Improvements in Girder-structures for Suspension Railways.
Year: 1896

page_text: Date of Application, 16th Nov., 1896-Accepted, 16th Nov., 1897
Improvements in Girder-structures for Suspension Railways.
A communication by THE MASCHINENBAU ACTIEN GESELLSCHAFT NURNBERG, of
24, Kesslerstrasse, Nuremberg, in the Empire of Germany, Manufacturers.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester, both
in the County of Lancaster, 118 New Street, Birmingham, in the County of
Warwick and 322, High Holborn, in the County of Middlesex, Civil Engineer,
do hereby declare the nature of this invention and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement:-
This invention relates to girder structures for suspension railways and will
be described with reference to the accompanying drawings, in which:-
Figure 1 is a perspective view of the structure generally.
Figures 2 and 3 diagrammatic plans of the horizontal girders as used in curves
Figures 4 and 5 plan views of the upper and lower horizontal girders respec-
tively.
Figure 6 a side elevation of the vertical and horizontal girders with the trestle
in cross section.
Figure 7 a cross section of the whole structure.
Figure 8 a diagram illustrating the action of girders under variations of
temperature.
Figures 9, 10 and 11 are perspective and diagrammatic views of a modified
form of construction.
Figures 12 to 15 are details of said modification in which Figure 12 is a side
elevation of the vertical girder a with the lower girder c in position, but the
upper girder only indicated by a dotted line for clearness in order to show the
omission of the middle beam. Figure 13 is a plan view of the upper girder b.
Figure 14 a cross section on the line st of Figure 12 and Figure 15 a cross section
on the line q r of Figure 12.
This improved girder structure, in contradistinction to all the forms of con-
struction hitherto employed for similar purposes, consists of only one vertically
disposed truss girder which is stiffened at the top and bottom by two horizontally
disposed latticed or truss girders.
The upper horizontal girder b which as shown in Figures 2 and 4 consists
of two side beams 12 and a central beam a' all trussed together by diagonal
braces and transverse ties b, is riveted by ordinary joints to the top of the
vertically disposed girder a (Figures 4 and 6) whilst the lower horizontal girder c
which as shown in Figures 3 and 5 consists of two side beams el cand a central
beam a trussed together by diagonal braces and transverse ties is similarly

page_text: riveted by joints to the bottom of the vertical girder a (Figures 5 and 6). The
middle beams a¹ and a² of the upper and lower horizontal girders b and c serve
also as top and bottom beams for the vertical girder a so that the vertical girder
is formed by the middle beams a¹ and a2 of the horizontal girders b and c
(Figures 4 and 5) and by the diagonal braces a and vertical ties a° (Figure 6).
The vertical girder a and the horizontal girder bare together supported at
each end at the points A and B on the trestle legs or oscillatory supports S S¹ as
shown in Figure 1 in general perspective view and more in detail in Figure 6, a
little play being allowed between the ends and a* of successive spans.
All the vertical loads and reactions resulting from the weight of the carriage
and of the whole girders structure are thus received by the vertical girder a and
transmitted to the supports S S at the points A and B, which points also receive
the horizontal reactions of the horizontal girder b. The lower horizontal. girder c
which is connected as before stated to the vertical girder a is further connected
at each end C D to the supports S S¹ by a truss formed of oblique tension rods
(Figures 1 and 5) arranged to transmit to said supports the horizontal reactions
of the said girder c, the points C and D being vertically below the points A and B.
. The side beams c¹ of the girder c are formed as rail carriers as shown in
Figure 7 and are further tied to each upper joint of the vertical girder by
means of oblique tension rods f f (Figures 1, 5, 14 and 15).
"
This improved girder structure has special advantages in that ample room is
afforded for the free oscillation of the carriage (see Figure 7) and that the
structure is suitable for use in curves of any desired curvature.
As shown in Figures 2 and 3, the making of curved pieces is extremely simple.
for the reason that only the lower horizontal girder c need be curved concen-
trically to the track, whilst the vertical girder a and also the upper girder b may
remain straight. The preparation and also the fitting up of the girder structure
is not therefore complicated or rendered more difficult by the existence of curved
pieces.
This improved arrangement affords, morcover, a means of making the ordinary
superstructure more advantageous than where constructions,necessitating the
ordinary two or more vertical girders are employed.
As is well known, in view of the alterations of length produced by variations
of temperature, it is advisable to place the superstructures of lengthy street rail-
way viaducts on oscillatory supports arranged at right angles to the axis of the
track because these can be of considerably lighter construction than fixed tie
beams. In straight stretches of track any desired number of vertical girders a
alongside of one another may be connected by fixed links with the upper ends of
the oscillatory supports S S¹ without impeding the free mobility of the latter
which may thus oscillate into positions parallel to themselves. On the other hand
in the case of curves in the track, the upper ends of the oscillatory supports S S
being arranged radially to the curve of the track will have their free mobility
impeded when connected by more than one vertical girder a and will not therefore
have the desired action under variations of temperature. This will be under-
stood by referring to Figure S. In this diagram let m n and o 2 be two bars
representing in plan two vertical girders (a) and let S be a bar representing in
plan the upper end of an oscillatory support (S) arranged as shown radially to
the curve of the track. Assuming the ends m and o to be pivotally connected
to two points of a fixed abutment for example, then in the event of an alteration
in length of the bars m n and o p through variations in temperature the ends m
and o would retain their positions whilst the ends n and p would extend to n¹ p
for instance, but as n and p are kept at a given distance apart by the bar $ and
as the distance nl pl is greater than n p the points n p¹ would move to n p
taking the bar S into the position indicated in dotted lines at S" if the above
movements were possible. But as S representing the trestle or oscillatory support
can only oscillate into positions parallel to itself it is obvious that the above

page_text: movements are impossible seeing that S is not parallel to S, and the advantages
of an oscillatory support are thus not secured in curves where more than one
vertical girder are employed.
By the use of only one vertical girder a however in accordance with the present
invention, which girder is mounted or supported as hereinbefore described at the
points AC and B D, the free mobility of the oscillatory supports S S¹ even in
curves is in no way effected, if only the ends a³ a of the girders, as shown in
Figure 6, be movable within certain limits on their supports.
Seeing that in street railways constructed on the suspension rail system, the
use of oscillatory supports is from economic and also (owing to their light appear-
ance) from aesthetic reasons, particularly desirable, this improved form of girder
structure shows a very considerable technical advance.
In cases in which it is a question of diminishing, as far as possible, the weight
and obtaining a particularly light pleasing appearance, the girder structure herein-
before described may be carried out in the manner shown in the accompanying
drawings in Figures 9-15 without affecting its firmness and stability. The
middle beams aa² of the upper and under horizontal girders (b c), which in the
form of construction shown in Figures 1-8 formed the top and bottom beams
of the vertical girder a as before described, in this modified form are omitted,
and the strains which would have been absorbed by the above mentioned central
beams a¹ a are conveyed by the diagonals and 3 of the upper and under
horizontal girders b and c to the side beams b¹ b and c c of the said upper and
under girders.
RF
For this purpose, as shown in Figures 12-15, the vertical girder a consisting
of the diagonal braces a and vertical ties aº is rivetted to the joints k of the
diagonals 6 of the upper girder b and to the joints of the under girder c. A
separate plan of the girder c without the middle beam a2 is shown diagram-
matically in Fig. 10 and reference may be had to Figure 5 in other respects for
details of construction the middle beam being disregarded. The diagonals b
and therefore transfer all the strain and pressure which would have been
absorbed by the central beams al a², to the joints ii of the side beams b¹² and c¹ c²
of the respective horizontal girders b and c.
It is obvious however that only one central beam either a¹ or a² need be omitted
if desired.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is:―
1. A girder structure for double track suspension railways, characterised by
the arrangement of only a single vertical girder (a) for receiving all the vertical
loads, the upper and under beams of said girder, for the purpose of obtaining
the necessary resistance against torsional strains, being stiffened by horizontal
girders (b c), each mounted at two places (A. C and B D) substantially as described.
2. A modified form of construction of girder structure such as herein described
for use in curves characterised by only the lower horizontal girder (c) being curved
concentrically to the track, whilst the vertical girder (a) and the upper horizontal
girder (b) remain straight substantially as described.
3. A form of construction of the girder structure herein described, characterised
by the three principal members of the same, namely, the vertical girder (a) and
the upper and lower horizontal girders (b and c) being mounted at each trestle
or oscillatory support always at only one point and in such a way that the
supports (A C or B D) at one trestle always lic vertically under one another,
and admit of so much play that even in curves the oscillation can take place
unimpededly, substantially as described.
4. A modified form of construction of the girder structure herein described,
characterised by the central beam (a' or a²) of the upper and under horizontal

page_text: girders being omitted, and the vertical girder being only connected at the joints
with the diagonals of the horizontal girders (b c) substantially as described.
Dated this 14th day of November 1896
WM. P. THOMPSON & Co.,
Agents.