TO PREPARE A BEAM FOR THE FLOATING BRIDGE

Field of the invention.

The present invention relates to a device for a floating bridge to form a transport connection between two land attachment points over a sound or fjord, where the floating bridge is comprised of a bridge beam assembled from a plurality of mutually joined pipe sections, assembled end to end, as is given in the preamble to claim 1 . Further, the invention relates to a method of production of a bridge beam for a floating bridge for a transport lane between two attachment points over a sound or a fjord, toward shore, where the bridge beam is assembled of a plurality of pipe sections, end to end, as is given in the preamble of claim 10. Further, the invention relates to a raft that is used during the assembly of the bridge beam, as is given in the preamble to claim 14.

Background of the invention.

Specifically the invention relates to a floating bridge that can be installed between land attachments in each end, and operated both in calm and stormy seas with large waves and sea swells. If desired, it can be combined with a passage for a ship. It can also cross very wide fjords and sounds, readily those with widths from 10 - 20 km. By floating bridge it is meant a construction that can be arranged as a roadway, with for example many driving lanes, for the transport of people and vehicles, and optionally a rail track for train operation.

By a bridge beam, it is meant a hollow body shaped as an elongated box shaped , formed of plates assembled around a structural framework. The roadway is arranged either directly upon the bridge beam, on a viaduct that is supported by columns upon the bridge beam, or inside of the hollow part of the bridge beam. Such a hollow bridge beam is normally composed of a number of pipe sections.

In the following specification it is further described that the bridge beam is substantially horizontal when extending over the water. But, it also allows that the bridge beam can, to some extent, bend upward in the vertical plane to follow the roadway. This could be used if someone wished to increase the vertical distance from the surface of the water to a part of the bridge. For example, to allow a ship to pass directly under the roadway, or to make the exits of the floating bridge to the land attachments, further up in the terrain. Such a vertical deflection of the bridge beam will preferably follow the roadway, i.e. with a typical gradient of 1 - 6%.

By floats, it is meant a float or pontoon in the sea that supports the entire bridge beam across the floating bridge's length. The floats to a floating bridge are preferably made from concrete, but can also be built of steel. The floats are placed with a mutual spacing calculated to ensure the necessary buoyancy and stability for the floating bridge. At the same time, the effects of environmental forces on the floating bridge are minimized. A typical distance between the floats can be between 50 - 100 meters.

The floating bridge according to the invention is oriented to span over fjords or sounds where the water depths can range from about 5 meters to 2000 meters deep. The attachment points to the floating bridge can either be attached to land on each end, or to another fixed installation. The attachment points preferably form a continuation of the roadway in the extension of the floating bridge.

The invention is comprised of a floating bridge composed of a closed bridge beam that rests on a the floats above the waterline and that connects the floating bridge between the attachment points, such that it forms a connected floating bridge between the attachment points. If desired, parts of the bridge can be replaced with a ship passage for larger ships at a place along the floating bridge. The road traffic could pass over the ship passage. Another possibility is that the bridge beam is arranged with a moveable floating bridge segment that can periodically open to let ship traffic pass through the bridge; while road and train traffic is stopped.

The ship passage can, if desired, also be arranged such that an underwater structure forms an integrated structural part of the floating bridge between the attachment points. The underwater structure can have another design than the bridge beam, for example: trusses. The purpose is that the ship passing can occur over this underwater structure, through the floating bridge. Prior art.

With very large distance over the fjords or seas, the floating bridge can be a cost effective and safe alternative. Floating bridges have been known for a long time and are in use in several places in the world. Crossing of fjords, sounds, and seas with bridges has been a challenge since time immemorial. Different types of bridges have been developed depending on the span, foundation possibilities, and mast clearance heights. This is referenced in patent publications US-1852338, SE-458850, NO-1 13404 and GB-2135637, JP- 2010037802, NO-171 .436, CN-203960729, CN-101 1 17793, GB-9391 19, KR- 100758200, and CN-203684099.

However, none of these publications deal with floating bridges with interconnected sections which is the aim of the present invention. A number of floating bridges are built with lateral anchoring, which is evenly spaced along the entire floating bridge and is usually on both sides, to hold the bridge in position.

The environmental forces on a floating bridge can be considerable, especially during storms; where current, wind, and waves can come both laterally and from the same direction. In addition, tidal water forces occur with variation of water levels as they ebb and flow. This can cause bending forces on the floating bridge near the shore. It is therefore important that it is designed to minimize the effect of environmental forces.

An example of a floating bridge that was adapted to sheltered waters is the Nordhordalandsbrua in Norway; which is anchored with two land attachments. The bridge, with its 1246 meter roadway, is the longest in Europe without side anchoring. This floating bridge does not allow the passage of ships. But this problem was solved by building an additional solid tall bridge near land. This solid bridge has a mast clearance height of 32 meters and a mast clearance width of 50 meters.

The Nordhordlandsbroen has a roadway that is 16 meters wide. The floats are shaped like barges and built in concrete. The floats are 40.0 meters wide along the direction of the width of the road and are 20.5 meters long along the longitudinal direction of the road. The free distance between these floats is about 1 10 meters. All of the floats lay across the direction of the roadway to minimize the effects of the current; such that the water at the surface flows almost unimpeded under and between the floats.

In addition to anchoring at the end points, the floating bridge can also be held in place with the help of lateral mooring lines. The floating bridge's movements are a direct result of the response of the floats to incoming environmental forces in the 6 known degrees of freedom. The structural stress in the bridge beam is a function of the floats response to motion, the bridge beams design, and the individual distance between the floats. A floating bridge can be designed using techniques and constructive solutions such that the floats' dynamic response to the waves is minimalized. At the same time, the structural stresses in the bridge beam can be made acceptable; usually from column shaped structures with a small waterline area. Weather statistics gathered over many years indicate the dominating and likely directions for environmental forces such as wind, waves, and currents. During the planning and designing of the floating bridge, this information can be utilized.

The proliferation of floating bridges has been limited mainly due to an inability of allowing for ship passage. For the Nordhordlandsbro, this has been solved by connecting it to a solid tall bridge that gives the possibility of ship passage close to shore. However, ship passage near land is often not desirable, and in patent application NO 20101273, a specific solution for a floating ship passage that allows shipping lanes to go through the floating bridge far from land is disclosed.

The expression "pipe sections" refers to the hollow modules that the floating bridge is composed of. These can comprise hollow steel structures with a typical length of 50 - 150 meters, formed as an elongated hollow box shape of plates mounted like a closed box structure, with interior beams and rods in trusses that can support the roadway or support columns for a viaduct with the roadway. Normally making connections of the pipe sections in a bridge beam primarily above the water is a demanding, extensive, expensive, and risky operation. This is, because the connections are made with the use of series of floating bodies. These include the floating bridge's own floats, temporary barges, and crane vessels. Because of the natural motion on the sea, the floating bodies will need to be continuously controlled with the help of tugboats, propulsion units or temporary moorings. At the same time, the joining of pipe sections must be performed with great precision since they are of a large size (length/width/height) and are heavy. Known floating bridges, for the most part, use welding for the connection of pipe sections. But, this takes a long time since such the welding process requires numerous sequential, time consuming operations in the open air. Such preparations include preparation of the welding seams, hydraulic joining of the large and heavy pipe sections, adaptation of the present welding joints, welding operations, after treatment, x-ray and NDT controls, sand blasting, priming, painting, etc. Many of these welding operations have to occur under temporary protection against the weather; which varies with the sun, wind, precipitation, and temperature. Some of these operations require the rigging of a provisional welding tent or other protections: which are constantly being moved to new joints that need welding.

Bolting of the pipe sections is a well known technique with the building of most types of bridges. But one of the disadvantages with using bolts on bridges is that the bolts are often located outside of the structure. They are exposed to wind, weather, and salt spray and they are not easily accessible for later inspection and repair. Over time, the bolts will collect even more layers of paint that will hinder a good inspection of the quality of the surface and the replacement of the bolts.

In the following, the terms bolts and flanges also intend to cover other types of mechanical joining techniques that have the same effect; such as: riveting, hydraulic presses, prestressing rods, etc.

Purpose of the invention.

It is a purpose of the present invention to provide a new structure for the joining of such hollow pipe sections. Further, it is also a purpose to produce a new method for assembly of such floating bridge spans based upon the joining of pipe sections, over a sound between two land attachments. As well as a new method to carry out said assembly. A purpose of the invention is to provide a new joining method of pipe sections for the assembly of floating bridges that makes it possible for bridge beams-pipe sections to be quickly and precisely joined. They are brought together, flange to flange, and joined with the use of screw bolts, flanges, or other known techniques (forces) with great precision and speed.

It is a further purpose to provide a new construction for the arranging of an annular shaped end flange. Each open end of a pipe section is equipped with it for the mutual joining of two adjacent pipe sections.

It is also a purpose of the invention that all of the bolts are easily accessible for inspection, control, and replacement. Also, that the bolts are easy to access with mechanical equipment, i.e. when the bridge beam composite pipe sections are located under water.

It is an additional purpose of the invention that the air environment in the space around the bolt holes can be kept at a low humidity, using known techniques, to reduce corrosion and the need for expensive surface treatments.

It is also a purpose of the invention that the temperature of the air environment in the space around the bolts, if desired, can be held at a desired substantially constant level. This will reduce tension variations in the entire bridge beam structure that is a result of external temperature variations. This will increase the life span of the entire floating bridge construction; especially in geographic areas with large temperature variations.

Moreover, a purpose of the invention is that the bolts shall be protected against saltwater spray from the sea.

It is also a purpose of the invention that the bridge beam can be disassembled by screwing out/up of the bolts and then the hollow pipe sections separated. This allows for entire or parts of the floating bridge to be moved and reused in other places; or that a damaged piece can be replaced.

It is a further purpose of the invention to provide a rational method for the production of a bridge beam for a floating bridge. It is a particular purpose of the invention to reduce the building time for a floating bridge in relation to the earlier known solutions. The present invention.

The pipe section construction according to the invention is distinguished by that

each end of a pipe section in the bridge beam is comprised of an inwardly facing annular flange transverse of the pipe section's longitudinal direction that with the help of a row of bolts are joined together surface to surface with a corresponding inwardly facing annular flange in an adjoining pipe section in the bridge beam and an internal bridge beam cavity is comprised of a transport lane, for the conveyance of personnel together with a means for inspection and maintenance equipment. According to the preferred embodiment is the opposing flange surfaces are orientated across the pipe section's longitudinal direction, and extends around the entire end of the pipe section's periphery, and is comprised of threaded bolts with clamping nuts around the entire perimeter, where the bolts extend through mutually aligned holes through the flanges in the pipe section's longitudinal direction, and where, the flange's surface is clamped together with the help of the clamping nuts, or with a forced construction that grips and tightens against the backside of the flanges.

According an even more preferred embodiment is where each hole on the flange's inside is shaped like a sleeve seat with a bolt channel that is flush with the corresponding bolt channel in the hole in a corresponding seat construction in the adjacent flange construction.

Preferably that when the end portion of the pipe section is comprised of a transverse beam, it also has a flange surface that faces against and links together with a corresponding flange surface on the opposing pipe section. It is preferred that the flange adjoining surfaces comprises a film of copper, sealing felt or a rubberized material to establish a sealing in the joint between two pipe sections, and in particular it is preferred that the sealing film is of a softer material such as copper, or a rubberized or a felt-like material. According to an even more preferred embodiment comprises the bottom part of the beam cavity is comprised of a transport lane, such that a rail track for the conveyance of a means for inspection and maintenance equipment. Preferably the transport lane is formed transport lane is formed by one or more rails or pair of rails mounted to and hanging from the ceiling sections of the transverse frames and end flanges, in that one of the personnel and equipment basket is suspended in longitudinal rails and travels inside through the entire bridge beam. The floating bridge is formed by the bridge beam that rests on a plurality of mutually spaced individual floats along the bridge span in that the joint between two adjacent sections rest directly upon a float.

With the present invention, someone can reduce the time that it takes to join together two sections. Due to the large width and height dimensions of the sections, it will usually take 1 to 2 weeks to weld together just two sections. However, with the present invention, such a job can be done in a day or two. This means a large time and costs savings when compared to previous joining methods. The method according the invention is distinguised by that by the following steps: a) a plurality of pipe sections to shape the bridge span over the sound/fjord, where each pipe section is comprised of inwardly directed annular flange for mounting to a neighboring pipe section in the bridge span, and that

b) a first pipe section is placed by a shore side for connection to a land transport system, where after a second pipe section is placed on a floating assembly raft that is arranged in an suitable position and adjusted in a controlled manner to align the flange end of the second pipe section to be arranged flush against the corresponding flange end to the first assembled pipe section,

c) that the first and second pipe sections are connected by the assembly of threaded bolts and corresponding clamping nuts through respectively aligned holes in the two adjacent flanges, in the said connection performed from the inside of the pipe sections, and

d) after which the assembly raft is maneuvered suitably to place a third pipe section to rest on the raft flush with the protruding end to the said second pipe section, and e) the remaining pipe sections to complete the floating bridge over to the second shore side are assembled in turn and arranged in an analogous manner as described under the process steps c) - d).

The preferred embodiment of the method is given in claims 1 1 -13.

The assembly raft according to the present invention is distinguished in that the deck of the raft is comprised of a transport means that makes it possible for a simple horizontal displacement of a loaded pipe section, said transport means in the form a transport roller or a belt that is connected to a motor and a brake to control a pipe section's motion on the deck of the raft during the assembly, and the assembly raft comprises means for controlled movement in the sea during installation. The prefered embodiment of the assembly raft is given in claims 15-18.

It is preferred that the means to hold and change the assembly raft's position during the assembly, comprised of an adjustable mooring system connected to the raft; the adjustable mooring system comprised of a set of hawsers connected to separated motor driven winches that can either be assembled on the shore sides or onboard the raft. It is further preferred that the assembly raft is comprised of a winch operated first set of hawsers toward shore from each end of the raft is arranged approximately along the bridge beam's longitudinal direction, and optionally a second set of winch operated hawsers that extend out from each side of the assembly raft across said longitudinal direction.

It is further preferred that the assembly raft is comprised of a winch operated hawser set toward shore from each end of the raft is aligned approximately in the bridge beam's assembly raft stabilizes laterally via transverse hawsers that extend out from each side across from the assembly raft's longitudinal direction.

An alternative is to use mooring hawsers, the assembly raft can be comprised of propulsion machinery in the raft's hull in the form of a plurality of azimuth propellers that can be brought down into the sea under the raft and operated, such that the propellers operate based on automatic positioning via satellite navigation, such as a GPS system, or by means of a plurality of electronic transponders that are intermediate placed on the sea bed or on land. A third alternative is to combine the use of hawsers and propulsion. This combination could be advantageous on bridge routes, where there can be a large variation in water depth. Such a combination is known from offshore drilling rigs, and in the field in general, as "mooring assisted dynamic positioning". In shallow water is it natural that the mooring lines are used, but in deeper water, propulsion systems can hold the assembly raft in position.

Description of the figures.

The device according to the invention shall be further explained in the following description, with reference to the accompanying figures, wherein:

Figure 1 shows a horizontal cross section of a floating bridge that is comprised of an elongated bridge beam that rests on a plurality of floats and that spans continuously over a fjord or sound, between two land attachment points.

Figure 2 shows an end view of a pipe section according to the invention. Generally, the pipe sections have a shaped cross section, preferably rectangular, usually with rounded corners. Figure 3 shows an isometric view of the flange structure to joined two opposing pipe sections of the bridge beam, while figure 4 shows an enlargement of figure 3 to illustrate a preferred way of joining flanges; with a row of bolts.

Figure 5 shows a sectional view inside of two joined sections of a floating bridge beam of a floating bridge, wherein it is arranged a longitudinal conveyer, in this case a railway, for the conveyance of both maintenance personnel together with a service vehicle to perform internal inspection and maintenance of the pipe joints and of the interior walls of the joined pipe sections. Figure 6 shows an initial step of the assembly of the floating bridge from the one shore side, and shows a floating assembly raft with maneuvering lines for assembling the pipe sections for the floating bridge. Specifically, the figures shows the second pipe section ready to be joined with the first pipe section connected to the shore side.

Figure 7 shows the continuation of figure 5, where the second section is now joined together with the first section. Figure 8 shows another step in the assembly, where in a fourth section is ready for assembly to the previously mentioned third section, and further that the two prior formed pipe sections joints rest upon their respective floats.

Figure 9 shows a side view of the assembly configuration according to figure 7.

Figure 10 shows a plane view of the assembly configuration according to figure 7, additionally shows a service raft that supplies the assembly boat with pipe sections for assembling.

The same construction details are given the same reference numbers on the different figures. Description of the preferred embodiment of the invention.

The invention shall now be explained in more detail with reference to figure 1 .

Figure 1 shows a floating bridge 10 that spans over a fjord or a sound between two land attachments 1 1 and 13. The floating bridge is comprised of a bridge beam 12 that floats over the water line 21 resting on a plurality of floats 17 along the bridge span. The bridge beam is assembled from a plurality of pipe sections 14, 16, 18, 20, that are mutually join in accordance with this invention to form a bridge beam 12. The sea floor is shown as 15 in the figure. On figure 1 , is the joint between two adjacent pipe sections are shown as 19.

Figure 2 shows an end view of a pipe section 14 in the row according to the invention. The pipe section is shown with a rectangular cross section, and is comprised of a side, bottom, and top surface, where the top surface 20 is itself or forms the base for a transport/driving lane along the floating bridge. An annular flange 30 is arranged facing inwards around the entire inner circumference cross section, such that it forms an outwardly facing flange surface for the system in a vertical plane toward a corresponding flange surface on the end of the adjacent section 16 (figures 1 -5). Where each end of the pipe section 14, 16, 18, 20 is shaped with such a flange surface. To reinforce the hollow pipe section at the opening's surface there is a centrally arrange stiffening post 22 between the pipe sections interior top and bottom. The forward facing part of the post 22 is shapes a plane surface that forms a part of the flange surface that rest against the neighbor section's corresponding flange surface 31 (figure 4).

The perimeter of the flange has through holes bored through it with a plurality of axial borings 32 with generally mutually equal distance. The inside of each hole has a sleeve shaped seat 34 that forms a longer bolt channel that is flush with the corresponding hole 32. Each flange on each end of the pipe section is comprised of such a seat 34 for the affixing of bolts. Figure 3 shows that it is assembled using an upper and a lower row of bolts of 1 1 bolts in each row. Similarly is the vertical flange surfaces (also the extra support surface 34) shown to comprise 6 - 7 bolts in height.

The dimensioning of the bolts and flange connection is performed using traditional methods and available programs. Traditionally, bolts used for bridges often have a diameter of 15 - 27 mm; where one uses a large amount of bolts. For floating bridges, according to the invention, calculations have shown that it may be advantageous to slightly reduce the total number of bolts by using slightly courser bolts; preferably with diameters of up to 50 - 70 mm. The bolts are connected and tightened using well known techniques, such as hydraulic power where the torque force is measured. Other mechanical connections can also be used, for example prestressed cables than can be bolted or cemented in place. Traditional bolting and screw connections are temporary and preferred because of simple and well known processes for replacing them.

Before the two end flanges of the two adjacent pipe sections 14 and 16, respectively, are put together and screwed together with the help of the said bolts around the perimeter, a thin layer of sealing film is placed on the system surfaces to create a secure sealing of the joint 19 between the two pipe sections. This film can be a sealing film of a softer metal such as copper, or a rubberized, or felt film. This is not shown on the figures.

Figure 3 shows an isometric view of the flange structure to joint two opposing pipe sections of the bridge beam, while figure 4 shows an enlargement of figure 3 to illustrate a preferred way joining flanges; with a row of through bolts. With reference to figure 5 some significant features of the invention will be discussed. The row of bolts that hold the pipe sections 14, 16, 18, 20 together, are placed on the interior of the bridge beam. The bridge beam has such large interior dimensions with regards to height and width, that the maintenance of the row of bolts, seals, and the inner surfaces of the sections (surface treatments, etc.) can be performed from the inside by personnel or with robots that can maneuver inside of the bridge beam.

To facilitate the conveyance of both personnel and equipment for the inspection and maintenance, the hollow cavity of the bridge beam is arranged with one or more transport lanes. Where there are several such lanes, they are arranged mutually parallel on the bottom of the bridge beam's interior as indicated by the two rails ways 120A and 120B on figure 5. It is essential to arrange the transport over separate lanes as a single piece over the bottom surface 102 itself. This is because, the bottom beams to the transverse truss frames 122 between each of the section ends and the corresponding flange pieces 30/31 to the two nearest corresponding section ends 14/16, 16/18 extends upwards from the bottom surface. Otherwise, would be a hindrance for the conveyance.

The transport lane is preferably a separate road/gangway or a railway 12A, 120B, i.e. one or more parallel longitudinal partial lanes. The transport lanes can rest on the bearing columns that are supported by the floor/bottom 1 12 or rest on the bottom pieces on the inside of the transverse truss frames 1 12 that are placed regularly between each end of the sections 14/16, 16/18, ... thus it is also an advantage with a rail way mounted on top of the flanges 30/31 ; 122, since the bottom 122 is not even but is comprised of the upwards extending transverse flange portions. The cart 102, here shown as a cart that can move on a pair of rails, can be comprised of a lift with a personnel and equipment basket 104, mounted to a moveable lift arm 104. Figure 5 shows two transport railways 120A and 120B; each with its own cart that carries its own basket 106.

According to an alternative embodiment, the transport lane can be shaped of one or more rails or a pair or rails (not shown in the figures) mounted to and hanging from the ceiling sections of the transverse frames and end flanges. A personnel and equipment basket can, in this way, be suspended in longitudinal rails and travels inside through the entire bridge beam. The transport wagon is connected to an electric motor for operation, and provides the required lighting; together will all of the instrumentation for the relevant maintenance of joints and surfaces. The cavity in the bridge beam can be accessed via entrance doors for the passage of equipment and personnel, preferably placed on the shore sides 1 1 and 13 respectively. Instead of the entire bridge beam being composed of continuous hollow section from shore side to shore side, it can also be divided up into several hollow sections with the help of sealed walls with entrance doors. When a bridge beam, for example, is comprised of 10 flange ended pipe sections every 120 meters, it has a closed interior room that can convey personnel and equipment through 1200 meters. Inspection and maintenance can involve controlling the surface treatment, in particular with the row of bolts that hold together two corresponding sections 14/16, 16/18.

It is referred to figures 6 and 10 showing a floating assembly raft 50 that is used to assemble a bridge beam of pipe sections.

In a preferred embodiment, the raft is comprised of a deck for the positioning of pipe sections 16 (figure 2). On the top deck, a glide path is placed for the pipe sections, for example: as shown by a row of parallel rotatable rollers (like a transport roller) 53 where the pipe sections are placed upon, such that it can easily be moved into an assembly position. Horizontal displacement of the pipe section can be performed by jacking mechanisms or hydraulic cylinders, or that the assembly raft is moved with the help of the hawsers and the pipe sections into a new position. Instead of rollers, it is also possible to use custom gliding surfaces based upon known techniques. For example: glide surfaces assembled with Teflon plates that reduce the horizontal friction. The raft is towed to both the shore sides 1 1 and 13 with the help of suitable hawsers 60, 62, 64, 66 mainly longitudinally along the bridge span, and side hawsers 65, 67 (across) that contribute to the rafts 50 lateral stability. The hawsers 60-78 are shown as hawser pairs.

Each hawser pair is maneuvered via separate motor driven winches that either can be assembled on the shore sides or on board the raft 50. The maneuvering of the winches is coordinated and controlled via a computer device (not shown), for example: based on automatic position of a GPS-system, such that the raft can be controlled in a stepwise manner from one shore side 1 1 and over to the other shore side 13 to carry out the assembly of the pipe sections into a bridge beam according to the present invention. The figures show two exemplar winches with rope-coil drums 70 and 71 . The system is also comprises steering with a braking system coupled to rotatable rollers 52, such that these are stationary and do not allow the sections to move on the raft before it is brought forth for assembly. To carry out the maneuvers, the raft 50 can include a wheel house for an operator to steer and oversee the process.

The hawsers are held under a certain tension to secure the position of the assembly raft/barge. The winches are computer controlled and connected together such that the entire assembly raft can be moved while the line tension and raft position can be monitored by the operator.

According to another preferred embodiment, the positioning of the assembly raft 50 is performed with the help of propulsion machines incorporated into the raft's hull, and comprised of a plurality of azimuth-propellers that can be brought down into the sea under the raft. The propeller system operates based on automatic positioning such as from a GPS system. In this embodiment, the mooring lines are unnecessary, even thought the embodiment can also include them as extra security to keep the keep the raft in place for each pipe section as it is assembled. The submersible propeller system and rotatable "thrusters", have suitable redundancy to act as a reserve in the case of power failure, maintenance, accident, etc. These are known techniques and have been used regularly by other types of offshore operations, where the positioning demands are strict, particularly during storms. The advantage with this variation of automatic positioning is that it is not required to put out mooring lines to move the assembly raft to precise positions (parking at sea) as required.

To make the maneuvering simpler, a raft accommodating one single pipe section can be placed upon the rollers, and this is because a pipe section can be very heavy, which can affect how easily the raft can be maneuvered in the sea. To supply the deck of the raft 50 with pipe sections 14,20 ... one after another, a separate supply raft 80 loaded with a plurality of pipe sections can be floated up and moored next to the mounting raft 80. The resupply raft 80 includes a crane 90 suitably placed on the raft 80 (shown positioned in a corner) and dimensioned to lift up a section of the supply raft 80 and set it gently onto the deck (the rollers) 52 on the assembly raft 50. Alternatively, the new pipe sections are transferred to the assembly raft by custom gliding devices which is also mounted on the supply raft 80. As mentioned the bridge beam rests along is span by a plurality of floats 17 to keep the bridge beam stable during the movement of traffic and to withstand the weather forces it is subjected to. Specifically, each joint between two adjacent pipe sections is screwed together and rests on a float 17; which keeps the joint area additional stable.

The joining of the pipe sections to form the integrated bridge beam.

The assembly of the sections to form the bridge beam can be performed as follows, with reference to figures 6 - 10.

The first pipe section 14 is assembled with one end on the shore side as indicated in figure 6, to form a transport connection to a road system on the shore side. This will not be discussed in more detail at this time. This is done by that the section 14 is placed on the raft deck 52, slowly slid over the shore side 1 1 , and joined together. Thereafter, the next pipe section 16 is put over onto the assembly raft 50. This is then maneuvered so that the two opposed flanges 30 and 31 , and attached packing films, on the ends of the pipe sections 14 and 16 are inserted towards each other and aligned, whereupon all the bolts 40 are fitted and used to screw the sections together. To get good precision in the joining of the two flange surfaces, the two surfaces can have guide devices mounted to them, for example: those of a male/female type. This can make it easier to join or separate the two flanges in the two corresponding pipe sections.

The number of bolts and the design of the flanges can be calculated by known techniques. It will depend upon the forces found in bridge beam's pipe sections.

Said levelled of two opposing corresponding pipe sections 14 and 16 may be performed by the base transport rollers 52 in connection with a lifting / lowering driven means so that the section on the raft can be freely raised and lowered on the raft. Alternatively, the raft will be equipped with ballast tanks for air / water filling for regulating the raft's depth.

When the first sections 14 and 16 (figure 6) are positioned, all the mounting bolts 40 are inserted through the holes in the flange and associated tightening nuts 42 tightened until the flange surfaces 30 and 1 at the two corresponding end sections and an intermediate gasket/seal are clamped against each other so that the joint/seam 19 (figure 1 ) is sealed. After the two sections 14, 16 are joined (figure 7), a support float 17 is moved in under the bridge beam and place such that the bridge beam rests with the joint upon the float. This is shown in figure 8. Furthermore, the raft 50 is pulled toward the right such that only the end of the outermost pipe section rests on the raft 50. Cf. figure 5 that shows that the end of the section 14 rests on the raft's 50 left side, while the next section 16 is ready.

Shown in figure 8 are three interconnected pipe sections 14, 16 and 18 while the fourth, no. 20 waits to be joined. The end of the pipe section 18 still rests on the raft to carry out the next joining. The longitudinal mooring cables 60 and 66 shown in the figure allow the raft to pulled / slackened in the desired direction by synchronous maneuvering winches (70, 72 in figure 5). These may optionally be based on a dynamic positioning of the raft using a satellite navigation system, such as GPS. The adaptation and flushing of the raft can, of course be controlled by an operator on board the raft, along with the assembly personnel that are inside the pipe section and making said screwing together.

Further details of the invention.

A typical hollow bridge beam segment has a length of 50 to 150 meters, a width of 8 to 20 meters, and a height of 4 to 8 meters. The assembly raft should preferably, therefore, have a correspondingly larger length. I.e. that when pipe segments are 150 meters long and 20 meters wide, the raft should have a length / width on the order of 200/40 meters. The system surfaces of the adjacent bolting flanges must have good contact to form a satisfactory structural connection that can take up and transfer the occurring forces around the flanges and bolts. These include shear, pressure, and tensile forces that may occur in this connection during operation of the bridge. The pipe sections can be assembled in a straight line along the floating bridge's longitudinal axis or at a small angle, preferably less then 6 - 7 ^Q , dependent upon the desired global curvature of the floating bridge or incline in the vertical plane. Each bridge beam element is preferably rectilinear in the axial direction, i.e. in the floating bridge's longitudinal direction, but may also optionally be produced with a slight curvature, preferably with a larger bend radius greater than 1500 meters. When the assembled bridge beam is closed and secured against the end fasteners 1 1 and 13, it is preferable that the end walls will also be made as sealed as possible. Thereby, the assembled pipe sections form a continuous closed space where air can be conditioned with respect to replacement, temperature and humidity. Experience has shown that steel and iron surfaces at low air humidity have minimal corrosion and there is little need for surface-treatment in terms of priming and painting; which is cost-saving for both construction and operation.

If the floating bridge is longer than 2000 meters, it should be divided into several mutually separate enclosed spaces, which will not affect the structural integrity of the bridge beam and the individual pipe sections. Because the bolting flanges and corresponding bolts, in accordance with the invention, is contained within an enclosure that has moderate transverse dimensions (typical a width of 8 - 20 meters, and a height of 4 - 8 meters), all bolting flanges and bolts of the bridge beam are readily accessible for inspection and replacement from within, and is in completely protected environment.

The roadway on the floating bridge can, by known techniques, be transferred over ship passages either on a high bridge or a movable bridge section.

The floats 17 can be shaped according to the local environmental conditions, such that they cause the least amount of dynamic forces in the bridge beam. In calm water, a float can have a traditional single hull shape, while in exposed regions they, for example, could be shaped as column structures. The float's buoyancy capacity and stability is dimensioned appropriately for the carrying capacity of its own weight and the weight of the bridge beam, bridge equipment, asphalt and traffic. It should also meet security requirements for ship collisions and damage stability

The floating bridge can be without side anchoring or front anchoring in a plurality of mooring lines to meet the functionally requirements of the floating bridge.