Wooden pedestrian bridges. The most remarkable wooden bridges in the world. Wooden arch bridge

The history of wooden bridge construction in our country has not yet been the subject of special study. Only the briefest mentions and simple listings of monuments in general works and popular essays devoted to the history of bridge construction in general and Russian wooden architecture. This article makes an attempt to systematize Russian wooden bridges of historically established and currently existing types.

Short story. The art of building bridges has been highly developed since ancient times. The main building material was pine due to the straightness and evenness of the trunk, good mechanical properties of the wood and resistance to decay, as well as its wide distribution. Ancient bridges, like other structures, were chopped and processed with an ax: grooves and sockets were cut out when connecting beams; even the manufacture of planks was carried out by splitting logs lengthwise into several pieces using wedges. Therefore, the chroniclers, speaking about buildings wooden buildings or structures, they used the word “cut down” instead of the word “build”: they cut down huts, mansions, bridges, etc.

The first mentions of bridges in Russian chronicles date back to the end of the 10th century. The improvement of the art of construction gave rise to the emergence of a special kind of specialist - builders of bridges and crossings, called “bridge builders”. The first bridges consisted of trees thrown from bank to bank; raft ferries were built on large rivers. Several interconnected rafts, on top of which a log flooring was laid, formed a “living” floating bridge. They were common on large rivers.

In 1115, under Vladimir Monomakh, a floating bridge across the Dnieper was built in Kyiv. Because floating bridges were quickly aimed and easily disassembled, they played a big role in military operations. There are two such bridges across the Volga, mentioned in reports of the siege of Tver under Dmitry Donskoy, and another bridge for crossing the Don during the battle with the Tatars in 1380. The first bridges in Moscow were “alive”: Moskvoretsky, Krymsky, etc. It should be noted that that floating bridges were widely used in Russia until late XIX V. The main reason for this was the significant width and depth of the rivers, as well as strong ice flow; under such conditions, floating bridges without permanent supports seemed to be the most appropriate, simple and inexpensive structures.

1. Moskvoretsky “live” - floating bridge. Engraving by Picard from the 17th century. (Photo library of GNIMA named after Shchusev)

2. Single-span bridge in Yeniseisk towards the 19th century.

3. Cantilever-beam bridge with an arched span on the river. This Arkhangelsk region. (photograph from 1920, Photo library of the Shchusev State National Research Institute)

Floating bridges could also be drawbridges; To allow ships to pass, one part of the bridge (the raft) was moved to the side. A 17th-century engraving by Picard gives an idea of ​​the floating Moskvoretsky drawbridge, which already existed in 1498. (Fig. 1) and a figurative description of Pavel Aleppo: “There are several bridges on the Moscow River, most of which is approved for wooden stilts. The bridge near the Kremlin, opposite the gate of the second city wall, arouses great surprise: it is level, made of large wooden beams, fitted one to the other and tied with thick ropes of linden bark, the ends of which are attached to the towers and to the opposite bank of the river. When the water rises, the bridge rises, because it is not supported by pillars, but consists of boards lying on the water, and when the water decreases, the bridge also lowers. When a ship with supplies for the palace arrives from the Kazan and Astrakhan regions... from Kolomna... to the bridges approved (on stilts), they lower its mast and guide the ship under one of the spans; when they approach the said bridge, then one of the connected parts is freed from the ropes and taken away from the ship’s path, and when it passes to the Kremlin side, then that part (of the bridge) is again brought to its place. There are always many ships docked here, bringing all kinds of supplies to Moscow... On this bridge there are shops where brisk trade takes place; there is a lot of traffic on it; we always go there for a walk...troops constantly move back and forth along it. All the city maids, servants and commoners come to this bridge to wash their clothes in the river, because the water here is high, level with the bridge.” The Moskvoretsky “living” bridge was located opposite the Water Gate of the Kitay-Gorod wall; in the second half of the 18th century. it was replaced with a wooden bridge on stilts.

Drawbridges were used in fortifications. The first chronicle indications of their structure date back to 1229: “...and the erection bridge and the zheravets vozhgosha...”, reports the Ipatiev Chronicle. The span adjacent to the city wall was made liftable and called an overhead bridge. The mechanism that set the bridge deck in motion consisted of a rocker arm rotating between the pillars (jeraves) and chains. In the 16th century The Kremlin bridges - Konstantino-Eleninsky, Spassky, Nikolsky - were connected to a sluice system that regulated the filling of the ditch with water from the Neglinnaya River, and had a wooden bridge customary for fortresses. lifting structure. In the 17th century Trinity Bridge had a lifting part.

Strengthening bridges. In the middle there are additional abutments. Below - the appropriate direction of the load using wheel guards (1 and 2) and reinforcement of the flooring (3 and 4).

The types of bridges described above are classified as movable bridges in their design. A fundamentally different type were permanent bridges. Depending on the number of supports on which they rested spans, they were distinguished as single-span or multi-span. Rowing bridges belong to the ancient type of single-span bridges; the first mention of them dates back to 977: in Vručia “rowing bridge”. Rowing took place in wide floodplains of rivers and was a semblance of dirt road. In the middle part, a slot was left for the construction of a single-span bridge, the abutments of which were log supports filled with earth and stone. It is likely that the rows could also consist of solid log buildings with a slot in the middle part. At the end of the 19th century. L. F. Nikolai, analyzing the drawings of wooden bridges measured on the Arkhangelsk Highway in 1795, came to the conclusion: “A similar method of crossing wide floodplains of rivers is still used today...”. The bridges of the late 19th - early 20th centuries had a similar design. in the city of Yeniseisk (Fig. 2) and on the river. This is in the Arkhangelsk region (Fig. 3). The successive protruding logs of the bank abutments formed an almost arched structure. To prevent the bridge from floating up during floods, cobblestones were laid along the edges of the deck.

In the case when several holes were left in the log house for the entire height of the fence, a multi-span bridge was obtained with supports in the form of cages or gorodny (Subsequently, such supports began to be called ryazhi or bulls). To ensure the required degree of immobility and non-floatability, log houses-gorodni were, as a rule, filled with stones. Purlins made of logs were laid on top of the gorodnya in the longitudinal direction, and in turn, a continuous ramp of logs was laid on them in the transverse direction - the flooring of the roadway. The carpenters were required to create strong support for a roadway that at the same time could withstand the rapid flow of water during spring floods. These tasks were complicated by the fact that the bridges reached significant sizes.

The people of Novgorod were famous for their skill as woodworkers. The famous Great Bridge across the river. Volkhov had supports in the form of towns and was built obliquely across the river (the width of Volkhov near Novgorod is about 250 m). Under 1133, the Novgorod First Chronicle reports: “In the same summer, the bridge across the Volkhovo was renewed and destroyed.” Since this date, chronicles have systematically reported damage to the city bridge by floods, storms, and ice drifts. There is a miniature from the Nikon Facial Chronicle of the 16th century, which depicts the Great Bridge, where the Strigolniks were executed in 1375.

Bridges, in addition to their main purpose - crossing over any obstacle, were used as street markets. There were benches on the Moskvoretsky Bridge, mentioned above. Resurrection Bridge on the river. Neglinke was a brick multi-span structure covered with a wooden pavement, and was built on both sides with two rows of chopped wooden trading benches. It was located at the Resurrection Gate of Kitay-Gorod and provided an exit from the city to Red Square near the current Historical Museum.

Stone-wooden bridges were logical in the system of defensive structures of the Kremlin. To prevent enemies from crossing the bridge, it was enough to dismantle or even burn the wooden decking of the bridge. Then he recovered easily.

Changes in the country's economy caused by the transformations of Peter I had a positive impact on the development of bridge construction. The construction of the capital at the mouth of the Neva required the construction of large quantity crossings in a relatively short time. The first bridge of the new city, built in 1705, was floating. Instead of rafts, barges were used there. Such bridges were built in St. Petersburg throughout the 18th and 19th centuries, the most notable of them being St. Isaac's. Simultaneously with the floating ones, permanent bridges on pile supports were built across the canals. It is interesting to note the fact that at this time wooden bridges were often built according to “samples”, i.e. standard standard drawings. By 1748, there were about 40 wooden bridges in St. Petersburg, about half of which had drawbridges. On the river In Fontanka, according to the design of V.V. Rastrelli, an aqueduct was built, which, using a special machine, supplied water to the fountains of the Summer Garden.

An outstanding achievement of Russian technical thought of the 18th century. was a project by I.P. Kulibin. It was proposed to block the Neva with a huge wooden arch with a span of 294 m.

The most important and complex engineering structure among bridges are dam bridges, which are functionally connected to an entire system of hydraulic structures. From the end of the 17th century. the construction of waterways of national importance began, such as the Vyshne-Volotsk, Tikhvin, and Mariinsk systems. All hydraulic structures of these systems were wooden. The Vytegorsk Museum of Local Lore preserves views of the dams and bridges of the Mariinsky system. The St. Paul Dam (at the same time it served as a bridge), located on the river. Vytegra near the village. Devyatina, had a red-colored stepped drain, the difference in heights of the pool marks (the pool is a section of the river between two neighboring dams on the river) was 8.5 m. The Anninsky swing bridge on the river was of significant interest. Kovzha, it existed from 1810 to 1896. The middle support of the bridge had a rotating mechanism that could rotate along with the bridge spans by 90°, allowing oncoming ships free passage on both sides. In the city of Vytegra, there was a drawbridge on the connecting canal until 1961. It was built on pile supports. The middle part of the bridge had two lifting spans of different sizes. With the introduction of the Volga-Baltic waterway, the Mariinsky system was reconstructed with the replacement of wooden hydraulic structures with concrete ones.

Widespread construction of highways and then railways in the 19th century. led to the rise of bridge construction. A wide variety of structural systems of span structures appeared: braced, arched, trusses, etc. Issues of engineering construction in Russia of this period are beyond the scope of this article and deserve special consideration. With the introduction of new building materials (cast iron, concrete, steel, etc.), wooden bridges are gradually being replaced, and then in the central part of the USSR they almost completely disappear.

Modern timber bridge construction. In the North of the USSR, wooden bridge construction received the most striking and multifaceted development. The stability of northern life contributed to the transfer from generation to generation of the construction skills of folk architects, which is why examples of wooden bridges have been preserved here to this day. various types. What are the types of bridges that have survived and are currently under construction, what are their technical and design features?

Wooden bridges experience great physical and atmospheric influences, therefore, more often than other structures, they are subject to overhaul or replacement of individual parts, but at the same time, the original forms and structural basis remain the same, formed from the river regime and operating conditions. Thanks to these features, bridges, unlike other structures, retain their original shapes, which date back to ancient times.

Most in a simple way The connections between the banks are ferry crossings. They are used with low traffic intensity. A raft, or pontoon, ferry moves manually along a rope thrown from bank to bank along the river bottom or over the water. For example, in the Arkhangelsk region, on the Onega and Moshe rivers, ancient ferry crossings have been preserved, which are currently in use. In cases where the construction of a bridge on permanent supports is expensive and cannot be justified by the cargo turnover, floating bridges are used. When the water horizon is high, all the rafts of such a bridge are afloat; when the water horizon is low, some of the rafts near the shore rest on the river bottom. With the onset of winter, these raft bridges have to be dismantled and put into backwaters, protected from floods and ice drift. In this case, communication between the shores in the winter occurs over ice. In Kargopol across the river. A pontoon bridge was thrown across Onega. In more remote areas, raft floating bridges have been preserved - in the village. Korovino on the river Kene and village Ust-Pocha in the Plesetsk district of the Arkhangelsk region.

4. Bridges in the village. Purnema, Arkhangelsk region. a - new bridge (1969), the solid structure of the bridge is not extended to the slope of the ravine; b - the ancient bridge (1927) has a solid log structure with logs laid “in the dir”

5. Cantilever-beam single-span bridge made of timber in the village. Gridino, Karelia

6. An ancient bridge with supports made of rectangular logs in the village of Verkhovskaya, Komi Republic (Photo by I. N. Shurgin)

7. Bridge with two triangular log houses in the village. Stupino Arch. region

Narrow obstacles, such as ravines and rivers, are covered by solid bridges. They consist of end-to-end rows of log buildings (ryazhevoy log house), connected in the transverse direction by the same rows of logs, forming monolithic structure. This design, for example, has been preserved in the Arkhangelsk region on Kenozero in the village of Tarasovo. Ancient bridge in the village. Purnema in the Arkhangelsk region (Fig. 4, b) is built through a deep ravine (8 m); its flooring lies on a solid timber frame, filling the ditch to the very bottom. This method of cutting “in the dir” (It is necessary to distinguish the concept of a ryazhe log house or a ryazhe support from the felling “in the dir.” Ryazh is the accepted name for the construction of a bridge support. “Rezh” is a method of laying logs with gaps) protects the bridge from rotting and allows free miss spring waters. A hole is left in the middle part for free passage of water. The bridge has already fallen into disrepair, its edges have settled, since the bank of the slope is sandy. In 1969, next to the old bridge, a new one was built, similar in design, but the ryazhe frame was not completed to the end of the ditch (Fig. 4, a). The new wooden bridge is also of significant interest.

The most common type of bridge for small rivers is single-span beam bridges, such as in Ust-Tsilma of the Komi Autonomous Soviet Socialist Republic. To increase the span between supports, a cantilever-beam structure is used - successively protruding logs of coastal abutments. Such a bridge in the village. Gridino of the Karelian Autonomous Soviet Socialist Republic (Fig. 5) was built across a stormy, rocky river, its foundations are littered with boulders.

On wider rivers, multi-span bridges are built; this is achieved by introducing intermediate supports: piles, ryazhevyh. For rocky or muddy soil, ridge supports with different shape log houses: three-, four-, five-sided and more complex.

Simple and more ancient supports are rectangular log houses. In the Komi ASSR, in the village of Verkhovskaya (Ust-Tsilmsky district), a bridge was built across the Domashny stream (Fig. 6), the flooring of which, without a fence, lies on four rectangular bull cages. The logs of the log houses are processed with an ax, laid “in the cut” and have large outlets.

In the Arkhangelsk region, in the village of Stupino (Nyandoma district), in 1967 a bridge was measured, the intermediate abutments of which have a triangular shape (Fig. 7), and the frame of the bulls is placed at an angle towards the river flow.

On rivers with ice drift, pentagonal-shaped ridges are arranged. A triangular appendage is cut into the rectangular frame of the bull, acting as an ice cutter. Wooden bridges with this type of frame are the most widespread and can reach significant sizes. In the village Shueretskoe Karelian Autonomous Soviet Socialist Republic (Fig. 8) the bridge has eleven bulls, and its length is 150 m. In the village. Ryagovo (Kargopolye) with a bridge length of more than 100 m, the height of the ridge reaches 8 m (Fig. 9). (Today, a new concrete bridge has been built nearby.)

As a rule, ryazhe bridges have the original foundation of log houses, since wood survives in water for centuries. When replacing or rebuilding the top of the supports, their shapes are repeated. There are many similar bridges in the Arkhangelsk region in the direction Krechetovo-Kargopol-Oshevensk on the rivers Ukhta, Tikhmanga, Lekshma, Churiega. With identical design solutions, each of them has its own unique architectural artistic image(Fig. 10).

8. The longest surviving wooden bridge (150 m) in the village. Shueretskoye, Karelia

9. Ryazhevoy bull of the bridge in the village. Ryagovo reaches a height of 8 m. (Arch. region)

North of Oshevensk, in the place where the river. Churiega flows into the river. Ken, in the 15th century. The Kenoretsky monastery was founded, which reached its heyday at the end of the 17th - beginning of the 18th century. Large land acquisitions on both sides of the river date back to this time. Kens. In 1764 the monastery was abolished, and in 1800 a fire destroyed its buildings. The only witnesses of that time are two ryazhe bridges: in the village of Leshino (now the village of Kenoretskaya) (Fig. 11) and three kilometers downstream of the river, in the village of Pelyugino.

According to the ancient Russian tradition, at the entrance to the Pelyuginsky Bridge, on the elevated bank, there was a chapel on the basement, with a tented belfry above the entrance, surrounded by a gallery (now transported to the Arkhangelsk Museum wooden architecture"Little Karelians")

Back in 1946, an expedition from the Institute of History and Theory of Architecture of the USSR Academy of Architecture explored Kargopolye. One of the most important results of her work was the measurements of the Ken bridges made by A.V. Opolovnikov. In 1982, the author of the article carried out repeated surveys and measurements, which showed that, despite the almost complete replacement of building materials, the shape and design of the bridges had not changed. Honed over centuries, these forms have proven to be very stable.

The structural basis of Ken bridges is the same. The five-span bridge near the village of Leshino has a length of 114 m, the four-span bridge near the village of Pelyugino has a length of 84 m. Their design is unique, each middle ridge consists of a rectangular frame with triangular and trapezoidal cuts protruding from its lower part; so that the entire outline of the plan resembles the shape of a boat. The bottom here is rocky, the river flow is very fast, so the frame of the ryazh is littered with boulders. To eliminate the resulting thrust and to uniformly fill the bull with boulders in the transverse and longitudinal directions at different levels, the log houses have ligated crowns, forming a system of internal triangular “pockets.” The upper tetrahedral base of the bull forms rolls on the log outlets, which makes it possible to increase the spans to 15 m.

12. Ryazhevoy bridge with a triangular shape on the river. Keme (Vologda region) Combination folk traditions and engineering techniques (Photo Sevan O. G.)

Unlike civil structures Bridges do not have a shell - walls, ceilings that hide the supporting structure. Therefore, the structural system of the bridges remains open and forms the basis of the architectural composition. Bridges are rarely subjected to artistic treatment; their architectural expressiveness is achieved by the boldness of constructive solutions, the originality of spatial composition and various techniques wood processing. The most interesting engineering and architectural structure is the bridge across the river. Kema in the Vytegorsky district of the Vologda region. Its distinctive feature - a triangular log truss - significantly enriches the volumetric composition: it is arranged “in space” in the deeper part of the river, which allows increasing the span length (Fig. 12). Another example is the bridge in the village. Umba, Murmansk region. Its bright artistic expressiveness is achieved by the log struts of the spans and the X-shaped frame of the bridge handrails (Fig. 13).

Any wooden bridge, having its own special artistic image, is also part of environment: landscape or residential development. In the Oshevensky complex of villages located along the Churiega and Khaluy rivers, wooden bridges are important element planning structure and together with unique religious, residential and outbuildings form a harmonious whole.

The city of Belomorsk (formerly the village of Soroka) can be considered a kind of “reserve” of wooden bridges. The old part of the city is built of wood and does not have unique architectural monuments, but nature itself has made it unusually picturesque. When it flows into the White Sea, the Vyg River overcomes many rapids and, spilling over several kilometers, forms about forty islands, on which the village of Soroka was once located. In these natural conditions, bridges became a necessary element of intracity communication. In the relatively small old territory of the city there are about twenty of them (Fig. 14). Unfortunately, several bridges have been lost; the longest among them (more than 300 m) was replaced with a concrete one. But all the existing bridges, merging with the space of the river, and the buildings along with the rapids created a unique image of this city.

The idea of ​​wooden bridge construction at the present time would be incomplete without noting some surviving types of purely “engineering” bridges, among which beam bridges with pile supports of various combinations with frame and brace systems are the most widely used. Multi-span beam bridge on the river. Tartas in the Novosibirsk region (50s of the XX century) has a two- and four-row system of pile supports (Fig. 15). In the transverse direction, the pillars of the support frame have diagonal contractions, and the entire structure of the supports is secured with steel bolts and pins. Purlins are laid on the supports, and in turn, the roadway deck is laid on them. The length of the bridge is 66 m. Ice cutters 11 m long are installed in front of the middle supports.

An important component of a bridge with piles and frame supports are wooden ice cutters. To protect supports and spans from shocks when struck by ice floes, ice cutters are not connected to the bridge supports. Narrow supports are protected by flat ice cutters having one or two rows of piles. For wide supports, tent ice cutters are used, consisting of several rows of piles. Ice floes approaching the ice cutter, under the influence of inertial forces and water pressure, rise along it and break under the influence of their own weight.

There are still wooden bridges with trusses, which were widely used since the mid-19th century. Gau-Zhuravsky truss spans are the most common design of wooden bridges. This bridge was built in 1967 on the river. Moshe in the Arkhangelsk region (Fig. 16). The channel spans of the bridge are blocked by spans with trusses with a ride on the bottom (design span 31.5 m). The outer spans are covered with spans of a simple beam system with two-tier purlins. The length of the bridge is 146 m. ​​The channel pile supports are protected by free-standing tent ice cutters.

Another type is bridges with a braced system. In the Plesetsk district of the Arkhangelsk region there is a wooden overpass (a bridge designed to pass one road over another), built in 1939 on the Plesetsk-Kargopol highway, which passes over the local railway, forming an oblique intersection of 42°. The three-span bridge has frame supports on a support base (Fig. 17). The two middle supports are completed with a combined braced system, which made it possible to create a middle span. The design of the overpass is typical for bridge structures of the 19th - early 20th centuries. and now practically never occurs. Although the bridge is in good condition, it is in danger of being destroyed.

Currently, there is another type of single-span bridges - suspension bridges, found in the Arkhangelsk region. The bridge in the village of Papinskaya, Konosha district (Fig. 18) has the following structure: on both banks of the river there are two log houses with passage gates at the upper level, metal cables are stretched along the top and bottom of the openings of the log house, secured to the ground with metal crutches. Along the entire length of the bridge, the upper and lower cables are connected to each other by wooden blocks (acting as hangers); wooden flooring is laid on the lower cables. On both sides of the log houses there are boardwalks. On the river Emtse in the village. Emtsa, Arkhangelsk region, the suspension bridge of the hydrometeorological service was built in 1928 (see side 4 of the cover). The simple design creates a beautiful silhouette against the background of the river, giving lightness to the entire structure. Suspension bridges, widely used since the mid-19th century, are now rare.

Wooden engineering bridges were the predecessors of steel and concrete structures and played a certain historical role in their time. It seemed that with the development of professional engineering bridge construction, with the introduction of various new structural systems - strutted, arched, suspended, etc. - they were supposed to finally replace the ryazhe, folk bridges, displace them. However, this did not happen.

Folk wooden bridges, having a long history, are examples of the stability of architectural form, which have been precisely worked out by many generations of builders, carpenters, and folk architects.

In our age of technological progress, the widespread replacement of wooden bridges with modern steel and concrete ones leads to the disappearance in some places of this type of structure. At the same time, in the North of the USSR and in Siberia, where wood is the main building material, wooden bridges continue to be built, especially since wood is a cheap building material that can be quickly harvested and processed, allowing construction to be carried out in the shortest possible time. Wooden bridge structures, reflecting the ancient culture of the Russian people, connect times and generations; They still have practical significance today and are a most valuable contribution to the cultural heritage of our Motherland.

8. Laskovsky F. F. Materials for the history of engineering art in Russia. St. Petersburg, 1858. Part 1.

9. Novgorod first chronicle of the older and younger editions of M.; L., 1950.

10. Punin A.L. The Tale of Leningrad Bridges. L., 1971.

11. Zabella S. Kargopol expedition. - In the book: Architectural heritage. M., 1955, No. 5.

The advantages of wooden bridges are the speed of construction at any time of the year and the low construction (initial) cost, especially for bridges of small spans, which is significantly lower than for bridges made of other materials.

Specified positive traits wooden bridges give them a significant advantage over bridges made of other materials in heavily forested areas where wood is a local material, as well as in conditions where the rapid construction of a temporary crossing is necessary, etc.

The disadvantages of wooden bridges include higher maintenance and repair costs than bridges made of other materials, susceptibility to rotting and combustibility.

The cost of annual maintenance and repair of wooden bridges averages 2.5% of their original construction cost, which is 2-3 times higher than the cost of maintaining steel bridges and 8-10 times higher than the cost of maintaining stone and reinforced concrete bridges.

Rotting is the main factor limiting the life of wooden bridges. For bridges made of unimpregnated wood, not protected from direct moisture, this period is 8-12 years, and for bridges made of damp forest He

sometimes decreases to 5-6 years; in the far north, bridges built from larch last much longer.

Along with this, there are (see Introduction) examples of the great durability of covered wooden bridges (across the rivers Meta, Pskova, Pakhra, etc.). They owe their durability to the use of a constructive method of protection against rot, common in bridges of the past, by installing a roof and side cladding that protect the bridges from direct moisture from precipitation. A slight increase in the weight and cost of the span structure due to the installation of the roof and side cladding, amounting to approximately 10-12% (for mid-span trusses with a ride below), is compensated by an increase in the reliability and service life of the bridge.

In road bridges with a ride on top, the role of the roof can be played by a waterproof roadway with sidewalks on cantilevers that protect the outer trusses from slanting rain. At. The high height of the span and the small overhang of the consoles require, in addition, the installation of side cladding.

By using antiseptic coatings in such bridges to protect against condensation moisture, which, when assembling the structure, cover all bonded surfaces of the elements, nodal joints, etc., it is possible to radically protect the bridge structure from rotting and ensure any (according to the conditions of economic and obsolescence) service life of the bridge, bringing it, if necessary, to 40-60 years. Similar methods of protection against rotting can be applied without violating architectural requirements in bridges of a combined system with a ride below or in the middle.

In cases where the described structural methods of protection turn out to be impractical due to the conditions of saving material or for reasons of structural and production order, for example, in through-beam trusses with a ride at the bottom and upper lattice connections, chemical measures should be used to combat rotting by deep impregnation of all parts with oily antiseptics wooden elements span structure, which (according to the experience of bridge construction in the USA) ensures a service life of 30-35 years, even in unfavorable conditions.

The fire hazard in road bridges when driving on the top and fireproof surface of the roadway is insignificant. In railway bridges with locomotive traction, this danger is greater; however, here too, the construction of a roadway with a ballast trough and the use of protective measures against wood fire almost exclude fire danger wooden bridges constructed from massive beams.

The spans of modern girder railway and road wooden bridges are usually limited to 40-60 m.

Wooden structures are widely used in the construction of overpasses on approaches to bridges, industrial enterprises(for transporting sand, limestone, ore, coal, etc.), in the form of pedestrian bridges, etc.

Overpasses that have a roof and walls are called galleries; if necessary, they are arranged insulated. Overpasses and galleries can be horizontal or inclined; in their design they are similar to bridges.

Brief historical sketch of the development of wooden bridges

Wood has long been used in the construction of bridges. In terms of distribution on earth and duration of human use, only stone competes with wood.

Bridges made of wood were built back in ancient Rome, Greece and other countries. One of the oldest is the bridge across the river. Euphrates in Babylon (1200-625 BC). The Italian builder Palladio made a significant contribution to the development of wooden bridge construction. He proposed spregel and transom-braced systems for bridges, as well as lattice trusses with parallel chords, posts and braces, which have survived to this day.

At the end of the 18th century. and the beginning of the 19th century. In the construction of wooden bridges, the arch system began to be used. In the middle of the 19th century. American engineer Town proposed and built wooden spans in the form of lattice trusses made of boards.

In the second half of the 19th century. and at the beginning of the 20th century. metal and then reinforced concrete began to be used more widely.

Intensive construction of wooden bridges in Russia began under Peter I in St. Petersburg. Bridges were built using beam and arch systems on pile and stone supports, as well as floating bridges.

At the beginning of the 19th century. in Russia they began to use Gau system farms. Russian engineer D.I. Zhuravsky developed a method for their calculation.

In the second half of the 19th century. Intensive construction of metal bridges began in Russia.

Wooden bridges became widespread after the October Socialist Revolution on highways.

In the post-war period, reinforced concrete became more widespread in the construction of new bridges.

In the modern period, wooden bridges are practically never built on highways. But they have applications as temporary bridges and can be built on local roads in forest-rich areas. According to statistics, 1% of wooden bridges are used in Ukraine.

Main features of wooden bridges

Wood is used as a building material for bridges thanks to his wide distribution, low volumetric weight and ease of processing.

Along with its advantages, wood also has flaws - susceptible rotting, as a result of which wooden bridges quickly fail. The service life of a wooden bridge is 8–10 years, unless special measures are taken to prevent decay. Parts of the bridge that are located in conditions of variable humidity rot after 5 - 7 years.

The disadvantage of wood is dependence of wood resistance to forces on their direction relative to the fibers. This makes it difficult to connect elements and does not make it possible to use the material with the greatest strength.

Characteristic feature wood is heterogeneity. The strength characteristics of wood depend on which part of the cross section and at which height of the trunk the sample was taken, influence wood defects: knotty, cross-layered, etc.

The disadvantages of wood include: reduction in size upon drying. Shrinkage and weak resistance to crushing across the fibers lead to collapse of the notches and breakdown of the joints. Therefore, careful observations during operation and appropriate maintenance and repair costs.

Wooden bridges dangerous in terms of fire.

Wood rotting is not a natural aging process of the material, but a disease caused by fungi. In conditions that exclude the activity of fungi, wood can be preserved for more than a thousand years.

The search for ways to increase the service life of wooden bridges is using structural and chemical wood protection products. Constructive way - this is a transition to cutless structures and mechanical protection bridge elements from atmospheric influences canopies, awnings, etc. Chemical method – antiseptic treatment of wood with substances that kill fungi. Antiseptic treatment allows you to increase the service life of the bridge by 2-3 times (up to 30 years, and when using glued and glued plywood structures up to 40 years and more). But it should be noted that antiseptics are expensive.

Wood is undoubtedly the oldest and most widely used material for bridge construction in previous centuries. However, in the 20th century, steel and reinforced concrete almost forced it out of this area. And while in other countries old bridges have been preserved thanks to the protection of their structures, in Russia almost all of them have been lost.

Wood is now returning to bridge construction in the form of modern designs. Russia, unfortunately, is almost not involved in this process yet, but our specialists have the opportunity to study other people’s experience and take the best from it.

This review, using the example of several of the most remarkable, in the author's opinion, objects in different countries, traces the history of the development of wooden bridge construction from the oldest (surviving) bridge on wooden trusses to modern road bridges made of laminated timber structures. The review presents only existing or planned bridges.

Kapellbrücke Bridge, Switzerland, 1365

This bridge, whose name translates from German as “Chapel Bridge,” is the oldest in Europe and also the oldest timber truss bridge in the world. In 1993, he survived a fire. Its total length is 275 m, the maximum span is 15 meters.

The transition from beams to wooden trusses allowed bridge builders to increase the free spans of bridges - now they were not limited by the size of the original logs and beams. In Switzerland, the database of wooden bridges lists 1,055 in operation, many of them built in the 15th-19th centuries. Vehicles are generally prohibited from crossing these bridges, but they are still used by pedestrians and cyclists. Such durability of ancient Swiss bridges is due to the fact that they were built covered.

Currently, to prevent rotting of wooden structures, deep impregnation of wood with bioprotective compounds, protection of structures with steel sheets (on top) and cladding boards (on the side), and combination of wooden structures with a concrete slab, the overhangs of which protect the wooden elements from precipitation, are used.

Keystone Wye Interchange, USA, 1968

Laminated timber has been used for bridge construction in North America since the second half of the 1940s, when industrial scale production was established moisture-resistant adhesives. However, the real breakthrough came in 1966-1967, when laminated timber structures were used to build a three-level interchange on Interstates 16 and 16A in South Dakota. The object consists of two bridges located one above the other. The upper bridge, supported by three glued arches, has a span length of 47 m, even today this value is impressive if you remember that the bridge is a road bridge! Each arch is made of two semi-arches connected by a hinge at the apex.

The Keystone Wye Bridges became a symbol of wood bridge construction in the United States for many years. Since then, quite a few have been built in the United States big number bridges made of laminated timber structures. In 1989, the US Senate approved the Timber Bridge Initiative, which sought to encourage the use of wood in forested regions as a local building material for transportation infrastructure. This decision marked the beginning of a large-scale national program that funded the development of economical designs and methods for constructing bridges made of wood, and the construction of experimental and demonstration bridges.

Thus, design solutions have been developed for bridges on forest roads. Small spans, short service life, low traffic intensity - all this makes it possible to simplify the design and make it inexpensive. The span in this case can consist only of a self-supporting fabric, made by tightening boards placed on the edge (stress-laminated deck). Metal studs also perform a reinforcing function. The slab is assembled in a factory. To increase the service life of the structure, pressure-impregnated lumber is used. Since these structures have proven themselves well in operation, the scope of their application has been expanded and bridges with self-supporting decks are used today on public roads. To increase the load-bearing capacity of the slabs, they began to make them not from boards, but from glued beams (stress-laminated glulam deck). Moreover, as it turned out, it is advisable to tighten the elements into a slab not of a massive cross-section, but of a box-shaped or T-shaped one. Slabs of the latter type are used to cover spans 25-30 m long. Currently, this solution is widely used in other countries.

It should be noted that there are now about 48 thousand wooden bridges in the United States and almost the same number of bridges with wooden slabs laid on steel beams.

Vihantasalmi Bridge, Finland, 1999

The local authorities were prompted to build a wooden bridge across the Vihantasalmi Strait by the desire to emphasize the picturesqueness of the place and the close connection of the area with the woodworking industry. The bridge spans have a length of 21 + 42 + 42 + 42 + 21 m. The length of the middle spans is twice that maximum length spans of all bridges built in Finland before. The width of the roadway is 11 m, the width of the sidewalk and bicycle path is 3 m. As a result, this bridge has the largest road surface area among wooden road bridges. The distance from the water surface to the highest point of the bridge (the top of the wooden truss) is 31 m - this is almost the height of an 11-story building!

The 1050 m 3 laminated timber structures were manufactured by Vierumäen Teollisuus (currently Versowood Group).

This project was a real breakthrough in wooden bridge construction, since during its implementation solutions were developed and tested, thanks to which it is possible to build highway bridges with large spans today. First of all, it is a combination of laminated wood, steel and concrete in one structure; Such technologies are now commonly called hybrid. The three middle spans are covered with triangular laminated timber trusses, the two outer ones - with laminated timber beams. These structures are reinforced with transverse metal trusses, which gives them additional rigidity. In addition, the wooden elements are connected through inclined hooked pins glued into them with a monolithic reinforced concrete covering slab. Thus, elements from three construction materials work as one. All wooden elements are deeply impregnated with antiseptics.

Norwegian laminated timber bridges, 2001-2012

If we rank wooden road bridges by span and total length, the first three places will belong to bridges from Norway. Several more bridges from this country will be included in the top 15. In Norway, they believe that architecture, firstly, should reflect national culture and identity, and secondly, be based on the principle of harmony with the natural environment.

In 2001, over the river. Glomma built a bridge in the town of Tynset that broke the world record for the longest span of a wooden road bridge. The length of the main span, stretching over the river, is 70 m, the other two are 26.5 m each, the total length is 125 m. The bridge has two lanes for vehicle traffic and one for pedestrians and cyclists. The roadbed is a slab of planks fastened with metal pins, suspended on cables through steel beams under load-bearing structures made of laminated wood. As these load-bearing structures arches were installed for small spans; Arched trusses were used for the main span. The cross-section of the elements of the upper and lower chords of the truss is 700 x 600 and 700 x 560 mm, they are obtained by gluing bent-glued blanks, all diagonal elements consist of two beams with a cross-section of 240 x 400 mm each. The truss elements are assembled using splined (hidden) connections on metal plates. For rigidity under wind loads, the upper chords of the trusses are connected by horizontal struts. According to the Norwegian forestry institute NTI, double impregnation was used to protect the wood of the main structures: first, the lumber was impregnated with water-soluble antiseptics, and then the finished elements were impregnated with creosote, which was also impregnated with the wood of the slab. In addition, the upper chords of the trusses and the laminated arches of other spans are sheathed on top with copper sheets. For the construction of the bridge, about 400 m 3 of glued elements, 200 m 3 of lumber for the road surface slab and 95 tons of steel were used.

In 2003, another bridge was opened over the same river in the city of Flisa, the parameters of which exceeded the record bridge in the city of Tynset. The maximum span of this bridge is 70.3 m, and the total length is 197 m. The bridge in Flies is today considered the longest-span wooden road bridge in the world. The main design solutions used for the construction of this bridge are similar to those used in the construction of the Tyunsetsky Bridge: the roadbed made of lumber tied together with pins (48 x 223 mm) is suspended under glued trusses, deep impregnation of wood for glued elements with a water-soluble antiseptic (chromium copper arsenate) and surface impregnation of finished elements with creosote. In total, the bridge required 900 m 3 of laminated wood and lumber and 200 tons of steel.

In 2012, the Tretten road bridge with a maximum span of 70.2 m was opened. Today it is the second longest wooden road bridge in the world; Tyunset Bridge is in third place. The Tretten Bridge was designed in accordance with the requirements of the Eurocode - a pan-European set of norms and regulations.

But perhaps these three bridges will soon be left far behind technical specifications another Norwegian bridge is across Lake Mjøsa. This project is currently undergoing approval. The preliminary concept suggests that the total length of the bridge with four middle spans of 120 m each will be 1650 m. These four spans will be cable-stayed, that is, a span structure that is a hybrid structure of laminated timber trusses and a monolithic reinforced concrete slab roadway, will be connected by cables to five pylons. The height of the trusses will reach 6.8 m, and the cross-section of the wooden elements will be 1100 x 1100 mm. Thus, everything will be embodied in the design Hi-tech wooden bridge construction: gluing glued beams into large elements and then connecting them into a truss; hybridization of wood with monolithic reinforced concrete; cable-stayed structures. Wooden part the structure will be completely hidden under the concrete, which will probably make it possible to avoid treating wooden structures with creosote and limit ourselves to deep impregnation with a water-soluble antiseptic, because in Norway, as in other countries, they are trying to abandon the use of creosote for impregnating wood.

Speaking about Norwegian wooden bridges, one cannot fail to mention the famous Leonardo da Vinci Bridge, built in 2001 across a highway in the Norwegian province of Askerhus, 20 km from Oslo. This pedestrian bridge is distinguished by its incredible plasticity of shape. The artist Vebjorn Sand was inspired by a sketch of the bridge created by Leonardo da Vinci in 1502. Modern version The bridge is made of laminated timber structures, not stone, its length is 109 m, and not 240 m, as in the project of the famous Florentine. The main structure of the bridge consists of three arches with spans ranging from 45 to 55 m in length, with the outer spans installed at an angle. The cross section of the arches is not rectangular. To achieve the desired aesthetic effect, elements of increased cross-section, obtained by gluing bent-glued blanks, are processed on a CNC milling machine. Arches are obtained by joining these elements at the construction site. The road surface slab is made of bent-laminated beams held together by steel rods. Wooden structures are protected from external influences by painting, as well as by lining horizontal surfaces with metal sheets.

All wooden elements were manufactured at the enterprise of the Norwegian woodworking concern Moelven. The total cost of the project was 12 million Norwegian kroner (about $1.33 million at the exchange rate at the time of construction).

It is curious that in terms of the total number of wooden bridges - about 200 - Norway is noticeably inferior to its neighbors - Finland and Sweden, whose road infrastructure includes more than 800 wooden bridges.

Bridges in Lohmar, Germany, 2013-2014

A road bridge across the river was built in 2014. The Agger in North Rhine-Westphalia may be the calling card of the Miebach engineering office and the Schaffitzel Holzindustrie timber construction factory. The bridges designed and built by this tandem of companies almost always use elements of increased cross-section, obtained by gluing together conventional laminated elements, so-called blocklaminated wood. The production and processing of such elements is an extremely labor-intensive process, which also imposes special requirements on equipment, adhesive materials and personnel qualifications. In the DCC industry, only a few companies in Germany and Norway work in this direction. However, such elements are most promising for the construction of wooden bridges.

When constructing road bridges, Miebach and Schaffitzel use the hybridization of wooden elements with a road surface made of monolithic reinforced concrete, which is also a global trend in wooden bridge construction.

The total length of the bridge in Lohmar is 40 m, width - 4.75 m (including a 3 m car lane). The length of the main span is 28 m. The span is a hybrid structure of two symmetrical glulam beams of variable non-rectangular cross-section and a monolithic slab of white reinforced concrete. There is free space between the beams for communications. The fences are made of stainless steel, the handrails are made of acetylated wood, the so-called accoya.

The consumption of basic materials for the construction of the bridge was: GL32c class laminated spruce wood - 112 m3, accoya wood - 1.8 m3, concrete - 66 m3.

In Lohmar, in 2013, the Miebach and Schaffitzel companies built a picturesque cable-stayed pedestrian bridge with an S-shaped road surface. The total length of the bridge is 62 m, width - 2 m. The bridge structure is a block-bent laminated element suspended by cables on two pylons. To make it, bent-glued beams were glued into large elements, and fencing, brackets for cables and protective larch cladding were mounted on them. On site, the finished sections were connected into an S-shaped structure.
White granite slabs were used as flooring. The railings are made of accoya.

Bridge in Anaklia, Georgia, 2012

This is the longest wooden bridge in Europe, its total length is 540 m, the length of the maximum span is 84 m. The span structure is a spatial truss made of glued wooden elements, suspended in two spans by cables on a triangular frame. The consumption of laminated wood was 650 m3. Manufacturer: German company Hess Timber. Due to transportation to long distance the elements were manufactured to a length of no more than 13.5 m. They were joined on site using Hess Timber's patented method: gluing on jagged tenons with the addition of a hidden overlay of defect-free wood at the joint.

Bridge in Rheinfelden, Germany/Switzerland, 2018

What kind of free span can a pedestrian wooden bridge even have? Currently, in Europe and North America, the span length does not exceed 85 m, while the world record holder with a result of 141 m is the Maramataha bicycle suspension bridge in New Zealand (however, it is incorrect to compare this light narrow bridge with city pedestrian bridges). But next year the record will be 180 m - this is exactly the span that the suspended pedestrian bridge across the river will have. Rhine, which is being built according to the design of the German engineering bureau Miebach.. This bridge should connect two cities with the same name Rheinfelden - one in Germany, in the state of Baden-Württemberg, the other in Switzerland, in the canton of Aargau. The project is financed from the budgets of both regions. The total length of the bridge is 213.5 m, width 4.5 m. The span consists of a pair of connected block-laminated beams suspended on cables between curved steel “slingshots” 30 meters high. The wooden structure will be protected by sheathing. The handrails will be made from accoya. Paving is assumed to be white granite slabs. According to calculations, about 550 tons of CO 2 will be conserved in the wooden structure of the bridge.

So, wooden bridge construction is actively developing abroad. Moreover, as a rule, wooden structures are more expensive than steel and reinforced concrete for bridges with the same span length. The main motivation for choosing timber for local authorities and communities is the desire to create an aesthetically pleasing environment. For the same reasons, they are trying to add observation towers, lanterns and even power line supports made of laminated wood to the landscape. But at the same time, modern wooden structures are considered in bridge construction as... a durable alternative to steel and concrete. Thus, inspections of road bridges with steel and concrete structures in Norway, in many cases, their premature wear was revealed, which forced us to reconsider our ideas about the most durable material for the construction of bridges. Steel rusts, reinforced concrete crumbles in the stretched zone due to impact loads. Highway bridges under construction are designed to last 80 or even 100 years, and the ability of traditional structures to withstand this period under increased loads is increasingly being questioned. Wood, while providing biostability, copes well with shock loads. Great possibilities open up when combining materials. So, in wood-concrete structures concrete slab works in a compressed area, which has a positive effect on its durability. The steel elements in the bridges discussed above are of secondary importance and can be replaced if worn. And the main structure made of laminated wood is protected and works in optimal conditions. So wooden structures have a great future in bridge construction.

Artem LUKICHEV

The bridge, the spans of which are made of wood. Basic wooden bridge systems: beam, beam-braced, beam with lattice trusses, arched and combined. D. m. are widely used as temporary structures during the construction and restoration of railways and especially highways, as well as when constructing bypasses during the construction of a new bridge. Permanent wooden bridges are built on roads of categories III, IV and V, as well as in cities and other populated areas.

Construction of permanent D. m. on the railway. transport is allowed only for category III lines, and with the mandatory use of beam-overpass systems and structures, which can be replaced by permanent structures without interrupting train traffic and without constructing a bypass route.

The cost of building wooden bridges is usually lower than bridges made of other materials, but the maintenance costs are significantly higher, and the service life is shorter (from unprotected and unimpregnated wood does not exceed 5-10 years).

The simplest and most convenient to operate are beam systems of wooden bridges, used for spans of 2-3 m on railway. and 8-10 m on highways. IN standard projects girder road bridges with a cross lattice (so-called Gau farms), board-and-dowel and board-and-nail trusses.

To cover large spans, beam-braced systems are used: triangular-braced and double-braced, respectively, for spans of 6 and 9 liters in railways. and 12 and 18 m in road

bridges; trapezoidal-braced and transom-braced for spans up to 10-12 m and combined braced up to 18-20 m in road bridges. With a span length from 8 to 23 m in the railway. and 20-50 m in road bridges, spans with lattice trusses are used, of which the most common are belt trusses and braces made of sawn or round wood and vertical metal ones. strands They come with a top ride and a bottom ride. In the latter case, when covering large spans, the upper chord is given a polygonal outline.

The weak point in the design of trusses with a cross lattice is the joints of the lower chord, which are made using metal. overlays with dowels.

Plank trusses are a system with parallel chords and lattice filling. The boards of the belts cover on both sides the vertical wall (lattice) of the truss, consisting of two intersecting layers of boards, and are fastened with oak dowels passed through (in board-dowel trusses) or nails (in board-and-nail trusses). In board-and-nail trusses, the construction of a continuous wall is common. Plank trusses are simpler to manufacture compared to cross-lattice trusses and require less metal, but they are less durable due to accelerated rotting of the planks. Arched, top-mounted spacer systems have limited use on highways. For spans up to 25 m, arches are made of a solid section from boards or beams, for spans up to 60 m - through lattice or board and nails. Combined systems are also used on highways to cover large spans (up to 60 m). The most common are flexible plank or block arches of a solid section in combination with a beam in the form of a truss with a cross lattice or a plank truss connected to the arch with metal or wooden pendants. When constructing large wooden bridges, river spans are covered with trusses or arches, and for coastal spans, beam and beam-braced systems are used.

Railway bridge deck wooden bridges are built on wooden crossbars. When there is little traffic, the carriageway of road roads is made in the form of a roll-up of edged logs or plates laid along purlins. To improve traffic conditions on such roadway a layer of lightweight black covering or a single plank flooring is laid. Another type of roadway for wooden road bridges is a double plank deck (longitudinal, transverse or oblique) on wooden crossbars. On roads with heavy traffic, a deck made of boards laid on edge, covered with a layer of asphalt concrete, is sometimes used.

Wooden bridge supports usually wooden - piles, planks or cords. In some cases, when in the future it is planned to replace wooden spans with reinforced concrete ones, the supports are made of concrete or reinforced concrete. Protection of wooden supports from ice drift is provided by ice cutters, usually standing separately upstream at a distance of 1.5-4.0 m. In case of large ice drift, a second row of ice cutters, called ice cutters, is placed at a distance of 30-50 m from the first row. outpost.

The main types of wood used for the manufacture of concrete frames are: pine, larch, cedar, as well as spruce and fir (the use of the latter for railway bridges is allowed only in certain cases). Oak, ash, beech and hornbeam are used to make small parts of joints. Considering that the annual consumption of wood for the construction of new and major repairs of existing timber mills in the USSR exceeds 10 million JH5, a large national economy. What matters is max. extending their service life by preserving wood. Wooden bridges made from such wood last 15-20 years or more.

Permanent wooden bridges must meet the requirements of industrial construction and durability: their design must be quite simple, without notches and complex connections, allowing assembly from enlarged elements; During assembly, it is necessary to completely eliminate the fitting and pressing of elements manufactured in factories or construction yards. These conditions are best satisfied by a simple beam system with supports and spans made of sawn timber. Experimental work is being carried out on the use of laminated laminated elements (see Glued laminated structures) made from preserved boards, bakelized plywood or wood plastics, which are bioresistant and waterproof materials, in wooden bridges. For glued and glued plywood spans, the most rational are beam structures with a solid wall of I-beam or box section. It is also possible to use through structures. A number of roads and railways have been built and are being built in the USA and Canada. bridges with laminated beams, arches and truss belts, spans up to 45-50 m long. See also Bridge.

Lit.: Gibshman E.E., Wooden bridges on highways, M.-L., 1948; Evgrafov G.K., Bridges on railways, 3rd ed., M., 1955; Ivanova E.K., Glued wooden structures, M., 1961; Ten I. A. and Pospelov N. D., Introduce laminated wood structures, “ Car roads", 1961, No. 4.