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Drop-down bridges

Such bridges are characterized by rotational movement of the span relative to the horizontal axis. The single-wing swing bridge is an asymmetrical system (Fig. 9.1). In the closed state, the span rests on the supporting parts (3) and (4); the axis of rotation (2) is unloaded using a special wedging device (6). When opening, the span structure rests on the axis of rotation, and to ensure a stable position of the span structure and reduce the required engine power, the span structure is balanced by a counterweight (5). The design span L is selected depending on the specified width of the under-bridge clearance, taking into account the distance from the centers of support to the edges of the supports, as well as taking into account the incomplete release of the under-bridge clearance when opening (5-10% more than the width of the under-bridge clearance). The location of the seam (1) of the roadway is possible behind the axis of rotation or in front of it. The latter solution has advantages: at any position of the temporary load, it does not cause a negative support reaction on the support on which the end of the wing is located; during opening, no gap is formed in the roadway through which dirt from the drawbridge falls into the support well, and an accidental fall of a person is not excluded. The seam of the roadway above the main beams and in this case must be arranged behind the axis of rotation so that when opening the main beams do not rest against the structure of the roadway.

Rice. 9.1 - Drop-down bridge: L - design span of the bridge

To ensure the balance of the span of a drop-down bridge at any moment of movement, it is necessary that the centers of gravity of the wing, counterweight and axis of rotation lie on the same straight line, and the moments of the weight of the counterweight Q and the weight of the wing G relative to the axis of rotation are equal. If the counterweight is placed in the support well (see Fig. 9.1), it will require a significant width. The width of the support can be reduced if the counterweight is placed between the beams or trusses of the adjacent span (Fig. 9.2, a) with a device in the support of open niches, and a sub-blade is placed at the end of the wing, pulling it down. The width of the support can be reduced by using a device for hinged attachment of the counterweight to the tail of the wing (Fig. 9.2, b). This will increase the depth of the well into which the counterweight is lowered. In addition, if it is possible for the water level to rise above the bottom of the well, it will need to be waterproofed. The counterweight is additionally connected to the support by rod AB to ensure forward motion and prevent it from swinging. To maintain the balance of such a system, it is necessary that the point Oʹ of the counterweight suspension, the axis O of rotation and the center of gravity of the span (together with the tail section) lie on the same straight line, and the figure OOʹBA is a parallelogram (see Fig. 9.2, b).

Rice. 9.2 - Location of the counterweight of the drop-down span

An important issue is the number and location of the main beams of the movable span, taking into account the clearance of the bridge. For a single-track railway bridge, as well as a road bridge with a small passage width, you need to install two beams. With a large passage width, the number of beams can be increased, but it is advisable to take it as even so that the beams can be connected in pairs with ties.

The drop-down system can also have two wings. It is sometimes used for architectural reasons, but it can be economically feasible if the draw span has a significant length (50-70 m). Here, as a rule, there is a saving in the power of propulsion mechanisms and engines, which must be designed for significantly lower loads (although supplied in duplicate). The width of the supports can also be reduced. Particular attention should be paid to the static diagram of the span in the closed state. There are two main options here: connecting the ends of the wings using a longitudinally movable hinge; closing the span into a three-hinged spacer system with the transmission of thrust through the middle hinge (Fig. 9.3). In the first case, the design of the connection is simple, but the rigidity of the span is relatively low; when a load passes, a fracture of the passage profile above the hinge occurs. Therefore, this solution is unacceptable for railway bridges. In the second case, the design becomes more complicated and a thrust is transferred to the supports, which can be significant, since the system turns out to be flat (f/L ≥ 1/15). However, the structure is more rigid. From the span (see Fig. 9.3), the thrust is transmitted to the support through the stop (1), which limits the rotation of the swinging post (2). The span is slightly unbalanced; when closing, the swinging stand, turning, lifts it and unloads the axis of rotation.

Rice. 9.3 - Spacer system

It is possible to connect the ends of the wings with a lock capable of operating at full bending moment. This solution has not been implemented due to the difficulty of providing a sufficiently rigid lock, designed to withstand significant forces, which, moreover, could be quickly closed and opened.

To bring drop-down drawbridges electromechanical or hydraulic drive. The electromechanical drive (Fig. 9.4, a) has a drive gear (1), which rotates from an electric motor with a gearbox and engages with a toothed arc (2) mounted on the span. A drive option with a gear on the span and a gear wheel on the support is possible. A drive with a crank mechanism has its advantages (Fig. 9.4, b). Here the drive gear (1) rotates the crank (3), the force is transmitted to the superstructure through the connecting rod (4). The advantage of this drive is the zero speed of rotation of the span at the beginning and end of movement. The hydraulic drive (Fig. 9.4 c) consists of hydraulic cylinders (5) and pumping units. The hydraulic cylinder has a piston (6), the rod of which is pivotally connected to the span (7). The hydraulic cylinder is also pivotally connected to the support. By supplying oil under pressure into the cavity above or below the piston, it is possible to create the force necessary to set the superstructure in motion. Hydraulic cylinders have a diameter of up to 500 mm, an oil pressure of up to 10 MPa and a force of up to 2000 kN.

Rice. 9.4 - Drop axle drive

Sliding-opening bridges

The span structure of such a bridge (Fig. 9 5), when raised, rolls back along a special rolling path (1), resting on it with a rolling circle (2) attached to the span structure, which makes a plane-parallel movement. By turning in a vertical plane and rolling back, it completely clears the opening of the drawbridge, which is an advantage of this system.

Rice. 9.5 - Sliding-dropping bridge

Vertical lift bridges

Superstructure vertical lift bridge(Fig. 9.6) when spread, it moves forward in a vertical plane. For this purpose, towers (4) are used, which are supported on special supports or on adjacent spans. The towers are equipped with pulleys (2) through which the cables (1) pass. Cables connect the lifting span with counterweights (3), which lower down when the bridge opens. The lifting height h p of the span structure is determined as the difference in the heights of the under-bridge clearance in the draw span in the closed h 3 and in the open h p states - and the height h 3 can be approximately taken equal to the height of the under-bridge clearance in fixed navigable spans. When pre-determining the height of the towers, a margin is left A, equal to 3-5 m.

Rice. 9.6 - Vertical lift bridge

When determining the dimensions of the tower, care is taken to ensure its stability against overturning both along and across the bridge. Significant tensile forces in the tower legs are undesirable. Therefore, the length of the base of the tower when located on an adjacent span is usually assigned to about 1/6 H, and when resting on supports - 1/4÷1/5 H; The width of the tower across the bridge is usually at least 1/6 H.

In addition to the main variety of vertical lift bridges with the entire span being lifted on special towers, systems were used with a rising roadway structure at a low lift height h p, with a span descending under water, and in other rare cases.

The lifting span structure can have through or continuous main trusses. For railway bridges, as a rule, two main through trusses with a ride on the bottom are used, and for road bridges other types of structures are also used, for example, a span with a ride on top and with several main beams. In this case, powerful transverse beams will be required, at the ends of which the counterweight cables will be attached. A span with through main trusses can have the same design as a typical span of a conventional fixed bridge.

Additionally, only the elements of the support post and the upper chord in the first panel are required. A transverse lifting beam is attached to the upper node they form.

Towers in most cases consist of two longitudinal trusses, including front and rear posts and a lattice, and two bracing trusses located in transverse planes. The link trusses at the bottom are portals to provide passage. At the top, the heads are arranged in the form of a system of beams that absorb the load from the pulleys and transfer it to the towers. The front pillars of the towers are vertical, the rear pillars are usually inclined or outlined in a broken line. The distance between the axes of the front pillars in the transverse direction is, as a rule, equal to the distance between the axes of the main trusses of the lifting span or the one adjacent to the lifting span (if the tower is located on an adjacent span). The width of the tower at the top in the longitudinal direction is taken to be minimal, insufficient for the free movement of the counterweight inside the tower. At the bottom, the tower must have a width sufficient to ensure its stability against tipping over. If small spans adjoin the draw span, then the towers are placed on closely spaced supports. If the spans in adjacent spans are long, then the towers are placed on them (see Fig. 9.6). Sometimes, with a small lifting height and a significant height of adjacent spans, it is possible to do without towers by placing the heads and pulleys on the upper chords of adjacent spans. Lifting cables, thrown over pulleys and connecting the lifting span to the counterweight, are attached to the span using transverse lifting beams.

The tower head (Fig. 9.7) is a beam cage that absorbs the load from the pulleys and transmits it to the tower nodes. The pulleys (1) rest with their axes through bearings (2) on the longitudinal beams (3). Each longitudinal beam is located at one end on the front transverse beam (4), attached to the front posts (5) of the tower, and the other end is connected to the rear transverse beam (6). In places where concentrated forces are transferred to the beams, stiffeners are installed. In order for the longitudinal beams (3) to be stable and well withstand horizontal wind and random loads, their cross-section can be made box-shaped or the points of support on the front transverse beam can be strengthened using brackets.

Rice. 9.7 - Tower head design

Vertical lift bridges have significant rigidity. Standard structures with minor modifications can be used as lifting spans. The system is quite economical if the lift height is not too high. Disadvantage - the presence of towers that worsen appearance bridge.

To set vertical lift bridges in motion, as a rule, an electromechanical drive is used. Electric winches set the superstructure in motion using a system of blocks and cables attached to the superstructure and towers. Winches can be placed on the span, then the synchronization of their operation can be easily ensured. A drive is used in which electric motors with gearboxes are placed on towers, and the force from the drive gear is transmitted directly to the ring gear of the pulley. This device is reliable in operation, but requires synchronization of the rotation of the pulleys on both towers, which can be achieved using a special electrical system connecting the drive motors (electric shaft).

Swing bridges

Such drawbridges have spans that rotate around a vertical axis. When opened, the span structure is located along the river, usually opening two identical spans for navigation. One of the varieties can be a swing bridge (Fig. 9.8) with the superstructure supported on rollers (2) using a central drum (4) attached to the superstructure. The rollers roll along a circular track (5) laid on a support (6). To center the span and rollers, a fixed axis (3) is used, which does not carry a vertical load. Wedging devices (1) are installed on the outer supports, taking on part of the constant load when closed.

Rice. 9.8 - Rotary span structure

Swing bridges They are relatively simple in design, have sufficient rigidity and, when deployed, do not restrict the height clearance for ships. Their disadvantages are the danger of ships collapsing on the span and, as a consequence, slowing down the passage of ships, as well as the significant width of the central support. When choosing a swing bridge system, you need to keep in mind that when the span is supported on rollers, they also work under operational loads. To prevent rapid wear of the rollers, it is necessary to install quite a lot of them; The diameter of the rolling circle becomes significant and the dimensions of the central support increase. Rollers are subject to uneven wear, and their replacement involves raising the span. Accurate alignment of the circular path under the rollers is required, otherwise the movement resistance and wear of the rollers increases sharply.

The distance between the main trusses of the span when driving on top is taken to be 2.5-3.5 m, and the number of main trusses depends on the size of the passage on the bridge. In the case of cramped under-bridge clearance, a span with a ride below and two main trusses is used. Main trusses can be through or continuous; As a rule, for spans up to 50 m, solid main trusses have an advantage. The height of the main trusses usually increases towards the central support, where it reaches approximately 1/8-1/15 L; in the middle of the span the height of the main trusses is about 1/10-1/20 L.

To rotate the span, an electromechanical or hydraulic drive can be used, similar to those used for drop-down bridges with the difference that the rotation here occurs relative to the vertical axis.

The given examples do not exhaust the variety of systems and varieties of metal drawbridges. IN suitable conditions drop-down bridges with a counterweight located above the roadway (which reduces the size of the support), as well as rocker drop-down bridges, can be used. With a draw span length of more than 50 m, in many cases through trusses are appropriate. When the underbridge clearance is cramped in a closed state, a movable span with a ride below is appropriate.

An example of a drop-down drawbridge design

The design of the city drawbridge, which allows the passage of sea vessels with an under-bridge clearance of 55 m wide and 60 m high, was developed by Lengiprotransmost. The drawable part is covered by a single-wing drop-down span, which in the closed state has a design span of 60.4 m. The opening angle of 77° provides the under-bridge clearance (Fig. 9.9). The tail sub-blade is not used. In the closed state, the span rests on a fixed supporting part with the end of the wing (1) on a hinged post located on the same vertical with the axis of rotation, and is a simple beam on two supports with a cantilever on which the counterweight is placed. The stable position of the wing in the closed state, as well as the unloading of the axis of rotation, is ensured due to the imbalance of the wing when opening (the moment from unbalanced forces is 6 MN∙m). This solution required an increase in drive power, but simplified the design due to the absence of sub-blade mechanisms.

Rice. 9.9 - Drop-down movable span structure: 1 - outline of the underbridge clearance; 2 - wing in open position; 3 - axis of rotation; 4 - counterweight; 5 - support stand; 6 - wing in closed position

The bridge with a carriageway width of 18.5 m is designed for four-lane traffic. In addition, two sidewalks of 2.25 m each are provided. 9.10). In cross section, the span has four main beams of solid section and an orthotropic slab of the roadway in the form of a horizontal sheet 12 mm thick, reinforced with longitudinal ribs 80x10 mm every 400 mm and transverse beams 500 mm high, placed every 2200 mm. The walls of the main beams have a thickness of 12 mm (in the tail part - 20 mm) and are reinforced with longitudinal and transverse stiffeners. The material of the span is steel classes C-35 and C-40. Two counterweights are located between the main beams. Drive hydraulic cylinders are located on both sides of the pairs of beams. When opened, the counterweights are lowered into the support well, the bottom of which is 3.5 m below the water level in the river. Therefore, special attention is paid to the waterproofing of the well: its lower part is protected from water penetration by a continuous casing made of steel 10 mm thick, reinforced with stiffeners. The casing is welded and tested for water resistance before concreting the support.

Rice. 9.10 - Cross section of the counterweights: 1 - main beams; 2 - counterweight; 3 - hydraulic cylinder axis

During deployment and in the expanded state, the wing rests on rotation axes, separate for each main beam (1); double-row self-aligning roller bearings (2) (8 pcs. in total) were used, allowing a static load of up to 4.9 MN (Fig. 9.11). The weight of the wing with counterweight is approximately 24 MN.

Rice. 9.11 - Location of main mechanisms

The span structure is driven using a hydraulic drive. The hydraulic cylinders (3) are located vertically in cross section in four planes and create a pair of forces with a shoulder of 3.4 m, so during their operation there is no additional overload of the rotation axis. The hydraulic cylinder rods are hingedly attached to the span, which includes special transverse beams (7) with brackets (8). In the room, inside the support of the adjustable span, there are the main pump installations, which ensure opening in 4 minutes, as well as spare pumping installations operating from an autonomous power plant.

The support posts (9), on which the span rests in the closed state, simultaneously serve as a mechanism for unloading the wing rotation axes (Fig. 9.12). When the wing is open, the pillars are located obliquely, and the span rests on the axis of rotation. During closing, when the wing approaches a horizontal position, the strut is brought to the wing using a special rod and engages with the supporting part attached to the lower chord of the main beam. At this moment, the support strut has a slight inclination to the vertical, and the wing - to the horizontal. With further movement, which is facilitated by the imbalance of the wing, the stand rises to a vertical position. In this case, the wing is raised by approximately 5 mm, the axis of rotation is unloaded, and a gap is formed in the bearing of the rotation axis.

Rice. 9.12 - Support stand: 1 - axis of rotation; 2 - clearance under the bearing; 3 - stand for the axis of rotation; 4 - support post after opening; 5 - thrust; 6 - support post in closed position; 7 - support

To soften the impact when the wing approaches the maximum opening position, buffer devices (6) made of rubber are provided, and to fix the wing in the open position, automatic hydraulic locks (5) are provided in the form of retractable bolts in the recesses at the ends of the main beams (see Fig. 9.11) .

An example of a vertical lift bridge design

The design of the railway bridge span was developed by Lengiprotransmost in 1978. According to navigation conditions, the passage of large ships requires a bridge opening of 40 m and a lifting height of 30 m (Fig. 9.13).

Rice. 9.13 - Vertically lifting movable span structure

A standard span structure (10) with a span of 44.8 m was used as a lifting structure with the addition of elements necessary to lift it to position (9). The lifting span towers are located on adjacent spans and have welded elements with mounting connections on friction bolts (steel 15HSND). The front racks of the towers (6) are vertical, box-shaped. Significant efforts are transferred to them. The inclined rear pillars (1), like the lattice elements of the longitudinal vertical trusses of the towers, have an H-shaped section.

In the transverse planes there are connections (11), and, in addition, in the horizontal planes in each node of the towers there are cross transverse connections. The top of the tower is a beam cage supported on the front (4) and rear (2) transverse beams. The bearings of pulleys (3) having a diameter of 2700 mm rest on the head. Each pulley has a toothed ring on one side, with which a drive gear meshes, driven by an electric motor through a gearbox. The gears of two pulleys on one tower are located on one common shaft. To synchronize the lifting of both ends of the span, a device called an electric shaft is used, which requires laying cables connecting the drive motors on both towers. In order to avoid laying cables under water, a lightweight cable bridge (8) is used.

The span structure is balanced using counterweights (5), consisting of metal frames with monolithic concrete filling and removable reinforced concrete slabs for precise weight adjustment. Provision is made for hanging counterweights from the head beams using steel belts to unload the ropes during repairs. Suspension cables (7), 10 on each pulley, connect the span and counterweights (cable type 37-G-V-ZhS-O-N-140). The cables are attached to the lifting beam (12), located in node B1 of the span.

The span is equipped with additional devices (Fig. 9.14). Suspension cables are attached to the lifting beam (1) through threaded steel rods screwed into anchor cups (11) and having nuts (3) at the ends to adjust the length of each cable. It can be adjusted using adjustable hydraulic jacks (4) from a special bridge (5). When the cables approach the lifting beam, they are separated on both sides by steel deflection castings (2). To prevent the span structure from swinging on the cables during lifting, there are guide devices in the form of eight clips with rollers attached to the span structure. During lifting, the rollers roll along the guide plates of the towers. In the plane of the lower chord, in the support units of one end of the span, clips with three rollers (9) are installed, preventing the movement of the span in both the longitudinal and transverse directions. The remaining support units of the upper and lower chords are equipped with cages with one roller (10), which only prevent transverse movements. This ensures a stable position of the span during lifting and freedom of temperature movements of the support units. Pneumatic buffer devices (8) are attached to the supporting transverse beam of the lifting span to prevent impacts when lowering the span. To accurately fix the span in the transverse direction, a centering device (7) is used, attached to the support, which includes a protrusion with bevels attached to the supporting transverse beam.

Rice. 9.14 - Details of the movable span

The weight of the lifting span is 2.23 MN; it is not completely balanced by counterweights. The span is 40 kN heavier than the counterweights; in addition, the unbalanced part of the cables when the span is lowered is 66 kN, which creates a stable position of the span in the closed state. For additional guarantee against spontaneous lifting of the span, for example from the action of rising wind, span locks are provided. After lowering the span, the lock bolt (6) moves with the help of a mechanical drive (12) in the longitudinal direction and enters the cutouts of the centering device box,

The railway track on the span is built on metal crossbars. For precise alignment of the rail track on the movable and fixed spans, rail locks are provided.

The duration of lifting by the main drive is 2 minutes. In addition to the main one, there is a spare drive with an autonomous power plant (lifting time 17 minutes) and a manual emergency drive (lifting time 150 minutes). The power of the main and synchronizing drives is 45 - 22 = 67 kW.

Drawbridges are those in which the span (one or more) can move, forming a free passage for ships whose height exceeds the under-bridge clearance.
TO modern types Drawable railway bridges include swing, swing and lift bridges.
The drawbridge during construction is shown in Fig. 1.

Rice. 1. During the reconstruction of a bridge with a total length of about 800 m, which included raising it by 1.20 m, a lifting span weighing 1,050 tons was launched into the span afloat using four barges

Swing bridges.

Swing bridges are opened by rotating the span around a vertical axis, which can be located in the middle of the span, at one of its ends, or at an intermediate point.
According to the method of support, they are divided into swing bridges with a central axis of rotation and with a central drum. These types of supports are sometimes combined.
In swing bridges with a central axis of rotation, the weight of the span is transferred to the axis of rotation, and when closed, the moving load is transferred to the central bull using a wedging mechanism. Support wheels placed under the turning plate ensure the span is stable when turning.
In swing bridges with a central drum, the weight of the rotating span is transferred through a riveted drum-shaped structure to a series of rollers located between the upper and lower rolling circles. Radial links connected to the ring enclosing the axis of rotation and to the roller guides serve to center the rotation.
In most swing bridge designs, the wings are arranged to be the same length, and the bridge is balanced relative to the center of rotation. When crossing narrow rivers, spans are sometimes used, the outer part of which is longer than the coastal part; in this case, balance is achieved using counterweights.
The length of the wings of the swing bridge is determined primarily by the requirements of the standards governing the width of the clearance for shipping. Another factor influencing the purpose of this length is the angle of intersection of the watercourse.
In cases where the width of the shipping clearance is equal to or more than 15.2 m, through trusses with a ride on top or bottom of a closed or open type are usually used. When the width of the shipping gauge is 12.2 m or less, solid beams with a ride on the top or bottom are used.
In earlier years, the United States used mainly swing bridges with a central drum, which were also the earliest of the metal swing bridges. Such structures, as well as bridges with combined support, were preferred over swing bridges with a central axis, especially for heavy multi-track long-span structures. However, over time, the prevalence of center-axis swing bridges has increased and they are now widely used in American practice.
Important advantages of this latter type are simplicity of design, saving of materials and space, reduction in the number of parts requiring the use of special materials and special precision of work, as well as ease of installation.
This design also allows for a reduction in the size of the central bull. Simplicity of construction leads to reduced cost.
Despite all these advantages, the use of swing axles with a central axis, apart from individual examples, is limited to light single-track spans of relatively short length, approximately 45-75 m. Only a few single-track spans of such a system with a span of 79 m and one span of 139.6 m long, as well as several double-track spans with a length of 76-119 m, have been built.

Swing bridges with a central drum are suitable for solid and through span structures 30-70 m long, mostly single-track. Combined swing bridge systems are used for through-span structures with a length of 60-152 m, mainly double-track.
Both types of swing mechanisms vary greatly in detail and load capacity.
To accommodate the longitudinal and transverse beams of the central drum, which ensures a more uniform transfer of load to the central bull, as well as the necessary connections and the turning mechanism, both of these types require a greater distance between the base of the rail and the head of the central bull than in swing bridges with a central axis.
In Fig. Figure 2 shows the rail lock of the swing bridge.

Rice. 2. Special devices (rail locks) at the ends of the turning spans to ensure the correct position of the track in plan and to facilitate the passage of rolling stock wheels along the rail joints

The disadvantage of swing bridges is the need to locate the central bull in the riverbed. This creates certain inconveniences for navigation even when the bridge is raised and railway traffic is interrupted. It follows from this modern trend transition from swing bridges to drop-down and lifting bridges.

Drop-down bridges.

In a drop-down bridge, one end of the movable span is fixed. The span rotates around a hinge or axle at the fixed end, with the free end describing a vertical arc. All movements of spans of this type occur in the vertical plane, in contrast to rotary ones, which move in the horizontal plane. Therefore, drop-down bridges are advisable in conditions where there are clearance restrictions on the sides of the bridge. Their other advantage is that there is no need to build a central bull and safety devices (from the pile-up of ships), due to which the river bed is not cluttered.
The use of drop-down bridges began a long time ago, facilitated by the simplicity of their design. However, heavy drop-down spans of railway bridges with special devices driven by power plants appeared relatively recently; designs of this kind need significant improvement.
Bridges of this type fall into two main classes: hinged opening and sliding opening. The most widely used are hinged types, which include the Brown, Rall, Strauss systems, as well as the American bridge, etc. In the American bridge (Abt design), the counterweight is hinged to the posts in the tail section and is located on the channel side. When the wing is raised using a mechanism located on the shore side, the counterweight falls vertically down. In Brown system bridges, the counterweight, located on the shore side of the strut, hangs at the end of the rocker arm, which is pivotally connected through rods to the lifting wing.

The spans of the Rall system are hinged at the center of gravity to a rod, at the lower end of which there is a fixed hinge. An axle is attached to the span, on which two rollers sit freely, supported by roller beams. The movement of the superstructure is limited by rods, which cause it to tip over.
The Strauss design is divided into types with a counterweight located above or below the roadway, and a type with a trunnion at the heel (rocker bridges).
Retractable spans of the sliding-opening type open when rolled back along guides curved in the profile. A well-known design of this type is the Scherzer sliding-opening bridge.
Lift bridges. In a drawbridge, the hole is cleared when one span is lifted. In the lowered position, the movable part is a conventional span on two supports.
In most cases, lifting is carried out using cables passing through pulleys on towers installed at the ends of the span. Counterweights are suspended from the ends of the cables. Sometimes hinged frames are used instead of cables to move the span.
The advantages of lift bridges are the comparative freedom to choose the span length and simplicity of design. However, their lifting mechanism is quite expensive, and maintaining wire ropes and other parts is quite a difficult task.
Further, if in other systems of drawbridges, when the span is opened, the height of the under-bridge clearance is unlimited, then the drawbridge cannot be raised above a certain, pre-fixed position. The AREA technical specifications for movable bridges provide the necessary guidelines for the design and construction of these structures.
Shipping alarm. Bridges over navigable rivers must be equipped with navigational signaling that meets the requirements of the relevant organizations.

The utility model relates to the field of bridge construction and can be used in the construction of road cable-stayed drawbridges, usually in cities across wide navigable rivers. The technical objective of the utility model is to reduce material and financial costs for the construction of a cable-stayed drawbridge, as well as to use all the hollow pylon struts in the navigable span simultaneously and as lifting supports for the vertical movement of the drawbridge to the design level. The technical problem is solved due to the fact that a cable-stayed vertical lift bridge, consisting of cable-stayed girder spans, has a vertical lift span and two pylons with four hollow pillars in the navigable span, and is distinguished by the fact that all pylon posts in the navigable span are used as lifting supports, inside of which there are counterweights, traction winches and rope-pulley systems for moving the span upwards. In this case, all the pylon posts at the top are rigidly connected to each other along the facade and across the bridge by horizontal metal beams, which are used as pedestrian bridges. At the same time, people are lifted onto them by special observation elevators located outside all pylon posts.

The utility model relates to the field of bridge construction and can be used in the construction of road cable-stayed drawbridges, usually in cities across wide navigable rivers.

Various designs of large and extra-class cable-stayed fixed bridges across wide and deep navigable rivers and straits are known (Byte bridges. A.A. Petrovsky and others - M.: Transport, 1985. Metal bridges. N.N. Bychkovsky, A.F. Dankovtsev. In 2 parts. Saratov, 2005. Engineering structures in transport construction. In 2 books. P. M. Salamakhin et al. - M.: Academy, 2008. Bulletin of Bridge Construction. Journal. 2003, 1; 2 ).

To ensure a navigable height clearance (up to 70 m or more), high supports are built, which requires significant material and financial costs for the bridge itself and for the construction of long overpass structures to them in order to provide the design slopes for vehicle access to the bridge. However, such solutions are not always possible due to the lack of necessary territories, especially in the cramped conditions of urban development on the banks of a water barrier.

The design of a metal cable-stayed single-pylon drawbridge is also known (Patent for utility model 118319 dated July 20, 2012 “Metal cable-stayed single-pylon drawbridge”), in which the part of the cable-stayed beam span (VBPS) above the shipway, adjacent directly to the pylon, is opening by rotating it upward around a horizontal axis using counterweights of a rope-pulley system and traction winches. These elements are placed inside both hollow pylon posts (reinforced concrete or metal).

The main disadvantage of a cable-stayed bridge is the following: during the erection of the bridge, the fixed part of the VBPS is kept from horizontal shift by its cables to the pylon with a special rigid metal stop placed in the bridge abutment. In addition, the fixed part of the VBPS in the open position of the bridge may have (like a cantilever) significant transverse vibrations (amplitudes) when exposed to wind, which will complicate the process of disconnecting and connecting the adjustable and fixed parts of the VBPS. The consequence of this may be the impossibility of raising the bridge in strong winds.

There are also known designs of vertical lift bridges (for example, across the Neva, Northern Dvina, Svir and other rivers), in the navigable spans of which beam spans and two lift towers with elements of a rope-pulley system and guides for the vertical movement of the span are located buildings [Drawbridges. IN AND. Kryzhanovsky - M.: Transport, 1967].

The main disadvantage of the vertical lift bridge adopted as a prototype is the limitation of the navigable clearance in height. When the height of the towers is greater than the width of the navigable span, such bridges become unprofitable due to the high cost of installing lifting towers.

The technical objective of the utility model is to reduce material and financial costs for the construction of a cable-stayed drawbridge, as well as to use all the hollow pylon struts in the navigable span simultaneously and as lifting supports for the vertical movement of the drawbridge to the design level.

The technical problem is solved due to the fact that a cable-stayed vertical lift bridge, consisting of cable-stayed girder spans, has a vertical lift span and two pylons with four hollow pillars in the navigable span, and is distinguished by the fact that all pylon posts in the navigable span are used as lifting supports, inside of which there are counterweights, traction winches and rope-pulley systems for moving the span upwards. In this case, all the pylon posts at the top are rigidly connected to each other along the facade and across the bridge by horizontal metal beams, which are used as pedestrian bridges. At the same time, people are lifted onto them by special observation elevators located outside all pylon posts.

The utility model is illustrated in the drawing, where in FIG. Figure 1 shows a diagram of a fragment of a cable-stayed bridge with a navigable span, where it is indicated:

a - section of the pylon stand with a counterweight placed in it, a traction winch and a rope-pulley system for lifting the span;

b - general form along the façade of the bridge there are pylon posts with fan system cables and an observation elevator;

c - cross section of the bridge in the navigable span;

d - top view of the pylon support and parts of the lifting and cable-stayed beam spans;

1 - cable-stayed beam spans;

2 - lifting span;

4 - pylon stands;

5 - stiffening beams;

6 - panoramic elevators;

7 - observation pavilions on the heads of the pylon posts;

8 - counterweight;

9 - traction winch;

10 - support beam;

11 - pulley rollers;

12 - consoles for lifting (jacking) beams of the lifting span;

13 - supporting parts;

14 - pylon support.

Cable-stayed vertical lift bridge is an extended structure consisting of several cable-stayed girder spans 1 and at least one vertical lift span 2 in the navigable span, as well as several pylon supports 14. The cable-stayed girder spans 1 are supported by cables 3 of the fan system. The pillars of the pylons 4 at the top are rigidly connected to each other along the façade and across the bridge by metal beams.

A cable-stayed vertical lift bridge works as follows. The lifting span 2 moves upward using counterweights 8, traction winches 9, a rope-pulley system consisting of steel ropes (cables), various rollers 11, some of which are fixed to the support beam 10 and to four consoles 12 of the span 2.

In the lower (unraised) position, spans 1 and 2 rest on supporting parts 13 placed on pylon supports 14 of the navigable span.

During the raising of the bridge, pedestrians, as well as maintenance personnel, can move from one part of the bridge to another along stiffening beams 5, on which decking and railings are installed. Lifting people onto the tops of the pylon posts 4 is carried out by panoramic elevators 6, which are attached to the facade surfaces of the posts 4. Pavilions 7 (or canopies) with fences can be mounted on the tops of the posts 4. These pavilions (or canopies) can also be used as observation platforms.

The mass of counterweights, the power of winches, and pulleys are calculated based on data on the length and mass of the lifting span.

The utility model expands the scope of use of pylon struts and simplifies the design of supports in a navigable span.

1. Cable-stayed vertical lift bridge, consisting of cable-stayed girder spans and having a vertical lift span in the navigable span and two pylons with four hollow racks, characterized in that all pylon racks in the navigable span are used as lifting supports, inside which are placed counterweights, traction winches and rope-pulley systems for moving the span upwards.

2. Cable-stayed vertical lift bridge according to claim 1, characterized in that all the pylon racks at the top are rigidly connected to each other along the facade and across the bridge by horizontal metal beams, which are used as pedestrian bridges, while lifting people onto them is carried out by special observation elevators located outside all pylon posts.

LIFT BRIDGE

the most common type of drawbridge, characterized by the presence of one span (sometimes two), which can be raised to allow ships to pass. In some highways, not the entire span is raised, but only the roadway.

• - a lighter gas compared to atmospheric air, which fills the shell of aeronautics aircraft to create aerostatic lift...

  Encyclopedia of technology

• - a drawbridge, the movable span of which, when passing ships, is lifted up along guide pylons - we move the bridge - zdvižný most - Hubbrücke - emelhető híd - өргөгддөгүүр - most podnoszony - pod basculant - most na podizanje - puente...

  Construction dictionary

• - ...

  Spelling dictionary of the Russian language

• - ...

  Together. Apart. Hyphenated. Dictionary-reference book

• - LIFTING, lifting, etc. see lift...

  Dictionary Dahl

• - oh, oh. 1. see raise, -sya and rise. 2. Serving for lifting, upward movements. P. mechanism. P. tap. 3. One that can be lifted. P. bridge. 4. Issued for expenses for moving to a new place of work...

  Ozhegov's Explanatory Dictionary

• - lifting, lifting. 1. Serving for lifting. Lifting crane. Lifting machine. 2. adj., by meaning associated with lifting or lifting something. Lifting weight. Lifting work. 3...

  Ushakov's Explanatory Dictionary

• - lifting adj. 1. ratio with noun rise associated with it 2. Characteristic of rise, characteristic of it. 3. Constructed so that it can be lifted; rising...

  Explanatory Dictionary by Efremova

• - oh, oh. 1. Related to ascent, moving something. up. Lifting work. Lifting force of the vessel. || Intended for lifting. Crane. Lifting mechanism. 2...

  Small academic dictionary

• - ...

  Spelling dictionary-reference book

• - vertical "...
• - ...

  Russian spelling dictionary

• - ...

  Russian word stress

• - ...

  Word forms

• - portal,...

  Synonym dictionary

• - lifting portal,...

  Synonym dictionary

"LIFT BRIDGE" in books

Bridge

Bridge This was still in the first year of living in St. Petersburg. At noon, as usual, Kulibin went to his place for dinner. The wife called to the table, at which the children were already sitting, but Ivan Petrovich hesitated. He stood at the window, basked in the first spring sun, watched how, weaving between puddles, along the weak

Bridge