GB2143269A - Bridges for traversing waterways - Google Patents

Abstract

A method of constructing a bridge for traversing a waterway includes preparation of an underwater sea-bed site (20) for supporting a pier (12). Pier (12) is constructed in a dry dock and is floated to the sea-bed site (20) after completion of the pier (12). At the sea-bed site (20) the pier is rendered unbuoyant and is deposited on site (20) and anchored thereat by anchorages (24) penetrating base (13) of pier (12). A double cantilevered bridge section (29) undergoes construction at a land-based construction site and on completion is transported by water-borne craft along the waterway (11) to the location of the pier (12) where it is affixed to the pier at the water level and thereafter hoisted to the top of the pier (12) where section (29) is affixed. <IMAGE>

Description

SPECIFICATION Bridges for traversing waterways This invention relates to bridges for traversing waterways and to a method of constructing same.

In conventional construction techniques for bridges over waterways one or more support structures or piers are fabricated at a prepared sea-bed site, the site being temporarily en cased and evacuated of water as far as pos sible to permit construction under dry conditions. On completion of the pier a doublecantilever bridge section is constructed adja cent the top of the pier along the intended line of communication to be served by the bridge, the ends of this double-cantilevered bridge section being connected to correspond ing bridge sections mounted atop adjacent piers or mounted atop land based structures, depending upon the width of the waterway and the span of the double-cantilevered section.

This known arrangement suffers from the disadvantage that construction work is undertaken in the waterway and ensues for long periods of time which inhibits flow of waterborne traffic. Furthermore the technique of encircling the site in the waterway is limited to sea-bed sites of limited depth from the surface of the water.

It is an object of the present invention to provide a method of constructing a bridge for a waterway which obviates or mitigates the foregoing disadvantages.

According to the present invention there is provided a method of constructing a bridge for a waterway comprising the steps of preparing an underwater sea-bed site for support of a pier, constructing a pier in a dry dock, rendering the completed pier buoyant, flooding the dry dock and floating the completed pier to the prepared sea-bed site, rendering the pier unbuoyant and anchoring the pier base to the prepared underwater sea-bed site, constructing a double-cantilevered bridge section at a land-based construction site, transporting the double-cantilevered bridge section from the construction site to the anchored pier by water-borne means, mounting the said section on the pier at the water level of the water-way, hoisting the said section to the top of said pier and securing the section thereat.

It will be appreciated that in accordance with the present invention there is no requirement to surround the sea-bed site with any form of temporary enclosure since at all times the sea-bed site remains under water. Accordingly, the depth limitation on sea-bed sites considered appropriate by the known construction method is no longer applicable. The present invention permits sea-bed sites to be prepared at depths dependent upon under water working techniques which, as is well known, can be many hundreds of meters.

Additionally, the present invention provides for the majority of construction work to be undertaken at locations which are remote from the sea-bed site, namely, in the dry dock and at the construction site and therefore the work undertaken at the sea-bed site is of limited duration. Accordingly closure of the waterway to water borne traffic can be restricted in duration. Alternatively, closure can be avoided by utilising the known technique of initially securing the double-cantilevered bridge section to the pier such that the longitudinal extent of that section lies in the direction of waterway traffic flow, the section thereafter being hoisted to the pier top and then being swivelled through an angle such as 90 as will permit the bridge section extent to lie along the intended line of communication to be served by the bridge.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figs. 1-8 illustrate different aspects of a first embodiment; Fig. 9 illustrates a detail of a second embodiment; and Fig. 10 illustrates part of a completed bridge constructed from the second embodiment.

In the drawings, Figs. 1 and 2 illustrate a dry dock 10 formed adjacent a waterway 11 in which dry dock 10 a pier 12 has been constructed. Pier 1 2 comprises a base portion 1 3 supporting a column 14 the upper end of which has a header 1 5 which may be separately constructed as illustrated. Header 1 5 is fitted to the column 14 preferably in dry dock 10 and may be arranged to swivel on column 14 if so desired. Following completion of pier 1 2 a floatation collar 1 6 is fitted to the pier, dry dock 10 is flooded and pier 1 2 is floated on waterway 11 to the required sea-bed site.

During construction of pier 1 2 in dry dock 10 the sea-bed site 20 undergoes preparation, for example, as illustrated in Fig. 3 by means of a barge mounted device 21. On reaching the prepared sea-bed site 20 as illustrated in Fig. 4 the pier 1 2 is rendered unbuoyant, for example by removal or collapse of the collar 1 6 and by ballasting of the base 1 3 so that the pier 1 2 is mounted on the prepared site 20. Base 1 3 is preferably thereafter anchored to site 20 by underwater affixing of piles 24 penetrating base 1 3 and site 20.

During simultaneous preparation of site 20 and pier 1 2 a double-cantilevered bridge section 29 undergoes construction at a landbased construction site 30 as illustrated in Fig. 5. The completed section 29 is thereafter transported by water-borne craft 31 along waterway 11 to the location of pier 12, see Figs. 6 and 7 where the section 29 is mounted on pier 1 2 whilst section 29 is at the water level of waterway 11. In the example illustrated this mounting is effected by means of cables 32 connected to header 15, the cables being mounted on winching apparatus in header 1 5. By operation of this winching apparatus bridge section 29 is elevated from the water level of waterway 11 to the top of the pier 1 2 where it is affixed.

Fig. 7 illustrates header 1 5 of the swivel type such that connection of section 29 initially to pier 1 2 is effected whilst the longitudinal extent of section 29 is parallel to the flow of traffic on waterway 11. After section 29 has been elevated to the top of pier 12 and has been secured to header 1 5 at that position the entire header 1 5 together with section 29 is swivelled on pier 1 2 so that section 29 extends along the intended line of communication to be served by the bridge, this normally being at approximately 90 to the direction of traffic flow on waterway 11.

This swivel action is undertaken in a manner known per se, for example as described in U..K. Patent Specification No. 2011980 incorporating the use of temporary guys or stays.

By way of example Fig. 8 illustrates an anchoring mechanism 33 between section 29 and pier 1 2 which additionally provides support for section 29 on pier 12. It will be understood that in this arrangement following completion of the swivel motion of header 15, header 1 5 is locked onto the top of pier 1 2 to avoid unwanted swivel activity during normal use of the bridge.

It will be observed that in the embodiment of Figs. 1-8 the pier 1 2 comprises a single column or leg 14 upstanding from base 13.

This is one convenient embodiment of pier 1 2. An alternative embodiment is illustrated in Fig. 9 where pier 1 2 is shown anchored to site 20, this pier 1 2 comprising a four leg tower. In this arrangement section 29 is initially located astride the individual legs of the pier 1 2 and is elevated up the pier 1 2 with lateral support provided on both sites of section 29 by virtue of the individual legs. The completed assembly as shown in Fig. 10 is secured to the top of the pier 1 2 at the ends of the four legs and if required may be swivelled thereat, the elevating means in this case being beneath section 29.

It will be appreciated that the double cantilevered bridge section 29 previously referred to is constructed at construction site 30 in skeletal form and that following completion of the mounting of the section 29 on pier 1 2 and that of any adjoining sections and piers a finished traffic flow surface is provided over the entire length of the bridge. This surface may be a roadway for vehicular traffic and/or railway lines or the like for a rapid transport system. Furthermore where a plurality of piers are provided for supporting individual bridge sections adjoining portions of adjacent sections as shown in Fig. 10 may be interconnected with openable span units 35 for the purpose of enabling passage of waterway traffic with oversized super structure.Span units 36 provided between other adjacent sections 29 provide an in-built facility for articulation relief of the bridge which enables compensatory movement of the bridge in the event of earth structure movements such as may arise from time to time from seismic activity.

It will be appreciated that pier 1 2 may have any number of upstanding columns or legs and that the two embodiments depicting single column and a four-legged pier are merely by way of example. Furthermore bridge section 29 whilst of the double-cantilevered type need not be physically symmetrical and as regards the cable stay arrangement of section 29 any number of cables may be utilised as required in the interests of safety and efficiency of construction. There may be one or more cable stays for each cantilevered portion of bridge section 29.

In the embodiments utilising bridge sections 29 which are hoisted up the pier 1 2 and thereafter swivelled through for example 90 , it will be appreciated that provided the ability to swivel is retained after completion of the entire bridge one or more of the sections can be deliberately arranged to operate as a swing section to permit pivotal movement around the relevant pier 1 2 thereby enabling passage of over-sized super structured shipping.

As regards utilisation of bridges in accordance with the present invention the waterways to be traversed may be sea-water crossings or river crossings. for example, separating such land masses as England and France; Italy and Sicily; and Gibraltar and Algeria.

It will be appreciated that a pier 1 2 may be of predetermined dimension or it may be telescopic and likewise bridge section 29 may be of predetermined length or it may be telescopic in length.

In the modification the bridge may take the form of an airport runway extending from a land-based end and over a waterway and terminating at or adjacent a pier secured to the sea-bed. In this arrangement the or each bridge section may be of a buoyant construction secured to the pier at or about the normal water level of the waterway, the periphery of the runway being protected from ingress of water by means of a Jarlin type wall. It will be understood that a Jarlin type wall is a multiple cell structure each cell having apertured walls whereby the wall functions as a break-water.

In this arrangement the main runway section is supported in part by buoyancy and in part by the or each pier and to enhance buoyancy it is preferred that the main runway portion be of cellular construction each cell having a dense durable reinforced concrete skin covering a lightweight concrete housing internally filled with polystyrene or the like.

Claims (7)

1. A method of constructing a bridge for a waterway comprising the steps of preparing an underwater sea-bed site for support of a pier, constructing a pier in a dry dock, rendering the completed pier buoyant, flooding the dry dock and floating the completed pier to the prepared sea-bed site, rendering the pier unbuoyant and anchoring the pier base to the prepared underwater sea-bed site, constructing a double-cantilevered bridge section at a land-based construction site, transporting the double-cantilevered bridge section from the construction site to the anchored pier by water-borne means, mounting the said section on the pier at the water level of the waterway, hoisting the said section to the top of said pier and securing the section thereat.

2. A method as claimed in claim 1, including providing said pier with a header incorporating winding apparatus for hoisting said bridge-section to the top of said pier.

3. A method as claimed in claim 2, including providing said header with means for swiveling the header relative to the remainder of the pier.

4. A method as claimed in any preceding claim, wherein said pier is provided with at least two columns upstanding from the pier base to provide lateral support for the bridge section which initially is located between said at least two columns.

5. A method as claimed in any preceding claim, wherein said bridge section is provided with a cable-stay arrangement for each cantilevered portion.

6. A method of constructing a bridge for a waterway substantially as hereinbefore described with reference to the accompanying drawings.

7. A bridge when constructed in accordance with the method claimed in any preceding claim.