15 July Martyrs Bridge, formerly the Bosphorus Bridge or the First Bridge, with reference to being the first bridge built on the strait; It is one of the three suspension bridges located on the Bosphorus, which connects the Black Sea and the Marmara Sea. The feet of the bridge are in Ortaköy on the European Side and Beylerbeyi on the Anatolian Side.
The Bosphorus Bridge, also known as the First Bridge, as the first bridge built on the Bosphorus, provides land transportation between the two sides of the city, together with the Fatih Sultan Mehmet Bridge and Yavuz Sultan Selim Bridge. Bridge construction started on February 20, 1970, on October 30, 1973 of the Republic of Turkey in honor of the 50th anniversary of the state ceremony was opened by President Fahri Koruturk. While it was the fourth longest suspension bridge in the world when its construction was completed, it ranked twenty-first as of 2012.
The official name of the bridge on July 26, 2016, Turkey 2016, as amended July 15 to commemorate the Martyrs Bridge on the bridge of the citizens who lost their lives during the military coup.
Connecting the two shores of the Bosphorus with a bridge has been a thought that has been emphasized since ancient times. According to the information that is somewhat confused with the legend, the first to build such a bridge was Persian King Darius I, who ruled between 522-486 BC. In his campaign against the Scythians, Darius led his troops from Asia to Europe over the bridge that architect Mandrokles built by linking ships and rafts side by side.
After that, it was only in the 16th century to build a bridge over the Bosphorus. Famous artist and engineer Leonardo da Vinci, the Ottoman sultan of the period in 1503. By applying to Bayezid with a letter, he proposed to build a bridge over the Golden Horn, and to extend this bridge (over the Bosphorus) to Anatolia if desired.
In 1900, a French named Arnaudin prepared a Bosphorus bridge project. This bridge project, which is considered to pass the railway and has two separate locations, one between Sarayburnu-Üsküdar and one between Rumeli Fortress and Kandilli, was not approved.
In the same year, a company called Bosphorus Railroad Company applied to build a bridge between the fortresses on the Bosphorus. According to the project submitted with the application, the span to be crossed by the bridge was divided into four by three large masonry legs, and the bridge consisting of an "overhead iron mesh suspended with steel wires" was carried to these legs. An ornamental element, consisting of a dome surrounded by four minarets, was placed on each of the legs, and in the essay it was said that these elements were shaped by Northwest African architecture. The name "Hamidiye" was deemed appropriate for the bridge "which will take a magnificent view", but the sultan of the period II. Abdulhamid did not accept this project.
The next attempt came from Nuri Demirağ, a construction contractor and businessman during the Republican era. Demirağ, who signed an agreement with an American company called Bethlehem Steel Company in 1931, prepared a bridge project to be built between Ahırkapı and Salacak, based on the Oakland Bay suspension bridge in San Francisco and presented it to Atatürk. With a total length of 2.560 m, 960 m of this bridge would pass over land and 1.600 m over the sea. This second section would sit on 16 feet at sea, with a 701 m long suspension bridge in the middle. It would have a width of 20,73 m and an altitude of 53,34 m. It was also envisaged that tram and bus routes other than railways would cross the bridge. This project, which Demirağ tried to get accepted until 1950, did not come true either.
Germans also took care of the Bosphorus bridge. The Krupp firm was founded by German architect Professor, who worked as a faculty member at ITU Faculty of Architecture between 1946-1954. He suggested that Paul Bonatz conduct a study and research on such a bridge in 1951. The most suitable place was determined between Ortaköy and Beylerbeyi by Bonatz's assistants and Krupp prepared a project proposal accordingly. But this attempt did not come to a conclusion either.
In 1953, at the request of the Democrat Party government, a committee consisting of the representatives of Istanbul Municipality, General Directorate of Highways and ITU was established to examine the issue of the Bosphorus bridge. This committee concluded that the issue should be examined well due to its importance and decided to have the investigation done by a specialist firm. In 1955, the General Directorate of Highways gave the study to the US firm De Leuw, Cather and Company. An international announcement was requested in 1958 for the preparation of a suspension bridge project between Ortaköy and Beylerbeyi, the location of the company, and for the control services. A project was prepared by Steinman, Boynton, Granquist and London companies selected among the applications. However, financial and managerial difficulties that arose afterwards prevented the implementation of this project.
In the same year, the Germans also made an attack for the Bosphorus Bridge. Dyckerhof und Widmann firm applied to the government with a project proposal prepared by Gerd Lohmer, an architect with expertise in bridges. According to this proposal, the deck of the bridge consisted of only 60 cm thick tape, which was made of prestressed concrete. In other words, the bridge was not a suspension, but a tension bridge. Its deck was sitting on two legs in the sea. The distance between the piers 300 meters off the land was 600 meters. Each pillar consisted of two 150 m long consoles, which opened like a fan to both sides. Like the bridge, the piers were only 60 m high; Therefore, it was argued that a suspension bridge crossing the same span would not spoil the skyline of the Bosphorus, like the towers that would have to be about three times higher. The proposal was turned down when a board of experts in urban planning, architecture and aesthetics decided that a suspension bridge would look better on the Bosphorus.
The project, which was prepared by Steinman, Boynton, Granquist and London, was incomplete and inadequate due to the change and advancement of technology in the meantime. In 1967, four foreign engineering firms specializing in the subject were asked to prepare a new project and an agreement was signed in 1968 with the British firm Freeman, Fox and Partners, who made the most appropriate proposal. A consortium of German companies named Hochtief AG and British companies named Cleveland Bridge and Engineering Company won the tender to select the company to carry out the construction.
Construction of the bridge started on February 20, 1970. In March 1970, the excavation of the Ortaköy feet and just after the excavation of the Beylerbeyi feet began. The tower assembly was started on August 4, 1971. The first joint was achieved by pulling the guidewire in January 1972. The tension and twisting processes of the wires started on June 10, 1972 and continued until the opening of the bridge. In December 1972, the first deck was started to be mounted on the steel ropes stretched to the bridge with a swing system. The hollow decks were connected to the suspension ropes by means of hoists and hoists at the top of the towers. The lifting of the decks was started from the middle of the bridge, respectively, towards both ends in equal numbers. The assembly of the last deck was completed on March 26, 1973. Then 60 decks were welded together. Thus, it was the first time that it was passed from Asia to Europe on foot. In April 1973, double layer asphalt casting with a rubber alloy started, and on June 1, 1973 the asphalt casting process was completed. The construction of the approach viaducts (passing through Ortaköy and Beylerbeyi) was completed in May 1973. On June 8, 1973, the first vehicle transit test was conducted.
It was put into service by President Fahri Korutürk on 30 October 1973, on the 50th anniversary of the proclamation of the Republic. The cost of the bridge, whose construction was completed in three years, is USD 21.774.283 according to the agreement. When it was built, when the USA was excluded from the evaluation, it was the longest suspension bridge in the world.
The 15 July Martyrs Bridge consists of a transport tower on each side of the Bosphorus and a deck suspended from two main cables between them. Each carrier tower has two box-section vertical pillars and these are connected to each other at three points by three box-section horizontal beams. The deck sits on the lowest one of these beams at both ends. There are passenger and service elevators inside the towers, 165 m high, made of soft and high-strength steel. Passenger elevators are for ten people each and service elevators carrying maintenance personnel are for eight people each.
The 33,40 m wide deck consists of 60 stiffened hollow plate panel units. These units, which are connected to each other by welding, are 3 m high and 28 m wide. There are 2,70 m wide consoles on both sides. There are six tracks, three departures and three arrivals, on the deck, whose midpoint is 64 m above sea level, and pedestrian paths are located on the consoles on the sides.
With a total length of 1.560 m and a middle span of 1.074 m between the two towers, the suspension cables connecting the nature of the bridge to the main cables are arranged inclined rather than straight. However, when the cracks caused by metal fatigue were detected in the oblique suspension cables of the Severn Bridge in England, which was similar to this bridge, the diameter of the carrying main cables of the Fatih Sultan Mehmet Bridge, which was built later on the Bosphorus, was 58 cm in the middle span, and the towers were is 60 cm in the back tensioners between. The ends of these cables are concreted to the rock ground with anchor blocks.
D 100 Bosphorus Bridge that crosses over the highway, the fixed link between Europe and Asia is very important for both Turkey and the Istanbul public transportation network. Since its opening, the traffic increase has been much higher than expected; In the year the bridge was first put into service, the average daily vehicle passage was 32 thousand, while this number increased to 1987 thousand in 130 and 2004 thousand in 180.
In 1991, heavy tonnage (4 tons and over) vehicles, excluding buses, were banned from crossing the bridge. Today, only municipal buses, public buses and buses with a tourist transport license, cars and motorcycles are allowed to cross the Bosphorus Bridge.
The Bosphorus Bridge has been closed to pedestrian traffic since 1978.
The lighting and lighting system of the Bosphorus Bridge was activated with a ceremony and light show held on April 22, 2007. The color-changing led luminaires used in the bridge are known to be long-lasting, low energy consumption and environmentally friendly. The entire bridge was illuminated with 16 million color LED luminaires that can be changed. During the installation of the equipment, 236 LED light modules and over 2000 meters of cable were fixed on 7000 V-suspension ropes. During this study, 12 rope access technicians made vertical rope descent over 9000 meters. This installation was the largest rope access project was carried out until 2007 in Turkey.