Designs and types of bridges

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

Bridges are an integral attribute of almost every river, they help to overcome obstacles, thanks to them the distances become shorter, and getting from point "A" to point "B" is more comfortable and faster. With the advent of new materials and technologies, complex crossing designs are becoming a reality.

What is a bridge

Bridges are an extension of the road over an obstacle. Most often they are laid through a water barrier, but they can also connect the edges of a ravine or canal. In connection with the development of transport infrastructure, bridges are being built in megacities for movement over roads, forming large interchanges. The main details of their design are spans and supports.

Classification of bridge structures

Types of bridges can be qualified according to several criteria:

• by main purpose of use;
• constructive solution;
• building materials;
• depending on length;
• by service life;
• depending on how it works.

Since a man threw a tree from one side of the river to get to the other, a lot of time has passedand a lot of effort has been put into the construction of engineering structures. As a result, different types of bridge designs appeared. Let's take a closer look at them.

Beams

The materials for their construction are steel, its alloys, reinforced concrete, and the first material was wood. The main elements of the load-bearing structures of this type are beams, trusses, which transfer the load to the bridge foundation supports.

Beams and trusses are part of a separate structure called the span. The spans are split, cantilevered and continuous, depending on the scheme of connection with the supports. The first ones have two supports at each end, the continuous ones can have more supports, depending on the need, and at the cantilever bridge, the spans go beyond the anchor points, where they are connected to subsequent spans.

Arched

Steel, cast iron, reinforced concrete casting or blocks are used for their manufacture. The first materials for the construction of this type of bridges were stones, cobblestones or monolithic blocks composed of them.

The basis of the design is the arch (vault). The connection of several arches by a road or railroad track is an arch bridge. The roadbed can have two locations: above the structure or below it.

One of the varieties is a hybrid - an arch-cantilever bridge, where two semi-arches are connected at the top and resemble the letter "T". The arched structure can consist of one span, and then the main load falls on the extreme supports. If the bridgeconsists of several connected structures, then the load is distributed to all intermediate and extreme supports.

Suspension bridges

The main materials for construction in this case are steel, reinforced concrete. Structures are erected in places where it is impossible to install intermediate supports. The supporting element is pylons connected by cables. To keep the bridge in a stable condition, the pylons are mounted on opposite banks, a cable connection is pulled between them to the ground, where it is securely fixed. Vertical cables are attached to the stretched horizontal cables, also attaching chains that will support the bridge deck. Beams and trusses give rigidity to the canvas.

Cable-stayed bridges

Building materials - steel, reinforced concrete. As with suspended counterparts, their design involves pylons and cables. The difference is that the cable connection is the only one that connects the structure of the entire bridge, i.e. the cables are not attached to horizontally stretched carriers, but directly to the end supports, which makes the structure more rigid.

Pontoons

"Floating" crossings do not have a rigid frame and connection with the shore. Their design is assembled from separate sections with a movable joint. A variation of this type of bridges are floating crossings. Most often they are temporary structures that are used until ice is established on water barriers. They are dangerous during heavy seas on the water, make navigation difficult, and movement on them has restrictions for multi-ton trucks.

Metal bridges

Most modern bridges involve the use of metal in the load-bearing parts of structures. For quite a long time, a metal bridge was considered the most durable type of structure. Today, this material is an important, but not the only component of bridge connections.

Types of metal bridges:

• Arched structures.
• Span viaducts.
• Hanging, cable-stayed.
• Trestles with reinforced concrete supports, where the spans are assembled from metal joints.

Metal structures have the advantage of being easy to assemble, which is why almost all types of railway bridges are built from this material. The metal parts are manufactured industrially at the factory, and the size can be adjusted. Depending on the load capacity of the mechanisms with which the installation will be carried out, factory blanks of the future one-piece connection are formed.

It is possible to weld the structure from parts directly at the place of final assembly. And if earlier it was necessary to connect many parts of one span, now a crane with a lifting capacity of 3600 tons can easily transfer and hoist an all-metal span on supports.

Advantages of steel structures

Iron is rarely used as a bridge material due to its poor corrosion resistance. High-strength steel and itsconnections. Its excellent performance can be appreciated in projects such as cable-stayed bridges with huge spans. An example is the Moscow bridge across the Dnieper in Kyiv or the Obukhovsky bridge in St. Petersburg.

Metal structures with lattice trusses are widely used in the construction of railway bridges. The main advantage of these solutions is the efficiency in operation, the speed of construction and dismantling of individual parts, the relatively low cost of production, the ability to build structures in the shortest possible time on accessible sites and in any geographical area.

Wooden bridges

The first bridges in human history were built of wood. For a long time, these structures could not be used without appropriate repairs, constant preventive maintenance and replacement of individual parts and fixtures. This was associated with the difficulties of construction and the fragility of the material itself. The following types of wooden bridges are currently under construction:

1. Depending on the system - beam, strut.
2. Depending on the design - package buildings with spans, truss bridges.

Beam structure is the simplest, and therefore quickly assembled structure. The support beams are driven into the ground to a depth of 4 m. Attachments are laid on the upper ends of the piles with the help of steel pins, all the piles are connected into a single whole, and a canvas for movement is laid on top. When building a wooden bridge, it is important to create a strong interfacestructures with earth embankment at both ends, this is done so that the bridge is stable.

Now there is a trend to revive the construction of wooden bridges, which is associated with the advent of technology for the manufacture of glued beams, which are more resistant to aggressive environments, external torsion forces and more durable in operation, moreover, its length does not depend on the natural growth of a tree.

Poetics and practice

There are 93 water arteries in St. Petersburg, including rivers, channels, canals and almost 100 reservoirs. Unhindered communication between the islands and parts of the city is provided by bridges, of which there are about 800, of which 218 are for pedestrians. From the beginning of the construction of the city, the tradition of building bridges was laid, without which St. Petersburg is already unthinkable. They form part of its architecture, history, lore and culture.

Perhaps, in no other city in Russia are drawbridges used so actively as in St. Petersburg.

The symbol of the Northern capital is considered to be one of the oldest bridges - Palace. It was built according to the project of engineer Pshenitsky A. P. and connects the Admir alteysky Island with the Spit of Vasilyevsky Island. State-of-the-art machinery lifts the 700-ton central span structures for ship passage.

The longest drawbridge in St. Petersburg is named after Alexander Nevsky. Its length is 905.7 m, the central movable span is made of metal, the construction time of the structure is only 2 minutes.

Types of bridgesPetersburg include the entire history of bridge building - from the first wooden structures to modern multi-lane cable-stayed structures. Bolshoy Obukhovsky Bridge, for example, has a length of 2824 m, and today it is one of the longest engineering structures in Russia. It is made up of two parallel identical parts, along which a four-lane one-way traffic is organized.

Petersburg legends

Different types of bridges are presented in abundance in St. Petersburg, there are also old ones that have become symbols of a bygone era, but their purpose has not changed, although it has acquired a veil of stories and romance. So, the Kissing Bridge across the Moika River attracts tourists with its name, but it came from the name of the merchant Potseluev, whose drinking house "Kiss" was located next to the crossing, and the name has nothing to do with romantic impulses.

Interesting legends are overgrown with Liteiny Bridge, and the dramatic plot arose immediately upon its laying. It is believed that one of the foundation stones of the supports was the sacrificial stone Atakan. Now he makes passers-by feel sad and provokes suicides. To appease the "bloody" boulder, some townspeople throw coins from the bridge into the Neva and pour red wine. Also, many argue that the ghost of Lenin can be found on Liteiny.

Five longest bridges in Russia

Until the bridge across the Kerch Strait is built, the five large-scale crossings look like this:

• Russian bridge in Vladivostok. Building lengthis 3100 m, the opening took place in 2012. For the first time, its necessity was thought about in 1939, but carried out at the present stage.
• The bridge in Khabarovsk. Its length is 3891 m. It has two tiers. The lower one is open to rail traffic, and the upper one is open to automobile traffic. His image adorns the five thousandth bill.
• The bridge on the Yuribey River. It is located beyond the Arctic Circle in the Yamalo-Nenets Autonomous Okrug. The length of the structure is 2893 m.
• The bridge across the Amur Bay has a length of 5331 m. It was opened in 2012. It is interesting for its lighting system, which helps to save up to 50% of electricity.
• Presidential bridge across the Volga in Ulyanovsk. Its length is 5825 m. Construction was carried out for 23 years.