Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to bridge reinforcements.
Bridge reinforcements in accordance with this invention are particu-
larly suitable for use with the bridge spans of temporary bridges. It is
particularly advantageous to provide reinforcement for such bridge spans
since then the temporary bridge can support greater loads and consequently
a stock of a single design of bridge span may be able to cope with most con-
tingencies.
It has been proposed to reinforce a rectilineal bridge span of a
temporary bridge by providing the span with an underslung reinforcing member
and to tension the member by means of two similar reinforcing struts project-
ing normally from the span and connected to points on the member inter-
mediate its two ends. However such a proposal suffers from the disadvantage
that forces exerted on the points of the span where the member is attached
are high and consequently the extent to which the span can be reinforced is
limited. With such reinforcement it has been proposed to provide the rein-
forcing struts with jacking means for extending the length of the strut to
tension the reinforcing member. Such a proposal suffers from the disadvan-
tage that, since the member and strut are beneath the span, the jacking means
is not readily accessible and is, when the bridge is to be laid across a
river, liable to be submerged.
The present invention seeks to overcome the disadvantages of the
aforesaid proposals by firstly, in such proposed bridge reinforcements,
inclining the reinforcing struts such that when the member is under tension
each strut is, at its point of connection to the member, inclined at acute
angles to the member (thereby reducing the forces on the points of the span
where the member is attached) and secondly, by providing jacking
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means, for urging the reinforcing strut into its working position, which
exerts a force transverse to the longitudinal axi~ of the strut (and may there-
by be mounted in a more accessible position than hitherto).
According to the present invention there is provided a bridge rein-
forcement for a bridge span, said reinforcement comprising:
a) a reinforcement member attachable to said bridge span at two
longitudinally spaced locations,
b) at least one slideway attachable to said bridge span at a loca-
tion intermediate said spaced locations and disposable in a direction parallel
with the longitudinal axis of said bridge span~ and in respect of each slide-
way,
c) a slider block slidable upon said slideway,
d) a reinforcing strut having a first end adapted for pivotal
connection to said slider block and a second end adapted for pivoted connec-
tion to said reinforcing member, and
e) jacking means arranged to vary the position of said slider
block with respect to said slideway, whereby in use, tension is adjustable
in said reinforcing member via said reinforcing strut.
Advantageously the jacking means has locking means for retaining
the strut in its working position. The jacking means may further include
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a cable for attachment to said slider block and a jack for hauling in the
cable to thereby, in use, slideably move said second end of the strut.
The reinforcing member may comprise a chain o~ rigid elongate
members and advantageously may be provided with bifurcated ends.
This invention extends to a bridge including a bridge span rein-
forced with a bridge reinforcement in accordance with this invention. The
bridge span may include a plurality of intermedia~e units joined in end to
end relationship by unions. With such a bridge span and where the reinforc-
ing member has bifurcated ends advantageously the member may be attached to
the bridge span by each branch of the bifurcated end of the member being
attachad to a union. Conveniently the branches are attached to adjacent
unions. Where the jacking means includes a slideway, the slideway may be
mounted upon the bridge span by attachments to two adjacent unions.
The invention will now be described by way of example only with
reference to the accompanying drawings of which:
Figure 1 shows, very diagrammatically, a bridge incorporating a
bridge reinforcement in accordance with this invention, and
Figure 2 shows an embodiment of the jacking means.
Referring to Figure 1 there is shown a reinforoed bridge. The
bridge includes a bridge span 2 composed of a plurality of intermediate
units 3 and two end units 4. The end units 4 are supported by earthworks 5.
The bridge span is reinforced by a bridge reinforcement which includes a
reinforcing member 6 and two reinforcing struts 7. The member 6 comprises
a chain of rigid elongate members 8. The members 8 are pivotally connected
by links 9. The lower ends of the struts 7 are pivotally connected to the
member 6 by means of links 9. The member 6 is provided with bifurcated ends
~ and the branches of these ends
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are attached to the unions between the intermediate units 3 of the span 2.
The bridge reinforcement further comprises jacking means for urging the
strut 7 into its working position. In use the jacking means exerts a force
transverse to the longitudinal axis of the strut 7. The jacking means
includes a slideway 10 which is shown in Figure l. The slideway is attached
to two adjacent unions. The jacking means is shown in greater detail in
Figure 2 and will now be described.
The jacking means comprises the slideway 10, a cable 11 and a jack
12 for hauling in the cable 11. The upper end of the strut 7 is provided
with a slider block 13 for co-operation with the slideway lO. The jack 12
is rigidly mounted upon the slideway 10 and the cable 11 passes from the
jack around a pulley 14 to the slider block 13. The unions between the
intermediate units 3 include pins 15 which stand proud of girders 17 of the
intermediate units. The slideway 10 is attached to the pins 15 of two adja-
cent unions by means of clasps 16. Four such clasps are provided on the
slideway and enable it to be mounted astride the girders 17. The clasps 16
include a static portion 18 welded to the slideway 10 and a resiliently
biased hook 19 which is pivotally connected to the static portion 18. The
hook 19 is resiliently biased, by means not shown, towards the static portion
18 such that the pin 15 is clasped. The means for biasing the hook 19 may
be a coil spring but having regard to the environment in which bridge rein-
forcements are used it is preferable to use, instead of a coil spring, a
block of rubber like material cemented to the hook 19 in such a position that
i it bears upon the static portion 18 to bias the hook towards it as foresaid.
Preferably, to facilitate attachment of the slideway 10, the surfaces of the
clasp 16 indicated in the figure by 20 are shaped such that when the slideway
10 is offered up to the span and the pin 15 contacts said surfaces 20 the
hook 19 is initially urged, against its biasing, away from the static portion
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18 and subsequently returns with a snap action to clasp the pin 15.
In use, the bridge reinforcement is added to the bridge under erec-
tion as is convenient. The form of the member 6 facilitates the addition of
the reinforcement in that the rigid elongate members 8 and links 9 may be
added progressively as the erection of the bridge proceeds. When the bridge
is erected the member 6 may be tensioned by operating the jacks 12 to haul in
the cables ll thereby causing the slider blocks 13 to be slideably moved
along the slideways 10. The struts 7 are ~hereby moved to their working
positions.
Locking means for retaining the strut 7 in its working position is
provided. The locking means comprises a pin 21, adapted at each of its ends
to receive cotter pins 22, and pin receiving apertures 23. The strut 7 is
moved to its working position by tensioning the cable 11 thereby urging the
slider block 13 to a position to the right of the apertures 23. The slider
block may be locked in that position by inserting the pin 21 into the
apertures 23 and applying the cotter p-lns 22. When the tension in the cable
11 is released the left hand edge of the slider block 13 will abut and be
retained by the pin 21.
It will be appreciated that a satisfactory bridge reinforcement may
be provided, for one or both sides of a bridge, by employing one jacking
means preferably positioned about the middle of the span 2. In such an
embodiment the strut 7 may in its working position project normally from the
span. Alternatively the bridge may be reinforced at one or both sides with
a reinforcement as shown in Figure 1.
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