BRIDGING SYSTEM

Abstract

A modular bridging system comprising modules (10) which inter-link to form a deck suitable for use as a buoyant walkway or roadway; and in which the means for causing successive modules to interlink comprises pegs (61; FIG. 6A-6D) which, in use, joint the facing surfaces of adjacent modules allowing the modules a limited relative up-and-down linked movement and, which are readily detachable when the deck is to be dismantled.

Description

FIELD OF THE INVENTION

The present invention relates to modular bridge building systems and particularly to temporary modular bridge building systems.

REVIEW OF THE ART KNOWN TO THE APPLICANT

Presently if a river, body of water or other obstacle such as boggy ground is to be crossed, then a number of systems exist that allow the rapid building of a bridge to allow vehicles to cross the obstacle. One such bridging system is the pontoon bridge wherein the deck of the bridge is supported by a series of floating boats or pontoons which are either tied together, or fixed in position by attachment to the deck or to the river bottom. In recent times a number of powered floating vehicles have been used which can be connected together such that the decks of the vehicles form a bridge.

Another form of such a bridge is the bailey bridge which is composed of pre-fabricated building components typically made from steel or steel alloys. The building components are assembled together to form a bridge which spans across the obstacle.

The bridging systems described above all suffer from a common problem in that they are formed from large heavy components which are relatively difficult to transport.

A bridging system is therefore required which is lightweight to facilitate its transport and which is quick and simple to assemble. Such a bridging system is disclosed within.

SUMMARY OF THE INVENTION

In it broadest aspect, the invention provides a modular bridging system comprising modules which inter-link to form a deck suitable for use as a buoyant walkway or roadway; and in which the means for causing successive modules to interlink comprises pegs which, in use, joint the facing surfaces of adjacent modules allowing the modules a limited relative up-and-down linked movement and, which are readily detachable when the deck is to be dismantled. A system of this type may be readily made from lightweight material such as plastics material, such that the modules and pegs used to form the walkway or roadway are easily transported. Additionally, the modules and pegs may be quickly assembled or dismantled without the need to use heavy lifting equipment.

Preferably the facing surfaces of adjacent modules are in close juxtaposition. The close juxtaposition of the facing surfaces allows the walkway/roadway to be walked on without the risk of people's feet falling into the gap between adjacent modules.

Preferably the modules are shaped such that when not in use they can be stored in a nested stack. The formation of a nested stack of modules enables the modules to be stacked one inside another, the nesting of modules in this way giving rise to a stack of modules which are more stable when stood upon each other.

The formation of a nested stack reduces the space required to store the modules. A stack of nested modules also have an increased stability as compared to a series of modules which are simply stacked one on top of the other. It is also worth noting that the upper and lower faces, in use, of the modules may incorporate ridges and corresponding indentations which allow the upper and lower faces to interengage as a means of improving the stability of a stack of modules whether they are nested or not.

Preferably the modules incorporate one or more orifices to allow the insertion of one or more poles which attach to plates such that a stack of the modules can be sandwiched between two such plates to form an assembly for storage purposes. In this way a stack of modules may be held together to form a single unit which may be readily moved rather than having to move separate modules one at a time.

Preferably the pegs incorporate a locking mechanism to lock the pegs to the modules. The use of pegs which incorporate a locking mechanism ensures that the pegs are not accidentally ejected from the point where they joint adjacent modules.

Preferably the pegs utilise a releaseable locking mechanism. The use of a releasable locking mechanism enables a bridge to be built from the modular bridging system described herein to be readily dismantled for transport to other locations.

Preferably the modules have a wider cross-section at their upper face, in use, than at their lower face. In this way a deck can be formed wherein the upper facing surfaces, in use, of adjacent modules may fit closely together whilst a gap is provided between adjacent lower facing surfaces which facilitates the passage of water around the interlinked modules.

Preferably, at least some of said modules have a tapered shape (with a narrow, and preferably pointed end, and a broad end) in plan view, in use. Modules incorporating the tapered shape may be used at the outer edges of the deck, with the narrow or pointed end facing in the direction of a water flow and away from the direction of the water flow.

The provision of modules with a tapered shaped at the outer edge facing in the direction of the water flow assists (i.e. upstream) the flow of water around and through the interlinked modules. The tapered shape of modules facing away from the direction of the water flow (i.e. downstream) helps to reduce the formation of eddies around the modules, further assisting the flow of water through and around the interlinked modules.

Preferably at least the sides, in use, of the modules are produced from a flexible, and preferably an elastomeric material. The production of the sides of the modules from flexible material, combined with at least the upper surface, in use, or potentially the upper and lower surfaces, in use, being made from a rigid material, provides a module which may be inflated for use and deflated for storage purposes, thus reducing the volume occupied by the modules for storage purposes. Elastomeric materials give further resilience to the units, and increased capacity for shock absorbance.

Preferably the system includes means to allow the modules to be at least partially deflated. It may be particularly useful when using the bridging system on uneven marshy ground to provide a module that compresses when a load is applied to the module. This compression is enabled by the expulsion of air from the module (i.e. deflation) due to the applied load. The module resumes its original shape once the applied load is removed.

Preferably the pegs incorporate one or more openings to assist the flow of water through the pegs. This feature further assists the flow of water through and around the interlinked modules reducing the overall resistance of the interlinked modules to the flow of water.

Preferably the pegs are sized such as to enable a selective increase or decrease of the distance between adjacent modules in use. The pegs may incorporate a central section, the size of said section being increased or decreased such that the spacing between adjacent modules may be increased or decreased.

Preferably panels are provided which fix to the upper surface, in use, of one or more modules and wherein successive panels interlock in a manner which provides additional rigidity to a deck formed from modules and panels. The use of interlocking panels in this way allows loads applied to an individual panel to be spread over a larger number of modules than would be the case if the load was applied directly to the modules. Thus the bridging system incorporating modules used in combination with panels provides improved buoyancy as compared to the system wherein the panels are not used.

In any aspect of the invention there is provided a module suitable for building a modular bridging system in accordance with any preceding claim and shaped such that when not in use it can interengage with one or more identical such modules to form a nested stack. The nesting of modules in this way reduces the volume of space occupied by the modules during storage.

In any aspect of the invention there is provided a peg suitable for building a modular bridging system characterised by the feature that the peg is generally I-shaped in cross-section. The I-shape of the pegs allows limited movement of adjacent modules in a vertical direction whilst preventing horizontal movement between adjacent modules.

Included within the scope of the invention is a modular bridging system as described herein with reference to and/or as illustrated by any appropriate combination of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of the upper face, in use, of a module according to the present invention.

FIG. 2 is a schematic perspective view of the lower face, in use, of a module according to the present invention

FIG. 3 is a schematic plan view of the upper face, in use, of a module according to the present invention.

FIG. 3A is a schematic plan view of the lower face, in use, of a module according to the present invention.

FIG. 4A is a schematic perspective view of two plates 4 and their associated poles used to form an assembly of stacked modules.

FIG. 4B is a schematic representation of an assembly formed from plates and associated poles and modules.

FIG. 5 is a schematic side view of a module according to the present invention.

FIG. 6A is a schematic side view of a peg according to the present invention.

FIG. 6B is a schematic front view of a peg according to the present invention.

FIG. 6C is a schematic plan view of the upper surface, in use, of a peg according to the present invention.

FIG. 6D is a schematic perspective view of a peg according to the present invention.

FIG. 7 is a schematic perspective view of a module with a section which is tapered in shape according to the present invention.

FIG. 7A is a schematic plan view of a module with a section which is tapered in shape according to the present invention.

FIG. 8 is a schematic perspective view of a reinforcing strut suitable for use with modules according to the present invention.

FIG. 9a is a schematic view of a module which can be nested and which also incorporates an elastomeric diaphragm.

FIG. 9 is a schematic side view showing a stack of nested modules.

FIG. 10 is a schematic perspective view of an alternative embodiment of a module

FIG. 11 is a schematic plan view of a deck assembled using modules according to the present invention.

FIG. 12 is a schematic perspective view of a panel suitable for fixing to a deck formed according to the present invention.

FIG. 13 is a schematic plan view showing part of a deck formed according to the present invention wherein panels are shown which are attached or in the process of being attached to the deck.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, there is shown module 10 suitable for the construction of a modular bridging system, the module being manufactured principally from a plastics material, such as polyethylene, by a rotational moulding operation. The walls of the module 10 are thin in relation to their overall size such that the modules are hollow and filled with air such that they are buoyant when immersed in water. The modules are also sealed to prevent the entry of water into their interior.

Referring to FIGS. 3 and 3A, it can be seen that the module further comprises four receiving portions 31 into which I-shaped shaped pegs, described later, can be inserted.

The module also incorporates four orifices (elongate circular channels) 32 which extend from the upper face 12 of the module to the lower face 15 of the module. The walls of the orifices 32A may act as stiffeners when the modules are produced solely from rigid plastic material to improve the overall strength of the modules, such that they can stand greater loads.

Referring to FIG. 4B, poles may be inserted through the orifices 32 of a stack of inter-engaged modules 43 and two plates 41 attached to the ends of the poles, by known means, to maintain the inter-engagement of the modules by formation of an assembly of modules, thus facilitating the storage and transport of the modules. The plates 41 and associated poles 42 may be more clearly seen on FIG. 4A.

The orifices 32 may also be used as attachment points for the attachment of posts for signs, railings and the like.

The module has a pattern on its upper face 12, see FIG. 1, and a corresponding pattern 14 on the lower surface 15 which can be seen more clearly in FIG. 2.

Referring to FIG. 5, it can be seen that the patterns on the upper face 12, in use, comprise raised portions 51 and lowered portions 52. Similarly, the patterns on the lower face 15, in use, comprise raised portions 54 and lowered portions 53. The raised portions 51, 54 and lowered portions 52, 54 being generally elongate ridges as can be seen clearly on FIGS. 1 and 2. The upper face 12 and lower face are patterned such that the upper face of a first module will interengage with the lower face of a second module when placed in appropriate alignment atop the first module.

Referring to FIG. 1 and FIG. 3, secondary raised portions 56 are provided on the upper face, in use, of the modules 10 which interengage with secondary recessed portions 57 on the lower faces of adjacent modules. The lower face 15, in use, of the module includes secondary raised portions 56A which interengage with secondary recessed portions 57A on the upper face of adjacent modules when the modules are stacked. This interengagement of the secondary raised portions 56, 56A and secondary recessed portions 57, 57A prevents lateral movement of the stacked modules along the length of the ridges.

Referring to FIG. 3A it can be seen that the lower face 15 of the module is narrower than the top face 12 of the module. The side walls 33 of the module are generally curved in cross-section as can be seen more clearly on FIGS. 1, 2 and 5.

Referring now to FIG. 6A there is shown a peg suitable for linking adjacent modules to each other. The peg 61 is generally I-shaped in cross-section as can be seen by reference to FIG. 6C. The peg 61 is tapered along its length, as can be seen in FIG. 6A. The peg 61 is sized such that it fits into the receiving portions 31 of adjacent modules.

The peg 61 further comprises a releasable locking mechanism in the form of two resiliently deformable pins 62. The pins may be integrally formed with the peg 61 which is produced from plastics material or alternatively produced from material which is more readily resiliently deformable such as sprung steel which is then attached to the peg 61 by known means. The peg joins the modules together by interlocking with a receiving portion, in the form of a recess 55 as shown in FIGS. 1, 3 and 5, the recess narrows from the top face of the module, in use, towards the lower face of the module. The receiving portion 31 of the modules generally narrows from the top face 12, in use, towards the lower face 15 in order to better accommodate pegs.

The central section of the pegs as indicated by 63 on FIG. 6C may be increased in size or decreased in size to increase or decrease the size between adjacent modules as required in use.

Reference is now made to FIG. 3 wherein eight fixing points 34 in the form of threaded holes are indicated. These fixing points 34 enable the direct attachment of panels to the upper faces 12 of the modules such that the modules may be attached directly to temporary walkways and roadways, leading up to and on to the modular bridging system. The fixing points 34 also allow the direct attachment of panels to the upper face 12 of a deck formed from modular bridging system described herein.

Referring to FIGS. 7 and 7A there is shown a module 71 which incorporates a portion 72 which is generally tapered in shape. The module is attachable on three sides to other modules by the use of pegs which insert into the receiving portions 31. For the sake of clarity, the pattern on the upper face of the module is not shown on FIG. 7.

FIG. 8 shows a reinforcing strut, generally indicated by 81, suitable for use with modules according to the present invention. The strut 81 is made from rigid light weight material such as aluminium or rigid plastics material such as glass reinforced polyethylene. The strut 81 is elongate and has a rectangular cross-section, and further incorporates engagement means 82 which are shaped to engage with the receiving portions 31 of the modules. The strut 81 also incorporates a rigid attachment means 83A and 83B to connect a first strut to a second strut, such that the two struts are rigidly attached to each other and do not allow the deflection of struts relative to each other.

If the modules are being used to cross a waterway a first module may be attached to a bank 121 as shown in FIG. 11 of the waterway using known means not shown or by the use of a trackway used to form a roadway which approaches the bank 121 of the waterway; this may be done using the fixing points 34. Additional modules 10 are then interlinked to the first module by the use of pegs 61.

Subsequently further modules are interlinked using pegs 61 to provide a deck across the waterway to the opposite bank 122. The modules adjacent the second bank 122 of the waterway may also be attached to the bank by the use of known means or by the use of trackway used to create a roadway approaching the second bank of the waterway. Additionally modules 71 incorporating tapered portions may be used on the outer edges of the deck facing towards and away from the direction of the waterflow, as shown in FIG. 11.

The use of modules 71A with a tapered section facing towards the direction of water flow (i.e. upstream) assists the flow of water around and through the interlinked modules.

The tapered shape of the modules facing away from the direction of water flow (i.e. downstream) reduces the formation of eddies around the modules 71B thus further assisting the flow of water through and around the interlinked modules.

The flow of water through the assembly is further facilitated by the lower faces of the 15 being narrower than the upper faces 12 of the modules, such that when the modules are interlinked by the use of pegs 61 the upper faces 12 of the modules can be juxtaposed to each other whilst a gap exists between the lower faces 15 of the modules. The gap between the lower faces of the modules facilitates the flow of water through the interlinked modules.

The I-shape of the pegs 61, as previously described, allows limited vertical movement of adjacent modules relative to one another whilst preventing horizontal movement between adjacent modules. Thus the modules forming the deck have a limited capability to tilt as loads are applied to one side of the module thus reducing the strain exerted on the pegs holding the relevant adjacent modules together.

A deck formed from the interlinking of the modules, as described, may be disassembled by disengaging the locking mechanisms 62 and then withdrawing the pegs from the receiving portions of adjacent modules.

In fast-flowing water, as the modules are inter-linked they may have a tendency to become deflected by the flow of water in the direction of the water flow, such deflection resulting in the pegs linking the modules together coming under excessive strain that may in exceptional circumstances result in the pegs snapping. A strut 81 of the type previously described may be attached to appropriate rigid support means on the bank of the waterway, by known means, and the modules then attached to the rigid support strut 81 and to then each other by the use of pegs. The means used to attach the strut to the bank may provide for vertical movement of the struts to accommodate rising and falling water levels. Similarly, if the modules are attached to the tracking or walkway used to approach the bridging system, then mechanisms may be incorporated to accommodate rise and fall in water level. The deck formed from the inter-linked modules being used to then allow the attachment of a second strut to the first by the use of rigid attachment means 83A and 83B. Further modules can then be attached to the second strut and to the deck formed of interlinked modules. This process being repeated until a deck is produced across the waterway, the strut being ultimately connected to a second rigid support on the second bank of the waterway. The modules may also be attached to the banks of the waterway or to the walkway/roadway used to approach the waterway. The use of a series of struts in this way forms a reinforcing means which prevents the deflection of the inter-connected modules by a flow of water. Further struts may be used in the same way at other points in a deck formed from inter-linked modules to further reinforce the rigidity of the deck formed. It may be that the reinforcing struts 81 are only required during the initial assembly of the deck formed from inter-linked modules and once the modules are linked and anchored to the two opposing banks the reinforcing struts 81 may be removed. Additionally in fast flowing water the central sections of the pegs 63 may be increased in size to space the modules 10 further apart such that the water can more easily flow around the modules. It may then be necessary to utilise a plate-like material to cover the top of the deck formed to prevent objects and the feet of people using the bridge from entering the space between adjacent modules.

In a particularly preferred embodiment the modular bridge building system as described herein is used in combination with the ‘Constructional Panels’ described in earlier PCT patent application PCT/GB2004/004200 (WO2005035874). The panels 131 disclosed therein, see FIG. 12, are provided with holes 132 to enable the panels to be connected to the modules 10 via the fixing points 34 in the modules 10 by the use of bolts. The bolts are sized to fit through holes 132 in the panel and engage with the threaded holes/fixing points 34 in the modules 10. The holes 132 may be countersunk (not shown) in the upper face (in use) of the panel such that the head of the fixing bolt used does not protrude above the surface of the panel 132. The panel also incorporates bores 133 for the receipt of lock members as described in earlier PCT application WO2005035874.

In use, once two modules 10 have been interlinked to each other by use of a peg 61 a panel 131 can then be used to more rigidly connect the modules to each other by the use of 4 bolts which fit through the holes in the panel 131 and then screw into the fixing points 34 in the modules. Further modules are then connected to the first two modules and subsequently further panels 131 are attached to the first panel according to the methods disclosed in PCT/GB2004/004200, the panels being connected to the modules on which they are situated rest by the use of bolts. In this way the upper face of the modules 10 can be covered by the use of such panels so that no gaps exist between adjacent panels to provide a deck which can readily be used as a walkway or driveway, without the problem of feet or other objects becoming inserted between adjacent modules.

Referring now to FIG. 13, there is shown part of a deck formed of modules 10 and modules incorporating tapered portions 71 the modules being held together by the use of pegs 61. A panel 131A has been fixed to modules 10A and 10B by the use of bolts inserted through the holes 132 in the panel and which then screw into the threaded holes/fixing points 34 in the modules 10A and 10B. Subsequently panel 131B has been interengaged with panel 131A, as shown, by the engagement of the relevant tongue and groove portions and is then locked to panel 131A by the use of the lock members 134A and 134B. The panel 131B is then attached to modules 10A and 10C by the use of bolts fitted through the holes 132 in the panel 131B and fixed the modules below by the use of the threaded holes 34. Panels may be interlocked by the inter-engagement of tongue and grooved portions of adjacent panels and so the lock members are not an essential component of this particular embodiment.

Panel 131C has its right hand edge engaged with the left hand edge of panel 131A, with respective tongues and grooves fitted together. As such panel 131C is slidable with respect to panel 131A in the direction of panel 131B such that it engages with panel 131B. Panel 131B is then locked to panel 131C by the use of locking members 134C and 134D. Panel 131C once locked to panel 131B is then fixed to module 10D by the use of bolts inserted through the holes 132 in the panel the bolts are then screwed to the fixing points 34 in modules 10C and 10D. In this way a deck, formed by the upper surface of the panels is built up, the panels making up the deck being attached to each other as well being fixed to the modules on which they are situated. Each of the modules 10 in turn is attached to adjacent modules by the use of pegs 61. In this way a particularly rigid modular bridging system is provided wherein when load is applied to the upper surfaces of the panels 131 (in use), the load is distributed by the panels to a plurality of modules 10 such that the buoyancy to support the load is distributed to a plurality of modules 10 enabling larger loads to be supported than could be supported by a single module 10, or by a module connected to adjacent modules by the use of pegs 61 alone.

The use of panels in this way may negate the need to use the struts 82, as previously described, in fast flowing water.

In an alternative embodiment the modules as generally indicated by 90, on FIG. 9 are shaped to allow them to form a nested stack for storage purposes. The upper face 9, in use, of the modules being sized to fit (nest) within the opening 92 provided in the lower side, in use, of the module, to produce a nested stack of modules. The nested stack may then be held together by the use of poles in conjunction with plates as previously described with respect to FIGS. 4A and 4B. Alternatively the modules may include a diaphragm, indicated by the dotted line 93 as shown on FIG. 9a, which allows the modules when appropriately shaped, to insert further into the body of the module into which it is inserted. The diaphragm allowing air to be entered into or withdrawn from an interior of the module through a valve.

In another preferred embodiment as shown in FIG. 10 the side walls 33A of the modules as generally indicated by 100, are produced from an elastomeric plastic material and a valve 95 is incorporated into the upper face of the module. The upper section 112 of the module, which incorporates the upper face 12A and the lower section 115 which incorporates the lower face, as generally indicated by 15A are made from rigid plastics material to which the elastomeric plastic is attached. Clearly the receiving portions 31A, where the pegs fit, must be made of rigid plastics material to ensure the relative position of adjacent modules is maintained. In this particular embodiment the orifices 32 may be omitted or alternatively the sides of the orifices may be produced from a elastomeric polymer. A module is therefore provided which may be inflated and deflated by the use of the valve 95, such that the volume of the module may be minimised for storage and transport purposes. Additionally the provision of such valves allow the modules to be inflated to varying levels such that when a deck is assembled on boggy/uneven ground the deck formed by the modules has a level upper surface. The valve 95 may alternatively be incorporated into the side of upper section 112 and for multiple valves 95A may be provided.

A valve or multiple valves may be provided which allow a steady stream of air to escape from the interior of the module when a load is applied to the upper face 12A of the module such that a cushioning effect is provided by the compression of the module when used on marshy or boggy ground. Additionally this type of system may also assist in providing what is perceived to be a more level walkway/trackway over terrain which is in parts submerged and in other parts not submerged as air will be ejected more quickly from modules which are resting on solid ground. The interior of the module may comprise a first chamber and second chamber wherein the release of air only occurs from one of the chambers the other chamber remaining filled with air and thus buoyant during normal use of the module. The first chamber 101 being incorporated above the dashed line A-A and the second chamber 102 being below the dashed line A-A. Once the load is removed from the module 100 the module returns to its original decompressed position and in so doing filling with air. The return to the original decompressed position may be achieved by providing some form of spring within the first chamber 101, which compresses under the application of a load to the upper face 12A of the module and then expands once the load is removed. Alternatively the side wall 33A may be made of an elastromeric polymer which returns to its uncompressed state following the removal of the load, wherein air re-enters the first chamber 101 through the valve 95 and/or valves 95A. In a further embodiment the modules may be filled with expanded plastics foam, such as polyurethane, foam to improve the strength of the modules whilst maintaining their buoyancy. This type of foam filled module may be particularly useful on boggy ground where some of the modules may be on solid ground and hence come under greater loads than those modules which are immersed in water.

Claims

1. A modular bridging system comprising modules which inter-link to form a deck suitable for use as a buoyant walkway or roadway; and with means for causing successive modules to interlink, said means comprising pegs which, in use, joint the facing surfaces of adjacent modules allowing the modules a limited relative up-and-down linked movement, said modules being readily detachable when the deck is to be dismantled.

2. A modular bridging system as claimed in claim 1 wherein the facing surfaces of adjacent modules are in close juxtaposition.

3. A modular bridging system according to claim 1 wherein the modules are shaped such that when not in use they can be stored in a nested stack.

4. A modular bridging system according to claim 1 wherein the modules incorporate one or more orifices to allow the insertion of one or more poles which attach to plates such that a stack of the modules can be sandwiched between two such plates to form an assembly for storage purposes.

5. A modular bridging system according to claim 1 wherein the pegs incorporate a locking mechanism to lock the pegs to the modules.

6. A modular bridging system according to claim 1 wherein the use pegs utilise a releaseable locking mechanism.

7. A modular bridging system according to claim 1 wherein the modules have a wider cross-section at their upper face, in use, than at their lower face.

8. A modular bridging system according to claim 1 wherein modules incorporating a tapered shape are used at the outer edges of the deck facing in the direction of a water flow and away from the direction of the water flow.

9. A modular bridging system according to claim 1 wherein at least the sides, in use, of at least one module are produced from a flexible, and preferably elastomeric material.

10. A modular bridging system according to claim 1 including means to allow the modules to be at least partially deflated.

11. A modular bridging system according to claim 1 wherein the pegs incorporate one or more openings to assist the flow of water through the pegs.

12. A modular bridging system according to any claim 1 wherein the pegs are sized such as to enable a selective increase or decrease of the distance between adjacent modules in use.

13. A modular bridging system according to claim 1 wherein panels are provided which fix to the upper surface, in use, of one or more modules and wherein successive panels interlock in a manner which provides additional rigidity to a deck formed from modules and panels.

14. A module suitable for building a modular bridging system in accordance with claim 1 and shaped such that when not in use it can interengage with one or more identical such modules to form a nested stack.

15. A peg suitable for building a modular bridging system in accordance with claim 1 and characterised by the feature that the peg is generally I-shaped in cross-section.

16. (canceled)