GB1587204A

GB1587204A - Bridge reinforcements

Info

Publication number: GB1587204A
Application number: GB773577A
Authority: GB
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1977-02-23
Filing date: 1977-02-23
Publication date: 1981-04-01
Also published as: DE2807859A1; CA1080412A; DE2807859C2

Description

(54) IMPROVEMENTS IN OR RELATING TO BRIDGE REINFORCEMENTS (71) I SECRETARY OF STATE FOR DEFENCE, London do hereby declare the invention for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to bridge reinforcements.

Bridge reinforcements in accordance with this invention are particularly 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 contingencies.

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 projecting normally from the span and connected to points on the member intermediate 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 reinforce.

ment it has been proposed to provide the reinforcing struts with jacking means for extending the length of the strut to tension the reinforcing member. Such a proposal suffers from the disadvantage 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 means, for urging the reinforcing strut into its working position, which exerts a force transverse to the longitudinal axis of the strut (and may thereby be mounted in a more accessible position than hitherto).

According to the present invention there is provided a bridge reinforcement for a bridge span, said reinforcement comprising: a reinforcement member attachable to the bridge span in an underslung position thereto, at two longitudinally spaced locations, at least one slideway attachable to said bridge span at a location intermediate the spaced locations and disposable in a direction parallel with the longitudinal axis of the bridge span; a slider block slidable upon the slideway, a reinforcing strut having a first end adapted for pivotal connection to the slider block and a second end adapted for pivotal connection to the reinforcing member,and jacking means arranged to vary the position of the slider block with respect to the slideway, whereby in use, tension is adjustable in the reinforcing member via the reinforcing strut.

Advantageously the slideway and the slider block are provided with coengageable locking means.

The jacking means may include a jack attached to the slideway and a cable attached between the slider block and the jack.

The reinforcing member may comprise a chain of rigid elongate members and advantageously may be provided with bifurcated ends.

This invention extends to a bridge including a bridge span reinforced with a bridge reinforcement in accordance with this invention.

The bridge span may include a plurality of intermediate units joined in end to end relationship by unions. With such a bridge span and where the reinforcing 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 attached to a union. Conveniently the branches are attached to adjacent unions. 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 in 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 reinforced 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 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 1. 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 ajack 12 for hauling in the cable. The upper end of the strut 7 is provided with a slider block 13 for co-operation with the slideway. The jack 12 is rigidly mounted upon the slideway 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 is attached to the pins 15 of two adjacent 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 and a resiliently biased hook 19 which is pivotally connected to the static portion.

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 may be a coil spring but having regard to the environment in which bridge reinforcements are used it is preferable to use, instead of a coil spring, a block of rubber like material cemented to the hook in such a position that it bears upon the static portion to bias the hook towards it as foresaid. Preferably, to facilitate attachment of the slideway, the surfaces of the clasp indicated in the figure by 20 are shaped such that when the slideway is offered up to the span and the pin 15 contacts said surfaces the hook 19 is initially urged, against its biasing, away from the static portion 18 and subsequently returns with a snap action to clasp the pin 15.

In use, the bridge reinforcement is added to the bridge under erection 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 11 thereby causing the slider blocks 13 to be slideably moved along the slideways 10. The struts 7 are thereby 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 aperture 23. The slider block may be locked in that position by inserting the pin into the apertures and applying the cotter pins. When the tension in the cable 11 is released the left hand edge of the slider block 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.

WHAT I CLAIM IS: 1. A bridge reinforcement for a bridge span, the reinforcement comprising a reinforcement member attachable to the bridge span in an inderslung position thereto, at two longitudinally spaced locations, at least one slideway attachable to said bridge span at a location intermediate the spaced locations and disposable in a direction parallel with the longitudinal axis of the bridge span; a slider block slidable upon the slideway, a reinforcing strut having a first end adapted for pivotal connection to the slider block and a second end adapted for pivotal connection to the reinforcing member, and jacking means arranged to vary the position of the slider block with respect to the slideway whereby in use, tension is adjustable in the reinforcing member via the reinforcing strut.

2. A bridge reinforcement according to Claim 1 wherein the slideway and the slider block are provided with coengageable locking means.

3. A bridge reinforcement according to either one of Claims 1 and 2 wherein the jacking means includes a jack attached to the slideway and a cable attached between the slider block and the jack.

4. A bridge reinforcement according to any one of the preceding claims in which the reinforcing member comprises a chain of rigid elongate members.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Figure 2 shows an embodiment of the jacking means. Referring to Figure 1 there is shown a reinforced 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 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 1. 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 ajack 12 for hauling in the cable. The upper end of the strut 7 is provided with a slider block 13 for co-operation with the slideway. The jack 12 is rigidly mounted upon the slideway 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 is attached to the pins 15 of two adjacent 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 and a resiliently biased hook 19 which is pivotally connected to the static portion. 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 may be a coil spring but having regard to the environment in which bridge reinforcements are used it is preferable to use, instead of a coil spring, a block of rubber like material cemented to the hook in such a position that it bears upon the static portion to bias the hook towards it as foresaid. Preferably, to facilitate attachment of the slideway, the surfaces of the clasp indicated in the figure by 20 are shaped such that when the slideway is offered up to the span and the pin 15 contacts said surfaces the hook 19 is initially urged, against its biasing, away from the static portion 18 and subsequently returns with a snap action to clasp the pin 15. In use, the bridge reinforcement is added to the bridge under erection 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 11 thereby causing the slider blocks 13 to be slideably moved along the slideways 10. The struts 7 are thereby 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 aperture 23. The slider block may be locked in that position by inserting the pin into the apertures and applying the cotter pins. When the tension in the cable 11 is released the left hand edge of the slider block 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. WHAT I CLAIM IS:

1. A bridge reinforcement for a bridge span, the reinforcement comprising a reinforcement member attachable to the bridge span in an inderslung position thereto, at two longitudinally spaced locations, at least one slideway attachable to said bridge span at a location intermediate the spaced locations and disposable in a direction parallel with the longitudinal axis of the bridge span; a slider block slidable upon the slideway, a reinforcing strut having a first end adapted for pivotal connection to the slider block and a second end adapted for pivotal connection to the reinforcing member, and jacking means arranged to vary the position of the slider block with respect to the slideway whereby in use, tension is adjustable in the reinforcing member via the reinforcing strut.

5. A bridge reinforcement according to any

one of the preceding claims in which the reinforcing member has bifurcated ends.

6. A bridge including a bridge span reinforced with a bridge reinforcement according to any one of the preceding claims.

7. A bridge according to Claim 6 in which the bridge span includes a plurality of intermediate units joined in end to end relationship by unions.

8. A bridge according to Claim 7 as dependent on Claim 5 in which each branch of the bifurcated ends of the member are attached to a union.

9. A bridge according to Claim 7 in which the slideway is mounted upon the bridge span by attachment to two adjacent unions.

10. A bridge incorporating a bridge reinforcement substantially as hereinbefore described with reference to Figure 1 or to Figures 1 and 2 of the accompanying drawings.