The Bosphorus Bridge known officially as the 15 July Martyrs Bridge and unofficially as the First Bridge is one of the three suspension bridges spanning the Bosphorus strait (Turkish: Boğaziçi) in Istanbul, Turkey, thus connecting Europe and Asia (alongside Fatih Sultan Mehmet Bridge and Yavuz Sultan Selim Bridge). The bridge extends between Ortaköy (in Europe) and Beylerbeyi (in Asia).
It is a gravity-anchored suspension bridge with steeltowers and inclined hangers. The aerodynamicdeck hangs on steel cables. It is 1,560 m (5,118 ft)long with a deck width of 33.40 m (110 ft). The distance between the towers (main span) is 1,074 m (3,524 ft) and the total height of the towers is 165 m (541 ft). The clearance of the bridge from sea level is 64 m (210 ft).
Upon its completion in 1973, the Bosphorus Bridge had the fourth-longest suspension bridge span in the world, and the longest outside the United States (only the Verrazano-Narrows Bridge, Golden Gate Bridgeand Mackinac Bridge had a longer span in 1973).The Bosphorus Bridge remained the longest suspension bridge in Europe until the completion of the Humber Bridge in 1981, and the longest suspension bridge in Asia until the completion of the Fatih Sultan Mehmet Bridge (Second Bosphorus Bridge) in 1988 (which was surpassed by the Minami Bisan-Seto Bridge in 1989). Currently, the Bosphorus Bridge has the 33rd-longest suspension bridge spanin the world.
After a group of soldiers took control and partially closed off the bridge during the military coup d’état attempt on 15 July 2016, Prime Minister Binali Yıldırım announced on 25 July 2016 the decision of the Cabinet of Turkey that the bridge will be formally renamed as the 15 Temmuz Şehitler Köprüsü (July 15th Martyrs Bridge) in memory of those killed while resisting the attempted coup.
The idea of a bridge crossing the Bosphorus dates back to antiquity. For Emperor Darius the Great of the Achaemenid Empire (522 BC–485 BC), as recorded by the Greek writer Herodotus in his Histories, Mandrocles of Samos once engineered a pontoon bridge across the Bosphorus, linking Asia to Europe, enabling Darius to pursue the fleeing Scythians as well as position his army in the Balkans to overwhelm Macedon. Leonardo da Vinci proposed a parabolic arch bridge to Sultan Bayezid II in 1502 or 1503.The first modern project for a permanent bridge across the Bosphorus was proposed to Sultan Abdul Hamid II of the Ottoman Empire by the Bosphorus Railroad Company in 1900, which included a rail link between the continents.
The decision to build a bridge across the Bosphorus was taken in 1957 by Prime Minister Adnan Menderes. For the structural engineering work, a contract was signed with the British firm Freeman Fox & Partners in 1968. The bridge was designed by the British civil engineers Gilbert Roberts, William Brown and Michael Parsons, who also designed the Humber Bridge, Severn Bridge, and Forth Road Bridge. Construction started in February 1970 and ceremonies were attended by President Cevdet Sunay and Prime Minister Süleyman Demirel. The bridge was built by the Turkish firm Enka Construction & Industry Co. along with the co-contractors Cleveland Bridge & Engineering Company(England) and Hochtief AG (Germany). Thirty-five engineers and 400 men worked on the project.
The bridge was completed on 30 October 1973, one day after the 50th anniversary of the founding of the Republic of Turkey, and opened by President Fahri Korutürk and Prime Minister Naim Talu. The cost of the bridge was US$200 million ($1.13 billion in 2018 dollars).
Upon the bridge’s opening, much was made of its being the first bridge between Europe and Asia since the pontoon bridge of Xerxes in 480 BCE. That bridge, however, spanned the Hellespont (Dardanelles), some distance away from the Bosphorus, and was the second bridge after the above-mentioned bridge built by Emperor Darius I The Great across the Bosphorus in 513 BCE.
The bridge highway is eight lanes wide. Three standard lanes, one emergency lane and one pedestrian lane serve each direction. On weekday mornings, most commuter traffic flows westbound to Europe, so four of the six lanes run westbound and only two eastbound. Conversely, on weekday evenings, four lanes are dedicated to eastbound traffic and two lanes, to westbound traffic.
For the first three years, pedestrians could walk over the bridge, reaching it with elevators inside the towers on both sides. No pedestrians or commercial vehicles, such as trucks, are allowed to use the bridge today.
Today, around 180,000 vehicles pass daily in both directions, with almost 85% being cars. On 29 December 1997, the one-billionth vehicle passed the bridge. Fully loaded, the bridge sags about 90 cm (35 in) in the middle of the span.