Project of the Year
Submitted by: Çanakkale Motorway and Bridge Construction Investment and Operation Inc
Owner: Ministry of Transport and Infrastructure of Türkiye, General Directorate of Highways
Lead Design Firm; Civil, Structural & MEP Engineer: COWI A/S
General Contractor: DLSY JV (DL E&C, Limak, SK Ecoplant and Yapi Merkezi)
Consultants: Mott MacDonald; Arup
The 1915Çanakkale Bridge is not only the world’s longest suspension bridge, with a main span of 2,023 m, but a historic and economic new landmark for Turkey. Built in just four years, the new link between Asia and Europe will decrease the crossing time across the Çanakkale Strait to just six minutes, from up to six hours.
Project participants from around the world helped the Turkish-Korean contracting team—Limak and Yapı Merkezi from Turkey, and DL E&C and SK Ecoplant from Korea—build the bridge in just four years, 18 months early (ENR 9-27/10-4/21, p. 18).
“The four partners who built this engineering marvel did not divide the work between themselves,” says Yapi Merkezi chairman Başar Arıoğlu. “We formed an integrated organization with our partners. Each company put forward their best people with the best know-how. If the best people were outside of the organization, we recruited them. We worked with experts from 19 different countries such as Japan, Germany, Australia, the U.K. and the Netherlands.”
The red-and-white colors of the bridge towers reflect Turkey’s flag.
Photo courtesy of DLSY JV
The Australian firm Marr Contracting Pty Ltd., aka “The Men from Marr’s,” used 330-ton capacity cranes to accomplish world-record feats: A 2,000-tonne capacity floating barge crane transported and lifted the 600-tonne assembled M2480D crane from the drydock to the site 1 km away, and lifted a 155-tonne tower block segment into place 318 high in about 30 minutes.
Those towers symbolize Turkey’s victory on March 18, 1915 in the battle of Gallipoli during World War I. The two red-and-white towers—reflecting Turkey’s flag—with ornamental corbels have a total height of 334 m, the tallest in the world for suspension bridges. The length of the main span symbolizes the 100th anniversary of the Republic of Turkey this year.
“It is the first bridge spanning over 2 km as a twin box steel girder with a 9-m gap,” Ömer Güzel, deputy general manager with Yapi Merkezi, wrote in a technical paper. “The arrangement of the deck is finalized with the analysis and wind tunnel tests done for satisfying the critical wind speeds and improving traffic comfort with wind barriers. The material of the towers is selected as steel to reduce the construction time by the utilization of prefabrication techniques as well as to reduce the seismic mass of the towers. The main cables consist of prefabricated parallel wire strands which provided fast erection.”
The General Directorate of Highways (KGM) awarded $2.5 billion to the 1915Çanakkale Bridge and Highway Project as a public-private partnership model to the consortium, which subsequently established a joint-venture company, Çanakkale Motorway and Bridge Construction Investment Management Inc. In 2018, finance agreements were signed with 25 financial institutions from 10 countries. They included a 15-year-term loan with a grace period of 5 years.
The record length of 2,023 m for the bridge main span also echoes the year 2023, the 100-year anniversary of the Turkish Republic; the crossing over the Dardanelles Strait is a new link between Asia and Europe.
Photo above courtesy Cemal Emden; photos below courtesy of DLSY JV
More than 1,300 subcontractors, suppliers and consultants from 19 countries helped build the bridge. Denmark-based COWI A/S was tasked with meeting the specific design requirements and preparing detailed design in a year. “The bridge situation in a seismically active region further affected significant parts of the substructure design,” noted COWI engineers in a technical paper. “Seismic hazard and difficult geological site conditions impose tremendous challenges to the bridge design.”
traffic, strong wind conditions, and unique live loads required innovative approaches to seismic and aerodynamic designs, vessel collision risk analysis and live load modeling. Comprehensive wind data collection and wind tunnel tests were performed in Canada, Denmark and China to confirm the bridge’s aerodynamic stability. The team chose an immersed caisson foundation system, including open-ended steel inclusion piles, to increase soil strength, topped by caissons to allow simultaneous pile installation and pouring. The inclusion piles reduced tower settlement and increase lateral resistance.
The seabed consists of Holocene clay deposits at the European tower and Pleistocene clay and sand deposits at the Asian tower, followed by a Miocene mudstone formation below at both locations, according to COWI. Crews dredged the seabed to level it out for the 2.5-m-dia inclusion piles to be driven into the mudstone. A total of 203 piles were installed at the European tower location with lengths up to 46 m and 165 piles at the Asian tower location with lengths of 21 m.
Plinth rebar-cage and tie-beam concrete installations were initially intended to be cast in place. Considering adverse weather conditions and pandemic-related workspace limitations, the decision shifted to prefabricating them. Crews used a floating crane and barge to lift and position them. To mitigate wind-induced bending action and minimize strain on temporary connections, the team designed an X-bracing release joint. This device preserved segment spacing longitudinally and transversely.
The two stiffened box girders comprising the deck represent recent evolutions in long-span bridge technology.
Photos by Resit Yildiz
Next-Gen Bridge Technology
The two stiffened closed steel box girders, connected by 3-m-wide cross-girders every 24 m, have overall widths of 45 m, with one maintenance walkway on each side and depths of 3.5 m. Project officials say they reflect the advances in long-span bridge technology.
“Laboratory studies in recent years and construction of bridges with spans longer than 1,500 m have proven that deck designs using multiple boxes showed sufficient resistance against wind loads within economic limitations. Following this discovery, the burning question was transformed into: ‘when and where will the 2,000-m-long span limit be overcome?’” said Ersin Arıoğlu, founder of Yapi Merkezi, in a keynote speech last year at a bridge conference.
Guzel noted in his paper: “The span length of suspension bridges, which is the fastest developing attribute of the bridge, has increased by nearly 10 times in the past 150 years. It is highly probable that over 3,000-m main span suspension bridges may be constructed in the next two decades”.
In another interview given before his passing this past spring, Arıoğlu stated: “The 1915Çanakkale Bridge, with all its aesthetic signs and messages and its notable suspension bridge technologies, is dedicated to crown the successes of the 100-year-old Republic of Turkey, to the memory of martyrs, to the development of prosperity, civilization and peace.”