GB2135637A

GB2135637A - Modular pontoon bridge

Info

Publication number: GB2135637A
Application number: GB08318720A
Authority: GB
Inventors: Fayren Jose Marvo
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-02-21
Filing date: 1983-07-11
Publication date: 1984-09-05
Also published as: FR2541333A1; GB8318720D0; IT1166981B; IT8323114A0; GB2135637B; MA20021A1

Abstract

The bridge consists of a plurality of modules each of which comprises a longitudinal box-type girder 3, carrying a carriageway, supported by two or more pontoon units 4. These pontoon units comprise a pair of vertical hollow cylindrical bodies 6 joined below water level by a hollow box girder 7. The modules are individually anchored and support the main bridging girder on rigid legs 5 and are joined by mating components at either end of the bridging girder. A series of such modules is preferably joined in a horizontally undulating manner in order to provide, in the completed structure, a degree of horizontal flexibility so that it is capable of withstanding extremes of weather, waves and currents, and is able to span water channels of great depth. Modules are mated by a relatively unballasted module with a male end piece being lowered by increasing ballasting to join with a female end piece of an adjacent module. <IMAGE>

Description

SPECIFICATION Floating bridge When spanning across a channel, an estuary or any other stretch of the sea by means of a bridge, two problems are frequently encountered: The excessive depth of the bottom.

The action of waves, currents, etc.

When there is a great depth of water, the pillars of the bridge which rest on the sea bed prove to be uneconomic due to their disproportionate length. On the other hand, the piling work for these pillars carried out under a large sheet of water is both difficult and costly.

In order to overcome these problems, floating bridges are occasionally used. Floating bridges have been in use since time immemorial, supported on barges or rafts, in order to span across rivers carrying a large flow of water.

However, this solution becomes too elementary for spanning across stretches of sea subject to adverse environmental conditions since storms would destroy a bridge of this type.

The aim of the present invention is to provide a type of floating bridge for use in spanning across wide stretches of water subjected to the action of storms and with great depths.

The floating bridge covered by the present invention is constructed by adding to a series of modules until the required overall length has been attained. These basic modules consists of an upper box girder, or bridging girder resting on two floating pontoons placed transversally to the said box girder.

The upper bridging girder constitutes the basic structural member of the bridge and furthermore allows the passage of vehicles along the said girder.

Transversal floating pontoons replace the conventional pillars and have the following functions: To provide points of support for the bridging girder.

To provide the necessary buoyancy.

To provide stability to prevent the entire structure from capsizing.

In their turn, floating bridges are fastened to the sea bed by the appropriate anchor lines which prevent the bridge from being swept away in the entirety. These anchor lines allow the pontoons a certain amount of mobility when acted upon by environmental agents while impeding undue horizontal travel.

Owing to the fluctuating nature of the forces exerted by the waves, the wind and the currents, combined with the elasticity of the system of anchor lines, any reactions which the pontoons produce on the bridge girder are of a fluctuating nature, both as regards the vertical components of these forces and the horizontal components.

To enable a bridging girder to absorb the said forces without endangering its structural integrity, this girder has been made sufficiently rigid in the vertical plane, in conjunction with a certain amount of flexibility in the horizontal plane so as to enable the bridging girder to adjust its length and geometry, thus adapting itself to the horizontal mobility of the floating pontoons and any expansion of the materials by heat.

This flexibility in the horizontal plane can be achieved by means of an undulating-shaped layout instead of making it in a straight line.

Returning to the vertical forces, the successive passing of the crests and hollows of the waves produces in the pontoons some fluctuating forces of buoyancy, the variability of which should be absorbed by the rigidity of the bridging girder. So that this latter does not have to be too strong, the fluctuation of the forces of buoyancy should preferably be relatively small, which leads us to give a special configuration to the pontoons, in such a way that the careenage volumes at the height of flotation are relatively slight compared with the total volume. The so-called U-type of pontoon fulfils this condition.

U-type pontoons consist of two cylindrical bodies with a vertical axis mutually joined by means of a box girder located, for preference, beneath the surface of the sea. The said girder is to be facing in a direction perpendicular to the upper bridging girder.

The pontoons are provided with means of ballasting and unballasting, thus making it possible to vary the conditions of buoyancy of the modules. Each module, furthermore, is provided with male and female members located at the ends of the upper longitudinal girders for aligning and linking the adjacent modules.

In building the bridge the following procedure can be adopted: when the first module has been installed, the second and following modules are floated for consecutively linking lengthwise. Each module is situated as a continuation of the previous one already installed and is fastened by means of its anchor lines, thus keeping a smaller draught than that of the said previous module.

Immediately after alignment, the pontoons of the module being installed are progressively ballasted while the male member which is integral with its upper longitudinal girder is lowered for insertion and coupling with the female member of the upper longitudinal girder of the previous module.

In this way the module being installed is made fast thus enabling it to be finally joined up to the previously installed module.

As an aid to understanding the invention, it will be described below in greater detail and with reference to the attached drawings, which contain, by way of a non-limitative example, a possible form of construction.

In the drawings: Figure 1 is an elevation of a bridge built in accordance with the invention.

Figure 2 represents a possible ground plan layout of the bridge in Figure 1.

Figure 3 is a view of one of the modules which comprise the bridge.

Figures 4 and 5 show, in elevation and ground plan, one of the pontoons of the modules.

Figure 6 is a schematic section, in accordance with line VI--VI of Figure 5.

Figures 7 to 12 shows schematically the process of assembling consecutive modules.

The bridge in Figure 1 is made up of modules which include two or more lower pontoons and one upper box girder.

The pontoons provide points of support for the bridging girder which constitutes the basic structural member of the bridge and defines the transit surface. The defines of the bridge may also contain pontoons of a different height in order to provide zones, like that denoted by the numeral 1 in Figure 1, to allow the passage of ships. It is also possible to insert a lifting bridge 2 between two consecutive modules.

The bridge, in its ground plan, Figure 2, may present an undulating outline in order to give a certain amount of flexibility to the structure in the horizontal plane.

The modules which comprise the abridge, as can be seen in Figure 3, are formed by an upper box girder 3 and lower pontoons generally denoted by the numeral 4. The girder 3 and pontoons 4 pass from one to the other in a crosswise direction and are connected by means of supporting legs 5.

The pontoons 4 assume a U-shaped configuration, the side branches of which are formed by cylindrical bodies 6 and whose main central branch is made up of a box girder 7.

The cylindrical bodies 6, as can be better appreciated in Figure 4 may be divided into compartments on the inside, in the same way as the box girder 7.

The modules comprising the bridge are fastened to the bottom by means of anchor lines 8.

The cylindrical bodies 6 are fitted with draining devices for ballasting and unballasting so as to enable the buoyancy conditions of the modules to be varied.

The box girder of each pontoon will for preference be located below the flotation line of the assembled structure.

The upper longitudinal girder 3 of each module is, at its extremities, fitted with male and female members 9 and 10 respectively, for aligning and linking consecutive modules, Figures 7 to 12.

During the construction of the bridge and once a module is placed into position, the following module is floated into place by towing to form a continuation of the first. Immediately afterwards the anchoring cables 8 are cast, the extremities of which may be fitted with anchors. Once these anchors are firmly secured to the sea bed, all the cables are made taut until the stipulated pretension is obtained as well as the correct alignment between modules. The module still in the installation phase and denoted by the numeral 11 in Figure 7, is kept with a shallower draught than the module 1 2 already installed, with which the male member 9 of the module 11 can be located on top of the female member 10 of the module 12.Once a perfect alignment of the modules 11 and 12 has been achieved, the ballast water is introduced into the pontoon of the module 11, whereupon the pontoon descends until such time as the male part or member 9 fits into the female part of member 10. In this way the module 11 is supported on the module 12 as shown in Figures 9 and 10 thus ensuring that both adjacent extremities are firmly fixed in relation to each other. Steps can then be taken to effect the final union of the two extremities by means of welding or some other efficient method, as represented in the Figures 11 and 1 2. This process can be repeated for constructing the bridge in its entirety.

An adequate description of the nature of the invention having been given as well as of the method of carrying this out in practice, it should be stated that the dispositions previously mentioned above allow modifications in detail provided these do not entail any alteration to its basic principie.

Claims

1. Improvements to the design of floating bridges, characterised by the fact that they are formed on the basis of floating modules consisting of an upper longitudinal box girder and at least two lower transversal floating pontoons, the girder of which is supported on the pontoons by means of rigid legs, whereby each of the said pontoons consists of two end floating bodies with a vertical axis, and an intermediate box girder joined at its ends to the cylindrical bodies.

2. Improvements in accordance with Claim 1, characterised by the fact that the modules are consecutively arranged in relation to each other in such a way that they define an undulating layout in the horizontal plane.

3. Improvements in accordance with Claim 1, characterised by the fact that the pontoons assume a U-shaped configuration, the side branches of which are defined by the cylindrical bodies, and the central branch of which consists of the intermediate box girder, the flotation capacity of the said pontoons being such that the afore-mentioned intermediate box girder is located preferentially below the load line of the module.

4. Improvements in accordance with the foregoing claims, characterised by the fact that the pontoons are provided with means for ballasting and unballasting making it possible to vary the buoyancy conditions of the modules as also the male and female alignment and linking members arranged at the extremities of the upper longitudinal girders of the modules, so that as soon as the first module is positioned and anchored, the second can be moved by floating until it is located as an extension of the first, being fastened in position by means of the anchoring lines, whereby the said second module has a shallower draught than the first, so that when the pontoons of the second module are progressively ballasted, its male member integral with its upper longitudinal girder descends and becomes inserted or coupled to the female member of the upper longitudinal girder of the first module, the said second module being thus fixed with respect to the first to enable both to be finally joined together.

5. A floating bridge substantially as herein before described with reference to the accompanying drawings.