Cable-stayed systems: device, advantages, features and disadvantages

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

How many types of bridges are there in the world? Dozens! Arched, cantilever, adjustable, ice, pontoon, retractable, floodable, lifting, rotary, hanging, beam, table-like and many others. But in this article we will talk with you about an aesthetically verified and reliable variation - with hanging cable structures of roofs, as well as about such systems themselves.

Cable-stayed and suspended systems

Hanging structures are steel structures, the bearing components of which are directed to tension. Here they are:

• steel wire ropes;
• flat or round steel;
• membranes (special steel sheets);
• rolled profiles (for presentation - hard metal threads), capable of not only stretching, but also bending.

Cable structures, unlike the previous ones, have not only stretched threads in the coating, but also rigid elements. The latter work just for bending, it is possible to impose fences on them, including those that include roofing and flooring.

Both hanging and cable-stayed systems are able to block the spandistance up to 200 m. However, their average length in practice varies between 50-150 m.

Design advantages

Let's list the advantages of hanging and cable-stayed structures:

• Creating a favorable basis for visibility, acoustics, lighting.
• A variety of structural forms of cable-stayed suspended structures can be used, leading to a variety of architectural variations.
• Bridges of this type are capable of covering impressive 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 into rolls or coils.
• The process of building a bridge is simplified by the fact that there is no need to install platforms, scaffolding.
• When a load is received in a tensioned load-bearing structure, the entire cross-sectional area works. When using high-strength steel in their production, due to this quality, it is possible to significantly reduce the consumption of this metal.

Design flaws

Let's touch on the disadvantages of hanging and cable-stayed roofs:

• There is an increased degree of deformation of the structure - this is especially true for hanging varieties, because there it is necessary to set a prestress to stabilize the threads.
• To perceive the spread of the stretched load-bearing components, a number of support contours are required.
• In some cases, there are difficulties in installing a drainage system.

Features of cable-stayed systems

The composition of cable-stayed suspended structures is load-bearing straight stretched ropes or cables, as well as rigid components - racks, beams, etc. Given that the guys are straight, they can consist of strip profiles or rods. It is important to note that the angle of inclination of the shrouds should not reach 25-30 degrees.

The simplest scheme of cable-stayed systems is a cable-stayed beam. It is typical for it that the guys in one or more places support the stiffening beam. At the same time, they themselves either radiate from the tops of the pylons, or resemble the outlines of a harp when they go parallel to each other.

Varieties of hanging systems

After the cable systems, let's look at the varieties of hanging systems:

• Single belt. They are performed over rooms of both round and rectangular shapes. The perception of the expansion of metal threads is provided by pylons, guys, extensions to the building, etc. The use of flexible threads or arches as intermediate supports is typical. The coating is stabilized with roofing reinforced concrete panels, embedding seams.
• Two-belt. In addition to load-bearing ropes, they also have stabilizing ones, which are connected to load-bearing stretch marks or spacers. Least of all, the disadvantages of hanging systems are detected 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 withskilled 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 of double or single curvature. They are distinguished from the background of other hanging structures by the fulfillment of the enclosing and bearing task. But the significant disadvantages of the membrane coating are low fire resistance due to the large surfaces of exposed metal, exposure to corrosion, as a result of which the minimum thickness of the steel sheet should be within 4-5 mm with an allowable 1-2 mm. The membranes can be cylindrical, circular, tent-shaped.

Let's move specifically to suspension and cable-stayed bridges.

Cable-stayed bridge

This variety is characterized by a special type of bearing systems - cable trusses, which are formed by stretched flexible rods (guys). Sometimes there are combined variations in which the lower parts of these trusses are replaced by stiffening beams. The work of the latter is aimed at bending, and the function is to support the platform of the roadway. The guys here are high-strength wire formed into bundles, or steel ropes.

Both cable trusses 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 support pressure is transferred to the anchors by a system of guy wires. If there is a stiffening beam, then the ends of the braces are fixed on it, which is why the system turns into an externally spaceless one. Roadway constructionis already attached to the nodes of the cable-stayed trusses.

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 facility was built in 1979 in Belgrade.

The first cable-stayed bridge on the territory of modern Russia is the Oktyabrsky across the Sheksna (Cherepovets) river. Its construction ended in 1979. In the Russian Federation there is also a cable-stayed structure-record holder. This is the Russian bridge in Vladivostok, blocking the Eastern Bosphorus. It is distinguished by the longest span - 1104 m (the total length is 1886 m), which is supported by two pylons.

Advantages and disadvantages of a cable-stayed bridge

Let's consider the pros and cons of such bridges. For a better understanding, we decided to present them to you in the form of a table below.

Dignity	Flaws
Light load-bearing structures	Reduced stiffness - only used as urban or road bridges
Overlapping capacity is large enough	In rare cases, it can be used as a railway bridge - only with a certain stiffening beam design
Material consumption is minimal, moreover, the purchase of expensive structures is not required
Possibility of surface mounting
Architectural aesthetics
Unlike hanging ones, they are more motionless

In conclusion, let's look at suspension bridges.

Suspension Bridge

Suspension (otherwise - suspension) bridge - a structure whose supporting main structure is flexible elements (ropes, chains, cables, etc.) operating in tension, and the roadway is in a suspended state. Such bridges are a real find in cases where a large coverage is required, and it is dangerous or impossible to install intermediate supports (for example, on a navigable river).

The load-bearing 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. A concentrated load allows the supporting structure to change its shape, which reduces the rigidity 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, and other peoples of Central and South America, Southeast Asia. Constructions of the modern type 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 Ekateringof park in St. Petersburg. One of the most famous domestic suspension bridges today can be called Krymsky 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 tablebelow.

Dignity	Flaws
Relatively little material is required to build a long main span	Insufficient rigidity - the bridge is dangerous to operate, for example, during a storm
Light dead weight of structure	For the reliability of pylon supports, a capital foundation is required
Bridges of this design can be built high above the water surface, which is very useful for navigable reservoirs	With a highly uneven load, the canvas of the suspension bridge tends to bend, which prevents its use as a railway
No intermediate supports required
Under the strong action of the elements or seismic loads, these bridges can bend without causing any damage to the structure as a whole

That's all we wanted to tell you about stays, stays, bridges. Suspended and cable-stayed roofs are easy to build, able to cover large spans, look harmonious, and provide scope for design solutions. However, they also have their drawbacks, which impose restrictions, for example, for building certain types of bridges.