ZA200600955B - Modular metal bridge and method for production thereof - Google Patents

Description

C 1 ® - 2006700958

MODULAR METAL BRIDGE AND MANUFACTURING METHOD

The invention relates to a modular metal bridge and its manufacturing method.

The invention enables to build provisional ridges, but may also apply to quick and economic realisation of average range bridges.

During military operations, it is often necessary to realise works for spanning rivers or valleys or to rebuild destroyed bridges rapidly.

To this end, the armies may have foldable bridges as described, for instance, in the document US-A-4,825,492 but « BAILEY »-type modular bridges have been known, consisting of a number of beams and metal profiles enabling to provide with little means and reduced staff, two longitudinal carrier elements forming trellised beams and connected, at their base, with transversal elements carrying a matting.

The BAILEY bridge has been subjected, since its creation, to numerous improvements, but while keeping the same general arrangement.

For example, the document US-A-4,965,903 describes a bridge of this type also comprising two trellised side beams connected at their bases by spacers whereon rests a matting. In this technique, the lower section of each side beam consists of butt-jointed tubular profiles with a rectangular section, the adjoining ends of two consecutive profiles being connected by several fish plates interconnected with the end of each beam by metal shells running between the fish plates. Consequently, the link between two consecutive profiles is hardly visible since the fish plates and the shells are placed inside the profiles but the assembly remains little aesthetic since, as in BAILEY bridge, the bridge is supported by two trellised side beams also forming the guard rail.

Besides, even in this recent technique, a very large number of elements are used whereof the assembly remains rather long and compiex.

To solve these shortcomings, the applicant company proposed, in the French patent n°2 801 328, a new manufacturing method of a modular bridge comprising, for each trestle between two resting points, two longitudinal beams consisting of butt-jointed elements and connected by transversal spacers, the assembly supporting a platform.

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Such a realisation exhibits the advantage of requiring only a small number of building elements, respectively longitudinal beam elements, transversal spacers and upper junction elements which, in the embodiments of the French patent 2 801 328 may be simple metal corner pieces used for laying wooden sleepers or casing panels for casting a slab, or prefabricated slabs fitted with sealing means with the upper soles of both beams.

Moreover, the beam elements consist of caissons with trapezoidal or rectangular section, which facilitates the laying process and, at equal weight, confers the beams excellent stiffness. On the other hand, the number of building elements is particularly reduced since it is possible to realise beforehand beam elements of great length, for instance approx. ten metres. Indeed, the specialised military units are now fitted with lifting means enabling to place and assemble elements of several tons.

But another advantage of this arrangement lies in its external aspect, far more aesthetic that the usual military bridges carried by two longitudinal trellised beams. A modular bridge of the type described in the French patent 2 801 328 exhibits, conversely, an external aspect very similar to that of the conventional bridges and, consequently, such a technique may be used not only for provisional bridges, for instance for military usage, but also for the rapid and economic construction of metal bridges of average range which blend in particularly well with the environment.

The applicant company has, however, extended its researches with a view to improving still further the technique described in its previous patent and has succeeded in simplifying further the realisation of such a metal bridge. On the other hand, it has been possible to develop different techniques for realising and placing the bridge, in particular in the case when the platform is made of concrete.

The invention concerns therefore, generally speaking, a modular metal bridge comprising a substantially horizontal platform resting on two longitudinal beams and consisting of at least three series of elements prepared beforehand, respectively a series of longitudinal elements each comprising two substantially horizontal spaced apart soles, respectively lower and upper soles, connected by at least one substantially vertical web, said beam elements being butt-jointed to form at least two parallel longitudinal beams spaced apart from one another, a series of transversal o 3 spacers spaced apart longitudinally, each having two ends fitted with removable attachment means on matching parts of the beam elements and a series of junction elements between the upper soles of the beam elements.

According to the invention, the upper junction elements rest on the transversal linking spacers between the elements of both beams by dint of wedging members whose height is adjusted so as to provide a continuous floor at the upper faces of the upper soles of the longitudinal beams.

In a first preferred embodiment, the upper junction elements are formed by a series of rectangular plates resting on the transversal spacers by dint of longitudinal profiles whereof the height is adjusted so that the upper faces of said plates extend at the upper faces of the upper soles of both longitudinal beams to form a continuous platform.

In such a case, the upper soles of the beam elements form two lanes for vehicles running on the bridge, said upper soles being treated to promote the adhesion. The junction plates between the upper soles of the beams may then consist of simple light grates.

But the platform consisting of the upper soles of the beams and junction plates therebetween may also serve as a permanent formwork for casting a concrete slab.

In another embodiment, the junction elements between both longitudinal beams consist of concrete slabs resting, on the one hand on the upper soles of the longitudinal beams and, on the other hand, on the transversal spacers by dint of wedging means of determined height, to define a continuous platform.

Preferably, according to the arrangement described in the previous patent 2 823 128, each longitudinal beam element forms a hollow caisson with a quadrangular cross-section with two substantially horizontal faces forming the soles, respectively upper and lower soles of the beam and two side faces fitted with means for fastening the spacers or, possibly, guard rail supports.

In a particularly advantageous embodiment, the consecutive elements forming a longitudinal beam are connected two by two, by their adjoining ends, at their lower soles by a linking means hinged around a transversal axis and bear upon one another, at their upper soles, by a

® 4 ® transversal wedging means whereof the width is adjusted to confer the longitudinal beam, between two spaced apart resting points, an upwardly convex elongated profile and having a jib sufficient to compensate for the downward deflection of each beam under the effect of the own weight of the bridge and of the loads applied.

Preferably, the hinged linking means between two consecutive beam elements comprises, at the end of each element, at least one longitudinal part for connection with a corresponding part of the element adjacent, each linking part being attached to the lower sole of the element and having at least one portion protruding past the end thereof and wherein is provided an orifice with a transversal axis and that, when assembling two consecutive beam elements, the protruding parts of the linking pieces overlap so that the orifices are aligned and centred on the same transversal axis for threading an interconnection rod.

Besides, the wedging means between the upper soles of two consecutive beam elements comprises, at the end of each element, a wedge consisting of a flat metal bar having two parallel transversal edges, respectively an internal edge welded along one end of the upper sole and an external edge bearing, when assembling two consecutive beam elements, against an external edge of the corresponding wedge of the element adjacent, each wedge having a width adjusted so that, after mounting two consecutive beam elements, their upper soles are placed in planes forming to one another a preset angle | so that the whole longitudinal beam follows the lengthwise profile requested.

Advantageously, after mounting consecutive beam elements and placing the wedging means, the adjoining ends of said beam elements are connected, at least provisionally, at their upper sections, by a locking means of the joint, so that all the elements behave like a continuous beam for the transport and the placement thereof.

Particularly advantageously, the whole platform of the bridge is covered with a concrete slab interconnected at least with the upper soles of both beams and those exhibit an upwardly convex elongated profile having a jib adjusted for compressing the concrete by downward deflection of said beams under the effect of the own weight of the bridge and of the loads applied.

® 5 ®

Preferably, each longitudinal beam consists of at least two consecutive elements connected, on the one hand at their lower sections, by a joint around a transversal axis and on the other hand, at their upper sections, by at least one linking member of variable length for maintaining the elongated convex profile of the beam between two spaced apart resting points, at least during the realisation of the concrete slab, the length of said upper linking members being diminished, after realisation of the slab to enable downward deflection of the beam with compression of the slab up to a resting position over one another of the upper sections of the adjoining ends of both consecutive elements.

Each upper linking member between two consecutive beam elements may consist of at least one hydraulic cylinder having a body and a piston rod hinged respectively on each of the consecutive elements, or of a sand measure box delineating a chamber filled with sand with a drain port enabling partial discharge of the sand for compressing the slab by reducing the jib of the longitudinal beam.

In case when the superstructure of the bridge lies on at least three spaced apart resting points, respectively two end abutments and at least one central pier, each longitudinal beam includes, at each central pier, a central element resting on the pier and having two ends connected to the opposite ends of adjoining beam elements, by means of joints with a transversal axis placed substantially at the level of upper soles, the other elements of the beam being connected to one another with joints placed substantially at the level of their lower soles.

The invention also covers a manufacturing method of a metal bridge wherein at least two longitudinal beams are built each composed of at least two butt-jointed beam elements, on two spaced apart resting points is laid a bridge trestle consisting of two beams connected together by spacers, at least two longitudinal profiles are laid on said spacers and on said profiles are laid a series of junction plates extending between the upper faces of the longitudinal beams and forming therewith the platform of the bridge.

The longitudinal beams prepared beforehand by butt-joining consecutive elements may be launched by longitudinal thrust from one of the resting points or may be prepared on the bank and lifted to be laid on the resting points.

® 6 ®

It is also possible to prepare trestles comprising two beams connected by spacers and to place them on the resting points, either by launching or by lifting.

Each longitudinal beam consisting of at least two consecutive elements whereof the adjoining ends are connected at their bases by a transversal joint, in case when the beam is launched by longitudinal thrust from one of the resting points, the first beam element placed foremost is lowered, when launched, while rotating round its joint and may be laid on a floating support associated with the front end of said first element up to the second resting point, the latter being equipped with a lifting means which raises the first element for bringing it in alignment with the following element and laying it on the second resting point.

Other advantageous characteristics, within the protection framework of the invention, will appear in the following description of certain particular embodiments, described by way of non-limiting examples and represented on the appended drawings.

Figure 1 is a cross-sectional view of a trestle element according to the invention.

Figure 2 is a partial perspective view of the end of a trestle element.

Figure 3 shows, at enlarged scale, the assembly of the ends of two longitudinal beam elements.

Figure 4 is a top view of the end of a beam, the upper sole being removed.

Figure 5 shows another hinged linking means between two consecutive beam elements.

Figure 6 is a schematic elevation view, of a beam consisting of three consecutive elements.

Figure 7 shows schematically, as a longitudinal sectional view, a bridge trestle curved upward and covered with a slab.

Figure 8 shows a link by a sand measure box between two consecutive elements.

Figure 9 shows, as a top view, the realisation of a slantwise bridge.

Figure 10 shows schematically, a bridge with a hinged superstructure resting on a central pier.

C 7

Figure 1 represents a cross-sectional trestle element, the semi-left view being a running sectional view and the semi-right view of the end of the trestle, according to line |, | of Figure 3.

As in the embodiment of the previous patent FR 2 801 328, each trestle element 1 comprises, generally speaking, two longitudinal beam elements 1, 1’ spaced apart symmetrically of both sides of a longitudinal middle plane P of the trestle and connected to one another rigidly by transversal spacers 2. They may consist of tubes, as in the case of the previous patent, which enables to obtain excellent rigidity for a reduced weight. However, one may also use more simply I-section profiles whereof the dimensions and the number are determined for ensuring the necessary rigidity. These profiles 2 are simply bolted, at their ends 21, on fastening plates 14 distributed along the side faces of both beams 1, 1" and forming gussets drilled beforehand with holes for attaching the end 21 of a profile 2 also drilled before hand.

Each beam 1, 1° may, moreover, be fitted with two series of gussets 14i, 14e provided on its two side faces to enable the attachment of guard rail C or, as will be seen later, the realisation of an additional trestle.

Particularly advantageously, as in the previous patent 2 823 128, each longitudinal beam is in the shape of a caisson with a rectangular section comprising a lower sole 11 and an upper sole 12 connected by two vertical webs 13, respectively internal web 13i and external web 13°.

In the particularly simple embodiment represented on Figures 1 and 2, usable, for instance, for a provisional bridge with military usage, the platform of the bridge consists solely of the upper soles 12 of both beams 1, 1’ between which are inserted junction plates 23 resting simply on the spacers 2 by dint of longitudinal profiles 20 thus forming wedging members whereof the height may be adjusted so that the upper faces of the junction plates 23 lie at the same level as the soles 12, 12" and form therewith a continuous floor B.

The distance between the axes of the beams 1, 1° may be determined so that the upper soles 12 of both beams 1, 1’ form two lanes for the circulation of the vehicles directly on said soles, the latter being treated, for instance scored, for correct adhesion. In such a case, the plates

® 8 23 inserted between the soles 12 and resting on the spacers 2 by distributed regularly profiles 20 may consist of simple grates.

Such an embodiment enables a particularly simple and rapid construction of a bridge with one or several circulation lanes from several series of prefabricated elements, respectively beam elements in caisson, spacers, longitudinal profiles and junction plates.

For example, for crossing a river, the beam elements 1 may be assembled on the bank to form a beam of required length which may be, either lifted as a single block or pushed longitudinally, the quadrangular section caisson of the beam enabling to avoid the risk of tipping.

Both beams being laid side by side, at the required distance, on two spaced apart resting points D, the spacers 2 are bolted to the gussets 14, the longitudinal profiles 20 are laid on the spacers and the consecutive panels 23 can then be placed to form the platform B of the bridge.

If the necessary lifting vehicles are available, one may also realise the trestle on the bank while placing the spacers 2 beforehand, and possibly, the longitudinal profiles 20 before launching the assembly of the trestle to lay it on both spaced apart resting points.

From a trestle thus provided, it is easy, in case of need to widen the bridge in order to realise a second circulation lane. Indeed, a third longitudinal beam may be realised by butt-joining prefabricated elements and this beam is then pushed onto the existing trestle then spaced apart therefrom to be placed at the required gap by lifting means mounted on the trestle. The new beam being also fitted with attachment gussets 14, it is possible, from the existing trestle, to place and to bolt the spacers 2 then the longitudinal profiles 20 and finally to lay the junction plates 23.

The same technique may be used for the realisation of a definite bridge, with a concrete platform. Said platform may consist of prefabricated slabs which rest directly on the upper soles 12 of both beams 1, 1" and on the spacers 2, by dint of the profiles 20.

But it is possible, also, to realise the junction between the upper soles 12 by dint of simple thin plates laid on the profiles 20 and situated in the extension of the upper faces of the soles 12 of both beams, the assembly forming thus a permanent framework whereon may be cast a continuous slab. In such a case, the soles 12 are advantageously fitted with

@® 9 _ connectors welded to the soles and sealed in the concrete for ensuring interlocking of the slab with both longitudinal beams.

According to another characteristic of the invention, applicable in particular in case when the platform consists of concrete, it is particularly advantageous to connect to one another the consecutive elements of a beam by joints, as represented schematically on Figures 3 to 6.

In such a case, indeed, as shown on Figures 3 and 4, two consecutive beam elements 1a, 1b are connected to one another, at their lower section, by a hinged linking means 3 and bear upon one another, at the upper section thereof, by a wedging means 4.

The hinged linking means 3 includes at least two linking parts 31, 32 attached respectively to the ends of both beams 1a, 1b at the level of their lower soles 11 and fitted with orifices 33 which, after mounting the beams 1a, 1b, are aligned for threading an interlocking rod 34.

To this end, as shown on Figure 3, the ends 11’, 12°, 13’, respectively of the lower sole 11, of the upper sole 12 and of each web 13, are recessed relative to the junction plane Q between two consecutive elements 1a, 1b, so that each linking part 31, 32 attached to the end of an element 1a, 1b contains a section 31’, 32’ protruding beyond the junction plane Q and wherein is provided an orifice 33 centred on an axis 30. When assembling the elements 1a, 1b, both protruding parts overlap and the orifices 33 are centred on the same axis 30 placed in the junction plane Q, a rod 34 being then threaded into the orifices thus aligned.

Both consecutive beam elements 1a, 1b, are hence hinged, at their lower section, around the axis 30 and have a tendency to rest on one another at the upper section thereof, under the effect of the own weight of the elements and of the loads applied. This resting point is provided by dint of a wedging means consisting, at the end of each beam, of a flat bar 41 forming a transversal wedge having an internal edge 42 welded to the end 12’ of the upper sole 12 and an external edge 43 placed substantially in the junction plane Q.

As shown on Figures 3 and 4, both these two linking parts form cappings, respectively a female 31 and a male capping 32, nesting into one another.

o 10 ®

The female capping 31 consists of two plates whereof one is represented in perspective on Figure 5, which are welded on both sides of each web 13 of the beam element 1a as well as to the lower sole 11. To the opposite end of the adjoining element 1b is attached the male capping 32 consisting of a plate fitted with a middie slot nesting on the lower section of the web 13 of the element 1b and is welded thereto as well as to the lower sole 11. The ends 31’ of both sections of the female capping 31 are tapered so as to provide a space wherein the end 32’ of the male section 32 engages, these protruding parts 31’, 32’ being fitted with orifices 33 wherein the interlocking rod 34 is threaded.

Obviously, it is possible, for better distribution of the loads, to arrange several hinged linking parts 3 on the width of the longitudinal beams 1.

It is also possible, in the embodiment represented on Figure 5, to equip the adjoining ends of both beams 1a, 1b with a number of flat bars 35a, 35b spaced apart from one another so as to provide cappings wherein fish plates 36 may be inserted, whereas the flat bars and the fish plates are fitted with holes which are aligned along two axes letting through two linking rods 34’.

As indicated above, both consecutive beam elements 1a, 1b thus hinged at their lower section bear upon one another, at the upper section thereof, by dint of a wedging means 4 consisting, at the end of each beam element 1a, 1b, of a flat bar 41 extending transversally to the longitudinal axis of the beam, over the whole width of the upper sole 12 and welded to the end 12' thereof along an internal edge 42. Moreover, both wedges 41 welded respectively to the soles 12 of both beam elements 1a, 1b rest over one another by an external edge 43 which, after mounting both beam elements, is placed in the junction plane Q running through the hinge axis 30.

Preferably, as shown on Figure 3, both wedges 41 have a wedge- shaped profile whereof the thickness increases between the internal edge 42 which has a thickness equal to that of the upper sole 12 and the external edge 43 whereof the thickness is designed for absorbing the horizontal strains resulting from the resting of both elements over one another under the effect of the load.

@® 11 ®

Each wedge 41 protrudes from the upper sole 12 and is welded to the upper parts of the ends of both webs 13 of the beam which are fitted with a scalloping whose profile matches that of the wedge 41.

Moreover, at both its ends, the wedge 41 is supported by two vertical gussets 15 extending as a bracket from a transversal corner piece 16 attached to the external edge of the vertical wedge 13.

As shown on Figure 1, the corner pieces 16 attached respectively to both webs 13 of the beam may be used, inwardly, for bolting a spacer 2 and, outwardly, for attaching a guard rail C.

On the other hand, the corner pieces 16a, 16b attached to the facing ends of both adjoining beam elements 1a, 1b are fitted with orifices 16’ for letting through a pre-stress bar 17 once placed under tension and whereof the ends are threaded for engagement of a nut which is not represented.

Consequently, for the construction, for instance, of a bridge for crossing a river, the trestle elements A each including two beam elements 1, 1" may be assembled on the bank by nesting their linking parts 31, 32 into one another, each beam element being fitted, at one end with a female part 31 and at its other end with a male part 32.

The joints may be assembled on the flat and, after assembly, the bars 17 once placed under tension are run through the orifices 16 so as to apply over one another the external edges 43 of the opposite wedges 41.

Thus, the consecutive trestle elements may be assembled to one another on the bank, and after placing slings, are raised by a lifting means such as a crane to be placed on two spaced apart piers D, as represented schematically on Figure 6.

However, when the trestle is launched by longitudinal thrust from the bank, it may be useful not to block the joints and to let, conversely, said joints open up.

During the launching process, indeed, the foremost element has a tendency to topple downward when its centre of gravity protrudes from the resting point on the abutment. Its front end then comes down and may rest on a pontoon. It is therefore not necessary any longer to place a counterweight at the rear in order to compensate for the cantilever.

The launching process may then carry on by moving the pontoon forward with the element supported up to the opposite bank whereon a

® 12 ® lifting vehicle may raise the front end of the trestle to make it rest on the second abutment.

According to another particularly advantageous feature of the invention, the width of the wedges 41 may be adjusted so as to confer the trestle thus formed, an elongated profile having, for instance, as shown on

Figure 6, a convexity turned upward so as to provide, between the upper level of the trestle and the level of the resting points D, a jib f enabling to compensate for the deflection of the beam under the effect of its own weight and of the loads applied in operation. Indeed, since the successive trestle elements are hinged over one another at their lower part, the width | of both wedges 41 may be adjusted so as to leave, after resting, a certain aperture which determines an angle (i) between the planes of the upper soles 12, 12b of two consecutive elements 1a, 1b.

It is thus possible to bring prefabricated beam elements and spacers to the site, so as to provide trestle elements which are then attached in succession so as to form a trestle. Said trestle may then be lifted as a single block or pushed to make it rest on abutments or spaced apart piers.

For relatively long ranges requiring a certain number of consecutive trestle elements, it is possible to provide a pre-stress over the whole length of the trestle by means of cables 18 running in guides attached to the webs 13 of the beam elements, and resting, at their ends, on the first and the last elements A of the trestle, the positions of the guides being determined so as to confer the pre-stressed cables a profile which is calculated in relation to the loads to be supported.

As indicated above, the circulation platform may consist, simply, of the upper faces of the soles 12, 12° and the plates 23 inserted therebetween.

However, the use of hinged beam elements for the realisation of a trestle having slightly convex upward profile is particularly interesting in case when the platform of the bridge consists of a concrete slab extending over the whole length of the trestle, as represented schematically on Figure 7.

As indicated above, this slab 5 may be cast on the continuous floor (B) consisting of the soles 12 of the beams 1 and the tapered plates inserted therebetween, the assembly forming a permanent framework. But it

® 13 ® is also possible to realise the slab in the form of prefabricated concrete elements laid after one another and between which are provided concrete joints so as to provide a continuous slab.

As in the case of Figure 6, the longitudinal beams 1 consist of a series of consecutive elements 1a, 1b, 1c... whereof the adjoining ends are connected, at their lower sections with joints 3 and are held spaced apart from one another at their upper sections so that their upper soles 12a, 12b are placed in planes forming to one another a determined angle so that the whole longitudinal beam is conferred an upwardly convex lengthwise profile.

As previously, wedging means 4 are interposed between the upper soles 12a, 12b. However, in case when the bridge is covered with a concrete slab, the longitudinal beams 1 are associated with a means for maintaining their lengthwise convex profile at least during the casting and the hardening of the concrete slab, the wedges 41a, 40b being slightly spaced apart from one another, as shown on Figure 8.

In the case of Figure 7, this means for maintaining the profile of the beams 1 contains a set of tie rods 6 resting on the concave lower face of the beam by thrust rods 61 forming a suspender at each joint 3, the beam 1 being thus under-streched.

After casting the slab 5 and hardening the concrete, the tension of the tie rods 6 may be slightly reduced so that, under the effect of the own weight of the trestle, the jib thereof diminishes, the concrete 5 being compressed until the wedges 4, placed at the upper section of the beams are resting over one another.

As indicated above, the upper soles of the beams 1, 1’ are fitted with protruding parts forming connectors, which are sealed in the concrete slab 5 so that said slab is interlocked with the beams and partakes of the resistance of the assembly.

In the embodiment of Figure 8, two consecutive elements 1a, 1b of the beam are connected, at their lower sections, by a joint 3 of the type described above and, at their upper sections by a linking member of variable length 60 which, in the example represented, consists of two sand boxes each comprising a cylindrical body 62 and a piston 63 hinged respectively, on the vertical wedges of both elements 1a, 1b and delineating

® 14 an internal chamber 64 filled with sand and fitted with an orifice 65 closed by a removable plug.

As shown on Figure 8, when casting the slab 5, the sand boxes 60 are adjusted so that the ends of the wedges 41a, 41b are slightly spaced apart from one another. After casting and hardening of the concrete, the orifices 65 are open and the sand 64 may escape while enabling the upper sections of both elements 1a, 1b to come closer to one another until their wedges 41a, 41b are rest over one another, whereas this closing-in process determines the compression of the concrete 5 under a preset load.

However, other arrangements are possible, for instance the replacement of the sand boxes with simple hydraulic cylinders.

Obviously, the invention is not limited to the details of the embodiments have just been described by way of simple example, but also covers all the variations using equivalent means.

Thus, Figures 6 and 7 represent a hinged trestle resting on two spaced apart abutments D and wherein the beam elements 1a, 1b... are hinged at their lower sections. In the case, however, of a bridge resting on an intermediate pier D’, it would be advantageous to place thereon an intermediate element 10’ connected to the adjoining elements 1e, 1f of both trestles with joints 3’ placed at the upper soles of the beams, to confer both trestles an upwardly convex elongated profile.

Moreover, since the beam elements 1a, 1'a are fitted, on their side faces, with attachment gussets 14i, 14e spaced apart regularly, it is possible of offset longitudinally one of the beams 1 relative to the parallel beam 1’ by a distance equal to the spacing between two attachment members 14. In such a case, it is still possible to lay the spacers 2 and to attach them to the side faces of both beams 1, 1’ but the offset enables, advantageously, to realise a slant bridge, the direction of the trestle forming a non-right angle with the direction of the resting point D.

The modular bridge which has just been described exhibits therefore multiple advantages and, in particular, taking into account the lifting vehicles which may be available for the realisation and the implementation of a trestle, it is possible to use caisson elements of a great length, for instance some ten metres. Such elements may, indeed, be realised in the factory and brought by road onto the building site, whereas the latter may be

® 15 ® supplied with 12-metre containers which enables to have the required number of all the necessary elements, i.e. the caisson beam elements fitted beforehand with their attachment gussets and with their joints, the transversal sleepers, the longitudinal profiles and the junction plates as well as diverse accessories such as, for instance, the guard rail elements or sidewalks which may be attached to the side faces of the external beams by short spacers.

In this view, it should be noted that on top of its aesthetic aspect, the modular bridge according to the invention exhibits the advantage of not limiting the circulation gauge between both carrier beams, as in the case of the BAILEY -type bridges, the superstructure being laid on the upper face of the carrier beams.

The realisation of a trestle by means of prefabricated elements hinged after one another exhibits therefore numerous advantages.

However, in certain simple cases, the beam elements might be simply attached after one another to realise continuous beams of variable length.

Besides, the use of caisson beams with a rectangular or trapezoidal section is particularly advantageous, but beam elements having another section, for instance an I-shaped section with a single web may also be contemplated.

Claims (32)

1. A modular metal bridge comprising a substantially horizontal platform (B) resting on two longitudinal beams (1, 1’) said bridge being 5S realised by on-site assembly of at least three series of elements prepared beforehand, respectively, a series of longitudinal elements (1a, 1b...) each comprising two substantially horizontal spaced apart soles, respectively lower (11) and upper (12) soles, connected by at least one substantially vertical web (13), said beam elements (1a, 1b...) being butt-jointed to form at least two parallel longitudinal beams spaced apart from one another, a series of transversal spacers (2) spaced apart longitudinally, each having two ends fitted with removable attachment means on matching parts of the beam elements, and a series of junction elements (23) between the upper soles of the beam elements, characterised in that the upper junction elements (23) rest on the transversal linking spacers (2) between the elements (1a, 1b) of both beams (1, 1’) by dint of wedging members (20) whose height is adjusted so as to provide a continuous floor (B) at the upper faces (12) of the upper soles of the longitudinal beams (1, 1’).

2. A metal bridge according to claim 1, characterised in that the upper junction elements are formed by a series of rectangular plates (23) resting on the transversal spacers (2) by dint of longitudinal profiles (20) whereof the height is adjusted so that the upper faces of said plates (23) extend at the upper faces of the upper soles (12) of the longitudinal beams to form a continuous floor (B).

3. A metal bridge according to one of the claims 1 and 2, characterised in that the upper soles (12, 12’) of the beam elements (1, 1’) form two lanes for vehicles running on the bridge.

4. A metal bridge according to claim 3, characterised in that the upper soles (12, 12’) of the beam elements (1, 1’) have been treated to promote the adhesion of the vehicles driving on the bridge.

5. A metal bridge according to one of the previous claims, characterised in that the junction plates (23) between the upper soles (12, 12’) of the beams (1, 1°) consist of grate.

6. A metal bridge according to one of the previous claims, characterised in that each transversal spacer consists of a metal profile (2)

® 17 - 2006/ 00958 ® having two ends (21) each bolted to a fastening gusset (14) provided on a side face 13 of a longitudinal beam element (1, 1’).

7. A metal bridge according to claim 1, characterised in that the junction elements consist of concrete slabs resting, on the one hand, on the upper soles (12, 12’) of the longitudinal beams (1, 1’) and, on the other hand, on the transversal spacers (2) by dint of wedging means (20) having a determined height to define a continuous platform.

8. Metal bridge according to one of the previous claims, characterised in that each longitudinal beam element (1, 1’) forms a hollow caisson with a quadrangular cross-section having two substantially horizontal faces forming the soles, respectively upper (12) and lower (11) soles of the beam and two side faces (13i, 13e).

9. A metal bridge according to one of the previous claims, characterised in that the upper soles (12, 12’) of both beams (1, 1’) and the plates (23) extending therebetween form a permanent framework for casting a concrete slab (5) covering the assembly.

10. A metal bridge comprising a platform resting on at least two longitudinal beams (1, 1’) each consisting of a series of elements prepared beforehand (1a, 1b...) and butt-jointed by their adjoining ends, and wherein two consecutive elements (1a, 1b) of a longitudinal beam (1) are connected to one another, at the level of their lower soles (11a, 11b), by a linking means (3) hinged around a transversal axis and bear upon one another, at the level of their upper soles (12a, 12b), by a transversal wedging means (4), characterised in that the width of each wedging means (4) is adjusted to confer the longitudinal beam (1), between two spaced apart resting points (D), an upward lengthwise convex profile and having a jib (f) sufficient to compensate for the downward deflection of each beam (1) under the effect of the own weight of the bridge and of the loads applied.

11. A metal bridge according to claim 10, characterised in that the hinged linking means (3) between two consecutive beam elements (1a, 1b) comprises, at the end of each element (1a), at least one longitudinal part (31) for connection with a corresponding part (32) of the adjoining element (1b), each linking part (31, 32) being attached to the lower sole (11) of the element (1) and having at least one portion (31°, 32’) protruding past the end (11) thereof and wherein is provided an orifice (33) with a transversal AMENDED SHEET (ARTICLE 19)

® 18 ® axis and that, when assembling two consecutive beam elements (1a, 1b), the portions (31°, 32’) protruding from the linking parts (31, 32) overlap so that the orifices (33) are aligned and centred on the same transversal axis (30) for threading an interlocking rod (34).

12. A metal bridge according to one of the claims 10 and 11, characterised in that the wedging means (4) between the upper soles (12) of two consecutive beam elements (1a, 1b) comprises, at the end of each element, a wedge consisting of a flat metal bar having two parallel transversal edges, respectively an internal edge (42) welded along one end (12) of the upper sole (12) and an external edge (43) bearing, when assembling two consecutive beam elements (1a, 1b), against an external edge (43b) of the corresponding wedge (41b) of the adjoining element (1b), each wedge (41) having a preset width so that, after mounting two consecutive beam elements (1a, 1b), their upper soles (12a, 12b) are placed in planes forming to one another a set angle | so that the whole longitudinal beam follows the lenghtwise profile requested.

13. A metal bridge according to one of the claims 10 to 12, characterised in that, after mounting two consecutive beam elements (1a, 1b) and installing the wedging means (4), the adjoining ends of both beam elements (1a, 1b) are connected, at least provisionally, at the upper part thereof, by a linking means (17) ensuring interlocking of both consecutive elements so that all the elements behave like a continuous beam for the transport and the placement thereof.

14. A metal bridge according to claim 13, characterised in that the upper linking means between two consecutive beam elements (1a, 1b) is at least one longitudinal bar (17) fitted with clamping means for compressing the wedging means (4).

15. A metal bridge according to one of the clams 9 to 14, characterised in that the whole platform (B) of the bridge is covered with a concrete slab (5) cast on the upper soles (12) of both beams (1, 1’) and the junction plates (23) and that the longitudinal beams (1, 1’) have an upwardly convex lengthwise profile having a jib (f) adjusted for compressing the concrete (5) by downward deflection of said beams (1, 1’) under the effect of the own weight of the bridge and of the loads applied.

® 19

16. A metal bridge according to claim 15, characterised in that each longitudinal beam (1) consists of at least two consecutive elements (1a,

1b...) whereof the adjoining ends are connected to one another, at least at their lower section by a joint (3) enabling to confer the beam (1), between two spaced apart resting points (D), an upwardly convex elongated profile, said beam (1) being associated with a holding means (6) of said elongated convex profile, at least when casting the concrete slab (5) on the platform (B) of the bridge.

17. A metal bridge according to claim 16, characterised in that each hinged longitudinal beam (1) is supported by a set of tie rods (6) resting on its concave lower face by thrust rods (61) forming a suspender at each joint

(3).

18. A metal bridge according to claim 16, characterised in that each longitudinal beam (1) consists of at least two consecutive elements (1a,

1b....) connected on the one hand, at their lower part, by a joint (3) around a transversal axis and on the other hand at the upper part thereof, by at least one linking member (60) of variable length for maintaining the lenghtwise convex profile of the beam (1) between two spaced apart resting points (D), at least until the concrete slab (5) has hardened.

19. A metal bridge according to claim 18, characterised in that the length of the upper linking member (60) between two consecutive beam elements (1a, 1b) is adjusted to confer each longitudinal beam (1), between two spaced apart resting points (D), an upwardly convex lengthwise profile and that, after casting a concrete slab (5) on the platform and hardening thereof, the consecutive elements (1a, 1b) rest, at the upper part thereof, by a wedging means (4) determining the profile of the longitudinal beams (1, 1’) whereof the downward deflection, under the effect of the own weight and of the loads applied, determines compression of the concrete of the slab

(5).

20. A metal bridge according to one of the claims 18 and 19, characterised in that the upper linking member (60) between two consecutive beam elements (1a, 1b) consists of at least one hydraulic cylinder having a body and a piston rod hinged respectively on each of the consecutive elements (1a, 1b).

® 20

21. A metal bridge according to one of the claims 18 and 19, characterised in that the upper linking member between two consecutive beam elements (1a, 1b) consists of at [east one sand box (60) comprising a body (62) and a piston (63) resting respectively on each of the beam elements (1a, 1b) and delineating a chamber (64) filled with sand with a drain port (65) enabling partial discharge of the sand after casting and hardening of the concrete slab (5) for the compression thereof by reducing the jib of the longitudinal beam (1).

22. A metal bridge according to one of the claims 10 to 21, comprising a superstructure resting on at least three spaced apart resting points, respectively two end abutments (D) and at least one central pier (D), the superstructure including a platform resting on at least two longitudinal beams (1, 1’) consisting of prefabricated butt-jointed elements having two vertically spaced apart soles, respectively lower (11) and upper (12) soles, characterised in that at each central pier (D’), each longitudinal beam contains a central element resting on the pier and having two ends connected to the adjoining ends of the beam elements (1e, 1f) surrounding it, with joints (3') with a transversal axis placed substantially at the level of the upper soles (12), the other elements of each beam (1) being connected to one another with joints placed substantially at the level of their lower soles (11).

23. A metal bridge according to one of the previous claims, characterised in that each longitudinal beam element is fitted, along at least one side face (13), with a plurality of gussets (14) spaced apart regularly for attaching at least one transversal spacer (2).

24. A metal bridge according to claim 23, characterised in that the elements (1a, 1'a) of two parallel beams (1, 1') are spaced apart longitudinally by a distance corresponding to the gap between two successive gussets (14) for attaching a spacer (2) so as to provide a cross trestle relative to its resting points (D).

25. A manufacturing method of a metal bridge, characterised in that a series of longitudinal beam elements (1a, 1b...), a series of spacers (2), a series of longitudinal profiles (20) and a series of upper junction panels (23) are provided beforehand, said series being brought to a building site of the bridge comprising at least two spaced apart resting points (D), at least two

@® 21 longitudinal beams are built each composed of at least two beam elements (1a, 1b) butt-jointed, a bridge trestle is placed on both resting points (D) consisting of two longitudinal beams (1, 1') connected together by the spacers (2), at least two longitudinal profiles (20) are laid on said spacers (2) and on said profiles (20) are laid a series of consecutive panels (23) extending between the upper faces of the longitudinal beams (1, 1’) and forming therewith the platform (B) of the bridge.

26. A method according to claim 25, characterised in that, after having provided two longitudinal beams (1, 1’) each composed of at least two consecutive elements (1a, 1b), both beams (1, 1’) parallel to one another are laid on two spaced apart resting points (D) and spaced apart from one another, the spacers (2) are laid, fastened at their ends (21) on the side faces (13) of both beams (1, 1’), the longitudinal profiles (20) are laid on the spacers (2), and the plates (23) are laid on the profiles (20).

27. A method according to one of the claims 25, 26, characterised in that the longitudinal beams (1, 1’) are prepared beforehand by butt-joining of beam elements (1a, 1b...) and are launched by longitudinal thrust from one of the resting points (D).

28. A method according to claim 27, characterised in that, each longitudinal beam (1) consisting of at least two consecutive beam elements (1a, 1b) whereof the adjoining ends are connected at their base by a transversal joint (3), the first beam element placed foremost is lowered when launched by a thrust from a first resting point, while rotating round its joint and is laid on a support associated with the front end of said first element up to the second resting point, the latter being equipped with a lifting means which raises the first element for bringing it in alignment with the following element and lays it on said second resting point.

29. A method according to one of the claims 25 to 28, characterised in that, after having provided a bridge trestle consisting of two longitudinal beams (1, 1’) connected by spacers (2) and junction plates (23), at least one third longitudinal beam is laid on at least one side of the trestle, said third beam being parallel and spaced apart from one of the beams of the trestle by a distance corresponding to the length of the spacers (2), a series of spacers (2) are laid, said spacers (2) being fastened at their ends (21) on said spaced apart beams, longitudinal profiles (20) are laid on the spacers

® (2), then a series of junction plates (23) are laid on the profiles (20), the width of the platform (B) being thus doubled.

30. A method according to claim 29, characterised in that the third longitudinal beam is pushed longitudinally on the trestle already built then placed at the required distance by lifting means mounted thereon.

31. A manufacturing method of metal bridge trestle comprising two longitudinal spaced apart beams (1, 1’) each having an upper sole (12) and a series of junction elements (23) arranged between the upper soles (12, 12’) of both beams (1, 1’), at the level thereof, so as to provide a platform (B), characterised in that both longitudinal beams are conferred an upwardly convex lengtwise profile and that the platform is covered with a concrete slab (5) made of at least one portion, said slab (5) being compressed by the downward deflection of both beams (1, 1’) under the effect of the own weight of the bridge and of the loads applied.

32. A method according to claim 31, characterised in that the longitudinal beams (1, 1’) consist of butt-jointed elements (1a, 1b...) whereof the adjoining ends are connected at their lower part with transversal joints (3) enabling to confer each longitudinal beam (1) an upwardly convex lengthwise profile, that each beam (1) is associated with means (6, 60) for maintaining a determined gap between the upper parts of the adjoining ends of the beam elements (1a, 1b) for maintaining the lengthwise convex profile during the realisation of the concrete slab (5) and that, once the concrete has hardened, said upper parts of the beam elements (1a, 1b) may be brought closer to one another for compressing the slab (5) by reducing the jib (f) of the hinged longitudinal beams.