holes beforehand, the distance between such holes being invariable.
Thus it will only be necessary to prepare beforehand and to keep in stock a very
small number of elements which are always of the same description.
From the foregoing it likewise results that by the juxtaposition or superposition
of a certain number of tubular girders, such as hereinbefore described, composite
tubular girders may be obtained, adapted for use either horizontally or vertically
(in the latter case in the shape of columns). Figures 21 to 23 give an idea of
such combinations, which, as will be readily understood, are capable of endless
variation.
I will now consider which are the elements by means whereof the combinations
just mentioned may be carried out, and more particularly the joints represented in
elevation and transverse section in Figures 24 and 25. The number of these
elements is nine and although a greater number may be devised, these will be
sufficient in case of necessity. They are:-Two lengths of angle-iron of equal
section, Figures 26 and 27; three flat bars in two sections, Figures 28, 29 and 30;
three braces for the longitudinal faces, Figures 31, 32 and 33; one brace for the
transverse diagonal ties, Figure 34. There is thus according to this system great
facility for keeping stock, for transporting, fitting up and taking down without the
use of any special tool with the exception of a spanner for tightening the nuts,
rivetting being done in the usual manner where required. Tables prepared before-
hand serve to indicate what will be, for a given load to be carried by one or more
girders, the number to be employed for each kind of elements; and the arrange-
ment of these elements is shewn by a diagram annexed to the said tables. Lastly,
it will be seen that bridges constructed according to this system may be readily
erected without requiring a temporary bridge, and without platforms, rollers or
other plant.
From the preceding, it will be perceived that girders either simple or composite
may be obtained intended for use in the construction of bridges either for foot-
passengers, or for foot-passengers and vehicular traffic or for railways. In the
latter case, the width of gauge (which as is well known differs in various countries)
will be the basis for determining the best length of the sides of each equilateral
triangle to be used in each case. For the more usual gauges, the calculated weight
of each element is such as to permit of easy manipulation.
Figures 35 to 40 represent, to an enlarged scale, a simple girder constructed
according to this invention. Figure 35 is an elevation of the rear girder, and
Figure 36 a corresponding end view upon which the angle-irons serving as counter
stays A B are partly indicated. Figure 37 is an elevation of the front girder and
Figure 38 a corresponding transverse section on line xy, of Figure 37. Figures 39
and 40 are respectively plans of the upper and lower counter stays, In Figures 37
and 39 the braces CDE have been added so as to indicate (as "joining pieces")
how to add to one simple girder, either vertically or horizontally, other simple
girders so as to produce composite girders of any desired section.

page_text: Finally, it may be added that ordinarily the braces are not included in estimating
the section of the longitudinal girders, although it would be reasonable to take
account of these braces, provided that their dimensions be such as to enable them
to resist oblique strains, which is the case in the system hereinbefore described.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, I claim :—
The use in combination and in the construction of tubular girders of square
cross section (which are to be employed either as simple girders or as compound
girders, and either placed horizontally, vertically or even obliquely) of a sinall
number of elements, which are always of a like kind and are formed by angle-
pieces or a combination of angle-pieces; by combination of angle-pieces and of
flat pieces; and by braces of suitable shape, in such a manner that the four faces
of every tubular girder of square section are formed by triangular equilateral
"links" which adjoin one another at their apices; the said four faces of every
tubular girder of square section having thus a proper absolute rigidity, the whole
construction being likewise absolutely free from liability to alter its shape (the
said construction consisting of said four faces) such non-liability to alteration of
shape being ensured by transverse diagonals, which may be arranged crosswise at
a distance of half a "link" from one another, the aforesaid elements being of such
convenient transverse section or shape as will enable them to resist tension or
compression, as well as oblique strains, as may be required; the whole as and for
the purposes hereinabove described and illustrated in the accompanying drawings.
Dated this 29th September 1886
G. G. M. HARDINGHAM.