RAPID DEPLOYMENT FLOATING BRIDGES

Abstract

A rapidly constructed floating bridge for emergency deployment to minimize the time required to restore vehicular traffic where a structure crossing over a waterway has been rendered unusable or unsafe due to natural forces or acts of terrorism. The bridge is modular in nature and may be constructed from parts, including assemblies and/or subassemblies, that can be delivered to a staging area from which the bridge is assembled and deployed. The floating bridge can also be constructed as a temporary detour floating bridge at a location where a permanent structure is being repaired, removed or replaced by a new structure. The bridge is also a low cost option for a new location where a useful life of 25 to 30 years is required. The bridge may be continuous without a span that opens or may include one or more spans that pivot to open and provide a navigation channel, and/or the bridge may include an elevated span at a shore side to provide a navigation channel below the elevated span.

Description

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyrights whatsoever.

BACKGROUND OF THE INVENTION

The invention disclosed herein relates generally to the field of floating bridges. More specifically, the present invention relates to floating bridges for vehicle and/or pedestrian traffic which can be deployed, erected, etc., rapidly. Such floating bridges may be used in emergency situations to replace a collapsed or damaged structure rendered unusable or unsafe due to, e.g., natural forces or acts of terrorism, or in planned situations, e.g., to provide a temporary bridge while an existing bridge is being repaired or a new bridge built, etc. The invention also relates to floating bridges that provide for passage of marine vessels therepast.

SUMMARY OF THE INVENTION

In accordance with some embodiments of the invention, rapid deployment of a floating bridge for carrying traffic (e.g., vehicles of various types, pedestrians, or both, etc.) over water from one shore to another encompasses the use of bridge parts including modules, components, spans and other parts (e.g., used or constituting spans, roadways, connectors, anchorage, shore approaches, etc.) that can be brought to a staging area for a bridge crossing quickly. In some embodiments, the bridge parts are of a size to be transportable by truck to the staging area, although the bridge parts may be transported to the staging area by any suitable and available mode of transportation, including by barge or boat. The size of the bridge parts as delivered to the staging area relates to the available mode of transportation. For example, for delivery at least by truck, the parts are provided unassembled, partially assembled and/or broken down so as to be transportable by truck. On the other hand, if water is an available mode of transportation, bridge parts can be assembled or partially assembled, etc., to a size to be transportable by a barge or boat, etc. However, floating bridges according to some embodiments of the invention are configured so that they may be entirely constructed from bridge parts transportable by truck. The bridge parts are configured to be relatively quickly assembled into the floating bridge so that a bridge may be deployed quickly when needed. The term “parts” is used herein in a broad sense and encompasses discrete parts, items, components, modules, assemblies, subassemblies, etc., as well as materials, e.g., bulk materials, including anything that may be included in a bill of materials, unless the context indicates otherwise.

A rapidly deployable floating bridge according to some embodiments of the invention is a temporary bridge in the sense that it can be assembled relatively quickly. In some embodiments, the bridge is temporary also in the sense that it can be disassembled relatively quickly, with many of the bridge parts being available for reuse. The bridge parts may be stored locally or regionally, but not necessarily earmarked for any particular potential bridge crossing.

A rapidly deployable floating bridge according to some embodiments of the invention is also rapidly openable to define a channel therepast for marine navigation.

The bridge parts may comprise modules and/or components that are assembled into bridge spans either on land or on the water, and can be stored on land. The parts may also comprise parts needed to assemble and/or secure spans of the floating bridge, or parts needed to form shore approaches, traffic carrying structures (e.g., a roadway, walkway), railings, road dividers, lighting and/or facilities used with a bridge, e.g., safety and/or security structures and apparatus, etc.

According to some embodiments of the invention, a local launch and/or assembly and/or staging area or site (for convenience, referred to as “staging area”) is constructed for receiving bridge parts, storing bridge parts, assembling bridge parts and/or staging or launching bridge spans, parts, etc. Such an area or site may include infrastructure such as storage space, assembly space, and shore approaches, etc., and equipment (e.g., cranes, fork lifts, trucks, ramps, boats, etc.) needed to assemble and/or launch bridge parts for the floating bridge.

A relatively rapidly deployable floating bridge according to some embodiments of the invention comprises overlapping sets of bridge parts (spans, units, modules components, etc.). This permits floating bridges to be assembled at different sites to employ many of the same parts, which in turn simplifies manufacture and storage of parts. In addition, using common parts enables bridges to be erected using standardized procedures.

A rapidly deployable floating bridge according to some embodiments of the invention comprises shore approaches (which bring traffic to and take traffic away from the bridge crossing) that are also configured to be quickly constructed from parts that are transportable by truck, e.g., utilizing reinforced earth wall technology or, if the soil requires, utilizing steel sheet piles, or modular load bearing units, etc. “Shore approaches” is used herein in a broad sense and my encompass load-bearing abutments and structures, traffic carrying structures including (roadways for vehicles, walkways for pedestrians and light vehicles such a electric carts, bicycles, etc.) entrance and exit ramps, site preparation, etc.

A rapidly deployable floating bridge according to some embodiments of the invention comprises first and second elevated transition spans and a plurality of floating spans that are connected to at an adjacent floating span and an adjacent elevated transition span or two adjacent floating spans. Together the spans cooperate to carry traffic across the bridge from one shore approach to the other. An “elevated” span comprises a span which is not floating, e.g., has one end connected to a shore approach or another elevated span at an elevation above water level and another end which is connected to a floating span. According to some of the embodiments, at least one of the floating spans comprises a floating transition span that carries traffic between a higher elevation above water level and a lower elevation floating span, e.g., between an adjacent higher elevation elevated transition span and a lower adjacent floating span. All of the spans are constructed of parts transportable by truck.

In some embodiments, a floating bridge span comprises a plurality of buoyant modules, such as pontoons, that are connected together. In one embodiment, the pontoons extend transversely, e.g., perpendicularly, to the portion of the traffic carrying structure supported by the span. Spans fabricated from pontoons provide the advantage that the span will not fail due to a buoyant failure of a pontoon or pontoons. Because the pontoons are connected together, water entering a pontoon will only rise to the water level, i.e., the pontoon will not sink, since the upper portion of the failed pontoon is supported above the water level by the other pontoons. Spans of varying sizes may be fabricated to satisfy local requirements as loading, lengths, widths, etc.

In accordance with some embodiments of the invention, floating bridges provide for passage of marine vessels therepast, e.g., by providing one or more navigation channels past the bridge without opening the bridge, and/or by, moving one or more spans of the bridge to open the bridge to marine navigation. In some embodiments, two spans are connected together so as to be selectively disconnected and separated to create a break in the floating bridge when wanted, e.g., when marine vessels want to navigate past the bridge. When the bridge is configured to carry vehicle and or people, the two spans are connected. When the bridge is to be opened, traffic across the bridge is stopped and the two spans disconnected.

According to an embodiment of the invention, a pivot connection used, e.g., for pivoting a span to provide a marine navigation channel, may comprise a hinge connector with a hinge portion (or hinge leaf or hinge half) connected to each of two adjacent spans to pivotally connect the spans.

An anchorage system is operated to move and maintain the separated parts of the bridge apart to create the navigation channel. The process is reversed to close the bridge and resume traffic across the bridge.

The anchorage system also maintains the floating spans in position and is dynamic to accommodate changing currents, tides, winds and water levels. In some embodiments, sensor are provided to sense currents, wind, water levels, loading, etc., and the anchorage system is automatically adjusted to accommodate changes. Existing conditions such as tides, currents, winds, etc. may be used to assist in pivoting a span open or closed.

In some embodiments, the anchorage system includes modular anchor elements that also are transportable by truck to the staging area. In an embodiment of a modular anchor element, the modular element may include a base unit adapted to be embedded on the water bottom, and one or more stackable units that directly connect to the base unit or through another stackable unit. A cable is connected to the base element and may also be connected to or looped through one or more stackable units. Such anchor elements may be made of concrete. The cables may be connected to winches on the bridge spans to suitably tension and loosen the cables. This embodiment of a modular anchor element is configured to be relatively quickly installed. In some embodiments, anchor elements may comprise a ship anchor, e.g., a fluke-type anchor, or other types of anchor element depending upon water bottom condition, currents, bridge size and loading, etc. In some embodiments, the anchorage system includes anchor elements on either or both shores.

According to some embodiments, a navigation channel is created adjacent a shoreline with one or more elevated spans or bascules (elevated relative to water level and floating spans). In some embodiments, an elevated span is followed by one or more floating transition spans that reduce bridge elevation from the elevated span to a lower span floating on the bridged body of water. According to an embodiment, an elevated span is pivotally connected, e.g., hinged, to an adjacent span and/or a shore approach to pivot vertically about a horizontal axis to accommodate changes in water level and/or loading.

According to some embodiments, a floating transition span comprises a floatation structure, support elements extending upward from the floatation structure tapering in height from an elevated end of the floating transition span to a lower end, and a traffic carrying structure supported by the support elements. In some embodiments, this floating transition span is pivotally connected to an adjacent span and/or a shore approach.

Some embodiments of floating bridges include locking connectors for locking adjacent spans together, e.g., pivotally connected spans. In some embodiments, a connector includes a male centering connector part on one span that is received in a female mating locking connector part on the adjacent span. In some embodiments, the centering part includes an actuatable locking structure, e.g., automatically operated to lock when the connectors are properly docked, and remotely actuated to disengage a locked connector. In some embodiments, a locking connector is locked and unlocked by manual activation. In some embodiments, a hinge connector includes at least one locking connector

According to an embodiment of the invention, a floating bridge for rapid deployment at a water crossing for carrying traffic between a first shore and a second shore, comprises a first shore approach at the first shore and a second shore approach at the second shore, each shore approach comprising a traffic carrying structure. This bridge also includes a first elevated transition span pivotally connected to the first shore approach and a second elevated transition span pivotally connected to the second shore approach, each elevated transition span comprising a traffic carrying structure, and a plurality of floating spans connected together between the first and second elevated transition spans, the floating spans including at least one transition floating that carries traffic between an adjacent higher elevation span and an adjacent lower elevation span. According to this embodiment, the shore approaches and all of the spans are constructed of parts transportable by truck or boat to a staging area from which the bridge is deployed.

As discussed above, the bridge may be constructed to open provide for navigation or not open. In an openable embodiment, at least one of the floating spans is pivotally connected to an adjacent span at one and releasably connected to an adjacent span at an opposite end so as to be pivotable horizontally on the water between a closed traffic carrying condition and an open condition in which an opening in the bridge is created for marine navigation.

To accommodate changes in water level, loading, weather, etc., an elevated span may be pivotally connected to a floating span.

To provide a navigation channel without opening the bridge, at least one of the elevated transition spans may be provided that is elevated a sufficient distance above water level at least for a portion thereof to form a navigation channel.

According to an embodiment of the invention, a hinge connector may be provided for attachment to two floating spans to allow horizontally pivoting therebetween. A hinge connector may comprise two leaves pivotally connected by a pin, each leaf of the connector being connected to adjacent pivotally connected spans, and a locking connector which comprises a mating locking part associated with each leaf.

An anchoring system may be provided for the bridge that anchors at least one floating span to the water bottom. In one embodiment, the anchoring system is attached to the at least one floating span and comprises a plurality of modular anchor elements which each comprise a base module situated on or in the water bottom on opposites sides of the at least one floating span, at least one stackable element attached to the base element, at least one cable attached to each anchor element and the at least floating span and a winch associated with the at least one floating span connected to each cable.

According to some embodiments of the invention, one or more of the floating spans comprises an assembly of a plurality of pontoons connected together transversely of traffic carried by the respective span. Various numbers and configurations of pontoons may be used. Exterior pontoons in an assembly include an end that is sloped to reduce drag and friction. In an embodiment, a pontoon assembly comprises pairs of pontoons arranged end to end with the sloped ends facing out. In one embodiment, two pontoons are configured to create a space therebetween which may function as a drain. In one embodiment, a pontoon may include a winch of the anchor system. In an embodiment of a pontoon assembly, four pontoons are arranged end to end. In this embodiment, two interior pontoons do not have sloped ends.

An embodiment of a floating transition span comprises a floating structure and supports extending upwardly from the floating structure to and supporting a traffic carrying structure, the supports comprising supports of different height arranged to provide a grade to the traffic carrying structure from the higher elevation span to the lower elevation span. The height of the supports may be adjustable.

According to some embodiments, a staging area is provided from which a floating bridge can be rapidly deployed. The staging area comprises a site near a water crossing which the floating bridge is to bridge, at least one storage area on the site for receiving pontoons transported by truck or boat, at least one assembly area on the site for assembling the floating spans on water from pontoon, and a launching area for at least one of the assembly sites.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the figures of the accompanying drawings, which are meant to be exemplary and not limiting, and in which like references are intended to refer to like or corresponding parts.

FIG. 1 is a schematic perspective view depicting a non-opening floating bridge in a fully deployed position according to an embodiment of the invention.

FIG. 2 is a schematic perspective of a floating bridge according to another embodiment of the invention, which is similar to the floating bridge depicted in FIG. 1 but includes two center pivoting floating spans which pivot to open the bridge.

FIG. 3 is a perspective schematic view of a portion of the bridges depicted in FIGS. 1 and 2 showing a shore approach, an elevated transition span, and a floating transition span.

FIG. 4 is a side schematic view of the bridge parts depicted in FIG. 3.

FIGS. 5-6 are schematic perspective and elevation views of a shore abutment of the bridges depicted in FIGS. 1 and 2.

FIGS. 7 and 8 are top and bottom schematic perspective views, respectively, of an assembly of pontoons according to an embodiment of the invention.

FIGS. 9A and 9B are perspective schematic views of mating sections of a pontoon according to an embodiment of the invention which includes a winch.

FIGS. 10A and 10B are perspective and elevational schematic views, respectively, of two pontoons according to another embodiment of the invention configured and arranged to form a space therebetween used for drainage.

FIG. 11 is a perspective schematic view of a pontoon according to another embodiment of the invention.

FIG. 12 is a side elevation view of a pontoon assembly including the pontoon depicted in FIG. 11.

FIG. 13 is a schematic perspective view of a portion of the bridges depicted in FIGS. 1 and 2 illustrating a part of an anchorage system for the bridge comprising the modular anchor elements depicted in FIGS. 14-18.

FIG. 14 is a perspective schematic view of an assembled modular anchor according to an embodiment of the invention.

FIGS. 15 and 16 are side elevation schematic views of the modular anchor depicted tin FIG. 14.

FIG. 17 is a top plan schematic view of a stackable module of the modular anchor depicted in FIG. 14.

FIG. 18 is a bottom plan schematic view of a base module of the modular anchor depicted in FIG. 14.

FIG. 19 is a perspective schematic view from one side of a hinge connector according an embodiment of the invention used to pivotally connect a floating center span to another span.

FIG. 20 is a perspective schematic view of the hinge connector depicted in FIG. 19 from the opposite side.

FIG. 21 is a perspective schematic view of the hinge pin portion of the hinge connector depicted in FIG. 19.

FIG. 22 is a side perspective schematic view of a locking connector according to an embodiment of the invention.

FIG. 23 is side elevation schematic view of the locking connector depicted in FIG. 22.

FIG. 24 is top plan schematic view of the locking connector depicted in FIG. 22.

FIG. 25 is a front elevation perspective schematic view of the locking connector depicted in FIG. 22.

FIG. 26 is an exploded perspective schematic view of a locking connector according to another embodiment of the invention.

FIG. 27 is a front elevational schematic view of the locking connector depicted in FIG. 26.

FIG. 28 is an side elevational schematic view of a female part of the locking connector depicted in FIG. 26.

FIG. 29 is an end elevational schematic view of a male part of the locking connector depicted in FIG. 26.

FIGS. 30-33 depict a series of movements of the locking connector depicted in FIG. 26 as the locking parts mate from an unlocked position to a locked position.

FIG. 34 is a perspective view of a bridge site for and staging area from which the bridges depicted in FIGS. 1 and 2 may be assembled and deployed.

DETAILED DESCRIPTION

Floating bridges according to embodiments of the invention may be configured for vehicular traffic, pedestrian traffic, or both, and in some embodiments, a floating bridge may be configured primarily for vehicle traffic, or primarily for pedestrian traffic, or for heavy or light vehicle and/or pedestrian traffic, etc. Floating bridges according to embodiments of the invention may include a single or a plurality of traffic lanes, e.g., for vehicular traffic and pedestrian traffic. Floating bridges according to embodiments of the invention may be configured for long or short term use, and may be permanent, e.g., have projected life span of many years, or temporary in nature, e.g., be used until another bridge is built or repaired, and one or more principles and/or embodiments of the invention are applicable to long term or permanent bridges, as well as to short term or temporary bridges. Parts of the bridge may modular and be of a size to be transportable to a staging and/or deployment area.

Floating bridges according to embodiments of the invention may include different numbers, types and positioning of floating bridge parts. Selection of various bridge parts may depend upon whether the floating bridge is for long or short term use, vehicle or pedestrian traffic, emergency evacuation, replacement of a damaged or collapsed bridge, temporary detour, etc., and takes into consideration the particular bridge site. Some floating bridges according to embodiments of the invention include bridge parts that provide for a marine vessel navigation opening or channel.

According to embodiments of the invention, bridge parts may be selected and stowed locally for a particular site or adjacent the site, or stored for use in a plurality of bridge sites, either identified or yet to be identified, and stored locally or regionally, or by type of floating bridge, etc. Bridge parts may be modular so as to be usable at more than one site and/or to facilitate storage, stowage and/or erection of a bridge. Some modular bridge parts themselves may be fabricated from modular components, e.g., pontoons.

While some embodiments of floating bridges and floating bridge parts are illustrated and/or discussed herein, it should be understood, however, that it is not intended to limit the invention to the illustrated and/or discussed embodiments and variations of bridges, bridge parts, etc.

Floating bridge 100 according to an embodiment of the invention includes a traffic carrying structure comprising a roadway 102, which is divided into three parts, 104a-c (FIGS. 7 & 13). In one embodiment, all three parts may be for vehicle traffic. In another embodiment, two parts, e.g., 104a and 104c, may be for vehicle traffic and part 104b may be for pedestrian traffic. However, the floating bridge 100 may be configured for various types of traffic depending on the particular application. Roadway dividers 136 (FIGS. 7 & 13) extend along the bridge and divide the roadway into the three parts. Parts 104a and c are each configured for two undivided lanes of vehicle traffic (in different or the same directions) separated by the central part 104b configured for service vehicles and/or pedestrians.

A roadway 102 may comprise a surface or combination of surfaces to accommodate different types of traffic on the floating bridge 100. The roadway surfaces may comprise wearing surfaces such as a thin overlay system consisting of an epoxy with aggregate broadcast onto the surface. In one embodiment, the roadway 102 is orthotropic.

FIG. 1 depicts a floating bridge 100 in a fully deployed position at a crossing between one shore 106 to the other shore 108. The roadway 102, only a portion of which is shown in FIG. 1, runs from one shore 106 to the other shore 108. FIG. 1 depicts as anchorage system 114 which includes anchor elements 115 visible in FIG. 1 but actually submerged. As depicted, floating bridge 100 includes shore approaches referenced generally by 120, which each comprise a shore abutment 122 (two shore abutments 122a and 122b are depicted) and shore ramps 124 (two shore ramps 124a and 124b are depicted). The floating bridge 100 also includes floating center spans 130 (four floating spans 130a-d are depicted as indicated by the dotted lines), elevated transition floating spans 140 (two elevated transition floating spans 140a and 140b are depicted) and floating transition spans 150 (two floating transition spans 150a and 150b are depicted) which are connected between a shore abutment 122 and a floating center span 130. According to one embodiment, floating transition span 150a may be provided with a graded roadway, i.e., sloped downwardly from an elevated side to a water level side supported on a buoyant structure 160 (for example, see FIGS. 3-4). Floating bridge 100 may also include lane dividers, lighting, railings and other structure and items normally associated with roadways.

A floating transition span 150b may be configured as a floating dock connected to piles 256 to permit the floating transitional span to move with water level. The elevated transitional span 140b is pivotally connected to the floating transitional span 140b for vertical pivoting with water level fluctuations.

Bridge 100 depicted in FIG. 1 is not configured to be opened for navigation. An embodiment of a floating bridge 100a which can be opened to provide a navigation channel is depicted in FIG. 2. The construction of bridges 100 and 100a is the same in most respects. However, the floating center spans 130a and 130b of bridge 10a are releasably connected together and pivotally connected to an adjacent floating span 130c and 130d, respectively. Bridge 100a as depicted in FIG. 2 shows the roadway 102 from shore 106 to shore 108, while in FIG. 1, the roadway 102 is shown to reveal pontoons represented by the transverse lines from which the floating spans are constructed.

An elevated transition span 140 need not be buoyant, and transitions from the shore to a floating span which may be a floating center span 130 or a transition floating span 150. An elevated transition span may be considered elevated with respect to water level, and may or may not permit marine navigation therebelow. In some embodiments, sufficient height above water is provided below an elevated transition span, and the elevated transition span has sufficient length, to permit marine navigation below the span where the water depth is suitable to accommodate such navigation, e.g., smaller craft. For example, an elevated transition span 140 which provides for marine navigation may be about 250 feet long, or longer, if navigation for larger craft is wanted, or smaller if navigation only for smaller boat traffic is wanted. A navigation channel may be provided for security reasons to allow security boats to quickly navigate past the bridge 100, and where the bridge is openable, without opening it. The transition spans 140 and 150 accommodate water level changes, e.g., due to tides, weather, etc., or loading, which may result in vertical movement of a floating transition span 150 at each shore. According to an embodiment, this movement is accommodated by pivotally connecting the elevated transition spans to a shore approach and/or a floating span. In some embodiments, a floating transition span 150 is not provided, and an elevated transition span 140 connects a shore approach with a floating center span 130. In that case, the elevated transition span 140 may be pivotally connected to a floating center span 130.

An elevated transition span 140 supports the roadway 102 between a shore abutment 122 and a floating transition span 150 while accommodating vertical movements of parts of the floating bridge, as discussed, and can provide longitudinal restraint to maintain the roadway straight at the water end of the elevated transition span. An elevated transition span 140 which provides a navigation channel may only be provided on one or both sides of the water crossing. The construction of an elevated transition span 140 can vary depending on the requirements at the particular crossing, and can be constructed from various materials. In one embodiment, the transition span may be a steel truss assembled from prefabricated steel components. As with other components and/or modules of the floating bridge 100, an elevated transition span 140 may be pre-constructed and stored for delivering to a staging area, or stored at a deployment site near a projected bridge crossing.

Navigation lights may be installed at the bottom of elevated transition span 140 in the center of the navigation channel. Roadway expansion joints may be located at each end of a transition span 140. Electrical power and control wiring for the floating bridge may be installed on a transition span 140.

Floating bridges 100 and 100a are of modular design. For example, floating bridges 100 and 100a may include different numbers and configurations of floating center spans 130, floating transition span(s) 150, elevated transition span(s) 140 and/or shore ramp(s) 124. Thus, these parts may be of modular design and usable at different sites.

Referring to FIGS. 3 and 4, according to an embodiment of the invention, the transition span 150a comprises the floating support structure 160 and supports or columns 164 for supporting a graded roadway 104, which descends at a constant grade to the level of the roadway 102 on the adjacent floating center span 130d, where a vertical curve (not shown) may be provided to transition from the sloped roadway supported by the floating transition span 150a to the horizontal roadway supported by the adjacent floating center span 130d. The columns 160 may be include telescoping portions and a collar 166 so as to be adjustable in height so as to accommodate elevated transitional spans 140a at different elevations and roadways of different grade. (Typically, grades should not exceed about 5%.) The columns may be made of steel and/or reinforced concrete, and may be attached to a base structure supported by the buoyant structure 160. Steel crossbeams and girders (not shown) can be provided to support roadway 102. At crossings where the navigation opening requires a greater vertical clearance, columns near the land side of the floating transition span 150 can be provided with extensions to provide a vertical clearance for a navigation channel. In the embodiment depicted in FIG. 1, all spans are connected and not intended to be opened during use. Locking connectors 280 or 290 (FIGS. 22-29) are used to lock adjacent floating spans together as described below.

In bridge 100a (FIG. 2), the center pivoting spans 130a and 130b are used to open the center section of the floating bridge, as depicted in FIG. 2, are pivoted open to provide a navigation channel marked by pairs of buoys 170 on each side of the bridge. A hinge connector (FIGS. 19-21) used to pivot the spans open, as shown, and closed, and locking connectors 280 or 290 (FIGS. 22-29) are used to lock the pivoting spans closed. The floating center spans 130 may be moved by cables 202 of an anchorage system 114 connected to the floating spans and to anchor modules 115 (visible in FIGS. 1, 2 and 13, but actually submerged). The anchorage system may include winches 206 (FIG. 9B) on board the floating spans However, the floating center spans 130a & b may be pivoted and moved in any suitable manner.

FIGS. 3 and 4 depict an embodiment of a shore abutment 122a, an elevated transition span 140a, and a floating transition span 150a. Shore abutment 122a connects the shore to transition span 140a to allow for vehicular (and/or pedestrian) traffic to enter the floating bridge. A shore abutment 122 comprises a load bearing portion and a wear surface such as a layer of concrete, black top, etc. The load bearing portion may be constituted at least partially by concrete. However, a shore abutment does not require conventional reinforced concrete construction. Shore abutments according to embodiments of the invention may be rapidly constructed by utilizing reinforced earth wall technology or, if the soil requires, utilizing steel sheet piles. Prefabricated concrete slabs may also be utilized. These systems may employ a footing and short stem wall to support an elevated transition span connected to the shore abutment 122. Technology for constructing such shore abutments is known in the art.

The shore abutments 122, which are depicted schematically in FIGS. 5 and 6, may be designed to be rapidly constructed by utilizing, for example, reinforced earth wall technology or, if required by soil conditions, steel sheet piles, modular load bearing units, e.g., of prefabricated concrete or steel. Support elements for transition span 140a may be made of precast concrete. As with other parts of the floating bridge, the shore abutment parts may be stored and delivered to the crossing site. The schematic views of FIGS. 5 and 6 depict two depth levels of the water bottom at 127a & b. The reinforce earth wall construction is referenced by 128. The roadway is represented by 102. The support elements for the elevated span referred to above are supported by a ledge referenced by 129.

Referring to FIG. 1, the floating spans are constructed of pontoons, referenced generally by 130, connected together. The pontoons may have an approximate size of 10 feet in width, 46 feet in length and 7 feet in height, which makes such pontoons transportable by truck. Pontoons may be of other sizes depending upon application. For example, in an application for a pedestrian bridge, a pontoon may be shorter than 46 feet in length. Also, for a single lane of vehicle traffic, a pontoon may be less than 46 feet in length. A pontoon of 46 feet in length can accommodate two lanes of vehicle traffic. Assembled sections of pontoons 230 may be transported by modes of transportation other than trucking, e.g., by barge. Although not shown in FIG. 1, two pontoons 230 are connected end to end to define the width of the bridge 100. Pontoons 230 connected end to end are depicted in FIGS. 7-8, and 10A & B.

Three types of pontoons are used to fabricate floating spans of the bridges 100 and 100a. Pontoons 230 comprise first end, a second end, opposed sides, a top and a bottom, which are connected together to form a hollow, water-tight structure. The top and bottom are parallel to each other, the sides are parallel to each other and extend normal to the top and bottom, and each of the opposed sides is substantially longer than each of the ends, whereby the pontoon is elongated. At least a portion of the first end is sloped inwardly relative to the top to reduce drag or friction of the pontoon on the water, and these ends face outwardly in pontoon assemblies as shown in FIGS. 7-8. The second end extends normal to the top and bottom.

Pontoon 230a, depicted in FIGS. 10A & B, is shorter than pontoon 230, and when connected in an assembly with pontoons 230 (FIGS. 7-8) creates an internal space 232 for drainage.

The width of the buoyant structure 160 of the floating transitional span 150a is defined by four pontoons 230, 230b (FIGS. 10A & B) connected end to end as shown in FIGS. 11-12, e.g., by bolts or other fasteners or other suitable means. Pontoons 230b do not include a sloped end to facilitate assembly and because the ends of pontoon 230b are not exposed to create friction or drag. Therefore, each transverse strip of the buoyant structure 160 represents two pontoons 230 at the exteriors of the strip and two pontoons 230b in the interior of the strip, as depicted in FIG. 12.

FIGS. 9A & 9B depict an embodiment of individual sections 136 of some of pontoons 230. Some of pontoons 230, and pontoons 230a and 10b may have similar constructions, but may not include a winch 2006. Pontoons 230, 230a and 230b include compartments 208 formed by internal baffles or stiffeners 210. The pontoons including tubes 212 for post tensioning cables 214 (FIG. 7), which may be used to attach and tighten pontoons together. The post tensioning cables 214 which extend to the exterior of the pontoon assembly 216 may be tightened by conventional cable connector devices. Post tensioning of assemblies of pontoons may be done in various ways depending upon size, assembly location, etc. Pontoons 230 with winches include a cable pathway 218 through which the cable 202 connected to an anchor (e.g., anchor element 115) and to the winch 206. The cable pathway 218 comprises a watertight tube comprising a first end near the bottom of the pontoon and a second end near the top of the pontoon adjacent the winch 206. The tube has a first opening communicating with the exterior of the pontoon and a second opening communicating with the compartment 208 that houses the winch 206. The tube is watertight between the openings.

The winch 206 may be used to automatically maintain the proper anchor cable tension so as to maintain the floating spans in position with varying tidal, current and weather conditions, and for moving a center pivoting span or other component of the floating bridge. Horizontal and vertical rollers (not shown) may be provide near the drum of the winch to provide proper spooling of the anchor cable. In an alternative embodiment, the winch 206 may be provide as a separate watertight cell (except for a cable opening) which is attached to a pontoon 230 modified, e.g., in length, to accept the cell.

Pontoons 230 may include a hatch (not shown) to provide access to the interior of the pontoon.

Pontoons 230, 230a and 230b include a deck plate 238 bolted thereto which forms part of the traffic carrying structure. An orthotropic roadway is formed by covering the plates with a desired road surface.

Floating spans and buoyant structures comprise assemblies of pontoons 230, 230a and 230b. For example, FIGS. 10A & B depict two pontoons 230a arranged to define a drainage space 136 therebetween for draining water and vehicle fluids from the floating bridge. Pontoons 230a assembled into a pontoon assembly are depicted in FIGS. 7-8. FIG. 11 depicts an assembly of pontoons 230 and 230b, as discussed above. Pontoons 230, 230a and 230b are assembled in various configurations to form floating spans or buoyant structures. For example, the floating center spans 130 may be 130 feet wide by 400 or 800 feet long. Thus, a floating span 130 may include 80 or 160 pontoons of 130, 130a each being 10 feet in width, 46 feet in length. The buoyant structure 160 includes pontoons 230, 230a and 230b, arranged four to a strip, as shown in FIG. 12. Thus, a buoyant structure 400 feet long may include 160 pontoons.

Pontoons 230, 230a, 230b may be combined into an assembly on land and launched into the water or may be assembled together in the water.

Bridges 100 and 100a comprise an anchorage system 114 as depicted in FIG. 13. The particular configuration depends upon bridge length, water currents, wind, traffic, etc. According to one embodiment the anchoring system 114 comprises a plurality of modular anchors, described in more detail below with respect to FIGS. 14-18, connected to a respective floating span (to a winch 206) and engaged with the water bottom. For example, in the embodiment described above where a floating span can be about 400 feet long, two anchor elements 202 may be provided at each one quarter point of such a floating span. As mentioned, the winch maintains the proper anchor cable tension and in some embodiments (e.g., see FIG. 2) moves a floating span to pivot and provide a navigation channel.

Referring to FIGS. 14-18 anchor element 115 comprises a base module 115a and at least one stackable module 115b stacked on the base module 115b or another stackable module 115b. The base and stackable modules in one embodiment are made of concrete, but may be made of any suitable material. The base module 115a comprises a weldment 116 embedded in the concrete for attaching anchor cables 152. Steel eye bars 117 may be used to provide an anchor cable connection that is above the mud line in conditions where the anchor connection to weldment 116 would normally be located below the mud line. The bottom surface of the base module 115a may be equipped with shear webs 118 to resist sliding on bottom soil. The top of the stackable modules 115b may include a circular depression 119 for centering the stackable modules. Stackable module 115b may include a circular protrusion (not shown) on the bottom surface which keys into a circular recess (not shown) on the top of the base module 115a. Stackable modules 115b may be installed on a base module 115a to a height dependent on environmental and site conditions, intended use, load, and other factors. Anchors elements 115 may include lifting eyes (not shown) embedded around the perimeter for use in installation and later removal. In alternative embodiments, ship anchor types such as plate and fluke may be used depending on environmental and site conditions, particularly the condition of the soil/sea bottom, etc.

Referring to FIG. 2, as discussed above, floating spans 130a and 130b may be connected to pivot between open and closed position, and are connected to adjacent spans by hinge connectors 260 shown in FIGS. 19-21. Hinge connector 260 comprises locking connectors 280 (FIGS. 22-33) which lock adjacent spans together. The locking connectors 280 comprise mating connector parts 280a and 280b and are described in more detail below.

Referring to FIGS. 19-21, the hinge connector 260 comprises hinge leaves or halves 262a and 262b, which each includes a reinforced section 264, and a hinge pin 266 which passes through hinge holes in the reinforced structure. A hinge half may be connected to an end of a span by any suitable means, e.g., welding, fasteners, etc. The hinge halves 260a and 260b extend for the width of the span and attach to respective facing ends of adjacent spans. A roadway 102 on a span extends over the hinge leaf half to the span. Two spaced locking connector parts 280a or 280b are attached to each hinge half 262a and 262b.

The embodiment of the lock connector 280 depicted in FIGS. 22-25 comprises a male connector part 280a on one span which is received a mating female locking connector part 280b on an adjacent span. In an embodiment, male locking connector part 280a comprises a hook 282 (FIG. 23) which hooks into and out of engagement with structure in the female connector part 280b. The male connector part 280a is pyramid in shape which guides the male connector part into alignment when it enters the female connector part during docking. A movable lever 284 is connected to the female connector part 280b via a linkage 286. Moving the lever 284 causes the linkage 286 to move the female connector part to engage or disengage structure in the female connector part with the hook 282 on the end of the male connector part.

The embodiment of the lock connector 290 depicted in FIGS. 26-29 comprises a male connector part 290a on one span which is received in a mating female locking connector part 290b on an adjacent span. Male connector part 290a comprises a locking jaw mechanism 292 comprising jaws 295 pivotally connected via a linkage system 294 to actuating rod 296. The male connector part 290a is some what pyramidal in outline shape to assist in guiding the male connector part when it enters the female connector part during docking.

Referring to FIGS. 26-29, docking, during docking, when male connector part 290a is received in mating female connector part 290b, actuating rod 296 is caused to pivot the jaws 292 to engage opening 298 in the female connector part 290b to lock the male and female connector parts together. In one embodiment, the actuating rod 296 is moved by a motor (not shown) which can be controlled remotely.

A locking sequence is illustrated in FIGS. 30-33. FIG. 30 shows the connector parts separated and the jaws in a retracted position. FIG. 31 shows the male connector part 290a entering the female connector part 290b with the jaws 292 still retracted. The entrance 299 (FIG. 28) to the opening 298 in the female connector part 290b is sloped to guide the jaws 292 into the opening 298. In FIG. 32, the jaws 292 have moved into the opening and are still retracted. In FIG. 33, the rod 296 has been activated and the jaws opened to engage the opening 298 engaging structure

FIG. 34 schematically illustrates the bridge site on shore 106. The bridge site in this embodiment operates as a staging area for receiving bridge parts, assembling spans launching spans, etc. As described above, the floating bridge comprises prefabricated span modules and/or components that can be rapidly constructed and rapidly deployed. The method used to assemble the floating bridge may be based on various site and environmental conditions or other factors, e.g., time, expense, or manpower.

The staging area includes an assembly area 310 in close to the shore in relatively shallow water. The assembly area 310 includes a channel 312, which functions similar to a dry-dock, cut into the bottom adjacent the shore line to provide a suitable water depth for floating partially or fully assembled spans. For example, the floating transitional span 150a is shown being assembled in this area. Assembly includes positioning of pontoons by a cranes 314 where they can be attached to form a pontoon assembly for the buoyant structure 160. The cranes then assembles the base structure on pontoon assembly followed by attached the columns. The roadway 102 is then attached to the columns. Upon completion of the assembly of floating transitional span 150a, it can be floated into position for assembly into the bridge.

Different assembly operations may take place at the same time in different areas of the staging area depicted in FIG. 34. For example, assembly of parts of pontoon assemblies 316 may be taking place on land in area 317 to be completed in channel 312.

Cranes 318 may be provided to unload bridge parts trucked to the staging area or delivered by barge at the channel 312. Also, a helicopter pad (not shown) may be provided for helicopters to land and deliver parts, or helicopters could lower parts into any desired area. Parts in partial assembly may be stored in areas such as 320, where assembly may continue or from which parts may be moved to channel 312 for further assembly. Area 320 also stores a part of a elevated transition span 140 and pontoons. Area 320 is accessible by the cranes to either continue assembly there or move parts to other areas for further assembly or launch.

The site depicted in FIG. 34 includes a constructed shore abutment 122a which awaits a roadway section 102 which is stored in area 320. As mention, floating transition span 150a is being assembled. Also, an assembled floating center span 130c is being towed by a tugboat toward shore 108 (not shown).

In an embodiment, the prefabricated span modules and/or components may all be stored at one central location, may be stored at a location near the planned crossing, or may be trucked to the planned crossing location. Security and periodic maintenance may be required while the prefabricated span modules and/or components are in storage.

In an embodiment, the various components of the floating bridge are initially transported to the deployment site, either by truck, boat, or other transportation method. Shore abutments 122 are first constructed along with a roadway system on shore to connect to the shore abutments 122. The shore abutments 122 may be designed to be rapidly constructed by utilizing, for example, reinforced earth wall technology, etc., as discussed above.

Floating spans are connected and secured with the anchorage system. Anchor modules, not shown in FIG. 34, may be stored in the staging area, loaded on a barge, and then installed in the proper locations. Cable connections may be made by divers. The anchor cables may then be tensioned to align the floating bridge.

During installation, the floating bridge is trimmed to the proper freeboard, i.e. the distance from the waterline to the upper deck level of the floating bridge, through the use of gravel ballast installed inside the floating spans.

In an embodiment, once the various components of the bridge are connected, electrical wiring is installed to accommodate deck lighting or other electrical components, and provisions for attaching traffic barriers to the deck are installed.

Roadway cover plates are installed at the center of the floating bridge to accommodate any longitudinal movement resulting from environmental loads or water level changes, and may be configured to move, as required, when the center pivoting span 118 is rotated. Further, the roadway cover plates may be positioned to have a positive hold down effect to minimize the noise created by vehicular traffic driving on the cover plates.

Traffic control gates for the roadways and a control building may be installed on shore. The operation and sequencing of the traffic control gates, navigation channel lights, center pivoting span, center locks, centering pyramids, and other components may all be controlled from the control building or other remote location. Remote cameras and display screens may be used to monitor various operations of the floating bridge or, more specifically, the center pivoting span opening and closing. Bumper guards may be installed on the interior or exterior of the floating bridge to protect against pedestrian, vehicle, service cart, or marine vessel traffic.

The components of the floating bridge may be disassembled in the reverse order for storage or transportation to a different deployment site.

A transition span 150a may be transported by barge into position and is lowered into the water by pumping water into the barges. which transported the transition span into place in embodiments where the transition span is not permanently installed. The shore abutments 122 are connected to the transition spans 112 which are then connected to the abutting floating spans 110, with each connection method comprising either a bolt or hinge system, as appropriate.

In an embodiment with a center pivoting span 118, a segment of floating spans 110 is equipped with the components of the center pivoting span 118 described above. The center pivoting span 118 is moved into position and connected to connection anchor cables 152 and tensioned, and the hinge connection is completed. The center lock mechanism 128 on the upstream side of the floating bridge at the hinge is tensioned to keep the center pivoting span 118 from opening during assembly. In an embodiment, one of the floating spans 110 abutting the center pivoting span 118 may be kept in an open position while the hinge is tensioned.

Claims

1. A floating bridge for rapid deployment at a water crossing for carrying traffic between a first shore and a second shore, the bridge comprising: a first shore approach at the first shore and a second shore approach at the second shore, each shore approach comprising a traffic carrying structure;a first elevated transition span pivotally connected to the first shore approach and a second elevated transition span pivotally connected to the second shore approach, each elevated transition span comprising a traffic carrying structure; anda plurality of floating spans connected together between the first and second elevated transition spans, the floating spans including at least one transition floating span that carries traffic between an adjacent higher elevation span and an adjacent lower elevation span;the shore approaches and all of the spans being constructed of parts transportable by truck or boat.

2. The floating bridge of claim 1, wherein at least one of the floating spans is pivotally connected to an adjacent span at one and releasably connected to an adjacent span at an opposite end so as to be pivotable horizontally on the water between a closed traffic carrying condition and an open condition in which an opening in the bridge is created for marine navigation.

3. The floating bridge of claim 1, wherein the plurality of floating spans comprises two adjacent floating spans which are releasably connected together at adjacent ends thereof and each pivotally connected to an adjacent span at an opposed end thereof so that each is pivotable on the water between a closed traffic carrying condition and an open condition in which an opening in the bridge between the pivoted spans is created for marine navigation.

4. The floating bridge of claim 1, wherein the at least one floating transition span is pivotally connected to an elevated transition span at one end to permit relative pivoting of the floating transition span and the elevated transition span about a horizontal axis, and connected at an opposite end to a floating span.

5. The floating bridge of claim 1, wherein the at least one shore approach comprises a load-bearing abutment.

6. The floating bridge of claim 1, wherein the load-bearing abutment comprises one or more of reinforced earth wall construction, piles and modular precast or pre-constructed load bearing units

7. The floating bridge of claim 1, wherein at least one of the elevated transition spans is elevated a sufficient distance above water level at least for a portion thereof to form a channel for marine navigation therebelow.

8. The floating bridge of claim 2, comprising a hinge connector attached to the pivotally connected floating spans which pivotally connects the pivotally connected floating spans.

9. The floating bridge of claim 8, wherein each hinge connector comprises two leaves pivotally connected by a pin, each leaf of a connector being connected to adjacent pivotally connected spans, and a locking connector which comprises a mating locking part associated with each leaf.

10. The floating bridge of claim 9, wherein one locking connector part comprises jaws and a linkage connected to the jaws for pivoting between a locking position and an unlocking position, and wherein the other locking connector part comprises an opening to receive the linked jaws therein, the opening including at least one edge and the linked jaws engaging the edge in response to activation of the linkage.

11. The floating bridge of claim 10, comprising a rod connected to the linkage to activate the linkage.

12. The floating bridge of claim 9, wherein one locking connector part comprises a projection including a hook and the other locking connector part comprises an opening to receive the projection and a locking pin connected to be movable between positions engaging and not engaging the hook when the projection is received in the opening.

13. The floating bridge of claim 12, wherein the locking pin is connected to be moved manually.

14. The floating bridge of claim 12, wherein the projection comprises a pyramidal shape.

15. The floating bridge of claim 1, comprising an anchoring system which anchors at least one floating span to the water bottom when the anchoring system is attached to the at least one floating span, the anchoring system comprising a plurality of modular anchor elements which each comprise a base module situated on or in the water bottom on opposites sides of the at least one floating span, at least one stackable element attached to the base element, at least one cable attached to each anchor element and the at least floating span and a winch associated with the at least one floating span connected to each cable.

16. The floating bridge of claim 1, wherein each of the floating spans comprises a plurality of pontoons connected together transversely of traffic carried by the respective span.

17. The floating bridge of claim 1, wherein the at least one floating transition span comprises a floating structure and supports extending upwardly from the floating structure to and supporting a traffic carrying structure, the supports comprising supports of different height arranged to provide a grade to the traffic carrying structure from the higher elevation span to the lower elevation span.

18. The floating bridge of claim 1, wherein the at least one floating transition span is connected to the first elevated transition span, and comprising a floating transition span and a plurality of pilings in the water, the floating transition span being pivotally connected to the second elevated transition span to permit relative pivoting therebetween about a horizontal axis, and to the pilings positioned adjacent the floating transition span so as to permit vertical movement of the floating transition span relative to the pilings in accordance with changes in water level at the second shore.

19. The floating bridge of claim 1, wherein the bridge is configured for pedestrian traffic, vehicle traffic, or both.

20. A plurality of connected floating bridge spans comprising: a first floating bridge span;a second floating bridge span;a hinge connector comprising a first hinge leaf connected to the first floating bridge span and a second hinge leaf connected to the second floating bridge span at a location adjacent the location at which the first hinge leaf is connected to the first floating span; and at least one connector part; anda locking connector associated with the hinge connector for locking the first and second spans together, the locking connector comprising connector parts associated with each of the hinge leafs that are configured and positioned to mate and lock.

21. The floating bridge of claim 20, wherein one locking connector part comprises jaws and a linkage connected to the jaws for pivoting between a locking position and an unlocking position, and wherein the other locking connector part comprises an opening to receive the linked jaws therein, the opening including at least one edge and the linked jaws engaging the edge in response to activation of the linkage.

22. The floating bridge of claim 21, comprising a rod connected to the linkage to activate the linkage.

23. A pontoon for a floating structure, the pontoon comprising a first end, a second end, opposed sides, a top and a bottom, which are connected together to form a hollow, water-tight structure, wherein: the top and bottom are parallel to each other, the sides are parallel to each other and extend normal to the top and bottom, and each of the opposed sides is substantially longer than each of the ends, whereby the pontoon is elongated;at least a portion of the first end being sloped inwardly relative to the top; andthe second end extending normal to the top and bottom.

24. The pontoon of claim 23, comprising a wearing surface attached to the top adapted to carry vehicle traffic when the pontoon is assembled into the floating bridge.

25. A pontoon structure for a floating structure, the pontoon structure comprising a plurality of pontoons each of which comprises a first end, a second end, opposed sides, a top and a bottom, which are connected together to form a hollow, water-tight structure, wherein, for each pontoon: the top and bottom are parallel to each other, the sides are parallel to each other and extend normal to the top and bottom, and each of the opposed sides is substantially longer than each of the ends, whereby the pontoon is elongated;at least a portion of the first end being sloped inwardly relative to the top; andthe second end extending normal to the top and bottom;a first and a second of the pontoons being arranged longitudinally aligned with respective second ends in contact, and connected together.

26. The pontoon structure of claim 25, comprising a plurality of parallel tubes running laterally through each pontoon opening to opposed sides of the respective pontoon, openings and tubes of adjacent pontoons being aligned and defining sets of aligned tubes, a cable passing through each set of aligned tubes adapted to be tensioned to attach adjacent pontoons together.

27. The pontoon structure of claim 25, comprising a wearing surface attached to the top of each of the first and second pontoons, the floating structure adapted to be assembled into a floating bridge and the wearing surface being adapted to carry vehicle traffic when the pontoon is assembled into the floating bridge.

28. The pontoon structure of claim 25, wherein the plurality of pontoons comprises third and fourth pontoons, each of which comprises a first end, a second end, opposed sides, a top and a bottom and comprises the same configuration as the first and second pontoons except that the sides, top and bottom of the third and fourth pontoons are shorter than the sides, top and bottom of the first and second pontoons, the third pontoon being connected to first pontoon with respective first ends being aligned and the fourth pontoon being connected to the second pontoon with respective first ends being aligned such that a space is created between respective second ends of the third and fourth pontoons, the space being adapted to drain liquid therethrough from the pontoon structure.

29. The pontoon structure of claim 28, comprising a wearing surface attached to the top of each of the third and fourth pontoons in respective alignment with the plates attached to the tops of the first and second pontoons, the floating structure adapted to be assembled into a floating bridge and the wearing surface being adapted to carry vehicle traffic when the pontoon is assembled into the floating bridge.

30. A pontoon for a floating structure, the pontoon comprising: ends, sides, a top and a bottom, which are connected together to form a hollow, water-tight structure;a winch within a watertight space;a cable connected to the water winch;a watertight tube comprising a first end near the bottom of the pontoon and a second end near the top of the pontoon adjacent the winch, the tube having a first opening communicating with the exterior of the pontoon and a second opening communicating with the watertight space;the cable passing through the tube and extending from the winch to the exterior of the pontoon.

31. The pontoon according to claim 30, wherein the cable is adapted to be attached to an anchor.

32. A staging area from which a floating bridge can be rapidly deployed, the floating bridge comprising a plurality of floating spans constructed of attached pontoons, the staging area comprising: a site near a water crossing which the floating bridge is to bridge;at least one storage area on the site for receiving pontoons transported by truck;at least one assembly area on the site for assembling the floating spans on water from pontoons; anda launching area for at least one of the assembly sites floating therefrom an assembled span.

33. A floating bridge comprising a plurality of floating spans two of which are pivotally connected for pivoting horizontally on the water and an anchor system attached at least to the pivoting spans, the anchor system comprising a plurality of anchor elements engaging water bottom, at least one for each side of a span, a cable attached to each anchor element at one end, a winch carried by the span for each side of the span, each cable being connected at an opposite end to a winch, the cables being positioned so that operation of a selected winch or winches acts to pivot the span.