WO2010122311A1

WO2010122311A1 - Deployable bridge element

Info

Publication number: WO2010122311A1
Application number: PCT/GB2010/000818
Authority: WO
Inventors: Alistair Law
Original assignee: Ove Arup & Partners International Ltd
Priority date: 2009-04-22
Filing date: 2010-04-22
Publication date: 2010-10-28
Also published as: GB0906978D0; GB201006775D0; GB2469752B; GB2469752A

Abstract

A deployable bridge element comprising a plurality of interconnected deck panels (2) that are movable between an extended configuration and an unextended configuration; and an inflatable member (1) connected to the deck panels (2) wherein inflation of the inflatable member (1) deploys the bridge element and moves the deck panels (2) into the extended configuration.

Description

DEPLQYABLE BRIDGE ELEMENT

This invention relates to a deployable bridge element such as a deployable walkway for use as a gangway or passerelle for a yacht or the like, or a deployable bridge structure for passage of persons and/or vehicles.

Gangways or passerelles are used for convenient passage between waterborne vessels and land. To ensure ease of use and mobility, it is desirable for these bridge element to be compact when not in use, and to be lightweight. It is however also necessary for the bridge element to have the necessary strength and rigidity to be used safely and comfortably by passengers and to support their weight as well as the weight of any items they may be carrying. Similarly, deployable bridge structures are preferably lightweight and also compact when not in use, to facilitate deployment and mobility.

The term "bridge element" refers herein to an element capable of carrying a load whilst spanning, and which is thus capable of carrying a bending moment as well as vertical load. In the present context, structural elements that spread load but do not span are not considered bridging elements. For example, floating pontoons and the like that are incapable of spanning a gap and supporting a load over the gap are not considered to be bridge elements.

Viewed from one aspect, the present invention provides a deployable bridge element comprising a plurality of interconnected deck panels that are movable between an extended configuration and an unextended configuration, and an inflatable member connected to the deck panels, wherein inflation of the inflatable member deploys the bridge element and moves the deck panels into the extended configuration.

With the arrangement of the invention, the deck panels may provide a bridge surface for supporting a load such as a person or vehicle, and they are retained in the extended configuration by the inflatable member. Preferably, the deck panels are all aligned when in the extended configuration, to thereby form the bridge surface. The unextended configuration provides a compact arrangement when the bridge element is not in use, and may for example involve folding or overlapping of the deck panels to fit them into a smaller space.

The use of an inflatable member allows the deployable bridge element to be lightweight. In a preferred embodiment, the inflatable member provides separation between a tension member and a compression member of the bridge element when it is deployed by inflation of the inflatable member. The inflatable member is thus preferably placed on the underside of the deck panels, as the deck panels support a compressive load in the preferred embodiment. The tension member may be provided by a wall of the inflatable member and/or by tensile elements such as cables joined to or integrally formed with the inflatable member. A preferred type of inflatable member is an inflatable tube that extends along the length of the bridge element, such as a cylindrical or rectangular tube. With this arrangement, the deck panels are in compression and are thus preferably of a stiff construction, and of a material selected to carry a compression load. Bending loads arising from vertical loading on the bridge element can thus be efficiently carried by the combination of tension member and compression member. A further benefit of the use of an inflatable member is the ability for the bridge element to optionally be used as a floating pontoon, as the inflatable member can provide sufficient buoyancy for this purpose. The inflatable member preferably includes one or more extension compensators for avoiding stretching of the walls of the inflatable member when it is folded about the deck panels in their unextended configuration. When the inflatable member is on the underside of the deck panels, folding of the deck panels in the direction away from the inflatable member will tend to require the inflatable member to extend over a greater length. There may be one or more extension compensator on the upper wall and/or on the lower wall of the inflatable member.

In a preferred embodiment, the upper wall includes extension compensators adjacent to the joints between deck panels, thereby allowing for bending of the deck panels. These extension compensators may be, for example, pleats, bellows or shirring. Preferably, the extension compensators in the upper wall comprise recesses providing a gap between the wall and the deck panel at the joint.

The lower wall may incorporate extension compensators. In some embodiments where the lower wall should preferably sustain a tensile load, and so the extension compensators of the lower wall are preferably tapered or curved portions at one or both ends of the bridge element. Toward the ends there is less need to provide separation between the tension and compression elements, and so a tapered section can be used without detrimental effect. In contrast to bellows or the like, the use of tapered end sections will not significantly reduce the tensile load carrying capability of the lower wall of the inflatable member. In embodiments where the lower wall does not need to sustain a high tensile load, for example where the bridge element is for light use or where an additional tensile element joined to the inflatable member, such as a cable, is used to carry a tensile load, then the extension compensator of the lower wall can be similar to the upper wall, and hence may comprise recesses, pleats, bellows or shirring, or similar arrangements to permit changes in the length over which the lower wall extends.

There may be two or more inflatable members extending along the length of the bridge element on either side of the bridge element. Where more than one inflatable member is used, there is preferably a single valve and interconnection between the inflatable members to ensure simultaneous inflation.

Reinforcement may be provided in walls of the inflatable member(s) to increase the tensile strength and/or stiffness. This reinforcement is of particular benefit where a part of the inflatable member forms the tension member for the bridge element. For example, cables may be embedded in or bonded to walls of the inflatable member(s) or otherwise joined to the inflatable member(s).

To deploy the bridge element, the inflatable member(s) are inflated by means of an electric or foot pump.

The deck panels may comprise a surface portion and a web or flange portion extending away from the surface and extending along the length of the bridge element in order to provide structural strength. The deck panels may alternatively or in addition comprise one or more box sections extending along the length of the bridge element. This enables the deck panels to carry bending load, which improves the overall bending stiffness of the bridge element and also allows the deck panels to support the weight of the bridge element during deployment and when in the unextended configuration. Additional reinforcing strips may be provided, for example bonded to the deck panels and side walls of the inflatable member(s), in order to further increase the bending stiffness of the bridge element and avoid undesirable curvature in use.

In a particularly preferred embodiment, the bridge element includes resilient members arranged to bias the deck panels toward the unextended configuration. The resilient members may be springs or similar, and are preferably connected between adjacent deck panels. A single resilient member may be present between each pair of deck panels, although more than one resilient member may be used to increase stability. A preferred embodiment uses spring hinges to connect adjacent deck panels. For light applications, such as a bridge element forming a pedestrian walkway, the spring hinges may be spring hinges of the type used in self closing doors. Inflation of the inflatable member acts against the resilient members in order to deploy the bridge element, with the resilient members acting to promote deflation of the inflatable member and move the deck panels into the unextended configuration when the pressure in the inflatable member is released. This enables stowage of the bridge element to be automatic, without manual input required. Deflation may be accelerated by reverse operation of the pump.

The deck panels may each be interconnected by one or more hinges such that the unextended and extended configurations are obtained by folding adjacent deck panels toward and away from one another. The hinges may also be resilient members, for example the spring hinges mentioned above. In a particularly preferred embodiment, the plurality of deck panels are connected end to end by hinges such that the extended configuration is formed by a line of deck panels. With this arrangement, the abutted ends of the deck panels may be arranged to join along a line at an angle to the vertical when in use in the extended configuration. Thus, elements of the deck panels are preferably angled away from the perpendicular to the deck surface. For example, the end surfaces of the deck panels and/or end profiles of flanges or box sections of the deck panels may be at a 45° or 135° angle to the surface of the deck panel. The use of angled elements allows vertical and bending loads as well as horizontal loads to be transmitted between adjacent deck panels.

The number of deck panels is preferably selected based on the desired length of the bridge element and the required unextended dimensions. For typical applications, the plurality of deck panels may for example consist of between 7 to 15 panels joined end to end.

Preferably the panels are arranged to all fold in the same direction, such that the unextended configuration resembles a coil of panels. Thus, resilient members may bias the deck panels to fold toward each other, the biasing forces all acting in the same direction. Preferably, the deck panels are arranged to roll upwards, away from an inflation member on the underside of the panels. This arrangement makes best use of the forces imparted by inflation of the inflatable member, and avoids compression of the inflatable member between adjacent panels.

In order to provide a more compact arrangement in the coiled unextended configuration described above, the plurality of deck panels are preferably arranged in a sequence with decreasing size to enable deck panels further from the start point of inflation to curl up and nest within deck panels closer to the start point of inflation as the unextended coil of panels is formed. The sequence of decreasing size may consist of a simple reduction in size of each panel compared to the preceding panel, but a preferred arrangement results in a rectangular coil of panels in the unextended configuration, with altemating long and short panels arranged to form long and short sides of the rectangle, and the long and short panels decreasing in size compared to the preceding long and short panel respectively.

The bridge element may be for use as a vehicle bridge or the like, such as a temporary bridge for military use. In this case, the construction of the deck panels and inflatable member and the maximum span of the bridge element is designed based on the required load carrying ability, such as a maximum vehicle weight. Alternatively, the deployable bridge element may be intended for use for passage of persons and goods between two points, and thus is arranged to support a lesser load, such as the weight of a typical person or persons. A preferred application of this type is for use as a yacht gangway or passerelle, i.e. a bridge element for passage from a floating vessel to land such as a dock or pier. A bridge element of this type is typically secured to the vessel and deployed outward onto the dock or pier. The coiled arrangement of the preferred embodiment is of particular benefit in this instance. The bridge element can be used to form any traditional 'bridge', and so other uses are envisaged, such as a lightweight folding bridge for small spans.

Further diverse uses for the bridge element are also possible. Solid or louvred deck panels can be used to form a foldable/extendable cover, such as an awning, roof canopy or brise soleil, to provide shade and protection from the weather. The lightweight and self supporting nature of the bridge element enables it to be used with other forms of solid panels. The dimensions of the panels can be varied to suit the desired application and to provide further uses, such as shorter and wider panels used to form a foldable bed or sofa bed, which folds out upon inflation. In this latter use, the inflatable elements may be utilised to provide a cushion or mattress as well as being the actuating mechanism for deploying the bridge element. In its broadest sense, the invention can be advantageously used in any circumstance where a light, self supporting, deployable bridging element is required.

Materials for the deck panels and inflatable member, and other components of the bridge element should be selected based on the required load carrying ability, and are preferably also constrained based on the weight of the deployable structure, to ensure ease of deployment and transport. For the deck panels, composite materials such as glass reinforced plastic (GRP) are preferred, for their light weight, high stiffness and high strength. For the inflatable member(s) PVC fabrics or chlorosulfonated polyethylene (CSPE) synthetic rubber (CSM) fabrics (such as Hypalon^R™ made by DuPont Performance Elastomers) may be used. With these preferred materials, the inflatable member can readily be bonded to the deck panels using an appropriate adhesive, although alternative connection means may also be used, such as a mechanical coupling. The bridge element may include a mounting device for securing one end of the walkway to a fixed mounting location, such as the deck or hull of a vessel. The mounting device may include a one or two way pivot, for vertical and/or horizontal pivoting of the bridge element relative to the mounting point. The mounting device may also incorporates an actuator or actuators for adjusting the horizontal and or vertical angle of the bridge element relative to the mounting point. In a preferred embodiment a hydraulic arm is provided as part of the mounting device, which can adjust the bridge element to a desired vertical angle in the unextended or extended configuration, and provides cantilever support for the bridge element. A ratchet fixing between the bridge element and a vertical adjustment device such as the hydraulic arm may also be used. This enables the bridge element to be easily deployed toward a landing point that is above or below the mounting point, or supported at an angle in a cantilevered fashion. Preferably, the hydraulic arm is arranged to be disconnected once the bridge element is fully deployed. This leaves the bridge element free to rotate to accommodate movement of the mounting location relative to the landing point, such as the movement of a floating vessel relative to a dock.

The distal end of the bridge element may be arranged to sit directly on the landing point. Preferably, the bridge element is supported at the landing point by the inflatable member(s). The lower surface of the inflatable member(s) at the distal end may be provided with a wear resistant surface or coating and/or reinforcement. This allows for movement of the mounting location to be accommodated, for example movement between a floating vessel and a pier, or movement due to flexure of the bridge element under load.

For additional stiffness and safety the bridge element may comprise connectors for joining a rope or cable between the ends of the bridge element when it is deployed. This allows a rope to be tied across the length of the bridge element to maintain it in the deployed state by preventing movement of the deck panels away from the extended configuration. The bridge element may include cleats for attachments of springers and/or mounting points for a handrail, especially when it takes the form of a yacht passerelle or foot .bridge. Certain preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 shows a first deployable bridge element in the form of a yacht passerelle in its stowed (unextended) configuration; Figure 2 shows the fully extended configuration of the deployable bridge element of Figure 1 ;

Figure 3 is a sequence of drawings showing the deck panels of a second deployable bridge element moving from the unextended to the extended configuration as the bridge element is deployed, with the inflatable tubes not shown; Figure 4 is a side view of the bridge element of Figure 3 in the extended configuration;

Figure 5 is a plan view of the deck panels of Figure 3 in the extended configuration, with the inflatable members not shown;

Figures 6A to 6C show details of the side view of Figure 4; Figure 7 is a side elevation of the bridge element of Figure 3 in its stowed

(unextended) configuration; and

Figure 8 is a cross-section through the bridge element of Figure 3 at a mid-point of a deck panel with the inflatable member inflated.

Figure 9 shows, in schematic form, an embodiment where cables are added to take tensile forces.

The preferred embodiments of the deployable bridge element take the form of a yacht passerelle, and a first deployable bridge element is shown in Figures 1 and 2 in the stowed and deployed configurations. The bridge element includes two inflatable tubes 1 and eleven deck panels 2. In Figure 1 the deck panels 2 are in their unextended configuration, with the inflatable tubes 1 deflated, and hence they take the form of a rectangular coil. The deck panels 2 are sized to form long and short sides of the rectangle, with decreasing size toward the distal end of the bridge element.

Figure 3 shows a sequential positions of the deck panels 2 of a second deployable bridge element as they move from the unextended to the extended configuration. This movement is driven by inflation of the inflatable tubes 1 , which deploys the bridge element. The inflatable tubes 1 take the form of air beams 1 consisting of a single inflatable pocket bonded to each side of the bottom of the deck panels 2, and as they are inflated the deck panels 2 unfold and are aligned. The final image in the sequence of Figure 3 shows the deck panels 2 in the extended configuration, with all the panels 2 aligned to form a continuous bridge deck. Figure 3 also illustrates the sequence of sizes of the deck panels 2.

The deployable bridge element of Figures 1 and 2 differs from that of Figure 3 mainly in the construction of the deck panels 2. In Figures 1 and 2 the deck panels 2 have a solid side flange portion 8 for stiffness and the inflatable air beams 1 are bonded to these flange portions 8. In the second example of a deployable bridge element shown in Figure 3 and the Figures discussed below the side flange 8 is a thin web, and the deck panels include additional stiffening elements not present in the first deployable bridge element of Figures 1 and 2. This difference in the side flange portions 8 leads to differences in the design of the inflatable tubes 1 , although the inflatable tubes 1 and deck panels 2 interact in a similar fashion in both the first and the second deployable bridge elements, and in other respects, the two deployable bridge elements are similar. Hence, spring hinges 4 are provided in a similar manner and the deck panels 2 have a similar sequence of decreasing size. It will be appreciated that the features discussed below could be utilised with the deployable bridge element of Figure 1 and 2 for the same beneficial effects.

More detail of the arrangement of the deck panels 2 of the second deployable bridge element can be seen in Figures 4 and 5. The profile of the inflated tubes 1 is shown in dashed outline in Figure 4, and runs along the base of the eleven deck panels 2. Adjacent deck panels 2 are connected together by spring hinges 4, which join to the underside of the deck surface. A pair of spring hinges 4 are used in each case. At the yacht end of the bridge element mounting points 5 are provided on each side of the proximal deck panel 2' for a mounting device (not shown). The mounting device includes pivots for joining to the mounting points 5 to thereby allow vertical rotation of the passerelle relative to the yacht (or other mounting location). The mounting device also includes a further pivot for horizontal rotation. A support arm 6 is provided to secure the bridge element at the desired vertical angle, and connects to the proximal deck panel 2' via a ratchet 7 on the underside of the panel. Detail of the ratchet 7 and support arm 6 can be seen in the enlarged view of Figure 6A. After deployment, a hand rail 3 can be affixed to the passerelle, as shown in

Figure 4.

Each deck panel 2 includes side flanges 8 for additional stiffness, and side reinforcing strips 9 are provided for further increasing the stiffness of the longer deck panels. These features can be seen in more detail in Figures 6B and 6C, which also more effectively shows the arrangement of the spring hinges 4 and their attachment to the underside of the surface of the deck panels 2. The inflatable tubes 1 are not shown in full in Figures 6B and 6C, but the upper wall of the inflatable tubes 1 appears as a dashed line 14. The side flanges 8 extend downward away from the surface area of the deck panels 2, and at the join of adjacent panels 2 the flanges 8 have end edges at a 45° or 135° angle to the surface of the deck panel 2. The orientation of the end edges switches for odd and even panels 2, such that in this embodiment the proximal panel 2' joins to the second panel with edges at a 135° angle clockwise from the bridge deck surface, the second and third panel joint with edges at a 45° angle clockwise from the bridge deck surface, and so on in alternating sequence, such that the flanges 8 are generally trapezoidal in shape. This arrangement allows for transfer of bending loads between adjacent deck panels 2 when the deck panels 2 are in deployment. To accommodate the spring hinges 4 and allow them to fit flush with the deck surface when the bridge element is deployed every second deck panel 2 includes recesses in the end profile.

Figures 6B and 6C also illustrate the profile of the inflatable tubes 1 around the hinges 4. A recess 13 is formed in the upper walls of the inflatable tubes 1 around each hinge 4. The recesses 13 act in a similar manner to pleats or shirring in clothing, compensating for changes in length of the underlying structure to be accommodated. The upper walls of the inflatable tubes 1 have to extend along a greater length when the deck panels 2 are folded, and these recesses 13 allow for this change in length by fitting closer about the hinges 4 when the panels 2 are folded together. Recesses 13 can also be included in lower walls of inflatable tubes 1 similar to recesses 13 in upper walls compensating for changes in length between the folded and extended positions. An example of an embodiment having recesses in both the upper and lower walls is shown in Figure 9, which is discussed below.

The lower walls of the inflatable tubes 1 have tapered sections 15 at either end of the bridge element. These sections ensure effective coupling of the tensile member formed by the lower wall of the inflatable tubes 1 and the compression member formed by the aligned deck panels 2. The tapered sections 15 also have a similar function to the recesses 13 in the upper wall, as they act like a fold of a bellows and allow the lower walls to extend over a greater length when the deck panels 2 are folded into the unextended configuration. The trapezoidal shape of each deck panel 2 including the flanges 8 and recesses in the end profiles can be seen in Figure 7, which shows a side view of the unextended configuration. In this configuration the inflatable tubes 1 are deflated and the deck panels 2 form a rectangular coil, with each spring hinge 4 forming a right angle. The dashed line 14 shows the position of the upper wall of the inflatable tube when it is folded, with the recesses 13 fitting more closely about the hinges 4 to compensate for need to extend the inflatable tubes 1 over a greater length. The spring hinges 4 are biased toward this folded configuration, and thus they will be applying a rotational force to the deck panels 2 when they are extended. This force will tend to fold the deck panels 2 upward, and is counteracted by inflation of the inflatable tubes 1 when the bridge element is deployed.

The side reinforcing strips 9 are bonded to the sides of the flanges 8 and the sides of the inflatable tubes 1 , as can be seen in the cross-section view of Figure 8. This cross-section is taken through a typical deck panel 2, which includes side reinforcing strips 9, at a point midway between the ends of the panel 2. Figure 8 also shows other elements of the construction of the deck panels 2, including box sections 10, and internal reinforcing strips 11. The box sections 10 are used to provide additional stiffness for the deck panels 2 and have a cap plate at either end to provide compression load transfer between the deck panels 2. They extend along the length of each panel 2, with an end profile corresponding to the end profile of the side flanges 8. The internal reinforcing strips 11 have a similar function to the side reinforcing strips 9, and thus prevent curvature of the upper portions of the inflatable tubes 1.

Figure 8 also shows the cross-section of the inflatable tubes 1 , which is constant along the main portion of the length of the bridge element, and tapers at the two ends of the bridge element as illustrated in Figure 4.

The deck panels 2 include eyes 12 for running a locking rope along the underside. The locking rope can be tied between the ends of the bridge element when it is deployed in order to secure the deck panels 2 in the extended configuration.

As noted above, Figure 9 shows, schematically, an embodiment with recesses 13 in both the upper and lower walls of the inflatable tubes 1. Cables 16 are used to provide tensile strength. The recesses 13 give greater freedom for both the upper and lower walls to fit about the outer portion of the deck panels 2 when they are folded up into the unextended configuration. The cables 16 compensate for the reduction in tensile stiffness of the lower wall that arises from the recesses 13 in the lower wall. In the embodiment of Figure 9, which includes two parallel inflatable tubes as for the embodiment of Figures 1-8, there are a total of four cables 16. The cables 16 comprise cables that cross over and wrap around the inflatable tubes 1. The side elevation of Figure 9 shows only a single inflatable tube 1 and parts of two cables 16. The two cables 16 cross over from one side of the inflatable tube 1 to another and hence what is visible in Figure 9 is the left hand portion of a first cable 16¹ and the right hand portion of a second cable 16². The cables cross over one another at the centre point of the bridge element 17, and so the left hand portion of the second cable 16² and the right hand portion of the first cable 16¹ are hidden behind the inflatable tube 1 as viewed in Figure 9. The cables 16¹ and 16² would appear as an elongated X-shape in plan view. The other inflatable tube 1 , not visible in Figure 9, has a similar arrangement of crossed cables 16. It will be appreciated that similar cables 16 could advantageously be used to increase stiffness in the embodiment of Figures 1 to 8, whether or not lower wall recesses are also used. As the cables 16 wrap around the inflatable tube 1 and cross over at the lower wall of the inflatable tube 1, the air pressure in the tube 1 serves to maintain separation of the cables 16 from the deck panels 2, and hence maintains separation of the tensile elements of the bridge from the compression elements

In the above embodiments, the deck panels 2 are 5 mm thick GRP, and the inflatable tubes 1 are Hypalon^R™. The inflatable tubes 1 are bonded to the underside of the deck panels 2 along each side between the box sections 10 and flanges 8. At the distal end of the bridge element, furthest from the mounting points 5, reinforcement is provided to increase the wear resistance of the outer surface of the inflatable tubes 1 , which forms the support surface for the distal end of the bridge element.

When in use, inflation of the tubes 1 acts against the spring hinges 4 to pull the deck panels 2 into alignment, and transform the bridge element from the unextended configuration to the extended configuration as shown in Figures 1 to 3. The deck panels 2 carry a compressive load, and the lower portions of the walls of the inflatable tubes 1 carry a tensile load. Optionally, the inflatable tubes 1 can be reinforced by cables or the like to increase their tensile strength and stiffness. Bending loads resulting from vertical loads on the bridge deck are hence carried by the compressive and tensile strength of the deck panels 2 and tube 1 respectively. The angled end profiles of the deck panels 2 allow loads to be spread between adjacent panels 2 to some extent.

Whilst use as a yacht passerelle is the subject of the embodiment described above, the bridge element is not limited to this use and may, for example, be scaled up and/or increased in strength to produce other deployable structures, such as pedestrian or vehicular bridges. Longer or wider bridge elements may be produced by changing the size and/or number of deck panels. Further possible uses are discussed above, including awnings, roof canopies, brise soleil, foldable beds, and the bridge element can be adapted for these uses and other uses by selection of appropriate dimensions and materials.

Claims

CLAIMS:

1. A deployable bridge element comprising: a plurality of interconnected deck panels that are movable between an extended configuration and an unextended configuration; and an inflatable member connected to the deck panels; wherein inflation of the inflatable member deploys the bridge element and moves the deck panels into the extended configuration.

2. A deployable bridge element as claimed in claim 1 , wherein in the extended configuration the deck panels are all aligned and form a bridge surface.

3. A deployable bridge element as claimed in claim 1 or 2, wherein the inflatable member provides separation between a tension member and a compression member of the bridge element when the inflatable member is inflated.

4. A deployable bridge element as claimed in claim 3, wherein the inflatable member is arranged to be on the underside of the deck panels when the bridge element is deployed and in use.

5. A deployable bridge element as claimed in claim 3 or 4, wherein the tension member is provided by a wall of the inflatable member and/or by tensile elements joined to or integrally formed with the inflatable member.

6. A deployable bridge element as claimed in any preceding claim, wherein the inflatable member is an inflatable tube that extends along the length of the bridge element.

7. A deployable bridge element as claimed in any preceding claim, wherein the inflatable member includes an extension compensator for accommodating movement of the deck panels between the extended and unextended configurations.

8. A deployable bridge element as claimed in any preceding claim, comprising two or more inflatable members extending along the length of the bridge element, wherein the inflatable members are interconnected to ensure simultaneous inflation.

9. A deployable bridge element as claimed in any preceding claim, wherein the deck panels comprise a surface portion and a web or flange portion extending away from the surface portion and extending along the length of the bridge element.

10. A deployable bridge element as claimed in any preceding claim, wherein the deck panels comprise one or more box sections extending along the length of the bridge element.

11. A deployable bridge element as claimed in any preceding claim, comprising reinforcing strips bonded to the deck panels and to side walls of the inflatable member(s).

12. A deployable bridge element as claimed in any preceding claim, comprising resilient members arranged to bias the deck panels toward the unextended configuration.

13. A deployable bridge element as claimed in claim 12, comprising at least one resilient member between each adjacent pair of deck panels.

14. A deployable bridge element as claimed in any preceding claim, wherein the deck panels are interconnected by hinges such that the unextended and extended configurations are obtained by folding adjacent deck panels toward and away from one another.

15. A deployable bridge element as claimed in claim 14 wherein some or all of the hinges comprise resilient members arranged to bias the deck panels toward the unextended configuration.

16. A deployable bridge element as claimed in claims 14 or 15, wherein the plurality of deck panels are connected end to end by hinges such that the extended configuration is formed by a line of deck panels.

17. A deployable bridge element as claimed in claim 16, wherein the abutted ends of the deck panels are arranged to join along a line that is at an angle to the vertical when the bridge element is deployed and the deck panels are in the extended configuration.

18. A deployable bridge element as claimed in any preceding claim, wherein the deck panels are arranged to all fold in the same direction, such that the unextended configuration resembles a coil of panels.

19. A deployable bridge element as claimed in claim 18, wherein the plurality of deck panels are arranged in a sequence with decreasing size.

20. A deployable bridge element as claimed in claim 19, wherein the sequence of decreasing size comprises alternating long and short panels, the long and short panels decreasing in size compared to the preceding long and short panel respectively and being thereby arranged to form long and short sides of a rectangular coil of panels in the unextended configuration.

21. A deployable bridge element as claimed in any preceding claim, wherein the deck panels, comprise a composite material and/or the inflatable member(s) comprise a PVC fabric or chlorosulfonated polyethylene (CSPE) synthetic rubber (CSM) fabric

22. A deployable bridge element as claimed in any preceding claim, comprising a mounting device for securing one end of the bridge element to a fixed mounting location

23. A deployable bridge element as claimed in claim 22, wherein the mounting device includes a one or two way pivot, for vertical and/or horizontal pivoting of the bridge element relative to the mounting point.

24. A deployable bridge element as claimed in any preceding claim, comprising connectors for joining a rope or cable between the ends of the bridge element when it is deployed.

25. A deployable bridge element substantially as hereinbefore described with reference to the accompanying drawings.