ELEMENTS MODULAIRES EN PONT EN ACIER

UNIT CONSTRUCTION STEEL BRIDGES

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
A prefabricated lattice bridge girder component for
a unit construction steel bridge comprises a zig-zag formation of
web members united with a single chord member to form a lattice
of two or more adjacent triangles having the chord member as a
common base. A plurality of such components may be assembled
to form for instance complete bridge girders of varying complexity.
If desired, additional or secondary members may be inserted into
the triangular frames for strengthening purposes.

Revendications

WHAT WE CLAIM IS:-
1. A prefabricated lattice bridge girder component
having a single chord-forming member and a zig-zag
shaped web formation with at least four legs and
having its ends and one or alternate apex parts
attached to the chord-forming member to form a
lattice of two or more adjacent triangles having the
chord-forming member as a common base, the ends of the
chord-forming member and the remaining apex parts
of the web formation remote from the chord-forming
member having holes to enable two or more such
components to be bolted or pinned end to end,
or in reverse facing relationship with or without
an intervening lattice frame.


2. A component in accordance with claim 1 wherein
at least some of the triangles contain a substantially
triangular or other configuration of secondary
reinforcing members.

3. A component in accordance with claim 1
wherein alternate legs of the web are
perpendicular to the chord-forming member.

4. A lattice bridge girder comprising two or more
girder components as claimed in claim 1, 2 or 3


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bolted or pinned together end to end or in reverse
facing relationship.


5. A lattice bridge girder comprising two or more
girder components as claimed in claim 1
bolted or pinned in reverse facing relationship
to an intervening lattice frame.


6. A lattice bridge girder as claimed in claim 5
in which the intervening lattice frame is of plural
diamond configuration.

A lattice bridge girder as claimed in claim 5
in which the intervening lattice frame is of plural
triangular configuration.

8. A lattice bridge girder as claimed in claim
5 in which the intervening lattice frame is of
plural parallelogram configuration.


9. A lattice bridge main girder comprising at least
a pair of parallel disposed components as claimed in
claim 1, 2 or 3 and which are connected by
roadway supporting cross-beams laid upon the
top of the chord-forming members or attached in
the vees formed between adjacent triangles.


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Description

llV(~713

~ lis invention relates to a prefabricated
lattice bridge girder component e.g. for use in unit
construction steel bridges, wherein certPin main
girder members are pre-assembled or fabricated together
in a workshop in order to minimise site connections
and site erection time. Such bridges, of which the
~ailey Bridge (British Patent 553374~ is the classic
example, comprise prefabricated latticework panels
of rectangular shape. The rectangular panel has
ho~ever the disadvantage that when numbers of panels
are assembled together to form bridge girders, some
of the panel members are non-load-bearing. They
therefore add weight to the structure without
contributing to its strength.
The present invention seeks to provide a
prefabricated lattice bridge girder component in ~-hich
the geometry of the constituent members is such that
when assembled into large structures - such as bridge
main sirders - all the members are load-carrying,
thus providing a far more efficient and economical
structure.
In accordance with the present invention a
prefabricated lattice bridge girder component has a
single chord-forming member and a ziS-zag shaped web
formation with at least four legs and having its ends
and one or alternate apex parts attached to the chord-
forming member to form a lattice of two or more

.
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, ~
,

llV07:13

adjaccnt triangles having the chord-forming member
as a common base, the ends of the chord-forming member
and the remaining apex parts of the web remote
from the chord-forming merllber having holes to enable
two or more such componentS to be bolted or pinned
end to end or in reverse facing relationship with
or without an intervening lattice frame.
The invention also consists in an assembly
of girder components as aforesaid with or without
other components fand forming for instance complete
bridge girders.
The invention further consists in a bridge
incorporating components or girders as aforesaid.
The nature of the invention will be further
explained by reference to the accompanying drawings
comprised of Figures 1~ lA, 2, 3, 3A, 4 to 10, 11A, llB
and 12 to 15 inclusive, and further Figures 16, 16A,
17, 18~ 18A, 19 to 25, 26A, 26B and 27 to 30
- inclusi~e.
Referring firstly to Figure 1, there is shown
a prefabricated lattice bridge girder component in its
simplest form comprised of a single horizontal chord
A and a zig ZaS web formation of four web mcmbers~
or legs ~, C, D and E united thereto to form a double
adjacent triangle lattice structure of which the chord

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A constitutes a common base.
The two ends F, G of the chord A and the
apices H, J of the web member formation are formed
with suitable holes for bolting or pinning the
components together to form girders of various lengths.
A longer form of component shown in Figure
2 has a web formation which together with the chord
defines a triple triangle lattice. This component
can be used in combination with the Figure 1 component
to give different length increments. The individual
members of the components can be made from standard
rolled or drawn steel sections. The shaping of the
components is such that they may readily be reversely
' nested one with another as indicated in Figure lA
thereby economising in the use of storage space and
reducing overall load width when in transit.
Figures 3 and 3A show auxiliary chord members -
of different length which are intended to be combined
respecti~ely with components having a three triangle
lattice and a four triangle lattice to provide bridge
girders.
Figure 4 shows a bridge girder comprised of a
- five triangle lattice component having an auxilairy
chord comprised of two auxiliary chord members of the
length shown in Fig. 3.




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In order to produce a deeper and stronger
girder, components may be connected together at their
apices as shown in Figure 5.
In Figure 6 there is shown an additional
component in the form of a diamond-shaped frame
which when combined with the other components provides
girders having a still greater depth and strength as
shown in Figure 7.
When used to form bridge main girders,
cross beams carrying the roadway can be attached in
the vees of the web-formation to provide a through
type bridge as shown in Figure 8 or on top
of the main chords to provide a deck type bridge
as sho~ in Figure 9, the main girders in each
instance being of substantially the same construction.
In a still further mode of application the
components can be arranged vertically ins~ead of
horizontally, for the construction of piers or towers
as shown in Figure 10.
In addition to all the foregoing, the
geometry of the basic component can be ~aried to
comprise one horizontal chord, as before, but with
half the web members arranged vertically and half
diagonally, as illustrated in Figure llA and llB,
to form an 'N' type truss.

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13


Simple chords combine with the components to
provide girders as shown in Figure 12.
Components can be connected together through
their apices, as shown in Figure 131 so as to produce
deeper and stronger girders.
Girders of double depth can be achieved by
connecting between them frames either in triansular
fashion - as in Fisure 14 - or in parallelogram
~ashion as shown in Figure 15.
Bridge cross girders may be attached as
pre~iously described to form either ~through~l type
or "deck'i type bridges and the frames may also be
erected vertically to form piers and towers.
Figures 16, 16A, 17, 18, 18A, 19 to 25,
26A, 26B and 27 to 30 inclusive some~hat resemble
dra~ring ~igùres which have already been referred to
and show, except in Figs. 18, 18A, the mode of insertion
into the triangular frames of additional or secondary
members in substantially triangular or other
configurations, or combinations thereof as may be
appropriate to particular constructions.
The purpose of these secondary members is
to reduce the lengths of the main frame members s~ as
thereby to increase considerably the compressive and/or
bendin$ loads which they are capable of carrying.