CA1100713A

CA1100713A - Unit construction steel bridges

Info

Publication number: CA1100713A
Application number: CA295,267A
Authority: CA
Inventors: Bevil G. Mabey
Original assignee: MABEY BRIDGE CO Ltd
Current assignee: MABEY BRIDGE CO Ltd
Priority date: 1977-01-19
Filing date: 1978-01-19
Publication date: 1981-05-12
Also published as: DE2801945A1; IT7819385A0; IT1092113B; FR2378133A1; NL7800592A; JPS5390626A; GB1597953A

Abstract

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.

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 .

, ~
, 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 110()713 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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11~)(~71.3 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.

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.

Claims

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 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.