How many varieties of bridges are there in the world? Dozens! Arched, cantilever, movable, ice, pontoon, retractable, flooded, lifting, turning, hanging, girder, table-like and many others. But in this article we will talk with you about aesthetically verified and reliable variations - with hanging cable-stayed constructions of coatings, as well as about such systems themselves.
Cable-stayed and hanging systems
Hanging structures are steel structures, the bearing components of which are aimed at stretching. They are as follows:
- steel wire ropes;
- strip or round steel;
- membranes (special steel sheets);
- profiles of rolling type (for presentation - hard metal threads) , capable of not only tensile, but also bending.
Cable-stayed structures, unlike the previous ones, have not only stretched threads in the coating, but also rigid elements. The latter work just on the bend, it is possible to impose fences on them, including including roofing and flooring.
Both hanging and cable systems can cover a span of up to 200 m. However, their average length in practice ranges from 50-150 m.
Design Advantages
We list the advantages of hanging and cable-stayed structures:
- Creating a favorable basis for visibility, acoustics, lighting.
- You can apply a variety of structural forms of cable-stayed suspension structures, which leads to a variety of variations of architectural designs.
- Bridges of this type are capable of covering an impressive length of spans.
- During the construction of the facility, one cannot fail to note the good transportability of the structures used - flexible tapes and ropes can be rolled up or coiled.
- The process of building a bridge is simplified by the fact that you do not need to install scaffolds, scaffolding.
- When the load is perceived in the stretched bearing structure, the entire section area works entirely. When using high-strength steel in their production, due to this quality, the consumption of this metal can be significantly reduced.
Design flaws
We touch on the disadvantages of hanging and cable-stayed coatings:
- An increased degree of deformation of the structure is observed - this is especially characteristic of hanging varieties, since there it is necessary to establish a prestress to stabilize the threads.
- To perceive the spread of stretched bearing components, a number of support contours are required.
- In some cases, there are difficulties in constructing a drainage system.
Features of cable-stayed systems
The composition of cable-stayed suspension structures is bearing straight, stretched ropes or cables, as well as rigid components - racks, beams, etc. Given the fact that the cables are straightforward, they can consist of strip profiles or rods. It is important to note that the angle of inclination of the cables should not reach 25-30 degrees.
The simplest diagram of cable-stayed systems is cable-stayed. It is characteristic of her that the guys in one or more places support a stiffener beam. At the same time, they themselves either diverge rays from the tops of the pylons, or resemble the shape of a harp when they are parallel to each other.
Varieties of Hanging Systems
After cable-stayed systems, let's look at the types of hanging:
- One-belt . They are performed over rooms of both round and rectangular shapes. The perception of the spread of metal threads is provided by pylons, guy wires, extensions to the building and so on. The use of flexible threads or arches as intermediate supports is characteristic. The coating is stabilized by reinforced concrete roofing panels, monolithic seams.
- Two-belt . In addition to the bearing ropes, they also have stabilizing ones that connect with the bearing extensions or struts. Least of all drawbacks of hanging systems are found when using a convex-concave combined coating scheme.
- Cable nets (a kind of two-belt). Their indisputable advantages are the variety of shaping and architectural advantages achieved by qualified design.
- Membrane coatings . These are continuous single-layer coatings consisting of sheets or strips, which are cut and connected in such a way that they form a pre-planned surface with double or single curvature. They are distinguished against the background of other hanging structures by the execution of the enclosing and supporting task. But the significant disadvantages of the membrane coating are low fire resistance due to the large surfaces of the open metal, corrosion resistance, as a result of which the minimum thickness of the steel sheet should be in the range of 4-5 mm with an allowable 1-2 mm. Membranes can be cylindrical, circular, tent-shaped.
We turn specifically to the suspension and cable-stayed bridges.
Cable-stayed bridge
This variety is characterized by a special type of load-bearing systems - cable-stayed trusses, which are formed by stretched flexible rods (cables). Sometimes combined variations are found in which the lower parts of these trusses are replaced by stiffeners. The work of the latter is aimed at bending, and the function is to support the platform of the roadway. Guys here are high-strength wires formed in bundles or steel ropes.
Both cable-stayed farms and combined systems in this structure are supported by pylons. From the places where the cables are suspended on the pylon, the horizontal component of their reference pressure is transmitted to the anchors by a guy system. If a stiffening beam is present, then the ends of the guy wires are fixed on it, which makes the system turn outwardly uncontrolled. The design of the carriageway is already attached to the nodes of cable-stayed farms.
The first cable-stayed bridge in the Soviet Union was built in 1932 - across the Magana River (modern Georgia). However, the first bridge of the modern cable-stayed system appeared only in 1956 - this is the Swedish Stomsund. The pioneer cable-stayed railway station was built in 1979 in Belgrade.
The first cable-stayed bridge on the territory of modern Russia is Oktyabrsky across the Sheksna River (Cherepovets). Its construction was completed in 1979. There is also a cable-stayed record holder in the Russian Federation. This is the Russian bridge in Vladivostok, overlapping the Eastern Bosphorus Strait . It stands out with the longest span - 1104 m (the total length is 1886 m), which is supported by two pylons.
Advantages and disadvantages of the cable-stayed bridge
Consider the pros and cons of such bridges. For a better perception, we decided to present you them in the form of a table below.
| Advantages | disadvantages |
| Lightweight supporting structures | Reduced rigidity - used only as city or road bridges |
| Overlapping ability is large enough | In rare cases, it can be used as a railway bridge - only with a certain design of a stiffener |
| The material consumption is minimal, besides, the purchase of expensive structures is not required | |
| Mounting possible | |
| Architectural aesthetics | |
| Unlike hanging, they are more motionless. | |
In conclusion, consider suspension bridges.
Suspension bridge
Suspension (aka - suspension) bridge - a structure whose main bearing structure is flexible elements (ropes, chains, cables, etc.) that operate in tension, and the carriageway is suspended. Such bridges are a real find in cases when a large coverage is required, and it is dangerous or impossible to establish intermediate supports (for example, on a navigable river).
The supporting structures are suspended between the pylons built on both banks. Vertical beams are already attached to these cables, to which the road part of the main span is directly suspended. The concentrated load allows you to change the supporting structure of its shape, which reduces the stiffness of the bridge. To prevent this from happening, the roadway is reinforced with longitudinal beams.
The first suspension bridges were built by the ancient Egyptians, Incas, other nationalities of Central and South America, Southeast Asia. Constructions of a modern look began to appear in the XVII-XVIII centuries. in Spain, France, Great Britain, and later in the USA. In Russia, the first suspension bridge was built in 1823 in the Ekaterinhof park in St. Petersburg. One of the most famous domestic suspension bridges today is Crimean in Moscow, built in 1938.
Advantages and disadvantages of suspension bridges
Consider the pros and cons of these suspended structures, which are presented in the table below.
| Advantages | disadvantages |
| The construction of a long main span requires a relatively small consumption of material | Insufficient rigidity - it is dangerous to operate the bridge, for example, during a storm |
| Low deadweight | Reliable support pylons require a solid foundation |
| Bridges of this design can be built high above the water surface, which is very useful for navigable water bodies. | When the load is very uneven, the canvas of the suspension bridge tends to bend, which prevents its use as a railway |
| No need for intermediate supports | |
| Under the strong action of the elements or seismic loads, these bridges can bend without causing any harm to the structure as a whole | |
That's all we wanted to tell you about guys, cable-stayed structures, bridges. Suspension and cable-stayed coatings are light in construction, able to cover large spans, harmoniously looking, providing room for design solutions. However, they also have their drawbacks, raising restrictions, for example, for the construction of a certain type of bridge.