GB1594610A

GB1594610A - Prefabricated bridges

Info

Publication number: GB1594610A
Application number: GB773377A
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: 1981-08-05
Also published as: DE2807789A1

Description

(54) IMPROVEMENTS IN OR RELATING TO PREFABRICATED BRIDGES (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 prefabricated bridges of modular construction, and more particularly to sloped end units for prefabricated girder bridges. The span of a prefabricated girder bridge is largely made up of a plurality of intermediate units joined in end to end relationship, each unit including a girder at each side thereof for supporting a roadway decking. For short spans and for light loads the girders may be arranged to form in the assembled span, a single longitudinally extending beam and such bridges are known in the art as "single storey bridges".Longer spans and heavier loads require what is known as a "double storey bridge" that is a bridge in which each unit includes a second girder arranged above the other such-that they are arranged to form, in the assembled span, a first longitudinally extending beam and a second longitudinally extending beam arranged one above the other and rigidly interconnected by braces.

In the double storey bridge the roadway decking is supported at the top of the upper beam and this may be an appreciable distance from the bottom of the lower beam which is approximately at the ground level at the end of the span. Each span of the double storey bridge is connected at both of its ends to an end unit which is laid directly upon the ground.

To provide access to the roadway, these end units are usually sloped. It has been a problem with bridges of this type that the changes of gradient at both ends of the steeply sloped end unit form obstructions to certain types of vehicle.

Double storey bridges are conventionally assembled in sections on one bank (the home bank) and, as more sections are added to the bridge, are passed progressively across the gap to be bridged on a roller situate on the home bank. In this mode of erection it is important that the bottom surface of the lower beam and that of the end units should be alinged and continuous to expedite the passage of the bridge over the roller. It is also useful, for speed of erection, if the bridge can be laid directly upon the ground at each bank without digging in. This is also assisted by having horizontally bottomed end units.

One way of overcoming the discontinuity between the slope of the end unit and the roadway of the bridge has been to connect the standard end units to the span at a reduced gradient. This lessens the obstruction to vehicles but introduces a slope to the underside of the end unit which creates difficulties for the roller and neccessitates some digging in which is time consuming in rock terrain.

Accordingly the invention provides bridge apparatus for a prefabricated girder bridge span comprising a sloped end unit and at least one hinged unit for connecting the end unit to an intermediate unit of the bridge span, which end unit is tapered having an upper surface and a lower surface inclined one to the other, wherein said hinged unit provides articulation between the end unit and the intermediate unit from a first position in which the lower surface of the end unit is substantially coplanar with the underside of the intermediate unit to a second position in which the upper surface is substantially coplanar with the upperside of the intermediate unit.

Preferably the hinged unit comprises a first member for rigid connection to the intermediate unit, a second member pivotally connected to the first member and for rigid connection to the end unit; and jacking means for urging the first and second members to pivot whereby, in use, the gradient of the end unit can be varied.

Preferably locking means is provided for locking the first and second members in two or more relative positions. The locking means may include a pin, and portions of the first and second members adapted to receive the pin.

The jacking means may include a jack mounted below the pivot.

Advantageously the hinged unit is provided with bracking means for locking the first and second members together for storage or trans portation, said bracing means comprising a pin and two projecting lugs, one provided on each member, for receiving said pin.

This invention extends to a prefabricated girder bridge incorporating bridge apparatus according to the foregoing.

This invention also extends to a method of erecting a prefabricated girder bridge across a gap from a home bank to the opposite bank including the steps of: a) connecting a hinged unit between the end intermediate unit of an assembly of intermediate units and an end unit, b) setting, by means of the hinged unit, the end unit in the first position so that the undersides of the end unit and intermediate units are substantially coplanar and continuous and may be passed, in rolling contact, over a roller situate on the home bank, c) passing said end unit, hinged unit and intermediate units over said roller and across the gap until the end unit is in contact with the opposite bank and d) resetting, by means of the hinged unit, the gradient of the end unit to suit the intended usage of the bridge.

The invention will now be described, by way of example only, with reference to the drawings accompanying the Provisional Specification, of which: Figure 1 is a side view of a part of an end portion of a prefabricated girder bridge incorporating bridge apparatus in accordance with the invention, and Figure 2 shows three operational configurations of the end portion of a prefabricated girder bridge embodying bridge apparatus in accordance with the invention.

Referring firstly to Figure 1 there is shown an end portion of a prefabricated girder bridge 1 of the double storey type which comprises intermediate units 2 and end units 3. As previously mentioned, the girder bridge 1 has a girder for each side of the bridge supporting roadway decking (not shown), but the structure of one side only of the bridge has been shown for clarity. Similarly the structure of each end of the bridge is identical and only a portion of one end is shown. The bridge 1 therefore should be understood to comprise four of the structures shown, one to each side of each end of the span. The intermediate units 2 comprise upper beam sections 4, and lower beam sections 5, the latter sections being integral with struts 6 which are joined to the upper beam sections 4 at pinned joints 7. The end units 3 comprise upper beam sections 8 and lower beam sections 9.

Between the intermediate unit 2 and the end unit 3 is connected a hinged unit 10, comprising upper beam sections 11, hinge 12, and struts 13. The hinge is situate between the two short upper beam sections 11 by which the hinged unit 10 is connected to the upper beam structures of the bridge. The lower ends of the struts 13 are connected to the lower beam structure at pinned joints 14. A hydraulic jack 15 is mounted between the lower ends of the struts 13 at pivoted joints 16 and 17. The jack 15, when operated, acts to thrust the joints 16 and 17 further apart thereby causing the end unit 3 to rotate about the hinge 12 with respect to the intermediate unti 2. Thus the gradient of the upper beam sections 8 of the end unit 3 can be varied from the comparatively steep gradient shown through any number of intermediate stages to the horizontal.At the lower ends of the struts 13, are overlapping flanges 18 provided with pin receiving apertures 19 to provide three preset configurations of the hinged unit 10 at which the flanges may be pinned together to lock the hinge 12 and enable the jack 15 to be relaxed. These preset configurations correspond to the configurations shown in Figure 2.

In the first of these configurations, the end unit 3 in the first position and the lower beam sections 9 of the end unit 3 are horizontal and aligned with the lower beam sections 5 of the intermediate units 2, whilst the upper beam sections 8 of the end unit provide a ramp of gradient 1 in 5 to provide access to the upper beam sections 4 of the intermediate units 2.

This configuration is most useful for rapid erection of the bridge span 1 as the bridge can be laid directly on unprepared ground.

In the second configuration, the end unit 3 is intermediate the first and second positions and the upper beam section 8 of the end unit 3 adopts a lesser gradient of 1 in 10 and the lower beam section 9 is sloping also. It is no longer possible to erect this bridge on uprepared ground as the ground must be sloped to match the underside of end unit 3. However this configuration reduces the hump effect at the hinged unit 10 for a minimum of ground preparation.

In the third configuration, the end unit 3 is in the second position and the upper beam section 8 of the end unit 13 is horizontal and is aligned with the upper beam sections 4 of the intermediate units 2 so that the hump at the hinged unit is completely eliminated. The lower beam section 9 of the end unit 3 adopts a more substantial slope so that a greater amount of ground preparation is required before the bridge can be erected. This configuration is most useful for bridges erected with a longer use in view.

Any of the three configurations described can be selected when the bridge is erected, and subsequent change in configuration may be achieved by raising the bridge span upon supporting jacks (not shown) preparing the ground, jacking the hinged units 10 to the new position desired, and lowering the bridge. It is preferred that the jacks 15 for the hinged units 10 at each side of one end of the bridge span are operated in unison so as not to subject the end units 3 to torsional forces.

The hinged units 10 are transported as a separate unit, one for each side of each end of the bridge span. The units can be supported during stowage by a brace pin 20 inserted into pin receiving apertures provided in projecting lugs 21.

Claims

WHAT I CLAIM IS:

1. Bridge apparatus for a prefabricated girder bridge span comprising a sloped end unit and at least one hinged unit for connecting the end unit to an intermediate unit of the bridge span, which end unit is tapered having an upper surface and a lower surface inclined one to the other, wherein said hinged unit provides articulation between the end unit and the intermediate unit from a first position in which the lower surface of the end unit is substantially coplanar with the underside of the intermediate unit to a second position in which the upper surface is substantially coplanar with the upperside of the intermediate unit.

2. Bridge apparatus according to Claim 1 wherein the hinged unit comprises a first member for rigid connection to the intermediate unit, a second member pivotally connected to the first member and for rigid connection to the end unit and jacking means for urging the first and second members to pivot whereby, in use, the gradient of the end unit can be varied.

3. Bridge apparatus according to Claim 2 in which there is provided locking means for locking the first and second members together in at least the two relative positions corresponding to the first and second positions of the end unit.

4. Bridge apparatus according to Claim 3 in which the locking means includes a pin and portions of the first and second members adapted to receive the pin.

5. Bridge apparatus according to any one of Claims 2 to 4 in which the jacking means includes a jack mounted below the pivot.

6. Bridge apparatus according to any one of Claims 2 to 5 in which there is provided bracing means for locking the first and second members together for storage or transportation said bracing means including a pin and two projecting lugs, one provided on each member, for receiving said pin.

7. A prefabricated girder bridge incorporating bridge apparatus according to any one of the preceding claims.

8. A method of erecting a prefabricated girder bridge across a gap from a home bank to the opposite bank, employing bridge apparatus in accordance with any one of the preceding claims, including the steps of: a.) connecting the hinged unit between the - end intermediate unit of an assembly of inter mediate units and an end unit, b) setting, by means of the hinged unit, the end unit in the first position so that the under side of the end unit and intermediate units are substantially coplanar and continuous and may be passed, in rolling contact, over a roller situate on the home bank, c) passing said end, hinged and intermediate units oversaid roller and across the gap until the end unit is in contact with the opposite bank and d) setting, by means of the hinged unit, the gradient of the end unit to suit the intended usage of the bridge.

9. A bridge incorporating bridge apparatus substantially as hereinbefore described with reference to Figure 1 of the drawings accom panying the Provisional Specification.