The Annunciation Bridge spans the Bolshaya Neva River. It connects the Admiralteysky District with Vasilievsky Island. The axis of the bridge marks the watershed between the Gulf of Finland and the Bolshaya Neva. It is the first permanent crossing over the Neva River, both in terms of construction time and location.

The length of the crossing is 349.8 meters, and the width is 38.07 meters. The bridge has eight spans, with a draw span in the middle. The span structure is a metal double-leaf bascule system.

The weight of each leaf of the draw span is 597 tons. During the reconstruction of the Annunciation Bridge in 2005–2007, the leaves were supported on the ends of the trusses of the permanent spans. This unique solution allowed part of the weight to be removed from the draw span, eliminating the need to rebuild its supports. Also, for the first time in bridge construction history, counterweights were made using lead blocks.

The opening of the bridge is carried out using a state-of-the-art hydraulic system. The pavilions for the mechanics are located directly on the surface of the bridge.

The bridge is equipped with unique cast-iron railings designed by architect Alexander Brullov, the elder brother of artist Karl Brullov. The main motif of the design is hippocamps, mythological sea horses with fish tails.

Projects for permanent bridges over the Neva began to appear in St. Petersburg as early as the mid-18th century, but at that time their construction was too expensive and complicated. The Neva is a fairly deep river with a strong current. Moreover, ships with tall masts entered the Neva from the gulf, which meant that drawbridges were required.

As a result, St. Petersburg long relied on floating or pontoon bridges—temporary structures made from wooden barges and pontoons. By the mid-19th century, experience in building permanent metal bridges had accumulated both worldwide and in Russia. In 1842, Russian engineer Stanislav Kerbedz drafted a project for a crossing over the Bolshaya Neva to Vasilievsky Island. The project envisaged a structure with cast-iron arches at this location. On October 15 of the same year, the project was approved by Emperor Nicholas I. On January 1, 1843, the foundation of the new bridge was laid. All work was planned to be completed within four years. However, in practice, the period turned out to be twice as long.

For the first time in the history of Russian bridge construction, it was necessary to drive piles into the bottom of such a fast and full-flowing river during the construction of the Annunciation Bridge. Underwater work was carried out using air bells. The underwater part of the shore supports was laid out of Finnish granite, and the above-water part from Serdobol granite. They were embedded into the Neva riverbed to a depth of ten meters.

The bridge had eight spans, seven of which were permanent spans of different sizes covered by two-hinged cast-iron arches. The draw span was located on the right bank of the Neva, on the side of Vasilievsky Island. Using a mechanism, two leaves opened horizontally, parallel to the water surface. The opening took about 40 minutes. For the first time in the world, the bridge leaves were made in the form of diagonal trusses. All metal structures were manufactured in St. Petersburg at Charles Berd's factory.

During the construction of the bridge, the adjacent territory was reconstructed. On the left bank, Annunciation Square appeared. Part of the Kryukov Canal was piped. The embankment on the side of Vasilievsky Island was significantly widened.

The new bridge was named Annunciation after the Church of the Horse Guards Regiment and Annunciation Square. The opening took place on November 21, 1850. The emperor arrived at the ceremony with his family and entourage. Nicholas I walked on foot to Vasilievsky Island with his sons and returned in an open carriage with the heir. At that time, in the mid-19th century, the new Annunciation Bridge was the longest in Europe. Its length was about 300 meters.

The St. Petersburg newspaper "Northern Bee" commented on the construction of the Annunciation Bridge in September 1844: “The very construction of the bridge is a gigantic undertaking. Hardly in recent times have works been carried out on such a huge scale, with such amazing precision, elegance, taste, and from such precious material! Mountains of granite have been brought here from Finland and, like soft wax, obey the genius of man! Steam engines drive piles in the midst of the fast and deep Neva, while underwater strong stone foundations are being built on pile-reinforced soil.”

In 1854, a small chapel was built near the draw span, consecrated in the name of Saint Nicholas the Wonderworker. After the emperor’s death in 1855, the bridge was renamed Nikolaevsky. In 1918, the bridge was given a new name in honor of Lieutenant Pyotr Schmidt, who led the uprising on the cruiser "Ochakov" during the first Russian revolution.

Already in the 19th century, the draw span of the bridge became too narrow for large ocean-going vessels. At the beginning of the 20th century, engineers developed several reconstruction projects. It was proposed to move the draw span to the center of the bridge. However, the implementation of this idea was hindered by World War I and the revolution.

In 1936–1938, the bridge was rebuilt. The project was developed by engineer Grigory Perederiy. The number of spans remained the same—eight—but the middle span became the draw span. The welded metal span structure is a double-leaf bascule system with rigidly attached counterweights and a fixed axis of rotation. The old draw span was covered with a reinforced concrete span structure of a two-hinged arch system. The bridge was opened using an electromechanical drive.

The Lieutenant Schmidt Bridge is one of the first welded bridges in our country. During its construction, an advanced method at the time—electric welding—was used. Underwater concreting technology was applied during the reconstruction, as well as a new method of testing span structures with water static load.

The new mechanisms were made at the Kirov Plant in Leningrad. The cast-iron structures of the old bridge were transported to Tver and used for the construction of a crossing over the Volga. The lanterns from the old bridge were installed on Mars Field. The chapel was not restored. From the old structure, wooden piles and cast railings remain.

In 1975–1976, a major repair was carried out according to a project by engineers from Lengiproinzhproekt. The wooden decking of the draw span was replaced with metal.

In 2004, the question of reconstructing the Lieutenant Schmidt Bridge arose. It was decided to bring the architectural appearance of the new bridge as close as possible to the look it had in the 19th century. Work began in September 2005.

The reconstruction took place in 2005–2007. The old foundations of the supports remained in working condition after one and a half centuries, but the steel structures had to be completely replaced. The draw span was significantly enlarged. The bridge became much wider, and the tram tracks were removed. The hydraulic opening system made the lifting of the bridge leaves fast and smooth.

On August 15, 2007, the crossing was solemnly reopened and its historical name—Annunciation Bridge—was restored.

In 1917, the cruiser "Aurora" was moored behind the Nikolaevsky Bridge. It was from there that the blank shot was fired, which became the signal for the storming of the Winter Palace.

During the major repair of 2005–2007, a duplicate bridge was built upstream on the Neva for automobile and pedestrian traffic between the Central District and Vasilievsky Island, which became popularly known as the "Son of Lieutenant Schmidt."

Sources:

https://mostotrest-spb.ru/bridges/blagoveshhenskij

https://kuda-spb.ru/place/blagoveschenskij-most/

https://ru.wikipedia.org/wiki/Annunciation_Bridge