IMPROVEMENTS IN SUSPENSION BRIDGES
Year: 1858

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in
the County of Middlesex, and of 166, Buchanan Street, in the City of
Glasgow, North Britain, Gentleman, for the Invention of "IMPROVEMENTS
IN SUSPENSION BRIDGES."-A communication from Freidrich Schnirch, of
Vienna, in the Empire of Austria.
Sealed the 25th June 1858, and dated the 30th April 1858.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson, at
the Office of the Commissioners of Patents, with his Petition, on the
30th April 1858.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, and of 166, Buchanan Street, in the City of Glasgow, North
Britain, Gentleman, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN SUSPENSION BRIDGES," a communication from Freidrich
Schnirch, of Vienna, in the Empire of Austria, to be as follows:-
This Invention relates to a peculiar construction and arrangement of the
suspending chains of suspension bridges, whereby increased rigidity and a
greater span is obtianed, with considerable economy in construction.
According to this Invention, the suspending chains are rendered stiff or rigid
by the application thereto of diagonal braces. Two or more chains are used for
each side of the bridge, such chains being suspended at different elevations, so as
to form concentric curves, and the intervening spaces between these curves are.

page_text: occupied by the diagonal braces above referred to, which are connected at
each end by pins or bolts to the upper and lower chain, and are so arranged
as to subdivide the space between the chains into a succession of triangles
having their apices alternately above and below, whilst the hypothenuse of
each angle is formed by the corresponding link of the upper or lower chain,
as the case may be. The links of the lower chain should, of course, be of a
greater length than those of the upper chain, to allow for the greater radius
of the curve of that chain over that of the upper one.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Henry Johnson in the Great Seal Patent Office on the
30th October 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex, and
of 166, Buchanan Street, in the City of Glasgow, North Britain, Gentleman,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirtieth day of April, in the year of our Lord One
thousand eight hundred and fifty-eight, in the twenty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
John Henry Johnson, Her special license that I, the said John Henry
Johnson, my executors, administrators, and assigns, or such others as I, the
said John Henry Johnson, my executors, administrators, or assigns;
should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for "IMPROVE-
MENTS IN SUSPENSION BRIDGES," a communication from Freidrich Schnirch, of
Vienna, in the Empire of Austria, upon the condition (amongst others) that
I, the said John Henry Johnson, by an instrument in writing under my
hand and seal, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said John Henry Johnson, do hereby
declare the nature of the said Invention, and in what manner the same is

page_text: to be performed, to be particularly described and ascertained in and by the
following statement, reference being had to the accompanying Drawings, and
to the letters and figures marked thereon, that is to say:-
The said Invention relates to a peculiar construction and arrangement of
the suspending chains of suspension bridges, whereby increased rigidity and a
greater span is obtained, with considerable economy in construction.
According to this Invention, the suspending chains are rendered stiff or
rigid by the application thereto of diagonal braces. Two or more chains are
used for each side of the bridge, such chains being suspended at different
elevations, so as to form concentric curves, and the intervening spaces between
these curves are occupied by the diagonal braces above referred to, which are
connected at each end by pins or bolts to the upper and lower chain, and are
so arranged as to subdivide the space between the chains into a succession
of triangles, having their apices alternately above and below, whilst the
hypothenuse of each angle is formed by the corresponding link of the upper
or lower chain, as the case may be. The links of the lower chain should be,
of course, of a greater length than those of the upper chain, to allow for the
greater radius of the curve of that chain over that of the upper one.
And in order that the said Invention may be fully understood, I shall now
proceed more particularly to describe the same, and for that purpose I shall
refer to the several Figures in the Sheet of Drawings hereunto annexed, the
same letters of reference indicating corresponding parts throughout all the
Figures.
Figure 1 of the annexed Sheet of Drawings represents a longitudinal section
of a portion of a suspension bridge, constructed according to this Invention,
and Figure 2 is a Diagram shewing the arrangement of the suspending chains
and their diagonal braces. A, represents one of the suspending towers or piers
of the bridge, and B, is the foundation for retaining the ends of the two series
of suspending chains C and D. Any number of these chains may be employed
side by side in each set, according to the required strength of the bridge. The
second set of chains D are suspended some distance below the first set, the
radius of the curve of the lower set of chains being larger than that of the
upper set, and, consequently, the links which compose the lower chains should
be proportionately longer than those of the upper set. The links in the two
sets of chains are so disposed with regard to each other that the joints of one
set of links will coincide with the central portions of the other set of links.
E, E, are the diagonal braces, which are interposed between the two sets of
chains, for the purpose of imparting steadiness and rigidity thereto. These
braces consist of bars of a greater or less strength, according to the amount of

page_text: resistance to displacement which they will be required to afford. An eye is
formed at each end of the braces, and the two eyes are made to coincide with
the joints of the links in the upper and lower sets of chains respectively, as
is clearly shewn in Figure 1. By this mode of interposing brace bars between
two sets of suspending chains of different radii, the intervening space is sub-
divided into a series of triangles, as will be clearly observed on referring to
the Diagram, Figure 2, where C represents the upper chain or set of chains,
D, the lower chain or set of chains, and E the brace bars placed diagonally,
but in opposite directions between the chains, to the joints of which they are
secured by pins or bolts passing through the link eyes and through those of
the brace bars. The two sides a, b, of each triangle so formed are produced,
by the two neighbouring brace bars, and the third side or hypothenuse c, is
formed by the link of the upper or lower chain, as the case may be. The
platform or roadway F, which may be of any convenient construction, is sup-
ported in the usual manner by suspension rods or links H, attached to the
chains.
The chief advantages derivable from this peculiar construction of suspension
bridges are, that railway bridges may be constructed on this principle with
larger spans and a much less expenditure of material than hitherto; a com-
plete stiffness and immovability of the chains is obtained by reason of the
employment of the diagonal brace bars, since neither side of the triangles so
formed is stretched or bent, consequently the chains invariably maintain their
normal curve without being displaced, whether the load carried by the bridge
be distributed over the entire surface of the same, or only over a portion
thereof; the expansion and contraction of the materials by variations of
temperature is almost entirely neutralized, since the homogeneous material
is equally contracted or extended in all three directions; another important
advantage is, that the strength of each single part may be tested before being
applied; finally, all parts of the suspension chains and rods are acted upon
only with respect to their greatest absolute solidity, and no single part in the
whole structure forms a dead weight which requires to be supported, without
itself carrying a load, whilst in the ordinary iron structures of this class the
actual dead weight forms from one-third to one-half of the whole of the
material.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried
into effect, I would observe, in conclusion, that I do not confine or restrict
myself to the precise details or arrangements which I have had occasion to
describe or refer to, as variations may be made therefrom without deviating

page_text: from the principles or main features of the said Invention ; but what I consider
to be novel and original, and therefore claim as the Invention secured to
me by the herein-before in part recited Letters Patent, is,―
First, the general construction and arrangement of suspension bridges, piers,
and other similar roadways, as herein-before described.
Second, the system or mode of imparting stiffness and immovability to the
suspending chains of suspension bridges, piers, and other similar roadways by
the interposition between two sets of suspending chains of diagonal braces, so
arranged as to subdivide the intervening space between the upper and lower
chain or set of chains into a series of triangles, having their apices pointing
alternately upwards and downwards, as herein-before described and illustrated
by the Drawings annexed.
In witness whereof, I, the said John Henry Johnson, have hereunto set
my hand and seal, this Twenty-ninth day of October, One thousand
eight hundred and fifty-eight.
J. HENRY JOHNSON. (L.S.)