GB2476843A - Bridge constructed from fibre-reinforced plastic material. - Google Patents

Abstract

The bridge 2 comprises a pair of side box modules 4, 6 which each comprise upper 10a, 10b and lower 12a, 12b longitudinally extcnding mouldings, where the upper and lowcr mouldings are joined together by joints 14a, 14b to define side cavities 18a, 18b. Between the side boxes is preferably a centre section 30 which comprises an upper deck element 32 and an underside element 34 which are preferably connected together by longitudinally extending webs 44 and so may also define at least one cavity in the centre section. The cavities are preferably large enough to allow a person to crawl through them and visually inspect the interior of the bridge. The bridge may comprise a curb drain and the cavities may house services pipes or cabling. A parapet may be joined to the side boxes. Also claimed are a kit of parts for making the bridge and a method of assembling the bridge.

Description

Modular Bridge The present invention relates to a modular bridge, in particular a modular bridge composed of fibre-reinforced plastic material.

It has been well known for many years to produce bridges from a variety of different structural materials. However, these bridges tend to suffer from a number of technical disadvantages.

For example, bridges manufactured from steel typically require re-painting every 18 years or so in order to maintain not only their visual appearance, but also their corrosion protection and thus their design life. Concrete bridges, whilst low cost, require very substantial foundations and heavy lifting equipment.

Fibre-reinforced plastic (hereinafter FRP) materials are now increasingly viewed as being more sustainable materials for the manufacture of structural bridges as compared to both steel and concrete, i.e. the higher embodied energy of reinforced concrete, especially when viewed as an installed item from cradle to grave.

Steel bridges are typically constructed from elongate spars composed of steel.

Correspondingly, it is known to produce FRP bridges which are structurally similar to steel in that the bridges are manufactured from elongate spars of pultruded FRP materials. However, such pultruded FRP materials are structurally inefficient, with a large number of joints, and moulded components tending to reduce the mechanical and structural durability of the bridge and increase its weight. Also, such FRP bridges have poor aesthetic appearance, being an assembly constructed from a combination of linearly pultruded elements, and can suffer from a poor quality of finish and weatherability.

The present invention aims to overcome these problems of such known bridges, and in particular such known FRP bridges.

Accordingly, the present invention provides modular bridge composed of a plurality of modules of fibre-reinforced plastic material, a first side box module comprising upper and lower longitudinally extending elongate first mouldings of fibre-reinforced plastic material joined along longitudinally extending joints to form therebetween a longitudinally extending hollow side cavity, the first module having longitudinally extending upper and lower first fitting surfaces; and a second side box module comprising upper and lower longitudinally extending elongate second mouldings of fibre-reinforced plastic material joined along longitudinally extending joints to form therebetween a longitudinally extending hollow side cavity, the second module having longitudinally extending upper and lower second fitting surfaces.

The present invention also provides a kit of parts for a modular bridge according to the invention, the kit comprising a pair of preassembled side modules each having longitudinally extending upper and lower fitting surfaces, and optionally further comprising a preassembled centre section module having upper and lower fitting edges for respectively fitting to the upper and lower fitting surfaces.

The present invention further provides a method of assembling a bridge, the method comprising providing a kit of parts according to the present invention, and fitting together the respective upper and lower fitting surfaces of the pair of side modules, or optionally fitting the upper and lower fitting edges on each side of the centre section to the upper and lower fitting surfaces of each of a respective one of the side modules The present invention is at least partly predicated on the technical aspect that moulded or monocoque FRP bridges are structurally more efficient than those manufactured from pultruded FRP materials. This is primarily for two reasons: there are fewer joints in a bridge composed of moulded components as compared to a bridge compose of pultruded spars; and also such moulded components have been demonstrated to be more durable than pultruded elements, The freedom of form offered by moulding, providing improved structural and aesthetic designs, is unmatched by assemblies constructed from a combination of linearly pultruded elements. The nature of the moulding process allows the incorporation of in mould finishes, such as surface films and gel coats, and these can provide an improved quality of finish and weatherability.

The modular FRP bridges used in accordance with the preferred embodiments of the present invention may be used indoors or out of doors and be of open, partly enclosed, or completely enclosed structures. Such modular FRP bridges are suitable for use over roads, railways, pedestrian and equestrian paths, rivers, waterways, dykes, canals or within shopping malls, stations, ports, sports, theme parks or other entertainment complexes.

The modular design allows for bridges of different widths and spans to be manufactured using common tooling and moulds. Thus narrow bridges for pedestrians, wider bridges for pedestrians/equestrian/cyclists and even wider for vehicles of any type can be manufactured using the same modules, which constitute building blocks for assembly together, in the factory or on-site, to form a unitary moulded bridge structure.

The moulded structural components are pre-engineered and tooling can be made that can be employed for making common components. For example, the upper moulding is common for each side box module of the bridge and correspondingly the lower moulding is common for each side box module of the bridge. In other words, in an embodiment only two moulds are required to mould the sides of the bridge, and when no centre section is required, those moulds can mould the entire bridge span structure. The designer merely needs to specify the length of the required span. For wider bridges, one or more centre sections may be required. The planar deck and planar underside may be assembled and bonded together using plural longitudinal webs therebetween, and optionally pre-made tooling may be used to mould the deck and underside if they have non-planar shape. The use of such pre-fabricated mouldings, commonly employed in plural bridge designs significantly reduces the cost and complexity of FRP bridge manufacture, and can reduce the lead time from customer order to fabrication to even below 12 weeks.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 schematically illustrates a perspective cross-sectional view of a modular bridge construction in accordance with a first embodiment of the present invention; Figure 2 schematically illustrates a transverse end view of the modular bridge construction of Figure 1; Figure 3 schematically illustrates a transverse end view of a modular bridge construction in accordance with a second embodiment of the present invention; Figure 4 schematically illustrates an exploded transverse end view of upper and lower moulding components of a first side box moulding of the modular bridge construction of Figure 1 or Figure 3; Figure 5 schematically illustrates an exploded transverse end view of upper and lower moulding components of a second side box moulding of the modular bridge construction of Figure 1 or Figure 3; Figure 6 schematically illustrates an enlarged transverse end view of a joint between the side box sections of the modular bridge construction of Figure 3; and Figure 7 schematically illustrates a parapet structure for mounting on the modular bridge construction of Figure 1 or Figure 3.

Referring to Figures 1 and 2, a modular bridge, designated generally as 2, comprises a pair of first and second side box modules 4, 6 and at least one centre section module 8 therebetween. Each module 4, 6, 8 is composed of fibre-reinforced plastic material.

Each side box module 4, 6 comprises upper and lower longitudinally extending elongate mouldings 1 Oa, lOb and 12a, 12b of fibre-reinforced plastic material. The upper and lower mouldings 1 Oa, b and 12a, b are joined along longitudinally extending outer joggle joints 14a, b and inner lap joints 1 6a, b to form therebetween a longitudinally extending hollow side cavity 18a, b. The outer joggle joint 14a, b extends longitudinally along an outer longitudinal surface 20a, b of the respective side box module 4, 6. The inner lap joint 1 6a, b extends longitudinally along a lower inner edge 22a, b of the respective side box module 4, 6. Each joggle joint 14a, b and lap joint 16a, b comprises an overlap, typically an adhesively-bonded or bolted overlap, between edge surfaces of the upper and lower mouldings lOa, b and 12a, b. The joggle joints 14a, b, and lap joints 16a, b between the upper and lower mouldings 1 Oa, b, and 1 2a, b are visually inspectable from within the side cavities 1 8a, b.

The first and second side box modules 4, 6 can have an identical or substantially identical symmetrical structure In the illustrated embodiment in which the side box modules 4, 6 are connected together via a centre section module 8 (Figures 1 and 2), the first and second side box modules 4, 6 may be identical, one being a mirror image of the other when assembled in the bridge 2. In the illustrated embodiment in which the side box modules 4, 6 are connected together directly (Figure 3), the first and second side box modules 4, 6 differ only in the moulding geometry at the interface, as shown in greater detail in Figures 4 and 5 which are in exploded form.

Figure 4 shows the structure of the upper and lower mouldings 1 Oa, 1 2a for the side box moulding 4 and when the bridge 2 has a centre section module 8 (Figures 1 and 2) the side box mouldings 4, 6 may be identical.

Figure 5 shows the structure of the upper and lower mouldings 1 Ob, 1 2b for the side box moulding 6 when the bridge 2 has no centre section module 8 and the side box modules 4, 6 are connected together directly (Figure 3).

When the moulding differ at the interface, as shown in Figures 4 and 5, the upper mouldings 1 Oa, 1 Ob of the first and second side box modules 4, 6 have a substantially identical cross-section apart from the moulding geometry at the interface.

Correspondingly, the lower mouldings 1 2a, 1 2b of the first and second side box modules 4, 6 have a substantially identical cross-section apart from the moulding geometry at the interface. In the assembled bridge 2, the assembly of upper and lower mouldings 1 Oa, 12a and the assembly of upper and lower mouldings lob, 12b have a substantially identical cross-section in a mirror image thereof The upper mouldings 1 Oa, lOb each have an integral wall construction comprising a vertical outer wall 11 Oa, 11 Ob, an upper horizontal wall 111 a, 111 b, an inwardly directed inclined wall 1 12a, 1 12b, a lower horizontal wall 1 13a, 1 13b, and a vertical inner wall 1 14a, 1 14b. For upper moulding lOb the vertical inner wall 1 14b is a shortened lap joint wall 114b for fitting to vertical inner wall 1 14a. Upper moulding lOa additionally has at the lower end of vertical inner wall 1 14a a horizontal shortened lap joint wall 11 5a for fitting to the lower moulding 12a. The lower mouldings 12a, 12b are substantially L-shaped, having vertical walls 120a, 120b and horizontal walls l2la, 121b integrally connected by an outwardly directed inclined wall 122a, 122b. The free ends 130, 132 of the horizontal walls 121a, 121b form ajoggle joint. The free ends 134a, b l36a, b of the vertical walls llOa, b, 112a, b form joggle joints.

The side box modules 4, 6 define a lower portion 90a, b which has an upper surface 92a, b which forms a deck or a deck support. The side box modules 4, 6 also each define an upper portion 94a, b which forms a respective opposed kerb 96a, b for the bridge 2. The kerbs 96a, b include the inwardly directed inclined walls 1 12a, 1 12b which are angled to deflect the wheels of a vehicle back towards the centre of the bridge in the event of an inadvertent impact therebetween. The lower portion 90a, b and upper portion 94a, b of each side box module 4, 6 is connected by a connection portion 98a, b.

The hollow side cavity 1 8a, b is shaped so that at least an internal lower surface 24a, b of the hollow side cavity 1 8a, b of the side box modules 4, 6 is continuous along the length of the side box modules 4, 6. In most preferred bridge constructions of the invention, each of the hollow side cavities 1 8a, b of the first and second side box modules 4, 6 has no transversely extending web extending across the respective cavity. Typically, each of the hollow side cavities 1 8a, b of the first and second side box modules 4, 6 has a minimum internal transverse dimension of 700 mm. This means that the internal cavity defines a volume which encloses a cylindrical space having a diameter of at least 700 mm, as indicated by circle s in Figure 2. This is sufficiently large to permit access to the cavity 1 8a, b along the entire length of the span of the bridge, either by a human or by a mechanical device which can be driven remotely along internal lower surface 24a, b.

Within each side box module 4, 6 at least one access opening 26 may be provided for the respective hollow side cavity 1 8a, b, the access opening 26 being formed in at least one of the respective upper and lower mouldings 10, 12 or an end of the respective side box module 4, 6. The access opening 26 is dimensioned to permit human access into the respective side cavity 18, and the side cavity 18 is dimensioned to permit human access therealong.

The side box module 4, 6 has longitudinally extending upper and lower first fitting surfaces 28a, b and 29a, b. As explained further below, the fitting surfaces 28, 29 are located to permit adjacent side modules 4, 6 selectively to be fitted together, by fitting together of the opposed upper fitting surfaces 28 and the opposed lower fitting surfaces 29, or to be fitted to opposed longitudinal edges of a centre part of the bridge disposed therebetween, by fitting the upper and lower fitting surfaces 28, 29 to a respective longitudinal edge of the centre part.

As shown in the illustrated embodiment of Figure 3, the modular bridge 2 may simply comprise a pair of the side modules 4, 6, each side module 4, 6 extending along the entire span of the bridge 2. However, in the illustrated embodiment of Figures 1 and 2 the modular bridge 2 further comprises at least one centre section module 30, which may also extend along the entire span of the bridge 2. The centre section module 30 is fitted between the first and second box mouldings 4, 6. The centre section module 30 comprises an upper deck element 32 and a lower underside element 34, both comprising longitudinally extending elongate mouldings of fibre-reinforced plastic material. The deck element 32 has respective opposed longitudinally extending upper fitting edges 36, 38 of the centre section module 30. The underside element 34 has respective opposed longitudinally extending lower fitting edges 40, 42 of the centre section module 30.

In either embodiment the structure of the side modules 4, 6 is the same. The side module 4 has an upper horizontal wall 62, connecting with a vertical wall 63 (both of the upper moulding 1 Oa) which in turn connects with a lower horizontal wall 64 (of the lower moulding 12a), the latter being located inwardly adjacent to the lap joint 16a between the upper and lower mouldings 1 Oa, 1 2a. The side module 6 has an upper horizontal wall 65, connecting with a vertical wall 66 (both of the upper moulding lOb) which is separated from a lower horizontal wall 67 (of the lower moulding 12b).

For the embodiment of Figure 3 and a direct connection between the side modules 4, 6, the opposed facing surfaces of vertical wall 63 and vertical wall 66 are bonded or otherwise joined together and the lower surface of lower horizontal wall 67 is joined to upper surface of the lower horizontal wall 64. This is shown enlarged in Figure 6. The lap joint between vertical wall 63 and vertical wall 66 has a length a, the lap joint at 16a between the upper and lower mouldings lOa, 12a has length b, and the joggle joint between the lower horizontal wall 67 and the lower horizontal wall 64 has length c.

These bond lengths, as for that of the remaining bonds between the structural elements, can readily be selected to provide the required structural strength to the modular structure for the bridge 2.

For the embodiment of Figures 1 and 2 and indirect connection between the side modules 4, 6 via at least one centre section module 30, the lower surface of the deck element 32 is bonded and/or bolted to the upper surface of the upper horizontal wall 62 and the upper surface of the upper horizontal wall 65 and the lower surface of the underside element 34 is bonded and/or bolted to the upper surface of the lower horizontal wall 64 and upper surface of the underside element 34 is bonded and/or bolted to the lower surface of lower horizontal wall 67.

When one centre section module 30 is fitted between the first and second box mouldings 4, 6, the opposed upper fitting edges 36, 38 of the deck element 32 are respectively joined to the first and second upper fitting surfaces 28a, b, and the opposed lower fitting edges 40, 42 of the underside element 34 are respectively joined to the first and second lower fitting surfaces 29a, b.

Alternatively, at least two parallel centre section modules 30 may be fitted together to form a composite central part of the bridge, the centre part being fitted between the first and second box mouldings 4, 6. The deck and underside elements 32, 34 are fitted together to form composite deck and underside elements. The opposed fitting edges of the composite deck element of the centre part are respectively joined to the first and second upper fitting surfaces 28a, b, and the opposed edges of the composite underside element of the centre part are respectively joined to the first and second lower fitting surfaces 29a, b.

Referring to Figures 1 and 2 again, at least one longitudinally extending web 44 of fibre-reinforced plastic material is joined to opposed inner surfaces 46, 48 of the deck and underside elements 32, 34 The deck and underside elements 32, 34 define therebetween at least one longitudinally extending hollow central cavity 50 which is continuous along the length of the deck and underside elements 32, 34. The central cavity 50 has no transversely extending web extending into the cavity 50, and typically the cavity 50 has a minimum internal transverse dimension of 800 mm. This means that the internal cavity defines a volume which encloses a cylindrical space having a diameter of at least 800 mm as indicated by circle t in Figure 2. At least one access opening 52 (shown in phantom in a typical location) is provided for the cavity 50, the access opening 52 being formed in at least one of the deck and underside elements 32, 34 or an end of the respective centre section module 30 and being dimensioned to permit human access into the cavity 50, the cavity 50 being dimensioned to permit human access therealong, or access for mechanical device which can be driven remotely.

The joints 54, 56, 58, 60 between the deck and underside elements 32, 34 and the side modules 4, 6 are visually inspectable from within the central cavity 50. The joints 68, between the deck and underside elements 32, 34 and the at least one longitudinally extending web 62 are visually inspectable from within the central cavity 50.

As shown in Figure 2 the modular bridge 2 may further comprise at least one longitudinally extending elongate kerb drain moulding 80 joined to upper moulding 1 Oa.

The kerb drain moulding 80 may be alternatively located in at least one of the deck elements 32 and a respective upper moulding 10 at a junction therebetween, A kerb drain moulding may also be provided in the bridge of Figure 3. As also shown in Figure 2, the modular bridge 2 may further comprise at least one longitudinally extending elongate service duct or cable tray 82, 84, within at least one side cavity 18 and/or within the central cavity 50. These elements are also formed from fibre-reinforced composite material bonded or moulded to internal surfaces of the structural members such as the upper or lower side mouldings, and /or the deck or underside elements, or may be manufactured from metal or other suitable materials.

Referring to Figure 7, the modular bridge 2 may further comprise a plurality of parapet stiffeners 90 joined to at least one upper moulding 10 and disposed in a mutually spaced configuration along the length thereof In combination therewith, at least one longitudinally extending elongate parapet assembly 92 may be fitted to the plurality of parapet stiffeners 90. This forms a parapet extending along the length of the bridge 2.

The parapet stiffeners 90 provided within the side box modules 4, 6 are located sequentially at appropriate intervals along the length of the bridge. These provide structural support for the attachment of a range of alternative parapet assemblies 92. The parapets may be manufactured from a variety of alternative materials such as FRP, steel, stainless steel, timber, mesh, aluminium, etc. and be of alternative designs as may be appropriate for different uses such as for pedestrian, equestrian, or vehicular application.

In place of a parapet it is also possible to provide a completely enclosed canopy, manufactured from FRP or from another material, or combination of materials with open, closed or glazed sides as required. Such canopy may be attached using the same parapet attachment point system provided along the side box modules 4, 6 or bonded continuously along its length.

The modules may be provided as a kit of parts for the modular bridge according to the various embodiments, the kit comprising a pair of preassembled side modules each having longitudinally extending upper and lower fitting surfaces, and optionally further comprising a preassembled centre section module having upper and lower fitting edges for respectively fitting to the upper and lower fitting surfaces. When the bridge is assembled, either the respective upper and lower fitting surfaces of the pair of side modules are fitted together, or the upper and lower fitting edges on each side of the centre section are fitted to the upper and lower fitting surfaces of each of a respective one of the side modules. The fitting may include bonding and/or bolting.

Accordingly, each side box module 4, 6 is typically manufactured from only two components, the upper and lower modules 10, 12, these being used on both sides of the bridge as substantially mirror image and thus similar items. Apart from the interface structures, the major surfaces of the components of opposite sides of the bridge are moulded using common moulds. The centre section module 30 comprises the substantially planar, or alternatively cambered deck 32 and underside 34 mouldings, which are readily fabricated, together with optional longitudinal support/shear webs 44 joining the deck element 32 to the underside moulding 34.

As mentioned above, the primary structural components which make up the bridge, namely the side box and centre section modules, and optionally some secondary components such as the kerb drain, cable tray and duct, are manufactured from FRP materials manufactured using only very few moulds. Typically only four moulds are required: one mould each for the components comprising the two opposing upper mouldings lOa, b and the two opposing lower mouldings 12a, b. The deck and underside elements 32, 34 are components which are typically completely or nearly flat and thus do not require moulds for their manufacture unless a greatly cambered deck is required.

By adjustment of the moulds, it is possible to produce the modular bridge with a longitudinally and/or transversely cambered geometry, possibly improving drainage and/or aesthetics in some locations. Bridges may also be produced which are either straight or curved in plan view.

Optionally, kerb drainage is provided for by the addition of a further kerb drain moulding 80. Each bridge may therefore be constructed from a common series of components.

Service ducts 80 and cable trays 82, manufactured in different geometries and from a variety of alternative materials such as FRP, steel, stainless steel, aluminium, etc., may be incorporated within any of the spaces within the bridge structure, or mounted externally as appropriate.

The modular bridge according to the embodiments of the present invention may be transported to the installation location either completely assembled with all major structural parts, for example the side box modules 4, 6 and where present the centre section module 8, already joined, or may be transported as separate modules to be joined at site prior to being installed onto foundations or supports.

Each component may be manufactured using a resin selected from one or more of polyester, vinylester, epoxy or any other resin type reinforced by one or more type(s) of fibres including glass, aramid, carbon, a hybrid fibre or natural fibre such as flax. The manufacturing process for each component may be different and use any typical known FRP manufacturing process appropriate for the component and materials in question.

Typically components are either: laid up using a wet resin system combined with dry fabrics; pre-impregnated materials, RTM, RTML, infusion, U"! curing materials, or partially impregnated prepreg material, such as commercially available under the trade mark SPRINT® available in commerce from Gurit (UK) Limited.

The fibre-reinforced plastic materials of the modules comprise a monolithic laminate, or a sandwich construction either comprising a central core between outer skin layers or with skin on only one side of the core.

Depending on the particular application and bridge design, each component may comprise a monolithic FRP laminate or a sandwich comprising one or more skins bonded to a core which may be manufactured from timber, timber product, foam, honeycomb, linked skins, or other structurally appropriate material including any core composed from 3D woven fibres.

In the workshop, the upper and lower mouldings 10, 12 may be joined together using adhesive or other joining means, resulting in a complete side box module 4, 6. The parapet stiffeners, cable ducts or service trays, and kerb mouldings where present, may be similarly joined to the side box module 4, 6. Similarly the deck and underside elements 32, 34, with any intermediate support webs 44 therebetween, may be joined using adhesive or other joining means, resulting in a complete centre section module 8.

These modules 4, 6, 8 may then be pre-assembled in the factory or transported to site for final assembly there. That final assembly may also use using adhesive or other joining means.

Where the bridge 2 is too narrow to require longitudinal supports/shear webs 44, the deck 32 and underside 34 elements may be supplied as separate components for joining to the side box modules 4, 6 either in the factory or at site.

Where assembly at site is chosen, the modules may be predrilled as appropriate to allow the use of bolts or other assembly aids to assure correct alignment of the various modules in relation to each other while any adhesive used during assembly cures.

Where the length or span of a bridge exceeds the length of the moulds available for manufacture of the various components, the required length may be achieved by joining two or more sections of the bridge together.

The modular FRP bridge in accordance with preferred embodiments of the present invention would be structurally engineered and assembled so as to meet the well accepted standards for bridge construction and structural composite materials in the relevant country in which the bridge is assembled.

The modular FRP bridge in accordance with preferred embodiments of the present invention has a very low weight as compared to steel or concrete bridges, and even as compared to bridges composed of pultruded FRP spars. This means that the bridge is easier to install, requires smaller lifting and handling equipment, and requires smaller and shallower foundations, reducing the extent of subterranean excavation.

When replacing older bridges manufactured from steel or from concrete the light weight of the modular FRP bridge can mean that existing foundations and supports may be used without the need for upgrading their load carrying capacity.

The modular bridge in accordance with preferred embodiments of the present invention would be pre-engineered in a variety of widths and spans. This provides the advantage that any lead time between order of the bridge and delivery would be reduced due to decreased design and engineering time. Also, the tooling and/or moulds for moulding the moulded modules may be pre-fabricated, again further reducing any lead time to achieve delivery. Such tooling and/or moulds may be made a standard shape and dimension for all bridge widths and spans, which can reduce design and manufacturing costs.

The modular bridge in accordance with preferred embodiments of the present invention may be moulded to receive any commercially standard form of parapet arrangement, or a canopy, allowing the bridge to be of an open, partly open or fully enclosed design.

Custom parapets may also be added where a particular visual intent or aspect of performance is required by the bridge.

The structural design of the modular bridge in accordance with preferred embodiments of the present invention avoids transverse bulkheads and thus provides for easy access for internal inspection of the internal structure of the bridge, by maintenance personnel having the ability to crawl through the cavities extending the entire length of the side sections and any centre section of the bridge without the need to close the bridge to traffic. Such a structural design allows for complete inspection of each and every joint between components and thus ensures build quality, eases through life inspection, and increases user confidence in bridge condition and life. This may be compared, for example, to a known bridge design composed of pultruded FRP spars where joint inspection is virtually impossible either during construction or subsequently for periodic routine inspection and maintenance. Furthermore, when cavities extending the entire length of the side sections and any centre section of the bridge are provided as a result of the absence of transverse bulkheads, this permits access to the internal structure of the bridge by remote operated inspection devices, for example robots on carriages, should personnel access be undesirable. For example, on other known FRP bridges, transverse bulkheads are commonly essential to maintain the structural integrity of the bridge which prevents the provision of a continuous longitudinal cavity permitting uninhibited personnel or device access along the entire length of the bridge for internal maintenance and inspection.

Such a structural construction with elongate through-cavities can provide that there are no blind bonds between FRP materials, i.e. each bond can be inspected from both sides thereof. This can increase FRP joint reliability, and eases through life inspections, correspondingly resulting in higher owner confidence. If required, remotely operated mechanical equipment can be used for the inspection of the longitudinal structural joints as it is possible for such equipment to be placed into the various cavities allowing it to traverse the full length of the bridge inspecting joints on its way. Furthermore, ease of personnel access allows joint or other repair in situ with minimum difficulty should that be required.

The modular bridge in accordance with preferred embodiments of the present invention may be transported completely assembled, or alternatively in prefabricated modules, which may be assembled on site, where dimensional limitations would make transport by the selected method expensive or difficult. The modular construction and light weight allows for increased packing density of the moulded components during transportation as compared to fully assembled structures, Single modules can form the entire span of the bridge, and fewer and larger modules demand less assembly at site, reducing risk and costs, and shortening assembly time.

The modular bridge in accordance with preferred embodiments of the present invention may have a complete lack of structural bolting within the main bridge structure, which minimises maintenance throughout the lifetime of the bridge construction. However, when assembling the modular bridge in accordance with preferred embodiments of the present invention, bolts or other assembly aids may be employed to align and support the modules during assembly and joining, thereby improving assembly quality and reducing risk. Over-taping of any joint between FRP materials or the addition of localised FRP reinforcement to regions or structural elements requiring additional structural integrity or properties is easily achieved, if required, in accordance with known FRP assembly procedures.

The FRP components may be monolithic, i.e. composed of FRP material, typically a multilayer ply, or alternatively comprise a sandwich construction, with a central core, for example of foam, between opposed outer skins of FRP laminar material. Such material structures may be selectively used for the manufacture of several of the components to lower both material and manufacturing labour costs, and also bridge weight.

The moulded nature of the bridge according to the preferred embodiments of the present invention provides the ability to add surface fire retardant resin and/or fire retardant surface films to the structural components to provide additional fire resistance to the bridge structure. In contrast, bridges constructed of pultruded FRP spars would require a resin exhibiting fire, smoke and temperature (FST) resistance to be present throughout the pultruded FRP spars, which may add a significant cost penalty to the structural FRP material.