The Osmangazi Bridge is a suspension bridge located in northwestern Türkiye, constructed between Gebze and Altınova at the eastern end of the Sea of Marmara to facilitate road transportation between Istanbul and Izmir. As the main structure of the Gulf Crossing Project, the bridge is part of the Istanbul-Izmir Motorway and has reduced the sea crossing time to approximately 6 minutes.
The total length of the Osmangazi Bridge is 2,682 meters, with a main span of 1,550 meters. As of its completion in 2016, this made it the seventh-longest suspension bridge in the world by main span length. The deck of the bridge is 35.93 meters wide and serves two-way traffic with six lanes. The deck height above sea level is 64 meters, allowing uninterrupted maritime navigation beneath the bridge.
Osmangazi Bridge (AA)
Structural System and Engineering Features
The towers of the bridge are 252 meters high and are anchored on pile foundations fixed to the seabed. The bridge is supported by a cable system, and the deck was lifted segment by segment and mounted onto the cables. Its wind resistance has been tested up to speeds of 216 km/h. Equipped with advanced monitoring and maintenance systems, the structure is constantly supervised. Given that it is located in a seismically active region, special engineering measures have been implemented.
Construction Process and Financing Model
The bridge was constructed under the Build-Operate-Transfer (BOT) model. The project was carried out without the use of public funds; the contractor committed to building and operating the bridge for a certain period before transferring it to the public sector. Construction began in 2013, and the bridge was officially opened by the Presidency on June 30, 2016. Engineers from Japan, South Korea, Italy, and Turkey took part in the construction of the Osmangazi Bridge. The design considered earthquake resistance, wind loads, and maritime traffic. The project incorporated seismic isolators, rigid structural elements, and advanced steel cable systems.
With the completion of the bridge, heavy vehicle traffic was diverted away from city centers around the Gulf, increasing the efficiency of logistics networks. According to official sources, the bridge contributed approximately 650 million USD indirectly to the Turkish economy within the first five years following its opening.
Transportation and Time Savings
The reduction in travel time between Istanbul and Izmir has provided a significant advantage for both trade and tourism, particularly strengthening the logistical connections of industrial cities such as Bursa, Balıkesir, and Manisa.
Osmangazi Bridge (AA)
Environmental Impact
Environmental Impact Assessment (EIA) studies were conducted for the project, with particular attention given to the marine ecosystem, water currents, and bird migration routes. Noise insulation measures were implemented for pile-driving machinery operating in the sea, and interventions to coastal ecosystems were kept to a minimum.
Sustainability and Maintenance System
The Osmangazi Bridge is equipped with a continuous Structural Health Monitoring System. Parameters such as wind, seismic activity, temperature, humidity, and traffic load are monitored in real time. This system is designed to ensure the safety and performance of the structure throughout its lifespan. Additionally, annual maintenance activities are carried out, including painting and tension checks of the cables.
